JPH10287251A - Industrial vehicle steering angle correction device and industrial vehicle - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To enable the operation of a steering wheel without a sense of incongruity at the time of high-speed traveling, and to avoid stopping the steering angle correction. SOLUTION: The actual position of a steering wheel is detected by a rotary encoder, and the turning angle of a steered wheel is detected by a potentiometer. The CPU calculates a target position according to the steering angle of the steered wheels. When the deviation amount Δθ between the actual position of the steering wheel and the target position exceeds the allowable value, the duty valve is driven, the change ratio of the driving amount of the steering cylinder to the operation amount of the steering wheel decreases, the steering wheel idles, and the deviation amount Δθ The position of the steering wheel is corrected until at least falls within the allowable range. Further, the duty value of the duty valve is set according to the vehicle speed v detected by the vehicle speed detecting means. Then, the duty valve is controlled so that the correction amount per unit time decreases in accordance with the increase in the vehicle speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an industrial vehicle such as a forklift equipped with a power steering device.
TECHNICAL FIELD The present invention relates to a steering wheel angle correction device for correcting a deviation in a positional relationship between a steering wheel angle and a steering wheel turning angle, and an industrial vehicle.

[0002]

2. Description of the Related Art Conventionally, as a power steering device,
2. Description of the Related Art An all-hydraulic power steering device that supplies steering oil to a steering cylinder in an amount corresponding to an operation amount of a steering wheel to steer a steered wheel is known.

For example, in an industrial vehicle such as a forklift,
A knob is provided on the handle so that the handle can be operated with one hand while performing a cargo handling operation or the like. For this reason, the position of the knob may be used as a guide for determining whether or not the turning angle of the steered wheels is in the straight traveling posture. However, not all hydraulic oil discharged in accordance with the operation amount of the steering wheel is necessarily used for driving the steering cylinder. When the orbit roll efficiency (actual discharge amount / theoretical discharge amount) decreases, the position of the knob and the A deviation occurs in the positional relationship with the steering angle of the steered wheels. The decrease in the orbit roll efficiency is caused when the steering wheel is operated at a low speed or due to an oil leak in a hydraulic system such as a steering cylinder.

[0004] For example, Japanese Patent Publication No. 3-30544 and Japanese Patent Publication No. 4-24270 disclose a steering wheel angle correcting device for correcting a deviation of a steering wheel angle with respect to a turning angle of a steering wheel. FIG. 16 shows a steering wheel angle correcting device disclosed in Japanese Patent Publication No. 4-24270.

[0005] All hydraulic power steering device 51
Are a steering unit 53 operated by a handle 52, a steering cylinder 54 for steering a steered wheel (not shown), and hydraulic lines 55 and 56 connecting the steering unit 53 and the steering cylinder 54.
And One of the hydraulic lines 55 and 56 is a feed line for supplying pressurized hydraulic oil from a steering hydraulic pump 57 during steering according to the steering direction of the steering wheel 52, and the other line is to a hydraulic oil tank 58. A return line for returning oil. An electromagnetic switching valve 60 is provided in the drain oil line 59 connecting the two hydraulic lines 55 and 56.

The control means 61 receives a handlebar rotation angle signal θabs from a handlebar rotation angle sensor 62 and a cylinder stroke signal s from a cylinder position sensor 63. The control means 61 obtains a target cylinder stroke xg from the handlebar rotation angle signal θabs using a map, and when the deviation between the cylinder stroke x obtained from the cylinder stroke signal s and the target cylinder stroke xg exceeds an allowable value, the solenoid 64 is activated. Energized to switch solenoid valve 60
Was opened.

When the electromagnetic switching valve 60 is opened,
A part of the hydraulic oil flows from one supply line of the hydraulic lines 55 and 56 to the other return line and flows out (recirculates) to the hydraulic oil tank 58 through the drain oil line 59, and the handle position corresponds to the tire turning angle. Until the normal position is corrected within the allowable value, the steering wheel 52 is in the idling state, and the steering wheel position is corrected.

[0008]

The correction of the steering wheel angle causes the steering wheel to idle even though the operator is operating the steering wheel. Therefore, if the correction operation is performed while the vehicle is running, when the operator turns the steering wheel with the intention of changing the course (turning or curve running), the rate of increase in the steering angle becomes smaller than the rate intended by the operator. The feeling of discomfort arises. There is a problem that even when there is a sense of discomfort during low-speed running, the vehicle does not feel much discomfort because the distance traveled by the vehicle is short, but during high-speed traveling, the discomfort becomes large because the distance that the vehicle moves during that time is long.

In order to eliminate the discomfort, it is conceivable to stop the correction operation during high-speed running. However, when the correction operation is stopped, there arises a problem that a knob shift occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an industrial vehicle capable of operating a steering wheel at a high speed without a sense of discomfort and not having to stop the steering wheel angle correction. And an industrial vehicle.

[0011]

According to the first aspect of the present invention, there is provided an all-hydraulic power steering apparatus, and a predetermined amount of positional relationship between a steering wheel angle and a steering wheel turning angle is provided. When the above deviation occurs, in an industrial vehicle provided with a steering angle correction means for correcting the deviation by rotating the steering wheel at the time of operating the steering wheel, the correction amount per unit time by the steering angle correction means is calculated at a high speed. At times, I made it less than at low speed.

According to the second aspect of the present invention, a driving means for driving the steered wheels to a steering angle corresponding to the operating position of the steering wheel, a steering wheel angle detecting means for detecting the actual position of the steering wheel, Steering angle detecting means for detecting a turning angle, target position calculating means for obtaining a target position from the turning angle, correcting means for reducing a change ratio of a driving amount of the driving means to an operation amount of the steering wheel, and detecting a vehicle speed Vehicle speed detecting means, and driving control of the correcting means so that a deviation amount between the actual position of the steering wheel and the target position is at least within an allowable range, and a unit time of the correcting means corresponding to an increase in vehicle speed. Control means for controlling so as to reduce the hit correction amount.

According to a third aspect of the present invention, in the second aspect of the present invention, the driving unit includes a hydraulic oil supply unit that discharges hydraulic oil having an oil amount corresponding to an operation amount of the handle, A hydraulic actuator that is driven by hydraulic oil from oil supply means and drives the steered wheels.The correction means reduces a part of the hydraulic oil discharged from the hydraulic oil supply means to the steering oil. A duty control valve is provided in a pipe that can return to the drain tank before being supplied to the actuator, and the control unit changes the duty of the duty control valve in accordance with the vehicle speed.

According to a fourth aspect of the present invention, in the third aspect of the invention, an on / off solenoid valve is used in place of the duty valve, and the control means controls the on / off solenoid in accordance with the vehicle speed. The time for keeping the valve open was changed.

According to a fifth aspect of the present invention, in the third aspect of the invention, a proportional valve is used in place of the duty valve, and the control means changes the opening of the proportional valve in accordance with the vehicle speed. I did it.

According to a sixth aspect of the present invention, in the third aspect of the present invention, a variable throttle valve and an electromagnetic switching valve are provided in the conduit in place of the duty valve, and the control means is adapted to correspond to a vehicle speed. The opening degree of the variable throttle valve is changed.

In the invention described in claim 7, in the invention described in any one of claims 2 to 6, the control means determines the target based on the steering angle detected by the steering angle detection means. Target position calculating means for calculating the position by the relative angle of the handle, so that the deviation between the actual position and the target position detected by the handle angle detecting means at the relative angle of the handle falls within a permissible value in the relative angle. The position of the handle is corrected.

An industrial vehicle according to an eighth aspect of the present invention includes the steering wheel angle correcting device according to any one of the first to seventh aspects. According to the first aspect of the present invention, when the positional relationship between the steering wheel angle and the steering angle of the steered wheels is deviated by a predetermined amount or more, the steering wheel angle correcting means is operated, and the steering wheel idles when the steering wheel is operated. Then, the deviation is corrected. Then, the correction amount per unit time by the steering wheel angle correction means is smaller at high speed running than at low speed running.

According to the second aspect of the present invention, the steered wheels are steered by the driving means at a turning angle corresponding to the operation of the steering wheel. The actual position of the steering wheel is detected by the steering wheel angle detecting means, and the steering angle of the steered wheels is detected by the steering angle detecting means. The target position, which is the normal position of the steering wheel,
It is determined from the angle by the target position calculating means. Then, when the amount of deviation between the actual position of the steering wheel and the target position corresponding to the steering angle of the steered wheel exceeds an allowable value, the control means drives and controls the correction means. As a result, the rate of change of the driving amount of the driving means with respect to the operation amount of the steering wheel decreases, and the steering wheel idles, and the position of the steering wheel is corrected until at least the deviation amount falls within the allowable range.
The vehicle speed is detected by the vehicle speed detecting means. And
The control means controls the correction means so that the correction amount per unit time of the correction means decreases in accordance with the increase in the vehicle speed. Therefore, if the steering wheel angle correction amount per unit time is large at the time of operating the steering wheel, an uncomfortable feeling is likely to occur.

According to a third aspect of the present invention, in the second aspect of the present invention, the hydraulic oil having an amount corresponding to the operation amount of the handle is discharged from the hydraulic oil supply means constituting the driving means, A hydraulic actuator for driving the steered wheels is driven by the hydraulic oil. The correction means reduces a change rate of the drive amount of the actuator by returning a part of the hydraulic oil discharged from the hydraulic oil supply means to the drain tank before being supplied to the actuator. Before a part of the hydraulic oil is supplied to the actuator, a duty control valve provided in a conduit that can return to the drain tank is controlled by a control unit. The duty is controlled to decrease as the vehicle speed increases.

According to a fourth aspect of the present invention, in the third aspect of the invention, an on / off solenoid valve is used in place of the duty valve. Then, as the vehicle speed increases, the open / close solenoid valve is controlled so that the time of the open state per operation becomes shorter.

According to a fifth aspect of the present invention, in the third aspect of the invention, a proportional valve is used instead of the duty valve. The control is performed so that the opening of the proportional valve decreases as the vehicle speed increases.

According to a sixth aspect of the present invention, in the third aspect of the invention, a variable throttle valve and an electromagnetic switching valve are provided in the pipeline in place of the duty valve. When performing the steering wheel angle correction, the electromagnetic switching valve is held in the open state. Then, the opening degree of the variable throttle valve is controlled to decrease as the vehicle speed increases.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the actual position of the handle is detected by the handle angle detecting means based on the relative angle of the handle. The target position used for the correction is determined from the steering wheel turning angle by the relative angle of the steering wheel by the target position calculating means. The steering wheel position correction is performed such that the deviation amount falls within an allowable value in a relative angle. Since the position correction of the steering wheel is performed based on the deviation amount in the relative angle, even when the steering wheel is deviated by 360 degrees or more with respect to the steered wheels, the correction amount is smaller by one rotation or two rotations and less than 360 degrees.

According to the invention described in claim 8, the industrial vehicle is provided with the steering wheel angle correction device according to any one of claims 1 to 7, so that the industrial vehicle has the following features. The same operation as the invention described in any one of claims 1 to 7 is obtained.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a schematic diagram showing the power steering device 1 mounted on a forklift F as an industrial vehicle. A steering wheel (steering wheel) 2 that is rotated by an operator is provided with a knob 2a for improving the operability. The steering shaft 3 supporting the handle 2 is connected to the orbit roll 4.

A valve unit 5 constituting the orbit roll 4 has a supply pipe 7 through which hydraulic oil is supplied from a hydraulic pump (loading pump) 6 driven by an engine (not shown), and a drain tank 8. A discharge pipe 9 for discharging oil is connected. A relief valve 11 is interposed in a conduit 10 connecting the supply pipe 7 and the discharge pipe 9, and the relief valve 11 keeps a hydraulic pressure fed from the hydraulic pump 6 to the valve unit 5 at a constant pressure (set pressure). It has become so.

The valve unit 5 is driven directly by the steering shaft 3 and has a function of supplying a hydraulic oil having an oil amount proportional to the rotation amount of the handle 2 to a steering cylinder 12 as a hydraulic actuator. Things. The valve unit 5 and the steering cylinder 12 are connected by two hydraulic lines 13 and 14. When the handle 2 is turned right, the hydraulic line 13
Functions as a supply line for supplying hydraulic oil from the hydraulic pump 6, and the hydraulic line 14 functions as a return line for returning hydraulic oil to the hydraulic pump 6. When the handlebar 2 is turned to the left, the hydraulic line 14 functions as a feed line, and the hydraulic line 13 functions as a return line. The orbit roll 4 and the hydraulic pump 6 constitute hydraulic oil supply means. The hydraulic oil supply means and the steering cylinder 12 constitute a drive means for driving the steered wheels 19 to a steering angle corresponding to the operating position of the steering wheel 2.

The steering cylinder 12 includes a cylindrical cylinder tube 15 fixed to a vehicle body, a piston 16 reciprocally disposed inside the cylinder tube 15, and a pair of left and right piston rods 17a protruding from both ends of the cylinder tube 15. , 17b. Each hydraulic line 13,1
4 is communicated with each chamber of the cylinder tube 15 divided into two chambers by a piston 16.

Left and right steering wheels (rear wheels) 19, 19 are connected to the distal ends of the piston rods 17a, 17b via link mechanisms 18a, 18b, and when the steering cylinder 12 is driven, both steering wheels are steered. The wheels 19 are steered left and right about the kingpin 20.

The hydraulic lines 13 and 14 are connected by a bypass line 21, and an electromagnetic switching valve 22 and a throttle valve 23 as correction means are provided in the bypass line 21. The bypass line 21 constitutes a conduit through which part of the hydraulic oil discharged from the hydraulic oil supply means can be returned to the drain tank 8 before being supplied to the steering cylinder 12. The electromagnetic switching valve 22 is for controlling the amount of hydraulic oil returned to the drain tank 8 via the bypass line 21. By opening the electromagnetic switching valve 22 to recirculate a part of the hydraulic oil, the ratio of the displacement of the piston 16 in the steering cylinder 12 to the amount of operation of the handle 2 is reduced, and the idle state of the handle 2 is created. Has become. The position of the steering wheel 2 is corrected by causing the steering wheel angle to catch up with the steering angle (steering angle) of the steered wheels 19 by idling of the steering wheel 2.

As the electromagnetic switching valve 22, a two-position switching duty valve is used, and a high-speed (two-position switching duty position) is provided for the electromagnetic switching valve 22. For example, switching is possible in 1 to 2 milliseconds). A spool (not shown) constituting the electromagnetic switching valve 22 is urged toward a shut-off position by a spring 24. The electromagnetic switching valve 22 is disposed at a communication position when the solenoid 25 is excited, and the solenoid 25 is demagnetized. When it is done, it will be placed in the blocking position. Solenoid 2
Numeral 5 is electrically connected to the controller 26, and is duty-controlled based on a control signal from the controller 26. The throttle valve 23 is provided with a bypass line 21 so that the steering wheel 19 can be steered by operating the steering wheel even if the electromagnetic switching valve 22 remains open due to a failure or the like.
This is for reducing the flow rate of the water.

The controller 26 is electrically connected to a rotary encoder 27 constituting steering wheel angle detecting means and operating direction detecting means, and a potentiometer 28 as steering angle detecting means. The rotary encoder 27 includes a disk 29 provided on the steering shaft 3 so as to be integrally rotatable, and slits 29 a and 29 b formed in the disk 29.
(See FIG. 6). The detection signal of the steering wheel angle sensor 30 is input to the controller 26.

As shown in FIGS. 3 and 6, a plurality of (40 in this embodiment) slits 29a are formed at equal intervals along the circumferential direction of the disk 29, The slit 29b for calibration (shown only in FIG. 6)
Are formed. The handle angle sensor 30 incorporates a first transistor 31, a second transistor 32, and a correction transistor 33 (all shown in FIG. 4) which are three phototransistors constituting each photocoupler.

The first transistor 31 and the second transistor 32 are for detecting light passing through the slit 29a, and a detection signal (digital signal) SS1 that repeats on / off 40 times each time the handle 2 rotates once. , S
S2 (shown in FIG. 5) is output. Both signals SS
1, SS2 so that their phases are electrically shifted by 90 °,
That is, it is set so as to be shifted by 1/4 cycle. And
By detecting and counting the edges of both signals SS1 and SS2, the rotation angle of the handle 2 (hereinafter referred to as the handle angle θ) can be detected with a resolution obtained by dividing one rotation of the handle 2 into 160. The steering wheel angle θ is counted by a steering counter 44 (see FIG. 4) described later as a count value C corresponding to the steering wheel relative angle.

The correction transistor 33 is for detecting light passing through the slit 29b for position correction, and is a detection signal (digital signal) SSC (FIG. 9) which is turned on when the handle 2 is placed at the neutral position. 5) is output. The ON signal from the correction transistor 33 is used to calibrate the count value C of the steering counter 44.

The potentiometer 28 is connected to the right steering wheel 19.
, And detects a turning amount of the king pin 20 and outputs a tire turning angle signal R corresponding to a turning angle of the steered wheel 19 to the controller 26.

A vehicle speed sensor 35 as vehicle speed detecting means is provided near a front differential ring gear 34 for transmitting rotation to driving wheels (not shown), and a vehicle speed signal v corresponding to the vehicle speed is sent from the controller to the controller. 26.

As shown in FIG. 4, the controller 26
The microcomputer 36 includes a microcomputer 36, an edge detection circuit 37 constituting the steering wheel angle detection means, AD conversion circuits 38 and 39, a drive circuit 40 constituting the control means, and the like. The microcomputer 36 includes a central processing unit (CPU) 41,
Read only memory (ROM) 42, read / write rewritable memory (RAM) 43, steering counter 44, control cycle counter 45, clock circuit 46, input interface 47
And an output interface 48. The potentiometer 28 and the vehicle speed sensor 35 include an AD conversion circuit 38,
39 are connected to each other. The CPU 41 constitutes control means and target position calculating means and functions as target direction detecting means. The ROM 42 constitutes a target position calculating means. The steering counter 44 constitutes a steering wheel angle detecting means.

The CPU 41 executes various arithmetic processes based on various program data stored in the ROM 42, and stores the arithmetic results and the like in the RAM 43. The ROM 42 stores program data and the like for the knob position correction control processing shown in the flowcharts of FIGS. In these flowcharts, step S30 constitutes target position computing means, S40 constitutes target direction detecting means, S100 constitutes duty value computing means, and S210 to S290 constitute operation direction detecting means.

Each detection signal SS from the first transistor 31, the second transistor 32 and the correction transistor 33
1, SS2 and SSC are the CPU 41 and the edge detection circuit 3
7 is input. Edge detection circuit 3
7 is the rising edge of each detection signal SS1, SS2, SSC.
This is for detecting a falling edge, and outputs edge signals SE1, SE2, and SEC at the time of edge detection.

The steering counter 44 is for counting the steering wheel angle θ of the steering wheel 2. The CPU 41 changes the count value C of the steering counter 44 by "1" each time the edge signals SE1 and SE2 are input, that is, each time the steering wheel 2 is rotated 1/160 (= 2.25). The steering counter 44 has a knob 2a represented by a steering wheel relative angle.
(The steering wheel angle θ) is counted as a count value C of “0 to 159”. Steering counter 4
4 is set so that the count value C when the knob 2a is located at the neutral position becomes “80”. The count value C is determined based on an edge signal SEC output from the edge detection circuit 37 every time the knob 2a passes the neutral position, by an interrupt process so that the time when the knob 2a is located at the neutral position becomes "80". It is to be calibrated.

The control cycle counter 45 counts the number of executions of the knob position correction control processing. Each time the count value C of the steering counter 44 is changed, that is, each time the steering wheel 2 is rotated by 1/160. Is cleared. Therefore, by looking at the count value C1 of the control cycle counter 45 when the count value C of the steering counter 44 is changed, the elapsed time required for the steering wheel 2 to be rotated 1/160 times can be indirectly determined. I have. Control cycle counter 45
Is used to determine whether or not the steering operation is stopped.

The CPU 41 executes the knob position correction control process shown in FIG. 1 at predetermined time intervals to (for example, 10 milliseconds) based on the clock signal from the clock circuit 46. However, when the edge signals SE1 and SE2 are input, the interrupt routine shown in FIG. 2 is executed with priority, and when the edge signal SEC is input, the calibration of the count value of the steering counter 44 is executed by interrupt processing.

The interrupt routine shown in FIG. 2 is executed preferentially by interruption when any of the edge signals SE1 and SE2 is input. In this interrupt routine, determination processing of the rotation direction of the steering wheel 2 (hereinafter, referred to as steering direction), counting processing of the steering counter 44, clear processing of the control cycle counter 45, and determination of stop of steering operation are performed.

The steering direction of the steering wheel 2 is determined by the types of the rising and falling edges of the detected edge signals SE1 and SE2, and the output level (the level of the signals SS1 and SS2) of the transistor which is not the output source of the edge signals. Is determined from the two pieces of determination data. That is, as shown in FIG. 5, for example, when the signal SS1 is at a “rising edge”, it is determined that “right steering” is performed when the signal SS2 is at H level and “left steering” is performed when the signal SS2 is at L level. When the signal SS1 is at the “falling edge”, the signal SS2
The relationship between the output level and the steering direction is opposite to that at the start. When the signal SS2 is at the “rising edge”, if the signal SS1 is at L level, “right steering” and the signal S
If S1 is at the H level, it is determined that "left steering" has been performed. Signal S
When S2 is a “falling edge”, the relationship between the output level of the signal SS1 and the steering direction is opposite to that at the time of rising.

The tire turning angle signal R from the potentiometer 28 is input to the CPU 41 as an 8-bit AD value (0 to 255) via an AD conversion circuit 38.
1 takes in the input AD value as the tire turning angle R.
The input value from the potentiometer 28 is AD value = “12
8 ”is associated with the tire turning angle R =“ 0 ° ”, and when the AD value is smaller than 128 (that is, the R value is“ negative ”), the steering is left (left turning angle), and the AD value is larger than 128 (that is, R). When the value is “positive”, it is recognized as right steering.

The vehicle speed signal v from the vehicle speed sensor 35 is input to the CPU 41 as an 8-bit AD value (0 to 255) via an AD conversion circuit 39. Also,
A control signal for controlling the duty of the electromagnetic switching valve 22 is output from the CPU 41 via the drive circuit 40 connected to the output interface 48.

The ROM 42 stores a map M2 shown in FIG. The map M2 is for obtaining a target steering wheel angle θg, which is a target position for correcting the position of the knob 2a, from the tire turning angle R. Map M2 contains
In the entire steering range between the stroke ends RE and LE of the steered wheels 19, the tire turning angle Rg is determined so that the target steering wheel angle θg is determined by the steering wheel relative angle corresponding to the tire turning angle R.
Control target line L that associates the target steering wheel angle θg
Is set. This control target line L is an ideal control line on the assumption that the orbit roll efficiency (actual discharge amount / theoretical discharge amount) is 100%. In this embodiment, since the steering wheel angle θ = 0 ° (count value C = 80) when the knob 2a is in the neutral position, “−180 ° to 180 °” of the target steering wheel angle θg is obtained. The target steering count value Cg is set in association with “0 to 159”.

In the knob position correction control process, the CPU 41 calculates a deviation Δθ between the steering wheel angle θ and the target steering wheel angle θg obtained from the tire turning angle R, and this deviation Δθ is set to an allowable value θo (for example, about 5 °). ) Perform the knob position correction so that it falls within the following. The shift amount Δθ referred to here is the same as FIG.
As shown in (a) and (b), it means the amount of deviation between the current knob position and the target knob position in the shortest path. When the actual deviation amount Δθs of the knob 2a exceeds 180 °, the deviation amount Δθ
Is represented by “360 ° −Δθs”.

As shown in FIGS. 7A and 7B, the conditions for executing the knob position correction are different depending on whether or not the deviation amount Δθ is equal to or smaller than a predetermined angle A °. That is, when the shift amount Δθ is equal to or smaller than A ° (that is, when the actual shift amount Δθs is Δ
θs ≦ A or Δθs ≧ (360−A) °) indicates that the operating direction in which the handle 2 is operated is a direction in which the current knob position approaches the target knob position via the shortest path (hereinafter, referred to as “the target knob position”).
The knob position correction is executed only when the position matches the target direction). Further, when the shift amount Δθ exceeds the predetermined angle A ° (that is, when the actual shift amount Δθs is A ° <Δθs <
In (360-A) °), the knob position correction is always executed regardless of the handle operation direction.

Here, the predetermined value A is larger than the predetermined value even if the correction is executed when the steering wheel 2 is operated in the direction opposite to the target direction when the deviation amount becomes larger than the predetermined value. Rather, it is a boundary value set in expectation that the probability of reduction will be higher. In the present embodiment, a value in the range of 80 ° to 120 ° is set as the predetermined value A °.

When executing the steering wheel angle correction (knob position correction), the CPU 41 controls the duty of the electromagnetic switching valve 22. The CPU 41 calculates a duty value corresponding to the detected vehicle speed in a map M1 shown in FIG.
Is calculated from Then, a control signal for performing duty control of the electromagnetic switching valve 22 with the calculated duty value is output to the electromagnetic switching valve 22 via the drive circuit 40 connected to the output interface 48.

Next, the operation of the power steering apparatus 1 configured as described above will be described. During operation of the forklift F, the operator operates the handle 2 by gripping the knob 2a. When the handle 2 is operated and the steering shaft 3 is driven to rotate, hydraulic fluid is discharged from the valve unit 5 according to the amount of operation of the handle 2 via the steering cylinder 12 according to the amount of operation of the handle 2. The steered wheels 19 are steered. When the steering wheel operating speed is low, or when the orbit roll efficiency is reduced due to oil leaks in the hydraulic system such as the steering cylinder 12, the knob 2a may deviate from the normal position. Therefore, knob position correction control for correcting the position of the knob 2a to a normal position corresponding to the tire turning angle is performed.

Hereinafter, the knob position correction control executed by the CPU 41 will be described with reference to the flowcharts shown in FIGS. In the initial state, it is assumed that the electromagnetic switching valve 22 is located at the shut-off position, that is, the electromagnetic switching valve 22 is stopped.

While the engine of the forklift F is being driven, CP
U41 includes detection signals SS1, SS2, and SSC from the transistors 31, 32, and 33, edge signals SE1, SE2, and SEC from the edge detection circuit 37, a tire turning angle signal R from the potentiometer 28, and the vehicle speed sensor 3.
5 is input.

The CPU 41 executes the knob position correction control processing shown in FIG. 1 every predetermined time to (for example, 10 milliseconds). When the edge signals SE1 and SE2 are input, FIG.
The interrupt routine shown in (1) is executed with priority. In this interrupt routine, in order to appropriately change data necessary for executing the knob position correction control to an appropriate value, a counting process of the steering counter 44, an arithmetic process for determining the steering direction of the steering wheel 2, a steering operation, A stop determination process and a clear process of the control cycle counter 45 are executed. At the start of the execution of the knob position correction control process shown in FIG.
At 0), a count process for incrementing the count value C1 of the control cycle counter 45 is performed, and the count value C1 of the control cycle counter 45 is incremented by "1" every execution cycle to of the process.

First, the interrupt routine shown in FIG. 2 will be described. When receiving the edge signals SE1 and SE2, the CPU 41 preferentially executes the interrupt routine. In this routine, the processing of S210 to S290 is performed by the signals SS1 and S2.
This is a process for determining the steering direction of the steering wheel 2 using S2, SE1, and SE2. The type of the edge signal (rising edge / falling edge) on which the routine is executed and the output of the edge signal The steering direction of the steering wheel 2 is determined based on the two determination data with the output level of the other transistor that is not the original.

First, in step 210, the output source of the edge signal is the first transistor 31 and the second transistor 32.
Is determined. In steps 220 and 230, it is determined whether or not the edge of the signal (SS1 or SS2) on which the output of the edge signal is based is the rising edge. In this determination process, an edge flag prepared for each edge signal output source is used. The edge flag includes information on the type of the next detected edge determined by the output level of the transistor that has output the edge signal at that time, which was determined in the previous interrupt routine (if the output level is H level, “falling edge” Edge ", if it is at L level," rising edge "
Has been saved. Therefore, if the edge flag corresponding to the output source of the edge signal which is the basis of this routine is "0", the current detected edge is determined to be "falling edge", and if "1", it is determined to be "rising edge". I do.

The processing of S240 to S270 is a processing of determining the output level of the other transistor which is not the transistor that is the output source of the edge signal. The signal is determined based on the determined output level and the type of the edge determined earlier. SS
The steering direction of the steering wheel 2 is determined by utilizing the fact that the phase relationship between the advance angle and the retard angle of SS2 is reversed depending on the steering direction of the steering wheel 2 (S280, S290). The result of this steering direction determination is set in a steering direction flag. The steering direction flag is set to "0" for leftward direction and "1" for rightward direction.

In step 300, the steering counter 44 performs a counting process according to the result of the determination of the steering direction. That is, when the steering direction is “rightward”, the count value C
Is incremented, and the count value C is decremented when the steering direction is “leftward”. However, when the count value C before the increment is “159”, the count value C is set to “0”, and when the count value C before the decrement is “0”, the count value C is set to “1”.
59 ". Thus, the steering counter 44 counts a count value C corresponding to the steering wheel angle θ represented by the steering wheel relative angle.

In step 310, the control cycle counter 4
It is determined whether or not the count value (control cycle count value) C1 of 5 is equal to or greater than a set value Co set for determining that the steering operation is stopped. The count value C1 of the control cycle counter 45 is cleared each time the interrupt routine is executed, that is, every time the handle 2 is operated 1/160 rotation (2.25 °) (S330), and the knob position correction control processing is executed. It is incremented every cycle to (for example, 10 milliseconds) (see S10 in FIG. 1). Therefore, the count value C1 of the control cycle counter 45 represents a value corresponding to the elapsed time until the steering wheel 2 is operated by 1/160 rotation, and the count value C1 is set to the set value Co.
If so, the steering operation is considered to be stopped.

If the count value C1 of the control cycle counter 45 is equal to or greater than the set value Co, "steering operation stop determination" is made and the steering stop determination flag is set to "1" (S3).
20) After that, the control cycle counter 45 is cleared (S33).
0). If the count value C1 is less than the set value Co, the control cycle counter 45 is cleared while the steering stop determination flag is not changed and remains "0" (S330).

As described above, during execution of the knob position correction control processing, the current steering wheel angle θ can be found by looking at the count value C of the steering counter 44, and the current steering wheel operating direction can be found by looking at the steering direction flag. By looking at the steering stop determination flag, it can be determined whether or not the steering operation is stopped.

Next, the knob position correction control processing will be described with reference to FIG.
A description will be given based on the flowchart of FIG. First step 1
At 0, the control cycle counter 45 is incremented. In step 20, the steering wheel angle θ and the tire turning angle R
Read. The steering wheel angle θ is read from the count value C of the steering counter 44.

In step 30, the map M2 shown in FIG.
Is used to calculate the target steering wheel angle θg from the tire turning angle R. The target steering wheel angle θg is equal to the target steering count value C.
g.

In step 40, a target direction in which the knob deviation correction is executed is calculated. That is, it is determined which of the left and right directions is the shortest path from the current knob position to the target knob position. Deviation ΔC between current count value C of steering counter 44 and target steering count value Cg = | C−Cg
Is calculated, and if the deviation ΔC is equal to or less than “80” (that is, the deviation | θ−θg | ≦ 180 ° in terms of steering wheel angle), the target direction is set to “right” when C <Cg holds, > C
When g is established, the target direction is determined to be “leftward”. Also,
If the deviation ΔC exceeds “80” (that is, the deviation | θ−θg |> 180 ° in terms of steering wheel angle), the target direction is set to “left” when C <Cg holds, and the target direction is set when C> Cg holds. The direction is determined to be “rightward”. The result of the determination of the target direction is set in a target direction flag, and is set to "0" when the target direction is "left" and "1" when the target direction is "right".

In step 50, a deviation amount Δθ between the current knob position and the target knob position is calculated. That is, when the deviation | θ-θg | is 180 ° or less in terms of the steering wheel angle, Δθ = | θ-θg |, and the deviation | θ-θg |
When it exceeds 0 °, Δθ = 360 ° − | θ−θg |
And Thus, the shift amount Δθ between the current knob position and the target knob position in the shortest path is obtained. The shift amount Δθ is calculated in terms of the count value C using the count values C and Cg in the processing.

In step 60, it is determined whether or not the steering operation is stopped. That is, it is determined whether or not "1" is set by looking at the steering stop determination flag. If "1" is set, it is determined that the steering operation is stopped. If the steering stop determination flag is “1”, step 1
The program proceeds to 20 to execute a valve stop command. Therefore, the electromagnetic switching valve 22 is not driven and is kept at the shut-off position. Therefore, the knob position is not always corrected while the steering operation is stopped. On the other hand, if the steering operation is not stopped, the process proceeds to step 70.

In the next step 70, it is determined whether or not the deviation amount Δθ is equal to or smaller than the allowable value θo. If the deviation amount Δθ is equal to or smaller than the allowable value θo, the process shifts to step 120 to execute a valve stop command. Therefore, the deviation amount Δθ becomes the allowable value θo
In the following cases, the knob position correction is not performed. On the other hand, when the deviation amount Δθ exceeds the allowable value θo, the routine proceeds to step 80. In step 80, it is determined whether the deviation amount Δθ is equal to or smaller than a predetermined value A °. If the deviation amount Δθ exceeds the predetermined value A °, the process proceeds to step 100.
In step 100, a duty value corresponding to the vehicle speed v is calculated from a map M1 shown in FIG. And step 1
The routine proceeds to step 10, where a valve drive command for outputting a control signal for duty-controlling the electromagnetic switching valve 22 is executed in step 110. Therefore, as shown in FIG.
When θ exceeds the predetermined value A °, the knob position correction is performed regardless of whether the operation direction of the steering wheel 2 is the left direction (b direction) or the right direction (c direction), and the knob 2a is moved from the current position. It will approach the target position. When the handle 2 is operated in the direction c, the correction is performed through the longest path. However, since the original deviation Δθ is larger than A °, the deviation Δθ is often reduced rather than enlarged. Thus, the chance of performing the knob position correction is substantially increased, and it is possible to avoid leaving the deviation amount exceeding A ° as much as possible.

On the other hand, if Δθ ≦ A ° is satisfied in step 80, the routine goes to step 90, where it is determined whether or not the steering direction matches the target direction. This determination is made based on whether or not both flag values of the steering direction flag and the target direction flag match. When the steering direction is equal to the target direction, the process proceeds to step 100 to obtain a duty value corresponding to the vehicle speed v, and then a valve drive command is issued at step 110. When the steering direction = target direction is not established, the process proceeds to step 120 to issue a valve stop command.

Accordingly, when the knob 2a is located at the solid line position in FIG. 7A, the knob position is corrected when the handle 2 is operated in the a1 direction (left direction) where the knob 2a approaches the target position by the shortest path. Is executed, and when the handle 2 is operated in the x1 direction (right direction) in which the knob 2a moves away from the target position (that is, approaches in the longest route), the knob position correction is not executed. When the knob 2a is at the position indicated by the dashed line in FIG. 7A that is shifted from the normal position by (360-A) ° or more, the handle is moved in the a2 direction (rightward) where the knob 2a approaches the target knob position by the shortest path. When the handle 2 is operated, the knob position correction is executed. When the handle 2 is operated in the x2 direction (left direction) in which the knob 2a moves away from the target position, the knob position correction is not executed. Further, even if the actual shift amount is 360 ° or more, the correction amount is always less than 360 ° because only the relative angle is considered. For example, even if the knob 2a is actually shifted by one or two rotations, the knob position correction is not executed if the position of the knob 2a is correct as viewed from the operator.

When the knob position correction is performed, the correction amount per unit time is changed according to the vehicle speed v, and the electromagnetic switching valve 22 is controlled so that the correction amount per unit time decreases as the vehicle speed increases. Duty control is performed. As a result, when the steering wheel is operated during high-speed running, the amount of correction per unit time is reduced even if the knob position correction is executed, so that the operator intends to change the course (turning or curve running). When the steering wheel is turned, even if the knob position correction is executed, the operator does not feel uncomfortable.

This embodiment has the following effects. (A) Since the correction amount per unit time by the steering wheel angle correction means is smaller at high speed running than at low speed running, when the course is changed at high speed running, the steering wheel follow-up performance is prevented from being deteriorated. It is possible to prevent the operator from feeling uncomfortable. Further, when the steering wheel angle correction (knob position correction) is necessary, the correction is executed, so that it is possible to prevent the knob displacement from increasing.

(B) Since the correction amount per unit time by the correction means is reduced in accordance with the increase in the vehicle speed, the steering wheel angle correction (knob position correction) is executed with an appropriate correction amount corresponding to the vehicle speed. Thus, it is possible to more reliably prevent the operator from feeling uncomfortable. In addition, steering wheel angle correction (knob position correction) is performed efficiently.

(C) Since the electromagnetic switching valve 22 which is duty-controlled is used as the correction means, the correction amount per unit time can be easily changed by changing the duty value.

(D) Since the target steering wheel angle θg is determined based on the tire turning angle, the target steering wheel angle θg can be set by the relative steering wheel angle, and the knob position is adjusted to adjust the steering wheel relative angle. Can be realized. Therefore, the actual shift amount is 360 °
Even with the above, for example, the correction amount can be reduced by one or two rotations. Therefore, useless idling of the handle 2 can be eliminated.

(E) Throttle valve 23 in bypass line 21
Is provided, even if the electromagnetic switching valve 22 remains open due to a failure or the like, the steering wheel 19
Steering becomes possible.

(F) When the deviation Δθ is equal to or smaller than A °, the correction is executed only when the handle 2 is operated in the direction passing through the shortest path. , It is possible to execute a correction for reducing the shift amount. In addition, the actual shift amount is, for example, 280 °.
Even 75 ° (when considering the allowable value θo = 5 °)
And the actual shift amount exceeds A ° and is 360 °.
Even in the case of less than the above, the correction amount can be smaller than the actual deviation amount. As a result, the idling amount of the handle 2 required for the knob position correction can be further reduced.

(G) Since the rotary encoder 27 is used to detect the steering wheel angle θ, the detection value (count value C) at the steering wheel relative angle corresponding to the position of the knob 2a is calculated over the entire rotation of the steering wheel 2 (360 °). Can be detected. As a result, unlike the case where a rotary potentiometer is used, the knob position can be corrected regardless of the position of the handle 2. Accordingly, the amount of steering wheel operation required for the correction is reduced and the correction is completed early, so that the convergence of the knob 2a to the neutral position when the steered wheels 19 are returned to the straight traveling posture can be improved.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. This embodiment is different from the above-described embodiment in that an on / off solenoid valve is used instead of the duty valve as the electromagnetic switching valve 22 functioning as a correction unit. Other hardware configurations are the same as those of the above-described embodiment. A part of the knob position correction control program and a map for setting the excitation time of the solenoid 25 when driving the electromagnetic switching valve 22 are different from those of the above-described embodiment. Is different. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and the detailed description is omitted.

The duty valve has a response of 1-2 ms.
(Milliseconds), whereas the on / off solenoid valve has an order of magnitude of 10 to 20 ms slower by one digit. Therefore, it is difficult for an on / off solenoid valve to finely adjust the apparent opening degree in a short time by performing on / off control at high speed like a duty valve.
Therefore, in this embodiment, the apparent opening degree of the electromagnetic switching valve 22 is adjusted by adjusting the energization time of the solenoid 25 during one cycle of about several tens to hundreds of milliseconds, thereby reducing the amount of correction. Adjustments are made.

For example, the response of the electromagnetic switching valve 22 is 20 m
When one control cycle is set to 100 ms, by changing the continuous excitation time (continuous energization time) of the solenoid 25, the apparent opening degree is changed as shown in FIGS. It is changed to 20%, 40%, 60% and 80%. Note that the horizontal axis of each graph represents the energization time. (A) energizes (turns on) the solenoid 25 for 20 ms and turns off 80 ms; (b) energizes (turns on) the solenoid 25 for 40 ms and turns off 60 ms; (c) energizes (turns on) the solenoid 25 for 60 ms. (D) shows a case where the solenoid 25 is energized (turned on) for 80 ms and is turned off for 20 ms. In addition, when current is continuously supplied for one cycle, the opening becomes 100%.

In this embodiment, since it is difficult to finely adjust the opening, the map M3 for obtaining the correction amount corresponding to the vehicle speed v is, as shown in FIG. 10, a graph represented by a discontinuous line. Become. In FIG. 10, the vertical axis represents the percentage of the continuous energization time in one control cycle of the electromagnetic switching valve 22 in%.

In this embodiment, the knob position correction control program is basically the same as that of the previous embodiment. However, in the flowchart of FIG. 1, in step 100, the duty value corresponding to the vehicle speed is calculated from the map M1 in step 100. Instead, the continuous energization time of the electromagnetic switching valve 22 corresponding to the vehicle speed v is obtained using the map M3 of FIG. And
In step 110, a valve drive command for outputting a control signal for continuously energizing the electromagnetic switching valve 22 for a predetermined time is executed.

Therefore, in this embodiment, the same effects as those of the above embodiment can be obtained. However, in the above embodiment, the correction amount can be adjusted in a more appropriate state, and the control cycle of one knob position correction can be shortened.

In the case of this embodiment, since the electromagnetic switching valve 22 can be used at a lower price than the duty valve, the manufacturing cost of the entire apparatus can be reduced. (Third Embodiment) Next, a third embodiment will be described with reference to FIG. This embodiment is different from the first embodiment in that a proportional valve is used instead of the electromagnetic switching valve 22 functioning as a correction unit. The other hardware configuration is the same as that of the first embodiment. A part of the knob position correction control program and a map for setting the opening when driving the proportional valve are different from those of the first embodiment. ing. Therefore, only different points from the first embodiment will be described.

FIG. 12 is a graph showing a map M4 for determining the opening of the proportional valve corresponding to the vehicle speed v. Since the valve opening of the proportional valve can be continuously adjusted, the map M4 is represented as a continuous line. The vertical axis indicates the opening of the proportional valve (the magnitude of the drive current of the proportional valve).

In this embodiment, the knob position correction control program is basically the same as that of the first embodiment, but in the flowchart of FIG.
Instead of calculating the duty value corresponding to the vehicle speed from the map M1, the opening of the proportional valve corresponding to the vehicle speed v is obtained using the map M4 in FIG. And step 110
Executes a valve drive command for outputting a control signal for supplying a drive current for driving the proportional valve at a predetermined opening.

Therefore, also in this embodiment, the first
The same effect as that of the embodiment is exerted. However, in the case of this embodiment, since the proportional valve is used, the opening can be more reliably adjusted to the predetermined opening degree as compared with the duty valve.

(Fourth Embodiment) Next, a fourth embodiment will be described with reference to FIGS. This embodiment is different from the first embodiment in that the electromagnetic switching valve 22 and the variable throttle valve are used in combination as correction means. Further, a part of the knob position correction control program and a map for setting the opening when driving the variable throttle valve are different from those of the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIG. 14, the bypass line 21
The electromagnetic switching valve 22 and the variable throttle valve 49 are provided halfway. The electromagnetic switching valve 22 and the variable throttle valve 49 constitute a correction unit. An on / off solenoid valve is used for the electromagnetic switching valve 22. The flow rate of the variable throttle valve 49 when fully opened is substantially the same as the flow rate of the throttle valve 23 of the first embodiment. The drive of the electromagnetic switching valve 22 and the variable throttle valve 49 is controlled via a drive circuit 40 provided in the controller 26. When performing the knob position correction, the CPU 41 outputs, via the drive circuit 40, a control signal for maintaining the electromagnetic switching valve 22 in the open state and maintaining the variable throttle valve 49 at a predetermined opening corresponding to the vehicle speed v. I do.

FIG. 13 shows a variable throttle valve 49 corresponding to the vehicle speed v.
5 is a graph showing a map M5 for determining an opening degree of the vehicle.
Since the valve opening of the variable throttle valve 49 can be continuously adjusted, the map M5 is represented as a continuous line. The vertical axis indicates the opening degree of the variable throttle valve 49 (the magnitude of the drive current of the variable throttle valve).
Is shown.

In this embodiment, the knob position correction control program is basically the same as that of the first embodiment, but in the flowchart of FIG.
Instead of calculating the duty value corresponding to the vehicle speed from the map M1, the opening degree of the variable throttle valve 49 corresponding to the vehicle speed v is obtained using the map M5 in FIG. Then, in step 110, a drive current for driving the variable throttle valve 49 at a predetermined opening is supplied, and a valve drive command for outputting a control signal for opening the electromagnetic switching valve 22 is executed.

Therefore, also in this embodiment, the first
The same effect as that of the embodiment is exerted. Further, in this embodiment, since the variable throttle valve 49 is used, the opening is more reliably adjusted to a predetermined opening degree as compared with the duty valve, as in the third embodiment using the proportional valve. it can. However, since the electromagnetic switching valve 22 is required, the structure and control are slightly more complicated than in the third embodiment.

(Fifth Embodiment) Next, a fifth embodiment will be described with reference to FIG. In this embodiment, 18
The difference from the above embodiments is that the knob position correction is performed only when the handle 2 is operated in a direction approaching the target position from 0 °. The knob position correction control program is basically the same as that corresponding to each of the above-described embodiments.
The point that “0” is omitted and the calculation in calculating the target direction in step 40 are slightly different.

More specifically, the conditions for determining whether or not to perform the knob position correction process differ depending on whether the steering wheel angle θ is less than 180 ° or more than 180 °. As a judgment condition,
There is a magnitude of the shift amount Δθ. When the steering wheel angle θ is equal to or less than 180 °, as shown in FIG. 15A, three types of target positions satisfying the condition that the vehicle approaches the target when the steering wheel is operated are different from the current knob position. Position P1,
P2 and P3 exist. That is, the target position P1 where the count value of the steering counter 44 is smaller than the current position when the deviation amount Δθ is 180 ° or less, and the target position P where the count value of the steering counter 44 is larger than the current position when the deviation amount Δθ is 180 ° or less.
3. There is a target position P2 in which the deviation amount Δθ is larger than 180 ° and the count value of the steering counter 44 is larger than the current position.

The steering directions for approaching the target positions P1, P2, and P3 are leftward for the target positions P1 and P2, and rightward for the target position P3. The target direction of each of the target positions P1, P2, and P3 determined by the method of determining the target direction in step 40 is leftward for the target positions P1 and P2, and rightward for the target position P3. . That is, in all three types of target positions P1, P2, and P3, when the target direction and the steering wheel steering direction match, the steering direction approaches the target.

On the other hand, when the steering wheel angle θ is larger than 180 °, the target position satisfying the condition that the target is approached when the steering wheel is operated is, as shown in FIG. Three types of target positions P1, P2
P3 is present. That is, the target position P3 where the count value of the steering counter 44 is smaller than the current position when the shift amount Δθ is 180 ° or less, the target position P2 where the count value of the steering counter 44 is larger than the current position when the shift amount Δθ is 180 ° or less, and the shift amount. There is a target position P1 where Δθ is larger than 180 ° and the count value of the steering counter 44 is smaller than the current position.

The steering direction for approaching each of the target positions P1, P2, and P3 is rightward for the target positions P1 and P2, and leftward for the target position P3. The target direction of each of the target positions P1, P2, and P3 determined by the method of determining the target direction in step S40 is rightward for the target positions P1 and P2, and leftward for the target position P3. . That is, in all three types of target positions P1, P2, and P3, when the target direction and the steering wheel steering direction match, the steering direction approaches the target.

Therefore, in the flowchart of FIG.
If step 80 is omitted and the steering direction matches the target direction in step 90, the process proceeds to step 100, so that the knob position correction is performed only when approaching the target. As a result, the shift amount Δθ can be reduced whenever the knob position correction (handle angle correction) is performed. Further, in each of the above-described embodiments, when the steering wheel 2 is corrected and steered in small increments, there is a possibility that the deviation increases. However, in this embodiment, even if the steering wheel 2 is smallly steered once the deviation has occurred. The deviation gradually converges without expanding.

The present invention is not limited to the above embodiments, but can be embodied as follows, for example. The vehicle speed detecting means is not limited to the vehicle speed sensor 35 that detects the rotation of the front differential ring gear 34, but may be a vehicle speed sensor that detects the rotation of another portion that rotates integrally with the drive wheels.

Instead of reducing the correction amount per unit time of the correction means in response to an increase in vehicle speed, the correction amount may be made smaller during high-speed running than during low-speed running. Here, high-speed running means, for example, in the case of a forklift, a maximum speed (about 20 km / h) of about 7
It means speed of ~ 80% or more. Also in this case, the steering wheel can be operated without feeling uncomfortable during high-speed running, and the steering wheel angle is also corrected. Further, control becomes easy.

Even when a valve having a configuration in which the correction amount can be continuously changed is used as the correction means, the correction amount is changed stepwise according to the vehicle speed as in the second embodiment. Is also good.

The absolute encoder may be used as a rotary encoder for detecting the steering wheel angle instead of the incremental rotary encoder. In this case, the steering operation direction can be easily known from the detected angle of the rotary encoder in the previous control cycle and the detected angle of the rotary encoder in the current control cycle.

A configuration in which the steering wheel angle is detected as an absolute angle, for example, the rotation of a steering shaft supporting the steering wheel is reduced through a reduction mechanism such as a worm gear as in the device disclosed in Japanese Patent Application Laid-Open No. Hei 4-24270. The rotation amount may be detected by a potentiometer. In a configuration in which the steering wheel angle is detected as an absolute angle, it may be determined from the steering wheel angle whether or not the steering angle of the steered wheels is within the straight traveling range. In this case, an accurate determination result can be obtained by taking into account the amount of displacement of the steering wheel.

A rotary potentiometer may be used as the steering wheel angle detecting means. In this case, 360 °
Although a non-detection area exists in a part of the entire area, setting such that the steering wheel angle “0 °” is detected in the center of the detectable area causes almost no problem even if the non-detection area exists.

The present invention is not limited to a forklift, and may be applied to an industrial vehicle other than a forklift having a fully hydraulic power steering device. The present invention may be implemented for the purpose of correcting the position of a handle without a knob.

The "forklift" referred to in this specification
An attachment other than a fork as a cargo handling attachment, for example, a roll clamp used for transporting roll paper, a block clamp used for transporting blocks or stacking work, a coil or a coil such as a coil and a wire or cable wound in a coil. Includes those equipped with rams and the like used to transport cargo in the shape of a letter.

The technical ideas (inventions) other than those described in the claims, which have been grasped from the above embodiments, will be described below together with their effects. (1) In the invention according to any one of claims 1 to 7, the handle angle detection means includes a rotary encoder having a disk that rotates integrally with the steering shaft. In this case, unlike the case of using a rotation detector using a rotary potentiometer, one of the handles is different.
The rotation position (angle) can be detected over the entire rotation area,
The knob position can be corrected regardless of the position of the handle.

(2) A fully hydraulic power steering device is provided, and when the positional relationship between the steering wheel angle and the steering angle of the steered wheels deviates by a predetermined amount or more, the steering wheel is idled at the time of operating the steering wheel. A steering angle correction apparatus for an industrial vehicle, comprising: a steering angle correction unit for correcting a deviation; wherein the correction amount per unit time by the steering wheel angle correction unit can be changed. In this case, by changing the correction amount according to the driving situation (for example, the vehicle speed) of the industrial vehicle, it is possible to avoid giving the operator an uncomfortable feeling when operating the steering wheel.

(3) In the invention according to claim 6,
The flow rate of the variable throttle valve when it is fully opened is set to a value that enables steering of a steered wheel by operating a steering wheel. In this case, even if the electromagnetic switching valve and the variable throttle valve remain open due to a failure or the like, steering of the steered wheels by operating the steering wheel can be performed.

[0114]

As described in detail above, claims 1 to 7 are provided.
According to the invention described in (1), the steering wheel operation can be performed without a sense of incongruity at the time of high-speed traveling, and it is not necessary to stop the steering wheel angle correction.

According to the second and eighth aspects of the present invention, the amount of correction per unit time by the correction means is reduced in accordance with an increase in vehicle speed. The steering angle correction is performed by the amount, and it is possible to more reliably prevent the operator from feeling uncomfortable. In addition, steering wheel angle correction is performed efficiently.

According to the third and eighth aspects of the present invention, since the duty control valve is used as the correction means, the correction amount per unit time can be easily changed by changing the duty value.

According to the fourth and eighth aspects of the present invention, an electromagnetic switching valve, which is less expensive than a duty valve, can be used as the correction means, so that the manufacturing cost of the entire apparatus can be reduced.

According to the fifth, sixth and eighth aspects of the present invention, the opening can be more reliably adjusted to the predetermined degree as compared with the case where the duty valve is used as the correcting means. According to the seventh and eighth aspects of the present invention, the actual position of the steering wheel is corrected to the target position obtained from the steering angle of the steering wheel based on the relative angle of the steering wheel. Is 360 degrees or more, a correction amount of less than 360 degrees which is smaller by one or two rotations is sufficient, and idling of the steering wheel required for steering wheel position correction can be relatively reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart of a knob position correction control process according to a first embodiment.

FIG. 2 is a flowchart of an interrupt routine.

FIG. 3 is a schematic diagram of a power steering device.

FIG. 4 is a block diagram showing an electrical configuration of the steering wheel angle correction device.

FIG. 5 is a time chart of an output signal from a rotary encoder.

FIG. 6 is a partial schematic view of a disk constituting the rotary encoder.

FIG. 7 is an explanatory diagram of knob position correction control.

FIG. 8 is a graph showing a map for setting a correction amount.

FIG. 9 is a graph showing a target position setting map.

FIG. 10 is a graph showing a map for setting a correction amount according to the second embodiment;

FIG. 11 is a graph showing the relationship between the valve opening and the on-time.

FIG. 12 is a graph showing a map for setting a correction amount according to the third embodiment;

FIG. 13 is a graph showing a map for setting a correction amount according to the fourth embodiment;

FIG. 14 is a schematic diagram of the power steering device.

FIG. 15 is an explanatory diagram of knob position correction control according to the fifth embodiment.

FIG. 16 is a schematic view of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power steering device, 2 ... Handle, 4 ... Orbit roll which comprises drive means and hydraulic oil supply means,
6: Hydraulic pump, 8: Drain tank, 12: Steering cylinder as actuator constituting drive means, 19: Steering wheel, 21: Bypass line as pipeline, 22: Electromagnetic switching as duty valve as correction means Valves: 27: Rotary encoder constituting steering wheel angle detecting means, 28: Potentiometer as steering angle detecting means, 35: Vehicle speed sensor as vehicle speed detecting means, 37
... Edge detection circuit constituting steering wheel angle detection means, 40
.., A driving circuit constituting control means, 41, a CPU as control means and target position calculating means, 44, a steering angle counter, constituting steering wheel angle detecting means, F, a forklift as a vehicle.

Claims (8)

[Claims] An all-hydraulic power steering device is provided, and when the positional relationship between the steering wheel angle and the steering angle of the steered wheels is deviated by a predetermined amount or more, the deviation is caused by idling the steering wheel when operating the steering wheel. An industrial vehicle provided with a steering angle correcting means for correcting the steering angle, wherein the correction amount per unit time by the steering wheel angle correcting means is made smaller at high speed running than at low speed running. 2. A driving means for driving a steering wheel to an angle of steering according to an operation position of a steering wheel, a steering wheel angle detecting means for detecting an actual position of the steering wheel, and a steering angle for detecting an angle of steering of the steering wheel. Detecting means; target position calculating means for calculating a target position from the turning angle; correcting means for reducing a change ratio of a driving amount of the driving means with respect to an operation amount of the steering wheel; vehicle speed detecting means for detecting a vehicle speed; The driving of the correcting means is controlled so that a deviation amount between the actual position of the steering wheel and the target position is at least within an allowable range, and a correction amount per unit time of the correcting means is reduced in accordance with an increase in vehicle speed. Angle correction device for an industrial vehicle, comprising a control means for controlling the steering angle. 3. The hydraulic motor according to claim 1, wherein the driving unit is a hydraulic oil supply unit that discharges hydraulic oil in an amount corresponding to an operation amount of the steering wheel, and is driven by the hydraulic oil from the hydraulic oil supply unit to drive the steered wheels. And a hydraulic actuator for performing the operation, wherein the correction means is connected to a pipe line which can return a part of the hydraulic oil discharged from the hydraulic oil supply means to the drain tank before being supplied to the actuator. The steering angle correction device for an industrial vehicle according to claim 2, further comprising a duty control valve provided, wherein the control means changes a duty of the duty control valve in accordance with a vehicle speed. 4. An on / off solenoid valve is used in place of said duty valve, and said control means changes the time for which said on / off solenoid valve is kept open in accordance with vehicle speed. 4. The steering angle correction device for an industrial vehicle according to 3. 5. The steering angle correction of an industrial vehicle according to claim 3, wherein a proportional valve is used in place of said duty valve, and said control means changes an opening degree of said proportional valve in accordance with a vehicle speed. apparatus. 6. A variable throttle valve and an electromagnetic switching valve are provided in the pipeline in place of the duty valve, and the control means changes an opening degree of the variable throttle valve in accordance with a vehicle speed. 3. The steering angle correction device for an industrial vehicle according to claim 1. 7. The control means includes target position calculation means for calculating the target position from the steering angle detected by the steering angle detection means as a relative angle of a steering wheel. The handle of an industrial vehicle according to any one of claims 2 to 6, wherein the position of the handle is corrected so that a deviation amount between the actual position and the target position detected in step (b) falls within an allowable value in a relative angle. Angle correction device. 8. An industrial vehicle comprising the steering wheel angle correction device according to claim 1.