JPH0624700A - Controller for fork lift truck - Google Patents

Abstract

PURPOSE:To automatically lower a fork and stop it at a specified position only by operating an automatic switch by taking a means to store the position of the fork detected by a lift height sensor as a stop position, when a lift lowering position memory switch turned on. CONSTITUTION:A controller 10 inputs the level operation signal S1 caused by the tilt of an operation lever 9a and outputs the flow control signal S2 in compliance with the signal S1. As a result, since pressure oil is supplied from an electromagnetic proportional control valve 11 and discharged to a lift cylinder 1, a fork is lifted. At this moment, the height of the fork is detected by a lift height sensor 25, and the height of the fork when a lift lowering position memory switch SW is turned on is also stored as a fork stop position. When an automatic switch SW1 is turned on, and the fork is lowered and reaches the stop position, the fork stops automatically. On the other hand, the weight of a load is detected by an oil pressure sensor 17, and the heavier the load is, the earlier speed reduction starts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forklift control device capable of operating a cargo handling operation by an electromagnetic hydraulic system, in which a fork is lowered and automatically stopped at a preset position.

[0002]

2. Description of the Related Art Conventionally, as a control device for a forklift that can be operated electromagnetically, for example, the one shown in FIG. 11 is known (Japanese Utility Model Laid-Open No. 60-107405). As shown in the figure, the pressure oil from the hydraulic pump 01 is divided into an electromagnetic proportional control valve 02 and a power steering control valve (not shown) via a conduit 07. An oil chamber 02a for pilot operation is formed in the electromagnetic proportional control valve 02, and a pilot piston 02b is slidably fitted in the oil chamber 02a. This pilot piston 02
b is connected to a spool 02c for switching the oil passage. The pilot piston 02b and the spool 02c are connected to the springs 03a and 03b, respectively, and are held at a neutral position without hydraulic pressure. Pilot inflow conduits 02d and 02e are provided on both sides of the pilot piston 02b.
Are provided respectively. Pilot inflow line 02
d and 02e are connected to a hydraulic system for power steering via electromagnetic opening / closing valves 02f and 02g. Therefore, the pilot piston 02b and the spool 02c move left and right in the figure by opening and closing the electromagnetic opening / closing valves 02f and 02g. When the spool 02c moves, this spool 0
Pressure oil is supplied to and discharged from the working machine cylinder 04 via 2c, and the working machine cylinder 04 expands and contracts. The flow rate of the pressure oil supplied to and discharged from the working machine cylinder 04 is adjusted by the moving position of the spool 02c, and the ascending / descending speed thereof is adjusted. As the working machine cylinder 04, various ones such as one for raising and lowering a fork (not shown) and one for tilting it can be used.

On the other hand, the opening / closing of the solenoid opening / closing valves 02f and 02g is controlled by a flow rate control signal from the controller 05. The controller 05 outputs a flow rate control signal in response to a lever operation signal from the work implement lever 06. The work implement lever 06 includes a potentiometer and outputs a lever operation signal according to the tilt angle and the tilt direction. The work implement lever 06 does not output at the neutral position. Therefore,
By operating the work equipment lever 06, the solenoid opening / closing valve 02
By opening and closing f and 02g, pressure oil is supplied to and discharged from the work machine cylinder 04 from the electromagnetic proportional control valve 02, the work machine cylinder 04 expands and contracts to elevate and tilt the fork, and the tilt angle of the work machine lever 06. Adjustment, work machine cylinder 0
The flow rate of the pressure oil to 4 can be adjusted to freely control the ascending / descending speed and the like.

[0004]

When carrying out cargo handling work with a forklift, the operator operates the work implement lever 06 to lift or lower each load. Among such cargo handling work, there is a work of repeatedly lifting many loads to the same height. Conventionally, even if the lifting height is the same, the operator has to tilt the work machine lever 06 in the same manner every time when carrying down each load. Therefore, the operator has to perform exactly the same operation many times, and the shoulder may be sore that the operator is easily tired, and the work efficiency may be reduced.

In view of the above-mentioned prior art, the present invention provides a control device for a forklift in which a stop position is set in advance, and when the automatic switch is pressed thereafter, the fork descends and the fork automatically stops when the stop position is reached. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION The structure of the present invention for solving the above-mentioned problems includes a working machine lever for outputting a lever operation signal having a value corresponding to an inclination angle, and a flow rate control having a value corresponding to the value of the lever operation signal. A controller that outputs a signal, an electromagnetic proportional control valve that supplies and discharges pressure oil according to the value of the flow rate control signal, and a lift cylinder that expands and contracts by expanding and contracting the pressure oil by the electromagnetic proportional control valve. In the forklift having, an automatic switch, a lift lowering position memory switch, a lift sensor for detecting the height of the fork, and a hydraulic sensor for detecting the pressure of pressure oil sent to the lift cylinder, wherein the controller is When the lift down position memory switch is turned on, the position of the fork detected by the lift sensor is stored as a stop position, and when the pressure detected by the hydraulic sensor becomes higher, Set the deceleration start position so that the interval between the deceleration start position and the stop position, which is set above the stop position, is long.When the automatic switch is turned on, the fork automatically descends, and when the fork passes the deceleration start position, it descends. It is characterized by controlling the value of the flow control signal so that the speed is gradually reduced and the fork is stopped when it reaches the stop position.

[0007]

Operation: When the automatic switch is turned on, the fork automatically descends, and when the fork reaches the stop position, the fork automatically stops. The fork starts deceleration at a position before the stop position. The interval between the deceleration start position and the stop position is longer as the load is heavier and the fork lowering speed is faster.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. 1 to 10 show an embodiment of the present invention. FIG. 3 is a perspective view showing an example of a forklift truck applied to this embodiment. As shown in the figure, the lift cylinder 1 is fixed to the pair of left and right outer masts 2,
With the expansion and contraction of the piston rod 1a, the pair of left and right inner masts 3 are moved up and down using the outer mast 2 as a guide. At this time, the outer mast 2 is fixed to the vehicle body 7 in front of the vehicle body 7. As a result, as the inner mast 3 moves up and down, the up-and-down unit composed of the bracket 5 suspended on the chain and the fork 4 for directly loading luggage is moved up and down. The tilt cylinder 8 is for tilting the elevating part together with the outer mast 2 and the inner mast 3 forward (opposite the vehicle body 7) and backward (on the vehicle body 7 side). That is, in the case of unloading, it tilts forward and in the case of loading and tilting backward when carrying a load, each workability is kept good and safety is secured.

The working machine levers 9a and 9b control the operations of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11 when the operator operates them, and an emergency stop is performed. It is housed in a joystick box 13 together with a safety switch 12 for performing. An automatic switch SW1 is provided on the top of the work machine lever 9a (see FIG. 1). Further, the joystick box 13 is provided with a lift position storage switch SW2 and a lift position storage switch SW3. The work machine levers 9c, 9d, 9e are provided for handling various attachments such as roll clamps and bale clamps. The seat switch 14 is a switch that operates when an operator sits in the driver's seat 15, and the output signal thereof is output to the controller 10.

FIG. 1 is a block diagram showing an example of the control device for the forklift. As shown in the figure, the working machine lever 9a is formed by a potentiometer and sends a lever operation signal S ₁ whose current value is proportional to the operation amount to the controller 10. The controller 10 sends out a flow rate control signal S ₂ for adjusting the opening degree of the spool of the electromagnetic proportional control valve 11 based on the lever operation signal S ₁ . Electromagnetic proportional control valve 1
1 moves the spool in proportion to the magnitude of the flow rate control signal S ₂ to control the flow rate of the pressure oil flowing through the hydraulic line 16 so that the operating speed of the lift cylinder 1 corresponds to the operation amount of the working machine lever 9a. Control to do. Further, the lift cylinder 1 is provided with a take-up type lift sensor 25 for detecting the height of the fork 4, and the lift sensor 25 sends a lift signal S ₄ to the controller 10.

The hydraulic sensor 17 is arranged in the hydraulic line 16 and sends out a hydraulic signal S ₃ representing the hydraulic pressure in the hydraulic line 16. The controller 10 processes the hydraulic signal S ₃ to calculate the load applied to the lift cylinder 1. Furthermore,
The controller 10 operates by being supplied with power from the battery 21 by turning on the starter switch 20 housed in the console box 19 together with the warning light 18, and when the safety switch 12 is operated and the seat switch 14 does not operate. Flow rate control signal S ₂ when seated
The current value of is set to zero and the opening of the electromagnetic proportional control valve 11 is controlled to be zero.

The hydraulic pump 22 operates by being connected to the engine of the fork and sends the oil of the hydraulic oil source 23 to the electromagnetic proportional control valve 11. Therefore, the pressure of the pressure oil sent from the electromagnetic proportional control valve 11 to the lift cylinder 1 depends on the value of the flow rate control signal S ₂ that determines the opening of the solenoid valve and the engine speed that determines the discharge hydraulic pressure from the hydraulic pump 22. Correspond. The engine speed is detected by the engine speed sensor 26, and the engine speed signal S ₅ is output from the sensor 26 by the controller 1.
Sent to 0.

Here, the controller 10 is mainly used.
The automatic stop control will be described with reference to FIG. Con
The CPU 120 of the trolley 10 has a clock generator 121.
It performs various arithmetic processing in synchronization with the clock of
Calculation using the software stored in the memory 122
To process. On the other hand, the lever output from the work machine lever 9a
-Operation signal S ₁, Hydraulic pressure output from the hydraulic pressure sensor 17
Issue S₃, Lift signal S output from lift sensor 25_Four，
Engine speed output from the engine speed sensor 26
Number signal S_FiveIs digitalized by the A / D converter 123.
After being converted into a signal, it is sent to the CPU 120. Automatic scan
Switch SW1 (This is provided on the top of the work equipment lever 9a.
Switch signal P from₁， Position memory switch
SW2, SW3 (This is the joystick box 13
Equipped with a switch signal P from₂, P ₃Is
Sent to the CPU 120 via the interface 124
It Flow control signal S₂Is based on the control of the CPU 120.
The solenoid valve drive circuit 125 to the solenoid proportional control valve 11.
To be

First, an outline of the operation of automatically stopping the fork 4 when it is raised will be described. First, in order to determine the position at which the fork 4 is stopped, the working machine lever 9a is tilted to the upside, and when the fork 4 moves up to the desired position, the working machine lever 9a is returned to the neutral position and the fork 4 is stopped. At this time, when the lift-up position storage switch SW2 is turned on, a lift signal S ₄ indicating the height of the fork 4 at this time is fetched, and the height of the fork 4 at this time is stored in the memory 122 as a stop position.

After the above preset is completed, the actual work is started. When the fork 4 is below the stop position, the working machine lever 9a is pushed while pushing the automatic switch SW1.
If the operator pulls the hand up, the operator releases the hand and the automatic switch SW1 opens, and the work machine lever 9a returns to the neutral position, but the fork 4 continues to rise and the fork 4 stops when the fork 4 reaches the stop position. A flow rate control signal S ₂ that causes the electromagnetic proportional control valve 1 from the controller 10
Sent to 1. Thus, the fork 4 automatically rises,
It stops at a predetermined stop position.

In the case of automatically raising and stopping automatically in this way, the ascending speed of the fork 4 is gradually reduced from the position before the stop position to stop the shock at the stop position, and the fork 4 stops at the stop position. I am trying to let you. Therefore, the characteristics shown in FIG. 4 and the characteristics shown in FIG. 5 are stored in the memory 122, and the CPU 120 issues a command to automatically raise / stop using both characteristics.

For example, when the stop position is H ₁ (see FIG. 6) and the engine speed is N ₁ , l ₁ is obtained as the raising / stopping braking distance and V ₁ is obtained as the deceleration value. Then, as shown in FIG. 6, when the fork 4 reaches the position of H ₁ −l ₁ , the ascending speed starts to decelerate, and the ascending speed of the fork 4 is reduced by V _{1 at} every predetermined time. When reaching H ₁ , the fork 4 is stopped.

The characteristics shown in FIGS. 4 and 5 are that when the engine speed is high and the ascending speed of the fork 4 is fast, the braking distance is increased and the deceleration value is decreased to prevent the occurrence of shock. When the ascending speed of the fork is low, the braking distance is shortened and the deceleration value is increased so that the fork is quickly stopped.

Next, an outline of the operation of automatically stopping the fork 4 when lowering it will be described. First, in order to determine the position where the fork 4 is stopped, the working machine lever 9a is tilted to the lower side, and when the fork 4 comes down and reaches the target position, the working machine lever 9a is returned to the neutral position and the fork 4 is stopped. At this time, when the lift lowering position storage switch SW3 is turned on, the lift signal S ₄ indicating the height of the fork 4 at this time is fetched, and the height of the fork 4 at this time is stored in the memory 122 as the stop position.

After the above preset is completed, the actual work is started. When the fork 4 is above the stop position, the working machine lever 9a is pushed while pressing the automatic switch SW1.
If the operator releases the hand and the automatic switch SW1 opens and the working machine lever 9a returns to the neutral position, the fork 4 continues to descend and the fork 4 is stopped when the fork 4 reaches the stop position. A flow rate control signal S ₂ that causes the electromagnetic proportional control valve 1 from the controller 10
Sent to 1. Thus, the fork 4 descends automatically,
It stops at a predetermined stop position.

In the case of automatically descending and stopping automatically in this way, the descent speed of the fork 4 is gradually reduced from the position before the stop position to stop the shock after the stop, and the fork 4 is stopped at the stop position. I am trying to let you. Therefore, the characteristics shown in FIG. 7 and the characteristics shown in FIG. 8 are stored in the memory 122, and the CPU 120 issues a command to automatically lower and stop using both characteristics.

For example, when the stop position is H ₂ (see FIG. 9) and the load is W ₁ (which is obtained from the hydraulic signal S ₃ ), l ₂ is obtained as the down-stop braking distance and V ₂ is obtained as the deceleration value. . Then, as shown in FIG. 9, when the fork 4 arrives at the position of H ₂ + l ₂ , the descending speed starts decelerating, and the descending speed of the fork 4 is reduced by V _{2 at} every predetermined time. _When it reaches ₂ , the fork 4 is stopped.

The characteristics of FIGS. 7 and 8 are that when the load is heavy and the descending speed of the fork 4 is fast, the braking distance is lengthened to reduce the deceleration value to prevent the occurrence of shock, and the load is light and the fork descends. When the speed is slow, the braking distance is shortened and the deceleration value is increased so that the vehicle can be stopped quickly.

Next, the command operation of the controller 10 will be described in detail with reference to FIG. It should be noted that each operation step is denoted by a symbol “ST”. After the control is started and the initialization is performed (ST1, ST2), when the lift-up position storage switch SW2 is turned on (ST3), the signal of the lift sensor 25 is taken into the controller 10 and the position of the fork 4 at this time is changed. It is stored as the raised position (S
T4). On the other hand, when the lift lowering position storage switch SW3 is turned on (ST5), the signal of the lift sensor 25 is taken into the controller 10 and the position of the fork 4 at this time is stored as the lowering position (ST6).

At step (ST7), the working machine lever 9
Whether the lift is lifted, lifted down, or lifted is determined by the closing direction of a, that is, the polarity of the lever operation signal S ₁ . When it is determined that the lift raising, rather than raising control mode (ST8), when the automatic switch SW1 is not turned on (ST9) outputs a flow control signal S ₂ in response to the lever operation signals S ₁ Lift Raise control (ST1
0).

Automatic match SW1 in step (ST9)
When is input, in step (ST11), the raising control mode is set, the deceleration start position and deceleration value are calculated using the characteristics of FIGS. 4 and 5, and the flow control signal S ₂ The value corresponds to the value of the lever operation signal S ₁ .

After it is determined to be the raising control in step (ST8), if the deceleration mode is not entered (ST12) and the lift does not reach the deceleration position (ST13), the ascent continues. When the lift becomes higher than the deceleration position in step (ST13), the deceleration mode is set (ST1).
4).

When the deceleration mode is set (ST12,
ST14), the value of the flow rate control signal S ₂ (output values) becomes minus deceleration value from the previous value (ST15). This calculation is performed every control cycle. When the output value is larger than the stop value (ST16), this operation control cycle is repeated and the fork is decelerated and raised. When the output value becomes smaller than the stop value (ST16), the raising control mode and the deceleration mode are cleared (ST17), and the fork is stopped.

When it is determined in step (ST7) that the lift is to be lowered, it is not in the lowering control mode (ST18),
When the automatic switch SW1 is not turned on (ST1
9) shows the flow control signal S corresponding to the lever operation signal S _1.
2 is output to perform lift lowering control (ST20).

At step (ST19), the automatic switch S
When W1 is turned on, the lowering control mode is set in step (SW21), the deceleration start position and deceleration value are calculated using the characteristics of FIGS. 7 and 8, and the flow rate control signal S ₂ The value of corresponds to the value of the lever operation signal S ₁ .

After it is determined in step (ST18) that the control is the down control, if the deceleration mode is not entered (ST22) and the lift does not reach the deceleration position (ST23), the descent continues. When the elevation becomes lower than the deceleration position in step (ST23), the deceleration mode is set (ST2
4).

When the deceleration mode is set (ST22,
ST24), the value of the flow rate control signal S ₂ (output values) becomes minus deceleration value from the previous value (ST25). This calculation is performed every control cycle. When the output value is larger than the stop value (ST26), this calculation control cycle is repeated and the fork is decelerated and raised. When the output value becomes smaller than the stop value (ST26), the lowering control mode and the deceleration mode are cleared (ST27), and the fork is stopped.

[0033]

As described above in detail with the embodiments, according to the present invention, the stop position of the fork can be set to an arbitrary height, and when the fork is lowered, the fork is moved by turning on the automatic switch. It automatically descends and stops automatically when it reaches the stop position, so even if you carry down many loads to the same height many times, you can carry out the work with a simple operation of turning on the automatic switch. it can. Thus, the operator's feeling of fatigue is reduced.

Further, since the descending speed of the fork is gradually reduced from the position before the stop position, the fork can be stopped without shock. Moreover, the weight of the load is calculated from the pressure of the pressure oil, and the heavier and faster the descending speed is, the earlier the deceleration of the fork is started, so that the fork can be smoothly stopped.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a perspective view showing a forklift to which the present invention is applied.

FIG. 4 is a characteristic diagram showing a relationship between an engine speed and a raising / stopping braking distance.

FIG. 5 is a characteristic diagram showing a relationship between an engine speed and a deceleration value.

FIG. 6 is a characteristic diagram showing a state in which a fork is lifted / stopped.

FIG. 7 is a characteristic diagram showing a relationship between a load and a down-stop braking distance.

FIG. 8 is a characteristic diagram showing a relationship between a load and a deceleration value.

FIG. 9 is a characteristic diagram showing a state in which the fork is lowered and stopped.

FIG. 10 is a flowchart showing the operation of the present invention.

FIG. 11 is a hydraulic circuit showing a conventional control device for an electromagnetic hydraulic forklift.

[Explanation of symbols]

1 Lift Cylinder 1a Piston Rod 4 Fork 9a Working Machine Lever 10 Controller 11 Electromagnetic Proportional Control Valve 16 Hydraulic Pipeline 17 Hydraulic Pressure Sensor 24 Automatic Lowering Switch 25 Lifting Height Sensor 26 Engine Speed Sensor 120 CPU S ₁ Lever Operation Signal S ₂ Flow Control Signal S ₃ Oil pressure signal S ₄ Lifting signal S ₅ Engine speed signal SW 1 Automatic switch SW 2 Lift up position memory switch SW 3 Lift down position memory switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Matsuda 3000 Tana, Sagamihara-shi, Kanagawa Mitsubishi Heavy Industries, Ltd. Sagamihara Works (72) Inventor Toshiyuki Midorikawa 3000, Tana, Sagamihara, Kanagawa Eye Sagami High Tech Co., Ltd.

Claims (1)

[Claims] 1. A work implement lever that outputs a lever operation signal having a value corresponding to a tilt angle, a controller that outputs a flow rate control signal having a value corresponding to the value of the lever operation signal, and a flow control signal corresponding to the value of the flow rate control signal. An electromagnetic proportional control valve that supplies and discharges a certain amount of pressure oil,
An automatic switch, a lift lowering position memory switch, and a lift height sensor that detects the height of the fork, in a forklift that has a lift cylinder that lifts and lowers the fork by expanding and contracting with pressure oil supplied and discharged by an electromagnetic proportional control valve. , A hydraulic pressure sensor for detecting the pressure of the pressure oil sent to the lift cylinder, the controller stores the position of the fork detected by the lift sensor when the lift lowering position memory switch is turned on as a stop position, and further stores the hydraulic pressure. When the pressure detected by the sensor becomes higher, the deceleration start position is set so that the interval between the deceleration start position set above the stop position and the stop position is lengthened, and when the automatic switch is turned on, the fork is automatically lowered. When the fork passes the deceleration start position, the descending speed is gradually reduced, and when the fork reaches the stop position, the fork is stopped. Manner, the control device for a forklift characterized in that to control the value of the flow rate control signal.