JPH05229792A - Hydraulic controller for tilt cylinder in forklift - Google Patents

Abstract

PURPOSE:To improve the operation property of a tilt lever and prevent a load collapse by controlling the opening of a control valve, based on the operation amount of an operation means, by an opening order value in response to the weight of a load so as to control the slanting of a fork. CONSTITUTION:A tilt cylinder 11 slanting the fork 7 on a forklift, a pressure sensor 12 detecting the weight of a load which is brought up by the fork 7, a lever operation amount detection sensor 9 detecting the operation amount of a tilt lever 8 for setting the extension/contraction speed of the tilt cylinder 11 and a control valve 10 for adjusting the flow rate of an operation oil in the tilt cylinder 11 and the slanting speed of the fork 7 are arranged. The opening order value for controlling the opening of the control valve per the weight of a load is memorized in a memory 17 and the opening of the control valve 10 is controlled by the opening order value in response to the operation amount of the tilt lever 8 and the slanting control of the fork 7 is performed by a controller 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a tilt cylinder in a forklift.

[0002]

2. Description of the Related Art Conventionally, when a tilt cylinder of a forklift is operated to perform a tilting motion of a mast (hereinafter, referred to as a fork for convenience of description), a front tilting motion and a rear tilting motion are performed as shown in FIGS. The tilting speed is determined based on the operation direction of the tilt lever 51, and the tilting speed is determined by the tilt lever 5
It is set by the lever operation angle (operation amount) θ of 1. That is, the electromagnetic proportional control valve 52 is switched based on the operation direction of the tilt lever 51, and the tilt cylinder 5 is switched.
Changing the supply direction of the hydraulic oil supplied to the fork 54
Tilting motion. The tilting speed of the fork 54 is controlled by adjusting the supply of hydraulic oil to the electromagnetic proportional control valve 52 based on the operation angle (operation amount) θ of the tilt lever 51. The operation force of the tilt lever 51 linearly increases based on the operation angle θ of the tilt lever 51.

The tilt speed control of the fork 54 will be described in detail. The lever operation angle θ of the tilt lever 51 is detected by a lever operation detection sensor 55, which is a potentiometer, and this detection signal is output to a controller 56.

The controller 56 includes an A / D converter 57, a CPU 58, a memory 59, and a D / A converter 60.
And a constant current amplifier 61. And
The detection signal from the lever operation detection sensor 55 is A / D
It is converted into a digital value by the converter 57 and the CPU 58
To the tilt lever 51 at that time.
The operation angle θ of is calculated. The CPU 58 controls the lever operation angle θ
Is calculated, the drive current value I to be applied to the electromagnetic proportional control valve 52 is calculated based on the map in which the drive current value I is set for the operation angle θ stored in the memory 59 shown in FIG. 7. The drive current value I with respect to the lever operation angle θ shown in FIG. 7 has been previously tested or logically obtained, and is stored in the memory 59 as data.

The CPU 58 outputs a drive control signal for the drive current value I to the D / A converter 60 in order to drive and control the electromagnetic proportional control valve 52 with the drive current value I, and the D / A converter 60 drives the drive control signal. The control signal is converted into analog, and the drive current value I is supplied from the constant current amplifier 61 to the electromagnetic proportional control valve 52. Electromagnetic proportional control valve 5
2 supplies the working oil to the tilt cylinder 53 in a supply or outflow amount determined by the drive current value I (that is, the lever operation angle θ). Therefore, the drive current value I is obtained based on the operation angle θ of the tilt lever 51, and the drive current value I determines the supply or discharge amount of the hydraulic oil at that time and the tilting speed. That is, the tilting speed of the fork 54 is determined by the operation angle θ of the tilt lever 51.

[0006]

By the way, when the load is being lifted by the fork 54, the higher the height of the fork 54, the slower the tilt cylinder 53 is controlled.
The tilting speed of the fork 54 needs to be slow.
In particular, when the fork 54 tilts forward,
Load of the load being lifted by the fork 54
It is necessary to slow the forward tilting motion in consideration of the height of.

However, the tilting speed of the fork 54 is determined regardless of the load of the load lifted by the fork 54 and the height of the fork 54. Therefore, the tilting speed of the fork 54 must be adjusted while finely adjusting the operation angle θ of the tilt lever 51, which causes a problem of poor operability.

Further, the operating angle θ of the tilt lever 51 is erroneously set.
When the value is increased, the tilting speed of the fork 54 becomes faster, and there is a possibility that the load falls from the fork 54 particularly in the case of the forward tilting operation.

The present invention has been made to solve the above problems, and its first object is to improve the operability of the tilt lever by adjusting the tilting speed of the fork based on the load change of the load. At the same time, another object of the present invention is to provide a hydraulic control device for a tilt cylinder in a forklift, which is capable of preventing the collapse of the load due to the tilting motion of the fork.

The second purpose is to adjust the tilting motion of the fork based on the change in the lifting height of the fork to improve the operability of the tilt lever and prevent the collapse of the load accompanying the tilting motion of the fork. It is an object of the present invention to provide a hydraulic control device for a tilt cylinder in a forklift that can be used.

A third object is to improve the operability of the tilt lever by adjusting the tilting speed of the fork based on the change in the lift of the fork and the change in the load of the load, and prevent the collapse of the load accompanying the tilting motion of the fork. It is to provide a hydraulic control device for a tilt cylinder in a forklift capable of performing.

[0012]

In order to solve the above problems, the first invention of the present application is to provide a tilt cylinder for tilting a fork of a forklift and a load for detecting a load of cargo handling lifted by the fork. Detecting means, operation amount detecting means for detecting an operation amount of the operating means for setting the expansion / contraction speed of the tilt cylinder, and a control valve for adjusting the tilting speed of the fork by adjusting the flow rate of the working oil of the tilt cylinder. A storage means for storing the opening degree command value for controlling the opening degree of the control valve for the operation amount of the operating means for each load of the cargo handling, and the load of the cargo handling at that time based on the operation amount of the operating means. Hydraulic control means for cargo handling for controlling the opening of the control valve according to the corresponding opening command value to perform tilting control of the fork As its gist further comprising a.

A second aspect of the invention is a tilt cylinder for tilting a fork of a forklift, a lift cylinder for vertically moving the fork, a lift detecting means for detecting a lift position of the fork, and an extension / contraction of the tilt cylinder. An operation amount detecting means for detecting an operation amount of the operating means for setting a speed, a control valve for adjusting a tilting speed of the fork by adjusting a flow rate of hydraulic oil of the tilt cylinder, and a lift position of the fork. The storage means for storing the opening degree command value for controlling the opening degree of the control valve with respect to the operation amount of the operation means at that time and the lift position of the fork at that time based on the operation amount of the operation means. A cargo handling hydraulic control means for controlling the opening of the control valve according to the opening command value to control the tilting of the fork. That there was example as its gist.

A third invention is a tilt cylinder for tilting a fork of a forklift, a lift cylinder for vertically moving the fork, a load detecting means for detecting a load of cargo handling lifted by the fork, and a lifting of the fork. Lifting height detection means for detecting a high position, operation amount detection means for detecting the operation amount of the operation means for setting the expansion / contraction speed of the tilt cylinder, and adjusting the flow rate of the working oil of the tilt cylinder to adjust the flow rate of the fork. A control valve for adjusting the tilting speed, a storage means for storing an opening degree command value for controlling the opening degree of the control valve with respect to the operation amount of the operation means for each of the lift position of the lift cylinder and the load of the cargo handling; Based on the operation amount of the means, the opening position finger corresponding to the lift position of the fork and the load of the cargo at that time. Values by the gist that a hydraulic control unit for cargo handling to be opening control performed the tilting control of the fork the control valve.

[0015]

The cargo handling hydraulic control means reads out the opening degree command value corresponding to each load of the cargo handling with respect to the operation amount of the operating means at that time from the storage means. Based on the opening command value read from the storage means, the cargo handling hydraulic control means controls the opening of the control valve to perform the expansion / contraction control of the tilt cylinder and the tilting operation of the fork.

Further, the cargo handling hydraulic control means reads from the storage means an opening degree instruction value corresponding to the lift position of the fork at that time with respect to the operation amount of the operation means at that time. Based on the opening command value read from the storage means, the cargo handling hydraulic control means controls the opening of the control valve to control the expansion and contraction of the tilt cylinder, and performs the tilting operation of the fork.

Further, the cargo handling hydraulic control means reads out from the storage means an opening degree command value corresponding to the lift position at that time and the load of the cargo handling with respect to the operation amount of the operating means at that time.
Based on the opening command value read from the storage means, the cargo handling hydraulic control means controls the opening degree of the control valve to perform the expansion / contraction control of the tilt cylinder and the tilting control of the fork.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of tilt control of a tilt cylinder in a forklift will be described below with reference to FIGS.

As shown in FIG. 1, a lift lever 1 is provided in the driver's seat of the forklift. And
The operation direction and operation angle θ of the lift lever 1 are detected by a lever operation amount detection sensor (for example, a potentiometer) 2 and output to a controller 3 as a cargo handling hydraulic control means. The controller 3 controls the opening of the control valve 4 to adjust the flow rate of hydraulic oil. The adjusted hydraulic oil is supplied to the lift cylinder 6 provided on the mast 5, and the lift cylinder 6 is vertically controlled. The lifting speed of the fork 7 is controlled by the lifting control of the lift cylinder 6.

Further, the forklift is provided with a tilt lever 8 in its driver's seat. Then, the operation direction and the operation angle (operation amount) θ of the tilt lever 8 are detected by a lever operation amount detection sensor (for example, a potentiometer) 9 as an operation amount detection means and output to the controller 3. The controller 3 controls the opening of the control valve 10 to adjust the flow rate of hydraulic oil. The adjusted hydraulic oil is supplied to the tilt cylinder 11, so that the mast 5 is tilted and controlled. The tilting speed of the fork 7 is controlled by the tilting control of the mast 5.

That is, the controller 3 controls the tilting of the fork 7 based on the operation direction and the operation angle θ of the tilt lever 8. When the operation angle θ of the tilt lever 8 is in the range from the neutral position to the reference operation angle θ1 or from the neutral position to the reference operation angle −θ1, a dead zone that does not operate the tilt cylinder 11 is provided, and the operation angle θ of the lift lever 1 is set. When the reference operating angle is ± θ1 or more, the opening of the control valve 10 is controlled by the controller 3 based on the operating angle θ, and the tilting control of the fork 7 is performed. Further, when the tilt lever 8 becomes equal to or larger than the predetermined operation angle ± θn, the controller 3 controls the control valve 10 to a constant opening regardless of the operation angle θ to supply a constant amount of hydraulic oil to the tilt cylinder 1.
1, and the tilting of the fork 7 is controlled at a constant speed.

A pressure sensor 12 as a load detecting means is provided below the mast 5, and the pressure sensor 12 detects the load of the cargo handling lifted by the fork 7. A lift sensor 13 as lift detection means is provided on the upper side surface of the mast 5, and the lift sensor 13 detects the lift position of the fork 7.

The working oil is supplied to the control valve 4 by an oil pump 15 which is rotated by the drive of the engine 14, and the working oil flowing out from the drain of the control valve 4 is supplied to the control valve 10. There is.

The controller 3 stores an A / D converter 16 for converting an input detection signal into a digital signal, temporarily stores a calculation result, stores a work program and various data, and uses the tilt lever 8 as a reference. A memory 17 as a storage means for storing a drive current value (opening command value) I for expanding and contracting the tilt cylinder 11 when the operation angle is ± θ1 or more, and maps MA, MB described later,
CPU 18 for performing arithmetic processing based on the input signal, various data in the memory 17 and a work program, the CPU 1
8 is composed of a D / A converter 19 for converting the command signal from 8 into an analog signal and a constant current amplifier 20 for outputting an output signal to the control valves 4, 10 based on the command signal.

The A / D converter 16 includes lever operation amount detection sensors 2 and 9, a pressure sensor 12, and a lift sensor 1.
The detection signal from 3 is input, this detection signal is converted into a digital signal and output to the CPU 18.

As shown in FIGS. 3 and 4, the memory 17
A map MA for storing a set drive current value based on the lifted position of the fork 7 is stored for each load of the cargo lifted by the fork 7. This map MA
Is the set drive current value IM when the lift position of the fork 7 is the minimum and there is no cargo handling, and the set drive current value IL when the lift position of the fork 7 is the minimum and the cargo handling is large (allowable maximum load). (<IM) is set.

When the lift position of the fork 7 is maximum, the set drive current value IN (<IL
) Is set. In addition, this map M
The inclination of A and the levels of the set drive current values IM, IL and IN are based on the data obtained by experimentally controlling the opening of the control valve 10. Therefore, the set drive current value is arbitrarily changed based on the load of the cargo handling lifted by the fork 7 and the lift position of the fork 7.

Further, the tilt lever 8 is provided in the memory 17.
Map M for setting the drive current value I based on the operation angle θ of
B is stored. This map MB is selected as follows. That is, the set drive current value set based on the map MA is associated with the drive current value I. At this time, when the tilt lever 8 is set to a predetermined operation angle ± θn or more in the map MB, the map MB in which the set drive current value and the drive current value I match is selected.

When the map MB is selected, the drive current value I based on the operation angle θ of the tilt lever 8 at that time is set based on the map MB. That is, when the operation angle θ of the tilt lever 8 is the neutral position to the reference operation angle −θ1 or the neutral position to the reference operation angle θ1, the drive current value I is set to 0. When the operation angle θ is the reference operation angle −θ1 to the predetermined operation angle −θn or the reference operation angle θ1 to the predetermined operation angle θn, the drive current value I based on the selected map MB is set. ing. Further, when the operation angle θ is ± θn or more, the maximum drive current value I based on the selected map MB is set regardless of the operation angle θ.

For example, when the lift position of the fork 7 is the lowest and there is no cargo handling, the set drive current value I is set based on the map MA.
M is set. This set drive current value IM is used to map MB
When the operation angle θ of the tilt lever 8 is equal to or larger than a predetermined operation angle ± θn, the drive current value I
The map MM that matches M is selected. Therefore, when the tilt lever 8 is operated, the drive current value I corresponding to the operation angle θ at that time is set based on the selected map MM.

Further, the drive current value I set as described above
Is read by the CPU 18, and the CPU 18 calculates a duty ratio based on the drive current value I and outputs the duty ratio to the constant current amplifier 20 via the D / A converter 19. The constant current amplifier 20 outputs a drive current based on the duty ratio to the control valve 10 to energize the electromagnetic proportional solenoids 10a and 10b of the control valve 10.

The electromagnetic proportional solenoids 10a and 10b of the control valve 10 are controlled by a control valve 41, which will be described later, according to the average drive current of the duty-controlled drive currents.
The opening degree of a and 41b is controlled. Therefore,
Since the drive current output from the constant current amplifier 20 increases proportionally with the passage of time, the control valves 41a, 41
The opening amount of b gradually increases, and eventually the control valve 10 supplies the working oil to the tilt cylinder 11. Then, the tilt cylinder 11 expands and contracts to start the tilting motion of the fork 7.

Next, the hydraulic circuits of the control valves 4 and 10 will be described in detail. As shown in FIG. 2, hydraulic oil supplied from the oil pump 15 is supplied to the control valve 4 by a supply pipe 21 and a diversion valve 22 via a main pipe 23 on the control valve 4 side. Further, a PS pipe line 25 for power steering is provided in the flow dividing valve 22 via a check valve 24. The main pipeline 23 is connected to the supply pipeline 33 connected to the control valve 4 via the check valve 32.

A spool 26 is arranged in the control valve 4, and pilot operation oil chambers 27 are formed at both ends thereof. This oil chamber 2
7, the spool 26 is slidable.
A spring 28 is provided in the hydraulic chamber 27, and the spring 28 always holds the spool 26 in the neutral position.

An electromagnetic proportional solenoid 4 is provided in the oil chamber 27.
control valves 29a, 2 whose opening and closing are controlled by a, 4b
9b is connected. Therefore, the constant current amplifier 20
Thus, the control valves 29a and 29b are controlled to be opened / closed via the electromagnetic proportional solenoids 4a and 4b.
Then, the flow rate of the hydraulic oil supplied to the control valves 29a, 29b is adjusted by the opening / closing control of the control valves 29a, 29b to be supplied to the oil chamber 27.

A pilot drain pipe 30 is connected to each of the oil chambers 27 and is led out to a tank or a return pipe line. The pilot drain pipes 30 flow out from the oil chambers 27. A throttle valve (orifice) 31 that regulates the outflow amount of hydraulic oil is provided.

That is, the control valve 4 controls the opening and closing of the control valves 29a and 29b based on the energization of the electromagnetic proportional solenoids 4a and 4b for raising or lowering, and the working oil is introduced into the oil chamber 27 while the inside of the oil chamber 27 is closed. Of the working oil is discharged at a flow rate limited by the throttle valve 31 of the pilot drain pipe 30 to control the magnitude of the working oil pressure acting on the spool 26.
The spool 26 is displaced to a position in which the forces of are balanced.

Therefore, the control valves 29a, 29 are controlled based on the drive currents supplied to the electromagnetic proportional solenoids 4a, 4b.
By controlling the opening degree of b, the position of the spool 26 corresponding thereto can be obtained, and the lift cylinder 6 is supplied or discharged with an amount of hydraulic oil corresponding to the position of the spool 26. That is, the lift cylinder 6 is the spool 2
It is designed to rise at a speed corresponding to the position of 6.

The working oil discharged from the control valve 4 is supplied to the control valve 10 through the main pipe line 35. The control valve 10 is connected to a supply conduit 37, and the supply conduit 37 is connected to the main conduit 23 via a check valve 36.

Inside the control valve 10, spools 39 each having a pilot operating valve 38 are arranged, and oil chambers 4 for pilot operation are provided at both ends thereof.
0 is formed respectively. The oil chamber 40 allows the spool 39 to slide. The oil chamber 4
0 is provided with a spring 41, and this spring 41
Due to this, the spool 39 is always held in the neutral position. In the oil chamber 40, the electromagnetic proportional solenoid 10a,
Control valves 41a, 41 controlled to open and close by 10b
b is connected.

Therefore, the electromagnetic proportional solenoids 10a, 10
The control valves 41a and 41b are opened and closed by b. By controlling the opening and closing of the control valves 41a and 41b, the flow rate of the hydraulic oil supplied to the control valves 41a and 41b is adjusted and supplied to the oil chamber 40.

A pilot drain pipe 42 is connected to each of the oil chambers 40 and is led out to a tank or a return pipe line. The pilot drain pipes 42 flow out of the oil chambers 40. A throttle valve (orifice) 43 that regulates the outflow amount of hydraulic oil is provided.

That is, the control valve 10 controls the opening degree of the control valves 41a and 41b based on the energization of the forward or backward tilting electromagnetic proportional solenoids 10a and 10b to introduce the working oil into the oil chamber 40. The hydraulic oil in the chamber 40 is flown out at a flow rate limited by the throttle valve 43 of the pilot drain pipe 42 to control the magnitude of the hydraulic pressure acting on the spool 39, and the hydraulic pressure and the force of the spring 41 are balanced. The spool 39 is adapted to be displaced to this position.

Therefore, the electromagnetic proportional solenoids 10a, 10
By controlling the opening of the control valves 41a and 41b based on the average drive current of the duty-controlled drive currents supplied to b, the corresponding position of the spool 39 can be obtained. An amount of hydraulic oil corresponding to the position of the spool 39 is supplied to or discharged from the valve 11. That is, the tilt cylinder 11 is the spool 3
The fork 7 expands and contracts at a speed corresponding to the position of 9, and the fork 7 tilts.

Next, the operation of the oil pressure control device for the tilt cylinder configured as described above will be described. First,
The forward tilting motion of the fork 7 due to the extending motion of the tilt cylinder 11 will be described.

As shown in FIGS. 1 and 4, the pressure sensor 12
C based on the detection signal of the
The PU 18 detects the lifting position of the fork 7 and the load of cargo handling. Then, based on the operation of the tilt lever 8, the lift position of the fork 7 and the load of the cargo handling at that time are detected. At this time, the CPU 18 determines that the lift position of the fork 7 is h.
1. When it is judged that the load of cargo handling becomes g1, the memory 1
The set drive current value I1 is set based on the map MA of 7.

Next, the CPU 18 uses the map M of the memory 17
Based on A, the set drive current value I1 is made to match the drive current value I1. Then, the CPU 18 selects the map M1 that matches the drive current value I1 and the maximum drive current value I1 when the tilt lever 8 becomes equal to or larger than the predetermined operation angle −θn.

Thereafter, when the operation angle θ of the tilt lever 8 is within the reference operation angle −θ1 from the neutral position, the CPU 1
Reference numeral 8 reads the drive current value I based on the selected map M1. In this case, the drive current value I is 0 because the tilt cylinder 11 is extended and the fork 7 does not tilt forward, so the CPU 18 causes the D / A converter 19 to operate.
The duty ratio based on the drive current value I is not output to the constant current amplifier 20 via. As a result, the tilt cylinder 11 does not extend and the fork 7 is not tilted forward.

When the operation angle θ of the tilt lever 8 is in the range from the reference operation angle −θ1 to the predetermined operation angle −θn, the CPU 18 operates the tilt lever 8 at that time based on the selected map M1. The drive current value I corresponding to θ is read from the memory 17. After that, the CPU 18 calculates the duty ratio based on the read drive current value I, and outputs this duty ratio to the constant current amplifier 20 via the D / A converter 19.

The constant current amplifier 20 outputs a drive current based on the duty ratio to the electromagnetic proportional solenoids 10a and 10b of the control valve 10. Then, the opening of the control valves 41a and 41b is controlled by the average drive current of the duty-controlled drive currents. Therefore, the flow rate of the hydraulic oil supplied from the control valve 10 is adjusted, the tilt cylinder 11 extends, and the fork 7 tilts forward.

When the operation angle θ of the tilt lever 8 becomes equal to or larger than the predetermined operation angle −θn, the CPU 18 sets the drive current value I1 based on the selected map M1 regardless of the operation angle θ of the tilt lever 8. read out. The CPU 18 calculates the duty ratio based on the drive current value I1,
This duty ratio is output to the constant current amplifier 20 via the D / A converter 19.

The constant current amplifier 20 outputs a drive current based on the duty ratio to the electromagnetic proportional solenoids 10a and 10b of the control valve 10. Then, the opening of the control valves 41a and 41b is controlled by the average drive current of the duty-controlled drive currents. Therefore, the flow rate of the hydraulic oil supplied from the control valve 10 is adjusted, the tilt cylinder 11 extends, and the fork 7 tilts forward. At this time, the drive current value I1 is the map M1.
, The maximum extension speed of the tilt cylinder 11 based on the selected map M1 and the maximum forward tilting motion of the fork 7.

Next, the backward tilting operation of the fork 7 will be described. Similarly to the above, as shown in FIGS. 1 and 3, the CPU 18 detects the lift position of the fork 7 and the load of the cargo handling based on the detection signal of the pressure sensor 12 and the detection signal of the lift sensor 13. Then, based on the operation of the tilt lever 8, the lift position of the fork 7 and the load of the cargo handling at that time are detected. At this time, when the lift position of the fork 7 is h2 and the load of the cargo handling is g2, the CPU 18 determines that the memory 1
The set drive current value I2 is set based on the map MA of 7.

Next, the CPU 18 uses the map M of the memory 17
Based on A, the set drive current value I2 is made to match the drive current value I2. Then, the CPU 18 selects the map M2 that matches the drive current value I2 and the maximum drive current value I2 when the tilt lever 8 becomes equal to or larger than the predetermined operation angle θn.

Thereafter, when the operation angle θ of the tilt lever 8 is within the reference operation angle θ1 from the neutral position, the CPU 18
Reads the drive current value I based on the selected map M2. In this case, the drive current value I is 0 because it is a dead zone in which the tilt cylinder 11 is extended and the fork is not tilted backward, and the CPU 18 sends the constant current amplifier 20 to the constant current amplifier 20 via the D / A converter 19 based on the drive current value I. The duty ratio is not output. As a result, the tilt cylinder 11
Does not contract, and the rearward tilting operation of the fork 7 is not performed.

When the operation angle θ of the tilt lever 8 is in the range of the reference operation angle θ1 to the predetermined operation angle θn,
The CPU 18 determines the drive current value I corresponding to the operation angle θ of the tilt lever 8 at that time based on the selected map M2.
Is read from the memory 17. After that, the CPU 18 calculates the duty ratio based on the read drive current value I, and outputs this duty ratio to the constant current amplifier 20 via the D / A converter 19.

The constant current amplifier 20 outputs a drive current based on the duty ratio to the electromagnetic proportional solenoids 10a and 10b of the control valve 10. Then, the opening of the control valves 41a and 41b is controlled by the average drive current of the duty-controlled drive currents. Therefore, the flow rate of the hydraulic oil supplied from the control valve 10 is adjusted, the tilt cylinder 11 contracts, and the fork 7 is tilted backward.

When the operation angle θ of the tilt lever 8 becomes equal to or larger than the predetermined operation angle θn, the CPU 18 determines the maximum drive current value I2 based on the selected map M2 regardless of the operation angle θ of the tilt lever 8. Read out. CPU 1
8 calculates the duty ratio based on the drive current value I2, and outputs this duty ratio to the constant current amplifier 20 via the D / A converter 19.

The constant current amplifier 20 outputs a drive current based on the duty ratio to the electromagnetic proportional solenoids 10a and 10b of the control valve 10. Then, the opening of the control valves 41a and 41b is controlled by the average drive current of the duty-controlled drive currents. Therefore, the flow rate of the hydraulic oil supplied from the control valve 10 is adjusted, the tilt cylinder 11 contracts, and the fork 7 is tilted backward. At this time, the drive current value I2 is the map M2.
, The contraction speed of the tilt cylinder 11 based on the selected map M2 becomes maximum, and the rearward tilting motion of the fork 7 becomes maximum.

Therefore, the higher the height of the fork 7, the lower the set drive current value is set, and the larger (heavy) the load of the cargo is, the lower the drive current value is set. Therefore, the tilting speed of the fork 7 is increased. Is set to low speed. As a result, when the tilt lever 8 is operated, the tilting speed of the fork 7 becomes very small, so that the collapse and drop of the cargo handling of the fork 7 can be prevented, and the operability of the tilt lever 8 can be improved.

Further, the lower the height of the fork 7, the higher the set drive current value is set, and the smaller (lighter) the load of cargo handling is, the higher the set drive current value is set. As a result, when the tilt lever 8 is operated, the tilting speed becomes high, the fork 7 can be moved to a predetermined tilting position, and the responsiveness of the fork 7 can be improved.

In the present embodiment, the set drive current value is set from the map MA based on the lift position of the fork 7 and the load of the cargo handling, and this set drive current value is directly associated with the map MB. A value obtained by multiplying the current value by the set rate may be set as the drive current value I of the map MB. That is, a map obtained by multiplying the set drive current value by, for example, 80% is set as the drive current value I, and when the tilt lever 8 becomes equal to or larger than the predetermined operation angle θn, the map that matches the drive current value I obtained by multiplying this set rate. May be selected.

Further, in this embodiment, the set drive current value is set from the map MA based on the lift position of the fork 7 and the load of cargo handling, but the set drive current value is set only by the lift position of the fork 7. You may do so. That is, the set drive current value may be set based on a map in which the set drive current value is set lower as the lift position of the fork 7 is higher.

Further, the set drive current value may be set only by the load of cargo handling. That is, the set drive current value may be set based on a map in which the set drive current value is set lower as the load of the cargo handling is larger.

Further, in the present embodiment, when the tilt lever 8 becomes the reference operation angle ± θ1 or more, the tilt cylinder 11 expands and contracts to tilt the fork 7, but it increases proportionally from the neutral position. The map MB is set, the drive current value I is set based on this map MB,
The tilt cylinder 11 may be expanded and contracted with the drive current value I based on the operation angle θ of the tilt lever 8 from the neutral position.

[0066]

As described above in detail, according to the present invention,
Adjust the tilting speed of the fork based on the load change of the load,
There is an excellent effect that the operability of the tilt lever can be improved and the collapse of the load due to the tilting movement of the fork can be prevented.

Further, it is possible to adjust the tilting motion of the fork based on the change in the lifting height of the fork, improve the operability of the tilt lever, and prevent the collapse of the load accompanying the tilting motion of the fork. It has an excellent effect.

Further, the tilting speed of the fork is adjusted based on the change in the lift of the fork and the change in the load of the load to improve the operability of the tilt lever and prevent the collapse of the load accompanying the tilting motion of the fork. It has the excellent effect of being able to

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a configuration of a hydraulic control device for a tilt cylinder in a forklift embodying the present invention.

FIG. 2 is a hydraulic control circuit diagram of a control valve that controls a lift cylinder and a tilt cylinder.

FIG. 3 is a characteristic diagram showing a map for controlling the opening of a control valve and controlling the expansion and contraction of a tilt cylinder.

FIG. 4 is a characteristic diagram showing a map for controlling the opening of a control valve and controlling the expansion and contraction of a tilt cylinder.

FIG. 5 is a block circuit diagram showing the configuration of a hydraulic control device for a tilt cylinder in a conventional forklift.

FIG. 6 is a characteristic diagram showing that the operating force increases with respect to the operating angle of the tilt lever.

FIG. 7 is a characteristic diagram of a map for setting a drive current value for controlling the opening of the electromagnetic proportional control valve.

[Explanation of symbols]

3 ... Controller as hydraulic control means for cargo handling, 6 ... Lift cylinder, 7 ... Fork, 8 ... Tilt lever, 9
... Lever operation amount detection sensor as operation amount detection means, 1
0 ... Control valve, 11 ... Tilt cylinder, 1
2 ... Pressure sensor as load detecting means, 13 ... Lifting sensor as lifting height detecting means, 17 ... Memory as storage means, θ ... Operating angle as operation amount

Claims (3)

[Claims] 1. A tilt cylinder for tilting a fork of a forklift, a load detecting means for detecting a load of cargo handling lifted by the fork, and an operation amount of an operating means for setting an extension / contraction speed of the tilt cylinder. An operation amount detection means, a control valve for adjusting the tilting speed of the fork by adjusting the flow rate of the working oil of the tilt cylinder, and an opening degree control of the control valve for the operation amount of the operation means for each load of the cargo handling. Storage means for storing the opening command value of the fork, and the tilt control of the fork by controlling the opening of the control valve by the opening command value corresponding to the load of the cargo handling at that time based on the operation amount of the operating means. And a hydraulic control device for a tilt cylinder in a forklift including a hydraulic control means for cargo handling. 2. A tilt cylinder for tilting a fork of a forklift, a lift cylinder for raising and lowering the fork, a lift detecting means for detecting a lift position of the fork, and an expansion / contraction speed of the tilt cylinder. An operation amount detection means for detecting an operation amount of the operation means, a control valve for adjusting a tilting speed of the fork by adjusting a flow rate of the working oil of the tilt cylinder, and a control valve for each lift position of the fork. A storage unit that stores an opening command value for controlling the opening of the control valve with respect to the operation amount of the operation unit, and an opening command value corresponding to the lift position of the fork at that time based on the operation amount of the operation unit. Hydraulic control means for cargo handling that controls the opening of the control valve to control the tilting of the fork. Hydraulic control device for tilt cylinder in lift. 3. A tilt cylinder for tilting a fork of a forklift, a lift cylinder for raising and lowering the fork, a load detecting means for detecting a load of cargo handling lifted by the fork, and a lift position of the fork. Lift detecting means, operation amount detecting means for detecting the operation amount of the operating means for setting the expansion / contraction speed of the tilt cylinder, and adjusting the tilting speed of the fork by adjusting the flow rate of the working oil of the tilt cylinder. Control valve, a storage means for storing an opening command value for controlling the opening of the control valve with respect to the lift position of the lift cylinder and the load of the cargo handling, and the operation amount of the operation means. Based on the opening command value corresponding to the lift position of the fork and the load of the cargo at that time. The hydraulic control device for the tilt cylinder in a forklift and a hydraulic control unit for handling for the control valve to perform the opening control to tilting control of the fork.