JP3074896B2 - Hydraulic control device for tilt cylinder in forklift - Google Patents

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 operation of a mast (hereinafter referred to as a fork for convenience of explanation), a forward tilting operation and a rearward tilting operation are performed as shown in FIGS. This is performed based on the operation direction of the tilt lever 51, and the tilting speed is determined by the tilt lever 5
1 is set by a lever operation angle (operation amount) θ. That is, the electromagnetic proportional control valve 52 switches based on the operation direction of the tilt lever 51, and the tilt cylinder 5
3 by changing the supply direction of the hydraulic oil supplied to the fork 54.
Is tilted. Further, the supply of hydraulic oil to the electromagnetic proportional control valve 52 is adjusted based on the operation angle (operation amount) θ of the tilt lever 51, and the tilting speed of the fork 54 is controlled. The operation force of the tilt lever 51 increases linearly based on the operation angle θ of the tilt lever 51.

The tilting 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 composed of 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
Is output to the tilt lever 51 at that time.
Is calculated. The CPU 58 controls the lever operation angle θ.
Is calculated, the drive current value I to be supplied to the electromagnetic proportional control valve 52 is calculated based on a map in which the drive current value I is set for the operation angle θ stored in the memory 59 shown in FIG. 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 corresponding to 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. The control signal is converted into an analog signal, 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 hydraulic oil to the tilt cylinder 53 at a supply or outflow amount determined by the drive current value I (that is, the lever operation angle θ). Accordingly, the drive current value I is obtained based on the operation angle θ of the tilt lever 51, and the supply or discharge amount of the hydraulic oil at that time is determined by the drive current value I, and the tilting speed is determined. 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 fork 54 is lifting a load, the higher the height of the fork 54, the slower the tilt cylinder 53 is controlled,
It is necessary to make the tilting speed of the fork 54 slow.
In particular, when the fork 54 is tilted forward,
The load of the load being lifted by the fork 54
It is necessary to make the forward leaning operation slow in consideration of the height of the vehicle.

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, and there is a problem that operability is poor.

Further, the operation angle θ of the tilt lever 51 is erroneously determined.
Is increased, the tilting speed of the fork 54 increases, and there is a risk that the load may fall from the fork 54 especially in the case of the forward tilting operation.

[0009]

The present invention has been made to solve the above problems.
Be those which, as its first object, based on the fork height change of the fork to adjust the tilt motion of the fork, it is possible to improve the operability of the tilt lever, the load caused by the tilting motion of the fork An object of the present invention is to provide a hydraulic control device for a tilt cylinder in a forklift capable of preventing collapse.

A second object is to adjust the tilting speed of the fork based on a change in the lift of the fork and a change in the load of the load to improve the operability of the tilt lever, and to prevent the collapse of the load due to the tilting operation of the fork. To provide a hydraulic control device for a tilt cylinder in a forklift capable of performing the following.

[0012]

[0013]

The present invention solves the above problems.
For this purpose, the first invention of the present application includes 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 a tilt cylinder. An operation amount detection means for detecting an operation amount of the operation means for setting an expansion / contraction speed, a control valve for adjusting a flow rate of hydraulic oil of the tilt cylinder to adjust a tilting speed of the fork, and a lifting position of the fork Storage means for storing an opening command value for controlling the opening of the control valve with respect to the operation amount of the operating means at that time,
A hydraulic control unit for cargo handling for controlling the opening degree of the control valve by an opening command value corresponding to the lift position of the fork at that time based on the operation amount of the operating means and performing the tilt control of the fork. That is the gist.

According to a second aspect of the present invention, there is provided a tilt cylinder for tilting a fork of a forklift, a lift cylinder for raising and lowering the fork, load detecting means for detecting a load of cargo handling lifted by the fork, and lifting of the fork. A lift detecting means for detecting a high position, an operation amount detecting means for detecting an operation amount of the operating means for setting an expansion / contraction speed of the tilt cylinder, and a flow rate of hydraulic oil of the tilt cylinder to adjust the fork of the fork. A control valve for adjusting a tilting speed, a storage means for storing an opening command value for controlling an opening of the control valve with respect to an operation amount of an operation means for each of a lifting position of the lift cylinder and a load of cargo handling; The opening finger corresponding to the fork's lifting position and the load of the cargo handling at that time based on the operation amount of the means 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]

[0016]

Hydraulic control means for [action] cargo handling reads the opening command value corresponding to the fork height position of the fork at that time with respect to the operation amount of the operation means when the from the storage means. Based on the opening command value read from the storage unit, the loading hydraulic control unit 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 loading hydraulic control means reads from the storage means an opening command value corresponding to the current lifting position and the load of the loading with respect to the operation amount of the operating means at that time.
Based on the opening command value read from the storage unit, the cargo handling hydraulic control unit controls the opening of the control valve to control the expansion and contraction of the tilt cylinder and the tilt control of the fork.

[0018]

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

As shown in FIG. 1, the forklift is provided with a lift lever 1 in the driver's seat. 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 hydraulic control unit for cargo handling. The opening of the control valve 4 is controlled by the controller 3 to adjust the flow rate of the hydraulic oil. The adjusted hydraulic oil is supplied to a lift cylinder 6 provided on the mast 5, and the lift cylinder 6 is controlled to move up and down. The lifting / lowering control of the lift cylinder 6 controls the lifting / lowering speed of the fork 7.

The forklift is provided with a tilt lever 8 at the driver's seat. Then, the operation direction and 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 operation amount detection means and output to the controller 3. The opening of the control valve 10 is controlled by the controller 3 to adjust the flow rate of the hydraulic oil. The adjusted hydraulic oil is supplied to the tilt cylinder 11, and the mast 5 is tilt-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 tilt 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 of the reference operation angle θ1 from the neutral position or the reference operation angle −θ1 from the neutral position, a dead zone for not operating the tilt cylinder 11 is provided, and the operation angle θ of the lift lever 1 is reduced. If the reference operation angle is ± θ1 or more, the opening of the control valve 10 is controlled by the controller 3 based on the operation angle θ, and the tilting control of the fork 7 is performed. Further, when the tilt lever 8 becomes a predetermined operation angle ± θn or more, the controller 3 controls the control valve 10 to a constant opening regardless of the operation angle θ, and supplies a certain amount of hydraulic oil to the tilt cylinder 1.
1 to control the tilting of the fork 7 at a constant speed.

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

The hydraulic oil is supplied to the control valve 4 by an oil pump 15 rotated by the drive of the engine 14, and the hydraulic oil flowing from the drain of the control valve 4 is supplied to the control valve 10. I have.

The controller 3 has an A / D converter 16 for converting an input detection signal into a digital signal. The controller 3 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 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 and MB described later;
A CPU 18 for performing arithmetic processing based on the input signal, various data in a memory 17 and a work program;
It comprises a D / A converter 19 for converting a command signal from the controller 8 into an analog signal and a constant current amplifier 20 for outputting an output signal to the control valves 4 and 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.
3 is input, and this detection signal is converted into a digital signal and output to the CPU 18.

As shown in FIG. 3 and FIG.
Stores a map MA for obtaining a set drive current value based on the lifting position of the fork 7 for each load of the cargo being lifted by the fork 7. This map MA
The set driving current value IM is set when the lifting position of the fork 7 is minimum and there is no cargo handling, and the set driving current value IL is set when the lifting position of the fork 7 is minimum and the cargo handling is large (allowable maximum load). (<IM) is set.

When the lift position of the fork 7 is at the maximum, the set drive current value IN (<IL
) Is set. In addition, this map M
The slope of A and the levels of the set drive current values IM, IL, and IN are based on 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 lifted by the fork 7 and the lifting position of the fork 7.

The tilt lever 8 is provided in the memory 17.
M for setting the drive current value I based on the operation angle θ
B is stored. This map MB is selected as follows. That is, the set drive current value set based on the map MA is made to correspond to 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 matches the drive current value I 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 between the neutral position and the reference operation angle −θ1 or between the neutral position and the reference operation angle θ1, the drive current value I is set to be 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 equal to or more than ± θn, 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 driving current value I is determined based on the map MA.
M is set. The set drive current value IM is stored in the map MB
When the operation angle θ of the tilt lever 8 is equal to or larger than the predetermined operation angle ± θn, the drive current
A map MM that matches M is selected. Therefore, when the tilt lever 8 is operated, the drive current value I with respect to the operation angle θ at that time is set based on the selected map MM.

The drive current value I set as described above
Are read by the CPU 18, 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 solenoids 10a and 10b of the control valve 10.

The electromagnetic proportional solenoids 10a and 10b of the control valve 10 control the control valve 41, which will be described later, by the average driving current of the duty-controlled driving current.
a and 41b are controlled for opening. Therefore,
Since the drive current output from the constant current amplifier 20 increases proportionally with time, the control valves 41a, 41
The opening amount of b gradually increases, and hydraulic oil is supplied from the control valve 10 to the tilt cylinder 11 in due course. Then, the tilt cylinder 11 expands and contracts to start the tilting operation of the fork 7.

Next, the hydraulic circuit 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 via a main pipe 23 on the control valve 4 side by a supply pipe 21 and a branch valve 22. The flow dividing valve 22 is provided with a PS pipe 25 for power steering via a check valve 24. The main line 23 is connected to a supply line 33 connected to the control valve 4 via a check valve 32.

A spool 26 is disposed in the control valve 4 and oil chambers 27 for pilot operation 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 spool 26 is always held at a neutral position by the spring 28.

The oil chamber 27 has an electromagnetic proportional solenoid 4
control valves 29a, 2 controlled to be opened and closed by
9b is connected. Therefore, the constant current amplifier 20
Thus, the control valves 29a and 29b are controlled to open and close via the electromagnetic proportional solenoids 4a and 4b.
The flow rate of the hydraulic oil supplied to the control valves 29a and 29b is adjusted by the opening and closing control of the control valves 29a and 29b, and the hydraulic oil is 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. The pilot drain pipe 30 flows out of each of the oil chambers 27. A throttle valve (orifice) 31 for regulating the outflow of hydraulic oil is provided.

That is, the control valve 4 controls the opening and closing of the control valves 29a, 29b based on the energization of the ascending or descending electromagnetic proportional solenoids 4a, 4b, so that hydraulic oil is introduced into the oil chamber 27, Is controlled at a flow rate restricted by the throttle valve 31 of the pilot drain pipe 30 to control the magnitude of the operating oil pressure acting on the spool 26.
The spool 26 is displaced to a position where the force is balanced.

Accordingly, the control valves 29a, 29b are controlled based on the drive current supplied to the electromagnetic proportional solenoids 4a, 4b.
By controlling the opening degree of b, the position of the spool 26 corresponding thereto is 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
It rises at a speed corresponding to the position of No. 6.

The control valve 10 is supplied with hydraulic oil that has escaped from the control valve 4 via a main line 35. The supply pipe 37 is connected to the control valve 10, and the supply pipe 37 is connected to the main pipe 23 via a check valve 36.

In the control valve 10, spools 39 each having a pilot operation valve 38 are disposed, and at both ends thereof, a pilot operation oil chamber 4 is provided.
0 is formed. The spool 39 is slidable by the oil chamber 40. The oil chamber 4
0 is provided with a spring 41.
Thus, the spool 39 is always held at the neutral position. In the oil chamber 40, the electromagnetic proportional solenoids 10a,
Control valves 41a, 41 controlled to be opened and closed by 10b
b is connected.

Therefore, the electromagnetic proportional solenoids 10a, 10a
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. The pilot drain pipe 42 flows out of each oil chamber 40 into the pilot drain pipe 42. A throttle valve (orifice) 43 for regulating the outflow of hydraulic oil is provided.

That is, the control valve 10 controls the opening of the control valves 41a, 41b based on the energization of the electromagnetic proportional solenoids 10a, 10b for forward leaning or backward leaning. The hydraulic oil in the chamber 40 is discharged at a flow rate restricted 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 displaced to the set position.

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

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

As shown in FIGS. 1 and 4, the pressure sensor 12
On the basis of 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 lifting position of the fork 7 and the load of 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 determined that the load of cargo handling has become g1, the memory 1
The set drive current value I1 is set based on the map MA of FIG.

Next, the CPU 18 stores the map M
The set drive current value I1 is made to match the drive current value I1 based on A. Then, the CPU 18 selects the map M1 that matches this 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
8 reads the drive current value I based on the selected map M1. In this case, the drive current value I is 0 since the tilt zone 11 is extended so that the fork 7 is not tilted forward and the fork 7 is not tilted forward.
Does not output the duty ratio based on the drive current value I to the constant current amplifier 20 via the. As a result, the tilt cylinder 11 does not extend, and the fork 7 does not tilt forward.

If the operation angle θ of the tilt lever 8 is within the range from the reference operation angle -θ1 to the predetermined operation angle -θn, the CPU 18 determines the operation angle of 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. Thereafter, the CPU 18 calculates a 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 degree of the control valves 41a and 41b is controlled by the average drive current of the duty-controlled drive currents. Accordingly, the flow rate of the hydraulic oil supplied from the control valve 10 is adjusted, the tilt cylinder 11 is extended, and the fork 7 is caused to tilt forward.

When the operation angle θ of the tilt lever 8 is equal to or larger than the predetermined operation angle −θn, the CPU 18 determines 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 a 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 solenoids 10a and 10b of the control valve 10. Then, the opening degree of the control valves 41a and 41b is controlled by the average drive current of the duty-controlled drive currents. Accordingly, the flow rate of the hydraulic oil supplied from the control valve 10 is adjusted, the tilt cylinder 11 is extended, and the fork 7 is caused to tilt forward. At this time, the drive current value I1 is stored in the map M1.
, The extension speed of the tilt cylinder 11 based on the selected map M1 is maximized, and the forward tilting operation of the fork 7 is maximized.

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 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 lifting position of the fork 7 and the load of cargo handling at that time are detected. At this time, when the lift position of the fork 7 is h2 and the load of cargo handling is g2,
The set drive current value I2 is set based on the map MA of FIG.

Next, the CPU 18 stores the map M in the memory 17.
The set drive current value I2 is made to match the drive current value I2 based on A. Then, the CPU 18 selects the map M2 that matches this 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 via the D / A converter 19 based on the drive current value I. Does not output the duty ratio. As a result, the tilt cylinder 11
Does not contract, and the fork 7 does not tilt backward.

When the operation angle θ of the tilt lever 8 is within a range from the reference operation angle θ1 to a predetermined operation angle θn,
The CPU 18 determines the driving 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. Thereafter, the CPU 18 calculates a 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 solenoids 10a and 10b of the control valve 10. Then, the opening degree 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 caused to tilt backward.

When the operation angle θ of the tilt lever 8 is 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. Is read. The CPU 1
8 calculates the duty ratio based on the drive current value I2, 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 solenoids 10a and 10b of the control valve 10. Then, the opening degree 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 caused to tilt backward. At this time, the drive current value I2 is set in the map M2.
, The contraction speed of the tilt cylinder 11 based on the selected map M2 is maximized, and the backward tilting operation of the fork 7 is maximized.

Accordingly, the higher the height of the fork 7, the lower the set driving current value is set, and the higher (heavy) the load of the cargo is, the lower the driving current value is set, so that the tilting speed of the fork 7 Is set to low speed. As a result, when the tilt lever 8 is operated, the tilting speed of the fork 7 becomes very slow, so that it is possible to prevent the collapse and drop of the cargo handling of the fork 7 and to improve the operability of the tilt lever 8.

The set drive current value is set higher as the height of the fork 7 is lower, and the set drive current value is set higher as the load of the cargo handling is smaller (lighter). 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 lifting position of the fork 7 and the load of 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 used as the drive current value I of the map MB. That is, a value 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 matches the drive current value I multiplied by the set rate. May be selected.

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 cargo handling. However, the set drive current value is set only by the lift position of the fork 7. You may make it. That is, the set drive current value may be set based on a map in which the higher the lift position of the fork 7, the lower the set drive current value is set.

[0064]

Further, in this embodiment, when the tilt lever 8 becomes equal to or more than the reference operation angle ± θ1, the tilt cylinder 11 expands and contracts and the fork 7 tilts, but it increases proportionally from the neutral position. A map MB is set, and a drive current value I is set based on the 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]

[0067]

As described in detail above, according to the present invention ,
The tilting operation of the fork is adjusted based on the change in the height of the fork, and the operability of the tilt lever can be improved, and the collapse of the load due to the tilting operation of the fork can be prevented. .

Furthermore, 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 to prevent the collapse of the load due to the tilting operation of the fork. There is an excellent effect that it can be done.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a configuration of a tilt cylinder hydraulic control device in a forklift embodied in 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 opening of a control valve and controlling expansion and contraction of a tilt cylinder.

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

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

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

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

[Explanation of symbols]

3 ... Controller as cargo handling hydraulic control means, 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 ... lift sensor as height detecting means, 17 ... memory as storage means, θ ... operation angle as operation amount

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B66F 9/00-11/04 F15B 13/042-13/043

Claims (2)

(57) [Claims] 1. A tilt cylinder for tilting a fork of a forklift, a lift cylinder for raising and lowering the fork, a height detecting means for detecting a lift position of the fork, and setting an expansion / contraction speed of the tilt cylinder. An operation amount detection unit that detects an operation amount of the operation unit; a control valve that adjusts a flow rate of hydraulic oil of the tilt cylinder to adjust a tilting speed of the fork; Storage means for storing an opening command value for controlling the opening of the control valve with respect to the operation amount of the operating means; and an opening command value corresponding to the fork lift position at that time based on the operation amount of the operating means. Hydraulic control means for controlling the opening of the control valve to perform tilt control of the fork. The hydraulic control device for the tilt cylinder in Clift. 2. A tilt cylinder for tilting a fork of a forklift, a lift cylinder for raising and lowering the fork, load detecting means for detecting a load of a cargo lifted by the fork, and detecting a lifting position of the fork. Lifting amount detecting means, operating amount detecting means for detecting the operating amount of the operating means for setting the expansion / contraction speed of the tilt cylinder, and adjusting the flow rate of the hydraulic oil of the tilt cylinder to adjust the tilting speed of the fork. A control valve to be opened; a storage unit storing an opening command value for controlling an opening amount of the control valve with respect to an operation amount of the operation unit for each of a lifting position of the lift cylinder and a load of cargo handling; and an operation amount of the operation unit. Based on the fork lift position at that time and the opening command value corresponding to each load of cargo handling. A hydraulic control device for a tilt cylinder in a forklift, comprising: a hydraulic control unit for cargo handling for controlling tilting of a fork by controlling an opening of the control valve.