JPH05215105A - Hydraulic control device for cargo handling in industrial vehicle - Google Patents

Abstract

PURPOSE:To enable actuation of hydraulic equipment even when a rotation speed changes by reading a control valve opening instruction value for every engine or supply pump rotation speed from a memory means when an operation means is at a standard operation quantity, and controlling a control valve based on it. CONSTITUTION:When an operation angle theta of a lift lever 1 is within a standard operation angle range, a CPU 10 selects a map of drive current values in accordance with a rotation speed of an engine 15 at the time from maps stored in a ROM 9, and it computes a duty ratio based on it. As a drive current duty- controlled is supplied from a constant current amplifier 12 to proportional solenoids 4a, 4b, a control valve is controlled to open or close by an average drive current, and an actuation oil flow from a control valve 4 is regulated, so a lifting speed of a lift cylinder 5 is regulated. When the operation angle thetais a standard operation angle or more, the lifting speed of the cylinder 5 becomes the maximum. A motionless width of the cylinder can thus be set constant if the engine rotation speed is changed, thereby the operability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control system for cargo handling in industrial vehicles such as forklifts.

[0002]

2. Description of the Related Art Conventionally, for example, when a fork of a forklift is moved up and down, as shown in FIGS. 7 and 9, ascent and descent are performed based on the operating direction of a lift lever 51.
The ascending / descending speed is controlled by the lever operation angle (operation amount) θ of the lift lever 51. That is, the lift lever 51
The electromagnetic proportional control valve 52 is switched on the basis of the operating direction to change the supply direction of the hydraulic oil supplied to or discharged from the lift cylinder 53 to raise and lower the fork 54. Further, the supply or the outflow of the hydraulic oil of the electromagnetic proportional control valve 52 is adjusted based on the operation angle (operation amount) θ of the lift lever 51 to control the ascending / descending speed of the fork 54.

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

The controller 56 is composed of an A / D converter 57, a CPU 58, a ROM 59, a RAM 60, a D / A converter 61 and a constant current amplifier 62. The detection signal from the lever operation detection sensor 55 is converted into a digital value by the A / D converter 57 and output to the CPU 58, and the CPU 58 calculates the operation angle θ of the lift lever 51 at that time. When the CPU 58 calculates the lever operation angle θ, the ROM 59 stores the drive current value I for energizing the electromagnetic proportional control valve 52 with respect to the operation angle θ.
Index based on the map shown in FIG.
The drive current value I with respect to the operation angle θ shown in FIG. 9 has been previously tested or logically obtained, and is stored in the ROM 59 as data.

The CPU 58 outputs a drive control signal for the drive current value I to the D / A converter 61 in order to drive and control the electromagnetic proportional control valve 52 at the drive current value I, and the D / A converter 61 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 62 to the electromagnetic proportional control valve 52. Electromagnetic proportional control valve 5
2 is a lift cylinder 53 for supplying hydraulic oil with a supply or outflow amount determined by the drive current value I (that is, the lever operation angle θ).
Supply to. Therefore, the drive current value I is obtained from the lever operation angle θ, and the drive current value I determines the supply or outflow amount of the hydraulic oil at that time, and the ascending / descending speed is determined. That is, the operating angle θ of the lift lever 51 causes the fork 54 to move.
The ascending and descending speed of is determined.

The operating oil is supplied to the electromagnetic proportional control valve 52 by an oil pump 64 which is rotated by driving the engine 63. The flow rate of this hydraulic oil is adjusted by the electromagnetic proportional control valve 52 and is supplied to the lift cylinder 53.

[0007]

However, the supply amount of the hydraulic oil supplied from the oil pump 64 to the electromagnetic proportional control valve 52 changes according to the change in the engine speed. Therefore, even if the electromagnetic proportional control valve 52 is controlled based on the change of the drive current value I, the lift cylinder 5
The supply amount of the hydraulic oil supplied to No. 3 changes.

That is, as shown in FIG. 8, when the engine speed is maximum, the flow rate of the hydraulic oil is adjusted by the electromagnetic proportional control valve 52 from the drive current value I1 and supplied to the lift cylinder 53. Further, when the engine speed is idling (minimum), the flow rate of the hydraulic oil is adjusted by the electromagnetic proportional control valve 52 from the drive current value I2 and supplied to the lift cylinder 53. Therefore, when the engine speed changes, a drive current value I for supplying hydraulic oil to the lift cylinder 53 via the electromagnetic proportional control valve 52.
Changes between drive current values I1 and I2.

Then, as shown in FIG. 9, when the engine speed is maximum, the operation angle θ of the lift lever 51 is changed to θ.
When operated up to 1, the hydraulic oil whose flow rate is adjusted by the electromagnetic proportional control valve 52 is supplied to the lift cylinder 53, and the lift cylinder 53 starts to rise. When the engine speed is idling, the lift lever 5
When the operation angle θ of 1 is operated up to θ2, the hydraulic oil whose flow rate is adjusted by the electromagnetic proportional control valve 52 is supplied to the lift cylinder 53, and the lift cylinder 53 starts to rise.

Therefore, when the engine speed is maximum, the lift cylinder 51 does not operate from the neutral position to the operation angle θ1. When the engine speed is idling, the lift lever 51 moves from the neutral position. The lift cylinder 53 does not operate until the operation angle θ2. As a result, the lift cylinder 5 changes due to a change in engine speed.
3 has a problem that the operability of the lift lever 51 deteriorates because the operating point at which the operation starts changes.

The present invention has been made to solve the above problems, and its purpose is to operate the operating means by a reference amount even if the rotation speed of the engine or the supply pump for supplying the hydraulic oil changes. An object of the present invention is sometimes to provide a hydraulic control device for cargo handling in an industrial vehicle that can operate a hydraulic equipment for cargo handling.

[0012]

In order to solve the above problems, the present invention solves the above-mentioned problems by operating amount detecting means for detecting an operating amount of an operating means for setting an operating speed of a hydraulic equipment for cargo handling, and the hydraulic equipment for cargo handling. A control valve that adjusts the operating speed by adjusting the flow rate of hydraulic oil, a supply pump that supplies the operating oil to the control valve by the rotation of the engine, and a rotation speed detection that detects the rotation speed of the engine or the supply pump. And a storage unit that stores an opening command value of a control valve for starting the cargo handling hydraulic device for each rotation speed of the engine or the supply pump when the operation unit operates a reference operation amount, When the operation amount of the operation means reaches the reference operation amount, the opening degree of the control valve is controlled based on the opening instruction value corresponding to the rotation speed at that time. That a hydraulic control means for handling starting the serial hydraulic equipment for handling the gist thereof.

[0013]

When the operation amount of the operating device becomes the reference operation amount based on the detection signal of the operation amount detecting device, the cargo handling hydraulic control device rotates the engine or the supply pump based on the detection signal of the rotation speed detecting device. For each number of rotations, the opening degree command value of the control valve is read from the storage means in order to start the cargo handling hydraulic equipment. The cargo handling hydraulic control means controls the control valve based on the opening degree instruction value read from the storage means to start the cargo handling hydraulic equipment.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a lift cylinder of a forklift will be described below with reference to FIGS. Since the fork is lowered by its own weight, speed control when the fork is raised will be described.

As shown in FIG. 1, the forklift is provided with a lift lever 1 as an operating means for operating the lift at the driver's seat. Then, the operation direction and operation angle (operation amount) θ of the lift lever 1 are detected by a lever operation amount detection sensor (for example, a potentiometer) 2 as an operation amount detection means and output to a controller 3 as a cargo handling hydraulic control means. To be done. The controller 3 controls the opening / closing of the control valve 4 to adjust the flow rate of the hydraulic oil. The adjusted hydraulic oil is supplied to the lift cylinder 5, and the lift cylinder 5 is controlled to be lifted. By the lift control of the lift cylinder 5,
The ascending speed of the fork 6 is controlled.

The controller 3 is based on the A / D converter 7 for converting the input detection signal into a digital signal, the RAM 8 for temporarily storing the calculation result, the ROM 9 for storing the work program, the input signal, the RAM 8 and the ROM 9. And a D / A converter 1 for converting a command signal from the CPU 10 into an analog signal
1 and a constant current amplifier 12 that outputs an output signal to the control valve 4 based on a command signal.

A / D converter 7 of the controller 3
The detection signal from the lever operation amount detection sensor 2 is converted into a digital signal and output to the CPU 10. In addition, the A / D converter 7 of the controller 3
The detection signal of the rotation speed sensor 13 as the rotation speed detection means is converted into a digital signal and output to the CPU 10. The rotation speed sensor 13 detects the rotation speed of an engine 15 which operates a hydraulic pump 14 for supplying hydraulic oil to the lift cylinder 5.

As shown in FIG. 3, the ROM 9 stores a map for setting the drive current value I with respect to the operation angle θ of the lift lever 1. The map above is for lift lever 1
Is a reference operation angle θ1, the opening of the control valve 4 is controlled for each engine speed to reliably start the lift cylinder 5 regardless of the engine speed, that is, the amount of hydraulic oil supplied to the control valve 4. The drive current value I for storing is stored. The drive current value I for each rotation speed is previously tested or logically obtained, and is stored in the ROM 9 as an opening degree instruction value. Therefore, when the lift lever 1 reaches the reference operation angle θ1, the drive current value I for controlling the opening of the control valve 4 is set for each engine speed. As a result, when the lift lever 1 is set to the reference operation angle θ1, the lift cylinder 5 is always started regardless of the engine speed at that time.

That is, for example, when the engine speed is maximum, the amount of hydraulic oil supplied from the hydraulic pump 14 to the control valve 4 is maximum. Therefore, the drive current value I1 is set so that when the lift lever 1 reaches the reference operation angle θ1, the opening amount of the control valve 4 is reduced and the lift cylinder 5 is started.

When the engine speed is idling, the amount of hydraulic oil supplied from the hydraulic pump 14 to the control valve 4 is minimized. Therefore, the drive current value I2 (> I1) is set so that the opening amount of the control valve 4 is increased and the lift cylinder 5 is started when the lift lever 1 reaches the reference operation angle θ1.

Therefore, the lift lever 1 operates at the reference operating angle θ1 while the engine speed is between the idling and the maximum.
Then, the drive current value I for starting the lift cylinder 5 is set between I1 and I2 for each engine speed at that time.

Further, the map stored in the ROM 9 is set so that the drive current value I becomes 0 when the lift lever 1 is at or below the reference operation angle θ1, and the lift cylinder 5 is operated by the operation of the control valve 4. It is set to not work. When the lift lever 1 becomes equal to or larger than the reference operation angle θ1, the map is such that the drive current value I corresponding to the operation angle θ is set for each engine speed in order to operate the lift cylinder 5.
Further, the map is set such that when the lift lever 1 becomes the operation angle θn or more, the maximum drive current value I is obtained regardless of the engine speed.

As shown in FIG. 1, the CPU 10 detects a detection signal from the rotation speed sensor 13 and a detection signal from the lever operation amount detection sensor 2 via an A / D converter 7. When the lift lever 1 is at or above the reference operation angle θ1, the CPU 10 reads out the drive current value I for the operation angle θ set for each engine speed from the ROM 9, and calculates the duty ratio based on this drive current value I. It is supposed to do.

Then, the CPU 10 supplies the duty ratio based on the drive current value I of the level corresponding to the operation angle θ of the lift lever 1 to the constant current amplifier 12 via the D / A converter 11.
The constant current amplifier 12 outputs the duty-controlled drive current based on the drive current value I to the electromagnetic proportional solenoids 4a and 4b of the control valve 4. Then, the solenoid proportional solenoid 4a of the control valve 4,
Reference numeral 4b controls opening and closing of control valves 29a and 29b, which will be described later, by an average drive current of duty-controlled drive currents.

The control valves 29a and 29b of the control valve 4 are operated by the average drive current of the duty ratio based on the drive current value I of the level corresponding to the operating angle θ of the lift lever 1 and supplied to the lift cylinder 5. Adjust the flow rate of hydraulic oil. And the lift cylinder 5
Also, the ascending speed of the fork 6 is controlled.

Therefore, when the operating angle θ of the lift lever 1 is between the reference operating angles θ1 to θn and the engine speed is idling, the ascending speed of the fork 6 based on the operating angle θ of the lift lever 1 is low, and the engine speed is low. When the rotation speed is maximum, the ascending speed of the fork 6 based on the operation angle θ of the lift lever 1 is high.

Next, the hydraulic circuit of the control valve 4 will be described in detail. As shown in FIG. 2, hydraulic oil supplied from the hydraulic pump 14 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.

A spool 26 is arranged 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 oil chamber 27, and the spring 28 always holds the spool 26 in the neutral position.

In the oil chamber 27, a control valve 29a controlled to be opened and closed by the electromagnetic proportional solenoids 4a and 4b,
29b is connected. Therefore, the constant current amplifier 1
A drive current having a duty ratio based on the drive current value I output from 2 is supplied to the electromagnetic proportional solenoids 4a and 4b, and the control valves 29a and 29b are controlled to open and close with an average drive current based on the duty ratio. The control valve 29a,
By controlling the opening / closing of 29b, the flow rate of the hydraulic oil supplied to the control valves 29a, 29b is adjusted and 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 controlled. 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, by controlling the opening of the control valves 29a and 29b based on the average drive current of the duty-controlled drive currents supplied to the electromagnetic proportional solenoids 4a and 4b, the position of the spool 26 corresponding to that is controlled. As a result, the lift cylinder 5 is supplied or discharged with an amount of hydraulic oil corresponding to the position of the spool 26. That is, the lift cylinder 5 is adapted to move up at a speed corresponding to the position of the spool 26.

Next, the operation of the cargo handling hydraulic control device configured as described above will be described with reference to the flowchart shown in FIG. In step 1, when the ignition switch is operated, the controller 3 is initialized. Then, in step 2, the CPU 10 sets A
Revolution sensor 13 input via the / D converter 7
The number of revolutions of the engine 15 is detected based on the detection from. In step 3, the CPU 10 detects the operation angle θ of the lift lever 1 based on the detection signal of the lever operation amount detection sensor 2 input via the A / D converter 7.

Next, in step 4, the CPU 10 determines whether or not the operation angle θ of the lift lever 1 is within the range of the reference operation angles θ1 to θn, and the operation angle θ of the lift lever 1 is the reference operation angle θ1 to θn. In the case of the range of θn, in step 5, the CPU 10 selects a map of the drive current value I corresponding to the engine speed at that time of the engine 15 from the map stored in the ROM 9 shown in FIG.

Then, in step 6, the CPU 10 sets the drive current value I corresponding to the operation angle θ of the lift lever 1 based on the map selected from the ROM 9, and calculates the duty ratio based on the drive current value I. ..

Next, in step 7, the CPU 10
The duty ratio based on the drive current value I is output to the constant current amplifier 12 via the D / A converter 11. The constant current amplifier 12 energizes the electromagnetic proportional solenoids 4a and 4b with a drive current whose duty is controlled by a duty ratio based on the drive current value I. Then, the control valve 29 is driven by the average drive current of the duty-controlled drive currents.
Opening and closing of a and 29b are controlled. Therefore, the flow rate of the hydraulic oil supplied from the control valve 4 is adjusted, and the rising speed of the lift cylinder 5 is adjusted. That is, the lift speed of the lift cylinder 5 is set based on the engine speed of the engine 15 and the operation angle θ of the lift lever 1.

On the other hand, when the operation angle θ of the lift lever 1 is not within the range of the reference operation angles θ1 to θn in step 4, the CPU 10 determines in step 8 whether the operation angle θ is equal to or larger than the operation angle θn. Then, when the operation angle θ of the lift lever 1 is not equal to or larger than the operation angle θn, the process proceeds to step 2 and the same processing as above is performed.

The operating angle θ of the lift lever 1 is the operating angle θ.
If n or more, in step 9, CPU 10 is in ROM
The maximum drive current value I is read based on the map of No. 9.
Then, in step 10, the CPU 10 calculates the duty ratio based on the maximum drive current value I. Thereafter, similarly to the above, in step 7, the CPU 10 outputs this duty ratio to the constant current amplifier 12 via the D / A converter 11, and the constant current amplifier 12 outputs the duty-controlled drive current to the electromagnetic proportional solenoids 4a and 4b. Energize. Then, similarly to the above, the control valves 29a and 29b are
Is controlled to open and close, and the lift cylinder 5 is raised. At this time, the control valve 4 corresponding to each engine speed
Since the hydraulic oil supplied from the engine is maximum, the rising speed of the lift cylinder 5 at that time is the maximum (maximum).

Therefore, the lift lever 1 is moved to the reference operation angle θ1.
When the above operation is performed, the CPU 10 always sets the drive current value I corresponding to the operation angle θ corresponding to the engine speed, so that the operating oil corresponding to the engine speed is passed through the control valve 4 as shown in FIG. The lift cylinder 5 and the fork 6 can be raised at a speed based on the supply amount of the hydraulic oil.

As a result, since the width of the region (dead zone) where the lift cylinder 5 does not operate can be made constant even if the engine speed of the engine 15 changes, the operability of the lift lever 1 can be improved. ..

Also, since the width of the dead zone can be made constant, the speed control range of the lift cylinder 5 and the fork 6 is widened, and it is easy to match the speed of the lift cylinder 5 and the fork 6 with any speed.

Although the present embodiment is applied to the raising control for raising the lift cylinder of a forklift, it is also possible to apply the present invention to a tilt cylinder and a reach cylinder. In this case, since the forklift is lowered by its own weight, it is not necessary to consider the control at the time of lowering, but in the case of the tilt cylinder and the reach cylinder, it is necessary to consider this, and based on the characteristics shown in FIG. It is necessary to control the speed.

Although this embodiment is embodied as a forklift, it can be applied to other industrial vehicles.

[0044]

As described in detail above, according to the present invention, when the operating means is operated by the reference amount even if the rotation speed of the engine or the supply pump for supplying the hydraulic oil is changed, the hydraulic equipment for cargo handling is provided. It has an excellent effect that it can be operated reliably.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a forklift cargo handling hydraulic control device embodying the present invention.

FIG. 2 is a hydraulic control circuit diagram of a control valve.

FIG. 3 is a characteristic diagram showing a map for setting a drive current value corresponding to an operation angle for each engine speed.

FIG. 4 is a flowchart illustrating the operation of the cargo handling hydraulic control device.

FIG. 5 is a characteristic diagram showing a supply amount of hydraulic oil with respect to an operation angle of a lift lever.

FIG. 6 is a characteristic diagram showing a map for setting a drive current value corresponding to an operation angle for each engine speed when applied to a tilt cylinder and a reach cylinder.

FIG. 7 is a block circuit diagram of a conventional cargo handling hydraulic control device for a forklift.

FIG. 8 is a characteristic diagram showing a supply amount of hydraulic oil with respect to a drive current value based on a change in engine speed.

FIG. 9 is a characteristic diagram showing a change in drive current value with respect to an operating angle of a lift lever.

[Explanation of Codes] 1 ... Lift lever as operation means, 2 ... Lever operation amount detection sensor as operation amount detection means, 3 ... Controller as cargo handling hydraulic control means, 4 ... Control valve, 5 ... Cargo handling hydraulic equipment Lift cylinder as a ...
ROM as storage means, 13 ... Rotation speed sensor as rotation speed detection means, 14 ... Hydraulic pump as supply pump, 15 ... Engine as supply drive means, I ... Drive current value, θ ... Operating angle as operation amount , Θ1 ... Reference operation angle as reference operation amount

Claims (1)

[Claims] 1. An operation amount detecting means for detecting an operation amount of an operating means for setting an operating speed of a cargo handling hydraulic device, and a control valve for adjusting an operating speed by adjusting a flow rate of hydraulic oil of the cargo handling hydraulic device. A supply pump that supplies hydraulic oil to the control valve by rotation of an engine; a rotation speed detection unit that detects a rotation speed of the engine or the supply pump; For each engine or rotational speed of the supply pump, storage means for storing the opening command value of the control valve for starting the cargo handling hydraulic device, and when the operation amount of the operation means becomes the reference operation amount, A cargo handling hydraulic control hand that controls the opening degree of the control valve based on the opening degree command value corresponding to the rotation speed at that time to start the cargo handling hydraulic equipment. Hydraulic control device for a cargo handling in an industrial vehicle equipped with and.