JP2002370900A - Lift control device of forklift truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forklift truck capable of improving energy efficiency, and capable of reducing noise a lift-up time. SOLUTION: At lift-up time for lifting a fork 10, a proportional control valve 28 is put in a fully opening state by a CPU 24, and output control of a hydraulic motor 27 is performed by deriving an output command value of the hydraulic motor 27 on the basis of an operation angle of a lift lever 12 derived by an angle detecting means 20. When simultaneously using the hydraulic motor 27 for the other function such as tilt other than a lift, the hydraulic motor 27 is controlled on output according to a lower value of the output command value. A lift-down time for lowering the fork 10, the hydraulic motor 27 is controlled by a minimum value required for operating the proportional control valve 28, that is, the output command value required for flowing oil round to a hydraulic passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forklift lift for raising and lowering a fork which is raised and lowered along a mast erected on a vehicle body by controlling output of a hydraulic motor and a proportional control valve in accordance with an operation angle of a lift lever. It relates to a control device.

[0002]

2. Description of the Related Art Generally, in a forklift, a mast is attached to a front portion of a vehicle body, and by operating a lift lever provided in a driver's seat, a hydraulic motor is driven to operate a lift cylinder to expand and contract the mast. A pair of L-shaped forks attached to the mast via brackets are moved up and down by expansion and contraction of the mast.

[0003] Conventionally, when the lift lever is operated in the ascending direction, the hydraulic motor is driven at almost the maximum output, and the hydraulic pressure to the lift cylinder is controlled by adjusting the opening of the proportional control valve. Was rising. On the other hand, at the time of the lift-down operation in which the lift lever is operated in the downward direction, the hydraulic motor is controlled to the minimum speed required to operate the proportional control valve, and the hydraulic pressure to the lift cylinder is controlled by adjusting the opening of the proportional control valve. The fork was being lowered.

[0004]

However, in the conventional case,
Since the hydraulic motor is driven at maximum output during lift-up and the lift speed when the fork rises is controlled by the proportional control valve, the oil that is not actually used for lift-up passes through the proportional control valve to the oil tank. As a result, there is a problem that the energy efficiency at the time of lift-up is reduced.

[0005] In addition, since the hydraulic motor is always driven at the maximum output state during lift-up, there is also a problem that the noise of the hydraulic motor is extremely large.

Accordingly, an object of the present invention is to provide a forklift capable of improving energy efficiency and reducing noise when lifting up.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a hydraulic motor and a proportional motor for lifting and lowering a fork that is raised and lowered along a mast erected on a vehicle body. In a lift control device of a forklift that lifts and lowers by an output control of a control valve, an operation direction detection unit that detects an operation direction of the lift lever that raises and lowers the fork, and an angle detection unit that detects an operation angle of the lift lever When the operation of the lift lever in the ascending direction is detected by the operation direction detection means, the proportional control valve is controlled to a fully open state, and the hydraulic pressure is controlled based on the operation angle detected by the angle detection means. The output command value of the motor is derived to control the hydraulic motor, and the operating direction detecting means moves the lift lever in the downward direction. Control means for controlling the opening degree of the proportional control valve based on the operation angle detected by the angle detection means while holding the output command value of the hydraulic motor at a predetermined value when the operation is detected; It is characterized by having.

[0008] According to such a configuration, at the time of lift-up for raising the fork, the proportional control valve is fully opened by the control means, and the output of the hydraulic motor is determined based on the operation angle of the lift lever derived by the angle detection means. Since the output of the hydraulic motor is controlled by deriving the command value, unlike the conventional case where the hydraulic motor is always driven at the maximum output state during lift-up, there is no return of oil to the oil tank and energy efficiency is reduced. The noise can be improved, and the noise of the hydraulic motor can be significantly reduced. At this time, by using an AC motor as the hydraulic motor, it is possible to improve the control accuracy of the fork at the time of lifting up, and it is possible to improve the responsiveness of the lifting speed.

Further, according to the present invention, the hydraulic motor is also used for control other than the lift of the fork, and the control means operates the lift lever in an ascending direction by the operation direction detection means. When is detected,
When deriving the output command value of the hydraulic motor based on the operation angle in a state where the proportional control valve is controlled to the fully opened state, the derived output command value and the hydraulic pressure in the control other than the lift of the fork. The hydraulic motor is controlled according to a lower value as compared with an output command value of the motor.

According to such a configuration, when the hydraulic motor is used for the control other than the lift and the lift motor and the other motor are used simultaneously, the hydraulic motor is controlled according to the lowest output command value. Driving can be realized.

Further, the present invention is characterized in that the predetermined value which is an output command value of the hydraulic motor when the operation of the lift lever in the descending direction is detected by the operation direction detecting means operates the proportional control valve. It is characterized in that it has been set to the minimum value required to make it work.

According to such a configuration, at the time of lift-down for lowering the fork, the hydraulic motor is driven by the minimum value required to operate the proportional control valve, that is, the output command value required to circulate oil to the hydraulic path. , The weight of the fork and the load placed on the fork can be effectively used, and the lift-down can be performed with minimum energy consumption.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a counterbalance type forklift will be described with reference to FIGS. 1 is a perspective view of a counterbalance type forklift, FIG. 2 is a block diagram of a control system, FIG. 3 is a schematic configuration diagram of a hydraulic system, and FIGS. 4 and 5 are flowcharts for explaining operations.

The counterbalance type forklift according to the present embodiment is configured, for example, as shown in FIG. That is, a battery (not shown) is mounted and accommodated below the seat 3 provided in the driver's seat 2 of the vehicle body 1, and the battery supplies power to a traveling motor and a hydraulic motor (neither motor is shown). When the accelerator pedal 4 is depressed, the traveling motor is driven based on an output command value from a control device (not shown), and the vehicle body 1 travels in the forward or rearward direction set by operating the directional lever. . In addition, 5 is a steering wheel and 6 is a brake pedal.

Further, as shown in FIG. 1, a mast 8 is attached to the front portion of the vehicle body 1 so as to be extendable and contractable, and a pair of L-shaped forks 10
Is attached. By operating a lift lever 12 provided in the driver's seat 2, a hydraulic motor is driven based on an output command value from a control device, a lift cylinder (not shown) is operated, and the mast 8 expands and contracts. The fork 10 is moved up and down by the expansion and contraction of 8. Driver's seat 2
In addition to the lift lever 12, the tilt lever 14
The tilt cylinder (not shown) is operated by operating the lever 14, and the mast 8 is tilted (tilted), and the fork 10 is tilted together with the mast 8.
At this time, the tilt control is performed in addition to the lift of the fork 10 by using one hydraulic motor, and the same hydraulic motor is also used to control the attachments other than the fork 10. Is being used.

Next, the configuration of the control device will be described with reference to the block diagram of FIG. As shown in FIG. 2, a detection signal from an angle detection unit 20 which is composed of, for example, a potentiometer and detects an operation angle of the lift lever 12 is converted into a digital signal by an analog / digital conversion unit (hereinafter, referred to as A / D) 21. Then, it is taken into the CPU 24 described later.

Further, as shown in FIG.
The state of the lift lever switch 22 that is turned on and off in accordance with the operation direction of 2 is input to the CPU 24 via a parallel input unit (hereinafter, referred to as PI) 23, and the lift lever 12 is moved forward (for example, in the upward direction). On the back side (for example,
The CPU determines which operation is being performed (downward direction).
24. Here, lift lever switch 2
2 and the CPU 24 correspond to an operation direction detecting means for detecting the operation direction of the lift lever 12.

On the other hand, a control signal from the CPU 24 is output to a hydraulic motor 27 composed of an AC motor and a proportional control valve 28 via a parallel output unit (hereinafter referred to as PO) 26, respectively. 28
Is controlled. At this time, a pulse generator (not shown) for detecting the rotation of the hydraulic motor 27 composed of an AC motor
Is provided to the CPU 24, and a lift speed, which is a speed at which the fork 10 rises, is derived from the number of output pulses of the pulse generator.

The CPU 24 opens the proportional control valve 28 fully when lift-up, that is, when the lift lever 12 is operated in the direction for raising the fork 10 (front side). The output command value Mu of the hydraulic motor 27, which is proportional to the operated angle θr of the lift lever 12, is calculated according to the following equation: Mu = θr × G1. Here, G1 is a gain.

On the other hand, at the time of lifting down, that is, when the lift lever 12 is operated in the direction of lowering the fork 10 (rear side), the operation angle θr of the lift lever 12 detected by the angle detection means 20 at that time indicates: Proportional control valve 2
8 is calculated in accordance with the following equation: Vm = θr × G2..., And the proportional control valve 28 is controlled to the opening target value Vm according to this equation, and the hydraulic pressure path is controlled. The hydraulic motor 27 is controlled by a constant output command value necessary for circulating the oil to generate a so-called pilot pressure.

When the hydraulic motor 27 is used simultaneously with, for example, a tilt other than the lift of the fork 10, the CPU 24 operates the hydraulic motor 27 calculated by the above equation.
Is compared with the output command value of the hydraulic motor 27 in accordance with the tilt angle of the tilt lever 14 according to the operation angle of the tilt lever 14, and the hydraulic motor 2 is set in accordance with the smaller output command value.
7 is performed.

Further, as shown in FIG. 2, calculation data such as the output command value Mu of the hydraulic motor 27 at the time of lift-up and the opening target value Vm of the proportional control valve 28 at the time of lift-down are temporarily stored in the RAM 31. RO is stored
In accordance with a predetermined control program stored in advance in M32, the CPU 24 controls the output of the hydraulic motor 27 and the opening of the proportional control valve 28.

The construction of the hydraulic system is as shown in FIG.
7, the opening of the proportional control valve is adjusted by the output of the CPU 24, and the oil from the oil tank 35 is supplied to the lift cylinder via the proportional control valve 28,
The lift control of the fork 10 is performed.

Next, the operation will be described with reference to the flowcharts of FIGS.

As shown in FIG. 4, as an initial setting, for example, a lift flag set in a built-in register of the CPU 24 is cleared (S1), the output of the hydraulic motor 27 is reset to zero (S2), and the proportional control valve is set. 28 is reset to zero (S3), and the operation angle θr of the lift lever 12 based on the output signal of the angle detection means 20 is set to A / D.
The data is received by the CPU 24 via the CPU 21 (S4).

The CPU 24 determines from the output signal of the lift lever switch 22 whether or not the lift lever 12 is operated (S5).
If O, the process proceeds to step S13 to be described later. If the determination result is YES, it is determined whether the operation direction of the lift lever 12 is “up” or “down” (S6), and it is determined to be “up”. Then, the lift flag is set to “up” (S
7) As the control at the time of lift-up, the target opening value Vm of the proportional control valve 28 is set to 100% and the proportional control valve 28
Is controlled to the fully open state (S8), and the output command value Mu of the hydraulic motor 27 proportional to the operation angle θr of the lift lever 12 is calculated by the calculation of the above equation (S8).
9).

On the other hand, if the result of the determination in step S6 is "down", the lift flag is set to "down" (S10). An opening target value Vm of the proportional control valve 28 proportional to the operation angle θr of the lift lever 12 is calculated (S11), and the output command value of the hydraulic motor 27 is set to a constant value (a constant experimentally obtained in advance). (S1
2) Then, the process proceeds to step S13 together with the case where the process of step S9 is performed.

In step S13, the opening target value Vm of the proportional control valve 28 is calculated based on the opening control value in the previous control (hereinafter, referred to as the previous value) stored in the internal memory of the CPU 24, for example. Is determined (S13). If the determination result is NO, it can be determined that the operation angle of the lift lever 12 is smaller than the previous time, and it is determined whether the previous value is zero (S14). If the determination result is NO, the current opening control value of the proportional control valve 28 (hereinafter, referred to as the current value) is set to (previous value -1).
Is set (S15), and then the process proceeds to step 18.

If the result of the determination in step S13 is YES, it can be determined that the operation angle of the lift lever 12 is larger than the previous time, and the current value of the proportional control valve 28 is set in step S8 or S11. After the opening target value is set (S16), the process proceeds to step S18. In addition, the determination result of step S14 is YE
If it is S, the current value of the proportional control valve 28 is set to zero (S17), and then the process proceeds to step S18.

Subsequently, in step S18, the opening direction of the proportional control valve 28 is controlled by the CPU 24 in accordance with the contents of the lift flags set in steps S7 and S10 (S18), and the opening of the proportional control valve 28 is performed. The degree is controlled (S19), and as an output value of the hydraulic motor 27,
The output command values obtained in steps S9 and S12 are set (S20).

Further, it is determined whether or not the output command value of the hydraulic motor 27 in other functions such as tilt other than lift (hereinafter referred to as "other function output command value") is zero (S21). If the determination result is NO, it is determined whether the output command value of the hydraulic motor 27 in the lift function (hereinafter, referred to as “lift output command value”) is zero (S22), and the determination result is NO. If, it is determined whether the lift output command value is larger than the other function output command value in step S21 (S23).

The result of the determination in step S23 is YE
If S, the other function output command value is prioritized, and the other function output command value is set as the output value of the hydraulic motor 27 together with the case where the determination result of step S22 is YES (S24), and thereafter, step S23 Is NO
And the result of the determination in step S21 is Y
The process moves to step S25 together with the case of ES, and after the hydraulic motor 27 is controlled according to the set output command value (S
25), and return to S2 described above.

As described above, when the fork 10 is lifted up, the proportional control valve 28 is controlled by the CPU 24.
Is fully opened, the output command value of the hydraulic motor 27 is derived based on the operation angle of the lift lever 12 derived by the angle detection means 20, and the output control of the hydraulic motor 27 is performed. At this time, as in the conventional case where the hydraulic motor 27 is driven in the maximum output state, the oil tank 35 for oil is used.
There is no return to energy efficiency.

When the hydraulic motor 27 is simultaneously used for other functions such as tilt other than the lift, the output of the hydraulic motor 27 is controlled in accordance with the lower output command value.

Further, when the fork 10 is lifted down, the hydraulic motor 27 is controlled by the minimum value required to operate the proportional control valve 28, that is, the output command value required to circulate the oil in the hydraulic path. You.

Therefore, according to the above-described embodiment, the output of the hydraulic motor 27 is controlled based on the operation angle of the lift lever 12 by fully opening the proportional control valve 28 at the time of lift-up. Energy efficiency can be greatly improved, and the hydraulic motor 2
7 can be greatly reduced.

At this time, since the AC motor is used as the hydraulic motor 27, the control accuracy of the fork 10 at the time of lift-up can be improved, and the responsiveness of the lift speed can be improved.

When the hydraulic motor 27 is also used for controlling the tilt function other than the lift function at the same time, and one hydraulic motor 27 is used simultaneously with the lift and the other, the value of the lower output command value in the lower function is used. According to the hydraulic motor 2
7, a safer operation can be realized.

Further, at the time of lifting down, the fork 10
And while effectively utilizing the weight of the luggage placed there,
It can be lifted down with minimum energy consumption.

In the embodiment described above, the angle detecting means 20 for detecting the operation angle of the lift lever 12 is
The case of using a potentiometer has been described,
The invention is not particularly limited to a potentiometer, and an encoder may be used.

Further, in the above-described embodiment, the case where the hydraulic motor 27 is used for other functions such as tilt other than the lift has been described. However, the hydraulic motor 27 does not necessarily need to be used for other functions. The hydraulic motor only needs to be used at least for lifting and lowering the fork 10, that is, for lifting.

In the above-described embodiment, it goes without saying that the hydraulic motor 27 is not limited to the AC motor described above, but may be a DC motor. In this case, the above-described pulse generator becomes unnecessary.

Further, in the above-described embodiment, the case where the present invention is provided to the counterbalance type forklift is described. However, other than the above-described counterbalance type to which the present invention can be applied, other types such as a reach type forklift can be used. Needless to say, the present invention can be applied to a forklift of a model type, and in this case, the same effect as in the above-described embodiment can be obtained.

The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention.

[0045]

As described above, according to the first aspect of the present invention, at the time of lift-up for raising the fork, the proportional control valve is fully opened by the control means, and the lift lever guided by the angle detecting means. In order to control the output of the hydraulic motor by deriving the output command value of the hydraulic motor based on the operation angle of the hydraulic motor, as in the conventional case where the hydraulic motor is constantly driven at the maximum output state during lift-up, the oil It is possible to provide a forklift capable of improving energy efficiency by eliminating return to the tank and significantly reducing noise of the hydraulic motor.

According to the second aspect of the present invention, 1
When two hydraulic motors are used for the control other than the lift and the lift and the other are used at the same time, the hydraulic motors are controlled according to the lowest output command value, so that safer operation can be realized. .

According to the third aspect of the present invention, at the time of lift-down for lowering the fork, the minimum value required for operating the proportional control valve, that is, the output required for circulating oil to the hydraulic path. Since the hydraulic motor is controlled by the command value, it is possible to effectively use the weight of the fork and the load placed on the fork and to perform the lift-down with the minimum energy consumption.

[Brief description of the drawings]

FIG. 1 is a perspective view of a counterbalanced forklift according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control system according to the embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a hydraulic system according to an embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 5 is a flowchart for explaining the operation of the embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 8 Mast 10 Fork 12 Lift lever 14 Tilt lever 20 Angle detection means 22 Lift lever switch (operation direction detection means) 24 CPU (operation direction detection means, control means) 27 Hydraulic motor 28 Proportional control valve

Claims (3)

[Claims] 1. A lift control device for a forklift, wherein a fork lifted and lowered along a mast erected on a vehicle body is lifted and lowered by output control of a hydraulic motor and a proportional control valve according to an operation angle of a lift lever. Operating direction detecting means for detecting an operating direction of the lift lever for raising and lowering; an angle detecting means for detecting an operating angle of the lift lever; and operating the lift lever in the ascending direction by the operating direction detecting means. When detected, the proportional control valve is controlled to a fully open state, and based on the operation angle detected by the angle detection means, an output command value of the hydraulic motor is derived to control the hydraulic motor, When an operation of the lift lever in the descending direction is detected by the operation direction detection means, an output command value of the hydraulic motor is provided. A lift control device for a forklift, comprising: control means for controlling an opening degree of the proportional control valve based on the operation angle detected by the angle detection means while maintaining a constant value. 2. The apparatus according to claim 1, wherein the hydraulic motor is also used for control other than the lift of the fork, and the control unit detects that the operation of the lift lever in the ascending direction is detected by the operation direction detection unit. When deriving the output command value of the hydraulic motor based on the operation angle in a state where the proportional control valve is controlled to the fully open state, the derived output command value and control other than the lift of the fork The lift control device for a forklift according to claim 1, wherein the hydraulic motor is controlled in accordance with a lower value as compared with an output command value of the hydraulic motor in (1). 3. The predetermined value which is an output command value of the hydraulic motor when the operation of the lift lever in the descending direction is detected by the operation direction detecting means is necessary for operating the proportional control valve. The lift control device for a forklift according to claim 1 or 2, wherein the forklift is set to a minimum value.