JPS60262797A - Forklift - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Technical field This invention relates to a forklift.

BACKGROUND ART Conventionally, for example, an engine-driven forklift truck uses a single engine to supply power to a pump for traveling and cargo handling, and an oil pump for a clutch. When the forklift is moved slowly, the engine speed is lowered, and when the fork of the forklift is raised, the engine speed is increased to increase the oil pump rotation speed.

However, when driving slowly while raising the fork, it is necessary to operate the clutch or inching pedal while depressing the accelerator to bring it into a half-clutch state, which is difficult and poses a safety problem during cargo handling operations.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and its purpose is to solve the troublesome problems such as half-clutching and inching operations that are performed during cargo handling work in which the forks are moved up and down while traveling. To provide a forklift truck which can eliminate driving operations and an inching pedal for inching operations, simplify driving operations, and improve safety in cargo handling operations.

Structure of the Invention In order to achieve the above object, the structure of the present invention includes a cargo handling pump and a clutch pump that are driven by an engine in the forklift 1 and supplies pressurized fluid to a lift cylinder and a forward/reverse clutch, respectively, and a an actuator that opens and closes a throttle valve;
A pressure control valve that reduces the pressure of the pressure fluid supplied to the clutch via the forward/reverse clutch switching valve and brings the clutch into a half-clutch state, and a pressure control valve that adjusts the pressure fluid supplied to the lift cylinder to adjust the a control valve opening sensor that detects the opening of a control valve that controls vertical movement; a vehicle speed sensor that detects the traveling speed of the forklift; an accelerator opening sensor that detects the amount of depression of the accelerator pedal; and the vehicle speed sensor and control. means for determining whether the cargo handling work is to move the lift 4-' up and down without traveling based on a detection signal from the valve opening sensor, and detecting the control valve opening sensor when it is determined that the cargo handling work is being carried out; a means for operating the thrower 1 to actuator to increase the engine rotational speed according to the amount of the load, and pressure saw fluid supplied to the clutch according to the amount detected by the accelerator opening sensor when cargo handling work is determined and means for operating the pressure control valve to lower the pressure.

EXAMPLE An example embodying the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a clutch pump driven by an engine (not shown), and pressure fluid from the pump 1 is supplied to a regulator valve 2. As shown in FIG. This pressure fluid is then regulated to a constant pressure by the regulator valve 2 and supplied to the forward/reverse clutch switching valve 4 via the supply pipe line 3. The forward/reverse clutch switching valve 4 is turned on or off based on a clutch switching lever provided at the driver's seat of the forklift vehicle, and supplies pressurized fluid to the clutch 5 to connect the forklift for forward or reverse driving. 6
is an orifice installed in the supply pipe 3.

A branch pipe 7 branches off from the supply pipe 3 and is connected to a pressure control valve 8. The pressure of the branched pressure fluid sent into the branch pipe 7 is controlled by a pressure control valve 8, and based on the pressure control, the pressure of the pressure fluid supplied to the clutch 5 via the clutch switching valve 4 is controlled. It's about to be controlled.

Next, this pressure control valve 8 will be explained.

In FIG. 2, 100 is a pressure control valve main body (hereinafter referred to as the valve main body), in which a small diameter hole 12 forming a main passage on the left side, a large diameter hole 13 forming a piston housing hole on the right side, and a large diameter hole 13 forming a piston housing hole in the center. A medium-diameter hole 14 is provided in the section to form a plunger housing hole that communicates the small-diameter hole 12 and the large-diameter hole 13.The small-diameter hole 12 has a suction hole connected to the branch pipe 7 on the left side A port 12a is formed, and a drain port 12b is provided on the right side.The right end opening 13a of the large diameter hole 13 is sealed with a plug 15, and a conduit 3b (first A port 13b is formed which communicates with the supply conduit 3 via a pipe (see figure), and an orifice 16 is provided in the port 13b.

A part of the pressure fluid of the supply pipe line 3 is supplied into the circumferential hole 13 as a control pressure fluid. Moreover, the medium diameter hole 14
has a drain port 14a in its center.

17 is the drain boat 14a of the large diameter hole 13 and the medium diameter hole 14.
The opening and closing of the valve body 100 is controlled by an electromagnetic solenoid valve 18 provided on the front side of the valve body 100. In addition,
In this embodiment, the electromagnetic solenoid valve 18 is
When the solenoid 18a is energized (on), the passage 17 is opened, and when the solenoid 18a is de-energized (off), the passage 17 is closed.

Reference numeral 19 denotes a piston that is disposed so as to be movable in the left-right direction with respect to the large diameter hole 13, and the large diameter portion 19a on the right side slides on the inner circumferential surface of the large diameter hole 13, and the inside of the tip portion Diameter portion 19b
is arranged so as to be in adhesive contact with the right inner circumferential surface of the medium diameter hole 14. Reference numeral 20 denotes a passage hole formed on the right end surface of one piston, which communicates with the port 13b via the suction hole 21 formed in the small diameter hole 19C in the center of the piston 1), and is connected to the inner wall on the open end side. Four transparent discharge holes 22
It communicates with the passage 17 via. Therefore, the control pressure fluid sent from the port 13b is transferred to this passage hole 2.
0 into the passage 17.

Reference numeral 23 denotes a support spring disposed outside the medium diameter portion 19 and the small diameter portion 19C of the piston 19, and the right side is a step surface formed by the large diameter portion 19a and the small diameter portion 19C of the screw 19. 19d, and its left end engages with the step surface 13c formed by the left end of the large diameter hole 13 and the right end of the medium diameter hole 14, so that one piston is always transparently connected to the plug 15. Elastic force is imparted to the same screw 1hen 19.

Therefore, the solenoid 1 of the electromagnetic solenoid valve 18
8a is energized and the passage 17 is always open, the control pressure fluid sent from the port 13b passes through the passage hole 20 and the passage 17 to the drain boat 1.
4a, the piston 19 is held in the state shown in FIG. On the other hand, in a state where an applied voltage with a predetermined duty ratio is applied to the solenoid 18a and the passage 17 is repeatedly energized and de-energized and controlled to open and close, the pressure in the passage hole 2o of one piston increases, so that the support spring 23 The piston 19 is moved to the left against the elastic force of.

A plunger 24 is disposed so as to be movable in the left-right direction with respect to the medium-diameter hole 14, and its tip protrudes to the small-diameter hole 12 and is provided through the plunger to connect the suction ports 1 to 12a and the discharge port 1'. It is designed to close the space between 2 and b. Reference numeral 25 is a housing recess provided in the right end surface of the plunger 24. 26
is a pressure adjusting spring disposed in the accommodation recess 25, whose right end engages with the left end surface of the piston 19, and the plunger 24 always keeps the small diameter hole 12 cold against the plunger 24. Gives elasticity.

When one of the pistons moves to the left, the pressure adjusting spring 26 is compressed according to the amount of movement, and the elastic force of the spring 26 increases, and as a result, the pressure with which the plunger 24 closes the small diameter hole 12 also increases. . Therefore,
The pressure fluid sent from the suction port 12a and sent out through the drain boat 12b has a pressure corresponding to the elastic force of the pressure adjusting spring 26, that is, the amount of leftward movement of the piston 19.

That is, it is difficult for a part of the pressure fluid to flow out from the drain boat 121 to the tank through the supply pipe line 31 and the branch pipe line 7, and the pressure of the pressure oil supplied to the clutch 5 increases.

Next, the solenoid 18 of the electromagnetic solenoid valve 18
An electric circuit for controlling the excitation of a will be explained with reference to FIG.

A vehicle speed sensor 31 detects the rotational speed of the drive shaft of the forklift and outputs a detection signal thereof. Reference numeral 32 denotes an engine rotation sensor that detects the engine rotation speed and outputs a detection signal thereof.

Reference numeral 33 denotes an accelerator opening sensor composed of a potentiometer, which is rotated in conjunction with the accelerator pedal and detects depression of the accelerator pedal. Note that this accelerator pedal is not mechanically connected to the engine throttle that operates the thrower valve, and is only mechanically connected to the opening sensor 33.

34 is a neutral detection switch consisting of a limit switch, which detects the operating position of the clutch switching lever that controls switching of the switching valve 4 of the forward/reverse clutch;
When the lever is in a neutral state, that is, when the switching valve 4 is in a neutral state, an on signal is output. Reference numeral 35 denotes a reverse switch, which is also a limit switch, and detects the operating position of the clutch switching lever, and outputs an on signal when the lever is in the reverse state, that is, when the switching valve 4 is in the marching state. A brake detection switch 36 is a limit switch, which turns on when the brake pedal is depressed and outputs an on signal.

37 is a control valve opening sensor (hereinafter referred to as C/V opening sensor) consisting of a potentiometer, which rotates in conjunction with an operating lever that operates a spool of a control valve that controls the amount of pressure fluid supplied to the lift cylinder. The operation amount of the operating lever, that is, the opening amount of the control valve is detected, and a detection signal is output. 38 is a cargo handling detection switch, which detects the pressure of the pressure fluid for cargo and determines whether there is a cargo or not. Outputs a detection signal.

Reference numeral 39 denotes an inclination sensor that detects the inclination state of the forklift, that is, whether it is on a level ground or on a slope, and outputs a detection signal thereof.

Reference numeral 40 denotes a central processing unit (hereinafter referred to as CPU) which inputs detection signals and "on signals" from each sensor and each switch, and a read-only memory (hereinafter referred to as ROM) 4.
The vehicle speed of the forklift is determined based on the detection signal from the vehicle speed sensor 31, and the engine rotation speed is determined based on the detection signal from the engine rotation sensor 32. Based on the detection signal, the amount of accelerator depression is determined by neutral detection and hack switch 3/1. ．． The state of the forward/reverse clutch switching valve 4 is determined based on the presence or absence of an on signal from the brake detection switch 35, the braking state is determined based on the on signal from the brake detection switch 36, and the forklift is determined based on the detection signal from the C/V opening sensor 37. Based on the lifting speed of the fork and the ON signal from the cargo handling detection switch 38, it is determined whether a load is loaded or not, and the presence or absence of the vehicle body is tilted based on the detection signal from the tilt sensor 39. It is designed to judge the condition. And CPLI
40 outputs drive control signals to the actuator drive circuit 42 and the solenoid drive circuit 43', respectively, based on the state of the forklift 1 determined from time to time.

The actuator drive circuit 42 controls the operation of a throttle actuator 44 connected to the engine throttle that opens and closes the throttle valve of the engine based on the drive control signal, thereby controlling the amount of drive of the engine throttle, that is, the rotational speed of the engine. do. Further, the solenoid drive circuit 43 performs various data based on the drive control signal.
An applied voltage having a T ratio is applied to the solenoid 18a of the electromagnetic solenoid valve 18 to control the pressure of the pressure fluid in the branch pipe 7, that is, the pressure of the pressure fluid supplied to the clutch 5.

In this embodiment, the rotational control amount of the engine and the pressure control amount of the pressure fluid [1 amount are preset for each state of the forklift, and the data is previously set in the R
It is stored in OM41.

Readable and rewritable memory (hereinafter referred to as RAM) 4
5, various calculation results of the CPU/1.0 are temporarily stored.

Next, the operation of the forklift truck 1 configured as described above will be explained.

Now, when the forklift is run without moving up or down, the vehicle speed sensor 31 and C/
Based on the detection signal from the V opening sensor 37, the CPU 40
determines the state and also determines whether the forklift is moving forward or backward based on the presence or absence of ON signals from the neural detection switch 34 and the reverse switch 35. In this state judgment, the CPU 40 determines the amount of depression of the accelerator pedal being operated by the operator based on the detection signal from the accelerator opening sensor, and calculates data on the optimum engine rotation speed according to the amount of depression.
It is read from the OM 41 and output to the actuator drive circuit 42 as a drive control signal. In response to this drive control signal, the actuator drive circuit 42 operates the throttle actuator 44 to drive the engine throttle.

Therefore, when the forklift is simply traveling, the engine speed is controlled depending on how much the accelerator pedal is depressed, and the speed of the forklift is controlled by the depression of the accelerator pedal.

Next, when carrying out cargo handling work by moving the forks up and down while the forklift is stopped, the vehicle speed sensor 31, C/
V opening sensor 37 and Niko i-ral detection switch 34
Based on the detection signal and on signal from c p U 4
0 determines the state, and also determines the opening amount of the control valve based on the detection signal from the operating lever, that is, the C/V opening sensor 37, and determines the optimum fork lifting speed according to the opening amount. Then, the CPU 40 outputs this data to the actuator drive circuit 42 as a drive control signal. Actuator drive circuit 42 operates throttle actuator 44 in response to this drive control signal to drive engine throttles 1 to 1.

Then, pressure fluid discharged from a cargo handling pump (not shown) directly connected to the engine is supplied to the cylinder cylinder, and the fork is set at a rising speed according to the amount of operation of the operating lever.

Therefore, when carrying out cargo handling work in a stopped state, the C/V opening sensor 3
7. That is, the speed of the fork is controlled according to the amount of operation of the operating lever.

Next, when carrying out cargo handling work, i.e., moving the fork up and down while driving, the vehicle speed sensor 1 31 and the C/V opening sensor 3
Based on the detection signal from 7, the CPU 40 determines its state, and also determines whether the forklift is moving forward or backward based on Niko i-heral detection and the presence or absence of an ON signal from the back switch 34, 35. In this state judgment, the CPtJ40 determines the opening amount of the control valve based on the detection signal of the C/V opening sensor 37, and adjusts the engine rotation speed for the optimum fork lifting speed according to the opening amount. Read data. CPU40
The actuator drive circuit 4 uses this as a drive control signal.
2 and increase the engine speed. Therefore, similarly to the above, the fork lowering speed is controlled based on the detection signal of the C/V opening sensor 37.

Further, while the CPU 40 controls the engine speed based on the C/V opening sensor, it also controls the traveling speed regardless of the engine speed. At this time, the CPU 4.0 is designed to control the traveling speed according to the amount of depression of the accelerator pedal, and determines the amount of accelerator depression based on the detection signal from the accelerator opening sensor 33, and starts driving. The half-clutch state ζ of the clutch 5 corresponding to the lifting operation during cargo handling work in which the fork is moved up and down while lifting the fork.
That is, data on the pressure of the pressure fluid supplied to the clutch 5 is read from the ROM 41 and output to the solenoid drive circuit 43 as a drive control signal. When a voltage with a duty ratio based on the drive control signal is applied to the solenoid 18a of the solenoid valve 18, the pressure control valve 8 controls the pressure of the pressure fluid in the branch pipe 7, that is, the pressure of the pressure fluid supplied to the clutch 5 ( In this case, lower the pressure). With this pressure drop, the clutch 5 becomes a half-clutch state, and the traveling speed is no longer related to the engine speed based on the C/V opening sensor 37.

Then, the CPU 40 sequentially determines the traveling speed based on the detection signal from the vehicle speed sensor 31, and controls the half-clutch state of the clutch 5 to maintain the traveling speed based on the depression of the accelerator pedal.

In this manner, in cargo handling work in which the forks are moved down in the R direction while traveling, the rotation of the engine is controlled based on the detection signal from the C/V opening sensor 31 for the downward movement of the forks. The traveling speed is controlled by changing the pressure of the pressure fluid supplied to the clutch 5 based on the amount of depression of the accelerator pedal, regardless of the engine speed, and bringing the clutch 5 into a half-clutch state. Therefore,
Unlike conventional driving operations such as a half-clutch operation or an inching operation, there is no need to provide an inching pedal for the inching operation, which simplifies the driving operation and improves the safety of cargo handling operations.

Effects As detailed above, in cargo handling work in which the forks are moved up and down while the vehicle is traveling, the engine speed is controlled based on the detection signal from the C/V opening sensor for the up and down movement of the forks. On the other hand, the running speed is controlled by changing the pressure of the pressure fluid supplied to the forward/reverse clutch based on the depression of the accelerator pedal, regardless of the engine speed, by placing the clutch in a half-engaged state. It is possible to eliminate troublesome driving operations such as clutch operation and inching operation, and also eliminate the inching pedal for inching operation, simplifying the driving operation and improving the safety of cargo handling work.

[Brief explanation of drawings]

FIG. 1 is a hydraulic and electrical block circuit diagram of a forklift embodying the present invention, and FIG. 2 is a partially cutaway front view of a pressure control valve. Clutch pump 1, supply pipe 3, forward/reverse clutch switching valve 4, clutch 5, branch pipe 7, pressure control valve 8, vehicle speed sensor 31, engine rotation sensor 32, accelerator opening sensor 33, control pulp opening sensor ( C,,/V
opening sensor) 37, central processing unit (CP) as each means
U) 40, actuator drive circuit 42, solenoid drive circuit 43, throttle actuator 44. Patent applicant Toyota Industries Corporation Fujitsu Corporation Agent Patent attorney On1) Hironobu

Claims (1)

[Scope of Claims] A cargo handling pump and a clutch pump that are directly driven by an engine and supply pressurized fluid to a lift cylinder and a forward/reverse clutch, respectively; a throttle actuator that opens and closes a throttle valve of the engine; A pressure control valve that reduces the pressure of the pressure fluid supplied to the forward/reverse clutch via the clutch switching valve and brings the clutch into a half-clutch state; a control valve rotation sensor that detects the opening degree of a control valve that controls vertical movement; a vehicle speed sensor that detects the traveling speed of the forklift; an accelerator opening sensor that detects the amount of depression of the accelerator pedal; means for determining whether cargo handling work involves moving a fork up and down while traveling based on a detection signal from a control valve opening sensor; means for operating the throttle actuator in order to increase the rotational speed of the engine; A forklift comprising: means for operating a pressure control valve.