JPH10330095A - Tilt control device of forklift truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select control in response to a loading work by a means by which either one of a first automatic horizontal control means for automatically stopping a tilt at the horizontal position of a forklift truck when a horizontal stop operation is carried out or a second automatic horizontal control means for automatically stopping the tilt regardless of the horizontal stop operation can be selected. SOLUTION: An automatic horizontal control selection switch 32 for selecting either one of two automatic horizontal control means is connected to the input filter 26 of the input side of a controller 20. When both of a loading work in which the stop of a forklift truck in a horizontal state is necessary and the loading work in which the stop of the forklift truck in the horizontal state is not necessary are carried out at random, the first automatic horizontal control is selected by the automatic horizontal control selection switch 32. Then, when the tilt of a mast 1 is stopped per the horizontal state of the forklift truck, the second automatic horizontal control is selected by the automatic horizontal control selection switch 32 when the loading work with a good work efficiency is carried out. Thereby, the work efficiency in response to the loading work can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt control device for a forklift, and more particularly to a tilt control device for automatically stopping the tilt of a mast at a position where the fork is horizontal.

[0002]

2. Description of the Related Art Conventionally, a tilt control device for a forklift automatically adjusts a tilt of a mast at a position where the fork is in a horizontal state when the tilt lever is operated while pressing a push button switch provided on the tilt lever. In some cases, the mast tilt is automatically stopped every time the fork becomes horizontal regardless of the operation of the push button switch as described above.

[0003]

Among the conventional forklift tilt control devices, the former automatically stops the mast tilt at a position where the fork is in a horizontal state only when a push button switch is pressed. Can be
The work efficiency is extremely high when both the cargo handling work in which the forks need to be stopped horizontally and the cargo handling work in which the forks need not be stopped horizontally are performed at random. On the other hand, the latter can automatically stop the tilt of the mast every time the fork is brought into a horizontal state, so that the work efficiency is extremely high in cargo handling work in which it is necessary to keep the fork in a horizontal state every time. Accordingly, an object of the present invention is to improve the efficiency of cargo handling work by providing a forklift tilt control device capable of selecting one of the two tilt controls according to the cargo handling work.

[0004]

According to a first aspect of the present invention, there is provided a first automatic level control means for automatically stopping a tilt of a mast at a position where a fork becomes horizontal when a horizontal stop operation is performed; Second automatic level control means for automatically stopping the tilt of the mast every time the fork becomes horizontal irrespective of the horizontal stop operation; and any one of the first automatic level control means and the second automatic level control means. And selecting means for selecting whether or not.

If the forklift tilt control device according to the first aspect of the present invention is used, the first automatic level control means and the second automatic level control means can be selected in accordance with the cargo handling operation. It is possible to perform automatic leveling control suitable for the vehicle, thereby improving the efficiency of cargo handling work.

According to a second aspect of the present invention, in the tilt control apparatus for a forklift according to the first aspect, a position at which the fork becomes horizontal by the first automatic horizontal control means and the second automatic horizontal control means. When the tilt of the mast is automatically stopped at the time of tilting the mast, the tilting lever is tilted forward or backward based on a signal from a switch that detects a forward tilting or a backward tilting operation of the tilting lever operated when tilting the mast. When the tilt angle of the mast is recognized based on a signal from a tilt angle detector that detects the tilt angle of the mast, and the tilt angle matches a value corresponding to the horizontal state of the fork, This is to control closing of an electromagnetic valve provided in a hydraulic circuit of a tilt cylinder for tilt-driving the mast.

According to the forklift tilt control device of the present invention, when the tilt-reversing operation of the tilt lever is recognized, the signal from the tilt angle detector for detecting the actual tilt angle of the mast is provided. , The fork can be stopped at the horizontal position, so that the fork horizontal stop position accuracy is improved.

According to a third aspect of the present invention, in the tilt control apparatus for a forklift according to the second aspect, the solenoid valve is a proportional electromagnetic flow rate control valve, and the proportional valve is provided before the tilt angle at which the fork becomes horizontal. A tilt speed variable control means is provided to reduce the tilt speed of the mast by narrowing the opening of the electromagnetic flow control valve, and to close and control the proportional electromagnetic flow control valve at a position where the tilt angle is horizontal. That is.

According to the forklift tilt control apparatus of the present invention, the opening of the proportional electromagnetic flow control valve is reduced from just before the tilt angle at which the fork becomes horizontal to reduce the tilt speed of the mast. Because it can be
The horizontal stop position accuracy can be further improved.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of a tilt cylinder in a forklift. As shown in the figure, a tilt cylinder 2 for tilting a mast 1 for guiding the fork up and down forward and backward includes a manual tilt spool 4 as a direction switching valve provided in a cargo control valve 3. The tilt spool 4 is connected to the hydraulic pump 5 via a hydraulic pump 5 so as to be expanded and contracted by a switching operation of the tilt spool 4.

Tilt spool 4 and tilt cylinder 2
An oil passage 6 connecting the rod-side oil chamber is provided with a proportional electromagnetic flow control valve 7 (hereinafter, referred to as an electromagnetic valve) as a control valve for stopping the mast 1 at a predetermined position within the tilting range. . The solenoid valve 7 includes a flow rate adjusting unit 8 and a solenoid unit 9 for generating pilot pressure. The electromagnetic pressure generated in the solenoid unit 9 (proportional to the current flowing through the coil) controls the pilot pressure acting on the flow rate adjusting unit 8. The flow rate is controlled by the balance between the pilot pressure and the spring force.
The amount of displacement (opening) of the valve is determined so that a flow rate proportional to the current can be obtained.

The pilot pressure is such that the pressure oil discharged from the hydraulic pump 5 is introduced directly through the pilot line 10, and the pilot line 10 is provided with a pressure reducing valve 11, which acts on the flow control unit 8. Pilot pressure is specified.

A pilot check valve 12 for preventing leakage is provided in the oil passage 6 downstream of the solenoid valve 7 (toward the tilt cylinder 2). The opening operation is performed by the pilot pressure controlled by the solenoid unit 9 of the first embodiment. In FIG. 1, reference numeral 13 denotes an oil tank, 14 denotes a flow dividing valve, and 15 denotes a power steering valve.

FIG. 2 is a control block diagram for controlling the tilt cylinder 2. As shown in FIG. 2, a controller 20 having a computer CPU serving as a control center is provided.
Is provided. Further, a push button type switch 2 is provided at the upper end of the tilt lever 4a operated when the mast 1 is tilted by the expansion and contraction operation of the tilt cylinder 2.
1 is attached. When the switch 21 is not pressed, a voltage of 5 volts is input to the computer CPU via the switch 21 as shown in FIG. 3, and when pressed, the voltage input to the computer CPU is reduced. Drop to 0 volts. The switch 21 functions as a horizontal stop switch for automatically stopping the tilt of the mast 1 at the fork horizontal position when the tilt lever-4a is operated in a pressed state.

At the base end of the tilt lever-4a, a forward tilt detecting switch 22 which is activated when the tilt lever 4a is tilted forward to tilt the mast 1 forward, and a mast 1 are provided. A rearward tilt detection switch 23 that is activated when the tilt lever-4a is tilted rearward for tilting in the rearward tilt direction is attached. As shown in FIG. 4, when the tilt lever-4a is in the neutral state, a voltage of 5 volts is input to the computer CPU via the forward tilt detection switch 22, and the tilt tilt lever-4a is turned on.
Is operated forward, the voltage input to the computer CPU drops to 0 volts. As shown in FIG. 5, when the tilt lever-4a is in the neutral state, a voltage of 5 volts is applied to the computer CP via the backward tilt detection switch 23.
When U is input to U and the tilt lever-4a is tilted backward, the voltage input to the computer CPU drops to 0 volt.

A rotary potentiometer 24 is attached to the base end of the tilt cylinder 2. The potentiometer 24 outputs a voltage signal proportional to the degree of expansion and contraction of the tilt cylinder 2, that is, the tilt angle of the mast 1, within the range of 0 to 5 volts as shown in FIG. In order to output a voltage signal proportional to the tilt angle of the mast 1 from the potentiometer 24, a projection 2A is attached to the side of the tilt cylinder 2, and this projection 2A is clamped by a U-shaped portion at the tip. A rotating body 2B whose base end is connected to the shaft of the potentiometer 24 is provided. With this configuration, the amount of rotation of the mast 1 that tilts due to the expansion and contraction of the tilt cylinder 2 matches the amount of rotation of the projection 2A, so that the rotating body 2B rotates the shaft of the potentiometer 24 with the rotation of the projection 2A. Then, a voltage signal proportional to the tilt angle of the mast 1 is output from the potentiometer 24.

The push button type switch 21, the forward tilt detecting switch 22, the rear tilt detecting switch 23, and the potentiometer 24 are connected to the input side of the controller 20. The input side of the controller 20 has an input filter 25,
The input filter 25 is connected to an analog / digital converter 27, and the input filter 26 is connected to an input port 28. Note that this input port
G is a digital signal (Low, High) for the 0 volts and 5 volts via a push button type switch 21, a forward tilt detecting switch 22, and a backward tilt detecting switch 23.
Is provided for input to the computer CPU. The analog-to-digital converter 27 is provided to convert an analog voltage output from the potentiometer 24 into a digital signal and input the digital signal to the computer CPU.

The controller 20 is provided with a solenoid drive circuit 30. The solenoid drive circuit 30 is connected to the solenoid 9 of the solenoid valve 7. The solenoid drive circuit 30 is a computer CPU
Is connected to an output port 31 provided on the solenoid valve, and supplies an exciting current to the solenoid unit 9 based on a control signal output from the computer CPU via the output port 31.

The computer CPU has a first automatic horizontal control for automatically stopping the tilt of the mast 1 at the fork horizontal position when the tilt lever-4a is operated while the push button type switch 21 is pressed. And the above switch 2
There are two automatic horizontal control means of a second automatic horizontal control for automatically stopping the tilt of the mast 1 every time the tilt lever-4a is operated and the fork becomes horizontal irrespective of the operation of the first operation.

The input filter 26 is connected to an automatic horizontal control selection switch 32 for selecting one of the two automatic horizontal control means. The automatic horizontal control selection switch 32 is an alternate type switch. When the switch is pressed, the pressed state is held, and the pressed state is released by the pressing again. In the pressed state, the signal via the automatic horizontal control selection switch 32 is Low, and when the pressed state is released, the signal via the automatic horizontal control selection switch 32 is High. Low signal by pressing operation of automatic horizontal control selection switch 32, re-pressing operation, or Hi signal
When the gh signal is input to the computer CPU through the input filter 26 and the input port 28, the computer C
The PU selects the first automatic horizontal control when the High signal is input, and selects the second automatic horizontal control when the Low signal is input. The automatic horizontal control selection switch 32 is mounted near the tilt lever-4a. The controller 20 has a DC power supply 33 that outputs a voltage of 5 volts.
Is provided.

In the tilt control apparatus for a forklift constructed as described above, both the cargo handling work in which the fork needs to be stopped in the horizontal state and the cargo handling work in which the fork does not need to be stopped in the horizontal state. Is performed at random, the automatic horizontal control selection switch 32 selects the first automatic horizontal control. When the first automatic horizontal control is selected and the tilt lever-4a is operated in a state where the push button type switch 21 is pressed, the computer CPU causes the forward tilt detection switch 22 and the rear tilt detection The solenoid drive circuit 30 recognizes the current tilt angle based on the voltage output from the potentiometer 24 while recognizing the forward tilt or backward tilt operation of the tilt lever-4a based on the signal via the switch 23. A drive signal is output, a drive current is supplied from the solenoid drive circuit 30 to the solenoid unit 9 to open a hydraulic circuit for tilt, and the tilt cylinder 2 is expanded and contracted to tilt the mast 1 in a direction in which the forks become horizontal. . When the output voltage of the potentiometer 24 becomes a value corresponding to the tilt angle of the mast 1 at which the fork is in a horizontal state, the computer CPU stops outputting a drive signal to the solenoid drive circuit 30 and drives the solenoid. The drive current from the circuit 30 to the solenoid unit 9 is stopped to close the tilt hydraulic circuit, the drive of the tilt cylinder 2 is stopped, and the mast 1 is stopped.
Stop tilting. When the tilt lever-4a is operated without pressing the push-button switch 21, the computer CPU determines that the output voltage of the potentiometer 24 is in the horizontal level in the fork state. The tilt of the mast 1 is continued without stopping the drive of the tilt cylinder 2 until the tilt lever-4a is in the neutral state, even when the value of the tilt cylinder 2 is reached.

Next, when the tilt of the mast 1 is stopped every time the fork is brought into a horizontal state, the second automatic horizontal control is selected by the automatic horizontal control selection switch 32 when the cargo handling work with high working efficiency is performed. . When the second automatic horizontal control is selected, the computer CPU operates the forward tilt detection switch 2
2. Recognizing the forward or backward tilt operation of the tilt lever-4a based on a signal via the backward tilt detection switch 23, and recognizing the current tilt angle based on the voltage output from the potentiometer 24, and solenoid. A drive signal is output to the drive circuit 30, a drive current is supplied from the solenoid drive circuit 30 to the solenoid unit 9, a hydraulic circuit for tilt is opened, and the tilt cylinder 2 is expanded and contracted to form a fork.
Tilt the mast 1 in the direction in which And
When the output voltage of the potentiometer 24 becomes a value corresponding to the tilt angle of the mast 1 at which the fork is in a horizontal state, the computer CPU stops outputting the drive signal to the solenoid drive circuit 30 and the solenoid drive circuit 30 Then, the supply of the drive current to the solenoid unit 9 is stopped, the tilt hydraulic circuit is closed, the drive of the tilt cylinder 2 is stopped, and the tilt of the mast 1 is stopped. Therefore, the tilt of the mast 1 is automatically stopped every time the tilt lever 4a is operated and the mast 1 is tilted to a position where the fork becomes horizontal regardless of the operation of the push button type switch 21.

As described above, according to the forklift tilt control device, the first automatic horizontal control and the second automatic horizontal control can be selected according to the cargo handling work, so that the work efficiency of the cargo handling work is improved. Can be improved. Also, since the potentiometer 24 can detect the actual tilt angle of the mast 1 at which the fork is horizontal,
The horizontal stop position accuracy of the fork is increased.

In this embodiment, since the proportional electromagnetic flow control valve 7 is used as an electromagnetic control valve for stopping the mast 1 at a predetermined tilt position, the computer CPU controls the operation of the tilt lever-4a. Separately, while recognizing the output voltage of the potentiometer 24, the tilting speed of the mast 1 is proportionally reduced by controlling the opening of the valve 7 proportionally before the fork becomes horizontal. , The precision of the tilt stop position of the mast 1 is increased, and the precision of the stop at the position where the fork is horizontal can be further increased.

[0025]

According to the forklift tilt control apparatus of the first aspect of the present invention, the first automatic tilt for automatically stopping the mast tilt at a position where the fork becomes horizontal when the horizontal stop operation is performed. Either the horizontal control means or the second automatic horizontal control means for automatically stopping the tilt of the mast every time the fork becomes horizontal regardless of the horizontal stop operation can be selected according to the cargo handling operation. Therefore, there is an effect that the cargo handling efficiency can be improved.

According to the forklift tilt control device of the second aspect of the present invention, the signal from the tilt angle detector for detecting the actual tilt angle of the mast when recognizing the forward tilt or the backward tilt operation of the tilt lever is recognized. Therefore, the fork can be stopped at the horizontal position based on the fork, so that the fork horizontal stop position accuracy is improved.

According to the forklift tilt control device of the third aspect of the present invention, the opening of the proportional electromagnetic flow control valve is reduced before the tilt angle at which the fork becomes horizontal, thereby reducing the mast tilt speed. Because it can be
There is an effect that the horizontal stop position accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a tilt cylinder in a forklift.

FIG. 2 is a block diagram of a forklift tilt control device.

FIG. 3 is an output signal characteristic diagram of the automatic horizontal switch.

FIG. 4 is an output signal characteristic diagram of a forward tilt detection switch.

FIG. 5 is an output signal characteristic diagram of a backward tilt detection switch.

FIG. 6 is an output signal characteristic diagram of a potentiometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mast 2 Tilt cylinder 3 Control valve for cargo handling 4a Tilt lever 7 Solenoid valve 9 Solenoid unit 20 Controller 21 Push button type switch 32 Automatic level control selection switch

Claims (3)

[Claims] 1. A first automatic level control means for automatically stopping the tilt of a mast at a position where the fork becomes horizontal when a horizontal stop operation is performed, and the fork is leveled irrespective of the horizontal stop operation. A second automatic level control means for automatically stopping the tilt of the mast every time the mast tilts, and a selection means for selecting one of the first automatic level control means and the second automatic level control means A lift control for the lift. 2. When the tilt of the mast is automatically stopped at the position where the fork is horizontal by the first automatic horizontal control means and the second automatic horizontal control means, A tilt angle detector for recognizing a forward or backward tilt operation of the tilt lever based on a signal from a switch for detecting a forward or backward tilt operation of the operated tilt lever, and detecting a tilt angle of the mast. The tilt angle of the mast is recognized based on the signal of the mast, and when the tilt angle matches a value corresponding to the horizontal state of the fork, the solenoid valve provided in the hydraulic circuit of the tilt cylinder that tilts the mast is closed. The tilt control device for a forklift according to claim 1, which controls the tilt. 3. The solenoid valve is a proportional solenoid type flow control valve, and the tilting speed of the mast is reduced by narrowing the opening of the proportional solenoid type flow control valve from just before a tilt angle at which a fork becomes horizontal. 3. A fork according to claim 2, further comprising a tilt speed variable control means for closing and controlling said proportional electromagnetic flow rate control valve at a position where said tilt angle is horizontal.
Clift tilt control device.