JPH04303392A - Control device for industrial vehicle - Google Patents

Abstract

PURPOSE:To reduce a shock when a piston rod of a working machine cylinder comes to its stroke end. CONSTITUTION:A controller outputs a flow control signal S1 in accordance with a lever manipulation signal S1 which is issued when a working machine lever 9b tilts, and accordingly, pressure oil is fed from a solenoid proportional control valve 11 to a tilt cylinder 8 so that a fork tilts. When the piston rod 8a of the tilt cylinder 8 approaches its stroke end, a stroke end sensor 25 outputs a stroke end signal S4 to a controller 10 which therefore gradually reduces the value of the flow control signal S1, thereby the moving speed of the piston rod 8 is gradually decreased.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a control device for an industrial vehicle that can operate cargo handling operations using an electromagnetic hydraulic system, and is designed to reduce shock even when the piston rod of a work machine cylinder reaches the end of its stroke. .

0002

2. Description of the Related Art Conventionally, as a control device for a forklift that can be operated in an electrohydraulic manner, the one shown in FIG. 6, for example, is known (Japanese Utility Model Publication No. 107405/1983). As shown in the figure, pressure oil from a hydraulic pump 01 is divided into an electromagnetic proportional control valve 02 and a power steering control valve (not shown) via a conduit 07. The electromagnetic proportional control valve 02 is formed with an oil chamber 02a for pilot operation.
A pilot piston 02b is slidably fitted into this oil chamber 02a. This pilot piston 02b is connected to a spool 02c that switches the oil path. The pilot piston 02b and the spool 02c are connected to springs 03a and 03b, respectively, and are held at a neutral position without hydraulic pressure. Pilot piston 02
Pilot inflow pipes 02d and 02e are provided on both sides of b, respectively. Pilot inflow pipe 02d,0
2e is connected to a power steering hydraulic system via electromagnetic on-off valves 02f and 02g. Therefore, by opening and closing the electromagnetic on-off valves 02f and 02g, the pilot piston 02b and the spool 02c move from side to side in the figure. When the spool 02c moves, pressure oil is supplied to and discharged from the work machine cylinder 04 via the spool 02c, and the work machine cylinder 04 expands and contracts. Depending on the movement position of the spool 02c, the flow rate of the pressure oil supplied to and discharged from the working machine cylinder 04 is adjusted, and its lifting speed is adjusted. Work machine cylinder 04
Various types of forks, such as those that raise and lower a fork (not shown) and those that tilt, can be used.

On the other hand, the opening and closing of the electromagnetic on-off valves 02f and 02g are controlled by a flow rate control signal from a controller 05. The controller 05 outputs a flow rate control signal in response to a lever operation signal from the work equipment lever 06. The working machine lever 06 is equipped with a potentiometer and outputs a lever operation signal according to the tilt angle and the tilt direction. The work implement lever 06 does not output any output in the neutral position. Therefore,
By operating the work equipment lever 06, the electromagnetic on-off valve 02f
, 02g is opened and closed, pressure oil is supplied and discharged from the electromagnetic proportional control valve 02 to the work machine cylinder 04, and the work machine cylinder 04 expands and contracts to raise and lower the fork, tilt, etc., and adjust the inclination angle of the work machine lever 06. When adjusted, work machine cylinder 04
The flow rate of pressure oil is adjusted, and the lifting speed etc. can be freely controlled.

0004

By the way, when the piston rod of the work machine cylinder 04 is moved at high speed by tilting the work machine lever 06 significantly, a large shock occurs when the piston rod reaches the stroke end. This shock can shorten the life of mechanical parts, and in the worst case, can cause the forklift to overturn or cause cargo to fall.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a control device for an industrial vehicle that does not cause a shock even when the piston rod of a working machine cylinder reaches its stroke end.

[0006]

[Means for Solving the Problems] The structure of the present invention to solve the above problems includes a work equipment lever that outputs a lever operation signal with a value corresponding to the inclination angle, and a flow rate control signal with a value corresponding to the value of the lever operation signal. An industry that has a controller that outputs a flow control signal, an electromagnetic proportional control valve that supplies and discharges an amount of pressure oil according to the value of a flow control signal, and a work equipment cylinder that expands and contracts when pressure oil is supplied and discharged by the electromagnetic proportional control valve. The vehicle includes a stroke end sensor that detects that the piston rod of the working machine cylinder approaches the stroke end, and the controller detects that the piston rod approaches the stroke end, and the controller detects that the piston rod approaches the stroke end. It is characterized by gradually decreasing the value of the flow rate control signal.

[0007]

[Operation] When the piston rod of the working machine cylinder approaches the stroke end, this is detected by the sensor, and the value of the flow rate control signal gradually decreases, and the moving speed of the piston rod decreases and stops.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings. An embodiment of the present invention is shown in FIGS. 1 to 5. FIG. 3 is a perspective view showing an example of a forklift truck applied to this embodiment, and in this embodiment, the present invention is applied to the tilt cylinder 8. As shown in the figure, the lift cylinder 1 is fixed to a pair of left and right outer masts 2, and as the piston rod 1a expands and contracts, the pair of left and right inner masts 3 is raised and lowered using the outer masts 2 as a guide. At this time, the outer mast 2 is fixed to the vehicle body 7 in front of the vehicle body 7. As a result, as the inner mast 3 moves up and down, an elevating section consisting of a bracket 5 suspended from a chain and a fork 4 for directly loading cargo moves up and down. The tilt cylinder 8, together with the outer mast 2 and the inner mast 3, moves the elevating section forward (toward the side opposite to the vehicle body 7) and backward (toward the vehicle body 7).
This is for tilting toward the vehicle body 7 side). That is, it tilts forward when unloading, and tilts backward when lifting or transporting cargo, thereby maintaining good workability and ensuring safety. This tilt cylinder 8 has a stroke end sensor 25 (Fig. 1,
(see Figure 3).

The work equipment levers 9a and 9b are operated by an operator to control the operation of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11, and are used to perform an emergency stop. It is housed in a joystick box 13 along with a safety switch 12 for carrying out the operation. Work equipment levers 9c, 9d, 9
e is various attachments, such as roll clamps,
This is for when a bail clamp or the like is installed. The seat switch 14 is a switch that operates when an operator sits on the driver's seat 15, and its output signal is output to the controller 10.

FIG. 1 is a block diagram showing an example of a control device for the forklift. As shown in the figure, the work implement lever 9b is formed of a potentiometer, and sends a lever operation signal S1 whose current value is proportional to the amount of operation to the controller 10. The controller 10 sends out a flow rate control signal S2 that adjusts the opening degree of the spool of the electromagnetic proportional control valve 11 based on the lever operation signal S1. The electromagnetic proportional control valve 11 moves the spool in proportion to the magnitude of the flow rate control signal S2, controls the flow rate of the pressure oil flowing through the hydraulic line 16, and adjusts the operating speed of the tilt cylinder 8 to the work equipment lever 9.
Control is performed to correspond to the manipulated variable b. The tilt cylinder 8 is also equipped with a stroke end sensor 25 that detects when the piston rod 8a of the tilt cylinder 8 approaches the stroke end. piston rod 8
When a approaches the stroke end, a stroke end signal S4 is sent from the stroke end sensor 25 to the controller 10.

The oil pressure sensor 17 is disposed in the oil pressure line 16 and sends out an oil pressure signal S3 representing the oil pressure in the oil pressure line 16. The controller 10 processes the oil pressure signal S3 to calculate the load acting on the lift cylinder 1. Further, the controller 10 is operated by being supplied with power from a battery 21 when a starter switch 20, which is housed in a console box 19 together with a warning light 18, is turned on, and when the safety switch 12 is operated and the seat switch 14 is not operated. When the person is away from the seat, the current value of the flow rate control signal S2 is set to zero, and the opening degree of the electromagnetic proportional control valve 11 is controlled to be zero.

The shockless stop control performed mainly by the controller 10 will now be described with reference to FIGS. 1 and 2. In FIG. 2, the CPU 120 of the controller 10
performs various arithmetic processing in synchronization with the clock of the clock generator 121, and performs the arithmetic processing using software stored in the memory 122. On the other hand, the lever operation signal S1 output from the work implement lever 9b and the stroke end signal S4 output from the stroke end sensor 25 are converted into digital signals by the A/D converter 123 and then sent to the CPU 120. The flow control signal S2 is sent from the electromagnetic valve drive circuit 125 to the electromagnetic proportional control valve 11 under the control of the CPU 120. Note that 124 is a power supply circuit.

[0013] When the work machine lever 9b is lowered, the lever operation signal S
1, the controller 10 outputs a flow rate control signal S2 proportional to the value of the lever operation signal S1 (which corresponds to the inclination angle of the lever 9b), and the tilt cylinder 8 is actuated to move the fork. 4 tilts. In other words, as shown in FIG. 4, when the opening degree of the lever 9b is large, the value of the signal S2 becomes large as shown by the characteristic α,
When the opening degree of the lever 9b is small, the value of the signal S2 becomes small as shown by the characteristic β.

When the work equipment lever 9b is kept tilted, the piston rod 8a of the tilt cylinder 8 approaches the end of its stroke, and the stroke end sensor 25 outputs a stroke end signal S4. When the stroke end signal S4 is output, even if the inclination angle of the work equipment lever 9b is the same and the value of the lever operation signal S1 remains constant, as shown in the shockless control region of FIG.
The controller 10 gradually decreases the value of the flow rate control signal S2. Therefore, the moving feed rate of the piston rod 8a gradually decreases as it approaches the stroke end, and the piston rod 8a gradually decreases as it approaches the stroke end.
Even if a reaches the stroke end, the shock will be small.

Next, the procedure of shockless stop control will be explained based on FIG. 5. Note that each operation step is marked with the symbol “
Add "ST". After the control is started and initialized (ST1, ST2), the closed state of the work implement lever 9b is determined (ST3). When the lever 9b is tilted backward, the flow rate control signal S2 performs tilt backward control.
is output (ST4), and when the flow rate control signal S2 is in neutral, the value of the flow rate control signal S2 is set to zero (ST5).

When the shockless control is not in progress (ST6), is not within the shockless control region (ST7), and is not in the shockless control region (ST8), the flow rate has a value corresponding to the value of the lever operation signal S1. Control signal S2
Output.

If it is determined in step (ST8) that the shockless control region has been entered, a shockless control flag is set, and the value of the flow rate control signal S2 corresponding to the value of the lever operation signal S1 is memorized as the previous value (ST10). )
. When it is determined in step (ST6) that shockless control is being performed, the value obtained by subtracting the deceleration value from the previous value is set as the value of the current signal S2 (ST11). The calculation in step (ST11) is repeated for each control cycle, and the output S2
When the output value of becomes smaller than the final value (see Figure 4),
ST12), clear the shockless control flag and make the value of output S2 the final value.

If the lever 9b is turned on in step (ST7) when it is within the shockless control region, the value of the output S2 is set as the final value.

In the above embodiment, the tilt cylinder 8 is subjected to shockless control, but the lift cylinder 1 can also be subjected to shockless control using a similar configuration. Further, the present invention can be applied not only to forklifts but also to cylinders of other industrial vehicles such as shovel loaders.

[0020]

According to the present invention, as specifically explained above in conjunction with the embodiments, when the piston rod of the working machine cylinder approaches the stroke end, the moving speed of the piston rod is reduced, so that the piston rod Even when the stroke end is reached, the shock becomes smaller. Therefore, damage to the machine can be prevented and safe work can be ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a perspective view showing a forklift to which the present invention is applied.

FIG. 4 is a characteristic diagram showing the relationship between cylinder stroke and flow rate control signal S2.

FIG. 5 is a flowchart diagram showing the operation of the present invention.

FIG. 6 is a hydraulic circuit showing a conventional control device for an electrohydraulic forklift.

[Explanation of symbols]

1 Lift cylinder 1a Piston rod 4 Fork 9b Work machine lever 10 Controller 11 Solenoid proportional control valve 16 Hydraulic pipeline 17 Oil pressure sensor 24 Automatic lowering switch 25 Stroke end sensor 120 CPU S1 Lever operation signal S2 Flow rate control signal S3 Hydraulic signal S4 Stroke end signal

Claims (1)

[Claims] Claim 1: A work equipment lever that outputs a lever operation signal with a value corresponding to a tilt angle, a controller that outputs a flow rate control signal with a value that corresponds to the value of the lever operation signal, and a controller that outputs a flow rate control signal with a value that corresponds to the value of the lever operation signal. In an industrial vehicle having an electromagnetic proportional control valve that supplies and discharges a certain amount of pressure oil, and a work equipment cylinder that expands and contracts when pressure oil is supplied and discharged by the electromagnetic proportional control valve, the piston rod of the work equipment cylinder reaches the end of its stroke. An industrial vehicle comprising a stroke end sensor that detects when the piston rod approaches the stroke end, and wherein the controller gradually decreases the value of the flow rate control signal when the stroke end sensor detects that the piston rod approaches the stroke end. control device.