JPH04303396A - Control device for fork lift - Google Patents

Abstract

PURPOSE:To elevate a fork lift with simple manipulation and stop the same at a set position. CONSTITUTION:When a controller 10 outputs a flow control signal S2 in accordance with a lever manipulation signal S2 which is generated upon a tilt of a working machine lever 9a, a solenoid proportional control valve 11 feeds and discharges pressure oil to and from a lift cylinder 1 so as to elevate a fork. The height of the fork is detected by a height sensor 25, and the height of the fork upon turn-on of a memory switch SW2 is stored in memory as a stop position. When an automatic switch SW2 is turned on, the fork ascends, and when the fork comes to the stop position, the fork automatically stops. A rotational speed of an engine is detected by an engine rotational speed sensor. The higher the engine rotational speed, the earlier the deceleration is initiated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a forklift that can perform cargo handling using an electromagnetic hydraulic system, and is configured to raise a fork and automatically stop it at a preset position.

0002

2. Description of the Related Art Conventionally, as a control device for a forklift that can be operated in an electrohydraulic manner, for example, the one shown in FIG. 11 is known (Japanese Utility Model Publication No. 60-107405). 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. An oil chamber 02a for pilot operation is formed in the electromagnetic proportional control valve 02, and a pilot piston 02b is slidably fitted into the 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

When carrying out cargo handling work using a forklift, an operator operates the working machine lever 06 to lift and lower each cargo piece by piece. Among such cargo handling operations, there is work in which many loads are repeatedly lifted to the same height. Conventionally, even if the height to be lifted is the same, the operator had to tilt the work implement lever 06 in the same way every time he lifted each load. Therefore, the operator has to perform the exact same motion over and over again, causing shoulder pain and fatigue, and also reducing work efficiency.

In view of the above-mentioned prior art, the present invention provides a forklift control device in which the stop position is set in advance, and then when an automatic switch is pressed, the fork rises and automatically stops when the fork reaches the stop position. The purpose is to provide.

[0006]

[Means for Solving the Problems] The structure of the present invention that solves 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 with a value that corresponds to the value of the lever operation signal. A controller that outputs a signal, a hydraulic pump that is connected to an engine and rotates to deliver pressure oil, and an electromagnetic proportional control valve that supplies and discharges an amount of pressure oil according to the engine rotation speed and the value of the flow rate control signal. and a lift cylinder that expands and contracts to raise and lower the fork by supplying and discharging pressure oil by an electromagnetic proportional control valve, an automatic switch, a lift-up position memory switch, and a lift height that detects the height of the fork. and an engine rotation speed sensor that detects the rotation speed of the engine, the controller stores the fork position detected by the lift height sensor as a stop position when a lift lifting position storage switch is turned on, and further When the engine speed detected by the engine speed sensor becomes high, the deceleration start position is set so as to increase the interval between the deceleration start position and the stop position, which is set below the stop position, and when the automatic switch is turned on, The present invention is characterized in that the value of the flow rate control signal is controlled so as to automatically raise the fork, gradually reduce the rising speed when the fork passes the deceleration start position, and stop the fork when the fork reaches the stop position.

[0007]

[Operation] When the automatic switch is turned on, the fork automatically rises, and when the fork reaches the stop position, the fork automatically stops. The fork starts decelerating at a position before the stop position. The interval between the deceleration start position and the stop position is made longer as the engine speed is higher and the fork rising speed is faster.

[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 10. FIG. 3 is a perspective view showing an example of a forklift truck applied to this embodiment. As shown in the figure, the lift cylinder 1 is fixed to a pair of left and right outer masts 2,
As the piston rod 1a expands and contracts, a pair of left and right inner masts 3 are raised and lowered using the outer mast 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 is used to tilt the elevating section together with the outer mast 2 and the inner mast 3 forward (toward the vehicle body 7 side) and rearward (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.

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. An automatic switch SW1 is provided at the top of the work machine lever 9a (see FIG. 1). Furthermore, the joystick box 13 is provided with a lift up position storage switch SW2 and a lift down position storage switch SW3. The work machine levers 9c, 9d, and 9e are used when various attachments, such as a roll clamp and a bail clamp, are attached. 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 9a 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 lift cylinder 1 to the work equipment lever 9.
Control is performed to correspond to the manipulated variable a. The lift cylinder 1 is also equipped with a wind-up lift height sensor 25 that detects the height of the fork 4, and the lift height sensor 25 sends a lift height signal S4 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 hydraulic pump 22 is connected to the engine of the fork and operates, and sends oil from a hydraulic oil source 23 to the electromagnetic proportional control valve 11. Therefore, the pressure of the pressure oil sent from the electromagnetic proportional control valve 11 to the lift cylinder 1 corresponds to the value of the flow control signal S2, which determines the opening degree of the electromagnetic valve, and the engine rotation speed, which determines the discharge oil pressure from the hydraulic pump 22. do. The engine speed is detected by an engine speed sensor 26, and an engine speed signal S5 is sent from the sensor 26 to the controller 10.

The automatic stop control performed mainly by the controller 10 will now be explained based on FIG. 2. The CPU 120 of the controller 10 performs various calculation processes in synchronization with the clock of the clock generator 121.
Arithmetic processing is performed using software stored in the memory 122. On the other hand, the lever operation signal S1 is output from the work equipment lever 9a, the oil pressure signal S3 is output from the oil pressure sensor 17, and the lift height signal S4 is output from the lift height sensor 25.
, the engine rotation speed signal S5 outputted from the engine rotation speed sensor 26 is converted into a digital signal by the A/D converter 123 and then sent to the CPU 120. Switch signal P1 from automatic switch SW1 (this is provided on the top of work equipment lever 9a), switch signal P2 from position memory switches SW2, SW3 (this is provided on joystick box 13),
P3 connects to the CPU 12 via the interface 124.
Sent to 0. 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.

First, an outline of the operation for automatically stopping the fork 4 when raising it will be explained. First, in order to determine the position where the fork 4 is to be stopped, the work machine lever 9a is tilted to the upward side, and when the fork 4 has risen to the desired position, the work machine lever 9a is returned to the neutral position and the fork 4 is stopped. When the lift-up position memory switch SW2 is turned on at this time, a lift height signal S4 indicating the height of the fork 4 at this time is taken in, and the height of the fork 4 at this time is stored in the memory 122 as the stop position.

After the above-mentioned presetting is completed, the actual work begins. Then, when the fork 4 is below the stop position, press the automatic switch SW1 and press the work equipment lever 9a.
When the operator releases his/her hand and the automatic switch SW1 is released and the work equipment lever 9a returns to the neutral position, the fork 4 continues to rise and stops when the fork 4 reaches the stop position. A flow rate control signal S2 is sent from the controller 10 to the electromagnetic proportional control valve 11. Thus, the fork 4 automatically rises and stops at a predetermined stop position.

When automatically lifting and stopping in this way, in order to reduce the shock at the time of stopping, the lifting speed of the fork 4 is gradually decelerated from a position before the stopping position, and the fork 4 is stopped at the stopping position. I try to let them do it. For this reason, the memory 122 stores the characteristics shown in FIG. 4 and the characteristics shown in FIG. 5, and the CPU 120 uses both characteristics to issue a command to automatically raise and stop.

For example, when the stop position is H1 (see FIG. 6) and the engine speed is N1, l1 is determined as the up-stop braking distance and V1 is determined as the deceleration value. Then, as shown in FIG. 6, when the fork 4 reaches the position H1 - l1, the rising speed starts to decrease, and the rising speed of the fork 4 is reduced by V1 at predetermined intervals.
The fork 4 is stopped when it reaches H1.

The characteristics shown in FIGS. 4 and 5 are such that when the engine speed is high and the fork 4 is rising quickly, the braking distance is increased and the deceleration value is reduced to prevent shock from occurring. When the rising speed of the fork is low, the braking distance is shortened and the deceleration value is increased to achieve a quick stop.

Next, an outline of the operation for automatically stopping the fork 4 when lowering it will be explained. First, in order to determine the position where the fork 4 is to be stopped, the work machine lever 9a is pushed down to the downward side, and when the fork 4 has descended to the desired position, the work machine lever 9a is returned to the neutral position and the fork 4 is stopped. At this time, when the lift lowering position storage switch SW3 is turned on, a lift height signal S4 indicating the height of the fork 4 at this time is taken in, and the height of the fork 4 at this time is stored in the memory 122 as the stop position.

After the above-mentioned presetting is completed, the actual work begins. Then, when the fork 4 is above the stop position, while pressing the automatic switch SW1, the work equipment lever 9a is
When the fork 4 is moved to the lowering side, the fork 4 continues to descend even if the operator releases his/her hand and the automatic switch SW1 is released and the work equipment lever 9a returns to the neutral position, and when the fork 4 reaches the stop position, the fork 4 is stopped. A flow rate control signal S2 is sent from the controller 10 to the electromagnetic proportional control valve 11. Thus, the fork 4 automatically descends and stops at a predetermined stop position.

When automatically lowering and stopping in this way, in order to alleviate the shock after stopping, the descending speed of the fork 4 is gradually decelerated from a position before the stop position, and the fork 4 is stopped at the stop position. I try to let them do it. For this reason, the characteristics shown in FIG. 7 and the characteristics shown in FIG. 8 are stored in the memory 122, and the CPU 120 uses both characteristics to issue a command for automatic lowering and stopping.

For example, when the stop position is H2 (see FIG. 9) and the load is W1, l2 is determined as the lowering stop braking distance and V2 is determined as the deceleration value. and figure 9
As shown in the figure, when the fork 4 reaches the position H2 + l2, the descending speed starts to decrease, and the descending speed of the fork 4 is reduced by V2 at predetermined intervals.
The fork 4 is stopped when it reaches H2.

The characteristics shown in FIGS. 7 and 8 are such that when the load is heavy and the fork 4 descends at a high speed, the braking distance is lengthened and the deceleration value is reduced to prevent the occurrence of shock; When the speed is low, the braking distance is shortened and the deceleration value is increased to achieve a quick stop.

Next, the command operation of the controller 10 will be explained in detail with reference to FIG. Note that each operation step is marked with “
It is marked with "ST". After the control is started and initialized (ST1, ST2), when the lift-up position memory switch SW2 is turned on (ST3), the signal from the lift height sensor 25 is taken into the controller 10, and the position of the fork 4 at this time is stored. Stored as the raised position (ST
4). On the other hand, when the lift lowering position storage switch SW3 is turned on (ST5), the signal from the lift height sensor 25 is taken into the controller 10, and the current position of the fork 4 is stored as the lowering position (ST6).

In step (ST7), the work machine lever 9
It is determined whether the lift is raised, lowered, or stopped, depending on the direction in which the lever a is turned on, that is, the polarity of the lever operation signal S1. When it is determined that the lift is to be raised, if the lift control mode is not in place (ST8) and the automatic switch SW1 is not turned on (ST9), a flow rate control signal S2 corresponding to the lever operation signal S1 is outputted to perform lift raising control. do(
ST10).

[0026] At step (ST9) automatic match SW1
When the is turned on, the increase control mode is set in step (ST11), and the deceleration start position and deceleration value are calculated using the characteristics shown in FIGS. 4 and 5, and the value of the flow rate control signal S2 is calculated. is made to correspond to the value of the lever operation signal S1.

After it is determined in step (ST8) that the lift control is to be performed, if the deceleration mode is not entered (ST12) and the lift height does not reach the deceleration position (ST13), the lift continues as it is. When the lift height becomes higher than the deceleration position in step (ST13), deceleration mode is set (ST14)
.

[0028] When the deceleration mode is set (ST12,
ST14), the value (output value) of the flow rate control signal S2 is the previous value minus the deceleration value (ST15). This calculation is performed every control cycle. When the output value is larger than the stop value (ST16), this calculation control cycle is repeated and the fork moves up while decelerating. When the output value becomes smaller than the stop value (ST16), clear the increase control mode and deceleration mode (ST17),
Stop the fork.

When it is determined in step (ST7) that the lift is to be lowered, the lowering control mode is not in effect (ST18);
When automatic switch SW1 is not turned on (ST19
) has a flow rate control signal S according to the lever operation signal S1.
2 to perform lift lowering control (ST20).

[0030] In step (ST19) automatic switch S
When W1 is turned on, the lowering control mode is set in step (SW21), the deceleration start position and deceleration value are calculated using the characteristics shown in FIGS. 7 and 8, and the flow rate control signal S2 is also calculated. The value corresponds to the value of the lever operation signal S1.

After the lowering control is determined in step (ST18), if the deceleration mode is not set (ST22) and the lift height does not reach the deceleration position (ST23), the lowering continues as it is. When the lift height becomes lower than the deceleration position in step (ST23), deceleration mode is set (ST24).
).

[0032] When the deceleration mode is set (ST22,
ST24), the value (output value) of the flow rate control signal S2 is the previous value minus the deceleration value (ST25). This calculation is performed every control cycle. When the output value is larger than the stop value (ST26), this calculation control cycle is repeated and the fork moves up while decelerating. When the output value becomes smaller than the stop value (ST26), clear the lowering control mode and deceleration mode (ST27),
Stop the fork.

[0033]

According to the present invention, as specifically explained above in conjunction with the embodiments, the stop position of the fork can be set at an arbitrary height, and when the fork is to be raised, the fork can be moved by turning on the automatic switch. It automatically rises and stops when it reaches the stopping position, so even if you have to lift many loads to the same height many times, you can complete the task with the simple action of turning on an automatic switch. . Thus, operator fatigue is also reduced.

Furthermore, since the rising speed of the fork is gradually reduced from a position before the stop position, the fork can be stopped without shock. Moreover, the rising speed of the fork is determined from the engine speed, and the faster the rising speed, the earlier the fork starts decelerating to achieve a smooth stop.

[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 engine speed and up-stop braking distance.

FIG. 5 is a characteristic diagram showing the relationship between engine speed and deceleration value.

FIG. 6 is a characteristic diagram showing the state of raising and stopping the fork.

FIG. 7 is a characteristic diagram showing the relationship between load and lowering stop braking distance.

FIG. 8 is a characteristic diagram showing the relationship between load and deceleration value.

FIG. 9 is a characteristic diagram showing the lowering and stopping states of the fork.

FIG. 10 is a flow diagram showing the operation of the present invention.

FIG. 11 is a hydraulic circuit showing a conventional control device for an electrohydraulic forklift.

[Explanation of symbols]

1 Lift cylinder 1a Piston rod 4 Fork 9a Work machine lever 10 Controller 11 Solenoid proportional control valve 16 Hydraulic pipeline 17 Oil pressure sensor 24 Automatic lowering switch 25 Lift height sensor 26 Engine speed sensor 120 CPU S1 Lever operation signal S2 Flow rate control signal S3 Hydraulic signal S4 Lift height signal S5 Engine speed signal SW1 Automatic switch

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 work equipment lever that is connected to and rotates with an engine. A hydraulic pump that sends out pressure oil, an electromagnetic proportional control valve that supplies and discharges an amount of pressure oil according to the engine speed and the value of the flow rate control signal, and an electromagnetic proportional control valve that supplies and discharges pressure oil and expands and contracts. A forklift that has a lift cylinder that raises and lowers the fork, an automatic switch, a lift-up position memory switch, a lift height sensor that detects the height of the fork, and an engine rotation speed sensor that detects the engine rotation speed. The controller stores the fork position detected by the lift height sensor when the lift-up position memory switch is turned on as the stop position, and further stops when the engine speed detected by the engine speed sensor becomes high. The deceleration start position is set so that the interval between the deceleration start position and the stop position is longer than the deceleration start position, and when the automatic switch is turned on, the fork is automatically raised, and when the fork passes the deceleration start position, the rising speed is increased. A control device for a forklift truck, characterized in that the value of a flow control signal is controlled so as to gradually decelerate the fork and stop the fork when the fork reaches a stop position.