JPH06127899A - Controller for fork lift - Google Patents

Abstract

PURPOSE:To raise a fork of a fork lift with the simple operation, and prohibit the automatic rise of the fork at the time of disconnection. CONSTITUTION:When an automatic rise switch 24 is turned on during the time when a working machine lever 9a is shifted at a neutral position, the flow quantity control signal S2 for commanding rise is output, and a lift cylinder is extended to raise the fork. A fork load is detected by a hydraulic sensor, and since a value of the flow quantity control signal S2 is selected in response to this load, the fork rises along the nearly same characteristics even in the case where a different load is detected. When a position sensor 25 detects the fork, the fork is stopped. At the initial time of the rise, the rising speed of the fork is increased gradually, and at the latter time of the rise, the rising speed is decreased gradually for stop. When a signal line 25a for position sensor 25 is disconnected, even if the automatic rise switch 24 is tuned on, the automatic rise is prohibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forklift control device capable of operating a cargo handling operation by an electromagnetic hydraulic system, and is devised so that the fork lift can be easily operated.
Also, in the case of a wire breakage failure, automatic raising is prohibited.

[0002]

2. Description of the Related Art Conventionally, as a control device for a forklift that can be operated electromagnetically, for example, the one shown in FIG. 10 is known (Japanese Utility Model Laid-Open No. 60-107405). As shown in the figure, the pressure oil from the hydraulic pump 01 is divided into an electromagnetic proportional control valve 02 and a control valve (not shown) for power steering (not shown) via a conduit 07. The electromagnetic proportional control valve 02 has an oil chamber 02a for pilot operation.
Is formed in the oil chamber 02a.
2b is slidably fitted. The pilot piston 02b is connected to a spool 02c that switches the oil passage. Pilot piston 02b and spool 02
c is connected to the springs 03a and 03b, respectively, and is held in the neutral position without hydraulic pressure. On both sides of the pilot piston 02b, the pilot inflow conduit 02d,
02e are provided. The pilot inflow conduits 02d and 02e are connected to a hydraulic system for power steering via electromagnetic opening / closing valves 02f and 02g. Therefore, by opening and closing the solenoid on-off valves 02f and 02g,
The pilot piston 02b and the spool 02c move left and right in the figure. When the spool 02c moves, pressure oil is supplied to and discharged from the working machine cylinder 04 via the spool 02c, and the working machine cylinder 04 expands and contracts. The flow rate of the pressure oil supplied to and discharged from the working machine cylinder 04 is adjusted by the moving position of the spool 02c, and the ascending / descending speed thereof is adjusted. As the working machine cylinder 04, various ones such as one for raising and lowering a fork (not shown) and one for tilting it can be used.

On the other hand, the opening / closing of the solenoid opening / closing valves 02f and 02g is controlled by a flow rate control signal from the controller 05. The controller 05 outputs a flow rate control signal in response to a lever operation signal from the work implement lever 06. The work implement lever 06 includes 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 at the neutral position. Therefore,
By operating the work equipment lever 06, the solenoid opening / closing valve 02
By opening and closing f and 02g, pressure oil is supplied to and discharged from the work machine cylinder 04 from the electromagnetic proportional control valve 02, the work machine cylinder 04 expands and contracts to elevate and tilt the fork, and the tilt angle of the work machine lever 06. Adjustment, work machine cylinder 0
The flow rate of the pressure oil to 4 can be adjusted to freely control the ascending / descending speed and the like.

[0004]

By the way, in the conventional forklift truck, it was extremely difficult to perform traveling operation (handle operation) while raising the fork. In other words, in order to perform both operations at the same time, the handle had to be operated while tilting the work implement lever.

Further, in order to raise the fork over a long lift, the working machine lever has to be tilted for a long time, and the operator's arm is tired. This has been a particular problem in a forklift having a high mast height (two-stage full-fli type, three-stage full-fli type, high-mast type, etc.).

SUMMARY OF THE INVENTION In view of the above-mentioned conventional technique, it is an object of the present invention to provide a forklift control device capable of lifting a fork by a simple operation.

[0007]

SUMMARY OF THE INVENTION The structure of the present invention for solving the above-mentioned problems includes a working machine lever for outputting a lever operation signal having a value corresponding to an inclination angle, and a flow rate control having a value corresponding to the value of the lever operation signal. A controller that outputs a signal, an electromagnetic proportional control valve that supplies and discharges pressure oil according to the value of the flow rate control signal, and a lift cylinder that expands and contracts by expanding and contracting the pressure oil by the electromagnetic proportional control valve. In a forklift having, a lift sensor, a position sensor that detects when the fork has reached a sensor detection position that is slightly lower than the lift upper limit position, and a disconnection detection that detects disconnection of the signal wire for the position sensor. And a hydraulic pressure sensor that is disposed in a pipe line that supplies and discharges pressure oil to and from the lift cylinder, and that detects the pressure of the pressure oil in the pipe line. The load of the load on the fork is calculated based on the pressure detected by the fork, and when the automatic raising switch is turned on when the value of the lever operation signal is zero, even if the load is different, the fork is initially raised. The ascending speed of the fork gradually increases, the ascending speed of the fork becomes constant in the middle ascending period, and the ascending speed of the fork gradually decreases in the latter ascending period after the position sensor detects that the fork has passed the sensor detection position. It has a function to control the value of the flow control signal by adding load so that the fork rises according to the characteristics set in advance so that it will detect the disconnection of the signal wire for the position sensor. In this case, even if the automatic raising switch is turned on, it has a function of prohibiting the raising of the fork.

[0008]

When the automatic lift switch is pressed while the work equipment lever is in the neutral position, the fork automatically rises, and when the fork reaches the upper limit, the fork stops. Further, when the disconnection detecting means detects the disconnection of the signal line for the position sensor,
Automatic climbing is prohibited.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. 1 to 9 show an embodiment of the present invention. FIG. 7 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, and the pair of left and right inner masts 3 are moved up and down with the outer mast 2 as a guide as the piston rod 1a expands and contracts. At this time, the outer mast 2 is fixed to the vehicle body 7 in front of the vehicle body 7. As a result, the inner mast 3
Along with the lifting and lowering, the lifting and lowering section including the bracket 5 suspended on the chain and the fork 4 for directly loading luggage is lifted and lowered. The tilt cylinder 8 is for tilting the elevating part together with the outer mast 2 and the inner mast 3 forward (opposite the vehicle body 7) and backward (on the vehicle body 7 side). That is, in the case of unloading, it tilts forward and in the case of loading and tilting backward when carrying a load, each workability is kept good and safety is secured.

The working machine levers 9a and 9b are operated by an operator to control the operations of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11. It is housed in a joystick box 13 together with a safety switch 12 for performing. Further, the joystick box 13 is provided with an automatic raising switch 24 and a manual switch 26. The work machine levers 9c, 9d, 9e are provided for handling various attachments such as roll clamps and bale clamps.
The seat switch 14 is a switch that operates when an operator sits in the driver's seat 15, and the output signal thereof is output to the controller 10.

FIG. 8 is a block diagram showing an example of the control device for the forklift. As shown in the figure, the working machine lever 9a is formed by a potentiometer and sends a lever operation signal S ₁ whose current value is proportional to the operation amount to the controller 10. The controller 10 sends out a flow rate control signal S ₂ for adjusting the opening degree of the spool of the electromagnetic proportional control valve 11 based on the lever operation signal S ₁ . Electromagnetic proportional control valve 1
1 moves the spool in proportion to the magnitude of the flow rate control signal S ₂ to control the flow rate of the pressure oil flowing through the hydraulic line 16 so that the operating speed of the lift cylinder 1 corresponds to the operation amount of the working machine lever 9a. Control to do. A position sensor 2 for detecting the position of the lift cylinder is provided near the lift cylinder 1.
5 is provided. The position sensor 25 outputs a detection signal when the fork 4 reaches a sensor detection position slightly lower than the upper limit position of the fork.

The oil pressure sensor 17 is arranged in the oil pressure conduit 16 and sends out an oil pressure signal S ₃ representing the oil pressure in this oil pressure conduit 16. The controller 10 processes the hydraulic signal S ₃ to calculate the load applied to the lift cylinder 1. Furthermore,
The controller 10 operates by being supplied with power from the battery 21 by turning on the starter switch 20 housed in the console box 19 together with the warning light 18, and when the safety switch 12 is operated and the seat switch 14 does not operate. Flow rate control signal S ₂ when seated
The current value of is set to zero and the opening of the electromagnetic proportional control valve 11 is controlled to be zero. In the figure, 22 is a hydraulic pump and 23
Is the source of hydraulic oil.

FIG. 1 is a block diagram showing a control device in which a main part of this embodiment is extracted. 7, those parts which are the same as those corresponding parts in FIGS. 7 and 8 are designated by the same reference numerals, and a overlapping description will be omitted. Further, the inside of the controller 10 of FIG. 1 is shown by functional blocks.

The outline of the control by the control device of FIG. 1 will be described first, and the detailed operation will be performed thereafter. In this control, if the automatic raising switch 24 is turned on when the work implement lever 9a is in the neutral position (see FIG. 1), the fork 4 is automatically raised according to the characteristics shown in FIG.
It stops after passing _S. That is, in FIG. 2, the fork 4 is raised while increasing gradually rising rate in the period I, rises in the period II in a constant speed, the fork 4 is a position sensor 25 that was in the sensor detection position H _S
When (see FIG. 1 and FIG. 8) is detected, the state moves to the state of the period III, the rising speed is gradually reduced, and the fork 4 is stopped. Although details will be described with reference to FIG. 9, when the signal line for the position sensor 25 is broken, the automatic raising of the fork 4 is prohibited even if the automatic raising switch 24 is turned on.

In this control, since the fork 4 is raised along the characteristic shown in FIG. 2 even if the load is different, the characteristic α,
As shown by β, in the initial and latter stages of the rise, when the load is small, the value of the flow rate control signal S ₂ is reduced to narrow the oil supply opening of the electromagnetic proportional control valve 11, and when the load is large, the flow rate control signal S ₂ is increased. Is increased to increase the oil supply opening of the electromagnetic proportional control valve 11. Therefore, even if the load is different, the fork 4 can be lifted substantially along the characteristics shown in FIG.

Next, when the embodiment of the present invention is normal (when the wire is not disconnected)
Details of the control will be described with reference to FIGS. 1 and 4 to 6. Note that the operation steps in FIG. 4 are indicated by using the symbol “S”.

First, after the initialization, the working machine lever 9
It is determined whether or not a is in the neutral position (S1). When the working machine lever 9a is turned in the direction up is to fork increase control sends a flow control signal S ₂ that instructs to increase the piston rod 1a of the lift cylinder 1 to the electromagnetic proportional control valve 11 (S2), The flow rate control signal S for instructing to lower the flow rate when the flow rate control signal S is in the downward direction.
₂ is sent to the solenoid proportional control valve 11 to control the fork lowering (S
Do 3). Work machine lever 9a is in the neutral position, and, when the automatic raising switch 24 rather than the automatic increase control mode is not turned (S1, S4, S5) is to zero the value of the flow rate control signal S ₂ Fork Neutral control for stopping 4 at that position is performed (S6).

The load / acceleration control amount correspondence table 102 shown in FIG. 1 stores the acceleration value calculation characteristics shown in FIG. 5, and the load / deceleration control amount correspondence table 105 has the deceleration value calculation characteristics shown in FIG. Remembered On the other hand, the speed increase control amount extraction means 101 and the deceleration control amount extraction means 104 are the oil pressure sensor 17
The load of the luggage loaded on the fork 4 is calculated from the hydraulic signal S ₃ sent from the. When the automatic raising switch 24 is turned on, the speed increase control amount extraction means 101
Is an upper limit value output means 10 that obtains an acceleration value corresponding to the load at that time from the calculated load and the characteristics of the correspondence table 102.
3 outputs an upper limit value according to the engine speed, and the deceleration control amount extraction means 104 uses the calculated load and the correspondence table 1
From the characteristic of 05, the deceleration value corresponding to the load at that time is obtained (S7). Further, the automatic control flag and the speed increasing flag are set, and the calculated speed increasing value is output as an initial value (S7).

When the control amount output means 107 receives the first speed-up value from the speed-up control amount extraction means 101, the speed-up mode (S
8), and the flow rate control signal S ₂ for instructing the piston rod 1a of the lift cylinder 1 to rise at the speed indicated by the acceleration value is output. Therefore, the piston rod 1a begins to move up. The acceleration value of the acceleration control amount extraction means 101 is once stored in the storage means 108 and then returned to the acceleration control amount extraction means 101 again. When one control cycle has elapsed, the output value output from the speed-up control amount extraction means 101 is the previous value plus the speed-up value (S9). Therefore, the value of the flow rate control signal S ₂ output from the control amount output means 107 gradually increases, and the ascending speed of the piston rod 1a, that is, the ascending speed of the fork 4 gradually increases. This state corresponds to the period I in FIG.

The comparison means 106 is an acceleration control amount extraction means 1
The output value of 01 is compared with the upper limit value obtained by the upper limit value output means 103 (S10), and when the output value becomes larger than the upper limit value, the upper limit value is sent to the control amount output means 107.
Then, the speed increasing flag is cleared and the holding flag is set (S11). Such become the holding mode (S12) the control amount output unit 107 outputs the flow control signal S ₂ that instructs piston rod 1a at a speed indicated by the upper limit value increases (S13). Therefore, the piston rod 1a and thus the fork 4 rise at a constant speed. This state is shown in Figure 2.
Corresponding to period II.

The fork 4 moves up and the sensor detection position H _S
When the position sensor 25 detects that the
4) The control amount output means 107 outputs the flow rate control signal S ₂ according to the value obtained by the deceleration control amount extraction means 104 from the previous value, and clears the holding flag to enter the deceleration mode (S15). Therefore, the ascending speed of the fork 4 starts to decrease. The deceleration value of the deceleration control amount extraction means 104 is
Once stored in the storage means 108, it is returned to the deceleration control amount extraction means 104 again. When one control cycle has elapsed, the output value output from the deceleration control amount extraction means 104 is the previous value minus the deceleration value (S1).
6). Therefore, the value of the flow rate control signal S ₂ output from the control amount output means 107 gradually decreases, and the piston rod 1
The ascending speed of a, that is, the ascending speed of the fork 4 gradually decreases. When the output value of the deceleration control amount extraction means 104 becomes smaller than the preset stop value (S1
7), it clears the automatic increase control flag (S18), and the zero value of the flow rate control signal S _2, stopping the fork 4 stops the piston rod 1a of the lift cylinder 1. The state in which the fork 4 gradually decelerates and stops corresponds to the period III in FIG. The disconnection detecting means 110
Detects the disconnection of the signal line of the position sensor 25, and its specific configuration and function will be described below.

Here, the control at the time of disconnection of this embodiment is shown in FIG.
It will be explained based on The inside of the controller 10 in FIG.
It is shown in the block. CP of controller 10
U120 synchronizes with the clock of the clock generator 121.
Various kinds of arithmetic processing, and is stored in the memory 122.
The arithmetic processing is performed using the stored software. Meanwhile, work
Lever operation signal S output from the machine lever 9a ₁And rank
The detection signal output from the position sensor 25 is an A / D converter.
Data is converted into a digital signal by the data processor 123, and then the CPU
Sent to 120. Automatic lift switch 24 and manual
The closing switch 26 is turned on by the interface 124.
Is sent to the CPU 120 via. Flow control signal S
₂Is a solenoid valve drive circuit 1 based on the control of the CPU 120.
25 to the electromagnetic proportional control valve 11.

Further, the position sensor 25 is provided with the resistor R1, the controller 10 is provided with the resistor R2, and the position where the resistor R1 (resistance value r1) and the resistor R2 (resistance value r2) are connected. A signal voltage V is applied to the signal line 25a for the sensor 25. And resistors R1 and R
2 and the CPU 120 constitute a disconnection detecting means. In FIG. 9, 126 is a power supply circuit, 50 is a battery, and 51 is a disconnection display unit.

When the position sensor 25 is OFF when the signal line 25a for the position sensor 25 is normal and not broken, the voltage V ₁ input through the A / D converter 123 is as follows. Become. V ₁ = V · r2 / (r1 + r2) When the automatic raising switch 24 is turned on during normal operation, the automatic raising described above is executed.

When the signal line 25a for the position sensor 25 is broken, the voltage V ₁ input through the A / D converter 123 becomes the ground potential. Therefore, the CPU 120
Detects that the signal line 25a is broken. Even if the automatic raising switch 24 is turned on at the time of this disconnection, the CPU 12
0 is a flow control signal S that prohibits the fork 4 from rising.
₂ is output, and the fork 4 is held in its current position without rising. If the automatic lifting of the fork 4 is not prohibited at the time of disconnection, the fork 4 starts to lift by turning on the automatic lifting switch 24, but the position sensor 25 cannot detect it, so that the fork 4 collides with the upper end of the fork. There is. In the present invention, the signal line 25a
When is disconnected, the automatic ascent is prohibited, so such a problem does not occur.

When the disconnection is detected, the disconnection display section 51 displays that the disconnection has occurred. When it is determined that a wire break has occurred, the manual switch 26 is turned on so that the fork 4 can be lifted by a lift command for the working machine lever 9a.

[0027]

According to the present invention as described in detail with reference to the embodiments, the lift starts to rise smoothly only by turning on the automatic raising switch. While lifting the lift, the operator can concentrate on the steering wheel operation or adjust the lift speed by controlling the accelerator of the engine. The lift stops without shock when passing the sensor detection position. In this way, the lift can be raised by a simple operation, and work efficiency is improved. Further, in the present invention, when the signal line for the position sensor is broken, the automatic rising is prohibited,
Increases safety.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control device in which a main part of an embodiment of the present invention is extracted.

FIG. 2 is a characteristic diagram showing a raised state of a fork according to the present embodiment.

FIG. 3 is a characteristic diagram showing an adjustment state of a flow rate control signal.

FIG. 4 is a control flow chart showing a control state of the embodiment.

FIG. 5 is a characteristic diagram showing an acceleration value calculation characteristic.

FIG. 6 is a characteristic diagram showing deceleration value calculation characteristics.

FIG. 7 is a perspective view showing a forklift to which the present invention is applied.

FIG. 8 is a block diagram showing an entire control device according to an embodiment of the present invention.

FIG. 9 is a block diagram showing a control device in which a main part of an embodiment of the present invention is extracted.

FIG. 10 is a hydraulic circuit showing a hydraulic system of a conventional electromagnetic hydraulic forklift.

[Explanation of symbols]

1 Lift Cylinder 1a Piston Rod 4 Fork 9a Working Machine Lever 10 Controller 11 Electromagnetic Proportional Control Valve 16 Hydraulic Pipeline 17 Hydraulic Pressure Sensor 24 Automatic Lift Switch 25 Position Sensor 25a Signal Line 26 Manual Switch 120 CPU R1, R2 Resistance S ₁ Lever Operation Signal S ₂ flow rate control signal S ₃ hydraulic pressure signal

Front page continuation (72) Inventor Yukio Uchiyama 3000 Tana, Sagamihara, Kanagawa Mitsubishi Heavy Industries, Ltd. Sagamihara Manufacturing Co., Ltd. (72) Inventor Toshiyuki Midorikawa, 3000, Tana, Sagamihara, Kanagawa Within the corporation

Claims (1)

[Claims] 1. A work implement lever that outputs a lever operation signal having a value corresponding to a tilt angle, a controller that outputs a flow rate control signal having a value corresponding to the value of the lever operation signal, and a flow control signal corresponding to the value of the flow rate control signal. An electromagnetic proportional control valve that supplies and discharges a certain amount of pressure oil,
In a forklift truck that has a lift cylinder that lifts and lowers the fork by expanding and contracting the pressure oil supplied and discharged by the electromagnetic proportional control valve, the fork reached the sensor detection position that is slightly lower than the automatic lift switch and the upper limit position of the fork lift. A position sensor for detecting such a situation, a disconnection detecting means for detecting a disconnection of the signal wire for the position sensor, and a pipe line for supplying and discharging pressure oil to and from the lift cylinder. In addition to having a hydraulic pressure sensor that detects the pressure, the controller calculates the load of the load loaded on the fork based on the pressure detected by the hydraulic pressure sensor, and when the value of the lever operation signal is zero, the automatic raising switch is turned on. Even if the load is different, the ascending speed of the fork gradually increases in the early ascending period, and the fork ascending speed becomes constant in the middle ascending period. , The load is adjusted so that the fork rises according to the characteristics set in advance so that the fork rise speed gradually decreases and stops in the latter ascent after the position sensor detects that the fork has passed the sensor detection position. In addition to having a function of controlling the value of the flow rate control signal, when the disconnection detecting means detects disconnection of the signal line for the position sensor, it has a function of prohibiting the fork from rising even if the automatic lifting switch is turned on. A forklift control device having.