JPH06127898A - Controller for fork lift - Google Patents

Abstract

PURPOSE:To lower a fork of a fork lift to a travelling posture position automati cally, and stop it accurately. CONSTITUTION:When an automatic lowering switch 24 is tuned on during the time when a working machine lever 9a is shifted at a neutral position, the flow quantity control signal S2 for commanding the lowering is output, and a lift cylinder is shortened to lower a 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 is lowered along the nearly same characteristics even in the case where a different load is detected. The fork is stopped after a position sensor 25 detects the fork. At the initial time of the lowering, the lowering speed of the fork is increased gradually, and at the latter time of the lowering, the lowering speed of the fork is decreased gradually and the fork is stopped. When a signal line 25a for position sensor 25 is disconnected, even if the automatic lowering switch 24 is turned on, the automatic lowering is stopped.

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 an improvement for automatically and without shock lowering a fork to a position in a traveling posture. Further, in the case of a wire breakage failure, automatic lowering 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. 11 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 work 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]

When the forklift is traveling, the fork has a predetermined position at a height of about 20 cm above ground (this position is referred to as the "traveling position").
It started running after being set to. However, when a large load is loaded on the fork, the operator of the forklift does not know the positional relationship between the fork and the ground. Sometimes lowered the fork. When the fork contacts the ground in this way, the load is shocked, which is a problem.

A veteran operator can lower the fork to the position of the traveling posture by the so-called "can" without any visual inspection, based on his experience so far.
The stop position was not accurate. Moreover, if the load is different, the lowering speed of the fork is different even if the working machine lever has the same inclination angle. That is,
Even if the tilt angle of the work implement lever is the same, the descending speed becomes fast when the load is large, and the descending speed becomes slow when the load is light. Therefore, when handling loads having different loads, it becomes extremely difficult to accurately position the fork in the traveling posture in a short time.

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 that can automatically lower a fork and accurately stop the forklift at a position in a traveling posture.

[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 the following, an automatic lowering switch, a position sensor that detects that the fork has reached a sensor detection position that is slightly higher than the position of the traveling attitude, and a disconnection detection unit 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 applied pressure, and if the automatic lowering switch is turned on when the value of the lever operation signal is zero, the lowering speed of the fork in the initial stage of lowering even if the load is different. Gradually increases, and the fork lowering speed becomes constant in the middle lowering period, and the fork lowering speed gradually decreases and stops in the second lowering period after the position sensor detects that the fork has passed the sensor detection position. So that the fork descends according to the characteristics set in advance, it has a function of controlling the value of the flow rate control signal by adding a load, and when the disconnection detecting means detects the disconnection of the signal line for the position sensor, It is characterized in that it has a function of prohibiting the lowering of the fork even when the automatic lowering switch is turned on.

[0008]

Operation: If the automatic lowering switch is turned on when the work implement lever is in the neutral position, even if the load on the fork is different, the fork will descend smoothly along with almost the same lowering characteristics, and the fork will Stop at the running position. Further, when the disconnection detecting means detects the disconnection of the signal line for the position sensor, the automatic lowering 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 10 show an embodiment of the present invention. FIG. 8 is a perspective view showing an example of a forklift applied to this embodiment. As shown in the figure, the lift cylinder 1 is fixed to the pair of left and right outer masts 2,
With the expansion and contraction of the piston rod 1a, the pair of left and right inner masts 3 are moved up and down 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, the up-and-down unit composed of the bracket 5 suspended on the chain and the fork 4 for directly loading luggage is moved up and down. 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 lowering 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. 9 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 (which is located slightly above the position of the running posture).

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. 8, those parts which are the same as those corresponding parts in FIGS. 8 and 9 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 explained first.
The detailed operation will be performed later. In this control, the working machine lever
-When the 9a is in the neutral position, turn the automatic lowering switch 24
When inserted (see FIG. 1), the fork 4 has the characteristics shown in FIG.
It automatically descends along the line and stops. Tsuma
2 In FIG. 2, the fork 4 that was at the height H in the period I
Falls gradually while the descent speed gradually increases, and remains constant in period II
The fork 4 descends at the speed, and the fork 4 moves to the sensor detection position H._SBecome
The position sensor 25 (see FIGS. 1 and 9) detected that
, Transition to the state of period III and the descending speed gradually decreases
Position H of posture _OWhere (ground height is about 20 cm)
Fork 4 is stopped at. See Figure 10 for details.
As described below, the signal line for the position sensor 25 is disconnected.
If the automatic lowering switch 24 is turned on,
The automatic lowering of the work 4 is prohibited.

In this control, the fork 4 is lowered along the characteristic shown in FIG. 2 even if the load is different.
As indicated by β, when the load is small, the flow control signal S
The value of ₂ is increased to widen the oil discharge opening of the electromagnetic proportional control valve 11, and when the load is large, the value of the flow rate control signal S ₂ is decreased to decrease the oil discharge opening of the electromagnetic proportional control valve 11. When the load is large, even if the oil discharge opening is narrowed, the force of pushing down the lift cylinder 1 acts due to the weight of the load to increase the discharge hydraulic pressure. Therefore, by performing the control of FIG. The fork 4 can be lowered along the characteristics shown in FIG.

Next, the details of the control of the present embodiment during normal operation (when there is no disconnection) will be described with reference to FIGS. 1 and 4-7. 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 lowering switch 24 instead of the automatic lowering control mode is not turned on (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 / limit control amount correspondence table 104 has the load limit calculation characteristics shown in FIG. The load / deceleration control amount correspondence table 106 stores the deceleration value calculation characteristics shown in FIG. 7. On the other hand, the acceleration control amount extraction means 101, the limit control amount extraction means 103, and the deceleration control amount extraction means 105
The load of the luggage loaded on the fork 4 is calculated from the hydraulic signal S ₃ sent from the hydraulic sensor 17. When the automatic lowering switch 24 is turned on, the speed increase control amount extraction means 101 obtains the speed increase value corresponding to the load at that time from the calculated load and the characteristics of the correspondence table 102, and the limit control amount extraction means 103 From the calculated load and the characteristic of the correspondence table 104, a load limit value corresponding to the load at that time is obtained, and the deceleration control amount extraction means 105 decelerates according to the load at that time from the calculated load and the characteristic of the correspondence table 106. A value is calculated (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 108 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 descend at the speed indicated by the acceleration value is output. Therefore, the piston rod 1a begins to descend. The acceleration value of the acceleration control amount extraction means 101 is temporarily stored in the storage means 109 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 108 gradually increases, and the descending speed of the piston rod 1a, that is, the descending speed of the fork 4 gradually increases. This state corresponds to the period I in FIG.

The comparison means 107 is the acceleration control amount extraction means 1
The output value of 01 is compared with the limit value obtained by the limit control amount extraction means 103 (S10), and when the output value becomes larger than the limit value, the limit value is sent to the control amount output means 108. Then, the speed increasing flag is cleared and the holding flag is set (S11). Such holding mode (S12) to the control amount output unit 108, the piston rod 1a at a speed indicated by the limit value and outputs a flow control signal S ₂ that instructs lowered (S13). Therefore, the piston rod 1a and thus the fork 4 descend at a constant speed. This state corresponds to the period II in FIG.

The fork 4 descends and the sensor detection position H _S
When the position sensor 25 detects that the
4) The control amount output means 108 outputs the flow rate control signal S ₂ according to the value obtained by the deceleration control amount extraction means 105 from the previous value, clears the holding flag, and enters the deceleration mode (S15). Therefore, the descending speed of the fork 4 starts to decrease. The deceleration value of the deceleration control amount extraction means 105 is
Once stored in the storage means 109, it is returned to the deceleration control amount extraction means 105 again. When one control cycle has elapsed, the output value output from the deceleration control amount extraction means 105 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 108 gradually decreases, and the piston rod 1
The descending speed of a, that is, the descending speed of the fork 4 is gradually reduced. When the output value of the deceleration control amount extraction means 105 becomes smaller than the preset stop value (S1
7), and clears the auto down 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. In this case, the size of the stop value is set so that the stop position of the fork 4 becomes the position H _{O of the} traveling posture (about 20 cm above ground). The state in which the fork 4 gradually decelerates and stops at the position in the running posture in this manner corresponds to the period III in FIG. The disconnection detecting means 110 detects 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 the present embodiment is shown in FIG.
It will be explained based on. The inside of the controller 10 of FIG.
It is shown in hardware building blocks. Of the controller 10
The CPU 120 synchronizes with the clock of the clock generator 121.
The memory 122 is for performing various arithmetic processing in anticipation.
The arithmetic processing is performed using the software stored in. on the other hand,
Lever operation signal S output from the work machine lever 9a ₁Over
And the detection signal output from the position sensor 25 is the A / D
C after being converted to a digital signal by the converter 123
It is sent to the PU 120. Automatic lowering switch 24 and manifold
The input signal of the dual switch 26 is the interface 1
It is sent to the CPU 120 via 24. 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. 10, reference numeral 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) Then, when the automatic lowering switch 24 is turned on in the normal state, the automatic lowering as 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 lowering switch 24 is turned on at the time of this disconnection, the CPU 12
0 is a flow rate control signal S for prohibiting the lowering of the fork 4.
₂ is output, and the fork 4 is held at the current position without descending. If the automatic lowering of the fork 4 is not prohibited at the time of breaking the wire, the fork 4 starts to lower by turning on the automatic lowering switch 24, but the position sensor 25 cannot detect it, so that there is a problem that the fork 4 collides with the ground. is there. In the present invention, when the signal line 25a is broken, the automatic lowering 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. If it is determined that the wire breakage has occurred, the manual switch 26 is turned on so that the fork 4 can be lowered by a descending command of the working machine lever 9a.

[0027]

According to the present invention as specifically described in connection with the above embodiments, the fork can be automatically and smoothly lowered to the position of the running posture even if the load is different. Therefore, the operator only has to turn on the automatic lowering switch for lowering the fork, and only needs to pay attention to the operation when lowering the fork, so that the efficiency of the cargo handling work can be improved. Further, according to the present invention, when the signal line for the position sensor is broken, automatic lowering is prohibited, so that the safety is enhanced.

[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 fork lowering state 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 load limit calculation characteristics.

FIG. 7 is a characteristic diagram showing deceleration value calculation characteristics.

FIG. 8 is a perspective view showing a forklift to which the present invention is applied.

FIG. 9 is a block diagram showing an entire control device according to an embodiment of the present invention.

FIG. 10 is a block diagram showing a control device in which a main part of an embodiment of the present invention is extracted.

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Uchiyama 3000 Tana, Sagamihara, Kanagawa Mitsubishi Heavy Industries, Ltd. Sagamihara Manufacturing Co., Ltd. Eye Sagami High Tech Co., Ltd.

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 solenoid proportional control valve, the fork has reached an automatic lowering switch and a sensor detection position that is slightly higher than the running posture position. A position sensor for detecting the disconnection, a disconnection detecting means for detecting disconnection of the signal wire for the position sensor, and a pipe for supplying and discharging pressure oil to and from the lift cylinder. In addition to having a hydraulic sensor for detecting the load, the controller calculates the load of the load loaded on the fork based on the pressure detected by the hydraulic sensor, and when the value of the lever operation signal is zero, the automatic lowering switch is turned on. Then, even if the load is different, the descending speed of the fork gradually increases in the initial stage of descending, and the descending speed of the fork becomes constant in the middle period of descending. The load is added so that the fork descends according to the characteristics set in advance so that the descending speed of the fork gradually decreases and stops in the latter half of the descending period after the position sensor detects that the brake has passed the sensor detection position. And has a function of controlling the value of the flow rate control signal, and also has a function of prohibiting the lowering of the fork even when the automatic lowering switch is turned on when the disconnection detecting means detects the disconnection of the signal line for the position sensor. A forklift control device characterized by the above.