JP2706374B2 - Forklift control device - Google Patents

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 improved so that a fork can be automatically and safely lowered to a traveling posture position. Further, in the event of a disconnection failure, automatic lowering is prohibited.

[0002]

2. Description of the Related Art Conventionally, as a control device for a forklift which can be operated by an electromagnetic hydraulic system, for example, a control device shown in FIG. As shown in the figure, the pressure oil from the hydraulic pump 01 is diverted to an electromagnetic proportional control valve 02 and a control valve (not shown) for power steering (not shown) via a pipe 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 for switching an oil passage. Pilot piston 02b and spool 02
c is connected to the springs 03a and 03b, respectively, and is held at a neutral position without hydraulic pressure. On both sides of the pilot piston 02b, pilot inflow pipes 02d,
02e are provided respectively. The pilot inflow pipes 02d and 02e are connected to a hydraulic system for power steering via electromagnetic on-off 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 right and left 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 / discharged to / from the work cylinder 04 is adjusted according to the moving position of the spool 02c, and the elevating speed is adjusted. As the work machine cylinder 04, various types such as a type that raises and lowers a fork (not shown) and a type that tilts the fork can be used.

On the other hand, the opening and closing of the solenoid on-off valves 02f and 02g are controlled by a flow control signal from the controller 05. The controller 05 outputs a flow control signal according to a lever operation signal from the work implement lever 06. The work implement lever 06 has 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 power in the neutral position. Therefore,
By operating the work machine lever 06, the electromagnetic on / off valve 02
f, 02g are opened and closed to supply and discharge pressure oil from the electromagnetic proportional control valve 02 to the work machine cylinder 04, the work machine cylinder 04 expands and contracts, and the fork moves up and down, tilts, etc., and the tilt angle of the work machine lever 06 Is adjusted, the working machine cylinder 0
The flow rate of the pressure oil to 4 is adjusted, and the elevating speed and the like can be freely controlled.

[0004]

When the forklift travels, the fork is set at a predetermined position at a height of about 20 cm above the ground (this position is referred to as a "position of running posture").
After setting to, had started running. 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, and if he lowers the fork and tries to stop it in the running posture position, he accidentally touches the ground Sometimes the fork was lowered. When the fork contacts the ground in this way, the load is shocked, which is a problem.

[0005] A veteran operator can lower the fork to the running posture position by a so-called "can" without visual observation based on the experience so far.
The stop position was not accurate. In addition, if the loading load is different, the lowering speed of the fork will be different even if the inclination angle of the work implement lever is the same. That is,
Even if the inclination angle of the work implement lever is the same, the descending speed increases when the load is large and decreases when the load is light. Therefore, when handling loads with different loads, it is extremely difficult to accurately and quickly position the fork in the traveling posture position.

SUMMARY OF THE INVENTION In view of the above prior art, an object of the present invention is to provide a control device for a forklift capable of automatically lowering a fork and stopping accurately at a position of a running posture.

[0007]

According to the present invention, there is provided a work implement lever for outputting a lever operation signal having a value corresponding to a tilt angle, and a flow control having a value corresponding to a value of the lever operation signal. A controller that outputs a signal, an electromagnetic proportional control valve that supplies and discharges an amount of pressure oil according to the value of the flow control signal, and a lift cylinder that supplies and discharges pressure oil by the electromagnetic proportional control valve to expand and contract and lift the fork And a position sensor for detecting that the fork has reached a sensor detection position slightly higher than the position of the running posture, and a disconnection detecting means for detecting disconnection of a signal line for the position sensor. And a hydraulic sensor arranged in a pipeline for supplying and discharging hydraulic oil to and from the lift cylinder, and detecting a pressure of the hydraulic oil in the pipeline, and the controller detects the hydraulic oil with a hydraulic sensor. The load of the load loaded on the fork is calculated based on the pressure obtained, and the automatic lowering switch is turned on when the lever operation signal is zero. Gradually increases, and the lowering speed of the fork becomes constant in the middle period of lowering, and the lowering speed of the fork gradually decreases and stops in the latter period of lowering after the position sensor detects that the fork has passed the sensor detection position. As the fork descends according to the characteristics set in advance, it has a function of controlling the value of the flow control signal in consideration of the load, and when the disconnection detecting means detects the disconnection of the signal line for the position sensor, It has a function of inhibiting the fork from lowering even when the automatic lowering switch is turned on.

[0008]

[Function] If the automatic lowering switch is turned on when the work equipment lever is in the neutral position, even if the load of the load on the fork is different, it will smoothly descend along almost the same descending characteristics, Stop at the running posture. 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 Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. 1 to 10 show one embodiment of the present invention. FIG. 8 is a perspective view illustrating an example of a forklift applied to the present 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, the pair of left and right inner masts 3 is 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 is moved up and down, the elevating section 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 section forward (toward the vehicle body 7 side) and rearward (to the vehicle body 7 side) together with the outer mast 2 and the inner mast 3. That is, in the case of unloading, it tilts forward, and in the case of unloading and transports luggage, it tilts rearward, so that the respective workability is maintained well and safety is ensured.

The working machine 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. It is stored in a joystick box 13 together with a safety switch 12 for performing the operation. Further, the joystick box 13 is provided with an automatic lowering switch 24 and a manual switch 26. The work implement levers 9c, 9d, and 9e handle various attachments such as a roll clamp and a bail clamp.
The seat switch 14 is a switch that operates when the operator sits on the driver's seat 15, and outputs an output signal to the controller 10.

FIG. 9 is a block diagram showing an example of the control device of the forklift. As shown in the figure, the working machine lever 9a is formed by a potentiometer, sends a lever operation signals S ₁ proportional to the current value by the operation amount to the controller 10. The controller 10 sends the flow control signal S ₂ to adjust the degree of opening of the spool of the electromagnetic proportional control valve 11 on the basis of the lever operation signal S _1. Electromagnetic proportional control valve 1
1 by moving the spool in proportion to the magnitude of the flow control signal S _2, corresponding to the operation speed of the lift cylinder 1 to control the flow rate of the hydraulic fluid flowing through the hydraulic line 16 to the operation amount of the work machine levers 9a To control. A position sensor 2 for detecting the position of the lift cylinder is provided near the lift cylinder 1.
5 are provided. The position sensor 25 outputs a detection signal when the fork 4 comes to a sensor detection position (which is located slightly above the position of the running posture).

The hydraulic pressure sensor 17 is disposed in the hydraulic pressure line 16 and sends out a hydraulic pressure signal S ₃ representing the oil pressure in the hydraulic pressure line 16. The controller 10 processes the hydraulic signal S ₃ to calculate the load applied to the lift cylinder 1. Furthermore,
When the starter switch 20 housed in the console box 19 together with the warning light 18 is turned on, the controller 10 is operated by being supplied with power from the battery 21, and is operated when the safety switch 12 is operated and when the seat switch 14 is not operated. In the seat state, the flow control signal S ₂
Is controlled so that the opening of the electromagnetic proportional control valve 11 becomes zero. In the drawing, reference numeral 22 denotes a hydraulic pump;
Is a hydraulic oil source.

FIG. 1 is a block diagram showing a control device in which main parts of the present embodiment are extracted. In the figure, the same parts as those in FIGS. 8 and 9 are denoted by the same reference numerals, and redundant description will be omitted. The inside of the controller 10 in FIG. 1 is shown by functional blocks.

An outline of the control by the control device shown in FIG. 1 will be described first.
The detailed operation will be described later. In this control, the work equipment lever
-9a is in the neutral position and the automatic lowering switch 24
When inserted (see FIG. 1), the fork 4 has the characteristics shown in FIG.
Automatically descends along the road and stops. Toes
In FIG. 2, the fork 4 at the height H is
Descends with a gradually increasing descending speed, and is constant in period II
The fork 4 descends at the speed and the sensor detection position H_SBecome
Is detected by the position sensor 25 (see FIGS. 1 and 9).
Then, the state moves to the period III, and the descent speed gradually decreases and runs.
Row posture position H _O(About 20 cm above ground)
The fork 4 is stopped. See FIG. 10 for details.
However, the signal line for the position sensor 25 is disconnected.
When the automatic lowering switch 24 is turned on,
Automatic lowering of the workpiece 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 shown by β, when the load is small, the flow control signal S
A value of ₂ is increased to widen the oil discharge opening of the electromagnetic proportional control valve 11 is made smaller the oil discharge opening of the electromagnetic proportional control valve 11 to decrease the value of the flow rate control signal S ₂ when a load is large. In the case of a large load, even if the oil discharge opening is narrowed, the force of pushing down the lift cylinder 1 by the weight of the load acts to increase the discharge hydraulic pressure. Therefore, even if the load differs, the control shown in FIG. The fork 4 can be lowered along the characteristic shown in FIG.

Next, the details of the control of this embodiment in the normal state (when there is no disconnection) will be described with reference to FIGS. 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 at 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 control signal S for instructing the lowering when the shutter is inserted in the lowering direction.
₂ is sent to the electromagnetic proportional control valve 11 and the fork lowering control (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 4 is stopped at that position to perform neutral control (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 stores 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. On the other hand, the speed-up control amount extraction unit 101, the limit control amount extraction unit 103, and the deceleration control amount extraction unit 105
From the hydraulic pressure signal S ₃ sent from the hydraulic pressure sensor 17, the load of the load loaded on the fork 4 is calculated. Then, when the automatic lowering switch 24 is turned on, the speed increase control amount extracting means 101 obtains a speed increase value corresponding to the load at that time from the calculated load and the characteristics of the correspondence table 102. From the calculated load and the characteristics of the correspondence table 104, a load limit value corresponding to the load at that time is obtained, and the deceleration control amount extracting means 105 determines the deceleration corresponding to the load at that time from the calculated load and the characteristics of the correspondence table 106. A value is obtained (S7). Further, an automatic control flag and an acceleration flag are set, and the obtained acceleration value is output as an initial value (S7).

When the control amount output means 108 receives the initial acceleration value from the speed increase control amount extraction means 101, the speed increase mode (S
Enters 8), the piston rod 1a of the lift cylinder 1 at a speed indicated by the speed increasing value to output a flow control signal S ₂ that instructs lowered. Therefore, the piston rod 1a starts to descend. The speed-up value of the speed-up control amount extraction means 101 is temporarily stored in the storage means 109 and then returned to the speed-up control amount extraction means 101 again. After one control cycle has elapsed, the output value output from the speed increase control amount extraction means 101 becomes the value obtained by adding the speed increase value to the previous value (S9). Therefore the value of the flow rate control signal S ₂ output from the control amount output unit 108 gradually increases, lowering speed of the piston rod 1a, i.e. lowering speed of the fork 4 is gradually increased. This state corresponds to the period I in FIG.

The comparing means 107 is a speed increasing control amount extracting means 1
The output value of 01 is compared with the limit value obtained by the limit control amount extraction means 103 (S10). 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 period II in FIG.

The fork 4 descends and the sensor detection position H _S
Is reached by the position sensor 25 (S1
4), the control amount output unit 108 outputs the flow control signal S ₂ according to a value obtained by the deceleration control amount extraction unit 105 from the previous value, enter the deceleration mode by clearing the hold flag (S15). Therefore, the lowering 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. After one control cycle, the output value output from the deceleration control amount extraction means 105 is a value obtained by subtracting the deceleration value from the previous value (S1).
6). Therefore the value of the flow rate control signal S ₂ output from the control amount output unit 108 gradually decreases, the piston rod 1
The descending speed of a, that is, the descending speed of the fork 4 gradually decreases. If the output value of the deceleration control amount extraction means 105 becomes smaller than a 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 magnitude of the stop value is set so that the stop position of the fork 4 is the position H _{O of the} traveling posture (about 20 cm above the ground). Such a state in which the fork 4 gradually decelerates and stops at the position of the traveling posture corresponds to a period III in FIG. The disconnection detecting means 110 detects a 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 in this embodiment is shown in FIG.
This will be described based on FIG. The inside of the controller 10 in FIG.
This is indicated by hardware configuration blocks. Controller 10
The CPU 120 synchronizes with the clock of the clock generator 121.
Various arithmetic processes are performed in anticipation.
The arithmetic processing is performed using the software stored in. on the other hand,
Lever operation signal S output from work implement lever 9a ₁Passing
The detection signals output from the position and position sensors 25 are A / D
After being converted into a digital signal by the inverter 123,
Sent to PU 120. Automatic lowering switch 24 and manifold
The input signal of the dual switch 26 is output from the interface 1
24 to the CPU 120. Flow control signal S
_TwoIs a solenoid valve drive circuit 1 based on the control of the CPU 120.
25 is sent to the electromagnetic proportional control valve 11.

Further, the position sensor 25 is provided with a resistor R1, the controller 10 is provided with a 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, R
2 and the CPU 120 constitute a disconnection detecting means. In FIG. 10, reference numeral 126 denotes a power supply circuit, 50 denotes a battery, and 51 denotes a disconnection display unit.

[0024] When the signal line 25a for the position sensor 25 is not broken normal, if position sensor 25 is turned OFF, voltages V ₁ inputted through the A / D converter 123 is as follows Become. V ₁ = V · r2 / (r1 + r2) When the automatic lowering switch 24 is turned on in a normal state, the automatic lowering described above is executed.

[0025] When the signal line 25a for the position sensor 25 is disconnected, voltages V ₁ inputted through the A / D converter 123 becomes the ground potential. Therefore, the CPU 120
Detects that the signal line 25a is disconnected. Even if the automatic lowering switch 24 is turned on during this disconnection, the CPU 12
0 is a flow control signal S that prohibits the fork 4 from descending.
₂ is output, and the fork 4 is maintained at the current position without descending. If it is assumed that the automatic lowering of the fork 4 is not prohibited at the time of disconnection, the fork 4 starts lowering by turning on the automatic lowering switch 24. is there. In the present invention, when the signal line 25a is disconnected, the automatic lowering is prohibited, so that such a problem does not occur.

When a disconnection is detected, the disconnection display section 51 indicates that a disconnection has occurred. When the manual switch 26 is turned on when it is determined that the disconnection has occurred, the fork 4 can be lowered by the lowering command of the work implement lever 9a.

[0027]

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

[Brief description of the 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 illustrating a lowered state of a fork according to the present embodiment.

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

FIG. 4 is a control flowchart showing a control state of the embodiment.

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

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 the entire control device according to the embodiment of the present invention.

FIG. 10 is a block diagram showing a control device in which main parts of the embodiment of the present invention are 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 forks 9a work machine lever 10 controller 11 solenoid proportional control valve 16 hydraulic line 17 hydraulic pressure sensor 24 automatic lowering switch 25 position sensor 25a signal line 26 the manual switch 120 CPU R1, R2 resistor S ₁ lever operation signal S ₂ flow control signal S ₃ oil pressure signal

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Toshiyuki Midorikawa 3000 Tana, Sagamihara-shi, Kanagawa M.H.

Claims (1)

(57) [Claims] 1. A work implement lever for outputting a lever operation signal having a value corresponding to an inclination angle, a controller for outputting a flow control signal having a value corresponding to a value of the lever operation signal, and a controller for outputting a flow control signal having a value corresponding to a value of the lever control signal. An electromagnetic proportional control valve for supplying and discharging an amount of pressure oil,
In a forklift that has a lift cylinder that moves up and down the fork by expanding and contracting by supplying and discharging pressurized oil by an electromagnetic proportional control valve, the fork has reached an automatic lowering switch and a sensor detection position slightly higher than the running posture position. And a disconnection detecting means for detecting disconnection of a signal line for the position sensor, and a pressure line for supplying and discharging pressure oil to and from the lift cylinder. The controller determines the load of the load loaded on the fork based on the pressure detected by the hydraulic sensor, and furthermore, when the value of the lever operation signal is zero, the automatic lowering switch is turned on. Thus, even if the load is different, the fork's descent speed gradually increases in the initial descent, and the fork's descent speed becomes constant in the middle of descent. In the latter half of the descent after the position sensor detects that the fork has passed the sensor detection position, the load is applied so that the fork descends according to a preset characteristic so that the fork's descent speed gradually decreases and stops. And a function of controlling the value of the flow rate control signal and, when the disconnection detecting means detects a disconnection of the signal line for the position sensor, inhibiting the fork from lowering even if the automatic lowering switch is turned on. A control device for a forklift, comprising: