JPH072498A - Cargo handling hydraulic control device - Google Patents

Abstract

PURPOSE:To surely stop a fork without giving a shock to the fork by decelerating the fork from a position in accordance with a load or the like applied to the fork. CONSTITUTION:A potentiometer 2 for detecting an operating amount of a cargo handling lever is connected to the cargo handling lever l provided in a driver's seat of a forklift, and the potentiometer 2 is connected to a controller 3. A fork 5 is provided liftably by a hydraulic cylinder 6 in the forklift. Here are connected a lift height sensor 7 for detecting a lift position of the fork 5 and a pressure sensor 12 for detecting a pressure, applied to the hydraulic cylinder 6, to the controller 3. That is, in the controller 3, based on a detection signal of the hydraulic cylinder 6, weight of a load applied to the fork 5 is calculated, to also set a shockless start position relating to a predetermined stop position of the fork 5 based on the weight of the load applied to the fork 5, and shockless control is performed from this set shockless start position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control system for cargo handling, and more particularly to a technique for reducing the impact generated by a sudden stop of a fork during movement.

[0002]

2. Description of the Related Art Conventionally, a control valve is provided in an industrial vehicle such as a forklift truck, and by adjusting the movement amount and the direction of the spool of the control valve, the supply amount and the supply amount of hydraulic oil supplied to a hydraulic cylinder are controlled. A hydraulic control device for cargo handling in which the direction is determined has been proposed.

According to this cargo handling hydraulic control device, the controller adjusts the movement amount and direction of the spool based on the operation amount of the cargo handling lever, and the ascending / descending speed of the fork is determined based on the movement amount of the spool. The ascending and descending of the fork is controlled by the moving direction of the spool. When the spool is in the neutral position, hydraulic oil is not supplied to the hydraulic cylinder, and the fork is in a stopped state.

At this time, the position of the fork when the piston comes into contact with the upper surface inside the hydraulic cylinder is the upper stroke end position, and the position of the fork when the piston comes into contact with the lower surface inside the hydraulic cylinder is the lower stroke end position. .

When the fork reaches the upper or lower stroke end position while moving up and down at a certain speed, the piston of the hydraulic cylinder collides with the inner upper surface or the lower surface of the hydraulic cylinder, and the fork suddenly stops. As a result, there is a problem that an impact occurs when the fork stops at the upper or lower stroke end position.

Similarly, for example, when the fork is automatically controlled to move up and down to stop the fork at a predetermined position within the stroke range of the fork, the fork is suddenly stopped as soon as the predetermined position is reached. Therefore, there is a problem that an impact occurs.

Therefore, a technique has been proposed in which a limit switch or the like is arranged at a position apart from the position where the fork is stopped, such as the stroke end, by a fixed distance, and the ascending / descending speed of the fork is reduced from that position.

[0008]

However, when a load or the like is placed on the fork and a certain load is applied, even if the deceleration is started from that position, the inertia (inertia Therefore, there is a problem that a large impact is generated or the fork goes too far at the position where the fork is stopped without immediately decelerating.

The present invention has been made to solve the above problems, and its purpose is to decelerate the fork from a position corresponding to the load applied to the fork, so that the fork is surely shocked. An object is to provide a hydraulic control device for cargo handling that stops a fork.

[0010]

In order to solve the above problems, a first aspect of the present invention is directed to a lift position detecting means for detecting a lift position of a fork lifted by expansion and contraction of a cylinder, and a load applied to the fork. A load detection means for detecting and a shockless start position with respect to a predetermined stop position of the fork are set based on the load applied to the fork, and after the fork passes the shockless position, the moving speed of the fork is reduced. The gist of the invention is to provide a speed control means for stopping the fork at the stop position of the fork.

A second aspect of the invention is based on the first aspect of the invention, wherein the stop position is the stroke end of the cylinder.

[0012]

Therefore, according to the first aspect of the invention, first, the load detecting means detects the load applied to the fork. At this time, the speed control means sets a shockless start position with respect to a predetermined stop position of the fork based on the load applied to the fork, and during movement of the fork, after the fork has passed the shockless start position, the fork The speed is reduced to stop the fork at the stop position of the fork.

According to the second aspect of the invention, the stop position of the fork is defined by the stroke end of the cylinder.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. As shown in FIG. 1, a cargo handling lever 1 as a cargo handling operating means is provided in a driver's seat of a forklift truck (not shown). To the cargo handling lever 1, a potentiometer 2 is connected as a cargo handling operation amount detecting means for detecting the operation amount (angle). The potentiometer 2 is connected to the controller 3 as speed control means.

Further, the forklift is provided with a mast device 4, and the mast device 4 is equipped with a fork 5 capable of moving up and down. Further, the forklift is provided with a hydraulic cylinder 6 for moving the fork 5 up and down. At this time, the lift position of the fork 5 is detected by a lift sensor 7 as a lift position detection sensor provided in the mast device 4.

The hydraulic cylinder 6 is connected to a control valve 8. Hydraulic oil is supplied to the control valve 8 by a hydraulic pump 10 which is rotationally driven by a cargo handling pump motor 9. Further, the control valve 8 is provided with a spool 11. By sliding the spool 11 in the vertical direction, the hydraulic oil supplied from the hydraulic pump 10 is supplied to the hydraulic cylinder 6, and the fork 5 moves up and down.

That is, hydraulic oil is supplied to the hydraulic cylinder 6 in an amount corresponding to the moving position of the spool 11. At this time, when the spool 11 is at the neutral position, the hydraulic oil is not supplied to the hydraulic cylinder 6 and the fork 5 is held at that position. Further, the hydraulic cylinder 6 is supplied with an amount of hydraulic oil according to the moving position of the spool 11, and the ascending / descending speed as the moving speed of the fork 5 is set according to the amount. That is, the opening of the control valve 8 is set by the moving position of the spool 11, and the ascending / descending speed of the fork 5 is set according to the opening.

At this time, the pressure sensor 12 as load detecting means for detecting the pressure applied to the hydraulic cylinder 6 is provided in the conduit V connecting the hydraulic cylinder 6 and the control valve 8.
Is provided. That is, the pressure sensor 12 detects the weight of the load as a load applied to the fork 5.

A stepping motor 13 is connected to the spool 11 via a link mechanism 14. That is, the movement control of the spool 11 is performed by the stepping motor 13
Is rotated through the link mechanism 14,
The stepping motor 13 is drive-controlled by the controller 3.

At this time, the fork 5 moves up and down within a predetermined range as a piston (not shown) of the hydraulic cylinder 6 moves within the hydraulic cylinder 6. That is,
The stroke end (upper stroke end) above the fork 5 is the position where the piston contacts the upper inner surface of the hydraulic cylinder 6, and the lower stroke end (lower stroke end) is where the piston contacts the lower inner surface of the hydraulic cylinder 6. This is the position to touch. That is, the fork 5 can be moved up and down between the upper stroke end and the lower stroke end.

Next, the electrical configuration of the cargo handling hydraulic control device configured as described above will be described. Controller 3
Is a central processing unit 15 (hereinafter referred to as CPU), a read-only memory 16 (hereinafter referred to as ROM), a readable / writable memory 17 (hereinafter referred to as RAM),
It is composed of A / D converters 18, 19, 20 and a motor drive circuit 21.

The A / D converter 18 includes a cargo handling lever 1
The potentiometer 2 provided in the is connected. A
The / D converter 18 A / D converts the operation direction and the operation angle as the operation amount of the cargo handling lever 1 detected by the potentiometer 2 with a predetermined resolution, and outputs the A / D conversion to the CPU 15.

The A / D converter 19 includes a lift sensor 7
Are connected. The A / D converter 19 converts the voltage corresponding to the lift position detected by the lift sensor 7 with a predetermined resolution.
/ D conversion and output to the CPU 15. At this time, the CPU
Reference numeral 15 indicates the elevation position of the fork 5 at that time based on the detection signal from the elevation sensor 7, and also calculates the ratio of the temporal change of the elevation position of the fork 5 to raise the fork 5. The speed and the descending speed are calculated.

The A / D converter 20 includes a pressure sensor 1
2 is connected. The A / D converter 20 uses a voltage corresponding to the pressure detected by the pressure sensor 12 with a predetermined resolution.
/ D conversion and output to the CPU 15. At this time, the CPU
Reference numeral 15 is adapted to judge the state of the load applied to the fork 5, that is, the state of the weight of the load, based on the detection signal from the pressure sensor 12.

Further, when the fork 5 is raised, the CPU 15 gradually decreases the ascending speed of the fork 5 in the vicinity of the upper stroke end in accordance with the weight of the load on the fork 5, and the piston mechanically moves to the inner surface of the cylinder upper part. The control (shockless control) is performed to mitigate the impact (shock) generated due to the collision and sudden stop of the piston. Similarly, when the fork 5 descends, the CPU 15 nears the lower stroke end and
The shockless control is performed in which the descending speed of the fork 5 is gradually reduced according to the weight of the load applied to the piston, and the shock generated when the piston mechanically collides with the inner surface of the upper part of the cylinder and suddenly stops the piston. It has become.

At this time, the CPU 15 calculates a lift position (shockless start position) separated from each upper or lower stroke end position for starting shockless control according to the weight of the load on the fork 5. ing. That is, the shockless start position is a position that is below the upper stroke end when the fork 5 is raised, and is a position that is above the lower stroke end when the fork 5 is lowered. .

As shown in FIG. 2, the ROM 16 stores a map indicating the load applied to the fork 5, that is, the shockless start position corresponding to the weight of the load. That is,
The weight of the load on the fork 5 and the shockless start position are in a proportional relationship, and the shockless start position is uniquely determined according to the weight of the load on the fork 5. At this time, with the load etc. not placed on the fork 5, that is, the shockless start position from the stroke end as the load becomes heavier with reference to the shockless start position when the fork 5 is in an unloaded state. The positions are set apart from each other, and as the weight of the load becomes lighter, the position is set closer to the shockless start position in the unloaded state (hereinafter referred to as the reference shockless start position).

Further, as shown in FIG. 3, the ROM 16 stores a map showing the opening degree of the control valve 8 after the shockless start position when the fork 5 is moved up and down.

For example, a case where the fork 9 moves up and down with the control valve 8 at the maximum opening will be described. At this time, if the fork 5 is in a no-load state, shockless control is started from the reference shockless start position, and the opening of the control valve 8 is controlled to be gradually reduced by gradually closing the spool 11. It Therefore, the ascending / descending speed of the fork 5 is gradually reduced. Then, the opening of the control valve 8 is controlled to be in a slightly opened state near the stroke end, the fork 5 is in an extremely low speed state, and at the stroke end, when the piston collides with the inner upper surface or the lower surface of the hydraulic cylinder 6. The shock is alleviated. At this time, the control valve 8 is closed by the spool 11.

When a load of a certain weight is placed on the fork 5, as shown by the broken line in FIG. 3, the stroke is greater than the reference shockless start position according to the weight of the load. The shockless start position is set at a position away from the end. Therefore, when the fork 5 moves up and down, shockless control is started earlier than when there is no load.

When the shockless control is started, the spool 11 is gradually closed to control the opening of the control valve 8 gradually as in the case of no load. Therefore, the ascending / descending speed of the fork 5 is gradually reduced. At this time, the ratio of gradually decreasing the control valve 8, that is, the fork 5
The rate of deceleration is controlled at the same rate as when there is no load.

Next, the operation and effect of the cargo handling hydraulic control device configured as described above will be described with reference to the flow chart shown in FIG. First, the operator operates the cargo handling lever 1,
The spool 11 is moved from the neutral position according to the operation amount of the cargo handling lever 1, the control valve 8 is opened, and the fork 5 is moved up and down at a speed based on the opening degree of the control valve 8. At this time, the lift sensor 7 detects the lift position of the fork 5 and outputs the detection signal to the A / D converter 1
It outputs to CPU15 via 9. Also, the pressure sensor 12
Detects the pressure applied to the hydraulic cylinder 6 and outputs the detection signal to the CPU 15 via the A / D converter 20.

Then, in step 101, the CPU 15
Determines whether the weight of the load is applied to the fork 5 based on the detection signal. At this time, if the weight of the load is applied to the fork 5, the CPU 15 causes the step 1
At 02, the shockless start position corresponding to the weight of the load is obtained based on the map shown in FIG. Also, fork 5
If the load is not loaded on the
At 3, the CPU 15 sets a predetermined reference shockless start position.

Subsequently, in step 104, the CPU 15 detects the fork 5 based on the detection signal from the lift sensor 7.
Determines whether has reached the shockless start position. When the fork 5 reaches the shockless start position, C
When the PU 15 judges, in step 105, the CPU 1
5 performs shockless control. That is, by gradually closing the spool 11, the opening degree of the control valve 8 is gradually reduced and the ascending / descending speed of the fork 5 is gradually reduced and stopped.

When the CPU 15 determines in step 104 that the fork 5 has not reached the shockless start position, the CPU 15 opens the control valve 8 based on the current operation amount of the cargo handling lever 1 in step 106. With the degree maintained, the process proceeds to step 101 again. That is, the fork 5 continues to move up and down at a speed based on the opening degree of the control valve 8.

Therefore, the shockless start position is changed based on the weight of the load on the fork 5, and the heavier the load on the fork 5, the more the shockless start position is set to a position farther from the stroke end. The lighter the weight, the closer the shockless start position is to the stroke end. Therefore, when the fork is moved up and down while a heavy load is placed on the fork 5, the shockless control is started from a position distant from the stroke end, and the fork 5 is surely moved. It can be stopped without fail in the state of softening the shock. Therefore, for example, during shockless control, it is possible to prevent the fork 5 from being gradually stopped due to the inertia of the load of the fork 5 or the like at the stroke end and suddenly stopping, and the load to be shocked. or,
When a light load or the like is placed on the fork 5, the shockless control is started from a position relatively close to the stroke end, so that the cargo handling work time can be shortened and the work efficiency can be improved. You can

In this way, the fork 5 is shocklessly controlled from the position corresponding to the weight of the load on the fork 5 and gradually decelerated, so that the fork 5 is reliably stopped at the stroke end without giving a shock. Can be made.

The present invention is not limited to the above-described embodiments, and a part of the configuration can be modified as appropriate without departing from the spirit of the present invention. (1) In the above embodiment, the lower stroke end is set to the position of the fork 5 in the state where the piston of the hydraulic cylinder 6 is in contact with the inner lower surface of the hydraulic cylinder 6, but the position where the fork 5 is in contact with the ground. It may be set to.

(2) In the above embodiment, the shock caused by the sudden stop of the fork 5 at the end of the upward or downward stroke is prevented. This may be applied, for example, when the fork 5 is automatically moved to a preset lift position when the fork 5 is moved up and down. At this time, it is possible to reduce a shock that is caused by the fork 5 suddenly stopping due to the spool 11 being suddenly positioned at the neutral position, and for example, a shock applied to a load placed on the fork 5 can be reduced.

(3) In the above embodiment, when the load placed on the pallet is lifted and lowered by the fork 5 and the load on the pallet is placed on a predetermined place such as the ground, The shockless control may be offset from the shockless start position set according to the thickness of the pallet, and the shockless control may be started from the offset position.

(4) In the above embodiment, the pressure sensor 12 is provided as the load detecting means in the pipe line V, but the hydraulic cylinder 6
It may be provided inside. In addition, a pressure sensor is provided on the fork 5 so that the weight of the load placed on the fork 5 can be determined based on the weight of the fork 5.
It may be configured to obtain the load on the.

(5) In the above embodiment, shockless control is performed when the fork 5 is raised and lowered, respectively.
The shockless control may be performed only when rising or when falling.

(6) In the above embodiment, when the weight of the load on the fork 5 is the same when the fork 5 is raised or lowered, the respective shockless start positions at the time of raising or lowering are the stroke ends. Are set at the same distance from. Even if the load applied to the fork 5 is the same when the fork 5 is raised or lowered, the shockless start position is different from the stroke end at different distances when the fork 5 is raised and lowered. It may be set to.

(7) In the above embodiment, as shown in FIG. 2, as the weight of the load placed on the fork 5 becomes heavier, the shockless start position is set to a position distant from the stroke end, and the weight is reduced. The lighter it is, the closer it is to the reference shockless start position. As shown in FIG. 5, the shockless control is started from the reference shockless start position up to a predetermined load (weight of a predetermined load), and when the load becomes equal to or more than the predetermined load, the load The shockless control may be started from the shockless start position (shockless start position under load) at.

(8) In the above embodiment, as shown in FIG. 3, the control valve 8 is provided in a slightly opened state during shockless control. However, without providing it, the fork 5 is gradually decelerated and stopped. You may let me.

(9) In the above embodiment, the rate of gradually decreasing the control valve 8 during shockless control, that is, the rate of deceleration of the fork 5 may be appropriately changed according to the magnitude of the load. Good.

(10) In the above embodiment, the hydraulic cylinder 6
However, it may be applied to a forklift that lifts and lowers the fork 5 with an electric cylinder.

(11) In the above embodiment, the present invention may be applied to a cargo handling hydraulic control device in which the shockless start position changes depending on the lifting speed of the fork 5. That is, the cargo handling according to the present invention is changed such that the shockless start position is set farther from the stroke end as the ascending / descending speed of the fork 5 is higher, and the shockless start position is set closer to the stroke end as the ascending / descending speed is slower. It may be applied to a hydraulic control device for use.

At this time, the higher the ascending / descending speed of the fork 5 is, and the heavier the load placed on the fork 5 is, the more the shockless start position is set to the position farther from the stroke end.
The lower the ascending / descending speed of the fork 5 and the lighter the weight of the load placed on the fork 5, the closer the shockless start position is to the stroke end.

[0050]

As described in detail above, according to the present invention, by decelerating the fork from the position corresponding to the load applied to the fork, the fork can be stopped without impact on the fork. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a cargo handling hydraulic control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a load applied to a fork and a shockless start position in one embodiment.

FIG. 3 is a characteristic diagram showing a relationship between an opening degree of a control valve and a lift position of a fork in one embodiment.

FIG. 4 is a flowchart showing control performed by a controller in one embodiment.

FIG. 5 is a characteristic diagram showing a relationship between a load applied to a fork and a shockless start position in another example.

[Explanation of symbols]

3 ... Controller as speed control means, 5 ... Fork, 7 ... Lift height sensor as lift position detecting means, 12 ...
A pressure sensor as load detecting means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Asada 2-1-1 Toyota-cho, Kariya city, Aichi stock company Toyota Industries Corp.

Claims (2)

[Claims] 1. A lift position detecting means for detecting a lift position of a fork lifted by expansion and contraction of a cylinder, a load detecting means for detecting a load applied to the fork, and a shockless method for a predetermined stop position of the fork. The starting position is set based on the load applied to the fork, and after the fork passes the shockless position, the moving speed of the fork is decelerated, and a speed control means for stopping the fork at the fork stop position is provided. Hydraulic control device for cargo handling. 2. The cargo handling hydraulic control device according to claim 1, wherein the stop position is a stroke end of a cylinder.