JPH06271298A - Spool movement control device for cargo handling hydraulic circuit - Google Patents

Abstract

PURPOSE:To provide a spool movement control device capable of improving the responsiveness of a cargo handling hydraulic cylinder via the control of spool movement. CONSTITUTION:A spool movement control device has ascending and descending side dead zones F1 and F2 where the piston 12a of a cargo handling hydraulic cylinder 12 does not operate, even if the spool 5 of a cargo handling hydraulic circuit 4 moves. Also, the device controls the movement of the spool 5 by driving a stepping motor 6 on the basis of the operation of a control lever 1 for the spool 5, thereby changing the direction of the piston 12a of the cylinder 12. Moreover, the device is equipped with a controller 2 for predicting the operational direction of the piston 12a of the cylinder 12, and causing the spool 5 to move to an ascending marginal position S1 with the stepping motor 6 operating under control, upon prediction of the ascending motion of the cylinder 12, while causing the spool 5 to move to a descending marginal position 82 with the stepping motor 6 operating under control, upon prediction of the descending motion of the piston 12a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spool movement amount control device in a cargo handling hydraulic circuit, and more particularly to a spool in a cargo handling hydraulic circuit for controlling the movement amount of the spool to improve the responsiveness of a cargo handling hydraulic cylinder. The present invention relates to a movement amount control device.

[0002]

2. Description of the Related Art Conventionally, a controller for controlling the driving of a stepping motor based on a lever operation amount, adjusting a spool in a cargo handling hydraulic circuit to switch a movement direction of a piston in a cargo handling hydraulic cylinder, a spool movement amount control device. Are proposed, and these devices are mounted on industrial vehicles such as forklifts. This movement amount control device is shown in FIG.

When the operation lever 1 is operated in one direction (P arrow direction), the controller 2 detects the operation amount of the operation lever 1 based on the detection signal from the potentiometer 3.
Then, the controller 2 calculates, based on the map shown in FIG. 9, how much the spool 5 of the cargo handling hydraulic circuit 4 corresponding to the operation amount of the operation lever 1 should be moved in one direction, and the stepping motor 6 Drive control.

When the stepping motor 6 is drive-controlled, the spool 5 moves in a direction corresponding to one direction (in this case, an ascending direction) via a link mechanism 9 composed of a lever 7 and a connecting rod 8. Then, since the supply pump 11 is supplying the working oil to the cargo handling hydraulic circuit 4 by driving the drive motor 10, the working oil is supplied to the first oil chamber 13 a of the cargo handling hydraulic cylinder 12. Therefore, the piston 12a of the cargo handling hydraulic cylinder 12 rises, and, for example, the fork of a forklift lifts.

When the operation lever 1 is operated in the other direction (opposite to the arrow P direction), the controller 2 detects the operation amount of the operation lever 1 based on the detection signal from the potentiometer 3. Then, the controller 2 is the operation lever 1
Based on the map shown in FIG. 9, the amount of movement in the direction corresponding to the other direction of the spool 5 of the cargo handling hydraulic circuit 4 corresponding to the operation amount is calculated based on the map shown in FIG. When the stepping motor 6 is drive-controlled, the spool 5 moves in the direction corresponding to the other direction (in this case, the descending direction) via the link mechanism 9. Then, the hydraulic oil is transferred to the second oil chamber 13b of the cargo handling hydraulic cylinder 12.
Is supplied to. Therefore, the piston 12a of the cargo handling hydraulic cylinder 12 descends, and, for example, the fork of a forklift descends.

By the way, in recent years, a forklift having a mechanism for automatically lifting the fork has been proposed. As shown in FIG. 11 and FIG. 12, this is to issue a loading instruction or a loading instruction for each of the shelves 15a to 15c of the predetermined storage rack 15.

That is, as shown in FIG. 10, the operation panel 17 includes various operation switches 18 in addition to the operation lever 1.
a, 18b, 19a to 19c are provided. Then, the operator operates, for example, the operation switch 18a for instructing the unloading work, and operates the operation switch 19b indicating that the unloading is the second-stage shelf 15b. Then,
The controller 2 drives and controls the stepping motor 6 so as to stop the fork 20 at the position shown by the chain double-dashed line in FIG. 12 based on a detection signal from a position detection device (not shown). Then, the spool 5 stopped at the neutral position is moved via the link mechanism 9, and the working oil is supplied from the cargo handling hydraulic circuit 4 to the cargo handling hydraulic cylinder 12 to cause the piston 12 to move.
a is operated.

When the fork 20 of the forklift 16 reaches the position shown by the chain double-dashed line in FIG. 12, the controller 2 stops the stepping motor 6. At this time, the spool 5 returns to the neutral position, and the fork 20 is stopped at the position shown by the chain double-dashed line. Then, the forklift 17 is moved forward to insert the fork 20 into the pallet 22 of the load 21. Then, if the operator operates the operation lever 1 and further raises the fork 20, the second stage shelf portion 15
The work of b) is completed.

On the contrary, as shown in FIG. 11, for example, in the case of a load placing work in which the load 21 held by the fork 20 is placed on the shelf 15b of the second stage, the operator instructs the load placing work by the operation switch 18b. Operation, and the loading is done on the second shelf 1
The operation switch 19b indicating 5b is operated.
Then, the controller 2 drives and controls the stepping motor 6 so as to stop the fork 20 at the position indicated by the solid line based on a detection signal from a position detection device (not shown). Then, the spool 5 stopped at the neutral position is moved via the link mechanism 9, and hydraulic oil is supplied from the cargo handling hydraulic circuit 4 to the cargo handling hydraulic cylinder 12 to supply the piston 12a.
To operate.

When the fork 20 of the forklift 16 moves to the position shown by the solid line in FIG. 11, the controller 2 stops the stepping motor 6, returns the spool 5 to the neutral position, and moves the fork 20 to the position shown by the solid line. Stop. After that, the forklift 16 is moved forward so that the load 21 corresponds to the second-stage shelf 15b. Then, when the operator operates the operation lever 1 to lower the fork 20, the load 21 is placed on the second stage shelf portion 15b, and the load placing work is completed.

[0011]

By the way, for example, referring to FIG.
As shown in FIG. 2, each of the shelves 15a to
It is assumed that the fork 20 is stopped at a height (loading position) where the fork 20 can be inserted into the pallet 22 stored in 15c. At this time, the spool 5 is stopped at the neutral position and the piston 12a and the fork 20 are held in a non-operating state. After that, the forklift 16 moves forward to insert the forks 20 into the pallets 22 of the shelves 15a to 15c. Then, the fork 20 is lifted by the operation lever 1 to perform the unloading.

In this case, the stopped fork 20 is lifted so that the fork 20 can take the load. That is,
As shown in FIG. 8, the spool 5 stopped at the neutral position
Move up. However, because of the structure of the control valve 4, switching of the communication state between the oil passage on the pump 11 side and the oil passage on the hydraulic cylinder 12 side is performed by the movement of one spool 5, so the spool 5 moves from the neutral position. Even if the hydraulic cylinder 12 is not supplied with hydraulic oil, a dead zone F1 on the rising side is generated, and the spool 5 must be moved to a position beyond the dead zone F1 on the rising side. In addition, also in the load placing work, when the load 21 is placed on the shelves 15a to 15c, the fork 20 is lowered, but the lower dead zone F2
It is necessary to move the spool 5 to a position beyond.

Therefore, since the fork 20 does not operate when the spool 5 is moving in the dead zones F1 and F2 on the ascending side and the descending side, there is a problem that the operation of the fork 20 is delayed and the responsiveness is poor.

The present invention has been made to solve the above problems, and its purpose is to predict a direction in which a piston in a cargo handling cylinder operates, and to smoothly move the cargo handling cylinder in the predicted operating direction. It is an object of the present invention to provide a spool movement amount control device in a cargo handling hydraulic circuit, which is capable of controlling movement of a spool so as to operate and improving response of a cargo handling cylinder.

[0015]

In order to solve the above problems, the present invention provides a dead zone in which a piston of a cargo handling cylinder does not operate even if a spool provided in a cargo handling hydraulic circuit moves within a predetermined range from a neutral position. A spool movement amount control device in a cargo handling hydraulic circuit for controlling the movement amount of the spool by driving a stepping motor based on the operation of the operating means, and switching the operation direction of the piston in the cargo handling cylinder. Predicting means for predicting the direction in which the piston of the cargo handling cylinder operates, and moving the spool to the point just before the piston starts operating within the dead zone of the direction in which the piston operates based on the prediction result of the predicting means. The gist of the present invention is to include a motor control means for driving and controlling the stepping motor.

[0016]

When the predicting means predicts the direction in which the piston of the cargo handling cylinder operates, the motor control means drives and controls the stepping motor to move the spool in the direction corresponding to the operating piston. This spool moves within the dead zone of the cargo handling hydraulic circuit and stops shortly before the piston begins to operate.

Therefore, when the direction in which the piston operates can be predicted from the state in which the piston of the cargo handling cylinder is stopped, the spool is moved in advance in the dead zone of the cargo handling hydraulic circuit in the direction corresponding to the desired direction of the piston. Then, the piston stops just before it starts moving. Therefore, the spool is moved just before the piston starts operating, so it is not affected by the dead zone provided in the cargo handling hydraulic circuit, and the responsiveness when operating the piston of the cargo handling cylinder in the direction predicted in advance Will get better.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the spool movement amount control device in the hydraulic circuit for cargo handling according to the present invention is applied to a forklift having an automatic lifting function will be described below with reference to FIGS. In the movement amount control device, the forklift, and the automatic lifting function, the same numbers are used for the parts having the same configurations as the conventional ones.

As shown in FIG. 1, the forklift 16 is provided with a cargo handling hydraulic cylinder 12 for moving the fork 20 up and down. The cargo handling hydraulic cylinder 12 is connected to the cargo handling hydraulic circuit 4. That is, the first oil pipe 25 connected to the cargo handling hydraulic circuit 4 is connected to the first oil chamber 13 a of the cargo handling hydraulic cylinder 12. The second oil pipe 26 connected to the cargo handling hydraulic circuit 4 is a cargo handling hydraulic cylinder 1.
2 is connected to the second oil chamber 13b. The hydraulic oil for cargo handling 4 is supplied with hydraulic oil from a supply pump 11 that is driven by the drive motor 10.

A spool 5 is provided in the cargo handling hydraulic circuit 4 so as to be movable in its axial direction. The lower end of the connecting rod 5 is connected to the tip of the spool 5 via a connecting pin 27. The upper end of the connecting rod 28 is connected to a rotating lever 30 via a connecting pin 29. The rotating lever 30 is connected to a rotating shaft 6a of a stepping motor 6 provided on the forklift 17.

Therefore, when the stepping motor 6 operates and the rotary shaft 6a rotates clockwise, the rotary lever 30
Rotates clockwise like the rotary shaft 6a. for that reason,
The spool 5 moves upward via the connecting rod 28. At this time, from the cargo handling hydraulic circuit 4 to the first
The hydraulic oil is supplied to the first oil chamber 13a via the oil pipe 25 of FIG. Therefore, the piston 12a of the cargo handling hydraulic cylinder 12 rises and the fork 20 rises.

On the contrary, when the stepping motor 6 operates and the rotary shaft 6a rotates counterclockwise, the rotary lever 30 rotates counterclockwise like the rotary shaft 6a. for that reason,
The spool 5 is adapted to move downward via the connecting rod 28. At this time, from the loading hydraulic circuit 4 to the second
The hydraulic oil is supplied to the second oil chamber 13b via the oil pipe 26 of FIG. Therefore, the piston 12a of the cargo handling hydraulic cylinder 12 descends and the fork 20 descends.

When the operation of the stepping motor 6 is stopped, the spool 5 of the cargo handling hydraulic circuit 4 is stopped at the neutral position by the urging force of a spring (not shown).

Further, an ascending side critical position S1 is provided above the neutral position, and even if the spool 5 moves from the neutral position to the ascending side critical position S1, the hydraulic oil is transferred from the cargo handling hydraulic circuit 4 to the first position. No hydraulic oil is supplied to the oil chamber 13a. Therefore, the rising side dead zone F1 in which the fork 20 does not rise is set. When the spool 5 moves upward from the ascending-side critical position S1, the cargo handling hydraulic circuit 4 moves to the first position.
The hydraulic oil is supplied to the oil chamber 13a.

Further, a descending side critical position S2 is provided below the neutral position. Even if the spool 5 moves from the neutral position to the descending side critical position S2, the hydraulic oil is transferred from the cargo handling hydraulic circuit 4 to the second position. No hydraulic oil is supplied to the oil chamber 13b. Therefore, the descending side dead zone F2 in which the fork 20 does not descend is set. Then, when the spool 5 moves below the lower critical position S2, hydraulic oil is supplied from the cargo handling hydraulic circuit 4 to the second oil chamber 13b.

The stepping motor 6 is driven and controlled by a controller 2 provided on the forklift 16 as a motor control means. The potentiometer 3 of the operating lever 1 is connected to the controller 2 as an operating means for raising or lowering the fork 20. When the operation lever 1 is operated, a detection signal based on the operation amount is output from the potentiometer 3 to the controller 2.

The controller 2 is adapted to calculate the movement amount of the spool 5 based on the operation amount of the operation lever 1 on the basis of a map shown in FIG. The controller 2 drives and controls the stepping motor 6 so as to move the suspension 5 by the calculated movement amount.

The controller 2 is instructed as to the operation switch 18a as a predicting means for instructing the taking of goods, the operation switch 18b as a predicting means for instructing the placing of goods, and the number of shelves 19a-19c. Operation switch 1
9a to 19c are respectively connected.

The operation switch 1 for instructing the unloading
After the operation of 8a, if the operation switch 19b for instructing the second stage is operated, as shown in FIG.
The controller 2 is configured to determine that the work is a work of picking up the load 21 of 5b. Then, the controller 2 moves the fork 20 to a position where the fork 20 can be inserted into the pallet 22 of the load 21 stored in the shelf 15b of the second stage and stops it.

That is, the controller 2 detects the position of the fork 20 based on a detection signal from a position detecting device (not shown). Then, in order to move the fork 20 from that position to the position shown by the chain double-dashed line in FIG. 12, the stepping motor 6 is drive-controlled, the spool 5 is moved, and the piston 12a of the cargo handling cylinder 12 is operated.

At this time, the controller 2 has determined that it is a unloading operation, and it is known that the fork 20 is lifted in order to carry out the unloading next time. Therefore, the controller 2 drives and controls the stepping motor 6 to move the spool 5 upward. Then, as shown in FIG. 2, when the spool 5 reaches the ascending-side critical position S1, which is a position just before the hydraulic oil for cargo handling is supplied to the hydraulic cylinder for cargo handling 12 from the cargo handling hydraulic circuit 4, the controller 2 causes the stepping motor 6 to operate. Through spool 5
It is supposed to stop the movement of. Then, the controller 2 drives and controls the stepping motor 6 so as to maintain the spool 5 stopped at the rising critical position S1.

In this state, when the forklift 16 moves forward and the fork 20 is inserted into the pallet 22 of the shelf 15b, and then the operating lever 1 is operated to the upside, the controller 2 causes the potentiometer 3 to detect the amount of operation. The movement amount of the spool 5 is calculated based on the detection signal based on the map shown in FIG. Then, the controller 2 drives and controls the stepping motor 6 so as to move the spool 5 by the calculated movement amount.

Then, the spool 5 moves to the upper critical position S1.
Moving upward, from the cargo handling hydraulic circuit 4 to the first oil pipe 2
5 through the first oil chamber 13a of the hydraulic cylinder 12 for cargo handling
Is supplied with hydraulic oil, and the fork 20 rises. Therefore, the shelf 15b is loaded.

On the contrary, the operation switch 18 for instructing the load placement
After operating b, for example, if the operation switch 19b for instructing the second stage is operated, as shown in FIG.
Controller 2 that the load is placed on the load 21
Is supposed to judge. Then the controller 2
Is configured to move the pallet 22 of the load 21 held by the fork 20 to a position slightly higher than the height of the second-stage shelf 15b and stop it. That is, the controller 2 detects the position of the fork 20 based on a detection signal from a position detection device (not shown). And from that position,
In order to move the fork 20 to the position indicated by the solid line 1, the controller 2 drives and controls the stepping motor 6, moves the spool 5, and operates the piston 12a of the cargo handling hydraulic cylinder 12.

At this time, the controller 2 has determined that it is a load placing operation, and it is known that the fork 20 is lowered in order to perform the load placing next. Therefore, the controller 2 drives and controls the stepping motor 6 to move the spool 5 downward. Then, as shown in FIG. 4, when the spool 5 reaches the descending side critical position S2, which is a position just before the hydraulic fluid for cargo handling is supplied to the hydraulic cylinder for cargo handling 12 from the cargo handling hydraulic circuit 4, the controller 2 causes the stepping motor 6 to operate. Through spool 5
It is supposed to stop the movement of. Then, the controller 2 drives and controls the stepping motor 6 so that the spool 5 is maintained in the stopped critical position S1.

In this state, when the forklift 16 moves forward and the fork 20 is inserted into the shelf 15b, and then the operation lever 1 is operated to the lower side, the controller 2 outputs a detection signal based on the operation amount from the potentiometer 3. Based on this, the movement amount of the spool 5 is calculated based on the map shown in FIG. Then, the controller 2 drives and controls the stepping motor 6 so as to move the spool 5 by the calculated movement amount.

Then, the spool 5 moves to the lower critical position S2.
It moves further downward, and from the hydraulic circuit 4 for cargo handling to the second oil pipe 2
The second oil chamber 13b of the hydraulic cylinder 12 for cargo handling via 6
The hydraulic oil is supplied to the fork 20, and the fork 20 descends. Therefore, the load is placed so that the load 21 is placed on the shelf 15b.

Next, the operation of the forklift constructed as above will be described. First, as shown in FIG. 1, normally, the spool 5 of the cargo handling hydraulic circuit 4 is stopped at the neutral position by the urging force of a spring (not shown). Therefore, the first and second oil chambers of the cargo handling hydraulic cylinder 12 are stopped. Thirteen
No hydraulic oil is supplied to a and 13b. Therefore, the fork 20 is stopped so as to maintain that state.

In this state, the forklift 16 first stops at the front of the storage shelf 15 and operates the operation switch 18a for instructing the unloading work in order to perform the unloading work, and then, for example, the second-stage shelf 15b. Instructing operation switch 19
Operate b. Then, the controller 2 detects the position of the fork 20 based on a detection signal from a position detection device (not shown).

Then, in order to move the fork 20 from that position to the position shown by the chain double-dashed line in FIG. 12, the controller 2 drives and controls the stepping motor 6 to move the spool 5. Therefore, hydraulic oil is supplied from the cargo handling hydraulic circuit 4 to the cargo handling hydraulic cylinder 12. And 2
Pallet 2 of the load 21 stored in the shelf 15b
2. Stop at a position where the fork 20 can be inserted into 2.

In the controller 2, since the operation switch 18a for instructing the unloading work is operated, it is predicted that the fork 20 will move up next. Therefore, the controller 2 drives and controls the stepping motor 6 to move the spool 5 upward. Then, as shown in FIG. 2, hydraulic fluid is supplied from the cargo handling hydraulic circuit 4 to the cargo handling hydraulic cylinder 12, that is, the controller 2 reaches the ascending side critical position S1 just before the fork 20 starts to rise. The spool 5 is moved, and when the spool 5 is located at the rising critical position S1, the stepping motor 6 is stopped to stop the spool 5 at the rising critical position S1.

On the other hand, the forklift 16 moves forward to unload the shelf 15b, and inserts the fork 20 into the pallet 22 of the load 21 stored in the shelf 15b. Then, the operation lever 1 is operated in the direction in which the fork 20 moves up. The controller 2 controls the spool 5 based on the detection signal from the potentiometer 3 based on the manipulated variable.
The movement amount of is calculated based on the map shown in FIG. The controller 2 drives and controls the stepping motor 6 so as to move the spool 5 by the calculated movement amount.

Then, as shown in FIG. 3, the spool 5 moves upward from the ascending side critical position S1, and the cargo handling hydraulic circuit 4 passes from the cargo handling hydraulic circuit 4 through the first oil pipe 25.
Hydraulic oil is supplied to the first oil chamber 13a of the fork 20
Rises. Therefore, the rack 15b is unloaded.

On the other hand, the forklift 16 stops at the front of the storage rack 15, and the load 21 of the fork 20 is loaded. Therefore, the operation switch 18b for instructing the load operation is operated, and then, for example, 2 The operation switch 19b for instructing the shelf section 15b of the stage is operated. Then, the controller 2 detects the position of the fork 20 based on a detection signal from a position detection device (not shown).

Then, in order to move the fork 20 from that position to the position shown by the solid line in FIG. 11, the controller 2 drives and controls the stepping motor 6 to move the spool 5. Therefore, hydraulic oil is supplied from the cargo handling hydraulic circuit 4 to the cargo handling hydraulic cylinder 12. Then, the pallet 22 of the load 21 held by the fork 20 stops at a position slightly higher than the height of the shelf 15b of the second stage.

In the controller 2, since the operation switch 18b for instructing the load placing work is operated, it is predicted that the fork 20 will descend next. Therefore, the controller 2 drives and controls the stepping motor 6 to move the spool 5 downward. Then, as shown in FIG. 4, just before the hydraulic oil for cargo handling is supplied from the cargo handling hydraulic circuit 4 to the cargo handling hydraulic cylinder 12, that is, the controller 2 is on the descent side critical position S2 just before the fork 20 starts to descend.
The spool 5 is moved up to, and when the spool 5 is located at the lower critical position S2, the stepping motor 6 is stopped to stop the spool 5 at the lower critical position S2.

On the other hand, the forklift 16 moves forward to place a load on the shelf 15b and moves the fork 20 having the load 21 on the shelf 15b. Then, the operation lever 1 is operated in the direction in which the fork 20 descends. The controller 2 calculates the movement amount of the spool 5 based on the detection signal from the potentiometer 3 based on the operation amount based on the map shown in FIG. 9, and moves the spool 5 by the calculated movement amount. Drive control.

Then, as shown in FIG. 5, the spool 5 moves downward from the lower critical position S2, and the cargo handling hydraulic circuit 4 passes from the cargo handling hydraulic circuit 4 via the second oil pipe 26.
Hydraulic oil is supplied to the second oil chamber 13b of the fork 20
Goes down. Therefore, the load 2 carried by the fork 20
1 is placed on the shelf 15b.

Therefore, when the controller 2 predicts that the fork 20 will rise, the controller 2 moves the spool 5 upward and stops it at the ascending side critical position S1. Then, when the operating lever 1 is operated to raise the fork 20, the spool 5 moves to the ascending side critical position S1.
The hydraulic oil for cargo handling is immediately supplied from the hydraulic circuit for cargo handling 4 to the hydraulic cylinder for cargo handling 12 so that the fork 20
Rises. As a result, the spool 5 moves to the rising dead zone F1.
Since it has passed through in advance and is stopped at the ascending-side critical position S1, it is possible to improve the responsiveness when the fork 20 is raised.

Similarly, when the controller 2 predicts that the fork 20 descends, the controller 2 moves the spool 5 downward and stops it at the descending side critical position S2. Then, when the operation lever 1 is operated to lower the fork 20, the spool 5 moves to the lower critical position S2.
The hydraulic oil for cargo handling is immediately supplied from the hydraulic circuit for cargo handling 4 to the hydraulic cylinder for cargo handling 12 so that the fork 20
Goes down. As a result, the spool 5 is moved to the descending dead zone F2.
Is passed in advance and stopped at the descending side critical position S2, so that the responsiveness can be improved when the fork 20 is lowered.

Moreover, when the operation direction of the fork 20 can be predicted in advance, it is not affected by the ascending-side dead zone F1 and the descending-side dead zone F2 of the spool 5, so that the characteristic indicating the supply amount of hydraulic oil with respect to the moving amount of the spool 5 is The characteristics shown by the chain double-dashed line in FIG. 7 can be obtained.

In the present embodiment, the operation switch 18a for instructing the unloading operation and the operation switch 18 for instructing the unloading operation.
Predicted based on b. In addition to this, as shown in FIG.
An ascending side end switch 33 that detects that the fork 20 is located at the uppermost end and a descending side end switch 34 that detects that the fork 20 is located at the lowermost end are added. Then, it is possible to further accurately predict the operation direction of the fork 20 based on these detection signals. Further, this configuration may be such that the elevation of the fork 20 is detected by a potentiometer or an encoder, and this may be performed based on the detected value.

Further, in the present embodiment, the movement amount of the spool 5 for operating the cargo handling hydraulic cylinder 12 is controlled by predicting the rise and fall of the fork 20 in the forklift 17, but in addition to this, a tilt cylinder or a reach cylinder may be used. It is also possible to predict the movement directions of the above and control the movement amount of the spool for operating these.

[0054]

As described in detail above, according to the present invention, the direction in which the piston in the cargo handling cylinder operates is predicted, and the spool movement is controlled so that the cargo handling cylinder operates smoothly in the predicted operating direction. Therefore, there is an excellent effect that the response of the cargo handling cylinder can be improved.

[Brief description of drawings]

FIG. 1 is an electric block diagram showing a configuration of a spool movement amount control device in a cargo handling hydraulic circuit according to the present invention.

FIG. 2 is a configuration diagram showing a state in which a spool is stopped at a rising side critical position.

FIG. 3 is a configuration diagram showing a state in which a spool is moved upward from a rising side critical position to supply hydraulic oil to a cargo handling cylinder.

FIG. 4 is a configuration diagram showing a state in which a spool is stopped at a lower critical position.

FIG. 5 is a configuration diagram showing a state in which a spool is moved downward from a lower critical position to supply hydraulic oil to a cargo handling cylinder.

FIG. 6 is an electric block diagram showing a configuration of a spool movement amount control device in a cargo handling hydraulic circuit showing another example of the present invention.

FIG. 7 is a map diagram for calculating a movement amount of a spool with respect to a lever operation amount.

FIG. 8 is an electric block diagram showing a configuration of a spool movement amount control device in a conventional cargo handling hydraulic circuit.

FIG. 9 is a map diagram for calculating a movement amount of a spool with respect to a lever operation amount.

FIG. 10 is a configuration diagram showing a state in which the mechanical configuration of the automatic lifting device is provided on a panel of a forklift.

FIG. 11 is an explanatory diagram showing that the second shelves of the storage shelves are loaded.

FIG. 12 is an explanatory diagram showing that the load stored in the second shelf of the storage rack is unloaded.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Operating lever as operation means, 2 ... Controller as prediction means and motor control means, 4 ... Cargo handling hydraulic circuit, 5 ... Spool, 6 ... Stepping motor, 12 ... Cargo handling hydraulic cylinder, 12a ... Piston, F1 ... Ascending side dead zone, F2 ... Descent side dead zone, S1 ... Ascending side critical position, S
2 ... Downward critical position

Claims (1)

[Claims] 1. A stepping motor based on the operation of operating means, wherein the spool provided in the cargo handling hydraulic circuit has a dead zone in which the piston of the cargo handling cylinder does not operate even if the spool moves within a predetermined range from the neutral position. Is a movement amount control device for a spool in a cargo handling hydraulic circuit for controlling the movement amount of the piston in the cargo handling cylinder by switching the movement direction of the piston, and predicting means for predicting a direction in which the piston of the cargo handling cylinder operates. And a motor control means for driving and controlling the stepping motor so as to move the spool just before the piston starts operating within a dead zone in the direction in which the piston operates based on the prediction result of the prediction means. Moving amount control device.