JPH08677B2 - Forklift load / push control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention is designed so that a face on a fork claw is moved back and forth to pull up a load on a slip sheet onto the fork or push it out from the fork for cargo handling work. Load push-pull control device for forklift trucks.

2. Description of the Related Art Many load push / pull control devices are known. Among them, the one in which the forward / backward movement of the face is synchronized with the forward / backward movement of the vehicle body is disclosed in, for example, Japanese Utility Model Publication No. 58-4599 and Japanese Utility Model Publication No.
There are 58-4600 and 58-7797.

Problems to be Solved by the Invention Even if the forward / backward movement of the face can be operated synchronously with the longitudinal movement of the vehicle body by automatic control, hydraulic oil is supplied at a predetermined pressure to the push-side oil chamber or the pull-side oil chamber of the push-pull cylinder. Then, the push-pull cylinder makes a full stroke at a constant speed to determine the stroke end of the face.
The stroke of the face is suddenly performed to generate an impact, which may cause collapse of the load or damage of the load.

Therefore, the present invention provides a load push / pull control device for a forklift truck that can avoid the occurrence of impact at the end of the stroke of the face.

Means for Solving the Problems The present invention prevents a shock at the stroke end of the face in a forklift in which a push-pull device for moving a face forward and backward on a fork by a push-pull cylinder is arranged in the front part of the vehicle body. A stroke end shock prevention device is provided, and the stroke end shock prevention device is interlocked with a pump that is driven to rotate forward and backward in accordance with forward and reverse rotation of the wheel using the rotation of the wheel as a drive source and forward and reverse rotation drive of the pump. And an oil discharger composed of a switching valve for switching operation. The two ports of the oil discharger and the oil chamber of the push-pull cylinder are connected by pipes respectively, and the operation from the oil discharger is performed. An automatic control device that extends and retracts the push-pull cylinder by supplying and discharging oil, and at least the face Face movement amount detector that detects that it is located near the weekend, and operation stop that stops the supply and discharge of hydraulic oil from the automatic control device to the push-pull cylinder based on the detection output of the face movement amount detector And means.

The operation stopping means is a clutch that is interposed in a transmission path that transmits the rotation of the wheel to the pump and that disconnects the power transmission path between the wheel and the pump based on the detection output of the face movement amount detector. Or a bypass passage interconnecting the pipes that respectively connect the two ports of the oil discharger and the oil chamber of the push-pull cylinder, and the face movement provided in this bypass passage. The flow control valve is configured to open based on the detection output of the quantity detector so that the pipes between the oil discharger and the push-pull cylinder communicate with each other through the bypass passage. be able to.

Further, the operation stopping means is provided in the middle of a pipe connecting each of the two ports of the oil discharger and the oil chamber of the push-pull cylinder, and is based on the detection output of the face movement amount detector. It is also possible to use a bypass switching valve that cuts off the communication between the port on the oil discharger side and the oil chamber of the push-pull cylinder by switching operation, and allows the ports on the oil discharger side to communicate with each other.

Action When the face is near the stroke end, this is detected by the face movement amount detector, and the operation stopping means operates based on the detection output of this face movement amount detector, and the automatic control device sends a push-pull cylinder to the push-pull cylinder. Immediately stop the supply and discharge of hydraulic oil. As a result, the operation of the push-pull cylinder is stopped before the stroke end, and the impact at the stroke end is reduced.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a push-pull device arranged at the front part of a vehicle body 7. This push-pull device 1 is a push-pull device for extending and retracting a link mechanism 3 to move a face 4 forward and backward on a fork 5. A cylinder 2 and a gripper 6 that is connected in parallel with the push-pull cylinder 2 and holds and releases a slip sheet (not shown) are provided. In the present embodiment, the push-pull device 1 can be operated by the automatic control device 8 in synchronism with the longitudinal movement of the vehicle body 7.

The automatic control device 8 responds to the rotation of the wheels W of the forklift truck, and supplies the hydraulic oil supplied from the pump 10 driven by the engine 9 to the push-pull cylinder 2 and the gripper 6, and A flow control valve 12 provided in the bypass passage 35 between the oil discharger 11 and the push-pull device 1 is provided.

The oil discharger 11 is positive or negative depending on whether the wheel W rotates normally or reversely.
The pump 13 is driven in reverse rotation, and the switching valve 14 is switched in conjunction with forward and reverse rotation drive of the pump 13. The switching valve 14 moves the hydraulic fluid discharged from the pump 13 to the pull side of the push-pull cylinder 2 when the vehicle body 7 moves forward, and the hydraulic fluid discharged from the pump 13 to the push side of the push-pull cylinder 2 when the vehicle body 7 moves backward. Switch to supply. The driving of the pump 13 is controlled by an electromagnetic clutch 15 which is operated via a controller 17 by operating a synchronous operation switch 16.

The flow rate control valve 12 includes a vehicle body movement amount detector 18 that detects the movement amount of the vehicle body 7 based on the rotation amount of the wheels W, and a face movement amount detector that detects the movement amount of the face 4 based on the extension / contraction amount of the link mechanism 3. The flow rate control valve 12 opens to open the hydraulic fluid when the movement of the face 4 is too fast with respect to the movement of the vehicle body 7 by controlling the opening and closing via the controller 17 based on the detection action with the vehicle. A part of it is relieved so that the movement of the face 4 is synchronized with the movement of the vehicle body 7.

20 is a sequence valve for gripping and activating the gripper 6 prior to the pulling operation of the push-pull cylinder 2, and 21 is the vehicle body 7.
Is a flow rate adjusting valve for avoiding a delay in pushing out the face 4 by reducing the amount of hydraulic oil supplied to the gripper 6 side and immediately pushing the push-pull cylinder 2 during backward movement. Reference numeral 22 is a control valve for operating the push / pull cylinder 2, lift cylinder 23, and tilt cylinder 24, and a dedicated push / pull valve 25, lift valve 26, and tilt valve 27 are provided side by side.

In this embodiment, the switching valve 14 of the oil discharger 11 is connected to the hydraulic oil carryover circuit 28 of the control valve 22 so that the hydraulic oil carried over from the control valve 22 is supplied to the oil discharger 11. Therefore, the correction operation by the control valve 22 can be prioritized.
Reference numeral 29 is a power steering cylinder, 30 is a switching valve for the same, 31 is a flow dividing valve for dividing hydraulic oil between the control valve 22 side and the switching valve 30 side, and 32 is a reservoir tank.

Here, in the present embodiment, the automatic control device 8 described above is effectively used, and the electromagnetic clutch 15 is used as the operation stopping means 33 so that the automatic control device 8 and the face movement amount detector can be used.
19 and the electromagnetic clutch 15 as the operation stopping means 33 constitute a stroke end shock prevention device, and the operation of the oil discharger 11 is stopped near the stroke end of the face 4 based on the detection action of the face movement amount detector 19. I am allowed to do it. That is, when the face movement amount detector 19 detects that the face 4 reaches near the stroke end,
The electromagnetic clutch 15 of the oil discharger 11 is disengaged via the controller 17 to release the power transmission to the pump 13.

According to the apparatus of the above embodiment, by turning on the synchronous operation switch 16, the electromagnetic clutch 15 is connected via the controller 17, and the power transmission system between the pump 13 of the oil discharger 11 and the wheel W is continued. .

When the vehicle body 7 slowly moves forward to load the luggage, the pump 13 rotates in the normal direction as the wheels W rotate in the normal direction, and at the same time, the switching valve 14 switches from the neutral position to the pull side to push the hydraulic oil into the push-pull cylinder 2. The hydraulic oil is supplied to the gripper 6 earlier than the pulling operation of the push-pull cylinder 2 by the sequence valve 20, and the gripper 6 grips the slip sheet (not shown) and simultaneously pushes and pulls it. The cylinder 2 pulls to move the face 4 backward. Therefore, the forward movement of the vehicle body 7 and the pulling operation of the load by the push-pull device 1 allow the load to be taken in on the fork 5 in a fixed position.

Here, since the push-pull cylinder 2 is a single rod, the volume of the pull-side oil chamber is smaller than the volume of the push-side oil chamber, and the amount of hydraulic oil supplied from the oil discharger 11 causes the pull-operation to be performed more than the push-operation. However, the vehicle body movement amount detector 18 and the face movement amount detector 19 detect this shift promptly, and the controller 17 passes through the controller 17. As a result, the flow rate control valve 12 is opened and a part of the hydraulic oil is relieved, so that the forward movement of the vehicle body 7 and the backward movement operation of the face 4, that is, the pulling operation of the load, are kept in synchronization.

At the time of unloading, when the vehicle body 7 moves backward, the hydraulic oil is supplied to the gripper 6 and the push side of the push-pull cylinder 2 by the reverse rotation of the pump 13 of the oil discharger 11 and the push side switching of the switching valve 14. Simultaneously with the release of the slipper seat, the face 4 is moved forward, and the load is unloaded from the fork 5 in the fixed position.

When the face 4 reaches the vicinity of the stroke end in the process of operating the push-pull device 1 in the synchronous mode,
The position of the face 4 is detected by the face movement amount detector 19, a detection signal is sent to the controller 17, and the electromagnetic clutch 15 of the pump 13 is disengaged via the controller 17.

Therefore, since the operation of the oil discharger 11 is stopped near the stroke end of the face 4 and the supply of hydraulic oil to the push-pull cylinder 2 is stopped, the push-pull cylinder 2 is stopped immediately before the full stroke, Therefore, stroke end shock can be prevented.

In the embodiment described above, the electromagnetic clutch 15 is used as the operation stopping means 33 of the stroke end shock prevention device, and the electromagnetic clutch 15 is used to pump the wheel 13 from the wheel W to the pump 13 of the oil discharger 11.
However, the flow control valve 12 can be effectively used instead of the electromagnetic clutch 15 as the operation stopping means 33.

That is, based on the detection action of the face movement amount detector 19 near the stroke end of the face 4, the controller
By opening the flow rate control valve 12 via 17 to reduce the amount of hydraulic oil supplied, it is possible to slow the operating speed before the full stroke of the push-pull cylinder 2 and prevent stroke end shock.

In some cases, the oil discharger 11 may be stopped near the stroke end and the flow rate control valve 12 may be opened to control the hydraulic oil supply to prevent the stroke end shock.

In the embodiment shown in FIG. 2, a face movement amount detector is used as the operation stopping means 33 of the stroke end shock prevention device.
A bypass switching valve 34 is used which operates based on the detection action of 19 to operate via the controller 17 to cut off the supply of hydraulic oil to the push-pull cylinder 2 side.

According to this embodiment, when the face 4 reaches the vicinity of the stroke end, the switching valve 34 is switched to the bypass position via the controller 17 by the detecting action of the face movement amount detector 19, and the push / pull cylinder 2 is operated. The oil supply is cut off immediately. Therefore, the push-pull cylinder 2 is completely stopped immediately before the full stroke to prevent a stroke end shock.

As described above, according to the present invention, when the face reaches the vicinity of the stroke end, the operation stopping means of the stroke end shock prevention device is activated based on the detection action of the face movement amount detector, and the push / push is immediately performed. The supply of hydraulic oil to the pull cylinder is cut off and the operation of the push / pull cylinder is stopped.Therefore, the push / pull cylinder makes a full stroke vigorously while synchronizing the forward / backward movement of the face and the forward / backward movement of the vehicle body. It is possible to reliably prevent the stroke end shock, and therefore it is possible to avoid damage to the load or collapse of the load, and to further enhance safety and reliability, which is a great practical effect. Have.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram showing a different example of the present invention. 1 ... push / pull device, 2 ... push / pull cylinder, 4 ... face, 5 ... fork, 7 ... body,
8 ... Automatic control device, 11 ... Oil discharge device, 12 ... Flow control valve, 13 ... Pump, 14 ... Switching valve, 15 ... Electromagnetic clutch, 19 ... Face movement amount detector, 33 ... Deactivating means, 34 ... Bypass switching valve, 35 ... Bypass passage.

Claims (4)

[Claims] 1. A forklift in which a push-pull device for moving a face forward and backward on a fork by a push-pull cylinder is arranged in a front part of a vehicle body, and a stroke end shock prevention device for preventing a shock at a stroke end of the face is provided. This stroke end shock preventive device uses a rotation of the wheel as a drive source to drive the wheel in forward and reverse rotations according to forward and reverse rotations of the wheel, and to perform switching operation in conjunction with forward and reverse rotation drive of the pump. And an oil discharger composed of a switching valve for switching the oil discharger, and two ports of the oil discharger and the oil chamber of the push-pull cylinder are connected by pipes, respectively, to supply and discharge the working oil from the oil discharger. An automatic control device for expanding and contracting the push-pull cylinder by means of: A face movement amount detector for detecting that it is located at, and an operation stopping means for stopping the supply and discharge of hydraulic oil from the automatic control device to the push-pull cylinder based on the detection output of the face movement amount detector, A load push-pull control device for a forklift, which is characterized by comprising 2. The operation stop means is interposed in a transmission path for transmitting the rotation of the wheel to the pump, and the power transmission path between the wheel and the pump is provided on the basis of the detection output of the face movement amount detector. The load push-pull control device for a forklift according to claim 1, characterized in that it is a clutch for releasing the connection. 3. The operation stopping means is provided in a bypass passage for interconnecting pipes respectively connecting two ports of the oil discharger and an oil chamber of the push-pull cylinder, and the bypass passage. And a flow rate control valve that causes the pipes between the oil discharger and the push-pull cylinder to communicate with each other via the bypass passage by performing an opening operation based on the detection output of the face movement amount detector. The load push-pull control device for a forklift according to claim 1, wherein the load push-pull control device is provided. 4. The operation stopping means is provided in the middle of a pipe connecting the two ports of the oil discharger and the oil chamber of the push-pull cylinder, respectively, and the detection output of the face movement amount detector. By-pass switching valve that cuts off the communication between the port on the oil discharger side and the oil chamber of the push-pull cylinder by switching operation based on the above, and makes the ports on the oil discharger side communicate with each other. A load push / pull control device for a forklift according to claim 1.