JPS6316587Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic circuit device for a tailgate lifter of a vehicle.

Conventionally, it is known that the rear enclosure plate of a vehicle, that is, the tailgate, is raised and lowered for loading and unloading heavy goods, and is raised and lowered to facilitate cargo handling, but the hydraulic circuit device that drives the tailgate is In order to raise and lower the gate and to tilt it up and down, two cylinders, a lift cylinder a and a tilting cylinder b, are provided as shown in the first diagram, and each cylinder a and b is connected to a main circuit d connecting this and a hydraulic pump c. By operating the intervening operation switching valve e, the extension operation is carried out sequentially, and by switching the operation switching valve e and the discharge switching valve g of the discharge circuit f branched from the main circuit d, the flow rate control valve h is operated. In general, each cylinder a, b is sequentially compressed through the compressor. Therefore, during the reduction operation, not only the discharge switching valve g must be operated, but also the operation switching valve e must be switched after confirming that the cylinder a has been reduced, which is disadvantageous in that the operation is complicated. It is desirable to have this done automatically.

The present invention aims to satisfy these demands, and includes a lift cylinder 1 for raising and lowering the tailgate and a tilting cylinder 2 for raising and lowering the tailgate, and operates both cylinders 1 and 2. It is connected to a hydraulic pump 5 via a switching valve 3 and a check valve 4, and the operating switching valve 3 and check valve 4
From the main circuit 6 between the discharge switching valve 7 and the flow control valve 8
In the hydraulic circuit in which the discharge circuit 9 is branched, the circuits 10 and 11 connecting each cylinder 1 and 2 and the operation switching valve 3 are connected to each other by a connection circuit 12,
A first position 14 is provided in the connecting circuit 12 with a check valve 13 that allows flow from the circuit 11 to the circuit 10 and is moved by the pressure of the main circuit 6 acting via a pilot circuit 15 to interrupt the flow. second position 16
A hydro switching valve 17 and a throttle 18 are provided.

FIG. 2 shows an embodiment of the invention, in which the tilting cylinder 2 is configured as a multi-stage cylinder, and the tailgate is raised and lowered by the projection and retraction of the first stage 2a, and the projection and retraction of the second stage 2b. Tailgate now tilts. The operation switching valve 3 and the discharge switching valve 7 are assumed to be electromagnetically operated, and the operation switching valve 3 normally connects the main circuit 6 to the lifting cylinder 1, but when energized, it connects the main circuit 6 to the tilting cylinder 2. The discharge switching valve 7 normally cuts off the flow from the main circuit 6 to the tank 19, but when it is energized, it communicates with the tank 19. 20 is a safety valve.

To explain its operation, when the hydraulic pump 5 is driven in the state shown in the second diagram, fluid is supplied to the lift cylinder 1 through the main circuit 6, which expands and the tailgate that is on the ground continues to rise. When the operation switching valve 3 is switched, the tilting cylinder 2 extends to raise the tailgate, and this operation is substantially the same as the conventional one. In the case of the present invention, when lowering the tailgate and then tilting the tailgate, only the switching operation of the discharge switching valve 7 is sufficient, and there is no need to excite the operation switching valve 3, and the cylinders 1 and 2 are automatically moved. The operation is as follows.

When the discharge switching valve 7 is energized and the discharge circuit 9 is opened, the pressure fluid of the extended lift cylinder 1 flows to the tank 19 via the circuit 10 and the main circuit 6, and the cylinder 1 is contracted. In this case, the flow rate flowing through the discharge circuit 7 is restricted by the flow control valve 8, so that a compensating pressure set by the valve 8 is generated in the main circuit 6, and this pressure moves the hydro-switching valve 17 to the second position. 16, the connection between the tilting cylinder 2 and the main circuit 6 is cut off, and the cylinder 2 does not perform the contraction operation. When the lift cylinder 1 is fully compressed, there is no fluid flow in the main circuit 6, so that the pressure in the main circuit 6 drops to atmospheric pressure. Along with this, the pressure in the pilot circuit 15 also decreases, so the hydro switching valve 17 returns to the normal first position 14, and the tilting cylinder 2 communicates with the tank 19 via the connection circuit 12 to automatically perform a reduction operation. . In this case, the main circuit 6
The throttle 18 controls the flow rate so that no pressure is generated that would cause the hydro switching valve 17 to switch. In the first position 14 of the hydro switching valve 17, the check valve 13
This prevents reverse flow from the circuit 10 to the circuit 11, and prevents the cylinder 2 during the contraction operation from inadvertently moving backward.

In this way, in the present invention, each cylinder 1, 2
A connecting circuit 12 is provided to connect the hydraulic switching valve 17 and the throttle 18 which are operated by the pressure of the main circuit 6.
A first position 14 in which the hydro switching valve 17 allows flow from the tilting cylinder 2 to the main circuit 6, and a second position 16 in which the flow is blocked.
The cylinders 1 and 2 are automatically switched to reduce the cylinders 1 and 2 in sequence, and the operation is simplified as it is enough to operate the discharge switching valve 7, and the hydro switching valve 17 is controlled by the hydraulic signal. Because it operates, it does not require any electrical control equipment and has the advantage of being able to manufacture hydraulic circuits at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram of a conventional example, and FIG. 2 is a diagram of an embodiment of the present invention. 1... Lifting cylinder, 2... Tilting cylinder, 3... Operation switching valve, 4... Check valve,
5...Hydraulic pump, 6...Main circuit, 7...Discharge switching valve, 8...Flow rate control valve, 9...Discharge circuit, 1
0, 11...Circuit, 12...Connection circuit, 13...
Check valve, 14...first position, 15...pilot circuit, 16...second position, 17...hydro switching valve, 18...throttle.

Claims (1)

[Scope of utility model registration request] It is equipped with a lift cylinder 1 for raising and lowering the tailgate and a tilting cylinder 2 for raising and lowering the tailgate.
In a hydraulic circuit in which a discharge circuit 9 equipped with a discharge switching valve 7 and a flow rate control valve 8 is branched from a main circuit 6 between the actuation switching valve 3 and the check valve 4,
Circuit 1 connecting each cylinder 1, 2 and operation switching valve 3
0 and 11 are connected to each other by a connecting circuit 12, the connecting circuit 12 has a first position 14 provided with a check valve 13 for allowing flow from the circuit 11 to the circuit 10, and a pilot circuit for blocking the flow. Hydraulic circuit arrangement for a tailgate lifter, comprising a hydro-switching valve 17 and a throttle 18 having a second position 16 moved by the pressure of the main circuit 6 acting through the hydraulic circuit 15.