JPS5819885B2 - Fluid pressure cylinder with flow control valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluid pressure cylinder with a flow control valve that automatically adjusts the moving speed of a piston sliding in contact within the cylinder.

Fluid pressure cylinders are widely used in various work equipment and other devices operated by fluid pressure.In these fluid pressure cylinders, the moving speed of the piston sliding in the cylinder is If there is a sudden large fluctuation, or if the piston approaches the end wall of the cylinder at a rapid speed and collides violently with the end wall of the cylinder, the fluid pressure cylinder or parts of the equipment in which the fluid pressure cylinder is incorporated may be damaged. , or their useful life may be shortened, resulting in various inconveniences.

Conventionally, for example, as shown in FIG. 1, when the piston 2 sliding in the cylinder 1 approaches the end wall of the cylinder 1, the valve rod 3 attached to the piston 2 touches the end wall of the cylinder 1. Penetrating the formed orifice 6,
A shock absorber was provided which slowed down the movement of the piston 2 by restricting the flow rate of the fluid passing through the supply and discharge passage 5 formed in the supply and discharge passage forming body 4 by constricting the orifice 6 .

Generally, the size of the opening area of the orifice in the device provided for controlling the flow rate is designed so that an optimal buffering function can be obtained when the maximum load Vhax among the loads acting on the fluid pressure cylinder is applied. It is being done.

Therefore, as shown by curve a in FIG. 2, the smaller the load W acting on the hydraulic cylinder, the smaller the flow rate of fluid through an orifice of the type mentioned, and the time T spent on damping becomes smaller. This results in drawbacks such as a very long time required for the cylinder retraction stroke.

On the other hand, if the load acting on the piston is too large,
Another drawback is that the piston is accelerated during its movement, and a large surge pressure is generated during buffering, giving a large impact to various parts of the device.

Therefore, as shown in the ideal curve in FIG. 2, the present invention has been developed so that the time T spent for buffering the movement of the piston is always the optimal length, regardless of the magnitude of the load W acting on the hydraulic cylinder. The main objective is to obtain a fluid pressure cylinder with a flow rate control valve that can be maintained at

The fluid stool cylinder with a flow control valve of the present invention includes a piston structure that extends along the axis in the cylinder so as to form a cylinder chamber between the end wall of the cylinder, and a piston structure that extends along the axis in the cylinder. a valve rod that is fitted into a synovial hole formed in the cylinder so as to allow synovial fluid to flow therein, is always subjected to an elastic pressing force on the end wall side of the cylinder, and has a distal end protruding from the piston structure in the axial direction; a valve cylinder that is attached to an end wall of the cylinder and forms a first communication port that opens to the cylinder chamber side and a second communication port that communicates with the fluid supply and discharge path side; along the axial direction while receiving an elastic pressing force on the piston structure side, and the first
When the piston component approaches the end wall of the cylinder, it forms an orifice which is closed by the tip of the valve rod, and which is closed by the distal end of the valve rod when the piston component approaches the end wall of the cylinder. a hollow coastal valve body that variably controls the opening area of the second flow port; the valve rod is bored in the valve rod and has a flow cross section smaller than the orifice; The cylinder chamber is characterized in that it includes at least a communication hole that communicates the cylinder chamber and the orifice when the cylinder chamber is closed.

An embodiment of the present invention will be described below with reference to the drawings. First, in FIG. The synovial fluid is inserted freely in the axial direction.

An abutment hole 9 is formed in the axial center of the piston component 8 in the axial direction, and a proximal end 11 of the valve rod 10 is inserted into the abutment hole 9.
is inserted in the axial direction so that the synovial fluid can freely flow.

The base end 11 has a larger diameter than the central part of the valve rod 10, and is configured so that it cannot be pulled out from inside the welt hole 9. It projects in the axial direction from within the structure 8 toward the end wall of the cylinder 7 .

A spring chamber B is provided between the bottom wall of the access hole 9 and the base end surface of the valve rod 10.
is formed, and by the action of a pressing spring 12 housed in this spring chamber B, the valve rod 10 is always elastically pressed toward the tip side.

A communication hole 13 is formed in the piston component 8 to communicate the annular chamber between the base end 11 of the valve rod 10 and the end wall of the opening end of the contact hole 9 with the cylinder chamber A. When I'm there,
A communication hole 14 is formed in the valve rod 10 to communicate the cylinder chamber A and the spring chamber B.
4 allows the valve stem 10 to move axially relative to the piston arrangement 8 without locking action due to fluid pressure.

A communication hole 16 is further formed in the valve rod 10, and the communication hole 16 is open on one side at the side surface of the valve rod 10 and at the center of the distal end surface 15 of the valve rod 10 on the other side. ing.

Incidentally, an opening 19 is formed in the center of the end wall of the cylinder 7, and a valve casing 17 is provided with a mounting bolt 18 on the outer surface of the end wall of the cylinder 7 so as to surround this opening 19. It is fixed by a fixing means.

The valve casing 17 has a fluid supply/discharge path 21 on its side surface, and an annular chamber is formed inside the valve casing 17 with the inner wall 20 of the valve casing 17.
A flow port 23 is formed along the inner periphery of the valve cylinder 22, and a valve cylinder 22 having one or more flow ports 24 is supported on the side wall.

Inside the valve cylinder 22, there is an orifice 26 on the flow port 23 side.
If it has, the flow port 24 will be opened along the axial direction.
A hollow coastal valve body 25 having an edge 29 that controls the opening degree of the
is inserted in the axial direction so that the synovial fluid can freely flow.

In the valve cylinder 22, a spring chamber C is formed between the valve body 25 and the valve seat 27 attached to the bottom of the valve cylinder 22, and a pressure spring 28 is housed in the spring chamber C. As a result, the marginal valve body 25 is always elastically pressed toward the flow port 23 side.

The orifice 26 is on the same center line as the valve rod 10, and the cross-sectional area of the orifice 26 is smaller than the area of the tip surface 150 of the valve rod 10, so that when the tip of the valve rod 10 comes into contact with the creeping valve body 25, The orifice 26 is closed by the distal end surface 15 of the valve rod 10, and the cylinder chamber A and the spring chamber C are communicated only through the communication hole 16.

With the structure described above, in FIG. 3, the piston structure 8 is
When a load is applied to the cylinder 7, the piston structure 8
Move towards the end wall.

At this time, the fluid in the cylinder chamber A is discharged to the supply/discharge passage 21 through the communication port 23, the orifice 26, the communication port 24, and the annular chamber.

At this time, the flow port 24 is normally at its maximum opening, but
When an excessive load is applied to the piston component 8, the pressure of the fluid flowing from the cylinder chamber A toward the spring chamber C causes the adjacent valve body 2 to
5 moves in a direction opposite to the pressing force of the pressing spring 28, and the end edge 29 reduces the opening degree of the flow port 24.

As a result, the flow rate of fluid passing through the flow port 24 is restricted, thereby braking the piston structure 8 and preventing a dangerous situation.

The piston component 8 further moves toward the end wall of the cylinder 7, and the end surface 15 of the valve body 10 is brought into contact with the orifice 2 as shown in FIG.
6, the valve body 10 receives a force in the direction opposite to the pressing force of the pressing spring 12 and elastically contracts toward the inside of the piston structure 8. 28
The end edge 29 moves in the direction opposite to the pressing force of
This reduces the opening degree of the flow port 24.

In this way, the piston structure 8 can gradually receive a larger braking force and come to a gentle stop.

When moving the piston structure 8 in a direction away from the end wall of the cylinder 7, the supply and discharge passage 2 is moved in the state shown in FIG.
When fluid is supplied from 1, the fluid flows through the annular chamber D and the flow port 24.
, flows into the cylinder chamber A through the spring chamber C1 communication hole 16, and presses the piston structure 8 in the axial direction.

At this time, when the inflow speed of the fluid is relatively high, a pressure gradient is generated in the flow direction, which causes the distal end surface 15 of the valve rod 10 to
A pressing force also acts on the valve rod 10, and the valve rod 10 retreats at a faster speed than the piston structure 8 against the pressing force of the pressing spring 12, and leaves the orifice 26.

Thus, as shown in FIG. 3, the valve rod 10 is completely separated from the orifice 26, and the marginal valve body 25 is pressed by the pressure spring 28 and moves toward the flow port 23, and accordingly, The opening degree of the flow port 24 also increases, and the piston component 8 smoothly moves away from the end of the cylinder 7.

Therefore, when the fluid pressure cylinder with a flow rate control valve of the present invention described above is implemented as a cylinder for tilting a load box provided between the body frame of a dump truck and a load box, for example, the load box can be tilted. When the cylinder is contracted and the cargo box is turned upside down from the state where the cargo box is in a contracted state, the cargo box can be turned down at a constant speed regardless of the magnitude of the load on the cargo box, that is, the magnitude of the load on the cylinder. It can be stopped smoothly and without causing any shock.

As described above, according to the present invention, the valve rod elastically protrudes from the piston component toward the end wall of the cylinder, and the valve rod elastically protrudes toward the piston component within the valve cylinder attached to the end wall of the cylinder. A floating valve body is provided which is pressed by the valve body, and as the creeping valve body moves along the axis in the axial direction, the opening area of the end flow port formed in the valve cylinder and communicating with the fluid supply and discharge passage becomes variable. When configured to be controlled, when the valve rod closes the orifice provided in the valve body, the fluid flows through the communication hole formed in the valve rod, so each Under conditions in which the members cooperate with each other, the piston component moves and stops smoothly, and regardless of the magnitude of the load acting on the hydraulic cylinder, the movement of the piston component is always buffered. Time is kept at an optimal length.

Furthermore, according to the present invention, it is possible to obtain a fluid pressure cylinder with a flow rate control valve that has a simple structure as a whole and has almost no breaks.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of the main part of an example of a conventional fluid pressure cylinder with a flow rate control valve, and Fig. 2 shows the relationship between the load and the required time during buffering of the fluid pressure cylinder in the case of a conventional device. A graph showing a comparison with an ideal case, FIG. 3 is a vertical sectional view of a main part showing a specific example of a fluid pressure cylinder with a flow control valve according to the present invention, and FIG. 4 is a state different from FIG. 3. FIG. 3 is a vertical cross-sectional view of a main part similar to FIG. 3 in FIG. 7... Cylinder, 8... Piston component, 9... Synovial hole, 10... Valve rod, 1
6... Communication hole, 21... Supply/discharge path, 22
...Valve cylinder, 23...First flow port, 24...Second flow port, 25...
Parallel valve body, 26... Orifice, A...
・Cylinder chamber.

Claims (1)

[Claims] 1 A piston structure 8 that slides into axial direction within the cylinder 7 so as to form a cylinder chamber A between the end wall of the cylinder 7, and a contact hole formed in the axial direction in the piston structure 8. a valve rod 10 which is fitted into the cylinder 9 so as to be freely movable therein, is always subjected to an elastic pressing force against the end wall side of the cylinder 7, and whose tip protrudes in the axial direction from inside the piston structure 8; 7, the valve cylinder 22 forms a first communication port 23 opening to the cylinder chamber A side and a second communication port 24 communicating to the fluid supply/discharge path 21 side; Inside the valve cylinder 22, the piston component 8 is always in sliding contact with the piston component 8 in the axial direction while being subjected to an elastic pressing force, and faces the first flow port 23.
comes close to the end wall of the cylinder 7, the valve rod 1
a hollow synovial fluid valve body 25 that forms an orifice 26 that is closed by the tip of the hollow synovial fluid valve body 25 and that variably controls the opening area of the second flow port 24 as the synovial fluid moves in the axial direction; and a communication hole bored in the valve rod 10, having a flow cross section smaller than the orifice 26, and communicating the cylinder chamber A and the orifice 26 when the valve rod 10 closes the orifice 26. A fluid pressure cylinder with a flow control valve, which includes at least a hole 16.