JP2593490B2 - Relief valve - Google Patents

Description

The present invention relates to a relief valve used in a hydraulic circuit or the like.

(Prior art) When the pressure in a hydraulic circuit rises and exceeds a set value, a part of the oil in the circuit is released to a tank (from a bypass) to control the pressure in the circuit to a set value or less. Usually, a relief valve is used.

FIG. 2 shows a basic structure of the relief valve. A valve seat 109 and a valve body 111 are connected to a port 107 which communicates an inlet 101 from a hydraulic circuit to be controlled and a return 103 to an oil tank. The port 107 is normally closed by the spring pressure of the coil spring 113 as shown in the figure. The spring pressure of the coil spring is adjusted according to the set pressure of the hydraulic circuit.
Is adjusted by moving back and forth.

Then, when the pressure in the hydraulic circuit rises and reaches a set value, the hydraulic pressure goes against the spring pressure of the coil spring 113 and the valve body 111
And open the hydraulic fluid in the circuit from port 107 to return port 103
The coil spring closes the valve element 111 again when the oil pressure in the circuit drops below the set value. This is repeated every time the oil pressure changes.

By the way, although the principle is as described above, if this is put to practical use as it is, the valve will vibrate when the valve closes,
A so-called chattering phenomenon that generates a sound by hitting a valve seat tends to occur. This is especially true if the pressure in the circuit is in or near the cracking pressure relative to the set point. Therefore, in order to avoid this, practically, the valve
In many cases, one having a buffer function as shown in the figure is used.

In FIG. 3, the valve seat 109 is formed in a substantially conical shape having a right columnar head 121 at the tip thereof, and a port 107 is provided at the axis of the valve seat 107 so as to pass to the side in front of the head. is there. On the other hand, the valve element 111 has a substantially cylindrical shape having a blind hole in the axial center, and its tip is in contact with the conical surface to close the port 107.
21 fit to form a buffer oil chamber 123. The gap α between the inner diameter of the blind hole and the outer diameter of the head functions as a throttle during buffering, and is set to an appropriate value for that.
The size of the gap α may be uniform throughout the circumference or partially changed.

In this method, when the valve closes, the oil filling the oil chamber 123 gradually flows out through the gap α, and as the valve closes, the vibration of the valve body 111 is suppressed, thereby preventing chattering from occurring. It is.

(Problems to be Solved by the Invention) In the case of the system shown in FIG. 3, the oil passage to the buffer oil chamber 123 is limited to the gap α between the blind hole of the valve body and the head of the valve seat in both directions. Used. Therefore, for example, when the viscosity of the oil increases in winter or the like, if the gap is small, it takes time to fill the oil chamber 123 at the time of opening the valve, and the rapid opening of the valve is hindered according to an increase in the hydraulic pressure in the circuit. There is. On the other hand, if the gap is increased to speed up the inflow of oil as a countermeasure, the oil in the oil chamber 123 escapes rapidly when the valve is closed, causing a significant decrease in the buffer function.

The present invention has been made in view of such circumstances, and has as its object to provide a relief valve having a buffer function that operates stably without being affected by the viscosity of oil and that has a simple structure.

(Means for Solving the Problems) The present invention is based on a conventional type relief valve shown in FIG. When the valve is opened, the oil quickly fills the oil chamber mainly through the new passage, but when the valve is closed, the oil flows out and out gradually from the gap α as before. The main point is that

(Embodiment) FIG. 1 is a cross-sectional view showing an embodiment of the present invention. An injection port 2 connected to a hydraulic circuit (not shown) is provided at one end of a cylindrical relief valve body 1, and a side view thereof is shown in FIG. A return port 3 is provided for connection to an external oil tank, and both are internally connected.

Inside the valve body 1, a valve seat 6, a valve body 8 and a coil spring 7 for pressing the valve body against the valve seat are built in, and the ends are closed by a spring pressure adjusting screw 17.

The valve seat 6 is formed in a substantially conical shape having a right circular column-shaped head 9 at the tip thereof, and from a passage 11 communicating with an inflow port of its axis,
It has a port 4 that exits to the side just before the head.

On the other hand, the valve element 8 has a substantially cylindrical shape having a blind hole in the axial center, the tip of which normally contacts the conical surface of the valve seat to close the port 4, and the head 9 of the valve seat fits into the blind hole. Thus, a buffer oil chamber 13 is formed. The gap α between the inner diameter of the blind hole and the outer diameter of the head functions as a throttle for gradually discharging the oil in the oil chamber 13 when the valve closes, and is set to a size suitable for it. I have.

The spring pressure of the coil spring 7 is adjusted by moving the adjusting screw 17 forward and backward by the driver groove 19 according to the set pressure of the hydraulic circuit.

The mechanism up to this point is the same as that of the above-described conventional product (see FIG. 3), and therefore, its operation is not different from the conventional case.

The difference in configuration according to the present invention is that a passage 5 dedicated to inflow that passes from the passage 11 to the buffer oil chamber 13 is provided in the head 9 of the valve seat,
The outlet is provided with a check valve 14 for preventing backflow from the buffer oil chamber 13 to the passage 5. This check valve comprises a ball 15 and a coil spring 16, and is adjusted to open when the pressure on the passage 5 side exceeds the set pressure of the hydraulic circuit.

Next, the operation of the relief valve will be described. When the hydraulic pressure of the hydraulic circuit rises from the state shown in FIG. 1 and exceeds the set pressure, the pressure acts on the valve element 8 and the check valve 14 and the oil flows. At the same time, the oil chamber 13 is quickly filled through the passage 5 opened from the inlet 2 and at the same time, the oil pressure pushes the valve 8 against the coil spring 7.

As a result, the port 4 and the return port 3 communicate with each other, part of the oil escapes to the tank, and the hydraulic pressure in the circuit decreases. When the pressure becomes equal to or lower than the set pressure, the check valve 14 returns to close the passage 5, and the oil in the oil chamber 13 gradually flows out from the gap (restriction) α as the coil spring 7 pushes back the valve element 8, so that the valve element 8 synchronizes with this and returns smoothly without chattering.

(Effects of the Invention) As described above in detail, in the relief valve of the present invention, the oil passage to the buffer oil chamber in the conventional relief valve is only the gap (throttle) α in and out. In contrast, by providing a passage dedicated to inflow into the oil chamber separately from the gap α, even when the viscosity of the oil is high, it is possible to respond quickly when the pressure of the hydraulic circuit increases, and the applicable range of the relief valve Has expanded.

Further, the gap α can be set to an appropriate value dedicated to the aperture function, and the buffer effect can be further enhanced. As described above, although the difference in configuration based on the present invention is apparently small, the effect obtained by practical use of the present invention is great.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a relief valve according to the present invention, FIG. 2 is a diagram illustrating the principle of the relief valve,
FIG. 3 is a drawing showing a conventional relief valve. 1,105 Relief valve body 2,101 Inlet 3,103 Inlet 4,107 Ports 5 and 11 Passage 6,109 Valve seat 7,113 Coil spring 8,111 Valve body 9,121 Head of valve seat 13,123 … Buffer oil chamber 14 …… Reverse valve

Claims (1)

(57) [Claims] A valve body having an inlet (2) and a return port (3) has a valve seat (6), a valve body (8) and a coil spring (7) for pressing the valve body against the valve seat (6). The valve seat (6) has a substantially conical shape with a straight cylindrical head (9) at the tip and a passage (11) communicating with the inflow port at the axis thereof. The valve (8) is provided with a port (4), and the valve body (8) has a substantially cylindrical shape with a blind hole in the axial center, and the head (9) of the valve seat fits in the blind hole to form a buffer oil chamber (13). In the relief valve in which the gap between the inner diameter of the blind hole and the outer diameter of the head (9) forms a throttle (α) for buffering, the head (9) of the valve seat is buffered from the passage (11). A relief valve characterized in that a passage (5) dedicated to inflow to the oil chamber (13) and a check valve (14) at the outlet are provided.