JP2561717Y2 - Two-way relief valve - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a relief valve provided in a closed circuit for driving a hydraulic motor for construction machines and industrial machines.

[0002]

2. Description of the Related Art A drive circuit of a hydraulic motor used for construction machines and industrial machines is, for example, a hydraulic motor 2 shown in FIG.
Is connected to a variable displacement dual discharge hydraulic pump 1 via a valve device 3.

[0003] The valve device 3 comprises a two-way relief valve comprising two valve units 4 and 5, a flushing valve 6 and a low-pressure relief valve 7, which are the body of the hydraulic motor 2 as shown in FIG. 8 inside.

The valve units 4 and 5 are provided facing ports A and B which communicate with the hydraulic pump 1, respectively.

[0005] A passage 14 is formed in the body 8 to communicate these ports A and B. The valve unit 4 has a poppet 9 seated on a seat 15 formed at the opening of the passage 14 facing the port A, and an inside of the poppet 9 communicating with the port A through orifices 10 and 11 formed on the wall surface of the poppet 9. The vehicle includes a damper chamber 12, a pilot valve 13 responsive to the pressure in the damper chamber 12, and a spring 16 for urging the poppet 9 toward the seat 15.

The valve unit 5 is similarly constructed, and includes a poppet 18 seated on a seat 17 formed at an opening opposite to the passage 14 facing the port B, and orifices 19 and 2.
0, a damper chamber 21, a pilot valve (not shown) and a spring 22.

The pressure in the port A acts on the damper chamber 12 through the orifices 10 and 11, and when this pressure rises above the set relief pressure, the pilot valve 13 is pushed open to release a part of the hydraulic oil in the damper chamber 12. It flows out to drain 23.

As a result, the pressure difference between the port A and the damper chamber 12 becomes large, and the poppet 9 is displaced rightward in FIG.
Connect to 4.

As a result, the pressure in the passage 14 also increases, the poppet 18 is pushed open by the increased pressure, and the hydraulic oil in the port A flows out to the port B. As a result, when the pressure of the port A decreases and the pilot valve 13 closes, the spring 1
The poppet 9 urged to 6 is seated again on the seat 15 to block outflow of the hydraulic oil from the port A.

When the pressure at the port B rises above the set relief pressure, the poppet 18 operates in the same manner, causing the hydraulic oil at the port B to flow out to the port A to lower the pressure at the port B.

In this manner, both ports A and B are maintained at a pressure lower than the set relief pressure.

[0012]

When the hydraulic oil flows from the port A to the port B, the hydraulic oil in the damper chamber 21 which contracts when the poppet 18 opens due to the high pressure in the passage 14 is filled with the orifice 19.
However, if the pressure of the port A rises rapidly, the hydraulic oil in the damper chamber 21 does not flow out to the port B in time, and the poppet 9 opens and the poppet 18 opens. There will be a time delay.

In the meantime, the passage 14 having the same pressure as the port A
Is applied to the poppet 9, the poppet 9 is further displaced in the opening direction, and the damper chamber 12 is further contracted.

However, since the supply of the hydraulic oil from the port A to the damper chamber 12 is performed through the orifices 10 and 11, even if the pressure of the port A decreases due to the outflow of the hydraulic oil to the port B, the hydraulic oil greatly contracts. The damper chamber 12 cannot be expanded suddenly, and the hydraulic oil continues to flow from the port A to the port B until the poppet 9 closes.

For this reason, in this two-way type relief valve, when the pressure at the port A or the port B rises sharply, the pressure is reduced to a point that is significantly lower than the set relief pressure by the relief operation, and the pressure becomes stable. Tend to take time.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the responsiveness of a two-way relief valve to prevent an unnecessary pressure drop.

[0017]

According to the present invention, a damper chamber communicating with a port around a poppet is formed in the poppet through an orifice formed in a wall surface of the poppet, and the damper chamber is formed in accordance with the pressure of the damper chamber. Valve units having a pilot valve for allowing hydraulic oil to flow to the drain are provided at both ends of the passage communicating between the ports, and the poppets of these valve units respond to the pressure balance between the passage and the port and the damper chamber. In a two-way relief valve that is seated on a seat in a passage opening,
The axial dimension of the poppet is set to a length such that the tip of one poppet abuts the tip of the poppet seated on the opposite seat just before the seating position.

[0018]

The poppet is held open at the low-pressure port by the interference between the tips of the poppet. For this reason, the pressure of the high pressure port rises above the set relief pressure and the valve unit of the high pressure port opens, and at the same time, the hydraulic oil of the high pressure port quickly flows out to the low pressure port to lower the pressure of the high pressure port. In other words, there is no time difference between the opening movement of the poppet on the high-pressure port side and the outflow of hydraulic oil from the high-pressure port to the low-pressure port, so that the poppet on the high-pressure port side is not excessively displaced and the pressure drops to the set relief pressure. The high pressure port side poppet closes quickly.

[0019]

FIG. 1 shows an embodiment of the present invention. The same components as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.

This figure shows the structure of a two-way relief valve provided between ports A and B of a hydraulic motor similar to the prior art.

As shown in the figure, each of the valve units 4 and 5
The tip portions 9A and 18A of the poppets 9 and 18 are formed longer than those of the conventional example. For example, in a state where the poppet 9 is seated on the seat 15, the tip 18 </ b> A is set to the tip 9 </ b> A just before the poppet 18 is seated on the seat 17.
Is set to abut. That is, the distance between the seating portion of the poppet 9 on the seat 15 and the seating portion of the poppet 18 on the seat 17 is set to be always larger than the distance between the seats 15 and 17.

As a result, at least one of the poppets 9 and 18 is separated from the sheet 15 (17), and the passage 14 is always in communication with at least one of the ports A and B.

The other structure is the same as that of the conventional example.

Next, when the port A for explaining the operation is at a high pressure and the port B is at a low pressure, the poppet 9 is seated on the seat 15 due to the difference between these pressures. It is separated from the sheet 17.

When the pressure of the port A rises above the set relief pressure in this state, the pilot valve 13 opens due to the rising pressure of the damper chamber 12 inside the poppet 9 communicating through the orifices 10 and 11, and the pilot valve 13 opens. The hydraulic oil flows out to the drain 23.

As a result, the pressure in the damper chamber 12 decreases, the pressure balance acting on the poppet 9 is broken, and the poppet 9 is displaced rightward in the figure against the spring 16.

As a result, the port A communicates with the passage 14,
The hydraulic oil in port A flows out to port B through the gap between passage 14 and poppet 18. The tip 9A is separated from the tip 18A with the displacement of the poppet 9, but at this time, the operating oil pressure to flow out of the port A acts on the poppet 18, so that the poppet 18 remains open.
The hydraulic oil in the port A immediately flows out of the passage 14 to the passage B.

For this reason, the poppet 9 does not open excessively, and when the pressure of the port A decreases to the set relief due to the outflow of the hydraulic oil and the pilot valve 13 closes, the poppet 9 immediately sits on the seat 15.

Therefore, the pressure at the port A does not drop below the set relief pressure, and the port A always maintains a stable pressure.

When the port B is on the high pressure side, the poppet 18 is seated on the seat 17 and the poppet 9 is separated from the seat 15. In this case as well, the poppet 18 opens and closes responsively in response to the pressure change of the port B, and the poppet 9 does not prevent the hydraulic oil from flowing out of the port B, so that the pressure of the port B is stably maintained.

[0031]

[Effect of the Invention] As described above, in the present invention, the valve unit of the low pressure port is kept open by contacting the tips of the poppet with each other. It opens and closes responsively to the change, immediately releases the excessive pressure of the high pressure port to the low pressure side port, and stops the pressure release as soon as the pressure drops to the relief pressure.

Therefore, there is no possibility that the relief operation causes an excessive pressure drop, and the pressure control accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a two-way relief valve according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a hydraulic drive device showing a conventional example.

FIG. 3 is a longitudinal sectional view of the two-way relief valve.

[Explanation of symbols]

 4,5 Valve unit 9,18 Poppet 9A, 18A Tip 10,11,19,20 Orifice 12,21 Damper chamber 13 Pilot valve 14 Passage 15,17 Seat 23 Drain A, B port

Claims (1)

(57) [Scope of request for utility model registration] 1. A pilot for forming a damper chamber communicating with a port around a poppet through an orifice formed on a wall surface of the poppet inside the poppet, and for allowing hydraulic oil in the damper chamber to flow to a drain according to a pressure of the damper chamber. Valve units provided with valves are provided at both ends of the passage communicating between the ports, and the poppets of these valve units are seated on the seat of the passage opening in response to the pressure balance between the passage and the port and the damper chamber. In the bidirectional relief valve configured as above, the axial dimension of the poppet is set to a length in which the tip of one poppet abuts on the tip of the poppet seated on the opposite seat just before the seating position. Type relief valve.