JPH0233909B2 - RIRIIFUBEN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relief valve that is disposed between a system pressure line and a return line in a fluid circuit and performs constant rate damping in response to a sudden increase in system pressure.

To explain the conventional example of power shovel,
A hydraulic circuit is used to control the start of the swing system.
A large number of relief valves are installed to cope with the sudden increase in oil pressure in the system pressure pipeline, but when conventional relief valves are rapidly operated for relief, the peak pressure exceeding the relief setting pressure transiently increases. This has disadvantages such as poor operating feeling and shortened hydraulic system life.In particular, in the upper rotating structure of a power shovel, when the brake is applied during turning, the backlash of the swing gear is shockingly reversed. , there is a problem that causes a large shock to the driver's seat.

The present invention was developed to eliminate the above-mentioned drawbacks of conventional relief valves, and includes a main valve disposed between a system pressure line and a return line and biased by a spring, and a main valve disposed between a system pressure line and a return line, A relief valve comprising a bleed passage that applies back pressure to the main valve connected to a pressure pipeline, and a pilot valve disposed between the bleed passage and the return pipeline, wherein the bleed passage and An accumulator is provided in the flow path between the pilot valve and the pilot valve through an orifice, and a piston for actuating the pilot valve is provided which is directly connected to the system pressure pipe and receives system pressure and is applied with back pressure from the accumulator. It has a unique feature and its purpose is to provide an accumulator between the bleed passage of the main valve and the pilot valve, and to eliminate the shock by utilizing the time delay until the pressure within the accumulator increases. The object of the present invention is to provide a relief valve that eliminates the above drawbacks.

The present invention has the above-mentioned configuration, and includes a pilot valve connected to a bleed passage and a return passage, which apply back pressure to a spring-biased main valve disposed between a system pressure line and a return line. An accumulator is provided through an orifice in the flow path between the system pressure pipe and a piston operated by the pilot valve that is directly connected to the system pressure line and receives system pressure and is provided with back pressure from the accumulator. When the system pressure in the pressure pipeline increases rapidly, the piston is driven by the system pressure and operates the pilot valve at a point when the system pressure does not become too high.A bleed flow path is created as a result, and the bleed flow passes through the orifice. Due to the inflow into the accumulator, the increase in back pressure of the main valve is significantly delayed, the rate of increase in system pressure becomes gradual, the main valve is smoothly shifted to relief operation, and an excessive increase in system pressure is prevented, resulting in a relief operation. Performance is significantly improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which 1 is a system pressure pipe in a hydraulic circuit, 2 is a return pipe communicating with a tank (not shown), and the system pressure pipe 1 and the return pipe are shown. A valve seat 3 is provided between the passage 2 and the main valve 10 , which is biased by a spring 11 , is seated on the valve seat 3 .
A bleed passage 13 having a main valve 10 is provided.
, a pressure receiving surface 1 receiving the system pressure P ₁ of the system pressure pipe 1
0-1 is provided with a back pressure surface 10-2 to which the bleed flow from the bleed flow path 13 is applied as back pressure,
A pilot poppet 15 biased by a spring 16 and seated on a valve seat 17 is provided on the downstream side of the flow path 14 connected to the bleed flow path 13, and a pilot valve 20 is provided. The spring chamber 10a of the valve 10 is connected to the return pipe 2 by a flow path 18.

Furthermore, in this embodiment, an accumulator 22 is provided in the flow path 14 between the bleed flow path 13 and the pilot valve 20 via an orifice 21, and a piston 30 is installed between the system pressure pipe 1 and the pilot valve 20.
The piston 30 includes a pressure receiving surface 30-1 that receives the system pressure _P1 in the system pressure pipe 1, a back pressure surface 30-2 of the back pressure chamber 31 communicating with the accumulator 22,
and a back pressure surface 30-3 on the back pressure chamber 32 side of the flow path 14.
The inner end is in contact with the pilot poppet 15.

In addition, the pressure receiving area A ₁ of the pressure receiving surface 10-1 on the system pressure pipe line 1 side in the main valve 10 and the back pressure surface 1 on the back pressure chamber side
The relationship between the pressure receiving area A ₂ of 0-2 is as follows: A ₁ = π/4 (D ₀ ² - _{D 1} ² ) A ₂ = π/4 (D ₀ ² - _{D 2} ² ) A ₁ ≒ A ₂ , the system pressure line 1 in the piston 30
The pressure receiving area a ₁ of the pressure receiving surface 30-1 on the side, the pressure receiving area a ₂ of the back pressure surface 30-2 on the back pressure chamber 31 side, and the back pressure chamber 3
The relationship of the pressure receiving area a ₃ of the back pressure surface 30-3 on the second side is a ₁ = π/ ^4d _{1 2} a ₂ = π/4 (d ₁ ² - d ₂ ² ) a ₃ = π/4d ₂ ² a ₁ It is composed of = a ₂ + a ₃ .

Furthermore, to explain the configuration of the embodiment in general, the main valve 10 is biased by a spring 11 from the upper end surface side and seats on the valve seat 3, the system pressure line 1 and the return line 2 are cut off, and the main valve 10 is seated on the valve seat 3. When the valve moves upward and leaves the valve seat 3, the system pressure in the system pressure line 1 becomes a return flow that flows to a tank (not shown) via the return line 2, and the system pressure can be controlled.

The pilot valve 20, which is separated from the main valve 10 via the flow path 14, is biased by the spring 16 so that the pilot poppet 15 is seated on the valve seat 17, and communicates with the back pressure chamber of the main valve 10 and the return pipe 2. Normally, the operating pressures of the pressure-receiving surface 30-1 and the pressure-receiving surfaces 30-2 and 30-3 of the piston 30 are balanced, and the piston 30 is not operated. In addition, the orifice 12 of the bleed channel 13 is connected to the pilot poppet 1.
5 opens away from the valve seat 17, the main valve 1
The hole diameter is set so that the pressure _P2 in the back pressure chamber at 0 is slightly lower than the system pressure _P1 .

The illustrated embodiment of the present invention has the above-mentioned configuration, and to explain the operation and effect, when the system pressure in the system pressure line 1 is below the set value, the main valve 1
0 Pressure on upper and lower pressure receiving surfaces 10-1 and back pressure surfaces 10-2
Since P ₁ and P ₂ and pressure receiving areas A ₁ and A ₂ are equal, the main valve 10 is seated on the valve seat 3 due to the bias of the spring 11,
The flow between the system pressure line 1 and the return line 2 is interrupted.

On the other hand, the piston 3 communicating with the system pressure pipe 1
0 pressure receiving surface 30-1, back pressure surface 30-2, 30-3
The respective pressure receiving areas at are a ₁ = a ₂ + a ₃ , and the receiving pressure and back pressure are also in a balanced state, and the pilot poppet 15 is seated on the valve seat 17 by the bias of the spring 16, and the pilot poppet 15 is seated on the valve seat 17 between the channels 14 and 18. flow is blocked.

When a high pressure higher than the allowable value occurs in the system pressure line 1, the pressure receiving surface 30-1 of the piston 30, which communicates directly with the system pressure line 1, immediately senses the increase in high system pressure, but the back pressure chamber Since there is a time delay before the high pressure flows into the accumulator 22 from the orifices 12, 21 and increases, the pressure acting on the back pressure surface 30-2 of the piston 30 becomes even lower than that on the pressure receiving surface 30-1. As a result, an upward force is generated on the piston 30 and overcomes the spring 16, and the pilot poppet 15 is pushed upward due to the upward force applied by the piston 30, and the pressure _P2 on the back pressure side of the main valve 10 becomes too large. The pilot valve 20 is opened even if the height does not rise.

Due to the opening, a flow is generated in the bleed channel 13 having the orifice 12, and the pressure _P2 gradually increases until it becomes slightly lower than the high pressure _P1 of the system pressure, and this differential pressure acts on the biasing force of the spring 11. The winning main valve 10 is pushed upward to enter a system pressure set value control state in which flow between the system pressure pipe 1 and the return pipe 2 is permitted.

During the operation, when the pressure in the accumulator 22 gradually increases and becomes equal to the pressure _P2 , the upward force of the piston 30 decreases and the pilot valve 2
As the _P2 pressure to maintain the 0 aperture increases,
The relief setting pressure is balanced out at a pressure higher than that at the time of initial opening, and this equilibrium state ultimately becomes the relief setting value.

Therefore, when applying system pressure in steps to activate the relief, in conventional relief valves, the rate of increase in system pressure is high and the peak pressure that exceeds the relief set pressure is transient, as shown in Figure 2. occurs and has an undesirable effect on the circuit system,
In the case of the present invention, as shown in FIG. 3, due to the action of the piston 30, the peak pressure is generated at a point in time when the system pressure in the system pressure line 1 is much lower than the relief set pressure, which is not very high. The subsequent pressure increase rate becomes extremely slow due to the action of the accumulator 22, which is arranged on the downstream side of the bleed passage 13 with orifices 12 and 21 interposed therebetween, and reaches the relief set pressure at a slow speed. For,
The occurrence of a peak pressure exceeding the relief set pressure as in the prior art is prevented, the main valve 10 operates smoothly, and the relief performance is significantly improved.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to these embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

FIG. 1 is a longitudinal mechanical diagram of a relief valve showing an embodiment of the present invention, FIG. 2 is a pressure characteristic diagram of a conventional relief valve, and FIG. 3 is a pressure characteristic diagram of an embodiment of the present invention. 1: System pressure pipe, 2: Return pipe, 10: Main valve,
11, 16: Spring, 12, 21: Orifice, 1
3: Bleed channel, 14, 18: Channel, 15: Pilot poppet, 20: Pilot valve, 22:
Accumulator, 30: Piston.

Claims (1)

[Claims] 1. A spring-biased main valve disposed between the system pressure pipe and the return pipe, a bleed passage that applies back pressure to the main valve connected to the system pressure pipe, and the bleed passage. In the relief valve including a pilot valve disposed between the return pipe, an accumulator is provided in the flow passage between the bleed passage and the pilot valve via an orifice, and the accumulator is directly connected to the system pressure pipe. A relief valve characterized in that a piston operated by the pilot valve is provided which receives system pressure and receives back pressure from the accumulator.