JPH06213343A - Relief valve - Google Patents

Abstract

PURPOSE:To prevent the relief pressure from rising steeply even though the pilot pressure oil to be supplied to a pressure receiving chamber rises steeply to a certain level from zero. CONSTITUTION:A rellief valve is equipped with a valve 30, which opens and closes the high pressure side 26 to the low 27 via a small hole 24a provided in a main valve 24, and a piston 35 which holds the valve 30 in the closed position using a spring 31 and pushes the valve 30 to the close side with the pilot pressure oil in a pressure receiving chamber 36. With a cancel spring 37, the piston 35 is pushed in the direction of going apart from the valve 30, and the force of pushing the piston 35 is canceled by a cancel spring 37 with the pilot pressure oil in the pressure receiving chamber 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relief valve used in a hydraulic circuit that supplies pressure oil to an actuator of a construction machine or the like.

[0002]

2. Description of the Related Art As a relief valve used in a hydraulic circuit, for example, the one shown in FIG. 1 is known. That is, the main valve 3 that opens and closes the high pressure side 1 and the low pressure side 2 is held in the closed position by the main spring 4, and the poppet 7 that opens and closes the port 6 that communicates with the high pressure side 1 through the pore 5 of the main valve 3 is provided. A relief valve that holds the poppet 7 in a closed position with a spring 8 and changes the mounting load of the spring 8 by sliding a piston 9 that serves as a spring receiver of the spring 8 with pressure oil in a pressure receiving chamber 10 is provided. Are known.

With this relief valve, when the pressure on the high-pressure side 1 exceeds the set pressure, the poppet 7 opens and the high-pressure side 1 opens.
Pressure oil flows from the ports 6 and 11 to the low pressure side 2, the main valve 3 is opened, and the pressure oil on the high pressure side 1 flows out to the low pressure side 2. Further, when the pressure of pilot pressure oil supplied from the pilot valve into the pressure receiving chamber 10 is changed to change the mounting load of the spring 8, the force pressing the poppet 7 is different and the set pressure can be made variable.

[0004]

With such a relief valve, when the pressure of the pilot pressure oil supplied into the pressure receiving chamber 10 is continuously increased as shown in FIG. The set pressure (relief pressure) gradually increases from P ₁ to P ₂ in proportion to
As shown in (b) of FIG. 7, when the pressure is rapidly increased from zero to Pis in a stepwise manner, the relief pressure is also rapidly increased from P ₁ to Ps.

That is, (P _S -P ₁ ) is (pis × π /
It is approximately equal to 4 × D ² ₀ ) ÷ (π / 4 × d ² ). However, D ₀ is the diameter of the piston 9, and d is the seat diameter of the poppet 7. As described above, when the relief pressure suddenly rises from the low pressure relief, the main valve 3 causes chattering and a pressure shock is transmitted to the hydraulic circuit, which causes a problem in use.

Therefore, an object of the present invention is to provide a relief valve capable of solving the above-mentioned problems.

[0007]

[Means for Solving the Problems] High-pressure side 26 and low-pressure side 27
A main valve 24 that opens and closes the main valve 24, a main spring 25 that holds the main valve 24 in a closed position, a valve 30 that opens and closes the high-pressure side 26 and the low-pressure side 27 via the pores 24a of the main valve 24, and this valve 30. 31 for holding the valve 30 in the closed position, a piston 35 for pushing the valve 30 to the closing side by the pressure in the pressure receiving chamber 36, and a piston 35 for pushing the piston 35 in the valve 3
A relief valve consisting of a cancel spring 37 that pushes away from zero.

[0008]

[Operation] If the pressure of the pressure oil supplied into the pressure receiving chamber 36 does not rise to a value commensurate with the mounting load of the cancel spring 37, the relief pressure becomes a low pressure set pressure, and if the pressure rises above that value, the relief pressure becomes the pressure. As the pressure supplied to the pressure receiving chamber 36 rapidly rises from zero to a certain value, the relief pressure does not suddenly become high, and the main valve 24 may cause chattering. Absent.

[0009]

[Example] As shown in FIG. 3, a main relief valve 24 for opening and closing an inlet port 22 and an outlet port 23 is fitted in one side hole 21 of the valve body 20, and the main relief valve 24 is a main spring. It is held in the closed position at 25, its inlet port 22 opening to the high-pressure side 26 and its outlet port 23 opening to the low-pressure side 27. The valve body 20 is formed with an intermediate hole 28 communicating with the high pressure side 26 through the small hole 24a of the main valve 24. The intermediate hole 28 is formed with a port 29 opening to the low pressure side 27. Is fitted with a valve 30 that opens and closes the port 29.
Is held in the closed position by a spring 31. A sleeve 33 is inserted and fixed in the other side hole 32 of the valve body 20, and the piston 3 having a pushing rod 34 is attached to the sleeve 33.
5 is inserted to form a pressure receiving chamber 36, and the piston 35
Is pushed to the pressure receiving chamber 36 side by the cancel spring 37,
The push rod 34 protrudes from the sleeve 33 and faces the valve 30 at a distance from each other, and the spring 31 causes the valve 3 to move.
It is provided between 0 and the retainer 40.

[0010] mounting load f ₀ of the cancel spring 37 are substantially equal to the _{^{π / 4 × D 2 0 ×}} Pis. The mounting load f ₀ can be adjusted by loosening the lock nut 38 and tightening and loosening the cylindrical piston support 39 with respect to the sleeve 33. Here, D ₀ is the diameter of the piston 35, and Pis is the pressure of the pilot pressure oil when the pressure rapidly increases from zero.

Next, the operation will be described. When the pressure of the pilot pressure oil in the pressure receiving chamber 36 sequentially increases from zero to Pis, as shown in FIG. 4A, the low pressure set pressure P corresponding to the mounting load of the spring 31 is increased until the pressure increases to Pis. ₁ and the pilot pressure oil pressure is Pi
When s or more, the piston 35 is pushed by the pressure in the pressure receiving chamber 36 against the cancel spring 37 toward the valve 30 side and compresses the spring 31 via the retainer 40, so that the pressure gradually increases in proportion to the pressure. .

When the pressure of the pilot pressure oil in the pressure receiving chamber 36 suddenly rises from zero to Pis, the relief pressure remains the low pressure set pressure P ₁ as shown in FIG. 4B, and thereafter. When the pressure rises, the relief pressure sequentially rises to the high pressure set pressure P ₂ . In this way, by providing the cancel spring 37, the relief pressure does not rise sharply even if the pressure of the pilot pressure oil rises sharply from zero.

Further, the pressure of the pilot pressure oil that does not increase the relief pressure can be made variable by changing the mounting load of the cancel spring 37, and the cancel spring 37 having a different spring constant can be selected as shown in FIG. The relationship between the relief pressure and the pressure of the pilot pressure oil can be changed within the range indicated by the hatched line in b).

[0014]

The relief pressure becomes a low pressure set pressure unless the pressure of the pressure oil supplied into the pressure receiving chamber 36 rises to a value commensurate with the mounting load of the cancel spring 37, and if the pressure rises above that value, the relief pressure changes. The pressure gradually increases in proportion to the pressure. Therefore, even if the pressure supplied to the pressure receiving chamber 36 rises rapidly from zero to a certain value, the relief pressure does not suddenly become high, and the main valve 24 does not chatter.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional relief valve.

FIG. 2 is a chart showing the relationship between pilot pressure oil pressure and relief pressure.

FIG. 3 is a sectional view of a relief valve showing an embodiment of the present invention.

FIG. 4 is a chart showing the relationship between the pressure of pilot pressure oil and the relief pressure.

[Explanation of symbols]

24 ... Main valve, 25 ... Main valve, 26 ... High pressure side, 27
... low pressure side, 30 ... valve, 31 ... spring, 35 ... piston, 36 ... pressure receiving chamber, 37 ... cancel spring,
39 ... Piston support.

Claims (2)

[Claims] 1. A main valve 24 that opens and closes a high pressure side 26 and a low pressure side 27, a main spring 25 that holds the main valve 24 in a closed position, and a pore of the main valve 24 that connects the high pressure side 26 and the low pressure side 27. A valve 30 which opens and closes via 24a, a spring 31 which holds the valve 30 in a closed position,
A relief valve including a piston 35 that pushes the valve 30 toward the closing side by the pressure in the pressure receiving chamber 36 and a cancel spring 37 that pushes the piston 35 in a direction away from the valve 30. 2. The cancel spring 3 for the piston 35.
The relief valve according to claim 1, further comprising a piston support body (39) which is pushed against the valve body (7) so as to be adjustable in and out.