JP2562738B2 - Seal structure - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal structure for fluid pressure equipment such as pneumatic cylinders and hydraulic cylinders, and more particularly, to a substantially constant sliding resistance of the piston regardless of changes in the pressure difference acting on both sides of the piston. The present invention relates to a seal structure that can be kept at.

[0002]

2. Description of the Related Art Conventionally, an O-ring has generally been used as a seal between a piston and a cylinder of a fluid pressure device such as a fluid pressure cylinder, but a Y-type packing is particularly used to reduce sliding resistance. And piston rings are used.

[0003]

The sliding resistance when the Y-type packing is used will be described with reference to FIG. 3. The ring groove formed in the piston b fitted in the cylinder a with a slight gap. The Y-shaped packing d is fitted in c, the high pressure P1 on the right side of the piston b acts on the right side in the ring groove c, and the low pressure P2 on the left side of the piston b acts on the left side in the ring groove c. To work.

Then, the cylinder a of the Y-type packing d
The high pressure P1 acts on the inner circumference of the portion in contact with the cylinder in the direction of pressing the portion against the cylinder a, and the high pressure P1 acts on the outer circumference.
From the low pressure P1 to the low pressure P1
It acts in the direction of pulling away from.

Here, assuming that the area of the portion of the Y-type packing d that contacts the cylinder a is A, the force Fp for pressing the Y-type packing d against the cylinder a is expressed by the following equation. Fp = P1 · A− (P1 + P2) / 2 · A = (P1−P2) / 2 · A Therefore, when the friction coefficient is μ, the sliding resistance F by the Y-type packing d is expressed by the following equation. F = μ ・ Fp = μ ・ (P1-P2) / 2 ・ A

Therefore, the larger the pressure difference P1-P2 between the high pressure side and the low pressure side, the larger the sliding resistance and the lower the operating efficiency of the piston b, which is a problem to be solved by the present invention. It is an issue. This also applies to the piston ring.

[0007]

As a means for solving such a problem, the present invention is directed to a bottom surface of a ring groove in the width direction.
Holding groove formed almost in the center of the
Contact by making elastic contact with the inner circumference of the piston ring
The height acting on the inner circumference of the piston ring at the position
A seal ring that separates the pressure on the pressure side and the pressure on the low pressure side
The piston ring consists of a high pressure side
Pressure that changes almost linearly from low to low pressure
And acts at the contact position of the seal ring as a boundary
The structure is such that the forces in opposite directions cancel each other out .

[0008]

According to the present invention having the above-mentioned structure, the directions of the forces for pressing the piston ring against the cylinder change between plus and minus at the position where the seal ring contacts the piston ring, so they cancel each other out. The absolute value becomes small, and therefore, the sliding resistance of the piston can be kept small even if the pressure difference acting on both sides of the piston is large.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. The piston ring 1 is fitted in a ring groove c formed in a piston b which is fitted in the cylinder a with a slight gap.
Is inserted into the ring groove c on the right side of the piston b
The high pressure P1 on the right side of the piston b acts on the left side in the ring groove c, and the low pressure P2 on the left side of the piston b acts on the left side in the ring groove c, and the piston ring 1 is pressed against the left side of the ring groove c by the left and right differential pressure. .

A narrow holding groove 4 having a narrow width is formed on the bottom surface of the ring groove c, and a seal ring 2 having a circular cross section made of an elastic material is tightly fitted in the groove 4, and a piston ring is formed at a line L. By contacting the inner surface of 1,
The right side and the left side are completely cut off from each other, and the area on the right side of the line L on the inner peripheral surface of the piston ring 1 is A1 and the area on the left side is A2. Between the bottom surface of the ring groove c and the inner peripheral surface of the piston ring 1, springs 3 are mounted on both sides of the seal ring 2 to press the piston ring 1 against the inner peripheral surface of the cylinder a. .

Since the pressure distribution acting between the piston ring 1 and the cylinder a changes linearly from the high pressure P1 to the low pressure P2, the line L that contacts the seal ring 2 is used.
The pressure at the position corresponding to is Ps. Further, since the high pressure P1 acts on the right side of the line L in the ring groove c and the low pressure P2 acts on the left side thereof, the fluid pressure causes
Let F1 be the force that presses the piston ring 1 against the cylinder a on the right side of the line L, and F2 be the force that presses the piston ring 1 on the cylinder a on the left side of the line L.
1 and F2 are respectively expressed by the following equations. F1 = P1 · A1- (P1 + Ps) / 2 · A1 = (P1-Ps) / 2 · A1 F2 = P2 · A2- (Ps + P2) / 2 · A2 = (P2-Ps) / 2 · A2 Incidentally, P s Is expressed by the following equation. Ps = (P1-P2) * A2 / (A1 + A2) + P2 Therefore, the force with which the piston ring 1 is pressed against the cylinder a by the fluid pressure is expressed by the following equation. F1 + F2 = (P1-P2) * (A1-A2) / 2

The piston ring 1 is further provided with springs 3 and 3.
Since the elastic force Fs of 1 acts, the force F for pressing the piston ring 1 against the cylinder a is expressed by the following equation. F = F1 + F2 + Fs Here, when the friction coefficient between the cylinder a and the piston ring 1 is μ, the sliding resistance T of the piston b is expressed by the following equation. T = μ · F = μ · {(P1-P2) · (A1-A2) / 2 + Fs}

Therefore, when the line L is located at the center of the piston ring 1 in the width direction, that is, when A1 = A2, T = μFs, which is irrespective of the pressure difference acting on both sides of the piston b. The magnitude of the dynamic resistance is constant.

Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, even if A1 = A2 is not satisfied, if A1≈A2, then T≈μ · Fs, and the sliding resistance of the piston b can be suppressed to a small value.

[0015] The present embodiment, the width of the holding groove 4 is wide, the seal ring 2 is different from the first embodiment in that can move within the retaining groove 4. That is, when the right side of the piston b has decreased to the high pressure, coercive as the seal ring 2 is indicated by the solid line in FIG.
Go to the left end of the lifting groove 4, shall apply so is moved to the right end of the holding groove 4 as shown by the chain line in FIG. If the left side of the piston b has decreased to the high pressure, the moving range of the seal ring 2 is holding groove 4
Is regulated within the range of.

Therefore, A1 and A2 of the first embodiment are
Is regulated within a certain range, and it is possible to suppress an increase in sliding resistance of the piston b due to a pressure difference acting on both sides of the piston b.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

a: cylinder b: piston c: ring groove 1: piston ring 2: seal ring 3: spring 4: holding groove

Claims (2)

(57) [Claims] 1. A fitted piston rings into the ring groove formed on the outer periphery of the piston, in the sealing structure so as to seal between the cylinder and the piston in elastic contact with the piston rings on the inner periphery of the sheet Linda Retaining formed at the center of the bottom of the ring groove in the width direction
The groove and the retaining groove are fitted into the groove and make elastic contact with the inner circumference of the piston ring.
The piston ring with the contact position as a boundary.
The pressure on the high pressure side acting on the inner circumference of the
A seal ring that disconnects the piston ring.
The pressure on the pressure side is affected by a linearly changing pressure.
The reverse of the contact point of the seal ring
A seal structure having rigidity such that directional forces cancel each other out . 2. Between the ring groove and the piston ring
If the piston ring is elastically contacted with the inner circumference of the cylinder,
3. The system according to claim 1, further comprising a resilient mechanism.
Structure.