JPH1030496A - Sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote sealing characteristics between a piston rod and a sealing member by providing a resilient portion and a cushoning portion between piston member and projected portion. SOLUTION: In a cylinder 3, a seal member accomodating groove 6 is formed. In this seal member accomodating groove 6, a packing 8 made of nitrile rubber, etc., for instance, is stored. In the packing 8, a packing recessed portion 8a, internal circumferential packing 8b and an outer circumferential packing 8c are formed. In a rod 2, a piston support portion 12 as projected part is provided. In the piston support portion 12, a piston 4 is provided as the piston member, through a spring 16 as the resilient portion, and a damper 14 as the cushioning portion. This piston support portion 12 and the piston 4 are stored in a piston receiving part 10 provided in the cylinder 3. Further, a clearance 18 is provided between the rod 2 and the cylinder 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing device, and more particularly to a sealing device used in a Stirling engine and capable of changing a sealing pressure.

[0002]

2. Description of the Related Art In recent years, a Stirling engine with extremely high thermal efficiency and low pollution such as exhaust gas and noise has attracted attention. As an example of such a Stirling engine, 2
There is a piston type. In this type, a heater, a regenerator, and a cooler are interposed between the expansion cylinder and the compression cylinder,
A working gas filled space is formed. The working gas filled space is filled with a working gas such as helium or hydrogen. The expansion piston and the compression piston provided in the expansion cylinder and the compression cylinder are connected to a crankshaft provided in a crank chamber via a piston rod and a connecting rod, respectively. The rotational movement of the crankshaft is converted into reciprocating movement of the expansion piston and the compression piston, and the working gas moves through the regenerator. At this time,
One is heated by the heat exchange action of the regenerator to become a heater, and the other is cooled to become a cooler.

In order to prevent the performance of the engine, such as heat exchange efficiency, from deteriorating, the Stirling engine is provided with a seal device for preventing lubricating oil in the crank chamber from entering the working gas filled space. I have.

FIG. 11 shows an example of a sectional structure of a cylinder section including a sealing device. Referring to FIG. 11, a piston 52 is provided in an expansion or compression cylinder 51.
The piston 52 includes a piston rod 53 and a crosshead 5.
4 and the connecting rod 55 are connected. The connecting rod 55 is connected to a crankshaft (not shown) installed in the crank chamber. At the upper end of a guide cylinder 56 for guiding the crosshead 54, a sealing device 57 surrounding the entire circumference of the piston rod 53 is provided. The seal device 57 has an annular groove 57a. This annular groove 57a
Is provided with a lip seal type sealing member 57b.

[0005] Inside the guide cylinder 56, lubricating oil (oil mist) exists due to rotation of the crankshaft in the crank chamber. When the piston rod 53 reciprocates, particularly when moving upward from below, oil mist adhering to the piston rod 53 is introduced into the cylinder 51 in the guide cylinder 56.
It is prevented by the sealing device 57 from entering the inside.

[0006]

However, the sealing device constructed as described above has the following problems. First, referring to FIG. 11, when piston rod 53 moves upward from below, as described above, oil mist adhering to piston rod 53 tightens sealing member 57b and piston rod 53 (see FIG. 11). (Seal pressure) prevents entry into the cylinder 51.

On the other hand, in the cylinder 51, there is essentially no oil mist, and no oil mist adheres to the piston rod 53. Therefore, when the piston rod 53 moves from top to bottom, it is not necessary to increase the sealing pressure between the seal member 57b and the piston rod 53 as much as when the piston rod 53 moves from bottom to top. However, the sealing member 57b is always tightened with the same strength regardless of the direction of movement of the piston rod 53. For this reason, the seal member 57b may deteriorate with the movement time of the piston rod 53, and the sealing performance between the seal member 57b and the piston rod 53 may deteriorate. As a result, there is a problem that the performance of the Stirling engine is reduced due to the oil mist penetrating into the cylinder.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a sealing device capable of improving the sealing performance between a piston rod and a sealing member and extending the life of the sealing member. is there.

[0009]

According to a first aspect of the present invention, there is provided a sealing device comprising a cylinder and a rod reciprocating in the cylinder, wherein impurities are transferred from one side to the other side of the cylinder with the rod interposed therebetween. It is a sealing device for preventing intrusion. The sealing device includes a concave receiving portion, a sealing member housing groove, a passage portion, a sealing member, a convex portion, and a piston member. The concave receiving portion is provided on the inner peripheral surface of the cylinder. The seal member storage groove is provided in an annular shape along the inner peripheral surface of the cylinder. The passage is
The concave receiving portion and the seal member storage groove are connected. The seal member is mounted in the seal member storage groove, has a concave portion on one end surface in the length direction of the rod over the entire circumference, and has a portion near the one end of the inner peripheral surface in contact with the rod outer peripheral surface, and the outer peripheral surface. The vicinity of one end of the contacting portion is in contact with the inner peripheral surface of the seal member storage groove. The convex portion is provided on the outer peripheral surface of the rod, protrudes toward the concave receiving portion provided on the inner peripheral surface of the cylinder, and reciprocates with the rod in the concave receiving portion. The piston member is located between the other end surface of the concave receiving portion and the convex portion. Between the piston member and the convex portion, an elastic portion for applying an elastic force between the piston member and the convex portion, and a buffer for applying a buffering force to a relative movement between the piston member and the convex portion. Part intervenes.

According to the above configuration, when there is no phase difference between the reciprocating motion of the piston member and the reciprocating motion of the convex portion, that is, at the position where the rod is completely raised, the piston member and the concave receiving portion surround the piston member. When the pressure in the variable pressure space is the lowest at the position where the rod is fully lowered, or when there is a phase difference, the rod is concave. The pressure in the variable pressure space is reduced during the movement from the receiving portion toward the direction of the seal member storage groove (going step), and during the movement of the rod from the seal member storage groove toward the concave receiving portion (return step). The phase difference can be set so as to exclude the case where the pressure in the variable pressure space is increased. In other words, in the step where the rod goes, the pressure in the variable pressure space is increased,
The pressurized gas flows into the concave portion of the seal member via the passage portion, the pressure in the concave portion increases, and the pressure in the variable pressure space is reduced in the return process of the rod so that the pressure in the concave portion decreases. The phase difference can be set.

Accordingly, in the going step, the sealing pressure between the vicinity of one end of the inner peripheral surface of the seal member and the outer peripheral surface of the cylinder, the vicinity of one end of the outer peripheral surface of the seal member, and the inner peripheral surface of the seal member receiving groove. The sealing pressure with the surface is increased.
Therefore, it is possible to prevent the oil mist adhering to one side of the rod from entering the other side. Conversely, in the return step, the seal pressure between the vicinity of one end of the inner peripheral surface of the seal member and the outer peripheral surface of the cylinder and the seal pressure between the outer peripheral surface of the seal member and the inner peripheral surface of the seal member storage groove are reduced. Therefore, deformation of the seal member due to friction between the seal member and the rod can be prevented, and the life of the seal member can be extended.

Preferably, the phase difference between the reciprocating motion of the piston member and the reciprocating motion of the rod is substantially 90 °.

In such a case, the pressure in the recess will be highest while the rod is moving fastest in the going process. On the other hand, while the rod moves fastest in the return step, the pressure of the gas in the recess becomes lowest. That is, it is possible to most effectively enhance or weaken the sealing property of the sealing member in accordance with the reciprocating motion of the rod. Therefore, the sealing performance of the sealing device can be further improved, and the life of the sealing member can be extended.

Preferably, the elastic portion includes a piston convex portion provided on the piston member, a piston convex portion receiving portion for receiving the piston convex portion provided on the convex portion, a piston convex portion and the piston. An elastic body for connecting the convex portion receiving portion; and the buffer portion includes a piston convex portion and a piston convex portion receiving portion.

In this case, the elastic body and the gas spring made of gas filled in the concave receiving portion during the reciprocating motion in the piston convex portion receiving portion of the piston convex portion constitute an elastic portion, and the piston convex receiving portion is formed. The viscous resistance of the piston and the piston convex part reciprocating in the piston convex receiving part constitutes a buffer part.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sealing device according to an embodiment of the present invention will be described. First, the principle of the present sealing device will be described using a model of a spring as an elastic portion and a damper as a buffer portion.

FIG. 1 is a model diagram showing a cross section of the present sealing device. Referring to FIG. 1, a seal member housing groove 6 is formed in cylinder 3. The sealing member housing groove 6 houses a packing 8 made of, for example, nitrile rubber. In the packing 8, a packing recess 8a, an inner peripheral side packing 8b, and an outer peripheral side packing 8c are formed. The rod 2 is provided with a piston support portion 12 as a convex portion. A piston 4 as a piston member is provided on the piston support portion 12 via a spring 16 as an elastic portion and a damper 14 as a buffer portion. The piston support part 12 and the piston 4 are housed in a piston receiving part 10 provided in the cylinder 3. An appropriate clearance 18 is provided between the rod 2 and the cylinder 3. The clearance between the rod 2 and the cylinder 3, for example, the piston receiving portion 1
Helium or the like as a working gas is filled in the clearance 0 and the clearance 18.

Next, the operation will be described. Referring to FIG. 2, rod 2 reciprocates in cylinder 3, and with reciprocation, piston 4 also reciprocates in piston receiving portion 10. Therefore, for example, the stationary position is defined as an equilibrium position (origin), the origin of the piston support 12 is O ₁ , and the origin of the piston 4 is O ₂ . The displacements from the origins O ₁ and O ₂ are defined as X ₁ and X ₂ , respectively. Also, piston 4
The pressure of a space (hereinafter referred to as a “variable pressure space”) sandwiched between the piston 4 and the packing 8 is p, the length of the fluctuating pressure space at the equilibrium position of the piston 4 is L, and the cross-sectional area is S.

Next, displacements X ₁ and X ₂ of the rod 2 and the piston 4 accompanying the reciprocating motion are assumed as follows.

[0020]

(Equation 1)

[0021]

(Equation 2)

Here, A ₁ is the displacement amplitude of the piston support, A ₂ is the displacement amplitude of the piston, ω is the angular frequency, and θ is the phase difference between the movement of the piston and the movement of the piston support.

The pressure p in the fluctuating pressure space is calculated according to Boyle Charles' law.

[0024]

(Equation 3)

## EQU1 ## Where R is the gas constant and T is the actuation
The temperature of the gas. Equation (3) shows that A _Two<< As L
Considering the first order after expanding

[0026]

(Equation 4)

## EQU1 ## Next, consider the equation of motion of the piston. Assuming that the spring constant of the spring 16 is k, the damping coefficient of the damper 14 is c, and the mass of the piston is m ₂ , the equation of motion of the piston is expressed by the following equation.

[0028]

(Equation 5)

By substituting equations (1) to (3) into equation (4) and rearranging,

[0030]

(Equation 6)

[0031]

(Equation 7)

[0032]

(Equation 8)

## EQU1 ## The following equation is obtained from the equations (5) and (6).

[0034]

(Equation 9)

Here, the phase difference θ between the movement of the rod and the piston is considered. FIG. 3 shows the position (amplitude) of the rod and the piston having the phase difference θ with respect to time, respectively. Referring to FIG. 3, in the movement R of the rod, RA indicates the return step of the rod, and RB indicates the going step. In RA, as the oil mist adheres to the rod, the oil mist attached to the rod returns from the packing to the piston receiving portion. Conversely, in the RB, as the rod moves, the oil mist attached to the rod rises toward the packing from the piston receiving portion. On the other hand, in the movement P of the piston, PA indicates that the position of the piston is below the equilibrium position, and PB indicates that the position of the piston is above the equilibrium position. Therefore, the pressure in the fluctuating pressure space is relatively low in PA and relatively high in PB.

When considering the sealing performance between the packing and the rod, it is necessary to increase the pressure in the variable pressure space in order to enhance the sealing performance. That is, it is necessary to enhance the sealing performance when the phenomenon of oil mist rising is observed.

The minimum condition for such a phase difference θ is, for example, that the piston position P1 shown in FIG. 3, that is, the position where the piston is fully raised is within the range of RB. That is, 0 <θ <180 °, and at this time, sinθ> 0. In equation (8), sin θ>
To be 0,

[0038]

(Equation 10)

Is as follows. When the equation (9) is arranged, the condition is given by the following equation.

[0040]

[Equation 11]

Under these conditions, the inside of the packing recess 8a is pressurized, and the inner packing 8b and the rod 2 are pressed.
And the sealing property between the outer peripheral surface side packing 8c and the sealing member housing groove 6 is improved.

Further, consider an ideal sealing property between the packing and the rod. In this case, it is not necessary to enhance the sealing property near the position where the rod is completely raised. Conversely, in the vicinity of the position where the rod is completely lowered, it is not necessary to weaken the sealing performance. That is, in these vicinity, it is desirable that the pressure in the variable pressure space is a pressure in an equilibrium state.
Thus, the condition for obtaining ideal sealing properties is that the phase difference between the movement of the rod and the movement of the piston is substantially 90 °. This relationship is shown in FIG.

Referring to FIG. 4, the phase difference between rod motion R and piston motion P is 90 °. Rod motion R
And the movement P of the piston will be described in detail. Referring to FIGS. 4 and 5, when the rod has passed the equilibrium position R1, the piston is at the fully raised position P2. That is, when the rod has the fastest speed in the going process, the pressure in the variable pressure space is the highest, and high sealing performance between the rod and the packing is obtained.

Referring to FIGS. 4 and 6, conversely, when the rod has passed the equilibrium position R4, the piston is at the fully lowered position P3. That is, when the rod has the fastest speed in the return process, the pressure in the fluctuating pressure space becomes the lowest, and the sealing performance between the rod and the packing is weakened.

Referring to FIGS. 4, 7 and 8, the pistons are located at equilibrium positions P4 and P5 at a position R2 where the rod is fully raised and a position R3 where the rod is fully lowered. That is, since the pressure in the fluctuating pressure space is a pressure in an equilibrium state, the sealing performance is not unnecessarily enhanced near the position R3, and the sealing performance is not unnecessarily weakened near the position R4.
Therefore, the movement of the piston effectively acts on the PD to pressurize the working space and at the PC effectively acts to depressurize the working space.

The conditions for obtaining the ideal sealing performance between the packing and the rod described above are as follows by substituting θ = 90 ° in equations (5) and (6).

[0047]

(Equation 12)

The damping coefficient c and the spring constant k are given by the following equation (11).
Is selected such that the rod has a high sealing property in the going process and a weak sealing property in the returning process. This prevents the oil mist adhering to the rod from penetrating to one side, and can easily return even if it does. Further, the friction between the packing and the rod is reduced, and the deformation of the packing can be suppressed. Therefore, the sealing performance of the packing is improved and the life of the packing can be extended.

Next, a configuration of a seal device that can be realized based on the above-described model will be described. FIG. 9 shows an example of a cross-sectional structure of the sealing device. Referring to FIG. 9, piston 4 has a first piston 4a and a second piston 4b. The first piston 4a reciprocates in the piston receiving portion 10. The second piston 4b reciprocates in a second piston groove 12a provided in the piston support portion 12. The piston 4 is supported by a piston support 12 via a piston equilibrium positioning spring 20 for determining an equilibrium position. The piston 4 and the piston support portion 12 are formed over the entire circumference of the rod 2. Since the other configuration is the same as the configuration shown in FIG. 1,
The same members are denoted by the same reference numerals and description thereof will be omitted.

Next, the relationship between the damping coefficient and the spring constant will be described in detail. FIG. 10 is an enlarged view of a portion of a frame A shown in FIG. Referring to FIG. 10, second piston 4b and second piston 4b
The distances between the outer peripheral surface and the inner peripheral surface of the piston groove 12a are ε ₁ and ε ₂ , respectively. The diameter of the inner peripheral surface and the outer peripheral surface of the second piston groove 12a respectively and D _1, D _2. Second
The thickness of the piston 4b is h, and the distance from the lower surface of the second piston 4b at the equilibrium position to the bottom of the second piston groove 12a is L1. The spring constant of the piston balancing the positioning spring 20 and k _m.

Second piston 4b and second piston groove 12
The damping coefficient c due to a is given by the following equation, where the contact areas between the second piston 4b and the inner and outer peripheral surfaces of the second piston groove 12a are S ₁ and S ₂ , respectively.

[0052]

(Equation 13)

Here, μ is the viscosity coefficient of the working gas.
By rearranging equation (12) from S ₁ = πD ₁ h and S ₂ = πD ₂ h, the following equation is obtained.

[0054]

[Equation 14]

When the second piston 4b reciprocates in the second piston groove 12a, a gas spring using a working gas is formed. The spring constant k _g of this gas spring, the cross-sectional area of the second piston S, when the equilibrium pressure when the piston is in the equilibrium position and P ₀ is given by the following equation.

[0056]

(Equation 15)

Here, from S = π (D ₂ ² −D ₁ ² ) / 4

[0058]

(Equation 16)

Is as follows. Further, the second piston 4b is supported in the second piston groove 12a by the piston balance positioning spring 20. Therefore, the second piston 4b
-The spring constant of the piston support 12 system is equal to the spring constant of the spring in which the gas spring and the piston balance positioning spring are connected in parallel. Therefore, the spring constant k is given by the following equation.

[0060]

[Equation 17]

By setting the dimensions of the piston 4, the piston support 12 and the like such that the damping coefficient c obtained from the equation (14) and the spring constant k obtained from the equation (17) satisfy the equation (11). In addition, the sealing property can be enhanced in the going process of the rod, and the sealing property can be weakened in the returning process. As a result, it is possible to obtain a sealing device capable of improving the sealing property of the packing and extending the life of the packing.

In the present embodiment, the case where the second piston and the piston support portion are formed over the entire circumference of the rod has been described. However, similar effects can be obtained even if they are formed on a part of the circumference. be able to.

The second piston and the second piston are used as dampers.
In addition to using the viscous resistance with the piston groove, in addition to this, it is also possible to use an electromagnetic damper using resistance to an electric conductor that moves in a magnetic field, a hydraulic damper using dynamic pressure resistance of fluid such as a dashpot, etc. Well, similar effects can be obtained.

Further, although the present sealing device has been described as applied to a Stirling engine, the present invention can also be applied to a device such as a hydraulic device which requires sealing properties of lubricating oil.

The embodiment disclosed this time is merely an example, and it is intended that various embodiments can be taken within the equivalent scope of the invention described in the claims.

[0066]

According to the sealing device of the first aspect of the present invention, when there is no phase difference between the reciprocating motion of the piston member and the reciprocating motion of the convex portion, that is, at a position where the rod is fully raised, In the case where the pressure in the pressure space is the highest, and conversely, at the position where the rod is fully lowered, the pressure in the variable pressure space becomes the lowest, or even when there is a phase difference, Decompressed,
The phase difference can be set so as to exclude the case where the pressure in the variable pressure space is increased in the return step. That is, the pressure of the fluctuating pressure space is pressurized in the going process of the rod, the pressurized gas flows into the recess of the seal member via the passage portion, the pressure of the recess increases, and the rod returns in the returning process. The phase difference can be set such that the pressure in the variable pressure space is reduced and the pressure in the concave portion is reduced.

Accordingly, in the going step, the sealing pressure between the vicinity of one end of the inner peripheral surface of the seal member and the outer peripheral surface of the cylinder and the vicinity of the one end of the outer peripheral surface of the seal member and the inner peripheral surface of the seal member housing groove. The sealing pressure with the surface is increased.
Therefore, it is possible to prevent the oil mist adhering to one side of the rod from entering the other side. Conversely, in the return step, the seal pressure between the vicinity of one end of the inner peripheral surface of the seal member and the outer peripheral surface of the cylinder and the seal pressure between the outer peripheral surface of the seal member and the inner peripheral surface of the seal member storage groove are reduced. Therefore, deformation of the seal member due to friction between the seal member and the rod can be prevented, and the life of the seal member can be extended.

Preferably, the phase difference between the reciprocating motion of the piston member and the reciprocating motion of the rod is substantially 90 °.

In such a case, the pressure in the recess is highest while the rod is moving fastest in the going process. On the other hand, while the rod moves fastest in the return step, the pressure of the gas in the recess becomes lowest. That is, it is possible to most effectively enhance or weaken the sealing property of the sealing member in accordance with the reciprocating motion of the rod. Therefore, the sealing performance of the sealing device can be further improved, and the life of the sealing member can be extended.

Preferably, the elastic part is a piston convex part provided on the piston member, a piston convex part receiving part for receiving the piston convex part provided on the convex part, a piston convex part and the piston convex part. An elastic body for connecting the convex portion receiving portion; and the buffer portion includes a piston convex portion and a piston convex portion receiving portion.

In this case, the elastic body and the gas spring filled with gas in the concave receiving portion during the reciprocating motion in the piston convex receiving portion of the piston convex portion constitute an elastic portion, and the piston convex receiving portion is formed. The viscous resistance of the piston and the piston convex part reciprocating in the piston convex receiving part constitutes a buffer part.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a model of a sealing device according to an embodiment of the present invention.

FIG. 2 is a first sectional view for explaining the operation of the device.

FIG. 3 is a first diagram for explaining movement of a rod and a piston of the device.

FIG. 4 is a second diagram for explaining movement of a rod and a piston of the device.

FIG. 5 is a second cross-sectional view for explaining the operation of the same device.

FIG. 6 is a third sectional view for explaining the operation of the device.

FIG. 7 is a fourth sectional view for explaining the operation of the device.

FIG. 8 is a fifth sectional view for explaining the operation of the device.

FIG. 9 is a cross-sectional view illustrating an example of the sealing device according to the embodiment of the present invention.

FIG. 10 is an enlarged view of the inside of a frame A shown in FIG. 9;

FIG. 11 is a sectional view showing an example of a conventional sealing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Seal device 2 Rod 3 Cylinder 4 Piston 6 Seal member accommodation groove 8 Packing 10 Piston receiving part 12 Piston support part 14 Damper 16 Spring 18 Clearance 20 Piston equilibrium positioning spring

Claims (3)

[Claims] 1. A sealing device for preventing an impurity from intruding from one side to the other side of a cylinder and a rod reciprocating in the cylinder with the rod interposed between the cylinder and the cylinder. A concave receiving portion provided on the inner peripheral surface of the cylinder, a seal member storage groove provided annularly along the inner peripheral surface of the cylinder, a passage portion connecting the concave receiving portion and the seal member storing groove, The rod is mounted in the seal member storage groove, and has a concave portion on one end surface in the length direction of the rod over the entire circumference, and the vicinity of the one end of the inner peripheral surface is in contact with the rod outer peripheral surface, and the outer peripheral surface is A seal member in which the vicinity of the one end is in contact with the inner peripheral surface of the seal member storage groove; and a protrusion provided on the outer peripheral surface of the rod, protruding toward the concave receiving portion provided on the inner peripheral surface of the cylinder, and In A convex portion that reciprocates with the rod, and a piston member located between the other end surface of the concave receiving portion and the convex portion. An elastic portion that applies an elastic force between the piston member and the convex portion, and a buffer portion that applies a buffering force to a relative movement between the piston member and the convex portion. The sealing device. 2. The seal device according to claim 1, wherein a phase difference between the reciprocating motion of the piston member and the reciprocating motion of the rod is substantially 90 °. 3. The elastic portion includes a piston convex portion provided on the piston member, a piston convex portion receiving portion for receiving the piston convex portion provided on the convex portion,
The elastic body which connects the piston convex part and the piston convex part receiving part, The buffer part contains the piston convex part and the piston convex part receiving part. 3. The sealing device according to claim 1.