JPH0225019Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of a non-contact type seal related to shaft sealing technology.

[Conventional technology]

Conventionally, as a type of non-contact type seal, a spiral groove is formed in a part of the outer circumferential surface of a rotating shaft, which is a rotating member, and this part is loosely inserted into a shaft hole of a housing, which is a stationary member. A viscous seal type is known that generates a pressure gradient within the fluid by rotating the helical groove relative to the fluid to prevent leakage of the fluid. Fig. 5 shows an example of this type of non-contact seal, in which 1 is a housing of a rotating device, 3 is a non-contact type seal;
is rotatably loosely inserted into the housing 1, and the part corresponding to the small diameter shaft hole 2a of the housing 1 is
It is a rotating shaft formed with a rotating side sealing member 4 in which a spiral groove 5 is formed. a spiral ridge 5' (the outermost peripheral surface of the rotating sealing member 4) corresponding to the spiral groove 5;
A slight gap 6 is formed along the entire circumference between the inner circumferential surface of the small diameter shaft hole 2a of the housing 1, and the fluid that attempts to leak out of the machine from the gap 6 flows through the rotating shaft 3. The leakage of the fluid is suppressed by the pressure gradient (so-called screw pump action) generated within the gap 6 by the rotation of the spiral groove 5 accompanying the rotation and by the viscosity of the fluid itself.

[Problem that the invention attempts to solve]

Leakage from non-contact seals as mentioned above,
Since it is a Poiseuille flow due to the pressure difference through the gap 6, the size of the gap 6 is h, the viscosity of the fluid is μ, and the axial length of the sealed portion (the gap 6) is L.
If the pressure difference between both ends of the sealed part is ΔP, the leakage amount Q
Generally, there is a relationship of Q∝h ³ /μ・LΔP. In this case, the pressure difference ΔP and fluid viscosity μ are given as operating conditions,
Furthermore, since there is a restriction on the length L of the sealing part, it is effective to reduce the size h of the air gap 6 in order to minimize the amount of leakage Q. From the viewpoint of preventing solid contact between the ridge 5') and the inner peripheral surface of the small diameter shaft hole 2a, it is necessary to center them (the rotating side sealing member 4 and the small diameter shaft hole 2a). This poses a problem in that machining and assembly of the peripheral surface become difficult. Therefore, there is a limit to how small the gap 6 can be, and even if it could be made small, precise and sophisticated machining would be required, which would increase costs.

In view of the above problems, the present invention aims to improve sealing performance by reducing the gap in the sealing part, and to provide a non-contact type seal that is easy to process and assemble. The difficulty in centering due to the reduction of h is due to the fact that, as shown in FIG. A body 7 is provided separately from the housing 1, and is floatingly supported in the shaft hole 2b of the housing 1 through an elastic member such as an O-ring 8 made of a rubber material so as to be freely displaceable in the radial direction and in an airtight manner. It is thought that this problem can be solved by configuring the cylindrical body 7 to follow the axial vibration of the rotating shaft 3 (rotating-side sealing member 4). In this case, in the sealing portion (gap 6), the fluid is sealed by the screw pump action of the spiral groove 5, and the bearing action by the viscosity of the fluid is performed to connect the inner circumferential surface of the shaft hole 2b of the housing 1 to the rotating side sealing member. 4 Outer peripheral surface (helical ridge 5')
It is necessary to prevent solid contact. For this purpose, the fluid load capacity of the bearing must be greater than the weight of the fixed cylindrical body 7 supported in a floating manner. However, in the case of a non-contact type seal having a spiral groove 5 in the sealing portion that performs a bearing action, the fluid bearing ability is limited to the outer periphery of the spiral ridge 5' having a narrow width l. That is,
According to the short bearing theory applied to narrow bearings, the load capacity W is W∝μl ³ (μ: fluid viscosity), so the bearing capacity is extremely small, especially when the sealing fluid is water, for example. If the viscosity is low, the bearing capacity becomes even smaller, and there are cases where even the weight of the fixed cylindrical body 7 cannot be supported. Therefore, in order to solve this problem, it is considered necessary to reduce the weight of the fixed cylindrical body 7 as much as possible.

[Means for solving problems]

From the above points of view, the present invention forms a spiral groove in a part of the outer peripheral surface of the rotating side, and uses this part as a rotating side sealing member, and the rotating side sealing member has an annular shape on the inner periphery of the stationary side sealing member. In the non-contact type seal that is loosely inserted so as to leave a small gap and prevents leakage of internal fluid by the screw pump action of the spiral groove, the fixed side sealing member is formed into a thin and lightweight cylindrical shape, Both ends of the fixed side sealing member are floatingly supported in the shaft hole of the device housing through bellows in a radially movable and airtight manner.

[Effect]

According to the above configuration, the cylindrical stationary side sealing member that forms a small gap with the rotating side sealing member is provided separately from the housing, and is airtightly supported in the shaft hole of the housing by the bellows. Due to the flexible deformation of the bellows, it can follow the axial vibration of the rotating side sealing member with excellent response, and since it is thin and lightweight, the load capacity of the sealing fluid (bearing capacity) is small. Also, the following action is performed well, and solid contact between the two sealing members is avoided.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

First, FIG. 1 shows a first embodiment, in which numeral 1 denotes an equipment housing, and numeral 3 denotes a rotating shaft constituting a rotation-side sealing member 4 having a spiral groove 5 formed therein. As shown in FIG. 2, a thin and lightweight cylindrical stationary sealing member 9 is provided between the housings 1 and 1 facing each other in the axial direction, and is arranged coaxially with the shaft holes 2 and 2. Both ends 9' of the fixed side sealing member 9 are connected to the housings 1, 1 through cylindrical bellows 10, 10 with corrugated cross sections made of metal, resin, or rubber.
The rotary side sealing member 4 portion of the rotary shaft 3 is floatingly supported on the shaft hole end faces 1', 1' of the rotary shaft 3, and the rotation side sealing member 4 portion of the rotary shaft 3 has a space between it and the inner circumferential surface of the stationary side sealing member 9. It is loosely inserted into the fixed side sealing member 9 so as to leave a slight gap 6 around the entire circumference. According to this configuration, the stationary side sealing member 9 performs an extremely good follow-up operation to the axial runout of the rotating side sealing member 4 due to the bearing function of the sealing fluid interposed in the gap 6. The size h of
It is now possible to reduce the size from 500 to 1/1000,
Therefore, the sealing performance is dramatically improved.

Next, in the second embodiment shown in FIG. 3, the fixed side sealing member 9 is fixed at the inner diameter part to the end part 9' of the fixed side sealing member 9 and at the outer diameter part to the end surface 1' of the housing 1. Elasticity is applied to the inner periphery of the shaft hole 2 of the housing 1 through corrugated disc-shaped bellows 11, 11, as shown in FIG. It is supported by floating airtightly and airtightly, and in this example,
Since the fixed side sealing member has a thin and lightweight cylindrical shape and is floatingly supported by the housing so as to be freely displaceable in the radial direction, the fixed side sealing member has good followability against shaft runout, as in the first embodiment. , the gap between the rotating side sealing member and the rotating side sealing member can be made extremely small.

[Effect of idea]

As explained above, the non-contact type seal of the present invention has a fixed side sealing member that forms a small gap between the rotary side sealing member and the outer circumference of the rotating side sealing member in which a spiral groove is formed and has a screw pump action. is made into a thin, lightweight cylindrical shape and is supported by the housing via a bellows.The bellows does not maintain airtightness between the housing and the stationary side sealing member by compression, so it can be bent and deformed freely. Therefore, even if the load capacity (bearing capacity) of the sealing fluid interposed in the gap is low, the stationary side sealing member can successfully follow the axial runout of the rotating side sealing member in the radial direction. Therefore, the gap can be made smaller and the sealing performance can be dramatically improved, and both the sealing members can be easily processed, and the centers can be easily aligned during processing and assembly, resulting in low cost. It also contributes to the development of

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing a first embodiment of the non-contact seal according to the present invention, Fig. 2 is a longitudinal cross-sectional view of the same with the rotating shaft removed, and Fig. 3 is a second embodiment. FIG. 4 is a cross-sectional perspective view with the rotating shaft removed, FIG. 5 is a vertical cross-sectional view showing an example of a conventional non-contact seal, and FIG. It is a longitudinal cross-sectional view showing a non-contact type seal when a fixed cylindrical body is provided. DESCRIPTION OF SYMBOLS 1... Housing, 2... Shaft hole, 3... Rotating shaft, 4, 4'... Rotating side sealing member, 5, 5'... Spiral groove, 6... Gap, 8... O-ring, 9... ...Fixed side sealing member, 10, 11...Bellows.

Claims (1)

[Scope of utility model registration request] A spiral groove is formed in a part of the outer peripheral surface of the rotating side to serve as a rotating side sealing member, and the rotating side sealing member is inserted loosely into the inner circumference of the stationary side sealing member so as to leave a small annular gap. In the non-contact seal, the stationary side sealing member is formed into a thin and lightweight cylindrical shape, and both ends of the stationary side sealing member are displaceable in the radial direction through bellows in the shaft hole of the device housing. A non-contact type seal characterized by being airtightly supported by floating.