JP3749651B2 - Gas bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates generally to gas bearings, particularly gas bearing throttle valves, for example used in free piston Stirling machines.
[0002]
[Prior art]
Free piston Stirling cycle machine gas bearings require restrictors upstream of the compression pad area.
Conventionally, a gas bearing throttle valve is equipped in many means. For example, a capillary, a screw member, and a part having a gap formed by a precision passage.
[0003]
[Problems to be solved by the invention]
All of these prior arts have either a cost problem or a problem of susceptibility to blockage. A desirable throttle valve is required to be as follows. That is, low cost, stability of temperature and creep, that is, the stability of the phenomenon that metal generally found at high temperature increases its strain over time under a constant load, affected by clogging. It is difficult.
[0004]
The present invention provides all these advantages and it has been found that a porous plastic strip supported by a backing ring is an inexpensive and effective squeezing device. The degree of squeezing is controlled by the diameter of the exhaust hole relative to the compression pad, the porosity of the plastic strip and the degree of compression of the backing ring.
[0005]
Furthermore, it has the additional advantage of providing a filter for particles that can damage or wear the surface of the bearing operating in a narrow gap . The throttling performance was found to be comparable to a precision throttling valve consisting of a 60 mm glass capillary with a length of 5 mm.
[0006]
[Means for Solving the Problems]
The gas bearing according to claim 1 is characterized in that a piston sleeve inserted in a cylinder, a gap between the cylinder and the piston sleeve, and an inner space of the piston sleeve penetrate into the gap . A plurality of exhaust holes that are open, a porous strip member that covers the opening in which the exhaust holes open into the inner space, and the porous strip member is pressed in the thickness direction to open the inner space A backing spring that is in close contact with the opening, and the backing spring seals the pressing surface of the porous strip member and passes through the thickness portion of the porous strip member to form the exhaust hole. There is a place where gas is allowed to flow.
[0007]
According to a second aspect of the present invention , a gas bearing recess is formed on the outer periphery of the piston sleeve, and the exhaust hole is open at the bottom of the recess .
[0008]
Further, the invention according to claim 3 is characterized in that the inner space of the piston sleeve is sealed by a piston cap provided at an opening end in the axial direction, and a gas inlet is provided in the piston cap. A lead check valve is attached to the opening on the inner space side of the inlet, and the lead check valve has a gas pressure outside the piston sleeve that fluctuates due to the movement of the piston sleeve. The gas is injected into the inner space only when the pressure in the inner space is higher .
[0009]
Thus, the present invention uses a porous strip member, for example, a porous plastic member, to cover the upstream side of the exhaust hole, and this porous strip member is supported by a backing spring or ring. The diameter of the exhaust hole, the porosity, width and thickness of the strip and the degree of compression by the backing spring control this restriction. The downstream side of the exhaust hole is directly connected to a recess for a gas bearing connected to the hole.
[0010]
The space upstream of the gas bearing throttle valve is a high pressure zone (charge volume). The space is pressurized to maximum pressure in the cycle by using a small reed check valve. The high-pressure fluid is exhausted through the throttle valve, through the exhaust hole, and through the recess for the gas bearing into the gap between the cylinder and the piston sleeve . By arranging the throttle valve so as to have a throttle similar to the gap between the cylinder and the piston sleeve , a value close to the maximum gas bearing rigidity can be obtained.
[0011]
When the parts move eccentrically with the gas bearing, the recess for the gas bearing to which the throttle is applied tends to increase in pressure, and the recess for the gas bearing on the opposite side is exhausted because the degree to which the throttle is applied is less, The pressure drops. This separates the piston sleeve from the cylinder wall and forms a gas film for lubrication. The use of a porous strip as a throttle valve has the advantage of being multipass, and thus is much less likely to become clogged by loose particles. A further advantage is that the gas bearing throttle valve acts as its own filter to prevent small particles from entering the cylinder and piston sleeve gap normally found in machines using gas bearings.
[0012]
The porous gas bearing throttle valve material is easily fitted into the piston sleeve by providing a backing spring or compression ring that presses the porous strip material against the exhaust holes of the gas bearing. Installation can be done by automated machines and seems to be advantageous for mass production.
[0013]
Material and labor costs are very low compared to past technologies. Reliability is much higher because it is less likely to occlude and prevents particles from entering the gap. This gas bearing throttle valve means appears to be particularly suitable for implementation in a Stirling cycle machine.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2, a piston sleeve ( hereinafter referred to as “ piston ” ) 1 is inserted into a cylinder 2 which is closed and attached, and FIG. 1 shows four gas bearings. Specifically, as shown in FIGS. 1 and 3, four gas bearing recesses 11 are formed on the outer periphery of the piston 1 at an equal angular interval of 90 degrees, as shown in FIGS. 1 and 3. An exhaust hole 12 is formed in the inside (bottom) of each concave portion in a state of penetrating the piston in the radial direction. As shown in FIG. 2, there is another set with a predetermined distance from the recesses 11 for the gas bearings, which are another recess 11 and an exhaust hole having substantially the same configuration as the recess and the exhaust hole 12. 12 are formed in the same circumferential direction.
[0015]
A gas bearing gap V is formed between the outer peripheral surface of the piston 1 and the inner wall surface of the cylinder 2, and this gap is the difference between the diameter of the outer periphery of the piston and the diameter of the inner wall surface of the cylinder, This difference is in the range of about 15 to 35 microns, but when the eccentricity of the piston 1 is zero, that is, at the dead point, this half is 7.5 to 17.5 microns.
[0016]
A band-shaped member 3 such as a porous plastic is installed on the inner wall of the piston 1 so as to cover the inner end opening of the exhaust hole 12, and this porous band-shaped member is suitable for sufficient gas bearing rigidity. It constitutes a diaphragm device and has sufficient width, thickness and stability to have this rigidity. Further, the porous belt-like member 3 acts as a filter for particles entering the gap V between the piston 1 and the cylinder 2.
[0017]
The porous strip member 3 is held at a predetermined position by a ring-shaped backing plate spring 4, and the backing plate spring 4 applies a squeezing force to the strip member 3. And the porous strip | belt-shaped member 3 has many gas flow paths, and reduces the possibility that the porous strip | belt-shaped member 3 will be obstruct | occluded. The backing leaf spring 4 includes a pressure compression ring. In addition, as shown in FIG. 1, knobs 4a and 4a are integrally formed at the end of the backing leaf spring 4, that is, at both ends of the joint when the leaf spring is deformed into a cylindrical shape, Therefore, it is easy to install the leaf spring.
[0018]
The opening end (the left end in FIG. 2) of the piston 1 is sealed with a piston cap 5, and the reed valve 6 is attached to the inner end opening of the inlet 51 of this cap. The gas is injected only when the pressure of the gas is higher than the pressure in the piston. The ideal maximum pressure in the piston 1 is the peak pressure applied to the piston cap 5, and this pressure fluctuation is usually caused by the movement of the piston. In order to prevent the lead disk of the reed valve 6 from being contaminated, a check valve filter may be provided at the inlet 51 of the piston cap 5.
[0019]
The other purpose of the backing leaf spring (compression ring) 4 is mainly from the thin thickness part of the porous belt-like material 3, that is, mainly from both end faces of this belt-like member as indicated by arrows in FIG. To make it flow through. This gives a further restriction to a given porous strip material.
[0020]
The operation of the gas bearing will be described with reference to FIG. Incidentally, FIG. 4 for ease of description, illustrated extremely wide empty gap V between the piston 1 and the cylinder 2 is shown to facilitate movement of the piston to understand. When the piston 1 approaches the cylinder 2 at some radial position (upper side in FIG. 4), the gas bearing recess 11 tends to close on the side closest to the cylinder 2 and the piston 1 Tends to open on the side farthest from the cylinder 2 (opposite side). The closed gas bearing recess 11 cannot be evacuated due to the restriction produced by the piston 1 and the cylinder 2 and is therefore pressurized by the gas flowing through the porous strip 3 which is a throttle valve. It will be. Since the recess 11 for the gas bearing on the opposite side is not closed, it tends to exhaust and release the pressure. This differential pressure generates a force that resists the piston movement toward the cylinder 2, thereby preventing the piston 1 from coming into contact with the cylinder 2, and this piston is controlled to float in the center of the cylinder. For optimum rigidity of the gas bearing (defined as the restoring force per unit radial displacement), the designed throttle of the porous strip 3 of the throttle valve is a leak caused by the recess 11 for the gas bearing. It should be almost the same as the aperture. The dimensions of the recess 11 for the gas bearing are selected so as to maintain stability against radial movement of the piston 1 in the cylinder 2. That is, when the piston 1 is displaced in the radial direction, the piston performs a restoring motion so as not to cause radial vibration that will eventually cause the piston to collide with the cylinder 2.
[0021]
The purpose of the reed valve 6 is to ensure that the gas only when the pressure of the gas is higher than the pressure in between the charge air is placed between the charge air piston 1. The ideal maximum pressure in between the charge air is the peak pressure applied to the piston cap 5. This pressure fluctuation is usually caused by the movement of the piston 1.
[0022]
【The invention's effect】
According to the present invention, since the porous belt-like member is held by the backing spring, assembly is facilitated, which is effective in reducing the manufacturing cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view at a position of a gas bearing.
FIG. 2 is a sectional view taken along line aa in FIG.
FIG. 3 is a perspective view of a piston sleeve.
FIG. 4 is a cross-sectional view for explaining the movement of a piston sleeve in a cylinder.
[Explanation of symbols]
1 piston ( piston sleeve )
11 Gas bearing recess 12 Exhaust hole 2 Cylinder 3 Porous strip member 4 Backing leaf spring ( backing spring )
V Gap between piston sleeve and cylinder

Claims (3)

A piston sleeve inserted in the cylinder;
A gap between the cylinder and the piston sleeve;
A plurality of exhaust holes penetrating from the inner space of the piston sleeve and opening into the gap ;
A porous belt-like member covering the opening where the exhaust hole opens into the inner space ;
A backing spring that presses the porous strip-shaped member in the thickness direction thereof and closely contacts an opening that opens into the inner space ;
The backing spring, the porous seals the pressing surface of the belt-shaped member, the gas bearing, characterized in that as the gas flows to the exhaust hole through the thickness portion of the porous strip . In claim 1, the outer periphery of the piston sleeve, Ri recess forming Citea for gas bearings, the gas bearing is the exhaust hole in the bottom of the recess, characterized in that open. In any one of Claim 1 or 2, the inner space of the said piston sleeve is sealed with the piston cap provided in the opening end part of the axial direction,
A gas inlet is formed through the piston cap,
A lead check valve is attached to the opening on the inner space side of the inlet,
The reed check valve injects gas into the inner space only when the gas pressure outside the piston sleeve, which fluctuates due to the movement of the piston sleeve, is higher than the pressure in the inner space. bearing.

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