JP4939581B2 - piston ring - Google Patents

Description

  The present invention relates to a piston ring, and more particularly to a piston ring suitable for use in a low-temperature fluid boost pump that compresses and pressurizes a low-temperature fluid.

  Conventionally, as a low-temperature fluid pressurizing pump that compresses and pressurizes a low-temperature fluid (for example, hydrogen, nitrogen, LNG, etc.) at a low temperature (for example, −253 ° C. to −100 ° C.) Is known (see, for example, Non-Patent Document 1).

Endo Takuya et al., “New Energy Vehicle”, Sankai-do, January 1995, p. 221-222

  However, in such a conventional pump for low-temperature fluid, in order to maintain airtightness, the piston ring slides while the outer peripheral surface of the piston ring is pressed against the inner peripheral surface of the cylinder. There is a problem that heat is generated due to friction with the heat and the low-temperature fluid is heated and vaporized by the heat, resulting in a decrease in pump efficiency. In particular, when trying to obtain a high pressure, the high-pressure low-temperature fluid that flows into the inner peripheral surface of the piston ring acts so that the outer peripheral surface of the piston ring is pressed more strongly against the inner peripheral surface of the cylinder. There is a problem that friction between the piston ring and the cylinder becomes intense, and heat generated by the friction is remarkably increased.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a piston ring capable of reducing frictional heat generated when the piston ring slides along the inner wall surface of the cylinder. .

The present invention employs the following means in order to solve the above problems.
The piston ring according to the present invention is a piston ring disposed in a plurality of ring grooves formed on the outer peripheral surface of the piston, and is made of a resin including a material having high thermal conductivity therein, and The high-rate material is arranged so as to be distributed more on the low-pressure side on the radially inner side.
According to such a piston ring, heat generated in the piston ring (that is, frictional heat generated when the piston ring slides along the inner wall surface of the cylinder) is contained in the heat conduction contained in the piston ring. Since it is transmitted to the piston (having a large heat capacity) through the material having a high rate, the temperature rise of the piston ring can be reduced.

The piston ring according to the present invention is a piston ring disposed in a plurality of ring grooves formed on the outer peripheral surface of a piston of a cryogenic fluid booster pump, and is made of a resin containing a material having high thermal conductivity. A recess having a rectangular shape in a cross-sectional view extending to the inner peripheral surface along the circumferential direction is provided on the inner side in the radial direction of one surface on the low-pressure side, and the recess is made of a material having high thermal conductivity. The heat transfer material is closely attached.
According to such a piston ring, heat generated in the piston ring (that is, frictional heat generated when the piston ring slides along the inner wall surface of the cylinder) is contained in the heat conduction contained in the piston ring. Since the heat is transmitted to the piston (having a large heat capacity) via the high-rate material and the heat transfer material, the temperature increase of the piston ring can be reduced.

The pressurizing pump for low-temperature fluid according to the present invention includes any one of the above piston rings.
According to such a booster pump for low-temperature fluid, heat generation of the piston ring and the cylinder (that is, the cylinder block) is suppressed, and thus evaporation (vaporization) of the low-temperature fluid sucked into (flowed into) the cylinder. Can be suppressed, and the pump efficiency can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that the frictional heat which generate | occur | produces when a piston ring slides along the inner wall face of a cylinder can be reduced.

It is a figure which shows 1st reference embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off a part of piston ring. It is a figure which shows 2nd reference embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off a part of piston ring. It is a figure which shows 3rd reference embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off a part of piston ring. It is a figure which shows 4th reference embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off a part of piston ring. It is a figure which shows 5th reference embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off a part of piston ring. It is a figure which shows 1st Embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off some piston rings. It is a figure which shows 2nd Embodiment of the piston ring by this invention, Comprising: It is the perspective view which cut off a part of piston ring. FIG. 5 is a diagram for comparing a cryogenic fluid booster pump according to a reference embodiment of the present invention with a conventional cryogenic fluid booster pump, in which (a) is a graph showing the relationship between the position of a piston ring and leakage resistance; (B) is a graph which shows the relationship between the position of a piston ring, and a pressure. It is a schematic longitudinal cross-sectional view of the booster pump for low temperature fluids provided with the piston ring by this invention.

  Hereinafter, a piston ring (hereinafter referred to as “piston ring”) first reference embodiment of a booster pump for low-temperature fluid according to the present invention will be described with reference to FIGS. 1 and 9. FIG. 1 is a perspective view in which a part of a piston ring according to the present embodiment is cut, and FIG. 9 is a schematic longitudinal sectional view of a cryogenic fluid booster pump having a piston ring according to the present invention.

As shown in FIG. 9, the booster pump 1 for low-temperature fluid is configured with a drive unit (not shown) and a pump unit 2 driven by the drive unit as main elements.
The pump unit 2 includes a piston 3, a piston rod 4, and a cylinder block 5.
The piston 3 is a member having a substantially cylindrical shape that is reciprocally accommodated in a cylinder 6 formed inside the cylinder block 5, for example, made of copper, and has one end surface (the lower end surface in FIG. 9). ) Can compress a low temperature fluid (for example, liquid hydrogen, liquid nitrogen, liquefied carbon dioxide gas, liquefied natural gas, liquefied propane gas, etc.).
A plurality of (three in this embodiment) ring grooves 7 are formed along the circumferential direction on the outer peripheral surface of the piston 3 (that is, the surface facing the inner peripheral surface (cylinder wall) of the cylinder 6). In addition, piston rings 8 are respectively disposed in the ring grooves 7.

The piston rod 4 is a substantially rod-shaped member having a circular shape in cross section, and one end thereof is connected to the central portion of the other end surface of the piston 3, and the other end is connected to a power transmission unit of a drive unit (not shown). It is connected.
The power transmission unit linearly reciprocates the piston rod 4 in the vertical direction with a stroke of, for example, 2 mm by the power from the drive source (see the solid line arrow in FIG. 1).

The cylinder block 5 is a member having an approximately hollow cylindrical cylinder 6 therein. The bottom surface of the cylinder 6 (the lower surface in FIG. 9) is a low-temperature fluid compressed by a fluid inlet 9 into which a low-temperature fluid in an atmospheric pressure flows and one end surface of the piston 3 (pressurized to about 40 MPa). And a fluid outlet 10 from which the fluid flows out. A pipe 11 is connected to each of the fluid inlet 9 and the fluid outlet 10, and a check valve (not shown) is connected to each of the pipes 11 located near the upstream side of the fluid inlet 9 and the downstream side of the fluid outlet 10. Check valves 12 and 13 are provided.
Further, a through hole 14 through which the piston rod 4 passes is provided on the upper surface of the cylinder 6 (the upper surface in FIG. 9), and a seal 15 is provided between the piston rod 4 and the through hole 14. ing.

  With the above-described configuration, in the booster pump 1 for low-temperature fluid, the piston 3 connected to one end of the piston rod 4 is moved into the cylinder 6 by the piston rod 4 that linearly reciprocates in the vertical direction by the power from the drive source. The low-temperature fluid sucked into the cylinder 6 from the fluid inflow port 9 is compressed by one end face of the piston 3 and pressurized (increased) to a desired pressure (for example, about 1.3 MPa). Then, it is led out of the cylinder block 5 from the fluid outlet 10.

Next, the piston ring 8 will be described in more detail with reference to FIG.
The piston ring 8 is made of resin (for example, polytetrafluoroethylene), and a plurality of (three in the present embodiment) circumferential grooves 8a are provided on the outer circumferential surface thereof along the circumferential direction. These circumferential grooves 8a are formed, for example, so as to be carved by a predetermined depth from an intermediate point in the height direction (vertical direction in FIG. 1) of the piston ring 8 to one side (upper side in FIG. 1).
In addition, the code | symbol 8b in FIG. 1 has shown the joint (stepped joint) of the piston ring 8. FIG.

According to the piston ring 8 according to the present embodiment, since a plurality of circumferential grooves 8a are provided on the outer peripheral surface thereof, the contact area between the outer peripheral surface of the piston ring 8 and the inner peripheral surface of the cylinder 6 can be reduced. In addition, the frictional heat generated when the piston ring 8 slides along the inner wall surface of the cylinder 6 can be reduced.
Further, according to the low-temperature fluid booster pump 1 having such a piston ring 8, heat generation of the piston ring 8 and the cylinder 6 (that is, the cylinder block 5) is suppressed. The evaporation (vaporization) of the low-temperature fluid that has been (flowed in) can be suppressed, and the pump efficiency can be improved.
Further, the temperature of the low-temperature fluid is increased between the outer peripheral surface of the piston ring 8 and the inner peripheral surface of the cylinder 6 from the other side (lower side in FIG. 1) to one side (upper side in FIG. 1). Therefore, the heat generation of the piston ring 8 and the cylinder 6 (that is, the cylinder block 5) can be further suppressed, and the evaporation of the low-temperature fluid sucked into (flowed into) the cylinder 6 can be achieved. (Vaporization) can be further suppressed, and the pump efficiency can be further improved.
Furthermore, the low temperature leaks between the outer peripheral surface of the piston ring 8 and the inner peripheral surface of the cylinder 6 from the other side (lower side in FIG. 1) to one side (upper side in FIG. 1). The fluid passes alternately through a narrow portion where the circumferential groove 8a is not provided and a wide portion where the circumferential groove 8a is provided. In a narrow portion where the circumferential groove 8a is not provided, the pressure decreases and the speed increases. In a wide portion where the circumferential groove 8a is provided, a vortex flow occurs and the speed decreases. As a result, the pressure of the low-temperature fluid passing between the outer peripheral surface of the piston ring 8 and the inner peripheral surface of the cylinder 6 is gradually reduced. That is, a labyrinth effect can be obtained.
Furthermore, only by changing the cross-sectional shape, arrangement, number, etc. of the circumferential groove 8a, the other side of the piston ring 8 (the lower side in FIG. 1) is provided between the outer peripheral surface of the piston ring 8 and the inner peripheral surface of the cylinder 6. ) From one side to the other (upper side in FIG. 1) can be easily adjusted.

A second reference embodiment of the piston ring according to the present invention will be described with reference to FIG.
The piston ring 20 in the present embodiment includes a circumferential groove machining portion 21 having a circumferential groove 8a formed on the outer peripheral surface thereof, and a piston ring body that forms a single piston ring 20 by the circumferential groove machining portion 21 being attached. 22 is different from that of the first reference embodiment described above.
In addition, the same code | symbol is attached | subjected to the member same as 1st reference embodiment mentioned above, and description about them is abbreviate | omitted here.

The circumferential groove processing portion 21 is made of metal (excellent in workability), and a plurality of (three in the present embodiment) circumferential grooves 8a are provided on the outer circumferential surface along the circumferential direction. The outer peripheral surface of the peripheral groove processed portion 21 (at least the portion in contact with the inner peripheral surface of the cylinder 6) is coated with a resin (for example, polytetrafluoroethylene) or a metal (for example, molybdenum disulfide). ing.
The piston ring main body 22 is made of a resin (for example, polytetrafluoroethylene), and a peripheral groove processing portion is formed on the peripheral portion from an intermediate point in the height direction of the piston ring 20 to one side (upper side in FIG. 2). A step 22 a for receiving (attaching) 21 is provided.

According to the piston ring 20 according to the present embodiment, the circumferential groove machining portion 21 and the piston ring main body 22 are separate members, and the circumferential groove machining portion 21 is made of a metal that is superior (rich) in workability than resin. Since it is manufactured, the productivity of the piston ring 20 can be improved, and the manufacturing cost can be reduced.
Other functions and effects are the same as those of the first reference embodiment described above, and a description thereof is omitted here.

A third reference embodiment of the piston ring according to the present invention will be described with reference to FIG.
The piston ring 30 in the present embodiment is different from that in the first reference embodiment described above in that a vertical groove 30a is formed instead of the circumferential groove 8a.

The piston ring 30 is made of resin (for example, polytetrafluoroethylene), and a plurality of vertical grooves 30a are provided on the outer peripheral surface thereof along the height direction (vertical direction in FIG. 3). These vertical grooves 30a are formed, for example, so as to be carved by a predetermined depth from an intermediate point in the height direction of the piston ring 30 to one side (upper side in FIG. 3).
In FIG. 3, the joint (stepped joint) of the piston ring 30 is omitted and not shown.

According to the piston ring 30 according to the present embodiment, since the plurality of vertical grooves 30a are provided on the outer peripheral surface, the contact area between the outer peripheral surface of the piston ring 30 and the inner peripheral surface of the cylinder 6 can be reduced. In addition, the frictional heat generated when the piston ring 30 slides along the inner wall surface of the cylinder 6 can be reduced.
Moreover, since these vertical grooves 30a can be processed more easily than the peripheral grooves 8a, the productivity of the piston ring 30 can be further improved, and the manufacturing cost can be further reduced. it can.
Furthermore, according to the low-temperature fluid booster pump 1 having such a piston ring 30, heat generation of the piston ring 30 and the cylinder 6 (that is, the cylinder block 5) is suppressed. The evaporation (vaporization) of the low-temperature fluid that has been (flowed in) can be suppressed, and the pump efficiency can be improved.
Furthermore, between the outer peripheral surface of the piston ring 30 and the inner peripheral surface of the cylinder 6, from the other side of the piston ring 30 (lower side in FIG. 3) to one side (upper side in FIG. 3), (Pole) Since part of it will pass, it is possible to further suppress the heat generation of the piston ring 30 and the cylinder 6 (that is, the cylinder block 5) and to be sucked into (flowed into) the cylinder 6. The evaporation (vaporization) of the low-temperature fluid can be further suppressed, and the pump efficiency can be further improved.
Furthermore, only by changing the cross-sectional shape, arrangement, number, etc. of the longitudinal groove 30a, the other side of the piston ring 30 (the lower side in FIG. 3) is provided between the outer peripheral surface of the piston ring 30 and the inner peripheral surface of the cylinder 6. ) From one side to the other (upper side in FIG. 3) can be easily adjusted.

A fourth reference embodiment of the piston ring according to the present invention will be described with reference to FIG.
The piston ring 40 in the present embodiment is different from that in the third reference embodiment described above in that an oblique groove 40a is formed instead of the longitudinal groove 30a.

The piston ring 40 is made of resin (for example, polytetrafluoroethylene), and a plurality of oblique grooves 40a are provided on the outer peripheral surface thereof along the height direction (vertical direction in FIG. 4). These oblique grooves 40a are formed, for example, so as to be carved by a predetermined depth from an intermediate point in the height direction of the piston ring 40 to one side (upper side in FIG. 4).
In FIG. 4, the joint (stepped joint) of the piston ring 40 is omitted and not shown.

According to the piston ring 40 according to the present embodiment, since a plurality of oblique grooves 40a are provided on the outer peripheral surface thereof, the contact area between the outer peripheral surface of the piston ring 40 and the inner peripheral surface of the cylinder 6 can be reduced. In addition, the frictional heat generated when the piston ring 40 slides along the inner wall surface of the cylinder 6 can be reduced.
Further, since these oblique grooves 40a can be processed more easily than the peripheral grooves 8a, the productivity of the piston ring 40 can be improved, and the manufacturing cost can be reduced.
Furthermore, according to the low-temperature fluid booster pump 1 having such a piston ring 40, heat generation of the piston ring 40 and the cylinder 6 (that is, the cylinder block 5) is suppressed. The evaporation (vaporization) of the low-temperature fluid that has been (flowed in) can be suppressed, and the pump efficiency can be improved.
Furthermore, between the outer peripheral surface of the piston ring 40 and the inner peripheral surface of the cylinder 6, from the other side of the piston ring 40 (lower side in FIG. 4) to one side (upper side in FIG. 4), (Pole) Since part of it will pass, it is possible to further suppress the heat generation of the piston ring 40 and the cylinder 6 (that is, the cylinder block 5) and to be sucked into (flowed into) the cylinder 6. The evaporation (vaporization) of the low-temperature fluid can be further suppressed, and the pump efficiency can be further improved.
Furthermore, an oblique groove 40a is provided between the outer peripheral surface of the piston ring 40 and the inner peripheral surface of the cylinder 6 so as to inhibit the flow of low-temperature fluid that proceeds from the other side of the piston ring 40 toward one side. Therefore, the flow resistance of the low-temperature fluid traveling from the other side of the piston ring 40 toward the one side between the outer peripheral surface of the piston ring 40 and the inner peripheral surface of the cylinder 6 is increased more than that of the longitudinal groove 30a. be able to.
Furthermore, only by changing the cross-sectional shape, arrangement (angle), number, etc. of the oblique groove 40a, the other side of the piston ring 40 (FIG. 4) is provided between the outer peripheral surface of the piston ring 40 and the inner peripheral surface of the cylinder 6. The amount of the cryogenic fluid that passes from the lower side to the one side (the upper side in FIG. 4) can be easily adjusted.

A fifth reference embodiment of the piston ring according to the present invention will be described with reference to FIG.
The piston ring 50 in the present embodiment is different from that in the fourth reference embodiment described above in that an inversion groove 50a is formed instead of the oblique groove 40a.

The piston ring 50 is made of a resin (for example, polytetrafluoroethylene), and a plurality of inversion grooves 50a are provided on the outer peripheral surface along the height direction (vertical direction in FIG. 5). These oblique grooves 50a are carved by a predetermined depth in one direction (from the upper left to the lower right in FIG. 5), for example, from an intermediate point in the height direction of the piston ring 50 to one side (upper in FIG. 5). The piston ring 50 is engraved by a predetermined depth in the other direction (from the lower left to the upper right in FIG. 5) from the intermediate point in the height direction of the piston ring 50 to the other side (lower in FIG. 5). Is formed.
In FIG. 5, the joint (stepped joint) of the piston ring 50 is omitted and not shown.

According to the piston ring 50 according to the present embodiment, since a plurality of inversion grooves 50a are provided on the outer peripheral surface, the contact area between the outer peripheral surface of the piston ring 50 and the inner peripheral surface of the cylinder 6 can be reduced. In addition, the frictional heat generated when the piston ring 50 slides along the inner wall surface of the cylinder 6 can be reduced.
Moreover, since these reversal grooves 50a can be processed more easily than the peripheral groove 8a, the productivity of the piston ring 50 can be improved, and the manufacturing cost can be reduced.
Furthermore, according to the low pressure fluid booster pump 1 having such a piston ring 50, heat generation of the piston ring 50 and the cylinder 6 (that is, the cylinder block 5) is suppressed. The evaporation (vaporization) of the low-temperature fluid that has been (flowed in) can be suppressed, and the pump efficiency can be improved.
Furthermore, between the outer peripheral surface of the piston ring 50 and the inner peripheral surface of the cylinder 6, from the other side of the piston ring 50 (lower side in FIG. 5) to one side (upper side in FIG. 5), (Pole) Since part of it will pass through, the heat generation of the piston ring 50 and the cylinder 6 (that is, the cylinder block 5) can be further suppressed, and is sucked into (flowed into) the cylinder 6. The evaporation (vaporization) of the low-temperature fluid can be further suppressed, and the pump efficiency can be further improved.
Furthermore, an inversion groove 50a is provided between the outer peripheral surface of the piston ring 50 and the inner peripheral surface of the cylinder 6 so as to inhibit the flow of low-temperature fluid traveling from the other side of the piston ring 50 toward one side. Therefore, the flow resistance of the low-temperature fluid traveling from the other side of the piston ring 50 toward the one side between the outer peripheral surface of the piston ring 50 and the inner peripheral surface of the cylinder 6 is increased more than that of the oblique groove 40a. be able to.
Furthermore, only by changing the cross-sectional shape, arrangement (angle), number, etc. of the inversion groove 50a, the other side of the piston ring 50 (FIG. 5) is provided between the outer peripheral surface of the piston ring 50 and the inner peripheral surface of the cylinder 6. The amount of the cryogenic fluid passing from the lower side to the one side (the upper side in FIG. 5) can be easily adjusted.

A piston ring according to a first embodiment of the present invention will be described with reference to FIG.
The piston ring 60 in the present embodiment is different from that in the above-described embodiment in that a material 61 having a high thermal conductivity is included in the piston ring 60.

The piston ring 60 is made of a resin (for example, polytetrafluoroethylene), and has a high thermal conductivity material (for example, powdered copper or the like) as shown by black dots (dots) in FIG. ) 61 is included (impregnated), for example, by about 60 wt%. Further, as shown in FIG. 6, the material 61 having a high thermal conductivity is arranged so as to be distributed more on one surface side in the radial direction (upper side in FIG. 6).
In addition, the code | symbol 62 in FIG. 6 has shown the backup ring.

According to the piston ring 60 according to the present embodiment, heat generated in the piston ring 60 (that is, frictional heat generated when the piston ring 60 slides along the inner wall surface of the cylinder 6) Since it is transmitted to the piston 3 having a large heat capacity through the material 61 having a high thermal conductivity contained therein, an increase in the temperature of the piston ring 60 can be reduced.
Further, according to the booster pump 1 for a low temperature fluid provided with such a piston ring 60, the heat generation of the piston ring 60 is suppressed, so that the evaporation of the low temperature fluid sucked into (flowed into) the cylinder 6 is performed. (Vaporization) can be suppressed, and pump efficiency can be improved.

A second embodiment of the piston ring according to the present invention will be described with reference to FIG.
The piston ring 70 according to the present embodiment replaces the material 61 having a high thermal conductivity contained in the piston ring 70 so that the material 61 is more distributed on the one surface side in the radial direction (the upper side in FIG. 6). It differs from the thing of embodiment mentioned above by the point that 71 is provided.

The piston ring 70 is made of a resin (for example, polytetrafluoroethylene), and inside thereof, as shown by black dots (dots) in FIG. 7, a material having a high thermal conductivity (for example, powdered copper or the like) ) 61 is included (impregnated), for example, by about 60 wt%. In addition, as shown in FIG. 7, the material 61 having a high thermal conductivity is arranged so as to be substantially uniform throughout.
In addition, the code | symbol 62 in FIG. 7 has shown the backup ring.
The heat transfer material 71 is a plate-like member having a ring shape in plan view made of a material having high thermal conductivity (for example, copper, indium, etc.), and is one surface side of the piston ring 70 on the radially inner side (the upper side in FIG. 7). ).

According to the piston ring 70 according to the present embodiment, the heat generated in the piston ring 70 (that is, frictional heat generated when the piston ring 70 slides along the inner wall surface of the cylinder 6) Since the heat is transferred to the piston 3 having a large heat capacity through the material 61 and the heat transfer material 71 contained in the inside, the temperature rise of the piston ring 70 can be reduced.
Further, according to the booster pump 1 for a low temperature fluid provided with such a piston ring 70, the heat generation of the piston ring 70 is suppressed, so that the evaporation of the low temperature fluid sucked (inflowed) into the cylinder 6 is performed. (Vaporization) can be suppressed, and pump efficiency can be improved.

Next, a reference embodiment of a booster pump for a low temperature fluid according to the present invention will be described with reference to FIGS. FIG. 8 is a diagram for comparing a cryogenic fluid booster pump according to the present embodiment with a conventional cryogenic fluid booster pump, wherein (a) shows the relationship between the position of the piston ring and the leakage resistance. Graph (b) is a graph showing the relationship between the position of the piston ring and the pressure.
Since the cryogenic fluid booster pump 1 shown in FIG. 9 has been described in detail above, the description thereof is omitted here.

Now, each of the first piston ring, the second piston ring, and the third piston ring in FIG. 8 is located on one end surface (lower end surface in FIG. 9) side of the piston 3 in FIG. A piston ring, a piston ring located in the middle, and a piston ring located on the other end surface (upper end surface in FIG. 9) side of the piston 3.
In the booster pump for low-temperature fluid according to the present embodiment, as shown in FIG. 8A, the leakage resistance in the first piston ring becomes the smallest, and the leakage proceeds toward the second piston ring and the third piston ring. It is comprised so that resistance may become large gradually. As a result, as shown in FIG. 8B, the pressure P1 ′ on the one end surface (the lower end surface in FIG. 9) side of the first piston ring becomes the largest, and the other end surface (FIG. 9, the pressure P2 ′ on the upper end face) side, the pressure P3 ′ on the other end face (upper end face in FIG. 9) side of the second piston ring, and the other end face of the third piston ring (upper end face in FIG. 9). The pressure P4 ′ on the side gradually decreases.

The leakage resistance in each piston ring can be adjusted by, for example, a combination with a backup ring disposed radially inward of each piston ring.
The leakage resistance in each piston ring is, for example, a low leakage resistance such as a stepped joint (step joint) as the first piston ring, and a double stepped, for example, as the third piston ring. Use a joint with a large leakage resistance such as a double-angle joint, and use a second piston ring with a leakage resistance that is approximately between the first and third piston rings. Can also be adjusted.
Furthermore, when the first piston ring, the second piston ring, and the third piston ring have a joint with the same shape, for example, a stepped joint (step joint), the degree of opening of the joint is It is also possible to adjust the leakage resistance in each piston ring so that it is most open in the first piston ring and most closed in the third piston ring.

According to the booster pump 1 for low-temperature fluid according to the present embodiment, the leakage resistance of the piston ring located closest to one end surface (the lower end surface in FIG. 9) of the piston 3 that compresses the low-temperature fluid is minimized, The difference between the pressure P1 'on the one end face (lower end face in FIG. 9) side of the piston ring and the pressure P2' on the other end face (upper end face in FIG. 9) is greatly reduced compared to the conventional one. Therefore, the surface pressure that presses the outer peripheral surface of the piston ring against the inner peripheral surface of the cylinder 6 can be reduced, and the friction generated when the piston ring slides along the inner wall surface of the cylinder 6. Heat can be greatly reduced.
Further, since the heat generation of the piston ring and the cylinder 6 (that is, the cylinder block 5) is suppressed in this way, the evaporation (vaporization) of the low-temperature fluid sucked into (flowed into) the cylinder 6 is suppressed. And pump efficiency can be improved.

DESCRIPTION OF SYMBOLS 1 Booster pump for low temperature fluid 3 Piston 5 Cylinder 6 Cylinder block 7 Ring groove 8 Piston ring 8a Circumferential groove 20 Piston ring 21 Circumferential groove process part 22 Piston ring main body 30 Piston ring 30a Vertical groove 40 Piston ring 40a Diagonal groove 50 Piston ring 50a Reversing groove 60 Piston ring 61 High thermal conductivity material 70 Piston ring 71 Heat transfer material

Claims (3)

A piston ring disposed in a plurality of ring grooves formed on the outer peripheral surface of the piston,
A piston ring made of a resin including a material having high thermal conductivity therein, and arranged so that the high thermal conductivity material is distributed more on the low-pressure side radially inward. . A piston ring disposed in a plurality of ring grooves formed on the outer peripheral surface of the piston of the booster pump for low-temperature fluid ,
It is made of a resin containing a material with high thermal conductivity inside, and a recess having a rectangular shape in cross section extending to the inner peripheral surface along the circumferential direction is provided on the inner side in the radial direction of one surface on the low pressure side. The piston ring is characterized in that a heat transfer material made from a material having high thermal conductivity is disposed in close contact with the recess .   A booster pump for cryogenic fluid, comprising the piston ring according to claim 1.

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