JP2007138863A - Reciprocating fluid machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive reciprocating fluid machine which assures sliding performance and sealing performance between a piston and a cylinder bore. <P>SOLUTION: In the reciprocating fluid machine, the piston 18 slides while in contact with the cylinder bore 8 via a coating layer 23 covering a side face 23 of the piston 18. The piston 18 includes a diameter-increased portion 26 protruding from the side face 23 outward in the radial direction and covered with the coating layer 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reciprocating fluid machine applied to, for example, a compressor of a vehicle air conditioner.

As this type of reciprocating fluid machine, for example, Patent Document 1 discloses a compressor in which a coat layer is formed on a side surface of a piston. The coat layer has a uniform thickness, and a fluororesin is distributed on the surface of the coat layer so that the sliding characteristics between the piston and the cylinder bore are improved.
JP 2000-170657 A

In the case of the compressor of Patent Document 1, it is considered that the sliding characteristics between the piston and the cylinder bore are surely ensured by the fluororesin of the coat layer. Further, it is considered that the sealing property between the piston and the cylinder bore is improved by the coat layer. However, since the material fluororesin is expensive, the compressor itself is also expensive.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an inexpensive reciprocating fluid machine while ensuring sliding characteristics and sealing performance between a piston and a cylinder bore. There is to do.

In order to achieve the above object, according to the present invention, in a reciprocating fluid machine in which a piston slides on a cylinder bore via a coating layer covering the side surface of the piston, the piston is disposed radially outward from the side surface. A reciprocating fluid machine is provided that has a diameter-expanding portion that protrudes and is covered with the coating layer.
In a preferred embodiment, the coating layer contains PTFE (polytetrafluoroethylene).

As a preferred aspect, the enlarged diameter portion is located in the cylinder bore when the piston is located at a bottom dead center (Claim 3).
As a preferred embodiment, the diameter-expanded portion is separated from the lower end of the cylinder bore by 3 mm or more when the piston is located at the bottom dead center, and is 3 mm or more from the upper end of the cylinder bore when the piston is located at the top dead center. They are separated (claim 4).

  As a preferred embodiment, the protruding height of the enlarged diameter portion from the side surface is 35 μm or less (Claim 5).

According to the reciprocating fluid machine of the first to fifth aspects of the present invention, since the enlarged diameter portion is formed on the side surface of the piston, the volume of the coating layer is reduced corresponding to the volume of the enlarged diameter portion. For this reason, the material cost of the coating layer per piston is reduced, and the reciprocating fluid machine becomes inexpensive.
In the reciprocating fluid machine according to claim 2, since PTFE which is a main component of the coating layer is expensive, the material cost is greatly reduced, and the reciprocating fluid machine is significantly cheaper.

  In the reciprocating fluid machine according to claim 3, when the piston is located at the bottom dead center, the enlarged diameter portion is located within the cylinder bore. Therefore, at this time, the enlarged diameter portion is separated from the lower end of the cylinder bore, and the lower end portion of the coating layer located at the lower end is thicker than the portion of the coating layer covering the enlarged diameter portion. Here, when the piston is located at the bottom dead center, the lower end portion of the covering layer located at the lower end of the cylinder bore is likely to wear and peel off, but the lower end portion of the covering layer is the portion of the covering layer that covers the enlarged diameter portion. The thickness of the lower end side portion of the coating layer is sufficiently secured. As a result, according to this fluid machine, the wear resistance and the peel resistance of the lower end portion of the coating layer are ensured, and the sliding characteristics and sealing properties of the coating layer are ensured over a long period of time.

In the reciprocating fluid machine according to claim 4, the enlarged-diameter portion is separated from the lower end of the cylinder bore by 3 mm or more when the piston is located at the bottom dead center, and is 3 mm from the upper end of the cylinder bore when the piston is located at the top dead center. Since they are separated from each other, the sliding properties and sealing properties of the coating layer are reliably ensured over a long period of time.
In the reciprocating fluid machine according to claim 5, since the protruding height of the enlarged diameter portion from the side surface of the piston is 35 μm or less, the thickness of the coating layer covering the side surface of the piston is equal to the thickness of the coating layer covering the enlarged diameter portion. It is not too thick compared to the thickness of the part. This ensures that the fluid machine is inexpensive.

Fig.1 (a) and FIG.1 (b) show schematic structure of the reciprocating fluid machine of one Embodiment of this invention, and a fluid machine is used as a compressor of a vehicle air conditioner, for example.
The fluid machine includes a cylinder head 2, and a suction chamber 3 and a discharge chamber 4 are defined inside the cylinder head 2. The cylinder head 2 is connected to one end of a cylindrical cylinder block 6 via a valve plate 7, and the cylinder block 6 has, for example, seven cylinder bores 8.

  The cylinder bores 8 are arranged concentrically at equal intervals in the circumferential direction of the cylinder block 6, and each cylinder bore 8 passes through the cylinder block 6 in the axial direction thereof. Each cylinder bore 8 has an open end opened at both end faces of the cylinder block 6, and the open end of the cylinder bore 8 on the cylinder head 2 side is connected to the suction chamber 3 and the discharge chamber via the suction hole and the discharge hole of the valve plate 7. 4 can be communicated.

  A crankcase 10 is connected to the other end of the cylinder block 6, and a drive shaft 12 is rotatably disposed in the center of the crankcase 11 surrounded by the crankcase 10. The drive shaft 12 is parallel to the axis of the cylinder bore 8, and the cylinder bore 8 is arranged concentrically around the drive shaft. An electromagnetic clutch 13 is fixed to one end of the drive shaft 12 protruding from the crankcase 10, and the electromagnetic clutch 13 can intermittently transmit power from the engine to the drive shaft 12.

  The drive shaft 12 passes through the annular swash plate 16, and the swash plate 16 can rotate integrally with the drive shaft 12 while being inclined with respect to the drive shaft 12. The outer peripheral portion of the swash plate 16 reaches the position of the cylinder bore 8 when viewed in the radial direction of the drive shaft 12, and the tail portion 19 of each piston 18 projecting into the crank chamber 11 from the opening end of the cylinder bore 8 on the crankcase 10 side is The outer peripheral portion of the swash plate 16 is slidably sandwiched via a pair of hemispherical shoes 20.

  The piston 18 has a cylindrical main body portion 22 that continues to the tail portion 19, and the main body portion 22 is slidably fitted to the cylinder bore 8. On the side surface 23 (outer peripheral surface) of the main body portion 22 of the piston 18, a fluororesin coating layer 24 mainly composed of PTFE (polytetrafluoroethylene) is formed over substantially the entire area, and the outer peripheral surface of the coating layer 24 is a cylinder bore. A cylindrical shape having an outer diameter substantially the same as the inner diameter of 8 is formed. Therefore, the main body portion 22 of the piston 18 slides on the inner peripheral surface of the cylinder bore 8 via the coating layer 24.

Moreover, each piston 18 has the enlarged diameter part 26 which protruded to the radial direction outer side from the main-body part 22, as expanded and shown in FIG. 2 (a), FIG.2 (b). The enlarged diameter portion 26 protrudes from the side surface 23 of the main body portion 22 at a constant height H over one circumference, and the outer peripheral surface 27 of the enlarged diameter portion 26 has a cylindrical shape coaxial with the side surface 23 of the main body portion 22.
The protruding height H of the enlarged diameter portion 26 is smaller than the thickness T1 of the portion of the covering layer 24 that covers the side surface 23 of the main body portion 22. Surface 27 is also covered. In other words, the enlarged diameter portion 26 is embedded in the coating layer 24.

However, regardless of the presence of the enlarged diameter portion 26, the outer peripheral surface of the covering layer 24 has a cylindrical shape with a constant outer diameter, and in the covering layer 24, the portion covering the outer peripheral surface 27 of the enlarged diameter portion 26. The thickness T2 is thinner than the thickness T1 of the portion covering the side surface 23 of the main body portion 22 by the protrusion height H of the enlarged diameter portion 26.
On the other hand, when viewed in the axial direction of the piston 18, the enlarged diameter portion 26 is separated from both ends of the main body portion 22, and the side surface 23 of the main body portion 22 is divided into a region 23 a on the valve plate 7 side and a region 23 b on the crank chamber 11 side. It is divided into and.

  More specifically, as shown in FIG. 2A, the enlarged diameter portion 26 in the main body portion 22 is located in the cylinder bore 8 even when the piston 18 is located at the bottom dead center. It is set as follows. For this reason, when the piston 18 is located at the bottom dead center, the portion of the covering layer 24 covering the region 23b, that is, the portion of the covering layer 24 having the thickness T1, is located at the opening end of the cylinder bore 8 on the crank chamber 11 side. To do.

  In the fluid machine described above, power from the engine is transmitted to the drive shaft 12 via the electromagnetic clutch 13, and the swash plate 16 rotates as the drive shaft 12 rotates. The rotation of the swash plate 16 is converted into a reciprocating motion of each piston 18 via the shoe 20, and each piston 18 has a bottom dead center as shown in FIGS. 1 (a) and 2 (a), and FIG. b) reciprocates between the top dead center and as shown in FIG.

  The reciprocating motion of each piston 18 includes the suction process of the refrigerant gas from the suction chamber 3 to the cylinder bore 8 through the suction hole, the compression process of the refrigerant gas in the cylinder bore 8, and the cylinder bore 8 to the discharge chamber 4 through the discharge hole. A series of processes consisting of a refrigerant gas discharge step is provided. In this process, each piston 18 slides on the cylinder bore 8 via the coating layer 24, and sliding characteristics and sealing performance between the piston 18 and the cylinder bore 8 are ensured.

And in the fluid machine mentioned above, by forming the enlarged diameter part 26 in the piston 18, the volume of the coating layer 24 decreases corresponding to the volume of the enlarged diameter part 26. For this reason, the material cost of the coating layer 24 per piston 18 is reduced, and the fluid machine becomes cheaper than before.
Further, in the fluid machine described above, when the piston 18 is located at the bottom dead center, the enlarged diameter portion 26 is located in the cylinder bore 8. Accordingly, at this time, the enlarged diameter portion 26 is separated from the opening end (lower end) of the cylinder bore 8 on the crank chamber 11 side, and the thickness T1 of the lower end side portion of the covering layer 24 located at the lower end is set to the enlarged diameter portion. It is thicker than the thickness T2 of the portion of the coating layer 24 that covers 26.

  Here, when the piston 18 is located at the bottom dead center, the lower end portion of the coating layer 24 located at the lower end of the cylinder bore 8 is likely to be worn or peeled off. Thickness T1 of the lower end side part of the coating layer 24 is sufficiently secured, being thicker than the covering layer part to be covered. As a result, according to this fluid machine, the wear resistance and the peel resistance of the lower end side portion of the coating layer 24 are ensured, and the sliding characteristics and the sealing properties of the coating layer 24 are ensured for a long period of time.

In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation is possible, for example, the cylinder bore 8 in a fluid machine is not restricted to seven pieces, The number is not restrict | limited at all.
In one embodiment, the covering layer 24 has a cylindrical outer peripheral surface. However, the covering layer only needs to be formed in a region where the main body portion of the piston and the cylinder bore slide, and the outer surface of the covering layer is Depending on the shape of the main body and the cylinder bore, it may not be cylindrical.

  In one embodiment, the material of the coating layer 24 is a fluororesin mainly composed of PTFE, but the material of the resin layer 24 is not particularly limited. However, the coating layer 24 of a fluororesin mainly composed of PTFE is preferable because it has excellent wear resistance. In the case of the coating layer 24 of a fluororesin mainly composed of PTFE, PTFE is expensive. Therefore, the material cost reduction by the enlarged diameter portion 26 is large, and the fluid machine is significantly inexpensive.

  In one embodiment, the enlarged diameter portion 26 is located in the middle of the main body portion 22 of the piston 18, but the enlarged diameter portion 26 is located in the region of the main body portion 22 of the piston 18 where the coating layer 24 is formed. It only has to be. However, the enlarged diameter portion 26 is preferably located in the cylinder bore 8 when the piston 18 is located at the bottom dead center, and the distance D1 from the lower end of the cylinder bore 8 to the enlarged diameter portion 26 (see FIG. 2A). Is more preferably 3 mm or more. This is because, when the piston 18 is located at the bottom dead center, the coating layer 24 located at the lower end of the cylinder bore 8 is likely to be worn or peeled off, so that the thickness of the coating layer 24 is sufficiently secured. .

  When the piston 18 is located at the top dead center, the distance D2 (see FIG. 2A) from the opening end (upper end) of the cylinder bore 8 on the valve plate 7 side to the enlarged diameter portion 26 is 3 mm or more. Is preferred. When the piston 18 is located at the top dead center, the coating layer 24 located near the upper end of the cylinder bore 8 is likely to be worn or peeled off, so that the thickness of the coating layer 24 can be sufficiently secured. is there.

Therefore, the length (width W) of the enlarged diameter portion 26 viewed in the axial direction of the piston 18 is appropriately set in consideration of the length of the main body portion 22 and the cylinder bore 8, the stroke length of the piston 18, and the distances D1 and D2. The
In one embodiment, the higher the protrusion height H of the enlarged diameter portion 26 is, the more material cost is reduced. However, the protrusion height H is preferably 35 μm or less. When the protrusion height H is 35 μm or less, the thickness T1 of the coating layer 24 covering the side surface 23 of the main body 22 of the piston 18 is larger than the thickness T2 of the coating layer 24 covering the expanded diameter portion 26. It will not be too thick. This ensures that the fluid machine is inexpensive.

  The thickness T1 is preferably in the range of 15 μm or more and 40 μm or less, and the thickness T2 is preferably 5 μm or more. This is because when the thickness T1 is smaller than 15 μm, sufficient wear resistance and peel resistance cannot be secured, and when the thickness T1 exceeds 40 μm, the wear resistance and peel resistance are hardly improved. On the other hand, if the thickness T2 is less than 5 μm, sufficient wear resistance cannot be ensured.

In one embodiment, one piston 18 has one enlarged diameter portion 26, but may have a plurality of enlarged diameter portions.
In one embodiment, the outer peripheral surface of the covering layer 24 slides with the inner peripheral surface of the cylinder bore 8, but the piston 18 has one or more piston rings 30 as shown in FIG. Also good.

  Finally, it is needless to say that the reciprocating fluid machine of the present invention can be applied to a double-headed swash plate compressor or a swing plate compressor.

It is a figure which shows schematic structure of the reciprocating fluid machine of one Embodiment of this invention, (a) shows a state when one piston is located in a bottom dead center, (b) shows one piston. The state when located at the top dead center is shown. It is a figure which expands and shows the enlarged diameter part vicinity of the piston in the fluid machine of FIG. 1, (a) shows a state when one piston is located in a bottom dead center, (b) shows one piston. The state when located at the top dead center is shown. It is the figure which expanded and showed the diameter expansion part vicinity of the piston of the modification applied to the fluid machine of FIG.

Explanation of symbols

8 Cylinder bore 18 Piston 23 Side surface 24 Cover layer 26 Expanded portion

Claims (5)

In a reciprocating fluid machine in which a piston slides on a cylinder bore through a coating layer covering the side surface of the piston,
2. The reciprocating fluid machine according to claim 1, wherein the piston has a diameter-expanding portion protruding radially outward from the side surface and covered with the coating layer.   The reciprocating fluid machine according to claim 1, wherein the coating layer contains PTFE as a main component.   3. The reciprocating fluid machine according to claim 1, wherein the enlarged diameter portion is located in the cylinder bore when the piston is located at a bottom dead center.   The diameter-expanded portion is separated from the lower end of the cylinder bore by 3 mm or more when the piston is located at the bottom dead center, and is separated from the upper end of the cylinder bore by 3 mm or more when the piston is located at the top dead center. The reciprocating fluid machine according to claim 3.   The reciprocating fluid machine according to any one of claims 1 to 4, wherein a protruding height of the enlarged diameter portion from the side surface is 35 µm or less.

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