Rolling piston compressor

Abstract

The invention relates to a fluid compressor (10), particularly for thermoregulation circuits, said compressor (10) comprising: - a cylinder (12), oriented about a first axis (A), - a drive shaft (14), coaxial with the first axis (A), - a cylindrical piston (16), oriented about a second axis (B) offset parallel to the first axis (A), said piston (16) being coupled to the drive shaft (14) to roll against a wall (18) of said cylinder (12) in an orbital motion, forming two compression chambers (22, 24) of the fluid separated by an interface zone (20) between the piston (16) and the cylinder (12), said interface zone (20) being movable with said piston (16), said compressor (10) further comprising a means (50) for actuating the piston (16) by reaction on the shaft (14) to generate a contact force of the piston (16) with the cylinder (12) at the level of said interface area (20).

Description

Technical field of the invention

[0001] The invention relates to a fluid compressor, in particular for a thermoregulation circuit such as an air conditioning circuit of a motor vehicle. Technical background

[0002] A roll compressor, or rolling piston compressor, is a type of compressor used in temperature control circuits, such as heating, ventilation, and / or air conditioning systems. Unlike traditional compressors that use pistons or screw gears to compress the refrigerant, a roll compressor uses a movable cylindrical piston that is mounted to roll eccentrically within a cylindrical stator.

[0003] The stator is the fixed part of the roll compressor that surrounds the cylindrical piston. It has a cylindrical wall, hereafter referred to as the cylinder, oriented along a first axis, on which the piston rolls, and which together form two compression chambers where the fluid is compressed successively. The two fluid compression chambers have a variable volume, determined by the position of an interface zone between the rolling piston and the cylinder; this interface zone is movable with the rolling piston.

[0004] To ensure the eccentric movement of the rolling piston, the compressor includes a drive shaft coaxial with the first axis. The piston is eccentric and oriented around a second axis that is offset parallel to the first axis. The offset of the axes and the piston's dimensions induce a contact force in the interface zone between the piston and the cylinder.

[0005] The efficiency of such a compressor depends directly on the contact pressure between the piston and the cylinder. It is at the contact between the piston and the cylinder that micro-leaks are likely to occur, and that some of the gas already compressed in the compression chamber located downstream of the piston is likely to leak into the compression chamber located upstream of the piston, due to the pressure differences between the two chambers.

[0006] There is therefore a real need for a rolling piston compressor benefiting from improved contact pressure between the piston and cylinder in the mobile interface area rotating with the rolling piston. Summary of the invention

[0007] The invention satisfies this need by proposing a fluid compressor comprising a means for increasing the contact pressure between the piston and the cylinder.

[0008] To this end, the invention proposes a fluid compressor, particularly for thermoregulation circuits, said compressor comprising: a cylinder, oriented along a first axis, a drive shaft, coaxial with the first axis, a cylindrical piston, oriented along a second axis offset parallel to the first axis, said piston being coupled to the drive shaft to roll against a wall of said cylinder in an orbital motion forming two fluid compression chambers separated by an interface zone between the piston and the cylinder, said interface zone being movable with said piston, said compressor further comprising a means of stressing the piston by reaction on the shaft to generate a contact force of the piston with the cylinder at the level of said interface zone.

[0009] Thanks to the actuation mechanism, the piston drive generates, particularly dynamically, an additional radial force beyond that obtained by simply offsetting the axes. This additional radial force increases the contact pressure between the piston and the cylinder, thereby improving the seal in the piston-cylinder interface and consequently increasing compressor performance.

[0010] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention: The loading means is adapted to load the piston in a direction of loading perpendicular to the first and second axes. The piston is supported by a bearing comprising an inner ring. The ring has a bore eccentric with respect to the second axis. The bore is received on the drive shaft. The ring is driven in rotation by the drive shaft. The loading means is interposed between the drive shaft and the inner ring of the bearing. The ring is rotationally connected to the shaft by a drive finger oriented in the direction of loading. The drive finger extends radially from the drive shaft. The drive finger is received with clearance between the edges of a notch formed in the inner ring of the bearing. The loading means is arranged by cooperation between the drive finger and the notch.The notch comprises a first edge oriented along said radial direction and a second opposite edge, which is inclined with respect to said direction to form said means, said second inclined edge being capable of transforming any stress exerted by said drive finger perpendicular to said second inclined edge into a stress exerted on said ring, said stress comprising at least one component acting along said direction of stress, the second inclined edge forms an angle of substantially 30 to 60 degrees with the first edge, the drive finger is formed at the end of a key, said key being received without play in a slot formed in the drive shaft, the piston comprises a bore receiving an outer ring of the bearing, mounted to rotate with respect to the inner ring, the bearing is a ball or roller bearing. Brief description of the figures

[0011] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the attached drawings in which: [ Fig. 1 ] There figure 1 is a schematic cross-sectional view of a compressor according to the invention, shown at the beginning of fluid compression; [ Fig. 2 ] There figure 2 is a schematic cross-sectional view of the compressor of the figure 1 represented at the end of fluid compression; Fig. 3 ] There figure 3 is a schematic cross-sectional view of the forces acting between a drive finger and an inner ring of a compressor piston bearing Figures 1 And 2 . Detailed description of the invention

[0012] As illustrated in Figures 1 And 2The invention relates to a rolling piston type fluid compressor 10, also known by its English acronym, "rolling compressor." Such a compressor 10 is intended, in particular, for use in a thermoregulation circuit, such as a circuit in a heating, ventilation, and / or air conditioning system of a motor vehicle. The fluid is composed, for example, of a refrigerant such as, in particular, a hydrofluorocarbon like the fluid known as R134a, or a gas such as carbon dioxide, also known as R744 in its use as a refrigerant.

[0013] The compressor 10 essentially comprises a cylinder 12, oriented about a first axis A. A drive shaft 14, coaxial with the first axis A, is mounted to rotate relative to this cylinder 12. This shaft 14 is generally driven by an electric motor. The cylinder 12 receives a cylindrical piston 16, oriented about a second axis B offset parallel to the first axis A.

[0014] The cylindrical piston 16, also called the rolling piston, is coupled to the drive shaft 14 so as to roll against a wall 18 of the cylinder 12. The movement of the cylindrical piston 16 is therefore an orbital movement, due to the offset between the axes A and B.

[0015] The cylindrical piston 16, during its movement, therefore defines in contact with the wall 18 of the cylinder 12 an interface zone 20 between the piston 16 and the cylinder 12, this interface zone 20 being mobile with the piston 16 during its movement.

[0016] The interface zone 20 delimits in the cylinder 12 two fluid compression chambers, respectively downstream compression chamber 24 and upstream compression chamber 22.

[0017] In the remainder of this description, the terms "upstream" and "downstream" will be used with reference to the direction of gas flow in the compressor 10, from upstream to downstream.

[0018] The compressor 10 further comprises an inlet port 26 and a discharge port 28 which are separated by a sliding tab 30 which is elastically and tightly returned to contact with the external surface of the piston 16. On the Figures 1 And 2 , piston 16 rotates clockwise.

[0019] In operation, the fluid to be compressed is introduced through the inlet port 26 and then confined upstream of the interface zone 20 by the piston 16 between the piston 16 and the wall 18 of the cylinder 12 in one of the chambers, namely the upstream chamber 22. In the other chamber, namely the downstream chamber 24, it is pushed back and simultaneously compressed towards the discharge port 28 through which it is discharged from the compressor 10 under high pressure.

[0020] According to this design, the pressure prevailing in the compression chambers 22, 24 is directly dependent, on the one hand, on the progression of the piston 16 towards the discharge port 28, and on the other hand on any losses by micro-leaks which may occur in the interface zone 20 between the piston 16 and the wall 18 of the cylinder 12.

[0021] Indeed, in the absence of pressure in the compression chambers, the contact pressure exerted by the piston 16 on the wall 18 is directly determined by the geometry of the piston 16, the wall 18, and the offset between the axes A and B of the piston 16.

[0022] The contact pressure is likely to be reduced during operation as the piston 16 moves and the volume of the downstream compression chamber 24 decreases, due to the establishment of an increasing pressure in this downstream compression chamber 24 exerted on the piston 16. Thus, the resulting force P of the pressure exerted on the cylinder 16 tends to create micro-leaks of fluid between the downstream compression chamber 24 and the upstream compression chamber 22, risking causing the piston to slightly lift due to the assembly clearances necessarily present.

[0023] The invention remedies this drawback by proposing a compressor 10 equipped with a means 54 for stressing the piston 16 towards the interface zone 20 in order to maintain, or even increase, the contact pressure exerted by the piston 16 on the wall 18 against the pressure P exerted on the piston 16 by the differential of fluid pressure between the two chambers 22, 24.

[0024] For this purpose, in accordance with the invention, the piston arousal means 54 acts by reaction on the shaft 14 to generate a contact force FR of the piston 16 with the cylinder 16 at the interface zone 20.

[0025] According to the invention, the excitation means 54 is particularly suitable for excitation of the piston 16 by applying the force FR along an excitation direction X which is perpendicular to the first and second axes A and B, that is to say in the plane of the Figures 1 And 2 .

[0026] Thanks to this means of stress 54, the contact pressure between the piston 16 and the cylinder 18 is increased, which makes it possible to improve the sealing in the interface area 20 between the piston 16 and the cylinder 18, and consequently to increase the performance of the compressor 10.

[0027] The invention applies in particular to a piston 16 drive configuration by shaft 14, according to which the piston 16 is supported by a bearing 32.

[0028] In this configuration, the bearing 32 comprises an inner ring 34 and an outer ring 36. The piston 16 has a bore 38 receiving the outer ring 36 of the bearing 32, mounted to rotate relative to the inner ring 34. Without limiting the invention, the bearing 32 comprises a ball bearing 40, or a roller bearing, but it could be another type of bearing.

[0029] The ring 34 has a bore 42, eccentric with respect to the second axis B of the ring. This bore 42 is received on the drive shaft 14.

[0030] To drive the piston 16, the inner ring 34 is rotationally linked to the shaft 14 by a drive finger 44.

[0031] The drive finger 44 extends radially along a radial direction R from the drive shaft 14. The finger 44 is received with clearance between the edges of a notch 48 formed in the inner ring 34 of the bearing 32. Without limiting the invention, this notch 48 is here oriented along the radial direction R.

[0032] Preferably, the drive finger 44 is formed at the end of a key 50, which is received without play in a slot 52 formed in the drive shaft 14.

[0033] As already mentioned, the stressing means 54 is suitable for stressing the piston 16 in a stressing direction which is perpendicular to the first and second axes A, B, i.e. in the plane of figures 4 to 6. In the present case, and without limiting the invention, this stressing direction corresponds to the radial direction R.

[0034] For this purpose, more specifically, the stressing means 54 is interposed between the drive shaft 14 and the inner ring 34 of the bearing.

[0035] The stressing means 54 can be made in different ways, for example by an elastic means with radial effect interposed between the drive shaft 14 and the inner ring 34 of the bearing.

[0036] However, preferably, the actuation means 54 is arranged by cooperation between the drive finger 44 and the notch 48.

[0037] For this purpose, the notch 48 has a first edge 46 oriented along the direction R and a second opposite edge 46', which is inclined with respect to the direction R to form said means 54, said second inclined edge 46' being able to transform any stress F exerted by the drive finger 44 perpendicular to said second inclined edge 46' into a drive stress F exerted on the ring 46 along a direction X which is not strictly tangential, which would be the case if the edges 46, 46' were parallel.

[0038] As can be seen on the figure 3The force F is decomposed into a tangential component FT and at least one component FR acting along the direction R of the force application. Indeed, the force exerted on the finger 44 on the edge 46' is necessarily perpendicular to this edge 46', which is itself inclined. Consequently, the inclination of the edge 46' induces a radial component FR of the force F. By reaction on the finger 44, and therefore on the shaft 14, this component is transmitted to the piston 16.

[0039] Preferably, the second inclined edge 46' forms an angle of approximately 30 to 60 degrees with the first edge 46.

[0040] The drive of the piston 16 by the shaft 14 generates, particularly dynamically once the drive is effective and the shaft 14 drives the ring 34, an additional radial force FR beyond that obtained by simply offsetting the axes. This force FR increases the contact pressure between the piston 16 and the cylinder 12, thereby improving the seal in the interface zone 20 between the piston 16 and the cylinder 12 and, consequently, increasing the compressor's performance.

Claims

1. Fluid compressor (10), particularly for thermoregulation circuits, said compressor (10) comprising: - a cylinder (12), oriented about a first axis (A), - a drive shaft (14), coaxial with the first axis (A), - a cylindrical piston (16), oriented about a second axis (B) offset parallel to the first axis (A), said piston (16) being coupled to the drive shaft (14) to roll against a wall (18) of said cylinder (12) in an orbital motion, forming two compression chambers (22, 24) of the fluid separated by an interface zone (20) between the piston (16) and the cylinder (12), said interface zone (20) being movable with said piston (16), said compressor (10) further comprising a means (50) for activating the piston (16) by reaction on the shaft (14) to generate a contact force of the piston (16) with the cylinder (12) at the level of said interface area (20).

2. Fluid compressor (10) according to the preceding claim, wherein the stressing means (50) is able to stress the piston (16) along a stressing direction (R) perpendicular to the first and second axes (A,B).

3. Fluid compressor (10) according to any one of the preceding claims, in which said piston (16) is carried by a bearing (32) having an inner ring (34), said ring (34) having an eccentric bore (42) with respect to the second axis (B), this bore (42) being received on the drive shaft (14), said ring (34) being driven in rotation by said drive shaft (14), and in which the stressing means (50) is interposed between said drive shaft (14) and the inner ring (34) of the bearing (32).

4. Fluid compressor (10) according to the preceding claim, in which the inner ring (34) is rotationally linked to said shaft (14) by a drive finger (44) which is oriented along said direction of stress (R), extends radially from the drive shaft (14), and is received between the edges (46, 46') of a notch (48) formed in the inner ring (34) of the bearing (32), said stressing means (50) being arranged by cooperation between said drive finger (14) and said notch (48).

5. Fluid compressor (10) according to the preceding claim, wherein the notch (48) has a first edge (46) oriented along said direction and a second opposing edge (46'), which is inclined with respect to said direction (R) to form said means (50), said second inclined edge (46') being capable of transforming any stress (F) exerted by said drive finger (44) perpendicular to said second inclined edge (46') into a stress (F) exerted on said ring (34), said stress having at least one component (F R ) exercised according to said direction of solicitation (R).

6. Compressor (10) according to the preceding claim, wherein the second inclined edge (46') forms an angle ( a ) of approximately 30 to 60 degrees with the first edge (46).

7. Compressor (10) according to any one of claims 4 to 6, in which the drive finger (44) is formed at the end of a key (50), said key (50) being received without play in a slot (52) formed in the drive shaft (14).

8. Compressor(10) according to any one of claims 3 to 7, in which the piston (16) has a bore (38) receiving an outer ring (36) of the bearing (32), mounted to rotate relative to the inner ring (34).

9. Compressor according to (10) any one of claims 3 to 8, wherein the bearing (32) is a ball or roller bearing.

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