Reciprocating compressor
The pistonless oil pump in reciprocating compressors addresses maintenance and efficiency issues by using a hollow body with valves and a reciprocating motion for oil circulation, enhancing service life and reducing costs.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-11-07
- Publication Date
- 2026-05-15
AI Technical Summary
Existing reciprocating compressors require complex oil pumps with pistons for lubrication and sealing, leading to increased maintenance needs and reduced efficiency.
A pistonless oil pump design using a hollow body with valves and a reciprocating motion to circulate oil, eliminating the need for a separate piston and reducing component complexity.
This design enhances the service life, reduces maintenance requirements, and improves efficiency by simplifying the oil circulation process, thereby lowering manufacturing and maintenance costs.
Smart Images
Figure EP2025082284_15052026_PF_FP_ABST
Abstract
Description
[0001] R. 412007
[0002] - 1 -
[0003] Description
[0004] title
[0005] reciprocating compressor
[0006] The invention relates to a reciprocating compressor, in particular for cooling devices.
[0007] State of the art
[0008] Reciprocating compressors are known from the state of the art.
[0009] For the lubrication and sealing of reciprocating compressors, an oil film is necessary in the gap between a piston and a cylinder. Oil pumps are used to create an oil circuit for a reciprocating compressor. The oil pumps circulate oil using a piston located inside the pump.
[0010] A reciprocating pump is known from US 8,070,460 B2.
[0011] Disclosure of the invention
[0012] The object underlying the invention can be seen as providing an improved reciprocating compressor. In particular, the reciprocating compressor should have an improved service life, reduced maintenance requirements, and at the same time high efficiency and wear resistance.
[0013] This problem is solved using a reciprocating compressor according to the independent claim. Advantageous embodiments are the subject of the dependent claims. R. 412007
[0014] - 2 -
[0015] According to a first aspect of the invention, a reciprocating compressor is provided, comprising: a cylinder, a piston arranged to be linearly movable within the cylinder, an oil circuit for building up an oil film in a gap between an inner wall of the cylinder and an outer wall of the piston, an oil pump for pumping oil from an oil reservoir for the oil circuit, wherein the oil pump has a hollow body with a first opening and a second opening, wherein the first opening is arranged in the oil reservoir, wherein a first valve is provided in the hollow body between the first opening and the second opening, wherein the first valve allows an inflow of oil into the hollow body and makes it difficult or prevents a backflow of oil from the hollow body into the oil reservoir, wherein the second opening is arranged outside the oil reservoir and is connected to the gap, wherein means are provided to generate a reciprocating movement of the hollow body.wherein, by means of the back-and-forth movement of the hollow body, oil from the oil reservoir can be conveyed through the first opening, via the valve, to the second opening in the gap.
[0016] This allows, for example, the technical advantage of providing an improved reciprocating compressor. The proposed reciprocating compressor offers the particular advantage that an oil film can be built up in a gap between the inner and outer walls of the cylinder using a pistonless oil pump. For this purpose, the oil pump has a hollow body with a first and a second opening, and a first valve that allows oil to flow into the hollow body and restricts or prevents backflow. Furthermore, means are provided to enable a reciprocating motion of the hollow body. This reciprocating motion allows oil to be pumped from the oil reservoir through the first opening, via the valve, to the second opening and into the gap of the reciprocating compressor.Consequently, the proposed reciprocating compressor does not require an additional piston for the oil pump. The oil pump can circulate the oil to build up an oil film by moving the hollow body back and forth, even without a piston. This allows for a reduction in the component size of the proposed reciprocating compressor (R. 412007).
[0017] - 3 - will be achieved and reduced manufacturing and maintenance costs will be reached.
[0018] In another embodiment, the first valve of the hollow body is designed as a check valve, in particular as a disc valve or ball valve.
[0019] This allows, for example, the technical advantage of making the transfer of oil from the first opening to the second opening in the oil circuit more efficient. Using a check valve, and in particular a disc valve or ball valve, the backflow of oil from the hollow body into the oil reservoir can be made particularly difficult or prevented.
[0020] In a further embodiment, a second valve is provided between the first valve and the second opening of the hollow body. This second valve allows oil to drain from the hollow body through the second opening, while hindering or preventing backflow of oil through the second opening into the hollow body. The second valve is specifically designed as a check valve.
[0021] This allows, for example, the technical advantage of further increasing the efficiency of the reciprocating compressor. The second valve can advantageously restrict the backflow of oil into the hollow body, thereby improving the flow of oil to the oil circuit. A disc valve or a ball valve can be used as the check valve.
[0022] In a further embodiment, at least one section of the hollow body extends along a first longitudinal axis, wherein means are provided to generate the back-and-forth movement of the hollow body essentially in the direction of the first longitudinal axis.
[0023] This allows, for example, the technical advantage that the oil can be conveyed particularly quickly and efficiently for the oil circuit using the hollow body. Through the back-and-forth movement of the hollow body in R. 412007
[0024] - 4 -
[0025] The oil pump for the reciprocating compressor can be operated particularly efficiently in the direction of the first longitudinal axis.
[0026] In another embodiment, the hollow body is coupled to the piston, whereby the back-and-forth movement of the hollow body can be generated using the piston.
[0027] This allows, for example, the technical advantage of making the reciprocating compressor more efficient to manufacture. By coupling the piston and the hollow body, the piston can generate the reciprocating motion of the hollow body. Consequently, additional components that generate this reciprocating motion can be omitted.
[0028] This allows for a reduction in the number of components required for the reciprocating compressor.
[0029] In a further embodiment, the hollow body is tubular in shape with a first section, wherein the first section extends along a first longitudinal axis, wherein the first opening is substantially arranged on the first longitudinal axis and is located in a first end region of the hollow body.
[0030] This allows, for example, the technical advantage that the oil can be conveyed particularly well using the hollow body.
[0031] In another embodiment, the second opening is essentially arranged on the first longitudinal axis and in a second end region of the tubular hollow body.
[0032] This allows, for example, the technical advantage that the oil essentially only needs to be transported along the first longitudinal axis to the second end area of the tubular hollow body and can therefore be conveyed more efficiently.
[0033] In a further embodiment, the tubular hollow body has a second section, wherein the second section extends along a second longitudinal axis R. 412007
[0034] - 5 - extends, wherein the second longitudinal axis is arranged transversely to the first longitudinal axis, wherein the second section is arranged in a second end region of the tubular hollow body, and wherein the second opening is substantially arranged on the second longitudinal axis.
[0035] This allows, for example, the technical advantage of redirecting the oil flow direction within the hollow body. In this embodiment, it is possible, for instance, to convey the oil through the hollow body in an L-shape within the oil pump.
[0036] In another embodiment, the first section has a first cross-section and the second section has a second cross-section, wherein the first cross-section is larger than the second cross-section.
[0037] This allows, for example, the technical advantage of accelerating the oil within the hollow body and transporting it more efficiently from the first opening to the second. The larger first cross-section and the smaller second cross-section enable the change in volume within the hollow body to accelerate the oil between the first and second sections.
[0038] The invention is explained in more detail below using exemplary embodiments. These include:
[0039] Fig. 1 shows a reciprocating compressor according to a first exemplary embodiment,
[0040] Fig. 2 shows a first exemplary embodiment of an oil pump for the reciprocating compressor,
[0041] Fig. 3 shows a second exemplary embodiment of the oil pump for the reciprocating compressor,
[0042] Fig. 4 shows an exemplary back-and-forth movement of the oil pump based on the second exemplary embodiment, R. 412007
[0043] - 6 -
[0044] Fig. 5 shows a third exemplary embodiment of the oil pump for the reciprocating compressor,
[0045] Fig. 6 shows a fourth exemplary embodiment of the oil pump for the reciprocating compressor,
[0046] Fig. 7 shows a fifth exemplary embodiment of the oil pump for the reciprocating compressor.
[0047] Fig. 1 shows a reciprocating piston compressor 10 according to a first exemplary embodiment.
[0048] The reciprocating compressor 10 comprises a cylinder 11 and a piston 15, which is arranged to move linearly within the cylinder 11. The reciprocating compressor 10 is intended for use in refrigeration equipment. For example, the reciprocating compressor 10 can be used in a refrigerator or a freezer.
[0049] For clarity, cylinder 11 and piston 15 are shown in a sectional view. The linear movement of piston 15 is indicated by a second arrow 7. The reciprocating compressor 10 includes an oil circuit 1 for building up an oil film 2 in a gap 5. The gap 5 is formed between an inner wall 12 of cylinder 11 and an outer wall 16 of piston 15.
[0050] The reciprocating compressor 10 also includes an oil pump 20. The oil pump 20 serves to pump oil 3 from an oil reservoir 4 for the oil circuit 1.
[0051] The oil pump 20 has a hollow body 30 with a first opening 31 and a second opening 32. The first opening 31 is located in the oil reservoir 4, and a first valve 35 is provided between the first opening 31 and the second opening 32.
[0052] The first valve 35 is designed to allow oil 3 to flow into the hollow body 30 and to hinder or prevent backflow of oil 3 from the hollow body 30 into the oil reservoir 4. The first valve 35 is, for example, R. 412007.
[0053] - 7 - designed as a check valve and can in particular be designed as a disc valve or ball valve.
[0054] The second opening 32 is located outside the oil reservoir 4 and is connected to the oil circuit 1. A second valve 36, for example, can be provided between the first valve 35 and the second opening 32. The second valve 36 is designed to allow oil 3 to drain from the hollow body 30 via the second opening 32 and to hinder or prevent backflow of oil 3 through the second opening 32 into the hollow body 30. The second valve 36 is, for example, a check valve and can be designed as a disc valve or a ball valve.
[0055] Furthermore, means are provided to generate a back-and-forth movement of the hollow body 30. The hollow body is fluidically connected to the gap 5 at the second opening 32, for example via a hose.
[0056] The back-and-forth movement can, for example, be a repetitive motion, which is indicated in this embodiment by a first arrow 6. The back-and-forth movement of the hollow body 30 can, for example, be generated by an additional unit attached to the hollow body 30. For example, a motor can be connected to the hollow body to generate the back-and-forth movement of the hollow body 30.
[0057] In this exemplary embodiment, the hollow body 30 is connected to the piston 15 via a connecting part 8. This allows the reciprocating movement of the hollow body 30 to be generated directly by means of the piston 15.
[0058] In this embodiment, the hollow body 30 extends along a first longitudinal axis 41 and the means are designed to generate the back-and-forth movement of the hollow body 30 in the direction of the first longitudinal axis 41.
[0059] By means of the back-and-forth movement of the hollow body 30, the oil 3 can be conveyed from the oil reservoir 4 via the first opening 31, through the first valve 35, to the second opening 32 in the oil circuit 1. R. 412007
[0060] - 8 -
[0061] Fig. 2 shows a first exemplary embodiment of an oil pump 20 for the reciprocating compressor.
[0062] The oil pump 20 has a hollow body 30 with a first opening 31 and a second opening 32. By way of example, the hollow body 30 is tubular and extends along the first longitudinal axis 41. The hollow body 30 has, by way of example, a circular cross-section. The hollow body 30 can have any possible cross-sectional shape and, for example, can also be rectangular, square, or oval.
[0063] In this embodiment, the first opening 31 is arranged on the first longitudinal axis 41 and in a first end region 61. Furthermore, the first opening 31 is arranged within the oil reservoir 4. In this embodiment, the second opening 32 is also arranged on the first longitudinal axis 41 and in a second end region 62. The second opening 32 is located outside the oil reservoir 4.
[0064] The first valve 35 is provided between the first opening 31 and the second opening 32. The first valve 35 is, for example, a check valve. In particular, the first valve 35 can be designed as a disc valve or a ball valve.
[0065] The back-and-forth movement of the hollow body 30 is schematically indicated by the first arrow 6. In this embodiment, the back-and-forth movement of the hollow body 30 can be generated in the direction of the first longitudinal axis 41.
[0066] Fig. 3 shows a second exemplary embodiment of the oil pump 20 for the reciprocating compressor.
[0067] The oil pump 20 is essentially the same as the oil pump shown in Fig. 1.
[0068] The oil pump 20, as previously described, serves to pump oil 3 from the oil reservoir 4 to a gap (not shown). The oil pump 20 has a hollow body 30 with a first opening 31. Furthermore, the hollow body 30 has a second opening 32. R. 412007
[0069] - 9 -
[0070] The hollow body 30 extends, by way of example, along the first longitudinal axis 41. The hollow body 30 is, by way of example, tubular in shape. The first opening 31 is, by way of example, arranged on the first longitudinal axis 41 and in the first end region 61. The second opening 32 is also arranged on the first longitudinal axis 41 and in the second end region 62 of the tubular hollow body 30.
[0071] The first opening 31 is located in the oil reservoir 4, and the tubular hollow body 30 has the first valve 35 between the first opening 31 and the second opening 32. The first valve 35 allows oil 3 to flow into the hollow body 30 and restricts or prevents backflow of oil 3 from the hollow body 30 back into the oil reservoir 4.
[0072] The second opening 32 is located outside the oil reservoir. The second opening 32 can be connected to the gap (not shown). Furthermore, means are provided to generate a reciprocating movement of the hollow body 30. The reciprocating movement of the hollow body 30 is illustrated by a first arrow 6. In this embodiment, the means are designed to generate the reciprocating movement of the hollow body 30 in the direction of the first longitudinal axis 41.
[0073] The second valve 36 is provided, by way of example, between the first valve 35 and the second opening 32 of the hollow body 30. The second valve 36 allows oil 3 to drain from the hollow body 30 via the second opening 32 and makes it difficult for oil 3 to flow back into the hollow body 30 via the second opening 32.
[0074] The first valve 35 and the second valve 36 are, for example, check valves and can be designed in particular as ball valves or as disc valves.
[0075] The following section explains in more detail the operation of the oil pump 20 for the reciprocating compressor with reference to Fig. 4. R. 412007
[0076] - 10 -
[0077] Fig. 4 shows an exemplary back-and-forth movement of the oil pump 20 based on the second exemplary embodiment.
[0078] The following section explains in more detail the operation of the oil pump 20 for the reciprocating compressor using five schematic snapshots.
[0079] The embodiment of the oil pump 20 for the reciprocating compressor essentially corresponds to the embodiment of the oil pump 20 shown in Fig. 3. To avoid repetition, the geometric design of the oil pump 20 will not be discussed in detail below. Only a few elements of the oil pump 20 will be described.
[0080] The oil pump 20 has a hollow body 30. The hollow body 30 has a first opening 31 and a second opening 32. The hollow body 30 is, for example, designed as a tubular hollow body 30. The first valve 35 is provided between the first opening 31 and the second opening 32. The first valve 35 is located in the oil reservoir 4. The second opening 32 is located outside the oil reservoir 4. The second valve 36 is provided between the first valve 35 and the second opening 32.
[0081] The reciprocating motion of the oil pump 20 is described below in five snapshots, or for five positions 21, 22, 23, 24, and 25. By means of this reciprocating motion, oil 3 can be conveyed from the oil reservoir 4 via the first opening 31, through the first valve 35, to the second opening 32 in the gap (not shown).
[0082] In a first position 21, the hollow body 30 is in a lower end position. The first valve 35 and the second valve 36 are closed in this first position 21. Oil 3 is present between the valves 35 and 36 inside the hollow body.
[0083] In a second position 22, the hollow body 30 is in an upward movement. With the first valve 35 closed and the upward movement in place, the oil 3 inside the hollow body 30 is accelerated in the direction of movement, i.e., towards the second valve 36. R. 412007
[0084] - 11 -
[0085] In a third position 23, the hollow body 30 reaches an upper end position. In the third position 23, the inertia of the accelerated oil 3 causes the oil 3 to flow out through the second opening 32. The second valve 36 then opens.
[0086] In a fourth position 24, the hollow body 30 is in a downward movement. During this downward movement, the first valve 35 opens, and the oil 3 is not accelerated in the direction of movement but continues to flow in the opposite direction to the downward movement of the hollow body 30. The opening of the first valve 35 and the prevailing back pressure allow the oil 3 to flow into the hollow body 30 through the first opening 31 and the first valve 35.
[0087] In a fifth position 25, the hollow body 30 reaches a lower end position. The first valve 35 and the second valve 36 close at this time.
[0088] The described cycle can now be repeated continuously. By repeating this cycle, the oil 3 can be conveyed from the oil reservoir 4 to the second opening 32 in a gap of the reciprocating compressor (not shown), as described previously.
[0089] Fig. 5 shows a third exemplary embodiment of the oil pump 20 for the reciprocating compressor.
[0090] The oil pump 20 has a hollow body 30 with a first opening 31 and a second opening 32. A first valve 35 is provided between the first opening 31 and the second opening 32. The first valve 35 is designed to allow oil 3 to flow into the hollow body 30 and to hinder or prevent backflow of oil 3 from the hollow body 30. The first opening 31 is located in the oil reservoir 4. The second opening 32 is located outside the oil reservoir 4.
[0091] For example, a second valve 36 is provided between the first valve 35 and the second opening 32. The second valve 36 again serves to control an R. 412007
[0092] - 12 -
[0093] to allow oil 3 to drain from the hollow body 30 via the second opening 32 and to make it more difficult for oil 3 to flow back into the hollow body 30 via the second opening 32.
[0094] In this embodiment, the hollow body 30 is again tubular and has a first section 51. The first section 51 extends along the first longitudinal axis 41, with the first opening 31 being arranged substantially on the first longitudinal axis 41. The first opening 31 is located in a first end region 61 of the hollow body 30.
[0095] As an example, the tubular hollow body 30 has a second section 52. The second section 52 extends along a second longitudinal axis 42. The second longitudinal axis 42 is arranged transversely to the first longitudinal axis 41. In particular, the second longitudinal axis 42 is arranged orthogonally to the first longitudinal axis 41. The second section 52 is arranged in a second end region 62 of the hollow body 30. The second opening 32 is arranged on the second longitudinal axis 42.
[0096] The first section 51, for example, has a first cross-section 55, and the second section 52 has a second cross-section 56. The cross-sections 55 and 56 can, in particular, be circular. The cross-sections 55 and 56 can also be, for example, square, rectangular, or oval. In this embodiment, the first cross-section 55 is, by way of example, larger than the second cross-section 56.
[0097] The back-and-forth movement of the hollow body 30 is again represented by the first arrow 6. The hollow body 30 is arranged such that the back-and-forth movement is formed in the direction of the first longitudinal axis 41.
[0098] By means of the back-and-forth movement, oil 3 can be pumped from oil reservoir 4 back into the oil circuit. For more efficient transport of oil 3 from oil reservoir 4, the first cross-section 55 and the second cross-section 56 are designed differently. R. 412007
[0099] - 13 -
[0100] The oil 3 can be accelerated within the hollow body 30 due to the change in volume between the first cross-section 55 and the second cross-section 56.
[0101] Fig. 6 shows a fourth exemplary embodiment of the oil pump 20 for the reciprocating compressor.
[0102] The oil pump 20 is essentially the same as the oil pump 20 from Fig. 5.
[0103] To avoid repetition at this point, only the differences to the oil pump 20 from Fig. 4 will be discussed.
[0104] The oil pump 20 again features the hollow body 30 with the first opening 31 and the second opening 32. In this embodiment, the first section 51 of the hollow body is completely located within the oil reservoir 4. A key difference from the oil pump 20 shown in Fig. 4 is that the first opening 31 of the hollow body 30 is arranged horizontally within the oil reservoir 4. Consequently, the direction of movement, indicated by the first arrow 6, is also horizontal. This can be advantageous, for example, when limited installation space is available for the oil pump 20 within the reciprocating compressor.
[0105] Fig. 7 shows a fifth exemplary embodiment of the oil pump 20 for the reciprocating compressor.
[0106] The oil pump 20 is essentially the same as the oil pump shown in Fig. 3. To avoid repetition, the differences to the oil pump shown in Fig. 3 will be discussed here.
[0107] In this embodiment, the hollow body 30 extends along the first longitudinal axis 41, and the first opening 31 is arranged on the first longitudinal axis 41 in the oil reservoir 4. The first arrow 6 again serves to illustrate the back-and-forth movement of the hollow body 30. In this embodiment, the back-and-forth movement is essentially in the direction of the first longitudinal axis 41. R. 412007
[0108] - 14 - formed. This means that the first longitudinal axis 41 is not arranged parallel to the back-and-forth movement of the hollow body 30.
[0109] The back-and-forth movement can, for example, deviate by an angle 65 of, say, 45 degrees, or 30 degrees, or 5 degrees from the first longitudinal axis 41.
[0110] Although the present invention has been described with reference to specific embodiments, a person skilled in the art can also implement embodiments that have not been disclosed or have only been partially disclosed, without deviating from the core of the invention.
Claims
R. 412007 - 15 - Claims 1. Reciprocating compressor (10) comprising: a cylinder (11), a piston (15) arranged to be linearly movable within the cylinder (11), an oil circuit (1) for building up an oil film (2) in a gap (5) between an inner wall (12) of the cylinder (11) and an outer wall (16) of the piston (15), an oil pump (20) for pumping oil (3) from an oil reservoir (4) for the oil circuit (1), wherein the oil pump (20) has a hollow body (30) with a first opening (31) and a second opening (32), wherein the first opening (31) is arranged in the oil reservoir (4), wherein a first valve (35) is provided in the hollow body (30) between the first opening (31) and the second opening (32), wherein the first valve (35) allows an inflow of oil (3) into the hollow body (30) and a return flow of oil (3) from the hollow body (30) into the oil reservoir (4) is made more difficult or prevented,wherein the second opening (32) is arranged outside the oil reservoir (4) and is connected to the gap (5), wherein means are provided to generate a reciprocating movement of the hollow body (30), wherein by means of the reciprocating movement of the hollow body (30), oil (3) can be conveyed from the oil reservoir (4) via the first opening (31) through the first valve (35) to the second opening (32) in the gap (5).
2. Reciprocating piston compressor (10) according to claim 1, wherein the first valve (35) of the hollow body (30) is designed as a check valve, in particular as a disc valve or as a ball valve.
3. Reciprocating piston compressor (10) according to claim 1 or 2, R. 412007 - 16 - wherein a second valve (36) is provided between the first valve (35) and the second opening (32) of the hollow body (30), wherein the second valve (36) allows oil to drain from the hollow body (30) via the second opening (32) and makes it difficult or impossible for oil to flow back into the hollow body (30) via the second opening (32), wherein the second valve (36) is in particular designed as a check valve.
4. Reciprocating piston compressor (10) according to one of claims 1 to 3, wherein at least a section of the hollow body (30) extends along a first longitudinal axis (41), wherein the means are provided to generate the reciprocating movement of the hollow body (30) substantially in the direction of the first longitudinal axis (41).
5. Reciprocating piston compressor (10) according to one of claims 1 to 4, wherein the hollow body (30) is coupled to the piston (15), wherein the reciprocating movement of the hollow body (30) can be generated by means of the piston (15).
6. Reciprocating piston compressor (10) according to one of claims 1 to 5, wherein the hollow body (30) is tubular with a first section (51), wherein the first section (51) extends along a first longitudinal axis (41), wherein the first opening (31) is substantially arranged on the first longitudinal axis (41) and is located in a first end region (61) of the hollow body (30).
7. Reciprocating piston compressor (10) according to claim 6, wherein the second opening (32) is arranged substantially on the first longitudinal axis (41) and in a second end region (62) of the tubular hollow body (30).
8. Reciprocating piston compressor (10) according to claim 6, wherein the tubular hollow body (30) has a second section (52), wherein the second section (52) extends along a second longitudinal axis (42), wherein the second longitudinal axis (42) is arranged transversely to the first longitudinal axis (41), wherein the second section (52) is located in a second end region (62) of the R. 412007 - 17 - tubular hollow body (30) is arranged, wherein the second opening (32) is substantially arranged on the second longitudinal axis (42).
9. Reciprocating compressor (1) according to claim 8, wherein the first section (51) has a first cross-section (55), wherein the second section (52) has a second cross-section (56), wherein the first cross-section (55) is larger than the second cross-section (56).