Radial piston pump, and method for manufacturing a radial piston pump

Description

[0001] The present invention relates to a radial piston pump, in particular a radial piston compressor, according to the preamble of claim 1, and to a method for producing a radial piston pump according to the preamble of claim 16.

[0002] A radial piston pump is a component of fluid technology. In this pump, also referred to as a pump based on the radial piston principle, the piston-working chamber combinations are arranged radially and perpendicular to the drive shaft, unlike an axial piston compressor. The delivery or reciprocating movement of each individual working piston is caused by an eccentric located on the drive shaft. Typically, the radial piston pump comprises several piston-working chamber combinations that extend radially from the drive shaft in a star-shaped pattern. The radial piston pump pumps a fluid from a low-pressure chamber to a high-pressure chamber.

[0003] Radial piston pumps are used, for example, as compressors for coolant in motor vehicle air conditioning systems, especially in electrically powered vehicles. A radial piston pump can also be referred to as a radial piston compressor or refrigerant compressor based on the radial piston principle.

[0004] The valves for the gas exchange process in the radial piston pump described here are arranged as follows. The inlet valves are arranged radially with respect to the rotational axis of the eccentric shaft, i.e., near the head end of the respective piston. The outlet valves, on the other hand, are arranged axially, which offers advantages in terms of installation space and increases design freedom for the inlet valves. For example, a larger valve diameter, greater bending length, possibly multiple inlet valves, etc., can be realized.

[0005] For functional reasons, a minimum wall thickness is required in the cylinder housing, especially between the cover seat and the contact surface of the exhaust valve in the high-pressure channel. Due to the axial arrangement of the exhaust valve plate, an additional "non-compressible volume" is created by the piston movement, the so-called "dead volume / damage volume" across the width of the cylinder housing up to the exhaust valve and thus to the exhaust channel. The dead volume is determined by its cross-sectional area x channel length. The aim is to keep this dead volume as small as possible, as it impairs the compressor's efficiency.

[0006] Due to the design, the exhaust port (the cavity that forms a flow-side connection between the compression chamber and the high-pressure port) is located as high as possible in the cylinder chamber, close to the cylinder head face. The outlet surface of the exhaust port (in the high-pressure chamber) is closed by the exhaust valve plate, which protrudes beyond the outlet surface of the exhaust port (overhang), thus sealing the port axially.

[0007] Since the cover requires an axial contact surface for precise positioning to the cylinder housing, the length of the outlet channel (when forming a flat sealing surface for the AV plate) is increased by the cover projection (radial projection of the cover mounting bore to the cylinder bore), which leads to more dead volume. Figures 1 to 3 for a radial piston compressor according to the state of the art.

[0008] From DE 195 07 295 B4, for example, a radial piston pump has become known, comprising a drive shaft with an eccentric, and at least one piston-working chamber combination, wherein the piston-working chamber combination comprises a cylinder bore and a piston, wherein the cylinder bore has a fluid outlet channel, wherein the cylinder bore is closed with a cover, wherein the cover is received in a cover receiving bore, wherein the cylinder bore has a longitudinal axis and the cover receiving bore has a longitudinal axis.

[0009] Other radial piston pumps are known, for example, from WO 98 / 58171 A1, US 4 975 025 A, US 5 156 531 A and US 6 514 050 B1.

[0010] This is where the present invention comes in and sets itself the task of proposing an improved radial piston pump, in particular a radial piston pump with a smaller dead volume in the exhaust port. In particular, the length of the exhaust port upstream of the exhaust valve is to be reduced, since this volume cannot be compressed as much as the compression / cylinder bore in the cylinder. This volume therefore represents dead volume / defective volume and reduces the efficiency of the compressor.

[0011] According to the invention, this object is achieved by a radial piston pump, in particular a radial piston compressor, with the characterizing features of claim 1. Due to the fact that the longitudinal axis of the cylinder bore and the longitudinal axis of the cover receiving bore are not congruent, in particular are offset parallel, the disadvantages outlined above are overcome, or at least mitigated. In particular, a reduced dead volume results from the shortening of the length of the outlet channel. Nevertheless, a sufficient axial contact surface remains for the cover assembly. Furthermore, a positioning option for securing elements in the cover contact surface is provided, in particular due to the offset of the pre-assembly "cover inlet valve." Furthermore, the use of simple geometric functional elements is enabled, in particular circular bores, simple and reliable sealing, and low costs.

[0012] Further advantageous embodiments of the proposed invention emerge in particular from the features of the subclaims. The subject matter and features of the various claims can, in principle, be combined with one another in any desired way.

[0013] In an advantageous embodiment of the invention, it can be provided that the cover receiving bore is arranged eccentrically to the cylinder bore.

[0014] In a further advantageous embodiment of the invention, it can be provided that the longitudinal axis of the cylinder bore is shifted toward the fluid outlet channel or away from the fluid outlet channel with respect to the longitudinal axis of the cover receiving bore. In this way, the fluid outlet channel can be advantageously shortened and thus the dead volume can be advantageously reduced.

[0015] In a further advantageous embodiment of the invention, a shoulder can be provided between the cylinder bore and the cover receiving bore, which, at least indirectly, forms the support surface for an edge region of the cover. For example, an intake valve, in particular in the form of a spring-loaded valve, can be placed on such a shoulder. The intake valve is then preferably arranged between the cover and the shoulder, so that the cover rests indirectly on this shoulder.

[0016] In a further advantageous embodiment of the invention, it can be provided that the cylinder bore and the cover receiving bore have different diameters, in particular that the cover receiving bore has a larger diameter than the cylinder bore. This can, for example, essentially create a completely circumferential shoulder.

[0017] In a further advantageous embodiment of the invention, it can be provided that the radial piston pump, in particular the piston-working chamber combination, has a fluid inlet channel with an inlet valve and the fluid outlet channel with an outlet valve, wherein the fluid inlet channel is aligned radially to the drive shaft and the fluid outlet channel is aligned axially.

[0018] In a further advantageous embodiment of the invention, the fluid inlet channel can be provided in the cover or the piston. Depending on the arrangement of the fluid inlet channel in the cover or the piston, structural, particularly space-saving, advantages can result.

[0019] In a further advantageous embodiment of the invention, it can be provided that the inlet valve, in particular an inlet valve designed as a spring-loaded valve, rests on the shoulder. The inlet valve can be arranged between the cover and the shoulder and, as will be explained below, can be connected to the cover in advance.

[0020] In a further advantageous embodiment of the invention, the inlet valve can be secured to the cover by means of a securing element, in particular a grooved nail. This ensures convenient assembly and disassembly, as the cover and inlet valve form a single assembly unit.

[0021] In a further advantageous embodiment of the invention, the securing elements can be arranged between the cover and the shoulder. Accordingly, the securing elements are located outside the cylinder bore, and there is fundamentally no risk of the securing elements accidentally entering the piston's working chamber, i.e., the cylinder bore.

[0022] In a further advantageous embodiment of the invention, recesses can be provided in the shoulder for partially accommodating the securing elements, in particular the grooved nails. The securing elements can be partially inserted into these recesses, which represents an additional safety measure to prevent the securing elements from accidentally entering the work area.

[0023] A further object of the present invention is to propose an advantageous and / or improved method for assembling a radial piston pump.

[0024] According to the invention, this object is achieved by a method having the characterizing features of claim 16.

[0025] Further advantageous embodiments of the proposed invention emerge in particular from the features of the subclaims. The subject matter and features of the various claims can, in principle, be combined with one another in any desired way.

[0026] Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying drawings. Fig. 1 shows a radial piston pump in a perspective view; Fig. 2 shows a schematic diagram of a radial piston pump with a radial inlet valve and an axial outlet valve; Fig. 3 shows an enlarged view of a region of a radial piston pump; Fig. 4 shows an enlarged view of a region of a radial piston pump according to the invention; Fig. 5 shows a plan view of a piston-working chamber combination, in particular the cover of a radial piston pump according to the invention; Fig. 6 shows a detail of a radial piston pump according to the invention, in particular grooved nails; Fig. 7 shows an exploded view of the cover, seal, valve and grooved nails of a radial piston pump according to the invention.

[0027] The following reference symbols are used in the figures: LLongitudinal axis FFluid 1Drive shaft 2 (a - e)Piston-working chamber combination 3Pump body 4Housing 5Retaining ring 6Securing element, especially grooved pin 11Eccentric 21Cylinder bore 22Piston 23(a - e)Cover 24Inlet valve 25Exhaust valve 26Seal 27Cover mounting bore 31Heel / contact surface 211Axis of symmetry / longitudinal axis (cylinder bore) 241Fluid inlet channel 251Fluid outlet channel 271Axis of symmetry / longitudinal axis (cover mounting hole) 311Recess for securing element

[0028] Features and details described in connection with a method naturally also apply in connection with the device according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other. Furthermore, a method according to the invention that may be described can be carried out with the device according to the invention.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a" and "an" are intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of the recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0030] First, Fig. 1 to 3 Reference is made.

[0031] A radial piston pump essentially comprises a drive shaft 1 with an eccentric 11, as well as at least one piston-working chamber combination 2. To define the axial direction, a longitudinal axis L of the drive shaft 1 is in the Fig. 1 The combination of drive shaft 1 and eccentric 11 can also be referred to as an eccentric shaft. The eccentric shaft in this case preferably comprises a circular eccentric, with the advantage that a rolling bearing can be slid onto the circular eccentric, reducing contact friction and contact speed (between the circular eccentric and the piston).

[0032] The piston-working chamber combination 2 essentially comprises a cylinder bore 21 and a piston 22. The cylinder bore 21 is closed at the head end with a cover 23. With respect to the drive shaft 1, the cylinder bore 21 and the cover 23 are thus preferably arranged one behind the other in the radial direction.

[0033] The cylinder bore 21 is preferably circularly cylindrical. Accordingly, the cylinder bore 21 has an axis of symmetry or longitudinal axis 211 in the direction of piston movement.

[0034] Typically, the radial piston pump comprises at least two piston-working chamber combinations 2, 2a, 2b, ..., which extend radially from the drive shaft 1. Preferably, the radial piston pump comprises at least three, preferably six, piston-working chamber combinations 2, 2a, 2b, ..., which extend in a corresponding star shape from the drive shaft 1. Accordingly, each cylinder bore 21 of the piston-working chamber combinations 2, 2a, 2b, ... is provided with a cover 23, 23a, ...

[0035] Preferably, the cylinder bore(s) 21 are received or formed by a pump base body 3. Accordingly, the pump base body 3 is preferably a cast part. The pump base body 3, in turn, can be at least partially enclosed by a housing 4.

[0036] The cover(s) 23, 23a, ... are fixed here, for example, by means of a retaining ring 5 on the pump base body 3 or above the cylinder bore(s) 21. In principle, however, any other suitable fastening method, such as screwing or a housing-integrated retaining ring, is also possible. The housing 4 engages over the retaining ring 5.

[0037] Furthermore, a fluid inlet channel 241 is provided in the cover 23 or on the head side of the cylinder bore 21. The fluid inlet channel 241 is equipped with an inlet valve 24, which can selectively close or open the fluid inlet channel 241. The fluid inlet channel 241 can also be provided, for example, in the piston 22. The fluid inlet channel 241 is preferably arranged radially.

[0038] The cover 23 is preferably circular in shape. The cover 23 is received in a corresponding, preferably also circular, cylindrical cover receiving bore 27 provided for this purpose. The cover receiving bore 27 is preferably provided in the pump base body 3. The cover receiving bore 27 accordingly has an axis of symmetry or longitudinal axis 271. In view of the manufacturing costs and the functional requirement of the tightness of the cover 23 to the cylinder bore 21 or to the pump base body 3, a circular shape is preferable for the geometry of the cover 23 and the cover receiving bore 27.

[0039] The cover receiving bore 27 for the cover 23 preferably has a larger diameter than the cylinder bore 21, so that a shoulder 31 is formed between the two bores. This shoulder serves, at least indirectly, as a support surface 31 for the cover 23. It is particularly provided that an inlet valve 24, preferably designed as a spring-loaded valve, initially rests on the shoulder 31, and the cover 23 with the fluid inlet channel then rests on the spring-loaded valve 24.

[0040] A fluid outlet channel 25 is also provided in the cylinder bore 21, preferably in the wall of the cylinder bore 21. The fluid outlet channel 251 is equipped with an outlet valve 25, which can selectively close or open the fluid outlet channel 251. The fluid outlet channel 251 is preferably arranged axially.

[0041] For example, in Fig. 2As shown, the fluid F to be compressed flows via the fluid inlet channel 241 or the inlet valve 24 into the cylinder bore 21, is compressed there by the stroke movement of the piston 22, and leaves the cylinder bore 21 through the outlet valve 25 or the fluid outlet channel 251. The design of the valves, for example as a spring-loaded valve, is well known to those skilled in the art and requires no further explanation here. Various design options or variations, in particular the number, of inlet / outlet valves are also conceivable, especially per piston-working chamber combination 2.

[0042] According to the invention, it is provided that the longitudinal axis 211 of the cylinder bore 21 and the longitudinal axis 271 of the cover receiving bore 27 are not congruent. In other words, it is preferably provided that the longitudinal axis 271 of the cover receiving bore 27 is displaced parallel to the longitudinal axis 211 of the cylinder bore 21 or that the cover receiving bore 27 is arranged eccentrically to the cylinder bore 21. Such an arrangement is shown, for example, in the Fig. 4 and 5 Here, it is also evident that the cover 23 is also displaced parallel or eccentrically to the cylinder bore 21 and thus ultimately to the piston 22.

[0043] For this purpose, it is preferably provided that the longitudinal axis 211 of the cylinder bore 21 is displaced with respect to the longitudinal axis 271 of the cover receiving bore 27 in the direction of or opposite to the direction of the fluid outlet channel 251. As a result, the fluid outlet channel 251 can be adapted, in particular shortened, as can be determined in particular by comparing the Fig. 3 and 4 can be seen. In principle, it is shown that the support on the side facing away from the HP port is larger, thus the cover is shifted away from the HP area. Furthermore, the relative displacement of the intake area in the cover relative to the cylinder is shown. The version "away from the HP area" is preferred.

[0044] Although the figures show an axial displacement (eccentricity) of the cover 23 relative to the cylinder bore 21, a displacement of the longitudinal axis 271 of the cover receiving bore 27 in a direction offset by 90° to the above-mentioned direction or a direction in between is also conceivable, for example also into or out of the plane of the drawing.

[0045] The Fig. 4 also shows a section of a radial piston compressor with axially aligned outlet channel 251. The position of piston 1 is shown in the partial stroke.

[0046] Further details of the present invention will become apparent from a description of an advantageous assembly of the radial piston pump, in particular the combination of cover 23 and inlet valve 24.

[0047] The "cover assembly" is preferably mounted on the pump body 3 in an "overhead" assembly for the inlet valve 24. Therefore, it is advantageous if the inlet valve 24 is secured to the cover 23 in a pre-assembly step to prevent it from becoming lost. For this purpose, at least one securing element—referred to below as grooved nails 6—can be provided, which should be arranged in such a way that loosening during operation either cannot occur or does not negatively affect the function of the radial piston pump.

[0048] For this purpose, the securing elements 6 are arranged between the cover and the shoulder. This prevents the securing elements, in particular the grooved nails, from entering the cylinder bore 21 in the event of loosening. Preferably, at least one recess 311 is provided in the shoulder 31 for this purpose, into which the securing elements 6, in particular the grooved nails or their heads, can be inserted.

[0049] With regard to a preferred assembly method, the assembly of a radial piston pump comprising an inlet valve, preferably a spring plate valve, and a cover 23 with a fluid inlet channel 241, as well as a shoulder 31 provided between the cylinder bore 21 and the cover receiving bore 27, is preferably as follows. Placing the inlet valve 24 on the cover 23; fixing the inlet valve 24 on the cover 23 by means of at least one securing element 6, preferably by means of a grooved nail; placing the cover 23 with the valve side on the shoulder 31, wherein the securing elements 6 are arranged between the cover 23 and the shoulder 31; fixing the cover 23 in the cover receiving bore 27.

[0050] Preferably, the assembly method may also include mounting the seal 26 to the cover (O-ring).

[0051] Preferably, it can be provided here that the securing elements, in particular the grooved nails, are accommodated in sections in recesses 311 of the paragraph 31.

[0052] The radial piston pump proposed here can preferably be used as an air conditioning compressor or refrigerant compressor, preferably driven by an electric motor. Accordingly, the fluid is preferably a refrigerant.

Claims

1. Radial piston pump, in particular radial piston compressor, comprising - a drive shaft (1) with an eccentric (11), and at least one piston-working space combination (2), wherein the piston-working space combination (2) comprises a cylinder bore (21) and a piston (22), wherein - the cylinder bore (21) has a fluid outlet channel (251), - the cylinder bore (21) is closed with a cover (23), wherein - the cover (23) is received in a cover receiving bore (27), - the cylinder bore (21) has a longitudinal axis (211) and the cover receiving bore (27) has a longitudinal axis (271), characterised in that the longitudinal axis (211) of the cylinder bore (21) and the longitudinal axis (271) of the cover receiving bore (27) are not congruent.

2. Radial piston pump according to claim 1 or the preamble of claim 1, characterised in that the cover receiving bore (27) is arranged eccentrically to the cylinder bore (21).

3. Radial piston pump according to at least one of the preceding claims, characterised in that the longitudinal axis (211) of the cylinder bore (21) and the longitudinal axis (271) of the cover receiving bore (27) are shifted parallel to each other.

4. Radial piston pump according to at least one of the preceding claims, characterised in that the longitudinal axis (211) of the cylinder bore (21) is displaced relative to the longitudinal axis (271) of the cover mounting bore (27) in the direction of the fluid outlet channel (251) or away from the fluid outlet channel (251).

5. Radial piston pump according to at least one of the preceding claims, characterised in that a shoulder (31) is provided between the cylinder bore (21) and the cover receiving bore (27), which, at least indirectly, forms the support surface for an edge area of the cover (23).

6. Radial piston pump according to at least one of the preceding claims, characterised in that the cylinder bore (21) and the cover receiving bore (27) have different diameters.

7. Radial piston pump according to claim 6, characterised in that the cover mounting bore (27) has a larger diameter than the cylinder bore (21).

8. Radial piston pump according to at least one of the preceding claims, characterised in that the piston working space combination (2) has a fluid inlet channel (241) with an inlet valve (24) and the fluid outlet channel (251) with an outlet valve (25).

9. Radial piston pump according to claim 8, characterised in that the fluid inlet channel (241) is aligned radially to the drive shaft and the fluid outlet channel (251) is aligned axially.

10. Radial piston pump according to at least one of the preceding claims 8 or 9, characterised in that the fluid inlet channel (241) is provided in the cover (23) or the piston (22).

11. Radial piston pump according to at least one of the preceding claims 8 to 10, characterised in that the inlet valve, designed as a spring plate valve, rests on the shoulder (31).

12. Radial piston pump according to at least one of the preceding claims 8 to 11, characterised in that the inlet valve (24) is fastened to the cover (23) by means of at least one securing element (6).

13. Radial piston pump according to claim 12, characterised in that the securing element is a grooved nail.

14. Radial piston pump according to claim 12, when dependent on claim 5, or according to claim 13, characterised in that the at least one securing element (6) is arranged between the cover (23) and the shoulder (31).

15. Radial piston pump according to claim 12, when dependent on claim 5, or according to claim 13 or 14, characterised in that at least one recess (311) is provided in the shoulder (31) for partially accommodating the at least one securing element (6) in the shoulder (31).

16. Method for assembling a radial piston pump according to at least one of the preceding claims, comprising an inlet valve (24), preferably a spring plate valve, and a cover (23) with a fluid inlet channel (241), and a step (31) provided between the cylinder bore (21) and the cover receiving bore (27), characterised by the following method steps: - Placing the inlet valve (24) on the cover (23); - Fixing the inlet valve (24) to the cover (23) by means of at least one securing element (6), preferably by means of a notched nail; - Placing the cover (23) with the valve side on the shoulder (31), whereby the at least one securing element (6) is arranged between the cover (23) and the shoulder (31); - Fixing the cover (23) in the cover mounting hole (27).

17. Method for assembling a radial piston pump according to claim 16, characterised in that the at least one securing element (6) is received in sections in at least one recess (311) of the shoulder (31).