PISTON COMPRESSOR

Description

[0001] The invention relates to a reciprocating piston engine or compressor for compressing a fluid, in particular ambient air, for a compressed air system of a motor vehicle, comprising a cylinder housing, a piston which can be moved up and down in the piston chamber of the cylinder housing and a cylinder head.

[0002] The cylinder head of such a compressor usually has a valve carrier plate to which a reed valve is attached for each cylinder. This reed valve has areas known as stop ears, whereby one or two stop ears can be provided, each of which has a support surface. In a first position of the reed valve, the reed valve rests flat against the valve carrier plate. During the downward movement of the piston, in which the reed valve is lifted from the valve carrier plate by the suction force in the direction of the downward movement, the reed valve moves to a second position in which the support surfaces strike stop surfaces, thereby limiting the movement.

[0003] The stop surfaces are subjected to impact during each movement to the second position, the open position of the valve, in which a stop lug strikes the stop surface with its support surface. To withstand this load on the stop surfaces, this area must exhibit increased damping properties, compressive strength, and wear resistance. This can be achieved, for example, by manufacturing the cylinder housing from gray cast iron or by using insert bushings with appropriate properties.

[0004] Coatings are also used to improve wear resistance. Another problem with existing designs is the shearing or breaking of the ears. When the components hit each other, a sharp edge forms between the cylinder wall and the stop surface, which then exerts a shearing effect on the reed valve until the ear breaks off. This regularly leads to compressor failure. DE 10 2008 052 744 A1 describes a process by which molded bodies are produced which have a stop surface. The manufacturing process adapts the shape of the stop surface to the deformation of the reed valve. However, the process is very complex. It is also known that the reed valve has a retaining tab on the opposite side of the ears, by means of which the reed valve is clamped or held between the valve carrier plate and the cylinder housing.The exact position of the lamella valve is ensured by two pins.

[0005] Another solution is known from DE 10 2017 109 773 A1, in which an intermediate element with stop surfaces is provided between the cylinder housing and the cylinder head. The intermediate part here is an intermediate plate, which is produced by forming and has a holding surface area and stop surface areas. Tests have shown that this solution is disadvantageous, particularly for compressors with very low oil discharge and relatively large valve openings.

[0006] Document EP 2 708 746 discloses a reciprocating piston compressor comprising a valve plate with reed valves and a sealing plate.

[0007] The document US 4 537 566 shows a valve device with reed valves for a compressor, wherein the reeds rotate over an edge of the compressor housing.

[0008] The object of the invention is to propose an alternative that improves the operating characteristics of the compressor.

[0009] The object is achieved according to the invention by a reciprocating piston engine according to claim 1. Further advantageous features of the embodiment according to the invention can be found in the subclaims.

[0010] A reciprocating piston engine for compressing a fluid, in particular ambient air for a compressed air system of a motor vehicle, is proposed, comprising a cylinder housing with a piston chamber, a piston which can be moved up and down in the piston chamber, and a cylinder head with a valve carrier plate and a reed valve fastened thereto, wherein the reed valve has a support tab and a fixing tab and wherein the reed valve can be moved by means of a spring element in the region of the fixing tabs against a sealing surface on the valve carrier plate.

[0011] To improve the operating characteristics, the invention proposes that a functional element with an impact surface be arranged between the cylinder housing and the valve carrier plate of the cylinder head, the functional element having a thickness of between 3 mm and 10 mm. The design as a separate component with the impact surfaces has the advantage that the functional element is very easily replaceable and / or adaptable to different conditions. Furthermore, additional functions can be easily integrated into the functional element.

[0012] In a preferred embodiment, it can further be provided that a free space with a support surface is provided in the valve carrier plate, which is preferably designed such that the support tab of the lamella valve can be moved into this free space and can be supported on the support surface.

[0013] Furthermore, at least two stop areas, each with a stop surface, can be provided on the functional element. In the open position of the reed valve, in which the reed valve is lifted from the valve support plate, the movement of the reed valve into the piston chamber is limited by the contact with the stop surfaces. The stop surfaces are arranged such that the reed valve rests essentially over its entire surface against the stop surfaces in the maximum open position.

[0014] In the preferred embodiment, the piston chamber has two spatial regions, the first being formed by the cylinder housing and the second by the functional element, with the piston being movable into the second spatial region. This design allows the functional element to have a greater thickness, thus improving both functionality and manufacturability.

[0015] Furthermore, it is proposed that a guide edge be provided on the valve support plate and a support edge be provided on the functional element, with the support tab being movably mounted between these edges. "Movable" is understood to mean that movement of the reed valve, in particular of the support tab, is possible and that length compensation can take place, which occurs when the reed valve deflects when the reed valve moves into the open position.

[0016] The support edge is located between the stop surface and the impact surface on the functional element and the guide edge is located between the support surface and the sealing surface on the valve carrier plate.

[0017] The stop surface is further arranged substantially parallel to the stop surface, with the surfaces having a distance from each other that is 5% to 20% greater than the thickness of the reed valve in the area of ​​the support tab.

[0018] Furthermore, the stop surface and the impact surface are preferably arranged at an angle α between 10° and 20° to the sealing surface.

[0019] In order to keep the impact forces on the impact surface low, the sealing surfaces are arranged parallel to the impact surface, with the surfaces having a distance from each other that is 5% to 20% greater than the thickness of the reed valve in the area of ​​the support tab.

[0020] Preferably, the supporting edge and the guiding edge are designed as rounded edges. The functional element can be made of a plastic material, in particular polyetheretherketone (PEEK). A plastic material significantly reduces wear on reed valves and can be manufactured using an injection molding process. Alternatively, the functional element can be made of a metallic material.

[0021] Furthermore, the functional element can be designed as a ring element or as an intermediate disc. In the ring element design, a functional element adapted to each compression stage of a compressor can be used.

[0022] When designed as an intermediate disc, the functional element can also have fluid channel sections through which a fluid flow can be directed from the cylinder housing to the cylinder head.

[0023] In a preferred embodiment, the functional element can further be provided with sealing contours on both sides, eliminating the need for additional sealing elements to separate the piston chamber and fluid channels. Sealing contours can be beads or contours created by applying a sealant.

[0024] The subject matter of the invention is described below with reference to the figures. The accompanying figures show in detail: Fig.1Exploded view from above of a reciprocating piston engine Fig.2Exploded view from below of the valve carrier plate Fig.3Detailed view of the stop situation of the reed valve Fig.4Detailed view of an impact surface and stop surface

[0025] In Figure 1 and Figure 2 An exploded view is shown in each case, showing the reciprocating piston engine 1 or the compressor from above and below. The compressor shown is a two-stage compressor with a pre-compressor stage and a post-compressor stage.

[0026] The cylinder head 4 is composed of several components, the general structure of which is essentially familiar from the StdT. Only the valve carrier plate 5 and the associated reed valves 6a, b differ from the StdT. Each of the reed valves 6a, b has a support tab 7a, b and a fixing tab 8a, b and is pressed against the valve carrier plate 5 by a spring element 15a, b in the area of ​​the fixing tabs 8a, b, so that the reed valves 6a, b are moved against the valve carrier plate 5 or the sealing surface 21 of the valve carrier plate 5 in the closed position.

[0027] The functional element 11 is shown between the cylinder housing 2 and the cylinder head 4. The functional element 11 is designed here as a plate that, in addition to the recesses for the piston 14, also has fluid channels 22 through which cooling water and / or compressed air is conducted between the cylinder head 4 and the cylinder housing.

[0028] In the top view of the functional element 11, recesses are also shown, which are intended to accommodate the fixing tabs 8a, b and the supporting tabs 7a, b. Figure 1 Centering pins can also be seen by means of which the spring elements 15a, b and the lamella valves 6a, b are held in position, as is also known from the StdT.

[0029] The piston chambers of the two stages are each composed of two chamber areas, with the first chamber areas 3a and 3a' being arranged in the cylinder housing 2, and the second chamber areas 3b and 3b' being arranged in the functional element 11. The pistons 14a and 14b thus move in both chamber areas 3a, b and 3a', b', respectively.

[0030] To seal the piston chambers 3a, b, 3a'b' and the fluid channels 22 from each other, seals, particularly metal bead seals, can be used on both sides of the functional element 11. The thickness of such a seal must be included in the distance between the surfaces. Alternatively, the sealing contours can also be applied or machined directly onto the functional element.

[0031] In Figure 3 A detailed view of the stop position of the reed valve 6a is shown. The valve carrier plate 5 is shown with an intake channel 20, which is closed off from the piston chamber 3a, b by the reed valve 6a. The reed valve is thus in the closed position, in which it is held by the spring element 15a (not shown here). The reed valve 6 rests fully on the sealing surface 21.

[0032] In the area of ​​the support tab 7a, a free space 24a is provided in the valve support plate, in which a support surface 12a is located. The support surface 12a is arranged at an angle α to the sealing surface 21, with the transition area between the surfaces 12a, 21 being formed by the guide edge 16a. The guide edge 16a is preferably rounded. The angle α can be between 10° and 20°.

[0033] The functional element 11 has a recess in the area of ​​the support tab 7a in which the impact surface 10a and the stop surface 9a are arranged. The impact surface 10a is arranged essentially parallel to the sealing surface 21, with the surfaces 10, 21 being spaced apart by 5% to 20% greater than the thickness of the reed valve 6a in the area of ​​the support tab 7a. This relatively small oversize has the effect that the support tab 7a can make a small movement in the stroke direction before it strikes the impact surface 10a when the reed valve 6a is moved into the open position.

[0034] The stop surface 9a is arranged at an angle α to the impact surface 10a or sealing surface 21, with the transition area between the surfaces 10a, 9a being formed by the support edge 17a. The support edge 17a is preferably rounded. The stop surface 9a is arranged substantially parallel to the support surface 12a, with the surfaces 9a, 12a being spaced apart by a distance that is 5% to 20% greater than the thickness of the reed valve 6a in the region of the support tab 7a.

[0035] Due to this geometric arrangement of stop surface 9a and support surface 10a to each other, angle and distance, a guide edge 16a is formed on the valve support plate 5 and a support edge 17a is formed on the functional element 11, between which the support tab 7a is movably mounted.

[0036] The compressor operation sequence is described below for one compressor stage: During the upward movement of the piston 14a, the reed valve 6a is pressed against the sealing surface 21 and thus closes the intake channel 20; during the downward movement of the piston 14a, a suction effect is created, so that ambient air is sucked into the piston chamber 3a, b via the intake channel 20, so that the reed valve 6a is lifted off the sealing surface 21; as soon as the support tab 7a impacts the impact surface 10a and the flow forces of the ambient air on the reed valve 6a continue to increase, the reed valve 6a bends and is supported in the area of ​​the support tab 7a by the support edge 17a; as the deflection of the reed valve 6a increases, the support tab 7a finally hits the support surface 12a with its upper side and the stop surface 9a with its underside.rests against it; As soon as the piston 14a returns to the upward movement, a change in load occurs and the lamella valve 6a is supported in the area of ​​the support tab 7a on the guide edge 16a until the lamella valve 6a rests again with its full surface on the sealing surface.

[0037] The slightly larger distance between support surface 12a and stop surface 10a compared to the thickness of support tab 7a results in support tab 7a being guided between surfaces 9a and 12a. Furthermore, depending on the deflection, the contact surfaces with which support tab 7a rests against one of surfaces 9a, 12a change. Support tab 7a is thus movably mounted between support edge 17a and guide edge 16a and, on the side of fixing tab 8a, is guided by pins 25 and the spring element, restricting its movement.

[0038] Figure 4shows a detailed view of the functional element 11. The impact surface 10a and the stop surface 9a can be seen, which are connected via the support edge 17a.

[0039] The representation as a ring element or even as insertable ring segments is omitted here due to the same function. List of reference symbols

[0040] 1 Reciprocating piston machine 2 Cylinder housing 3a, b Piston chamber 4 Cylinder head 5 Valve support plate 6a, b Blade valve 7a, b Support tab 8a, b Fixing tab 9a, b Stop surface 10a, b Impact surface 11 Functional element 12a, b Support surface 13 Seal 14 a, b Piston 15a, b Spring element 16a, bGuiding edge 17a, bSupporting edge 18a, bStopping areas 19Piston ring 20Intake channel 21Sealing surface 22Fluid channel 23Cooling channel 24Free space 25Pin

Claims

1. Reciprocating-piston machine (1) for compressing a fluid, in particular ambient air, for a compressed air system of a motor vehicle, comprising a cylinder housing (2) having a piston chamber (3a, b, 3a', b'), a piston (14a, b) which can be moved upwards and downwards in the piston chamber (3a, b, 3a', b'), and a cylinder head (4) having a valve carrier plate (5) and a lamellar valve (6a, b) fastened thereon, wherein the lamellar valve (6a, b) has a support tab (7a, b) and a fixing tab (8a, b) and wherein the lamellar valve (6a, b) can be moved against a sealing surface (21) on the valve carrier plate (5) by means of a spring element (15a, b) in the region of the fixing tabs (8a, b), characterized in that a functional element (11) having an impact surface (10a, b) is arranged between the cylinder housing (2) and valve carrier plate (5) of the cylinder head (4), wherein the functional element (11) has a thickness of between 3 mm and 10 mm, and wherein a guide edge (16á, b) is provided on the valve carrier plate (5) and a support edge (17a, b) is provided on the functional element (11), the support tab (7a, b) being movably mounted therebetween.

2. Reciprocating-piston machine (1) according to Claim 1, characterized in that a free space (24a, b) having a support surface (12a, b) is provided in the valve carrier plate (5).

3. Reciprocating-piston machine (1) according to Claim 1, characterized in that at least two stop regions (18a, b), having in each case a stop surface (9a, b), are provided on the functional element (11).

4. Reciprocating-piston machine (1) according to Claim 1, characterized in that the piston chamber (3a, b, 3a', b') has two spatial regions, wherein the first spatial region (3a, 3a') is formed by the cylinder housing (2) and the second spatial region (3b, 3b') is formed by the functional element (11), wherein the piston (14a, b) can be moved into both spatial regions (3a, b, 3a', b).

5. Reciprocating-piston machine (1) according to Claim 1, characterized in that the support edge (17a, b) is arranged between the stop surface (9a, b) and the impact surface (10a, b) on the functional element (11) and the guide edge (16a, b) is arranged between the support surface (12a, b) and the sealing surface (21) on the valve carrier plate.

6. Reciprocating-piston machine (1) according to Claim 1, characterized in that the stop surface (9a, b) is arranged substantially parallel to the support surface (12a, b), wherein the surfaces (9a, b, 12a, b) have a spacing from one another which is 5% to 20% greater than the thickness of the lamellar valve (6a, b) in the region of the support tab (7a, b).

7. Reciprocating-piston machine (1) according to Claim 6, characterized in that the stop surface (9) and the impact surface (10) are arranged at an angle α of between 10° and 20° from the sealing surface (21).

8. Reciprocating-piston machine (1) according to Claim 1, characterized in that the sealing surfaces (21) are arranged parallel to the impact surface (10a, b), wherein the surfaces (12a, b, 21) have a spacing from one another which is 5% to 20% greater than the thickness of the lamellar valve (6) in the region of the support tab (7a, b).

9. Reciprocating-piston machine (1) according to Claim 1, characterized in that the functional element (11) consists of a plastics material.

10. Reciprocating-piston machine (1) according to Claim 2, characterized in that the plastics material is a polyether ether ketone (PEEK).

11. Reciprocating-piston machine (1) according to Claim 1, characterized in that the functional element (11) consists of a metallic material.

12. Reciprocating-piston machine (1) according to Claim 2, characterized in that the functional element (11) is an annular element or an intermediate plate.

13. Reciprocating-piston machine (1) according to Claim 11, characterized in that the functional element (11), which is designed as an intermediate plate, has fluid channel portions (22), a fluid flow being able to be conducted thereby from the cylinder housing (2) to the cylinder head (4).

14. Reciprocating-piston machine (1) according to Claim 9, characterized in that the intermediate plate (11) has sealing contours on both sides.