Piston pump

Abstract

A piston pump (16), in particular a fuel high-pressure pump for an internal combustion engine, comprises a pump housing (26), a pump piston (28) guided in the pump housing (26), and a delivery chamber (38) at least bounded by the pump housing (26) and the pump piston (28), and a seal (43) is arranged between the pump housing (26) and the pump piston (28) for sealing the delivery chamber (38). The seal (43) is configured as a sealing ring (44) and has an inner peripheral surface (57), the sealing ring having a substantially sleeve-shaped base section (45) extending along a central longitudinal axis (41), wherein the sealing ring (44) is configured from a fiber-reinforced plastic by means of injection molding and is machined on the inner peripheral surface (57).

Description

Technical Field

[0001] This invention relates to a piston pump, and more particularly to a high-pressure fuel pump for internal combustion engines. Background Technology

[0002] Several piston pumps are known from the prior art, for example, in internal combustion engines with gasoline direct injection. For example, a piston pump with a plastic ring as a seal is known from WO2019 / 015862A1.

[0003] These plastic rings are typically manufactured using injection molding (Kunststoffspritzen). After injection molding, a so-called "spritzhaut" (injection skin) remains regularly on the component surface and is not removed. Consequently, the dimensional tolerances at the component after injection molding are large relative to machining processes, and the tribological properties of the component surface are also different. Summary of the Invention

[0004] The problem upon which this invention is based is solved by the piston pump of this invention. Advantageous extended configurations of the invention are mentioned in the preferred embodiments.

[0005] The piston pump according to the invention, particularly a high-pressure fuel pump for an internal combustion engine, comprises: a pump housing; a pump piston guided (in the axial direction) within the pump housing; and a delivery chamber at least defined by the pump housing and the pump piston, wherein a seal for sealing the delivery chamber is arranged (radially) between the pump housing and the pump piston, in other words, around the periphery of the pump piston. The seal is constructed as a sealing ring and has an inner circumferential surface (inner peripheral edge surface), the sealing ring having a base section that is substantially sleeve-shaped and extends along a central longitudinal axis. The sealing ring is constructed from fiber-reinforced plastic by injection molding and machined on its inner circumferential surface.

[0006] By machining the inner circumferential surface, the injection-molded skin can be largely or completely removed. Therefore, the tolerance of the sealing ring's inner diameter can be reduced, thereby improving the overall function of the sealing ring or piston pump.

[0007] Various plastics, such as thermoplastics, can be used for the sealing rings. The fibers (reinforcing fibers) can be glass and / or carbon fiber or constructed from glass (GFK) and / or carbon fiber (CFK). The injection molding material used to manufacture the sealing rings can contain both plastic and fibers.

[0008] According to an extended configuration, the sealing ring can be machined on its inner circumferential surface to expose the fibers or fiber segments (reinforcing fibers of fiber-reinforced plastics) adjacent to the inner circumferential surface. Therefore, the degree to which the fibers or fiber segments adjacent to the inner circumferential surface are exposed is determined by the machining of the inner circumferential surface. Thus, a fiber-reinforced component structure exists directly on the inner circumferential surface. Depending on the fiber material, the fibers can contribute to the tribological properties of the surface on the inner circumferential surface of the sealing ring.

[0009] According to an extended configuration, the fiber, i.e., the reinforcing fiber contained in the material of the sealing ring, can be constructed as carbon fiber. Carbon fiber helps reduce friction on the inner circumferential surface due to its excellent lubrication properties. Therefore, frictional losses between the pump piston and the seal can be minimized.

[0010] According to an extended configuration, the inner circumferential surface of the sealing ring can be machined by grinding and / or honing. This allows for suitable mechanical finishing of the inner circumferential surface, thereby removing, for example, approximately 0.02 mm to 0.03 mm of the injection-molded skin surface.

[0011] According to an extended configuration, the fibers can be oriented at least along a large portion of the periphery of the sealing ring in the circumferential direction. In this way, the circumferential strength, swelling properties, and thermal expansion of the sealing ring can be improved. This benefits the reliable function of the sealing ring or plastic ring under the operating conditions. For example, the fibers can be oriented or directed circumferentially, for example, at least 50%, preferably at least 70%, and more preferably at least 90% of the periphery of the sealing ring.

[0012] According to an extended configuration, one or more stems can be constructed on the sealing ring, each stem extending parallel to the central longitudinal axis along the outer circumferential surface of the sealing ring, particularly along its entire length. These one or more stems stabilize the structure of the sealing ring or the structure of the substantially sleeve-shaped base section. Furthermore, the one or more stems can provide an injection inlet (the entrance to the injection material) and, if necessary (in the case of two stems), an injection outlet (the exit of the injection material) (for injection in the circumferential direction). Therefore, these locations are outside the substantially sleeve-shaped base section, thus the stability of the ring is not affected. In the case of two stems, the two stems can be positioned opposite each other on the outer circumferential surface, but slightly offset from each other.

[0013] According to an extended configuration, the sealing ring may have radially outwardly projecting circumferential edges on one axial end or at both axial ends, said circumferential edges being molded onto a substantially sleeve-shaped base section. Thus, with one circumferential edge at one axial end, the sealing ring has a generally L-shaped cross-section, or with one circumferential edge at each of the two axial ends, it has a C-shaped or U-shaped cross-section. These circumferential edges can improve the rigidity of the sealing ring. Furthermore, the sealing ring can be radially centered within the pump housing. This allows the sealing ring to be installed in a fixed position within the pump housing. If the sealing ring has a circumferential edge only at one axial end, that edge can face or face away from the delivery chamber.

[0014] According to an extended configuration, the one or more protrusions and / or the annular edges may each have a (radial) clearance, for example, 0.01 mm to 1 mm, on their radially outer edges relative to the peripheral wall of the slot receiving the pump piston. In other words, the aforementioned elements (the one or more protrusions and / or the annular edges) have an outer dimension, such as an outer diameter, which is slightly smaller than the inner diameter of the slot (hole) receiving these elements at the respective location of the element. This clearance allows the radial position of the element to be adapted to the position of the pump piston. Therefore, a uniform and symmetrical clearance relative to the pump piston can be obtained.

[0015] According to an extended configuration, a spring element, one or more guide elements, a fastening ring, an O-ring, and / or a support ring acting on the sealing ring can be provided on the periphery of the pump piston, or in other words (radially) between the pump housing and the pump piston.

[0016] A spring element can act on the sealing ring, for example, pressing the sealing ring against the retaining ring. The spring element can be axially abutted at one end, for example, against a guide element, and at the other end press the sealing ring against the retaining ring. The spring element can be configured as a compression spring, particularly as a spring washer or a coil spring. The spring element can at least partially surround the pump piston. An axial force is applied to the sealing ring by the spring element, pressing against the axial end face of the sealing ring facing the delivery chamber. This axial force causes the sealing ring to lie flat on the retaining ring, for example, thereby ensuring initial sealing at static sealing locations (e.g., at the sealing location between the sealing ring and the retaining ring).

[0017] The one or more guide elements are used to guide the pump piston axially relative to the housing. The guide elements can be configured, for example, as guide rings. If two guide elements are provided, one guide element can be arranged in the pump housing, for example, in a slot for the pump piston, and the other guide element can be arranged in a seal support.

[0018] The retaining ring can be positioned on the side of the sealing ring away from the conveying chamber. The retaining ring can form a seat for the sealing ring, thereby securing the sealing ring to prevent axial movement, especially away from the conveying chamber.

[0019] O-rings can provide radial sealing. They can supplement static sealing areas and improve sealing performance. O-rings are particularly suitable for placement between the outer circumferential surface of the sealing ring and the pump housing (the peripheral wall of the groove for the pump piston).

[0020] A support ring can be arranged between the outer circumferential surface of the sealing ring and the pump housing (the peripheral wall of the groove for the pump piston), and serves as a support ring for the O-ring. This protects the O-ring from damage, such as extrusion. In particular, the support ring is arranged on the side of the O-ring away from the delivery chamber and can have a triangular profile in cross-section. The hypotenuse of the triangular profile can face the O-ring.

[0021] The present invention also relates to a method for manufacturing a sealing ring for a piston pump, particularly for a piston pump having one or more of the above-described aspects. For advantages, reference can be made to relevant embodiments for piston pumps. The method comprises the following steps: - A preform for injection molding a sealing ring from fiber-reinforced plastic, particularly carbon fiber reinforced plastic (CFK), wherein the sealing ring has a substantially sleeve-shaped base section extending along a central longitudinal axis and has an inner circumferential surface, and - The inner circumferential surface of the sealing ring is machined, especially ground and / or honed, wherein a material layer of a defined thickness is removed.

[0022] The machining or material removal on the inner circumferential surface is particularly carried out in this way, so that the injection-molded skin (left by injection molding) is removed. In particular, a material layer with a thickness of 0.02 mm to 0.03 mm is removed from the inner circumferential surface. As a result, the fibers can be exposed, wherein the tolerance of the inner diameter of the sealing ring is reduced, and the tribological properties of the inner circumferential surface are improved. If the fibers (reinforcing fibers) are composed of carbon fibers, the carbon fibers can help reduce friction with their good lubrication properties.

[0023] The measures described above and / or those described below can be used in further configurations of the method. Attached Figure Description

[0024] The invention will now be described in detail with reference to the accompanying drawings, wherein identical or functionally identical elements are given the same reference numerals, and are given only once if necessary. Figure 1 A schematic diagram of a fuel system with a high-pressure fuel pump in the form of a piston pump is shown. Figure 2 It shows Figure 1 A portion of the longitudinal section of the piston pump; Figure 3 It shows Figure 1 Enlarged view of the pump piston, sealing ring, guide element, and fastening ring of the piston pump; Figure 4 It shows Figure 3 An enlarged cross-sectional view of possible configurations of a sealing ring having an O-ring and a support ring; Figure 5 Shown separately Figure 2 A three-dimensional view of the sealing ring of the piston pump in the image; Figure 6 shows the process before machining the inner circumferential surface ( Figure 6a ) and after cutting ( Figure 6b ) Figure 5 A schematic cross-sectional view of the sealing ring in the middle; and Figure 7 It shows Figure 5 A partial view and magnified view of the inner circumferential surface of the sealing ring. Detailed Implementation

[0025] The fuel system of an internal combustion engine Figure 1 The figure generally includes reference numeral 10. The fuel system includes a fuel tank 12, from which an electrically powered pre-delivery pump 14 delivers fuel to a high-pressure fuel pump configured as a piston pump 16. The high-pressure fuel pump further delivers fuel to a high-pressure fuel rail 18, to which a plurality of fuel injectors 20 are attached, injecting fuel into a combustion chamber (not shown) of an internal combustion engine.

[0026] The piston pump 16 includes an inlet valve 22, an outlet valve 24, and a pump housing 26. A pump piston 28 is received within the pump housing and is capable of reciprocating motion. The pump piston 28 is positioned in motion by a drive mechanism 30, wherein... Figure 1 The drive mechanism 30 is shown only schematically. The drive mechanism 30 may be, for example, a camshaft or an eccentric shaft. The inlet valve 22 is configured as a quantity control valve, for example, through which the amount of fuel delivered by the piston pump 16 can be adjusted.

[0027] exist Figure 2 The structure of the piston pump 16 is shown in more detail below, with only the main components mentioned below. The pump piston 28 is constructed as a stepped piston, which has... Figure 2 The middle section includes a lower push rod section 32, a guide section 34 attached to the push rod section, and an upper end section (not shown further). The guide section 34 has a larger diameter than the push rod section 32 and the end section.

[0028] The end section of the pump piston 28 and the guide section 34, together with the pump housing 26, define a delivery chamber 38 (not shown further). The pump housing 26 may be constructed as a generally rotationally symmetrical part. The pump piston 28 is received in the pump housing 26 in a slot 40 present therein, which is constructed as a stepped bore 42. The bore 42 has multiple steps (three steps 42', 42'', 42'''; see Figure 2 and Figure 3 ).

[0029] A seal 43 is arranged between the guide section 34 of the pump piston 28 and the inner peripheral wall (step 42'') of the bore 42. This seal directly seals between the pump piston 28 and the pump housing 26, and thus isolates the delivery chamber (high-pressure area) located above the seal 43 relative to the... Figure 2 The area (low-pressure area) below the seal 43 is sealed, and the tappet section 32 of the pump piston 28 is located in this low-pressure area.

[0030] The seal 43 is constructed as a sealing ring 44, which has a base section 45 that is substantially sleeve-shaped and extends along the central longitudinal axis 41. The sealing ring 44 has an inner circumferential surface 57 and an outer circumferential surface 58 at the base section 45 (see...). Figure 3 The sealing ring 44 is constructed from fiber-reinforced plastic by injection molding and is machined on the inner circumferential surface 57. The configuration of the sealing ring 44 is further explained below.

[0031] For example, a guide element 46, separate from the sealing ring 44, is arranged between the guide section 34 of the pump piston 28 and the inner peripheral wall (step 42') of the bore 42 (see...). Figure 2 and Figure 3 The guide element 46 may be axially adjacent to the sealing ring 44, and in Figure 2 It is positioned above the sealing ring 44 (facing the conveying chamber). The guide element 46 is constructed as a ring (guide ring) and can be fastened to the step 42'.

[0032] In this example, the piston pump 16 has another guide element 48, which is arranged in the seal support 50 of the piston pump 16 (see...). Figure 2 The guide element 46 and the other guide element 48 are used to guide the pump piston 28. The other guide element 48 is constructed as an annular ring (guide ring) and can be fastened to the sealing bracket 50.

[0033] The piston pump 16 has a retaining ring 52 for the sealing ring 44 between the guide section 34 of the pump piston 28 and the inner peripheral wall (step 42''') of the bore 42. The sealing ring 44 lies flat on the retaining ring 52. A static sealing portion 53 is formed by the flat contact surfaces of the sealing ring 44 and the retaining ring 52 (see...). Figure 3The sealing ring 44, guide element 46, another guide element 48, and fastening ring 52 form a sealing assembly.

[0034] The sealing ring 44 has a radially outwardly projecting, circumferentially constructed annular edge 56 at its first axial end 54 (see...). Figure 3 The annular edge 56 protrudes from the base section 45. The annular edge 56 protrudes radially via the outer peripheral surface 58. The annular edge 56 completely surrounds the sealing ring 44. The annular edge 56 has a radial clearance 64 at its radial outer edge relative to the peripheral wall of the slot 40 (step 42'') of the receiving pump piston 28 (see...). Figure 3 Therefore, the sealing ring 44 can be oriented radially toward the pump piston 28.

[0035] The pressure acting in the delivery chamber 38 can reach the outer peripheral surface 58 of the sealing ring 44, causing the sealing wall on the sleeve-shaped section 45 to undergo radially inward deformation (not shown) due to the force acting there. Therefore, a dynamic sealing area can be formed between the pump piston 28, especially between the guide section 34 and the sealing ring 44 (radially inward annular edge).

[0036] Optionally, a spring element 47 can be arranged between the pump piston 28 and the pump housing 26, which presses the sealing ring 44 against the retaining ring 52. The spring element 47 can be arranged axially between the guide element 46 and the sealing ring 44 of the pump piston 28. The spring element 47 can be constructed as a compression spring in the form of a spring washer or a helical spring. The spring element 47 is axially attached at one end, particularly against the guide element 46, and presses the sealing ring 44 against the retaining ring 52 at the other end.

[0037] Optionally, an O-ring 98 may be arranged between the radial outer circumferential surface 58 of the sealing ring 44 and the pump housing 26 (see...). Figure 4 The O-ring is used to reinforce the static sealing portion 53 and improve the seal. Furthermore, a support ring 99 for the O-ring 98 can be arranged between the radial outer circumferential surface 58 of the sealing ring 44 and the pump housing 26 (see...). Figure 4 The support ring 99 is used to protect the O-ring 98, for example, to prevent the O-ring 98 from being extruded.

[0038] Independently, an axial circumferential edge 76 may optionally be arranged on the sealing ring 44 (see Figure 4 The axial circumferential edge 76 may abut the radial inner circumferential surface 70. This ensures that forces are guided through the sealing ring 44 in an optimized manner and precisely introduced into the static sealing portion 53 (see...). Figure 3 ).

[0039] Below, refer to Figures 5 to 7 Another configuration and manufacturing process of sealing ring 44 are described.

[0040] A protrusion 84 is formed on the sealing ring 44, which in this example extends parallel to the central longitudinal axis 41 of the sealing ring 44 along the outer peripheral surface 58 of the sealing ring 44, specifically along the entire length of the outer peripheral surface 58 (see [link to documentation]). Figure 5 Furthermore, another protrusion 86 is constructed on the sealing ring 44, which extends parallel to the central longitudinal axis 41 of the sealing ring 44 along the outer peripheral surface 58 of the sealing ring 44, specifically along the entire length of the outer peripheral surface 58 (see [link]). Figure 5 As described above, an injection inlet portion can be provided on the protrusion 84, and an injection outlet portion can be provided on another protrusion 86.

[0041] In this example, protrusion 84 and another protrusion 86 transition into the surrounding ring edge 56 (see...). Figure 5 In this example, the distance by which protrusion 84 and another protrusion 86 protrude relative to the outer peripheral surface 58 is the same as the distance by which the ring edge 56 protrudes relative to it. Protrusion 84, another protrusion 86, and ring edge 56 have gaps at their radially outer edges relative to the peripheral wall of the slot 40 of the receiving pump piston 28.

[0042] As previously described, the sealing ring 44 is constructed from fiber-reinforced plastic by injection molding and is machined on its inner circumferential surface 57. In this machining process (characterized by reference numeral 79), a material layer 78 of a defined thickness is removed from the inner circumferential surface 57 of the sealing ring 44 (see figure). Figure 6a After this processing, the fiber 80 or fiber segment (the reinforcing fiber of the fiber-reinforced plastic) adjacent to the inner circumferential surface 57 of the sealing ring 44 is exposed (see...). Figure 7 Due to this cutting process (removal of material layer 78), the inner diameter 84 of the sealing ring 44 is slightly increased (see...). Figure 6b ).

[0043] In this example, fiber 80 is constructed of carbon fiber. The inner circumferential surface 57 can be machined by grinding and / or honing. Fiber 80 is oriented at least along a large portion of the periphery of the sealing ring 44 in the circumferential direction 51 of the sealing ring 44 (see [link to documentation]). Figure 7 ).

[0044] As described above, the method for manufacturing the sealing ring 44 for the piston pump 16 is as follows.

[0045] First, a blank for the sealing ring 44 is injection molded from fiber-reinforced plastic, such that the sealing ring 44 has a base section 45 that is substantially sleeve-shaped and extends along the central longitudinal axis 41, and an inner circumferential surface 57 (see...). Figure 6a ).

[0046] Furthermore, the inner circumferential surface 57 of the sealing ring 44 is machined 79, for example by grinding and / or honing, wherein a material layer 78 of a defined thickness is removed (see...). Figure 6b ).

[0047] As a result, the "injection-molded skin" on the inner circumferential surface 57 is removed and the fiber 80 (in this example, carbon fiber 80) is exposed, and its good lubrication properties help reduce friction on the inner circumferential surface 57 or between the inner circumferential surface 57 and the periphery of the pump piston 28. Furthermore, the machining of the inner circumferential surface 57 reduces the tolerance of the inner diameter 84 of the sealing ring 44 and improves overall functionality.

Claims

1. A piston pump (16) comprising: a pump housing (26); a pump piston (28) guided within the pump housing (26); and a delivery chamber (38) at least defined by the pump housing (26) and the pump piston (28), wherein, A seal (43) for sealing the delivery chamber (38) is arranged between the pump housing (26) and the pump piston (28), wherein the seal (43) is constructed as a sealing ring (44) and has an inner circumferential surface (57), the sealing ring having a base section (45) that is substantially sleeve-shaped and extends along the central longitudinal axis (41), wherein the sealing ring (44) is constructed of fiber-reinforced plastic by means of injection molding and is machined on the inner circumferential surface (57), thereby removing to a large extent or completely the injection-molded skin left in the area of ​​the inner circumferential surface (57) after injection molding.

2. The piston pump (16) according to claim 1, characterized in that, The sealing ring (44) is machined on the inner circumferential surface (57) such that the fiber (80) or fiber segment adjacent to the inner circumferential surface (57) is exposed.

3. The piston pump (16) according to claim 2, characterized in that, The fiber (80) is constructed of carbon fiber.

4. The piston pump (16) according to claim 1 or 2, characterized in that, The inner circumferential surface (57) is machined by grinding and / or honing.

5. The piston pump (16) according to claim 2 or 3, characterized in that, The fiber (80) is oriented at least along most of the periphery of the sealing ring (44) in the circumferential direction (51) of the sealing ring (44).

6. The piston pump (16) according to claim 1 or 2, characterized in that, One or more protrusions (84, 86) are constructed on the sealing ring (44), the protrusions extending parallel to the central longitudinal axis (41) along the outer peripheral surface (58) of the sealing ring (44).

7. The piston pump (16) according to claim 6, characterized in that, The sealing ring (44) has a radially outwardly projecting, circumferentially constructed ring edge (56) on one axial end (54) or on both axial ends respectively, which is molded onto the base section (45) which is substantially sleeve-shaped.

8. The piston pump (16) according to claim 7, characterized in that, The one or more protrusions (84, 86) and / or the ring edge (56) have gaps on their radial outer edges relative to the peripheral wall of the slot (40) receiving the pump piston (28).

9. The piston pump (16) according to claim 1 or 2, characterized in that, The pump piston (28) is provided with a spring element (47) acting on the sealing ring (44), one or more guide elements (46, 48), a fastening ring (52), an O-ring (98) and / or a support ring (99).

10. The piston pump (16) according to claim 1 or 2, characterized in that, The piston pump (16) is a high-pressure fuel pump for an internal combustion engine.

11. The piston pump (16) according to claim 6, characterized in that, The protrusions (84, 86) extend along the entire length of the outer peripheral surface (58), respectively.

12. A method for manufacturing a sealing ring (44) for a piston pump (16), said piston pump being a piston pump (16) according to any one of claims 1 to 11, said method comprising the following steps: - A blank for injection molding the sealing ring (44) from fiber-reinforced plastic, wherein, The sealing ring (44) has a base section (45) that is substantially sleeve-shaped and extends along the central longitudinal axis (41) and has an inner circumferential surface (57). - The inner circumferential surface (57) of the sealing ring (44) is machined, wherein a material layer (78) of a defined thickness is removed.

Images