Piston pump, particularly a high-pressure fuel pump for an internal combustion engine

Abstract

A piston pump, in particular high-pressure fuel pump for an internal combustion engine, includes a pump housing, a pump piston and a conveying chamber defined at least by the pump piston and the pump housing. A seal for sealing the conveying chamber and a separate guide element for guiding the pump piston may be arranged between the pump piston and the pump housing. The seal is designed as a metal sleeve, and may have a radially outwardly projecting web.

Claims

1. A piston pump comprising: a pump housing; a pump piston; a conveying chamber defined by the pump piston and the pump housing; a guide element that guides the pump piston and is arranged between the pump piston and the pump housing; and a seal that seals the conveying chamber and is arranged between the pump piston and the pump housing, wherein the seal is configured as a metal sleeve having a radially outwardly projecting web, and wherein a play is defined between a radially outer edge of the web and a circumferential wall of a recess in which the pump piston is received such that the seal is radially movable relative to the circumferential wall of the recess.

2. The piston pump as claimed in claim 1, further comprising: a fastening ring for the seal arranged between the pump piston and the pump housing.

3. The piston pump as claimed in claim 2, wherein the guide element and the fastening ring are combined into one component.

4. The piston pump as claimed in claim 1, further comprising: a seal carrier; and a second guide element arranged in the seal carrier.

5. The piston pump as claimed in claim 2, further comprising: a spring element arranged between the pump piston and the pump housing, the spring element pressing the seal against the fastening ring.

6. The piston pump as claimed in claim 2, wherein the seal has at least one spring element which is connected to the seal and which presses the seal against the fastening ring.

7. The piston pump as claimed in claim 1, further comprising: an O-ring arranged between an outer lateral surface of the seal and the pump housing.

8. The piston pump as claimed in claim 2, wherein the seal is arranged such that the web rests on the fastening ring.

9. The piston pump as claimed in claim 1, wherein: the fastening ring has an axially projecting collar on which the web lies; and a sleeve portion of the seal and the collar axially overlap one another.

10. The piston pump as claimed in claim 1, wherein the piston pump is a high-pressure fuel pump.

11. The piston pump as claimed in claim 1, wherein the seal is formed of steel.

12. The piston pump as claimed in claim 1, wherein the play is between 0.01 mm and 1 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is explained in greater detail below, wherein identical or functionally identical elements are only provided with one reference number. In the drawing:

(2) FIG. 1 shows a schematic representation of the fuel system with a high-pressure fuel pump in the form of a piston pump;

(3) FIG. 2 shows a partial longitudinal section through the piston pump in FIG. 1;

(4) FIG. 3 shows an enlarged view of a pump piston, a seal, a guide element, a fastening ring, and a spring element of the piston pump from FIG. 1;

(5) FIG. 4 shows the seal from FIG. 3 as an enlarged sectional view;

(6) FIG. 5 shows a partial longitudinal section through an alternative embodiment of the piston pump from FIG. 1;

(7) FIG. 6 shows a partial longitudinal section through a further alternative embodiment of the piston pump from FIG. 1;

(8) FIG. 7 shows the seal of the piston pump from FIG. 1 with connected spring elements in multiple, partially sectional views;

(9) FIG. 8 shows the seal of the piston pump from FIG. 1 with connected spring elements in multiple, partially sectional views as an alternative embodiment;

(10) FIG. 9 shows the seal of the piston pump from FIG. 1 with connected spring elements in multiple partially sectional views as an alternative embodiment; and

(11) FIG. 10 shows the seal of the piston pump from FIG. 1 with connected spring elements in multiple partially sectional views as an alternative embodiment.

DETAILED DESCRIPTION

(12) A fuel system of an internal combustion engine is given the overall reference number 10 in FIG. 1. It comprises a fuel container 12 from which an electric conveying pump 14 conveys fuel to a high-pressure fuel pump configured as a piston pump 16. This further conveys the fuel to a high-pressure fuel rail 18 to which multiple fuel injectors 20 are attached which inject the fuel into combustion chambers of the internal combustion engine which are not shown.

(13) The piston pump 16 comprises an inlet valve 22, an outlet valve 24, and a pump housing 26. A pump piston 28 is received in said pump housing such that it can move back and forth. The pump piston 28 is set in motion by a drive 30, wherein the drive 30 is only depicted schematically in FIG. 1. The drive 30 may be a cam shaft or an eccentric shaft, for example. The inlet valve 22 is configured as a volume control valve through which the amount of fuel conveyed by the piston pump 16 can be set.

(14) The design of the piston pump 16 emerges in greater detail from FIG. 2, wherein only the essential components are mentioned below. The pump piston 28 is configured as a stepped piston with a lower tappet portion 32 in FIG. 2, a guide portion 34 attached thereto, and an upper end portion not depicted in greater detail. The guide portion 34 has a greater diameter than the tappet portion 32 and the end portion.

(15) The end portion and the guide portion 34 of the pump piston 28 delimit along with the pump housing 26 a conveying chamber 38 which is not depicted in greater detail. The pump housing 26 may be configured as a rotationally symmetrical part overall. The pump piston 28 is received in the pump housing 26 in a recess 40 which is present there and which is configured as a stepped bore 42. The bore 42 has multiple steps (three steps 42′, 42″, 42′″; see FIGS. 2 and 3).

(16) Between the guide portion 34 of the pump piston 28 and an inner circumferential wall of the bore 42 (step 42″) is arranged a seal 44. It creates a direct seal between the pump piston 28 and the pump housing 26 and thereby seals the conveying space (high-pressure region) located above the seal 44 in respect of the region (low-pressure region) arranged below the seal 44 in FIG. 2, in which the tappet portion 32 of the pump piston 28, among other things, is located. The seal 44 is configured as a metal sleeve with a radially outwardly projecting web 45. The seal 44 has an L-shaped cross section which has a sleeve portion 43 and the portion (web portion) formed by the web 45.

(17) Between the guide portion 34 of the pump piston 28 and the inner circumferential wall of the bore 42 (step 42′) is arranged a guide element 46 separate from the seal 44. The guide element 46 is arranged axially particularly directly adjacent to the seal 44 and in FIG. 2 above the seal 44 (facing the conveying chamber). The guide element 46 is annular in design (guide ring) and may be fastened to the step 42′.

(18) The piston pump 16 has a further guide element 48 which is arranged in a seal carrier 50 of the piston pump 16 (see FIG. 2). The guide element 46 and the further guide element 48 are used to guide the pump piston 28. The further guide element 48 is annular in design (guide ring) and may be fastened to the seal carrier 50.

(19) The piston pump 16 has a fastening ring 52 for the seal 44 between the guide portion 34 of the pump piston 28 and the inner circumferential wall of the bore 42 (step 42′″). The seal 44 lies on the fastening ring 52, namely such that the web 45 lies on the fastening ring 52. A static sealing point 53 is created by the resting contact surfaces of the seal 44 and fastening ring 52 (see FIG. 3). The seal 44, the guide element 46, the further guide element 48, and the fastening ring 52 form a sealing assembly. The seal 44 may be made of high-grade steel.

(20) The web 45 projecting radially from the seal 44 has a radial play 54 on its radially outer edge in respect of the inner circumferential wall of the recess 40 (step 42″) receiving the pump piston 28 (see FIG. 3). In this way, the seal 44 may be aligned in a radial direction relative to the pump piston 28. A spring element 56 is arranged between the pump piston 28 and the pump housing 26 which presses the seal 44 against the fastening ring 52. The spring element 56 is a helical spring 58 designed as a compression spring. This may rest against the guide element 46 at one end, for example, and against the web 45 of the seal 44 at the other end.

(21) Via the radial gap 60 (guide gap) which can be used as described above as cavitation protection for the seal 44, the pressure 61 prevailing in the conveying chamber 38 reaches the seal 44. At that point, this pressure acts with a force F (arrow 62) on the first front side 64 of the seal 44 (see FIG. 4). In this way, the seal 44 is pressed against the fastening ring 52. In addition, the pressure 61 also acts on the outer lateral surface 66 of the seal 44, so that the seal 44 undergoes deformation 70 on account of the force F acting there (arrow 68). Consequently, a dynamic sealing point is formed between the pump piston 28, in particular between the guide portion 34, and the seal 44 (radially inner ring edge 72). An O-ring 74 may be optionally arranged between the outer lateral surface 66 of the seal 44 and the pump housing 26 (step 42″). The O-ring 74 may lie on the web 45. The O-ring 74 has a radially sealing action and supports the static sealing point 53. The second front side of the seal 44 bears the reference number 65.

(22) FIG. 5 shows an alternative embodiment of the piston pump 16 from FIG. 2. This embodiment largely corresponds to the piston pump 16 described above, wherein identical or functionally identical elements are provided with the same reference numbers.

(23) The fastening ring 52 according to FIG. 5 has an axially (in the axial direction of the pump piston 28) projecting collar 76 which projects into the recess 40. The seal 44 is arranged in such a manner that the web 45 lies on the collar 76. The sleeve portion 43 of the seal and the collar 76 overlap one another axially. The collar 76 is arranged radially between the sleeve portion 43 and the inner circumferential wall of the recess 40 (step 42″). The seal 44 is formed on the sleeve portion and on the web portion 45 with a greater wall thickness. The static sealing point 53 is created between the web 45 and the collar 76. The spring element 56 is configured as a compression spring in the form of a corrugated spring 78.

(24) The radially inner ring edge 72 of the seal 44 has play in respect of the pump piston 28, in particular in respect of the guide portion 34 of the pump piston 28. Consequently, there is no contact between the seal 44 and the pump piston 28 in any operating state of the piston pump 16, since the pressure reaching the dynamic sealing point 82 from the conveying chamber 38 acts on the seal 44 such that said seal undergoes deformation 84 and expands. This means that there is no wear to the seal 44 or the pump piston 28 over the service life.

(25) FIG. 6 shows a further alternative embodiment of the piston pump 16 from FIG. 2. This embodiment largely corresponds to the piston pump 16 described above in relation to FIGS. 1 to 4, wherein identical or functionally identical elements are provided with the same reference numbers.

(26) In the present embodiment, the first guide element 46 and the fastening ring 52 are combined into one component 95 (integral design). The component 95 assumes the guiding and fastening function. The combined component 95 and the seal 44 overlap one another axially (axial direction of the pump piston 28). Hence, an overlapping portion 93 of the combined component 95 is arranged radially between the pump piston 28 (guide portion 34) and the pump housing 26 (circumferential wall 42′ of the bore 42).

(27) The guidance may take place on a lower portion 97 of the component 95. The fastening of the component 95 in the bore 42 may take place in the lower portion 97 or in the overlapping portion 93 of the component 95, for example by means of an interference fit, caulking or a projection 99 protruding radially outwardly from the component 95.

(28) FIGS. 7 to 10 show possible embodiments of the seal 44 in which the seal 44 itself has at least one spring element 56 (integral design). A separate spring element can be dispensed with. In this way, the production and assembly of the piston pump 16 are simplified. A seal 44 of this kind with a spring element 56 configured thereon may be used both in a piston pump 16 according to FIG. 2 and also in a piston pump 16 according to FIG. 5 or

(29) FIG. 6.

(30) FIG. 7 shows a seal 44 which has three spring elements 56 which are configured as spring arms 86. The spring arms 86 extend starting from the web portion 45 of the seal 44. The spring arms 86 each extend from an edge portion 88 projecting beyond the outer edge of the web portion 45. The spring arms 86 in this case have a curved shape in plan view and project axially from the web portion 45 (towards the front side 64 of the seal 44).

(31) The seal 44 according to FIG. 8 likewise has three spring arms 86 which extend from the web portion 45 of the seal 44 axially from the web portion 45. In this case, the spring arms 86 extend from the radially outer edge of the web portion 45. The spring arms 86 each have an arm portion 90 parallel to the sleeve portion 43 of the seal 44 and an angled arm portion 92.

(32) The seal 44 according to FIG. 9 likewise has three spring arms 86 which extend away from the sleeve portion of the seal 44. In this case, the spring arms 86 project away from the first front side 64 of the seal 44 and are angled in respect of the sleeve portion 43.

(33) The embodiment of the seal 44 according to FIG. 10 largely corresponds to the seal 44 shown in FIG. 7. Notwithstanding this, in the seal 44 according to FIG. 9 the spring arms 86 extend from the web portion 45 to the side of the web portion 45 facing away from the sleeve portion 43. The spring arms 86 in this case project beyond the second front side 65 of the seal 44.