WO2023006292A1

WO2023006292A1 - Piston pump, more particularly high-pressure fuel pump

Info

Publication number: WO2023006292A1
Application number: PCT/EP2022/065956
Authority: WO
Inventors: Patrick Hallas; Daniel HEINZINGER
Original assignee: Robert Bosch Gmbh
Priority date: 2021-07-30
Filing date: 2022-06-13
Publication date: 2023-02-02
Also published as: DE102021208296A1

Abstract

The invention relates to a piston pump (10), more particularly a high-pressure fuel pump, comprising: - a pump housing (12); - a pump piston (16), at least part of which is accommodated in a receiving opening (14) in the pump housing (12) and which has a first portion (18) having a larger diameter and a second portion (20) having a smaller diameter; and - a sleeve element (34), which is associated with the pump housing (12) and interacts, at least at times, with a stop surface (48) provided on the pump piston (16). According to the invention, the stop surface (48) is formed on a stop portion (46), at least part of which has a larger outside diameter than the first portion (18) of the pump piston (16).

Description

title

Piston pump, in particular high-pressure fuel pump

State of the art

The invention relates to a piston pump, in particular a high-pressure fuel pump, according to the preamble of claim 1.

High-pressure fuel pumps for fuel systems of internal combustion engines are known from the market. These high-pressure fuel pumps compress the fuel to a high pressure and direct it to a fuel collection line ("rail"), from where the fuel is injected directly into the combustion chambers of the internal combustion engine. A pump piston provided with a step is guided in the pump housing, and the pump piston is acted upon by a piston spring towards a drive, i.e. out of the pump housing. In order to prevent the pump piston from falling out of the pump housing in a preassembled state of the high-pressure fuel pump, in which it is not yet installed in the internal combustion engine, a sleeve element is provided which has a stop section for the pump piston, so that movement of the pump piston in Limited towards the drive and away from the housing and falling out of the pump piston is prevented from the pump housing. DE 102015209539 A1 shows an example of such a high-pressure fuel pump.

Disclosure of Invention

The problem on which the present invention is based is solved by a piston pump having the features of claim 1 . Advantageous developments are specified in the dependent claims. The piston pump according to the invention has the advantage that a pump piston can be realized whose first section has a smaller diameter than before without the risk that the pump piston will be pushed out of the pump housing in a preassembled state (“delivery state”). The sleeve element assigned to the pump housing can thus remain unchanged compared to previous designs. This is achieved by the simple measure that the stop surface on the pump piston, which interacts with the sleeve element in the delivery state mentioned, is no longer (only) formed by the step between the first section and second section, but on a stop section additionally provided according to the invention. Its diameter can be selected independently of the structural and in particular hydraulic requirements for the ratio of the diameters between the first section and the second section of the pump piston.

A desired so-called “stepped piston effect”, which is used to move medium, for example fuel, within the piston pump, can thus be designed as before and as desired. Also, no changes are necessary with regard to the manufacturing process of the pump piston, or such changes can be relatively small, since the additional stop section can be formed later. In particular, machining of the surface of the pump piston, for example by grinding, remains unaffected by the measure according to the invention. After all, only a few changes to the existing assembly process are required.

This is achieved specifically by a piston pump, in particular a high-pressure fuel pump. Such is used, for example, in fuel systems of internal combustion engines with direct fuel injection. In such fuel systems, it serves to compress the fuel to a high pressure and deliver it to a fuel rail, from where the fuel is injected directly into the combustion chambers. The piston pump according to the invention includes a pump housing, which can be designed, for example, as a substantially cylindrical part. There is a receiving opening in the pump housing, which can be designed, for example, as a stepped blind hole. A pump piston is accommodated in this at least in certain areas. A piston bushing, for example, which guides the pump piston and is accommodated in the receiving opening, can serve for this purpose. However, guide bushings that are axially spaced apart from one another and are pressed into the receiving opening are also conceivable. A piston seal can also be arranged in the receiving opening in order to separate a high-pressure area from a low-pressure area.

The pump piston is designed as a stepped piston with a first section with a larger diameter and a second section with a smaller diameter. A step is thus formed between these two sections. The first section with the larger diameter is that section of the pump piston that faces a pumping chamber, while the second section with the smaller diameter is that section of the pump piston that faces a drive, for example a camshaft or an eccentric shaft of the internal combustion engine.

A sleeve element is assigned to the pump housing. This is arranged coaxially to the pump piston. It can be held, for example, on a carrier fastened to the pump housing, so that it is stationary in relation to the pump housing and is “associated with it”. The sleeve element acts at least temporarily, for example in a so-called "delivery state" in which the piston pump is not yet installed in the internal combustion engine, but in which all components of the piston pump are preassembled, with the stop surface present on the pump piston.

This prevents the pump piston from being pushed out of the pump housing by a piston spring which acts on the pump piston in the direction towards the drive. According to the invention, it is proposed that the stop face is formed on a stop section in addition to the step between the first section and the second section, which at least in some areas has a larger outside diameter than the first section of the pump piston. The stop surface and its dimension is thus independent of the diameters of the first section and the second section. The contact surface can be designed as a classic step, as a radius transition or as a chamfer. In this way, the stop surface on the stop section of the pump piston can reliably come into contact with the corresponding stop section of the sleeve element.

In a further development it is provided that the stop section is in one piece with the pump piston. For example, the stop section can be designed as a radially extending, circumferential annular collar that is formed by turning during the manufacture of the pump piston. Such a stop section is particularly stable.

In an alternative development, it is provided that the stop section is formed by a part that is separate from the pump piston. Such a separate part can, for example, have the form of a ring or a sleeve. The advantage of this development is, among other things, that the pump piston can remain unchanged compared to previous embodiments.

In a further development, it is provided that the stop section, which is designed as a separate part, is pressed onto the pump piston or is injection-molded onto it. This creates a reliable hold of the stop section on the pump piston.

In a further development it is provided that the stop section designed as a separate part comprises a metal and/or a plastic material. The advantage of using metal is its high strength and resistance to different media. The advantage of plastic is that it can be sprayed onto the pump piston, for example, at low cost.

In a development, it is provided that the stop section has an annular surface facing away from the stop surface, which is orthogonal, oblique or convexly curved relative to a longitudinal axis of the pump piston when viewed from the outside. An annular surface configured orthogonally to the longitudinal axis is particularly easy to produce. A sloping or convexly curved annular surface has advantages in terms of flow technology. In a further development, it is provided that the piston pump has, on the side of the stop surface facing away from the stop sleeve, a bushing which is assigned to the pump housing and is at least essentially coaxial with the pump piston, the minimum inside diameter of which is smaller than the outside diameter of the stop section, and the bushing on the side facing the stop section Side has an annular recess into which the stop portion can at least partially immerse during operation. In this way, any interference between the stopper portion and the bushing is avoided during the operation of the piston pump.

In a further development it is provided that the shape of the recess is complementary to the shape of the ring surface. In this way it is particularly well avoided that the axial movement of the pump piston is impeded by the stop section. The bushing can be a piston bushing or a clamping ring, for example.

In a further development it is provided that the stop section is arranged or forms the transition from the first section to the second section of the pump piston. This is the overall optimal position for the function of the piston pump.

Embodiments of the invention are explained below with reference to the drawings. In this show:

Figure 1 is a schematic longitudinal section through an area of a

Piston pump with a pump housing, a pump piston, a sleeve member and a stop portion with a stop surface;

FIG. 2 shows an enlarged section II of FIG. 1;

Figure 3 is a view similar to Figure 2 of an alternative embodiment;

FIG. 4 shows a representation similar to FIG. 2 of a further alternative

embodiment; and FIG. 5 shows a representation similar to FIG. 2 of yet another alternative embodiment.

Functionally equivalent elements and areas bear the same reference symbols in different embodiments.

In FIG. 1, a piston pump bears the reference numeral 10 overall. In the present example, it is a question of a high-pressure fuel pump of a fuel system of an internal combustion engine, not shown in any more detail. Such a high-pressure fuel pump serves to compress the fuel to a high pressure and to convey it to a fuel rail, from where the fuel is injected directly into the combustion chambers of the internal combustion engine via injectors.

The piston pump 10 has an overall approximately cylindrical pump housing 12 in or on which the essential components of the piston pump 10 are arranged. Among other things, the piston pump 10 has a non-illustrated controlled inlet valve and an outlet valve. In the pump housing 12 there is a receiving opening 14 which is designed as a stepped blind hole. A cylindrical pump piston 16 is received in the receiving opening 14 .

The pump piston 16 has a first section 18 with a larger diameter and a second section 20 with a smaller diameter. The pump piston 16 is therefore a stepped piston. In FIGS. 1 and 2, above the first section 18, the pump piston 16 and the pump housing 12 delimit a pumping chamber (not shown), which is fluidically connected to the inlet valve and the outlet valve via channels. In the figures, below the second section 20 there is a drive, not shown, which can cause the pump piston 16 to move back and forth parallel to a longitudinal axis 22 during operation. The drive can be, for example, a camshaft or an eccentric shaft of the internal combustion engine.

The pump piston 16 is guided in the pump housing 12 and sealed off from it. This can be done, for example, via a piston bushing, or, as in the present case, via two guide rings and which are spaced apart axially one of these separate high-pressure seal. The upper of the two guide rings and the high-pressure seal are not shown, but they are arranged between the pump piston 16 and the receiving opening 14 . A bushing in the form of a clamping ring 24 is also arranged there, which is pressed into the receiving opening 14 and which serves in particular as a counter bearing for the high-pressure seal. In the present case, the lower of the two guide rings bears the reference number 26 and is arranged in the region of the second section 20 of the pump piston 16 . The guide ring 26 is held by a seal carrier 28 which is welded to a flange 30 of the pump housing 12 .

In Figure 1, the seal carrier 28 carries a low-pressure seal 32 and a sleeve element 34 directly above the lower guide ring 26. Since the sleeve element 34 is rigidly connected to the pump housing 12 via the seal carrier 28, it is “assigned” to the pump housing 12 in this respect. In the present case, the sleeve element 34 has, for example, a first radially outer and approximately cylindrical section 36 which is pressed into the seal carrier 28 . 1, a radial section 38 extends radially inwards towards an outer lateral surface 40 of the second section 20 of the pump piston 16. From a radially inner edge of the radial section 38 extends in FIG a second cylindrical section 42 at the top over a very short distance. This ends at a free and peripheral edge 44. A radial gap is present between the second cylindrical section 42 and the outer lateral surface 40 of the second section 20 of the pump piston 60. The sleeve element 34 can be produced, for example, as a shaped sheet metal part.

In the region of the step between the first section 18 and the second section 20 of the pump piston 16, the pump piston 16 has a stop section 46 in the manner of an annular collar, which extends radially outwards and runs around in the circumferential direction. In the embodiment of FIGS. 1 and 2, the stop section 46 is designed in one piece with the pump piston 16. Has a stop surface 48 pointing downwards to the edge 44 of the sleeve element 34 in the figures and extending essentially orthogonally to the longitudinal axis 22 . In the embodiment shown in FIGS. 1 and 2, an annular surface 50 of the stop section 46 facing away from the stop surface 48 is formed obliquely relative to the longitudinal axis 22 . The clamping ring 24 has, on its axial end face pointing towards the sleeve element 34 and the stop section 46 , a radially inner annular recess 52 , the shape of which is complementary to the stop section 46 and the annular surface 50 .

A so-called “delivery state” of the piston pump 10 is shown in FIG. In this case, the piston pump 10 has not yet been installed in an internal combustion engine, but is in a preassembled state, for example in a warehouse, and is therefore ready for installation in the internal combustion engine. In this preassembled state of delivery, the pump piston 16 is acted upon downwards in the figures by a piston spring (not shown), ie in a direction out of the pump housing 12 .

As a result, the stop surface 48 of the stop section 46 of the pump piston 16 comes into contact with the edge 44 of the sleeve element 34 facing it, as a result of which the pump piston 16 is prevented from falling out of the pump housing 12 . It can be seen from FIG. 1 that the diameter of the edge 44 corresponds approximately to the mean diameter of the annular stop surface 48 . Since the outside diameter of the stop section 46 and thus also the stop surface 48 is larger than the outside diameter of the first section 18 of the pump piston 16, the stop surface 48 also comes into reliable and complete contact with the edge 44 when the pump piston 16 is not viewed in the radial direction is fully coaxial with sleeve member 34 and the diameter of first portion 18 is relatively small.

During operation of the piston pump 10, for example when it is installed in an internal combustion engine, a drive acts on the lower end of the pump piston 16 in the figures, as a result of which the pump piston 16 is pressed in the direction of the pumping chamber, i.e. upwards in the figures. In the "installed position" the stop surface 48 and the edge 44 are spaced apart from one another. To avoid any interference between the stop portion 46 and the clamp ring 24 excluded, the above-mentioned recess 52 is provided, in which the stop section 46 can immerse when the pump piston 16 reaches its top dead center during operation, without the stop section 46 coming into contact with the clamping ring 24 .

In the embodiment of FIG. 3, the annular surface 50 is orthogonal relative to the longitudinal axis 22 and the recess 52 is correspondingly shaped in a complementary manner.

In the embodiment of FIG. 4, the annular surface 50 is convexly curved relative to the longitudinal axis 22 as viewed from the outside, and the recess 52 is correspondingly shaped in a complementary manner.

In the embodiment of FIG. 5, the stop section 46 is designed as a part that is separate from the pump piston 16 . In the present example, it is pressed onto the second section 20 of the pump piston 16 or molded onto it. The stop portion 46 can be made of the same material as the pump piston 16, for example metal. But it can also be made of a plastic material. In the embodiment shown in FIG. 5, the ring surface 50 is orthogonal to the longitudinal axis 22 . It is understood that with others not subscribed

Embodiments, the annular surface can be designed similarly to that shown in FIGS.

Claims

Expectations

1. Piston pump (10), in particular a high-pressure fuel pump, having a pump housing (12), a pump piston (16) accommodated at least in regions in a receiving opening (14) in the pump housing (12) and having a first section (18) with a larger diameter and a second section (20) with a smaller diameter, and a sleeve element (34) assigned to the pump housing (12), which at least temporarily interacts with a stop surface (48) present on the pump piston (16), characterized in that the stop surface (48) is on a Stop section (46) is formed, which has at least partially a larger outer diameter than the first section (18) of the pump piston (16).

2. Piston pump (10) according to claim 1, characterized in that the stop portion (46) is integral with the pump piston (16).

3. Piston pump (10) according to claim 1, characterized in that the stop section (46) is formed by a part separate from the pump piston (16).

4. Piston pump (10) according to claim 3, characterized in that the stop section (46) is pressed onto the pump piston (16) or molded onto it.

5. Piston pump (10) according to at least one of claims 3 or 4, characterized in that the stop section (46) comprises a metal and/or a plastic material.

6. Piston pump (10) according to at least one of the preceding claims, characterized in that the stop portion (46) has one of the stop surface (48) facing away from the annular surface (50) relative to a longitudinal axis (22) of the pump piston (16) is formed orthogonally, obliquely or convexly curved as seen from the outside.

7. Piston pump (10) according to at least one of the preceding claims, characterized in that on the side of the stop section (46) facing away from the sleeve element (34) there is a bushing which is assigned to the pump housing (12) and is at least essentially coaxial with the pump piston (16). (24), the minimum inner diameter of which is smaller than the outer diameter of the stop section (46), and which has an annular recess (52) on the side facing the stop section (46), into which the stop section (46) at least partially dips during operation can.

8. Piston pump (10) according to claims 6 and 7, characterized in that the shape of the recess (52) is complementary to the shape of the annular surface (50).

9. Piston pump (10) according to at least one of the preceding claims, characterized in that the stop section (46) is arranged at the transition from the first section (18) to the second section (20) or forms this.