WO2018069020A1

WO2018069020A1 - Overflow valve, in particular for a high-pressure pump, high-pressure pump, and fuel injection system

Info

Publication number: WO2018069020A1
Application number: PCT/EP2017/073993
Authority: WO
Inventors: Muzaffar Fatdachow
Original assignee: Robert Bosch Gmbh
Priority date: 2016-10-10
Filing date: 2017-09-22
Publication date: 2018-04-19
Also published as: DE102016219631A1; CN109844298B; KR20190065362A; CN109844298A

Abstract

The invention relates to an overflow valve, in particular for a high-pressure pump in a fuel injection system, comprising a valve element (1) and a valve piston (3) which is received in an axial bore (2) of the valve element (1) in an axially movable manner and to which the spring force of a spring (5) is applied in the direction of an end-face inflow opening (4), wherein a filter device (6) is mouned upstream of the inflow opening (4). According to the invention, the filter device (6) comprises a plastic housing (7) with at least one integrated filter fabric (8). The invention further relates to a high-pressure pump, in particular for a fuel injection system, comprising such an overflow valve and to a fuel injection system comprising a corresponding high-pressure pump.

Description

Description Title:

Overflow valve, in particular for a high-pressure pump, and high-pressure pump and fuel injection system

The invention relates to an overflow valve for a high pressure pump in a fuel injection system, in particular in a common rail injection system, with the features of the preamble of claim 1. Furthermore, the invention relates to a high pressure pump with such a spill valve. In addition, a fuel injection system is specified with a high-pressure pump according to the invention.

State of the art

Overflow valves of the aforementioned type are used for pressure control or the pressure limitation in the inlet region of a high-pressure pump. If the inlet pressure exceeds a predetermined limit value, the overflow valve opens to supply fuel from the inlet area to a return area.

A known from the prior art spill valve is exemplified in the published patent application DE 10 2013 200 050 AI. It comprises a valve body accommodated in a housing, which is penetrated by an axial bore. In the axial bore, a valve piston is received axially displaceable, so that via an axial displacement of the valve piston, a connection of an end-side inlet opening with a plurality of circumferential Absteueröffnungen can be produced. The displacement of the valve piston takes place counter to the spring force of a spring which loads the valve piston in the direction of the inlet opening. The inlet opening is covered by a multi-part screen or filter, which comprises a filter fabric, an outer basket and a stop plate for the valve piston. The filter fabric is hat-shaped and on the annular outer basket, which in a circumferential groove of the Valve body engages, held on the valve body. Between the filter fabric and the valve body, the stop plate is inserted.

The hat-shaped filter fabric of the filter of the known overflow valve has the disadvantage that it is relatively unstable. When curling, the filter fabric bends inward, resulting in a reduced flow area. In addition, the filter fabric can deform so much that it comes into contact with the valve piston and this damages the filter fabric. Thus the filter loses its function. Due to the multi-part design of the filter this is also expensive to manufacture and assemble.

Based on the above-mentioned prior art, the present invention seeks to provide an overflow valve, in particular for a high-pressure pump, in particular an injection system, with a filter device which respects their stability improved as well as simple and inexpensive to produce.

To solve the problem, the overflow valve is proposed with the features of claim 1. Advantageous developments of the invention can be found in the dependent claims. Furthermore, a high-pressure pump with such an overflow valve and a fuel injection system with a corresponding high-pressure pump are specified.

DISCLOSURE OF THE INVENTION The proposed spill valve comprises a valve body and a valve body

Axial bore of the valve body axially slidably received valve piston which is acted upon in the direction of an end-side inlet opening of the spring force of a spring. The inlet opening is preceded by a filter device, preferably connected to the valve body, which according to the invention comprises a plastic housing with at least one integrated filter fabric.

By integrating the filter fabric in the plastic housing, the filter device can be realized by a single component, so that the assembly of the spill valve is simplified. Furthermore, the plastic housing with integrated film tergewebe are produced inexpensively. This applies in particular if the production takes place by means of injection molding. The filter fabric can then be overmoulded with the plastic of the plastic housing. The plastic housing stabilizes the filter fabric, so that it is less prone to deformation. Furthermore, the filter cloth can be placed in the plastic housing in such a way that it does not come into contact with the valve piston.

Preferably, the plastic housing of the filter device is substantially tubular. The tubular shape gives the plastic housing a high dimensional stability and thus stability. Furthermore, the tubular shape facilitates the connection of the filter device with the valve body of the overflow valve, which preferably also has a circular cross-sectional shape.

Further preferably, the plastic housing has a pipe section with at least one window-like recess extending over a partial circumferential region, in which the filter fabric is inserted. This means that the filter fabric is flowed through substantially from radially outside to radially inside. In this arrangement, it is impossible for the valve piston to come into contact with the filter cloth. This reduces the risk of damage to the filter fabric.

Furthermore, the plastic housing preferably has a pipe section via which it is non-positively and / or positively connected to the valve body. The connection over the pipe section can be realized in a simple manner. For example, the connection may be a plug-in, clamping, pressing, screwing and / or latching connection. The pipe section serving for the connection is preferably an end section of the plastic housing, which is preferably placed on the outside of an end section of the valve body. This means that the plastic housing surrounds the valve body at least in sections. In order to produce a non-positive connection of the plastic housing with the valve body, the end portion of the valve body receiving the pipe section may have an excess pressure in relation to the plastic housing in the area of the pipe section serving for the connection. Furthermore, on the inner circumference side on the plastic housing and / or on the outer circumference of the valve body, geometries can be formed which engage behind one another, so that, alternatively or additionally, a positive locking is effected. For the production of a Positive fit, the plastic housing can also be screwed onto the valve body. For this purpose, the tube portion of the plastic housing serving the connection with an internal thread and the corresponding end portion of the valve body to be provided with an external thread.

In a further development of the invention, it is proposed that the plastic housing has at least one sealing contour arranged on the outer circumference and extending over at least a partial circumference, which is elastically and / or plastically deformable. The deformable sealing contour can be used to seal an inlet region of the high-pressure pump from a return region of the high-pressure pump, so that an additional seal with the aid of a sealing ring can be dispensed with. As a result, the number of components can be further reduced, which has a cost-reducing effect.

According to a preferred embodiment of the invention, the sealing contour is designed as a sealing lip, preferably as a circumferential sealing lip. If the plastic housing is an injection-molded part, the sealing lip can be injection-molded. The outer diameter of the sealing lip is preferably dimensioned such that the sealing lip is elastically and / or plastically deformed when inserting the overflow valve into a housing bore of a high-pressure pump. Hereby, a bias of the sealing lip against the bore wall is achieved, which increases the sealing effect. In order to ensure the deformability of the sealing lip, this may for example have a rounded or wedge-shaped cross-section.

As a further development measure, it is proposed that the sealing contour is designed to be interrupted in the circumferential direction in order to form a bypass flow channel. That is, the inlet area of the high-pressure pump, in which the spill valve is inserted, is connected to the return area via the bypass flow channel. The bypass flow channel can be used as a cooling flow bypass.

It is also proposed that the plastic housing has at least one outer peripheral side flattening, which is preferably arranged in the region of a bypass flow channel and / or forms a bypass flow channel. For example, a flattening to the discontinued region of a sealing contour are adjacent or used to interrupt the sealing contour, so that a usable as a cooling flow bypass bypass flow channel is formed over this.

Alternatively or additionally, the plastic housing may have a radial bore which opens into an axially extending bypass channel of the plastic housing. The cooling flow is then guided within the wall of the plastic housing. In the radial bore and / or in the bypass passage, a throttle point may be formed to regulate the drainage via the bypass passage. The opening into the bypass passage radial bore is preferably arranged in the region of a flattening of the plastic housing, so that it can be flowed in from the outside radially.

An outer peripheral side flattening of the plastic housing may also serve to connect an annular space surrounding the plastic housing with a space which is disposed in front of an end opening of the plastic housing. The front-side opening can replace the inlet via the at least one peripheral window-like recess, if, for example, the filter fabric used therein is melted. In order to prevent particles from being introduced into the overflow valve, a filter fabric is preferably also inserted into the end opening of the plastic housing. This advantageously has a mesh size which is greater than that of the circumferentially arranged filter fabric, so that the permeability to fuel, including the flocculated here paraffins is ensured. For example, the mesh size of the filter cloth 400 arranged on the face side can be 200 μm and that of the filter fabric 200 μm on the periphery can be μηη.

According to a preferred embodiment of the invention, therefore, the filter device has a plastic housing, are integrated in the filter fabric, which have different sizes mesh sizes.

Since the overflow valve according to the invention is preferably used in a high-pressure pump, a high-pressure pump is also proposed for a fuel injection system, in particular for a common-rail injection system, with such an overflow valve. The overflow valve is inserted into a housing bore of the high pressure pump, preferably pressed or screwed. The valve body of the For this purpose, overflow valve preferably has a section which has a press oversize relative to the housing bore or is provided with an external thread.

In addition, a fuel injection system, in particular a common rail injection system, indicated with a high-pressure pump according to the invention. The overflow valve of the invention used in the high pressure pump can be used in this case for pressure control and / or pressure limiting in an inlet region of the high pressure pump. For this purpose, the overflow valve is connected on the one hand to the inlet region, on the other hand to a return region of the fuel injection system.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

1 is a schematic representation of a fuel injection system,

2 shows a schematic longitudinal section through an inventive overflow valve according to a first preferred embodiment, which is screwed into a housing bore of a high pressure pump,

3 shows a schematic longitudinal section through the filter device of the overflow valve of FIG. 2,

4 is a perspective view of the filter device of the overflow valve of FIG. 2,

5 shows a schematic longitudinal section through an inventive overflow valve according to a second preferred embodiment, which is inserted into a housing bore of a high-pressure pump,

6 shows a schematic longitudinal section through the filter device of the overflow valve of FIG. 5, Fig. 7 is a perspective view of the filter device of the overflow valve of Fig. 5 and

8 is a perspective view of a modification of the filter device of FIG. 7.

Detailed description of the drawings

The fuel injection system according to FIG. 1 conveys fuel via a filter 100 from a fuel tank 200 by means of a fuel feed pump 300 via a fuel line 400 to a high-pressure pump 500, which is designed here as a radial piston pump.

The fuel injection system further comprises a metering unit 600 and a high-pressure accumulator 700, which is also referred to as a rail, which in turn is connected to injectors, not shown here, which inject the fuel into the combustion chamber of an internal combustion engine.

The metering unit 600 serves to variably adjust the inflow of fuel from the fuel feed pump 300 to the high-pressure pump 500 as needed. In the supply line from the fuel delivery pump 300 to the metering unit 600, an overflow valve 800 is arranged, which serves to the fuel pump 300 too much subsidized fuel, which can not reach the high-pressure pump 500 at completely or partially closed metering unit 600, and via a return line 900 returned to the fuel tank 200. The fuel delivery pump 300, the metering unit 600, and the spill valve 800 are associated with a low pressure circuit of the fuel injection system. By contrast, the high-pressure pump 500 and the high-pressure accumulator 700 are assigned to a high-pressure circuit.

The overflow valve 800 has an inlet opening 4 formed on the valve body 1 for supplying the fuel delivered by the fuel feed pump 300 and a return channel 24 which is connected to the return line 900. The overflow valve 800 shown in more detail in FIG. 2, which is used here in a housing bore 17 of a high-pressure fuel pump (not shown), serves for pressure regulation or pressure limitation in an inlet region of the high-pressure pump. For this purpose, it has a valve body 1 with an axial bore 2 and a valve piston 3 which can be moved back and forth in the axial bore 2 and is acted upon by the spring force of a spring 5 in the direction of an inlet opening 4. For this purpose, the spring 5 is supported on the one hand on the valve piston 3, on the other hand on a sealing plug 22 pressed into the axial bore 2. About the press-in depth of the sealing plug 22, the spring force of the spring 5 and thus the opening pressure of the overflow valve is adjustable. If an inlet pressure at the valve piston 3, which exceeds the opening pressure, is displaced in the region of the inlet opening 4, the valve piston 3 is displaced counter to the spring force of the spring 5 and establishes a connection of the inlet opening 4 with discharge openings 21 arranged on the circumference. The Absteueröffnungen 21 open into a valve body 1 surrounding the annular space 21 into which a return passage 24 opens, so that the Absteuermenge is a return flow can be fed.

In order to prevent that harmful particles are introduced via the inlet opening 4, the overflow valve of FIG. 2 has a filter device 6 with a substantially tubular plastic housing 7, which is pressed onto an end section of the valve body 1 in the region of the inlet opening 4. About an annular groove 18 which is formed in a pipe section 11 of the plastic housing 7 (see in particular Fig. 2) and in which a circumferential bead 25 of the valve body 1 engages, a positive connection is achieved at the same time.

To the pipe section 11, via which the plastic housing 7 is connected to the valve body 1, a pipe section 9 connects, which has a reduced outer diameter and thus within the housing bore 17 defines a further annular space 26. In the annular space 26 there is inlet pressure. In order to separate the annular space 26 from the annular space 23, in which the return channel 24 opens, are on the outer circumference side of the pipe section 11 of the plastic housing 7 sealing contours 12 in the form of circumferential sealing lips formed (see in particular Fig. 4), which under a radial bias on the wall of the housing bore 17 abut, so that hereby a seal is achieved. The annular space 26 delimiting pipe section 9 of the plastic housing 7 has a plurality of evenly distributed over the circumference arranged, window-like recesses 10, in which a filter fabric 8 is used. The filter fabric 8 is flowed through during operation of the overflow valve from radially outside to radially inside, so that the entry of particles is prevented. The filter fabric 8 is stiffened by the plastic housing 7 so that it is very stable, in particular not prone to deformation. There is also no risk that the filter fabric 8 comes into contact with the valve piston 3. In order to define an end position of the valve piston 3, as shown in FIGS. 2 and 4, a stop plate 20 can be integrated into the plastic housing 7. To reduce the cost can be waived on such a stop plate 20 but also.

However, even with the overflow valve according to the invention, it can not be ruled out that the filter fabric 8 will become clogged due to volatilization. In order to maintain the function of the overflow valve in such a case, the plastic housing 7 of the filter device 6 has an end-side recess 16 into which a filter fabric 8 is likewise inserted (see in particular FIG. 4). The frontally arranged filter fabric 8 has a significantly larger mesh size than the circumferentially arranged filter fabric 8, so that it is less prone to curling and allows a filtered bypass in the direction of the inlet opening 4. To throttle the flow through the bypass, the plastic housing 7 has peripheral flats 13 and end-side grooves 19 (see in particular FIG. 4), which form at least one throttle point within the connection of the annular space 26 with the frontal recess 16 of the plastic housing 7.

FIG. 5 shows a further preferred embodiment of an overflow valve according to the invention. It differs from that of FIG. 2 in particular in that the filter device has no filtered bypass. Furthermore, the plastic housing is merely pressed over the pipe section 11 onto the valve body 1.

Instead of a filtered bypass, however, a bypass channel 15 is provided within the wall of the plastic housing 7 for bypassing the sealing contours 12 and for connecting the annular spaces 23 and 26. The bypass channel 15 is for this purpose via a Radi- Albohrung 14 connected to the annular space 26 and occurs beyond the sealing contours 12 via a recess 27 again from the plastic housing 7 (see in particular Figures 5 and 7). To improve the flowability of the radial bore 14, this is arranged in the region of a circumferential flattening 13. As can be seen in particular from FIG. 6, a stop plate 20 is integrated into the plastic housing 7, but this is not absolutely necessary.

FIG. 8 shows a slightly modified filter device 6 for the overflow valve of FIG. 5. Here, the flattening 13 extends over the entire length of the pipe section 11 of the plastic housing 7, so that the flattening 13 in

Connection with the wall of the housing bore 17 forms a the annular spaces 23 and 26 connecting the bypass channel. An internal bypass channel 15, a radial bore 14 and a recess 27 can therefore be omitted, which has a cost-reducing effect.

Claims

claims

1. Overflow valve, in particular for a high-pressure pump in a fuel injection system, comprising a valve body (1) and in an axial bore (2) of the valve body (1) axially slidably received valve piston (3) in the direction of an end-side inlet opening (4) of the Spring force of a spring (5) is acted upon, wherein the inlet opening (4) is preceded by a filter device (6),

characterized in that the filter device (6) comprises a plastic housing (7) with at least one integrated filter fabric (8).

2. overflow valve according to claim 1,

characterized in that the plastic housing (7) is formed substantially rohrför- mig.

3. Overflow valve according to claim 1 or 2,

characterized in that the plastic housing (7) has a tube section (9) with at least one window-like recess (10) extending over a partial circumferential area, in which the filter cloth (8) is inserted.

4. Overflow valve according to one of the preceding claims,

characterized in that the plastic housing (7) has a pipe section (11) via which it is non-positively and / or positively connected to the valve body (1), wherein preferably the connection is a plug-in, clamping, pressing, screwing and / or latching connection.

5. overflow valve according to one of the preceding claims,

characterized in that the plastic housing (7) has at least one outside circumferentially arranged and at least over a partial circumferential area extending sealing contour (12) which is elastically and / or plastically deformable.

6. overflow valve according to claim 5,

characterized in that the sealing contour (12) is designed as a sealing lip, which is preferably molded and / or has a rounded or wedge-shaped cross-section.

7. overflow valve according to claim 5 or 6,

characterized in that the sealing contour (12) is designed to be interrupted in the circumferential direction to form a bypass flow channel.

8. overflow valve according to one of the preceding claims,

characterized in that the plastic housing (7) has at least one outer circumferential flattening (13), which is preferably arranged in the region of a bypass flow channel and / or forms a bypass flow channel.

9. Overflow valve according to one of the preceding claims,

characterized in that the plastic housing (7) has a radial bore (14) which opens into an axially extending bypass channel (15) of the plastic housing (7), wherein preferably the radial bore (14) in the region of a flattening (13) is arranged.

10. Overflow valve according to one of the preceding claims,

characterized in that in the plastic housing (7) filter fabric (8) are integrated, which have different sized mesh sizes.

11. Overflow valve according to one of the preceding claims,

characterized in that the filter device (6) is connected to the valve body (1).

12. High-pressure pump, in particular for a fuel injection system, in particular a common rail injection system, with an overflow valve according to one of the preceding claims.

13. High-pressure pump according to claim 12,

characterized in that the overflow valve in a housing bore (17) of the high-pressure pump used, preferably pressed or screwed is.

14. Fuel injection system, in particular common rail injection system, with a

Overflow valve (800) according to one of claims 1 to 11.