KR102299585B1 - Piston pump, particularly fuel pump for a fuel system for an internal combustion engine - Google Patents

Abstract

The present invention relates to a piston pump, in particular a fuel pump, of a fuel system for an internal combustion engine, said piston pump defined by an inlet (28), a low pressure region (20) on the inlet side, a piston (32) and said piston (32) and a section of the piston (32) facing away from the working chamber (30) is disposed within the fluid chamber (48), the fluid chamber (48) being at least temporarily in the low pressure region ( 20) and hydraulically connected. According to the invention, at least one first connecting channel 50 downstream of the inlet 28 branches into the low pressure region 20 on the inlet side, and at least one second connecting channel 52 is connected to the branching into the fluid chamber 48 . Further, the fluid chamber 48 is connected to the inlet side low pressure region 20 by at least one third connecting channel 54 .

Description

Piston pumps in fuel systems for internal combustion engines, in particular fuel pumps

The invention relates to a piston pump according to the preamble of claim 1 .

From the market, piston pumps of fuel systems for internal combustion engines are known, in which the piston can be moved axially by means of a drive device formed by a cam or an eccentric disc. The necessary restoring force of the piston is created by a compression spring. Due to operation, the piston pump is partially strongly heated, whereby the properties of the piston pump and/or its durability may be adversely affected.

The object of the present invention is to reduce the wear of the piston seal sealing the piston or the fluid chamber to the outside and the wear of the bush guiding the piston, reduce the hydraulic pressure required at the inlet of the piston pump, reduce the formation of vapor bubbles in the piston pump, , to reduce the undesirable mixing of fuel and oil, especially in the area of the piston seal.

This problem is solved by a piston pump according to claim 1 . Preferred refinements are presented in the dependent claims. Features important to the invention are also shown in the following description and drawings. These features, again, alone and in different combinations, may be important to the present invention, although not explicitly indicated.

The present invention relates to a piston pump, in particular a fuel pump, of a fuel system for an internal combustion engine, said piston pump comprising an inlet, a low pressure region on the inlet side, a piston and a working chamber defined by said piston, said piston pump being distal from said working chamber A section of the facing piston is disposed in a fluid chamber, said fluid chamber being in hydraulic communication with the low pressure region at least temporarily.

The piston may be embodied as a step piston comprising sections with different diameters. Due to this, a diametrical stage is formed, and a section of the piston precisely arranged with a diametrical stage can be arranged in the fluid chamber. Accordingly, the fluid chamber is also referred to as a “step chamber”. The periodic axial piston motion causes a corresponding periodic volume fluctuation in the step chamber, such that fuel is drawn into and discharged from the fluid chamber.

Downstream of the inlet according to the invention at least one first connecting channel branches into the low pressure region on the inlet side and at least one second connecting channel branches into the fluid chamber. Further, the fluid chamber is connected to the low pressure region on the inlet side by means of at least one third connecting channel. Due to this, the temperature in the fluid chamber can be significantly lowered because a portion of the fuel introduced through the inlet can flow through the fluid chamber. According to one embodiment of the piston pump, the flow through the fluid chamber may be a "periodic flow" and thus contain a relatively fluid volume within the piston pump.

The invention has the advantage that in particular the wear of the piston seal (“sealing lip”) which seals the piston or the fluid chamber to the outside (to the drive arrangement of the piston pump) and the wear of the bush guiding the piston can be reduced. Furthermore, by the aforementioned reduction in temperature, the hydraulic pressure required at the inlet of the piston pump (the so-called “primary pressure”) can be reduced without affecting the lubrication required for the operation of the piston. In this case, the risk of so-called "vapor bubble formation" and possible "piston jamming" in the piston pump can be reduced. In particular in the area of the piston seal, undesirable mixing of fuel and oil can be reduced or prevented.

In one embodiment of the piston pump, the first and second connecting channels have at least about the same flow resistance, such that a portion of the incoming fuel flows into the low pressure region on the inlet side and another portion of the incoming fuel flows into the fluid chamber. . The third connecting channel has a hydraulic flow resistance through which fuel is discharged from the fluid chamber through the third connecting channel. Due to this, the flows according to the invention can be implemented simply. Preferably the flow resistances can be adjusted by selection of the cross-section of the respective connecting channel. If the connecting channels are embodied as holes, this can preferably be achieved by designing an appropriate dimension of the hole diameter.

In another embodiment of the piston pump, a hydraulic pressure damper is arranged in the low pressure region on the inlet side. Taking into account the hydraulic resistance caused by the pressure damper, a further advantageous possibility is given for achieving a desired hydraulic flow through the fluid chamber.

The piston pump according to the invention can be simplified if the first and second connecting channels are sections of through-holes communicating with the inlet. This allows the two connecting channels to be manufactured in one working step, thereby reducing costs. In one embodiment of the piston pump, the length through which the inlet passes into the through-hole produced in this way is structurally set such that a predetermined relative flow resistance of the first connecting channel to the second connecting channel is given in advance. Due to this, the two connecting channels can optionally have different lengths and thus different flow resistances, which can affect the amount of fuel flowing through the fluid chamber.

In one embodiment of the piston pump the first and second connecting channels are blind holes leading into the inlet. This allows the first and second connecting channels to be arranged axially offset from each other, thereby giving further structural possibilities and a simple implementation of the piston pump. In particular, the first and second connecting channels can be implemented with different diameters.

Also, the third connection channel may be a through hole. Due to this, the third connecting channel can be manufactured inexpensively because it is particularly simple.

In particular, the piston pump comprises at least a substantially cylindrical housing, wherein the inlet is formed as a radial channel and the connecting channels are formed as axial channels. Due to this, since the structure of the piston pump is simplified, the cost can be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention are described with reference to the drawings.

1 is a longitudinal sectional view of a piston pump of a fuel system for an internal combustion engine;

1 shows an axial cross-sectional view of a high-pressure fuel pump embodied here as a piston pump 10 . The piston pump 10 is a member of a fuel system (not shown) for an internal combustion engine not shown, such as a common rail fuel system. The piston pump 10 is embodied at least partially rotationally symmetric about the longitudinal axis 12 .

The piston pump 10 includes a substantially cylindrical housing 14 , which can be screwed onto an engine block (not shown) of an internal combustion engine by a flange 16 . In the upper region of FIG. 1 the piston pump 10 comprises an inlet-side chambered low pressure region 20 formed between an arcuate cover 18 and an upper and substantially flat end face in the view of the housing 24 . and a hydraulic pressure damper 22 for damping pressure pulsations generated during operation of the piston pump 10 in the low pressure region is disposed.

In the region on the left as viewed in the figure, the piston pump 10 comprises a supply 24 for connection to a low-pressure fuel line (not shown). Here, the supply part 24 is connected with a fluid chamber 26 embodied in a cylindrical shape within the housing 14 , which is called the inlet part 28 and is a channel embodied in a radial direction with respect to the housing 14 . is connected to In one embodiment of the piston pump 10 , a flow control valve for controlling the amount of fuel supplied via the inlet 28 to the region of the fluid chamber 26 at the supply 24 is arranged. However, this is not clearly shown in the drawings.

Furthermore, the piston pump 10 is defined on the one hand by a housing 14 and on the other hand by an upper end section in the view of the piston 32 . The piston 32 is arranged movably in the bush 4 vertically as viewed in the drawing. A section of the piston 32 facing away from the working chamber 30 and comprising a diametrical end is disposed within the fluid chamber 48 , which is at least temporarily in hydraulic connection with the low pressure region 20 .

In the lower region of FIG. 1 the piston pump 10 is also: a spring receiver 36 formed generally in port shape and press-fitted into the housing 14 or otherwise fixedly and fluidly coupled thereto, compression It includes a loaded piston spring 38 , a piston seal 40 , and a spring cup 42 , which is pressed against the lower end section in the view of the piston 32 . As seen in the figure, in the lower section, in particular in the region of the fluid chamber 48 and the piston seal 40 , the piston 32 has a smaller diameter than in the central section, so that the aforementioned diametric stage is formed, and the fluid chamber The hydraulic volume displaced by the piston 32 in 48 depends on the axial position of the piston 32 .

Here, the working chamber 30 is connected to two hydraulic channels 44 and 46 , through which the working chamber 30 is connected on the one hand with the low-pressure region 20 on the inlet side, and on the other On the one hand, it is hydraulically connected with a discharge valve, not shown, of the piston pump 10 .

In addition, the piston pump 10 comprises a first connecting channel 50 , which, as viewed in the drawing, from the downstream to the upper side of the inlet 28 towards the inlet side low pressure region 20 . is branched The piston pump 10 also comprises a second connecting channel 52 , as viewed in the figure, which branches downwards from the downstream of the inlet 28 towards the fluid chamber 48 . The second connection channel 52 is indicated by a broken line border in the drawing.

In addition, the piston pump 10 includes a third connection channel 54 on the right side as seen in the drawing, through which the fluid chamber 48 is connected to the low pressure region 20 on the inlet side to the upper side. The first connecting channel 50 , the second connecting channel 52 and the third connecting channel 54 are each embodied substantially parallel to the longitudinal axis 12 .

Here, the three connecting channels 50 , 52 and 54 are formed as axial channels, which channels are embodied as axial bores in the housing 14 . The first and second connecting channels 50 and 52 are embodied as blind holes leading into the inlet 28 . Alternatively, the first and second connecting channels 50 and 52 may be sections of a through hole leading into the inlet 28 . The third connecting channel 54 is embodied as a through hole in FIG. 1 .

In an unillustrated embodiment of the piston pump 10 , at least one of the connecting channels 50 , 52 and 54 is embodied as a “slanted hole” with respect to the longitudinal axis 12 . In another embodiment, not shown, of the piston pump 10, the housing 14 is formed by a method of metal powder injection molding (MIM) and/or ceramic powder injection molding (CIM). manufactured by The connecting channels 50 , 52 and 54 are formed simultaneously by a casting process. In another embodiment, not shown, of the piston pump 10 , at least one of the connecting channels 50 , 52 and 54 is embodied as an external hydraulic line, said line being, for example, by screwing or welding the piston pump ( 10) are connected.

Here, the first and second connecting channels 50 and 52 have at least about the same flow resistance. This is such that a portion of the fuel introduced through the supply 24 and the inlet 28 flows toward the inlet-side low pressure region 20 and the other portion of the incoming fuel flows toward the fluid chamber 48 . The third connecting channel 54 has a hydraulic flow resistance through which fuel can be discharged from the fluid chamber 48 through the third connecting channel 54 .

During operation of the piston pump 10 , the piston 32 is periodically moved axially in the direction of the longitudinal axis 12 by means of a spring cup 42 via a drive device, not shown. In this case the piston seal 40 is lubricated by the surrounding fuel. Since the piston 32 moves downward as viewed in the drawing during the intake stroke, fuel can flow into the working chamber 30 from the low pressure region 20 on the inlet side. As the piston 32 moves upward as seen in the drawing during the expansion stroke, fuel is delivered from the working chamber 30 in a compressed state through a discharge valve (not shown) into a fuel high pressure accumulator (not shown). .

As a result of the piston movement, the hydraulic volume displaced by the piston 32 within the fluid chamber 48 periodically decreases and increases as described above. A first flow of fuel, indicated by arrow 56 , passes from the supply 24 through the fluid chamber 26 , then through the inlet 28 and then through the first connecting channel 50 of the piston pump 10 . As seen in the drawing, it consists of a low-pressure region 20 on the inlet side in the region of the upper part.

Taking into account the hydraulic resistance caused by the pressure damper 22 , through the second connecting channel 52 - at least as a time averaged - a second flow of fuel indicated by arrow 58 is given. Relatively cold fuel from the supply 24 passes through the fluid chamber 26 , then through the inlet 28 , then through the second connecting channel 52 , then through the fluid chamber 48 and then through the fluid chamber 48 and its It then reaches the low pressure region 20 on the inlet side in the upper region of the piston pump 10 via the third connecting channel 54 . Due to this, the fluid chamber 48 may be cooled.

In particular, by means of the aforementioned second flow of fuel according to arrow 58, the operating temperature of the piston pump 10 can be lowered. Due to this, the formation of vapor bubbles in the piston pump 10 can be prevented even when the hydraulic pressure in the supply part 24 is relatively low. As a result, the lubrication of the piston 32 in the region of the piston seal 40 can be improved.

Depending on the characteristics of the piston pump 10 and in particular the design of the connecting channels 50 , 52 and 54 , the second flow indicated by arrow 58 can be optimized. This is possible, for example, by a structural adjustment of the respective hydraulic cross-section. The structural adjustment of the axial or vertical position of the inlet 28 in relation to the longitudinal axis 12 likewise gives an additional degree of freedom in optimizing the hydraulic flow.

10 piston pump
20 low pressure zone
22 pressure damper
28 inlet
30 working chamber
32 piston
48 fluid chamber
50 first connection channel
52 second connection channel
54 third connection channel

Claims (7)

A piston pump (10) comprising an inlet (28), an inlet side low pressure region (20), a piston (32) and a working chamber (30) defined by the piston (32), the working chamber (30) a section of the piston (32) facing opposite of
Downstream of the inlet 28 , at least one first connecting channel 50 branches into the inlet-side low pressure region 20 , and at least one second connecting channel 52 connects to the fluid chamber 48 . ) is branched into
Piston pump, characterized in that said fluid chamber (48) is connected to said inlet side low pressure region (20) by way of at least one third connecting channel (54). According to claim 1, wherein the first and the second connection channel (50, 52), a portion of the incoming fuel flows into the low pressure region (20) on the inlet side, and the other portion of the incoming fuel flows into the fluid chamber ( 48) having at least about the same flow resistance, wherein the third connecting channel (54) has a hydraulic flow resistance such that fuel is discharged from the fluid chamber (48) through the third connecting channel (54) A piston pump, characterized in that. The piston pump according to claim 1 or 2, characterized in that a hydraulic pressure damper (22) is arranged in the low pressure region (20) on the inlet side. 3. Piston pump according to claim 1 or 2, characterized in that the first and second connecting channels (50, 52) are sections of through-holes communicating with the inlet (28). 3. Piston pump according to claim 1 or 2, characterized in that the first and second connecting channels (50, 52) are blind holes leading into the inlet (28). 3. Piston pump according to claim 1 or 2, characterized in that the third connecting channel (54) is a through hole. 3. The piston pump (10) according to claim 1 or 2, wherein the piston pump (10) comprises at least a substantially cylindrical housing (14), the inlet (28) being formed as a radial channel and the connecting channels (50, A piston pump, characterized in that 52, 54) are formed as axial channels.

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