DE102013200455A1 - Piston pump e.g. fuel pump for fuel system of internal combustion engine, has fluid space connected to low-pressure region through communicating passages having openings towards non-return valves in fluid space and low-pressure region - Google Patents

Abstract

The piston pump (24) has an inlet-side low-pressure region, a piston (46) and a workspace (25) bounded by the piston. The piston is arranged in a fluid space facing away from the workspace. The fluid space is temporarily connected to the low-pressure region through the communicating passages. The communicating passages are provided with openings towards the non-return valves in the fluid space and low-pressure region.

Description

State of the art

The invention relates to a piston pump according to the preamble of claim 1. Fuel pumps, in particular high-pressure fuel pumps, for the direct injection of a gasoline fuel or diesel fuel in cylinders of internal combustion engines, are known from the market. Often such fuel pumps are designed as a piston pump with a cylinder. During operation of the fuel pump, this is generally exposed to high thermal loads, which may possibly heat the fuel, which can lead to undesirable vapor bubble formation.

A patent publication in this field is, for example, the DE 10 2004 063 075 A1 ,

Disclosure of the invention

The problem underlying the invention is achieved by a piston pump according to claim 1. Advantageous developments are specified in subclaims. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features, both alone and in different combinations, can be important for the invention, without being explicitly referred to again.

The invention has the advantage that a fluid space (also called "step space", since the step-shaped shoulder of the piston is arranged there) of a fuel piston pump can be selectively flowed through by comparatively cool fuel. Thereby, a temperature of the piston pump - especially in the step room - lowered and reduced vapor bubble formation or even prevented. Furthermore, because of the lowered temperature and because of the lower risk of vapor bubbles, the piston pump can be operated with a lower prefeed pressure, as a result of which a prefeed pump with a smaller power can optionally be used. This can reduce fuel consumption and fuel system costs.

The invention relates to a piston pump, in particular a fuel pump for a fuel system for an internal combustion engine, with an inlet-side low-pressure region, a piston, a working space which is bounded by the piston, wherein the piston has a paragraph facing away from the working space in a fluid space (" Step space ") is arranged, and wherein the fluid space is at least temporarily connected via at least one connecting channel with the low-pressure region. According to the invention, there are at least two connecting channels, wherein in the one connecting channel a first check valve opening towards the fluid chamber and in the other connecting channel a second check valve opening towards the low pressure region are arranged. The connection channels and the check valves allow "fresh" and thus cool fuel to be sucked from the low pressure area via the one connecting channel into the step room and pumped back into the low pressure area via the other connecting channel. As a result, a directed flow is generated in the step room, so that there is effectively cooled by the cool fuel. A piston seal, which limits the step room, is thereby kept cool. According to the invention, therefore, the piston pump can be cooled at least partially in a special way. Thereby, the fatigue strength of the piston pump can be increased and the operation can be improved.

An embodiment of the invention provides that the check valve is a beak-slit valve or a diaphragm valve or a mushroom valve or a ball-cone valve. As a result, particularly suitable embodiments of the check valves are described for the piston pump, since these can be manufactured and assembled cost-effectively, switch quickly, build small and work reliably, whereby the total cost of the piston pump can be reduced.

In particular, the connection channels and the check valves are designed and arranged such that on average there is a directed flow through the fluid space with fuel. This allows a particularly effective cooling of the piston pump. The fuel is thus not alternately moved in two possible directions of flow through the connecting channels or through the fluid space, but flows substantially in one direction, so that once heated fuel is not used again for cooling.

In a further embodiment of the invention, it is provided that the piston pump has a Teflon seal, by means of which a fuel area in the piston pump is sealed against an oil area in a cylinder head. Thereby, a required for the operation of the piston pump tightness can be improved. Although a friction generated by the Teflon seal increases the thermal load of the piston pump, but the thermal load can be significantly reduced by the cooling effect of the invention.

The piston pump is easier to build if at least one connecting channel is arranged in a housing of the piston pump. This will be a external hydraulic connection dispensable, which costs can be reduced.

In a further embodiment of the piston pump is provided that the connecting channels are designed substantially straight and parallel to a longitudinal axis of the piston. As a result, a hydraulically particularly suitable arrangement is described, whereby the effect of the cooling is improved. In addition, such channels are easily introduced by drilling into the housing, which is inexpensive.

Furthermore, it can be provided that the first check valve is arranged at an end portion of the one connecting channel facing the low-pressure region, and that the second check valve is arranged at an end portion of the other connecting channel facing the fluid space. As a result, the manufacture and assembly of the piston pump are simplified, for example, when the check valves are designed as a beak valve. As a result, the manufacturing costs can be additionally reduced.

Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show:

1 a fuel system for an internal combustion engine;

2 a piston pump of the fuel system of 1 ;

3 a first alternative embodiment of a check valve for the piston pump in a closed state;

4 the embodiment of the check valve of 3 in an open state;

5 a second alternative embodiment of the check valve in a closed state; and

6 the embodiment of the check valve of 5 in an open state.

The same reference numerals are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

1 shows a fuel system 10 for a (not shown) internal combustion engine in a much simplified representation. From a fuel tank 12 will fuel through a suction line 14 , by means of a pre-feed pump 16 , via a low pressure line 18 , and about one of an electromagnetic actuator 20 actuatable quantity control valve 22 a high-pressure fuel pump - hereinafter as a piston pump 24 designated - supplied. Downstream of the quantity control valve 22 is a workroom 25 the piston pump 24 via an outlet valve, not shown, and a high-pressure line 26 to a high-pressure accumulator 28 ("Rail") connected.

Other elements, such as other valves of the piston pump 24 , are in the 1 not drawn. The electromagnetic actuator 20 is controlled by a control and / or regulating device 30 driven.

It is understood that the quantity control valve 22 also as a unit with the piston pump 24 can be trained. For example, the quantity control valve 22 a forced openable inlet valve of the piston pump 24 be.

When operating the fuel system 10 promotes the pre-feed pump 16 Fuel from the fuel tank 12 in the low pressure line 18 , The quantity control valve controls 22 the workroom 25 the piston pump 24 amount of fuel supplied. The piston pump 24 also has pistons 46 on top of the workroom 25 limited. The quantity control valve 22 can be closed and opened depending on a particular need for fuel. The fuel is for example gasoline or diesel fuel.

2 shows the piston pump 24 of the fuel system 10 in an axial sectional view. The piston pump 24 is at least partially about a longitudinal axis 32 arranged rotationally symmetrical.

The piston pump 24 includes a housing 34 , which by means of a flange 36 on a - not shown - engine block of an internal combustion engine can be screwed. In an upper area in the drawing, the piston pump comprises 24 a front-side housing portion 38 ("Cover"), as well as an inlet 40 for connection to the low-pressure line 18 , In the housing section 38 is designed as a diaphragm damper pressure damper 42 arranged, which hydraulically between the inlet 40 and one of the housing portion 38 included low pressure area 44 is arranged.

In a mid-range in the drawing, the piston pump comprises 24 the essentially cylindrical working space 25 whose longitudinal axis in this case the longitudinal axis 32 is equal to. The workroom 25 is through a hydraulic channel 45 and an unillustrated outlet valve with the high pressure line 26 hydraulically connected, the hydraulic channel 45 in the drawing of 2 is visible in cross section.

In the workroom 25 is the piston 46 arranged vertically displaceable in the drawing. The piston 46 is in a liner 48 guided radially. At a lower stepped in the drawing section of the piston 46 is a radial circumferential Teflon seal 50 arranged, which between the fuel in the piston pump 24 and an oil in a cylinder head seals.

The housing 34 has in the illustrated sectional view a first and a second connection channel 52 and 54 which are present as holes in the housing 34 are executed. The connection channels 52 and 54 can be the low pressure area 44 with a step room 56 ("Fluid space") of the piston pump 24 connect hydraulically and are substantially straight and parallel to the longitudinal axis 32 executed. The step room 56 is below the case 34 arranged and is among other things of a cup-shaped spring receptacle 57 limited by the piston 46 is also penetrated. In this step room 56 is one from the workroom 25 pointing away paragraph (diameter step) of the piston 46 , The heel reduces a comparatively large diameter of the piston 46 to a comparatively small diameter in the lower part of the drawing.

Furthermore, at one to the low pressure area 44 facing end portion of the first connection channel 52 a first check valve 58 arranged, and at one to the step room 56 pointing end portion of the second connection channel 54 is a second check valve 60 arranged. The first check valve 58 can go to the step room 56 open, and the second check valve 60 can go to the low pressure area 44 open. In the present case are the check valves 58 and 60 designed as beak-slit valves. arrows 62 and 64 indicate a respective flow direction.

At the bottom of the drawing in the drawing 34 is, as already mentioned above, the approximately cup-shaped spring receptacle 57 arranged, which has an upper end portion of a coil spring in the drawing 68 receives. The coil spring 68 is in the direction of the longitudinal axis 32 compressible. A lower end portion of the coil spring 68 is on a spring plate 70 struck, which with a lower end in the drawing of the piston 46 is compressed.

Below the spring plate 70 a roller tappet and a running on a tread of a cam roller are arranged, which in the 2 but not shown. Other for the operation of the piston pump 24 required elements, such as other hydraulic connections, valves or valve elements are in the sectional view of 2 also not shown or not visible.

In a suction phase of the piston pump 24 becomes the piston 46 at a corresponding cam position by means of the force of the coil spring 68 in the drawing of 2 moved down. The free volume of the working space 25 is increased, with fuel over the inlet 40 in the workroom 25 can flow.

In a funding phase of the piston pump 24 becomes the spring plate 70 and thus the piston 46 moved by the force of the cam in the drawing upwards. The free volume of the working space 25 is downsized, taking fuel out of the workspace 25 in the high pressure line 26 is encouraged. The piston pump 24 operates essentially periodically in response to the movement of the cam.

During the downward movement (suction phase) of the piston 46 becomes a volume of the step room 56 - thanks to the diameter step of the piston 46 - reduced. This can during operation of the piston pump 24 heated fuel from the step room 56 through the second check valve 60 and the second connection channel 54 in the relatively cool low pressure range 44 be pressed.

During the upward movement (production phase) of the piston 46 becomes the volume of the step room 56 increased. This results in the step room 56 a relative negative pressure, resulting in comparatively cool fuel from the low pressure range 44 through the first check valve 58 and the first connection channel 52 in the step room 56 can flow. This will be the step room 56 or the step room 56 surrounding sections of the piston pump 24 cooled.

In the present case are the connection channels 52 and 54 and the check valves 58 and 60 on both sides of the step room 56 and thus executed or arranged such that on average a unidirectional flow through the step room 56 With fuel, namely in the drawing from left to right, takes place, whereby the cooling is particularly effective. The Teflon seal 50 seal the step room 56 hydraulically against the cylinder head (roller tappet, cam, roller).

In an embodiment, not shown, of the piston pump 24 is one of the connection channels 52 respectively. 54 not in the case 34 arranged, but is carried out by means of an external hydraulic line. In a further embodiment, not shown, of the piston pump 24 are both connection channels 52 and 54 carried out by means of external hydraulic lines.

The 3 and 4 show schematically an alternative embodiment for the check valve 58 respectively. 60 , Present is the check valve 58 respectively. 60 as a ball-cone valve by means of a valve ball 72 executed, which by means of a valve spring 74 against a valve seat 76 can dense. The check valve 58 respectively. 60 is in the 3 in a closed and in the 4 shown in an open state.

The 5 and 6 schematically show a further alternative embodiment for the check valve 58 respectively. 60 , Present is the check valve 58 respectively. 60 designed as a mushroom valve, with an elastic mushroom head 78 against a valve seat 80 can dense. A shaft 82 the mushroom valve allows a certain axial guidance of the mushroom head 78 operational. The check valve 58 respectively. 60 is in the 5 in a closed and in the 6 shown in an open state.

Furthermore, the check valves 58 and 60 Also be designed as diaphragm valves. This is not shown in the drawing.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004063075 A1 [0002]

Claims (7)

Piston pump ( 24 ), in particular fuel pump for a fuel system ( 10 ) for an internal combustion engine, with an inlet-side low-pressure region ( 44 ), a piston ( 46 ) and a work space ( 25 ) coming from the piston ( 46 ), whereby the piston ( 46 ) one from the workspace ( 25 ) pointing away in a fluid space ( 56 ), and wherein the fluid space ( 56 ) at least temporarily via at least one connecting channel ( 52 . 54 ) with the low-pressure region ( 44 ), characterized in that at least two connection channels ( 52 . 54 ) are present, and that in the one connection channel ( 52 ) a first and the fluid space ( 56 ) opening check valve ( 58 ) and in the other connection channel ( 54 ) a second and the low pressure area ( 44 ) opening check valve ( 60 ) is arranged. Piston pump ( 24 ) according to at least one of the preceding claims, characterized in that the check valve ( 58 . 60 ) is a beak-slit valve or a diaphragm valve or a mushroom valve or a ball-cone valve. Piston pump ( 24 ) according to at least one of the preceding claims, characterized in that the connecting channels ( 52 . 54 ) and the check valves ( 58 . 60 ) are designed and arranged such that on average a directed flow through the fluid space ( 56 ) with fuel. Piston pump ( 24 ) according to at least one of the preceding claims, characterized in that it comprises a Teflon seal ( 50 ), by means of which a fuel area in the piston pump ( 24 ) is sealed against an oil area in a cylinder head. Piston pump ( 24 ) according to at least one of the preceding claims, characterized in that at least one connecting channel ( 52 . 54 ) in a housing ( 34 ) of the piston pump ( 24 ) is arranged. Piston pump ( 24 ) according to at least one of the preceding claims, characterized in that the connecting channels ( 52 . 54 ) substantially straight and parallel to a longitudinal axis ( 32 ) of the piston ( 46 ) are executed. Piston pump ( 24 ) according to at least one of the preceding claims, characterized in that the first check valve ( 58 ) at one to the low pressure area ( 44 ) facing end portion of a connecting channel ( 52 ) is arranged, and that the second check valve ( 60 ) at one to the fluid space ( 56 ) pointing end portion of the other connection channel ( 54 ) is arranged.

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