GB2134598A

GB2134598A - Fuel pumps for internal- combustion engines

Info

Publication number: GB2134598A
Application number: GB08332635A
Authority: GB
Inventors: Heinrich Knapp; Klaus Rose
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1983-02-02
Filing date: 1983-12-07
Publication date: 1984-08-15
Also published as: GB8332635D0; JPS59145395A; DE3303352A1

Abstract

The pump comprises a first stage 42 including an impeller 38 connected in series with a second stage 46 including an impeller 40. The first stage consists of a side-channel pump having an inlet 66 and a degassing line 68, and the second stage is provided with an outlet 86. The pump is driven by an electric motor which is cooled by the pumped fuel. Modifications are described in which the first stage is of smaller diameter than the second stage and in which the second stage surrounds the first stage. <IMAGE>

Description

SPECIFICATION Unit for feeding fuel preferably from a supply tank to the internal-combustion engine especially of a motor vehicle Prior Art The invention starts from a feed unit of the generic type of the main claim. There is already a known feed unit (U.S. Patent Specification 4,209,284) in which two so-called open periphery or regenerative pumps are arranged in series.

However, such a unit achieves only a feed pressure of approximately 0.7 bar, and this is not sufficient for certain purposes. However, if two Westco pumps building up a higher feed pressure, as are described in "Centrifugal pumps" by Carl Pfleiderer, 5th Edition of 1961, are connected in series, it is not possible to separate from the feed stream the gas bubbles (cavitation) escaping from the feed medium during intake, so that a proper fuel feed is not guaranteed. This fault occurs to a greater extent when the feed medium is heated.

Advantages of the Invention The feed unit according to the invention, with the characterising features of the main claim, has, in contrast, the advantage that degassing of the feed medium is possible without difficulty in the first feed stage, so that an appreciable reduction in the feed rate as a result of the formation of gas bubbles in the region of the second feed stage no longer arises. However, the necessary increase in pressure is achieved by means of the second feed stage where a final pressure of approximately 1.0 bar is possible.

As a result of the measures listed in the subclaims, advantageous developments and improvements of the feed unit indicated in the main claim are possible. It is especially advantageous if the two feed impellers are arranged at least essentially in a common rotational plane, the impeller of the first feed pump being surrounded by the impeller of the second feed pump.

Appropriately, these two pump impellers are located on a single disc-shaped component.

Drawing Exemplary embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. Figure 1 shows a diagrammatic representation of an arrangement with a fuel supply tank, a fuel feed unit and an internal-combustion engine, Figure 2 shows a partial longitudinal section through the pump region of a feed unit according to the invention, the section being taken so that both the inlet and the outlet of the first pump stage lie in one plane, Figure 3 shows a partial longitudinal section through a differently designed pump region of the feed unit, the section being taken so that both the inlet and the outlet of the first pump stage lie in one plane, Figure 4 shows a partial longitudinal section through the pump region of a further feed unit according to the invention, Figure 5 shows a partial view of an impeller of the feed pump according to Figure 4, as seen in the direction of the arrow V in Figure 4, Figure 6 shows, in an enlarged representation, a section through a pump region modified in respect of the pump region illustrated in Figure 4, and Figure 7 shows a partial view of a chamber wall belonging to the pump according to Figures 4 and 6, as seen in the direction of the arrow V in Figure 4.

Description of the Exemplary Embodiments Figure 1 shows a fuel supply tank 10 which is connected via a suction line 12 to the suction side of a fuel feed unit 14. A delivery line 1 6 leading to an internal-combustion engine 1 8 is connected to the delivery side of the fuel feed unit 14. During the running of the internal-combustion engine, the fuel feed unit 1 4 conveys fuel from the supply tank 10 to the internal-combustion engine 1 8.

A pump region 20, shown in Figure 2, of the feed unit 14 is located in a housing 22 surrounding, in addition to the pump region 20, a space 24 in which an electric drive motor (not shown) is arranged. A shaft 26 projecting into the pump region 20 is driven by the electric motor.

This shaft is mounted in a cover 28 belonging to the housing 22 and passes through an intermediate wall 30 retained in the housing 22.

An intermediate plate 32 is located between the cover 28 and the intermediate wall 30. The end faces 27 and 29, turned towards one another, of the cover 28 and of the intermediate plate 32 and the end faces 31 and 33 of the intermediate plate 32 and of the intermediate wall 30 are formed so that, as seen in the direction of the shaft 26, two pump spaces 34 and 36 result, in each of which a pump impeller 38 and 40 respectively is arranged.

The two pump impellers are connected in a nonrotational manner to the shaft 26 serving as a guide element for the pump impellers 38 and 40.

The pump impeller 38 belongs to a pump stage 42 which is the first, as seen in the direction of flow of the medium, and which is connected to a second pump stage 46 via a connecting line 44. The first pump stage 42 contains a so-called double-flow side-channel pump, the cylindrical pump impeller 38 of which has on the peripheral region 48 conveying means 50 which extend radially and are fixed. The blade-like conveying means 50 are arranged at a distance from one another, as seen in the peripheral direction of the pump impeller 38, so that there remain between the conveying means adjacent to one another chambers which are open towards the two end faces 27 and 29 and towards the peripheral region 48 of the pump impeller 38. The conveying means 50 form a ring 56 which revolves in a pump chamber 58.The pump chamber 58 is formed by approximately annular recesses 60 and 62 in the cover 28 and the intermediate plate 32. Furthermore, the two recesses 60 and 62 are connected to one another by means of an intermediate channel 64 which is arranged in the peripheral region of the pump impeller 38. An inlet or intake orifice 66 opening into the recess 60 is located in the cover 28.

Moreover, the cover 38 has a degassing line 68 which passes through the cover 28 and which opens on the end face 27 of the cover 28, which face is turned towards the pump impeller 38.

According to Figure 2, the pump impeller 40 belonging to the second pump stage 46 likewise has conveying means 74 on its peripheral region 72. These conveying means 74 are arranged at a distance from one another, as seen in the peripheral direction of the pump impeller 40.

Chambers remaining between the conveying means open only towards one of the two end faces 76 and 78 of the pump impeller and towards the peripheral region 72 thereof. At the same time, as seen in a peripheral direction, each of the chambers adjacent to one another opens towards the other end face 76 and 78 respectively of the pump impeller 40 designed as a disc-shaped component. In this way, as seen in the direction of the axis of rotation of the pump impeller 40, opposite a conveying means 74 of one end face 76 or 78 is located a chamber which opens on the other end face 78 or 76 respectively of the pump impeller 40. The pump impeller 40 is likewise located in a pump space 36 which is formed as a result of appropriate shaping of the end faces 51 and 33, turned towards one another, of the intermediate plate 32 and of the intermediate wall 30.The conveying means 74 of the pump impeller 40 likewise form, on the peripheral region of the pump impeller 40, a conveying-means ring 75 which revolves in a pump chamber 84 of a design corresponding to that of the pump chamber 58 of the first pump stage 42.

The connecting line 44 extends from the delivery region of the first pump stage 42 to the inlet region of the second pump stage 46. The cross-section of the connecting line 44 narrows in the direction of flow of the feed medium. The outlet region of the second pump stage 46 is connected to the space 24 via an outlet channel 86, so that the conveyed medium flows through this space 24 and at the same time washes round and cools essential parts of the electric motor. The feed medium leaves the feed unit 14 via a delivery line (not shown) and flows through the delivery line 1 6 to the internal-combustion engine 1 8 (Figure 1).

The specialist literature speaks of so-called Westco pumps when referring to feed pumps of a design corresponding to that of the second pump stage 46.

In the exemplary embodiment according to Figure 3, all the components conform in their design and arrangement to the corresponding components of the exemplary embodiment illustrated in Figure 2. The only difference is that the pump impeller 39 of the first pump stage 42 has a smaller diameter than the impeller 40 of the second pump stage 46. In the exemplary embodiment according to Figure 2, the diameters of the two pump impellers 38 and 40 are the same. Likewise, a common feature of the two exemplary embodiments according to Figures 2 and 3 is that the impeller 38 or 39 of the first pump stage 42 is larger than the impeller 40 of the second pump stage 46, as measured in the direction of the common axis of rotation.

Since all the other design features of the arrangement according to Figure 3 conform to the design features of the pump region illustrated in Figure 2, the reference numerals of Figure 2, mentioned there, can be transferred to Figure 3.

However, it goes without saying that in the exemplary embodiment according to Figure 3 the size of the pump chamber 58 matches the smaller diameter of the pump impeller 39.

In the embodiment according to Figure 4, the two pump impellers 90 and 92 are arranged on a disc-shaped component 94. At the same time, they lie in a common rotational plane. The impeller 90 of the first pump stage 96 is surrounded by the impeller 92 of the second pump stage 98. The disc-shaped component 94 forming the single pump impeller of this embodiment has a plurality of axially extending perforations 100 (Figure 5) which are arranged at a distance from one another in the peripheral direction of the component 94.

The webs 102 remaining between the individual perforations 100 form the fixed, radially extending blade-like conveying means of the first pump stage 96. As seen in a radial direction, the axial perforations 100 are limited on the inside and outside by cylindrical surfaces 1 03. However, it is conceivable, according to a design illustrated in Figure 6, for these perforations 100 to be limited, as seen in a radial direction, on the inside and outside by toroidal surfaces 104. The conveying means 106 of the second pump stage 98 are likewise of blade-like design and are arranged in the peripheral region of the disc-shaped component 94 (Figure 5). Between the conveying means 106 adjacent to one another are formed chambers 108, the bottoms 110 of which are rounded in the form of toroidal surfaces (Figure 6).

The chambers 108 (Figure 5) are open only towards one of the two end faces 112 or 114 of the disc-shaped component 94 (Figure 6). At the same time, these chambers are arranged in such a way that the orifice to the periphery 11 5 of the component 94 is less than half the thickness 11 6 of the cylindrical disc-shaped component 94.

Furthermore, the chambers 108 adjacent to one another are arranged so that these chambers 108 are open alternately towards the other end face 112 or 113 of the disc-shaped component 94.

The component 94 is located, as seen in the direction of its axis of rotation, between limiting walls 118 and 120 fixed to the housing, and in each limiting wall 118 and 120 there is an approximately annular channel 122 and 124 respectively, these being assigned to the ring of conveying means 102 of the first pump stage.

Moreover, in each of the limiting walls 11 8, 120 fixed to the housing an approximately annular channel 126 and 1 28 is also located, these being assigned to the ring of conveying means 106 of the second pump stage 98. The two channels 126 and 128 assigned to the outer ring of conveying means 106 are connected to one another by means of a transverse channel 130 surrounding the periphery of the component 94. Both the annular channels 122 and 124 and the annular channels 126, 128 are located in a cover 134 and in a pump-housing part 1 38 respectively. The cover 1 34 belongs to the housing 22 of the feed unit 14. The pump-housing part 138 is retained by the housing 22 of the unit.There passes through it the drive shaft 26, of which the end located on the same side as the pump is mounted in the cover 1 34 (Figure 4). However, a so-called "floating mounting" of the drive shaft 26 is also conceivable, as illustrated in Figure 6. The two channels 122 and 128 are connected to one another by means of a recess 142 (Figure 6) located in the pump-housing part 138 and serving as a line. This recess extends essentially radially (Figure 7). However, it can also have in its course a radial component and a component in the direction of rotation of the component 94. Located in the cover 134 within the ring of conveying means 102 of the first pump stage 96 or within the annular channel 122 assigned to this ring of conveying means 102 is a degassing line 148 which opens out at the limiting wall 118 and which passes through the cover 134.

The mode of operation of the pumping unit illustrated in Figure 2 is described below. When the feed unit 14 is in operation, the medium to be conveyed passes via the inlet orifice 66 into the first pump stage 42 where an increase in pressure takes place. Subsequently, the medium leaves the first pump stage 42 via the connecting line 44 and passes into the inlet region of the second pump stage 46. A further increase in pressure takes place there, until the feed medium leaves the second pump stage 46 via the outlet channel 86.

During the acceleration of the feed medium in the first pump stage 46, gas bubbles possibly occurring collect, because of their lower specific gravity, in the inner region of the pump chamber 58, from where, under increasing pressure, they pass through narrow axial gaps, located between the end faces of the first pump impeller 38 and the end faces 27 of the cover 28 and the end face 29 of the intermediate plate 32, to the degassing line 68, from where the gas leaves the first pump stage. The gas is therefore separated from the fuel flow. This applies to the same extent in the design according to Figure 3.

The mode of operation of the two pump regions according to Figures 4 and 6, which are of very similar design, is explained with reference to the illustration according to Figure 6. There, fuel likewise passes via an inlet orifice 1 50 into the annular channel 122, 126, where it is taken along by the conveying means 102 and undergoes an increase in pressure until it passes via the recess 142 serving as a line into the inlet region of the second pump stage 98. After a further increase in pressure in the second pump stage 98, the feed medium leaves the latter via an outlet orifice 1 52 (Figure 4). In this embodiment also, the feed medium passes into a space 24 which is surrounded by the housing 22 and which contains an electric drive motor.

The gas bubbles arising in the first pump stage likewise collect in the inner region of the annular channels 122, 124, from where, under a correspondingly increasing pressure, they pass via the axial gaps 152,154 to the degassing line 148 and consequently out of the flow of feed medium.

A common feature of all the exemplary embodiments is that the pump region 20 has at least two pump stages 42 and 46 or 96 and 98 connected in series in the direction of flow of the medium to be conveyed, the second pump stage 46 or 98 being designed as a Westco pump.

Claims

1. Unit for feeding fuel preferably from a supply tank to an internal-combustion engine especially of a motor vehicle, with at least two feed pumps which are arranged in series in the direction of flow of the fuel and each feed pump of which has a pump impeller provided with radially extending, fixed blade-like conveying means which each revolve in an annular pump chamber, the outlet of the feed pump which is the first, as seen in the direction of flow, being connected by means of a connecting line to the inlet of the second feed pump, characterised in that the second feed pump (46 or 98), is designed as a Westco pump.

2. Unit according to Claim 1, characterised in that the two pump impellers (38 and 40) rest on a common rotating guide element (26).

3. Unit according to Claim 2, characterised in that the guide element is a shaft (26) mounted in a housing part (28).

4. Unit according to Claim 3, characterised in that the housing part (28) belongs to a housing (22) which surrounds the two feed pumps (42 and 46) and a space (24) in which an electric drive motor is accommodated.

5. Unit according to Claim 1, characterised in that the conveying means (50) of the impeller (38) of the first pump stage (42) are arranged on the peripheral region (48) of the cylindrical impeller (38), and in that the chambers remaining between the conveying means (50) arranged at a distance from one another, as seen in a peripheral direction, are open towards the two end faces of the pump impeller (38) and towards its peripheral region (48).

6. Unit according to Claim 5, characterised in that the conveying means (74) of the impeller (40) of the second pump stage (46) are arranged on the peripheral region (72) of the cylindrical impeller (40), and in that the chambers remaining between the conveying means (74) arranged at a distance from one another, as seen in a peripheral direction, are open towards one of the two end faces (76, 78) of the pump impeller (40) and towards its peripheral region (72).

7. Unit according to Claim 6, characterised in that, as seen in a peripheral direction, each of the chambers adjacent to one another are open towards the other end face of the disc-shaped pump impeller (40), and in that, as seen in an axial direction, a chamber is preferably located opposite a conveying means (74).

8. Unit according to Claim 7, characterised in that the diameters of the two pump impellers (38 and 40) are the same.

9. Unit according to Claim 7, characterised in that the impeller (39) of the first pump stage (42) has a smaller diameter than the impeller (40) of the second pump stage (46).

10. Unit according to one of Claims 8 or 9, characterised in that the impeller (38 or 39) of the first pump stage (42) is larger than the impeller (40) of the second pump stage (46), as measured in the direction of the common axis of rotation.

11. Unit according to Claim 1, characterised in that the cross-section of the connecting line (44) narrows in the direction of flow.

12. Unit according to Claim 1, characterised in that the two pump impellers (90 and 92) are arranged at least essentially in a common rotational plane, the impeller (90) of the first pump stage (96) being surrounded by the impeller (92) of the second pump stage (98).

13. Unit according to Claim 12, characterised in that the two pump impellers (90 and 92) are arranged on a disc-shaped component (94).

14. Unit according to Claim 13, characterised in that the blade-like conveying means (102) of the first pump stage (96) separate a plurality of axially extending perforations (100) in the component (94) from one another in a peripheral direction.

1 5. Unit according to Claim 14, characterised in that, as seen in a radial direction, the axial perforations (100) are limited on the inside and outside by cylindrical surfaces (103).

1 6. Unit according to Claim 14, characterised in that, as seen in a radial direction, the axial perforations (100) are limited on the inside and outside by toroidal surfaces (104).

17. Unit according to Claim 14, characterised in that the blade-like conveying means (1 06) of the second pump stage (98) are arranged on the periphery of the component (94).

1 8. Unit according to Claim 17, characterised in that the conveying means (106) are arranged at a distance from one another and limit chambers (108) located between them.

1 9. Unit according to Claim 18, characterised in that the bottoms (110) of the chambers (108) are rounded in the form of toroidal surfaces.

20. Unit according to Claim 18, characterised in that the chambers (108) are open towards the peripheral surface and towards one end face (112, 114) of the component (94).

21. Unit according to Claim 20, characterised in that, as seen in a peripheral direction, each of the chambers (108) adjacent to one another is open towards the other end face (112 or 114 respectively) of the disc-shaped component (94).

22. Unit according to Claim 21, characterised in that the orifices of the chambers (108) to the periphery of the component (94) are less than half the thickness (116) of the cylindrical component (94).

23. Unit according to Claim 22, characterised in that the component (94) is located, as seen in the direction of its axis of rotation, between limiting walls (11 8, 120) fixed to the housing, and in that an approximately annular channel (122, 124 and 126, 128) in the limiting walls (118,120) is assigned to each ring of conveying means (102 and 106 respectively).

24. Unit according to Claim 23, characterised in that the two channels (126, 128) assigned to the outer ring are connected to one another by means of a transverse channel (130) surrounding the periphery of the component (94).

25. Unit according to Claim 24, characterised in that within the ring of conveying means (102) of the first pump stage (96) a degassing channel (148) which passes through the housing (22), especially the cover (28 or 134), opens out at one limiting wall (118).

26. Unit according to Claim 23, characterised in that the two approximately annular channels (124 and 128) are connected to one another by means of a line (142) which is preferably designed as an open channel covered by the component (94) and which extends essentially radially.

27. Unit according to Claim 26, characterised in that the two approximately annular channels (124 and 128) are connected to one another by means of a line (142) which has a radial component and a component in the direction of rotation of the component (94).

28. Any of the fuel feed units substantially as herein described with reference to the accompanying drawings.