US20080187451A1

US20080187451A1 - Feed Unit

Info

Publication number: US20080187451A1
Application number: US11/912,727
Authority: US
Inventors: Reinhard Dittmann; Markus Moertl; Christoph Mittermueller
Original assignee: Individual
Current assignee: Robert Bosch GmbH
Priority date: 2005-06-30
Filing date: 2006-05-08
Publication date: 2008-08-07
Also published as: DE102005030540A1; WO2007003456A1; EP1899607A1

Abstract

A feed unit for a fuel pup includes a rotor eccentrically mounted in a pump chamber, and a plurality of grooves disposed on the periphery of the rotor. The grooves receive a plurality of sealing bodies which extend from within the grooves to an annular wall of the pump chamber embodied as a curved track. A gap is defined between the rotor and the curved track and is subdivided into gap spaces that are sealed from each other by the sealing bodies, which are configured as elastic spring elements.

Description

PRIOR ART

The invention is based on a feed unit as generically defined by the preamble to the main claim.
A feed unit is already known from U.S. Pat. No. 5,378,111, having a rotor supported eccentrically in a pump chamber and having grooves, disposed on the circumference of the rotor, in which rollers, resting on a curved track of the pump chamber, are provided as sealing bodies. Between the rotor and the curved track, a gap is formed, which is split by the rollers into gap spaces that are sealed off from one another by means of the rollers. The grooves, the rollers supported in the grooves, and the curved track require very great production precision, if low wear at the curved track and a high degree of running smoothness of the feed unit are to be attained. Since the rollers can be allowed to protrude only scarcely halfway out of the groove at most, so that they will not tilt, the volume of the gap spaces and hence the feed capacity are limited. The sealing action of the rollers is based on the centrifugal force with which the rollers are pressed against the curved track. To seal off the gap spaces well from one another, a comparatively high mass of the rollers is necessary, but when the rollers vibrate, this causes wear to the curved track as well as running noise. The grooves require great production precision, so that the rollers will be adequately guided in the grooves. The rotor must be embodied as wear-resistant.

ADVANTAGES OF THE INVENTION

The feed unit according to the invention having the definitive characteristics of the body of the main claim has the advantage over the prior art that in a simple way, an improvement is attained such that the prod-action costs of the feed unit are reduced because the scaling bodies are embodied as elastic spring elements. In this way, the volume of the gap spaces can be increased markedly, so that a greater feeding capacity is attained for the same rpm. The curved track requires much less production precision than in the prior art, since the spring elements have a long spring travel for adaptation to the cured track. Because of the low mass of the spring elements, the wear to the curved track is also reduced. The requisite production precision and the requirements for wear resistance with regard to the rotor are markedly less than in the prior art.
By the provisions recited in the dependent claims, advantageous refinements of and improvements to the feed unit defined by the main claim are possible.
It is especially advantageous if the spring elements are supported unilaterally inside the pockets of the rotor, since in this way a long spring travel of the spring elements is possible, which makes it possible to embody large gap spaces and hence permits a high feed capacity.
It is also advantageous if the pockets are embodied in groovelike form, with two lateral flanks and a groove base, and the spring elements are secured by a Securing portion to one of the lateral flans or to the groove base.
It is highly advantageous if the spring element has a spring arm, with a curved portion cooperating with the curved track, since in this way a linear sealing is attained.
It is also advantageous that by elastic bending, the spring element can be resiliently pressed all the way into the associated pocket, since in this way the rotor can pass through an extremely narrow gap.
In an advantageous embodiment, it is provided that the elastic spring elements are embodied as leaf springs or spiral springs.
It is also advantageous if the elastic spring elements are each embodied as a spring assembly, comprising two leaf springs, joined solidly to one another at the ends, and are placed loosely in the pockets, since in this way an alternative version is achieved.

DRAWINGS

Two exemplary embodiments of the invention are shown in simplified form in the drawing and described in further detail in the ensuing description.

FIG. 1 shows a feed unit in section;

FIG. 2 shows a view of a first exemplary embodiment;

FIG. 3 shows a section through a spring element of the invention taken along the line III-III in FIG. 2; and

FIG. 4 shows a view of a second exemplary embodiment of the feed unit of the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a feed unit in which the embodiment according to the invention can be employed.
The unit according to the invention has a housing 1, for instance cylindrical in shape, with at least one inlet conduit 2 and one outlet conduit 3. The inlet conduit 2 of the unit communicates, for instance via a suction line 6, with a tank 7, in which fuel, fox instance, is stored. The outlet conduit 3 of the unit communicates with an internal combustion engine 9, for instance via a pressure line 8.
The housing 1 of the unit has a pump part 12 and a drive part 13. The pump part 12 has a pump chamber 14, which for instance is embodied cylindrically. A region upstream of the pump chamber 14 is called the intake side of the unit, while a region downstream of the pump chamber 14 is called the compression side of the unit. A rotor 15 is rotatably supported in the pump chamber 14, and the rotor 15 and the pump chamber 14 are disposed eccentrically to one another. The rotor 15 is driven to rotate by an actuator 18 via a drive shaft 19, the actuator being provided in the drive part 13 and for instance being an armature of an electric motor.
The pump chamber 14 is defined by two end walls diametrically opposite one another in the direction of a rotationally symmetrical axis 20 of the rotor 15, specifically a first end wall 21 oriented toward the inlet conduit 2 and a second end wall 22 oriented toward the outlet conduit 3, and in the radial direction relative to the axis 20 the pump chamber is defined by an annular wall 23.
The first end wall 21 is embodied on the inside, toward the rotor 15, of an intake cap 26, for instance disklike in shape, and the second end wall 22 is embodied on the inside, toward the rotor 15, of a pressure cap 27, which is for instance disklike in shape. The annular wall 23 is provided for instance on the inside, toward the rotor 15, of an annular intermediate cap 28. The intermediate cap 28 is disposed for instance between the disklike intake cap 26 and the disklike pressure cap 27. The intermediate cap 28 may, however, also be integrally joined to the intake cap 26 or to the pressure cap 27. The intermediate cap 28 with the annular wall 23 is for instance disposed eccentrically to the rotor 15.
The housing 1 has a cylindrical portion 31, which has the intake cap 26 on the face end toward the pump part 12 and has a connection cap 32 on the face end toward the drive part 13. The intake cap 26 and the connection cap 32 close off the cylindrical portion 31 of the housing 1 tightly from the external environment.
The inlet conduit 2 of the housing 1 is disposed for instance on the intake cap 26 and communicates with the flow direction with a pump chamber inlet 33 that discharges into the pump chamber 14. The outlet conduit 3 of the housing 1 is disposed for instance on the connection cap 32. The connection cap 32 has an electrical terminal 36, for instance, for contacting the actuator 18 provided in the housing 1.
A pump chamber outlet 34, which connects the pump chamber 14 downstream with a pressure chamber 35 of the housing 1, is disposed for instance in the pressure cap 27 of the unit. However, the pump chamber outlet 34 may also be provided on the intake cap 26. The pressure chamber 35 is embodied in the drive part 13 and is defined radially by the cylindrical portion 31 and axially by the pressure cap 27 and the connection cap 32. The actuator 18 is disposed for instance in the pressure chamber 35. The pressure cap 27 has a drive shaft conduit 37, which extends through the drive shaft 19 into the pump chamber 14 so as to drive the rotor 15 to rotate. The drive shaft 19 is supported for instance on the end, remote from the actuator 18, in a bearing recess 38 of the intake cap 26. The pressure chamber 35 communicates at least indirectly with the engine 9 via the outlet conduit 3 of the housing 1 and the pressure line 8.
The rotor 15 is embodied for instance as a cylindrical disk. A plurality of sealing bodies 39 are provided on the rotor 15. The sealing bodies 39 are disposed for instance in pockets 40 of the rotor 15 that are distributed uniformly over the circumference of the rotor 15, and the sealing bodies extend from the pockets 40 of the rotor 15 up to the annular wall 23. Upon the rotation of the rotor 15, the sealing bodies slide along the annular wall 23. The annular wall 23 forms a so-called curved track 24. The curved track 24 may be embodied circularly or elliptically, for instance, but is expressly arbitrary.
FIG. 2 shows a unit according to the invention in section, in accordance with a first exemplary embodiment.
In the unit of FIG. 2, the elements that remain the same or function the same as in the unit of FIG. 1 are identified by the same reference numerals.
The pockets 40 are embodied as a recess, which for instance is groovelike but whose shape is expressly arbitrary. There is preferably an odd number of pockets 40. For instance, the pockets 40 penetrate the rotor 15 in the axial direction, with respect to the axis 20, from one face end of the rotor 15 to the other face end. From the outer circumference, the pockets 40 extend radially inward, with two lateral flanks 43, disposed parallel to one another for instance, and each ends in a groove base 44.
Because of the eccentric arrangement of the rotor 15 in the pump chamber 14, there is one region on the curved track 24 having the least spacing between the rotor 15 and the curved track 24, hereinafter called the narrow gap 45, and one region on the curved track 24 having the greatest spacing between the rotor 15 and the curved track 24, which will hereinafter be called the wide gap 46.
Because of the eccentric disposition of the rotor 15 in the pump chamber 14, a crescent-shaped gap 48 is created between the curved track 24 and the rotor 15; this gap is divided by the sealing bodies 39 into a plurality of gap spaces 49, for instance crescent-shaped, that are separated from one another. The number of gap spaces 49 matches the number of sealing bodies 39.
Upon the rotation of the rotor 15 in a direction of rotation 16, the sealing bodies 39 rest on the curved track 24, so that the individual gap spaces 49 are sealed off Thom one another.
The pump chamber inlet 33 and/or the pump chamber outlet 34 is embodied as a kidney-shaped groove, for instance.
The pump chamber inlet 33 is disposed for instance such that each gap space 49, upon the rotation of the rotor 15, intermittently communicates fluidically with the pump chamber inlet 33 through an overlap, and fluid flows into the applicable gap space 49 via the inlet conduit 2 and the pump chamber inlet 33. The pump chamber outlet 34 is disposed for instance such that each gap space 49, upon the rotation of the rotor 15, intermittently communicates fluidically with the pump chamber outlet 34 by overlap, and fluid flows out of the applicable gap space 49 into the pump chamber outlet 34.
The curved track 24 comprises an intake region 58, a compression region 60, and a sealing region 61. The intake region 58 is located in the region of the pump chamber inlet 33 between the narrow gap 45 and the wide gap 46; the reversing region 59 is disposed in the region of the wide gap 46, between the pump chamber inlet 33 and the pump chamber outlet 34; the compression region 60 is located in the region of the pump chamber outlet 34; and the sealing region 61 is located in the region of the narrow gap 45.
In the intake region 58, the gap width of the gap 48 increases from the narrow gap as far as the wide gap 46, in the direction of rotation 16 of the rotor 15, so that the volume of the individual gap spaces 49, viewed in the direction of rotation of the rotor 15, increases, and a negative pressure occurs there. As soon as the pump chamber inlet 33, in the intake region 58, overlaps with one of the gap spaces 49 as a result of the rotation of the rotor 15, the pump chamber inlet 33 is open to the applicable gap space 49, so that fluid flows continuously into the applicable gap space 49. In the intake region 58, fluid is thus aspirated into the applicable gap space 49.
The filling of the applicable gap space 49 ends when the gap space 49, by further rotation of the rotor 15, no longer communicates with the pump chamber inlet 33. The gap space 49 is then closed off from the environment and reaches the reversing region 59.
In the reversing region 59, the gap space 49 is closed and in this way seals off the pump chamber outlet 34 from the pump chamber inlet 33.
In the compression region 60, the applicable gap space 49 is evacuated, because as a result of the reduction in the volume of the applicable gap space 49 a pressure is built up, and the fluid is forced in this way out of the gap space 49 into the pump chamber outlet 34. This happens as soon as the pump chamber outlet 34, in the rotation of the rotor 15, overlaps with the applicable gap space 49. The pump chamber outlet 34 is then open to the applicable gap space 49.
The sealing region 61 seals off the compression region 60 from the intake region 58, so that virtually no leakage from the compression region 60 into the intake region 58 occurs. The radial gap width between the rotor 15 and the cured track 24 in the sealing region 61 should be embodied to be as small as possible and the sealing region 61 should be embodied to be as large as possible, so that the fluid of the applicable gap space 49 is evacuated as completely as possible in the direction of the pump chamber outlet '34 and does not reach the intake region 58 again in the form of a leakage flow via the narrow gap 45.
According to the invention, it is provided that the sealing bodies 39 are embodied as elastic spring elements. In an advantageous feature, a leaf spring, spiral spring, or the like is used for instance as the elastic spring element. As the material for the elastic spring element 39, spring steel or plastic is for instance used. The rotor 15 may be produced from an arbitrary material, such as metal or plastic.
The spring elements 39 conform with a linear contact to the curved track 24 and one another (FIG. 3) both at the curved track 24 and at the end walls 21, 22.
In a first embodiment, it is provided that the spring elements 39 are supported only unilaterally; each spring element 39 is secured by a securing portion 50 inside the applicable pocket 40 on the rotor 15 and extends with a spring arm 51 as far as the curved track 24. The spring arm 51 for instance has a curved portion 51.1 with a radius, which rests on the cured track 24.
Upon the rotation of the rotor 15, the gap 48 varies in the radial direction, so that the spring element 39 with the spring arm 51 is elastically bent toward the rotor 15 upon a reduction of the gap 48 and is moved in the direction away from the rotor 15 upon an increase in size of the gap 48. Upon an increase in size of the gap 48, the spring element 39 remains in contact with the curved track 24, since the spring element 39, being elastically prestressed, is pressed against the curved track 24. Since the gap 48 at the narrow gap 45 is very slight, the pockets 40 must extend in the circumferential direction of the rotor 15 far enough that the spring elements 39 with their spring arm 51 on passing through the narrow gap 45 can be lowered in their pocket 40 and can plunge at least nearly completely into the pocket. It is also possible to embody the rotor 15 without pockets; then the spring elements 39, instead of plunging into the pockets, rest on the circumference of the rotor 15.
As an example, the spring elements 39 are disposed on a lateral flank 43 that leads ahead in the direction of rotation of the rotor 15 and extend, counter to the direction of rotation 16, at an acute angle 52 as far as the curved track 24. The spring elements 39, however, may also be solidly joined to the rotor 15 at the groove base 44. The spring elements 39 are welded with the securing portion 50 to the rotor 15, for instance, or pressed, inserted, glued or the like into a groove 53 of the rotor 15. However, they may also be provided integrally on the rotor 15, for instance by means of injection molding. The spring elements 39 may also be placed loosely in the pockets 40 (FIG. 4).
To avoid or reduce vibration of the spring elements 39 in operation of the feed unit, the mass of the spring elements 39 and/or their spring stiffness is designed accordingly, for instance by providing accumulations of material or additional weights at certain points of the spring elements 39.
It is also possible to embody the spring elements 39 such that upon loading above a predetermined overpressure, they yield elastically, so that the sealing action of the spring elements 39 of the applicable gap space 49 no longer exists, and fluid can flow out of the gap space 49 that is subjected to excessively high pressure into the adjacent gap spaces 49. In this way, the spring elements 39 have a pressure limiting valve function.
FIG. 3 shows a section through the spring element of the invention taken along the line III-III in FIG. 2.
In the unit of FIG. 3, the elements that remain the same or function the same as in the unit of FIGS. 1 and 2 are identified by the same reference numerals.
The spring elements 39 are bent toward the face ends 21, 22, in order to achieve good sealing with little friction.
FIG. 4 shows a unit according to the invention in a second exemplary embodiment in section.
In the unit of FIG. 4, the elements that remain the same or function the same as in the unit of FIGS. 1 through 3 are identified by the same reference numerals.
The feed unit of FIG. 4 differs from the feed unit of FIG. 2 in that instead of the unilaterally supported spring element 51, a spring assembly 54, each comprising two leaf springs, is disposed in the pockets 40. The two leaf springs are solidly joined together at their ends and in this way form an oval-shaped spring assembly. The spring assemblies 54 may also be embodied in one piece and are made for instance from spring steel or plastic. The spring assemblies 54 are prestressed in the pockets 40 in such a way that one of the leaf springs of the spring assembly 54 is pressed against the curved track 24, and the other is pressed against the groove base 44 of the applicable pocket 40. The spring assemblies 54 are placed loosely in the pockets 40.

Claims

1-8. (canceled)

9. A feed unit for a fuel pump, comprising:

a cylindrical pump chamber having an annular wall embodied as a curved track;

a rotor supported rotatably and eccentrically within the pump chamber;

a plurality of pockets disposed on a periphery of the rotor; and

a plurality of sealing bodies disposed within the pockets and extending from the pockets to the curved track of the rotor,

wherein the sealing bodies are embodied as elastic spring elements.

10. The feed unit according to claim 9, wherein the spring elements are supported unilaterally inside the pockets of the rotor.

11. The feed unit according to claim 10, wherein the pockets are embodied in groovelike form, with two lateral flanks and a groove base, and the spring elements are secured by a securing portion to one of the lateral flanks or to the groove base.

12. The feed nit according to claim 9, wherein the spring element has a spring arm with a curved portion cooperating with the curved track.

13. The feed unit according to claim 11, wherein by elastic bending the spring element can be resiliently pressed all the way into the associated pocket.

14. The feed unit according to claim 9, wherein the elastic spring elements are leaf springs or spiral springs.

15. The feed unit according to claim 9, wherein the elastic spring elements are each embodied as a spring assembly, comprising two leaf springs, joined solidly to one another at the ends, and are placed loosely in the pockets.

16. The feed unit according to claim 9, wherein the spring elements are embodied integrally on the rotor.