WO2003048564A1

WO2003048564A1 - Radial piston pump having force-feed lubrication

Info

Publication number: WO2003048564A1
Application number: PCT/DE2002/002879
Authority: WO
Inventors: Heinz Siegel; Helmut Rembold; Hans-Peter Stiefel; Karl Gmelin; Thomas Fuerst; Thilo Bolz
Original assignee: Robert Bosch Gmbh
Priority date: 2001-12-01
Filing date: 2002-08-06
Publication date: 2003-06-12
Also published as: EP1454055B1; EP1454055A1; ATE308676T1; DE50204804D1

Abstract

The invention relates to a radial piston pump for an injection system of internal combustion engines, in which a first plain bearing (7) and a second plain bearing (17) are provided in the form of a hydrostatic plain bearing, whereby the necessary pressure is provided by a pre-feed pump that supplies fuel to the radial piston pump via a fuel connection (31). This increases the bearing capacity of both the first plain bearing (7) and the second plain bearing (17). In addition, the cooling of said plain bearings (7, 17) is improved. As a result, the inventive radial piston pump can be subjected to higher loads with regard to pump capacity and pump head and has a longer serviceable life than that of prior art radial piston pumps.

Description

Radial piston pump with dual lubrication

State of the art

The invention relates to a radial piston pump for generating high fuel pressure for a

Fuel injection system of internal combustion engines, with a drive shaft, the drive shaft having an eccentric section and a stub shaft supported in a pump housing by a first slide bearing, preferably several with respect to the

Drive shaft radially arranged pump elements, with a ring arranged between the eccentric section and the pump element, and with a fuel connection in the pump housing.

Such an internally supported radial piston pump is known, for example, from DE 197 05 205 AI. Naturally, the mounting of the drive shaft in the pump housing and the mounting of the ring on the eccentric section of the drive shaft are subject to greater stress as the delivery volume and delivery head of the pump elements increase. Especially when the radial piston pump is to be used to deliver fuels with poor lubrication properties, such as gasoline, the mounting of the stub shaft in the pump housing and the mounting of the ring on the eccentric section of the drive shaft are a limiting factor for the delivery rate and the delivery head - 1

represents.

The object of the invention is to further develop a known radial piston pump in such a way that it can be used for larger delivery quantities and greater delivery heights without profound changes.

This object is achieved in a radial piston pump for high-pressure fuel generation for a fuel injection system of internal combustion engines, with a drive shaft, the drive shaft having an eccentric section and a stub shaft supported in a pump housing by a first slide bearing, preferably with a plurality of pump elements arranged radially with respect to the drive shaft, with one between the eccentric section and the pump elements arranged ring, and with a fuel connection in the pump housing, solved in that the first sliding bearing is forcibly flowed through by the fuel flowing through the fuel connection.

The fuel flowing into the fuel connection of the radial piston pump has a pressure, which is provided by a prefeed pump, of about 4-6 bar. This pressure is independent of the speed and the

Operating conditions of the radial piston pump. Because the fuel flowing through the fuel connection is forcibly guided through the first slide bearing, the first slide bearing is designed as a hydrostatic slide bearing. This creates a lubricating film with great reliability, so that the risk of "eaters" is significantly reduced. The load capacity of the first plain bearing also increases. This measure can be implemented by slight modifications of the first slide bearing on a known radial piston pump, so that the existing production facilities for manufacturing the radial piston pump can be taken over almost unchanged.

In a variant of the invention it is provided that the ring is supported on the eccentric section by a second slide bearing, and that the fuel flowing through the fuel connection forcibly flows through the second slide bearing, so that the load-bearing capacity of the second slide bearing is simple and effective Way is increased in all operating states and speeds of the high-pressure fuel pump.

A particularly economical embodiment of the invention provides that the first slide bearing has at least one lubrication groove running essentially in the direction of the axis of rotation of the drive shaft, so that the fuel flowing out of the fuel connection into the first slide bearing is ^' evenly distributed over the entire bearing surface and thus the uniform formation of a lubricating film is favored.

Another addition to the invention provides that the stub shaft has a central bore, that a transverse bore branches off from the central bore, and that the second slide bearing is supplied with fuel by the transverse bore. In this way, the fuel for lubrication of the second slide bearing can be introduced into the center of the bearing surface of the second slide bearing and flow from there to the edges of the slide bearing. This favors the formation of a stable lubricating film between the ring and the eccentric section of the drive shaft.

To further improve the lubricating film, that the second slide bearing has at least one lubrication groove running essentially in the direction of the axis of rotation of the drive shaft.

It has proven to be particularly advantageous if there is a hydraulic connection between the at least one lubrication groove and an interior of the pump housing on the side of the second slide bearing facing away from the shaft stub, since this ensures that the entire width of the second slide bearing is

Fuel flows through and thus a particularly good formation of the ^' lubricating film is achieved.

In a supplement of the invention it is provided that the eccentric section or the ring has an annular groove, and that the transverse bore opens into the annular groove, so that the fuel is distributed uniformly over the entire circumference of the second slide bearing.

To further increase the hydrostatic pressure in the second slide bearing, an impeller of a micropump can be inserted into the center bore, so that an additional pressure increase takes place depending on the speed of the radial piston pump, thus further increasing the load-bearing capacity of the second slide bearing at high speeds.

Alternative embodiments of the invention provide that the fuel connection opens into the interior of the housing or directly into the first slide bearing. As a result, the design of the first and second plain bearings according to the invention can be used equally advantageously in different types of radial piston pumps. Further advantageous refinements of the inventions provide that the lubrication groove is arranged on the stub shaft of the drive shaft, that the lubrication groove is arranged on the bushing of the first slide bearing, that the lubrication groove is arranged on the eccentric section of the drive shaft and / or that the lubrication groove on one Bushing of the second plain bearing is arranged so that the load capacity and life of the first and second plain bearings increase further.

It is particularly advantageous if the lubrication groove on the stub shaft and / or the lubrication groove on the eccentric section are arranged offset by approximately 180 ° to the resulting force vector.

The formation of a stable lubricating film can be further promoted if the lubricating groove on the shaft end and / or the lubricating groove on the eccentric section are designed to be spiral.

Further advantages and advantageous embodiments of the invention can be found in the following drawing, its description and the patent claims.

drawing

Show it:

Figure 1 is a representation of a first embodiment of an inventive

Radial piston pump in section, and

Figure 2 shows a second embodiment of a radial piston pump according to the invention in cross section. Description of the embodiments

In Fig. 1, a first embodiment of a radial piston pump according to the invention is shown in cross section. The radial piston pump consists of a pump housing 1. A drive shaft 3 is rotatably mounted in the pump housing 1. The drive shaft 3 is supported with a stub shaft 5 in a first slide bearing 7 in the pump housing 1. With its end opposite the shaft end 5, the drive shaft 3 is supported in a cover 9 by means of a ball bearing 11. Immediately next to the stub shaft 5, the drive shaft 3 has an eccentric section 13.

The eccentric section 13 is surrounded by a ring 15 which, in a view from the front (not shown), has a polygonal outer contour 19. The ring 15 does not rotate when the drive shaft 3 is rotated, but performs a circular movement. Between the

Ring 15 and the eccentric section 13, a second slide bearing 17 is present, which is pressed with the ring 15. With its polygonal outer contour 19, the ring 15 transmits the circular movement impressed on it by the eccentric section 13 to a piston foot plate 21 of a pump element 23.

The pump element 23 has a cylinder bore 25 and a piston 27. The piston 27 is set into an oscillating movement via the piston foot plate 21. As a result, fuel is drawn from a fuel connection (not shown) into a working space 29 and then pressurized during the so-called delivery stroke. The fuel, which is under high pressure, is fed through a high-pressure outlet (not shown) pushed out of the work space 29.

The high-pressure fuel pump is supplied via a fuel connection 31, which opens into the first slide bearing 7. The fuel in the fuel connection 31 is pressed into the first slide bearing 7 by a prefeed pump, not shown, with a delivery pressure of approximately 4-6 bar. This results in a very stable formation of a lubricating film between the pump housing 1 and the shaft end 5, which significantly increases the load-bearing capacity and service life of the first plain bearing 7.

In order to increase the throughput of fuel through the first slide bearing 7 and to promote the formation of a lubricating film, a plurality of lubrication grooves 33 are arranged distributed over the circumference of the first slide bearing 7. The lubrication grooves 33 can also be designed helically.

When the fuel has flowed through the first slide bearing 7, it reaches an interior 35 of the pump housing. From there, the fuel via a ^'in Fig. 1, not visible extension of the fuel port 31 during the suction stroke of the pump element is sucked into the working chamber 29 23. The first slide bearing 7 consists of a bush 37 pressed into the housing 1 with a pressed bush

Inner ring 36 and the stub shaft 5. The lubrication grooves 33 can be incorporated either in the inner ring 36 or in the stub shaft 5. When the lubrication grooves 33 are machined into the stub shaft 5, the rotary movement of the stub shaft can be used to deliver fuel into the first slide bearing 7. This further increases the load capacity of the first plain bearing 7.

In Fig. 2 is a second embodiment of an inventive radial piston pump in cross section shown :. Same components will be mine. provided with the same reference number and what has been said regarding FIG. 1 applies accordingly.

In this embodiment, the ball bearing 11 is inserted into the pump housing 1. The fuel connection 31 opens into the interior 35. From there, the fuel flows via lubrication grooves 33 through the first slide bearing 7 to the end of the stub shaft 5. From the cross-sectional illustration of FIG. 2 it can be seen that a bushing 37 is pressed into the housing 1, in which the lubrication grooves 33 are incorporated. The bush 37 forms, together with the stub shaft 5, the first slide bearing 7.

The stub shaft 5 has a central bore 39, which is penetrated by a transverse bore 41. The transverse bore 41 in turn opens into an annular groove 43 which is incorporated in the eccentric section 13 of the drive shaft 3. Alternatively, the annular groove 43 can also be worked into the ring 15. This alternative is not shown in Fig. 2. Via the central bore 39 and the transverse bore 41 and the annular groove 43, the fuel passes from the end of the stub shaft 5 to the second slide bearing 17, which is formed by the eccentric section 13 and the ring 15. In the eccentric ring 15 are lubrication grooves

45 incorporated, which extend parallel to the axis of rotation 47 of the drive shaft 3 over almost the entire width of the ring 15. The lubrication grooves 45 establish a hydraulic connection between the ring groove 43 and the interior 35 on the side of the ring 15 facing away from the shaft end 5. On the side of the ring 15 facing the stub shaft 5, the lubrication grooves 45 end in the ring 15, so that on this side of the ring 15 only very little fuel passes through the gap (not visible in FIG. 2) between the ring 15 and the eccentric section 13 in FIG Interior 35 occur can. This measure ensures that "fresh" fuel always flows out of the interior 35 through the first slide bearing 7 and that a short-circuit flow cannot occur between the second slide bearing 17 and the first slide bearing 7.

An impeller 49 of a micropump is pressed into the center bore 39 at the end of the stub shaft. This impeller rotates with the drive shaft 3 and generates a fuel flow, fuel being sucked in through the first slide bearing 7 and then flowing through the second slide bearing 17 due to the pressure increase of the micropump. The fuel passes through the annular groove 43 into the second slide bearing 17, the pressure increase by the micropump depending on the speed of the

Drive shaft 3 increases. As a result, the load capacity of the second plain bearing increases with increasing speed of the drive shaft 3. The hydrostatic pressure in the second slide bearing 17 is further increased by the centrifugal force which acts on the fuel (not shown) located in the transverse bore 41. This also leads to an increase in the load-bearing capacity of the second slide bearing 17 at higher speeds.

In Fig. 3, a third embodiment of a radial piston pump according to the invention is shown in cross section. The same components are provided with the same reference numerals and what has been said regarding FIGS. 1 and 2 applies accordingly. In the third exemplary embodiment, a coiled lubrication groove 33 is present in the stub shaft 5. In this exemplary embodiment, fuel is conveyed into the first slide bearing 7 by the rotation of the drive shaft 3, which increases its resilience and service life. In the same way is also in the eccentric section 13 of the drive shaft 3, a helical lubrication groove 45 is present. The lubrication groove 45 improves the supply of fuel to the second slide bearing 17 and thereby increases its load capacity and service life.

In Fig. 4, the third embodiment shown in Fig. 3 is shown schematically in a side view. On the basis of this illustration, the optimal arrangement of the coiled or straight lubrication grooves 37 and 45 will be explained. In this illustration, three pump elements 23-1, 23-11 and 23-111 which are arranged offset by 120 ° to one another are schematically represented by their longitudinal axes, which are actuated via the eccentric section 13 of the drive shaft. The direction of rotation of the drive shaft is shown by a first arrow 53. The direction of the resulting force vector 55, which acts on the shaft end 5 of the drive shaft and rotates with it, lies within the first angular range designated 57, which is preferably approximately 60 ° and whose central axis is approximately 90 ° to the maximum point of the

Eccentric section 13 is offset (axis 23-1). It is therefore advisable to arrange the lubrication groove 33 offset by 180 ° to the first winding area 57. The preferred location for arranging the lubrication groove 33 is identified in FIG. 4 as the second angular range 59. In this way, the load-bearing capacity of the first plain bearing 7 is not impaired by the lubrication groove 33 in the area of its highest stress. For the arrangement of the lubrication groove 45 (not shown) in the area of the second slide bearing 17, the first angular area 57 has 180 ° to the second

Angular range 59 is arranged offset, proven to be advantageous. Of course, if necessary, the first and second slide bearings 7 and 17 can also be lubricated with high-pressure fuel from the pump elements 23 (not shown). To control the amount of fuel flowing into the plain bearings, a throttle (not shown) can be provided for each plain bearing.

Claims

Expectations

1. Radial piston pump for high-pressure fuel generation for a fuel injection system of internal combustion engines, with a pump housing (1), with a drive shaft (3), the drive shaft (3) having an eccentric section (13) and one in the pump housing (1) by a first

Sliding bearing (7) having a stub shaft (5), preferably with a plurality of pump elements (23) arranged radially with respect to the drive shaft (1) and with a fuel connection (31) in the pump housing (1), characterized in that the first sliding bearing (7) is forcibly flowed through by fuel.

2. Radial ^' piston pump according to claim 1, characterized in that between the eccentric section (13) and the pump elements (23) a ring (15) is arranged, that the ring (15) on the eccentric section (13) by a second slide bearing (17) is mounted, and that the second slide bearing (17) is forcibly flowed through by fuel.

3. Radial piston pump according to claim 1 or 2, characterized in that the first sliding bearing (7) and / or the second sliding bearing (17) is flowed through by the fuel flowing through the fuel connection (31).

4. Radial piston pump according to claim 1 or 2, characterized in that the first slide bearing (7) and / or the second slide bearing (17) is flowed through by the pump elements (23) delivered under high pressure fuel.

5. Radial piston pump according to one of the preceding claims, characterized in that the first slide bearing (7) has at least one lubricating groove (33) extending essentially in the direction of the axis of rotation (47) of the drive shaft (3).

6. Radial piston pump according to one of the preceding claims, characterized in that the stub shaft (5) has a central bore (39) that branches off from the central bore (39), a transverse bore (41), and that the second plain bearing (17) from the transverse bore (41) is supplied with fuel.

7. Radial piston pump according to one of claims 4 to 6, characterized in that the second slide bearing (17) at least one substantially in the direction of the axis of rotation

(47) of the drive shaft (3) extending lubrication groove (45).

6. Radial piston pump according to claim 7, characterized in that there is a hydraulic connection between the at least one lubrication groove (45) and an interior (35) of the pump housing (1) on the side of the second slide bearing (17) facing away from the shaft end (5).

9. Radial piston pump according to one of claims 6 to 8, characterized in that the eccentric section (13) or the ring (15) has an annular groove (43), and that the transverse bore (41) opens into the annular groove (43).

10. Radial piston pump according to one of claims 6 to 9, characterized in that an impeller (49) of a micropump is inserted into the central bore (39).

11. Radial piston pump according to one of the preceding claims, characterized in that the fuel connection (31) opens into the interior (35) of the pump housing (1).

12. Radial piston pump according to one of claims 1 to 11, characterized in that the fuel connection (31) opens into the first slide bearing (7).

13. Radial piston pump according to one of claims 1 to 12, characterized in that the lubrication groove (33) on the stub shaft (5) of the drive shaft (3) is arranged.

14. Radial piston pump according to one of claims 1 to 12, characterized in that the lubrication groove (33) on the bush (37) of the first plain bearing (7) is arranged.

15. Radial piston pump according to one of claims 1 to 14, characterized in that the lubrication groove (45) on the eccentric section (13) of the drive shaft (3) is arranged.

16. Radial piston pump according to one of claims 1 to 14, characterized in that the lubrication groove (45) is arranged on the eccentric section and extends over a first angular range 57 of approximately 60 °.

17. Radial piston pump according to claim 16, characterized in that the central axis (23-1) of the first angular range is offset by approximately 90 ° from the point of maximum eccentricity of the eccentric section (13).

18. Radial piston pump according to one of the preceding claims, characterized in that the lubricating groove (33) on the stub shaft (5) is arranged in a second angular region (59), and in that the second angular region (59) is approximately 180 ° to the first angular region (57 ) is arranged offset.

19. Radial piston pump according to one of the preceding claims, characterized in that the lubrication groove (33) on the stub shaft (5) and / or the lubrication groove (45) on the eccentric section (13) are designed helically.