JP2000038972A - Radial piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the transmission of an eccentrical shaft movement to each piston constant when revolutions are high, and when each cylinder chamber is partially full of fuel. SOLUTION: A ring is pivoted in such a way as to be movingly slipped over a shaft division 1 eccentrically formed with respect to a driving shaft. This ring is cooperated with plural pistons 5, 6, and 7 disposed in the inside of respective cylinder chambers in the radial direction with respect to the driving shaft in such a way that they can be reciprocated in the radial direction in the inside of the respective cylinder chambers. The ring is divided into plural ring segments 2, 3 and 4. Each ring segment 2, 3 and 4 is interposed between each piston 5, 6 and 7 and the driving shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial piston pump for generating a high fuel pressure in a fuel injection system of an internal combustion engine, in particular, a common rail injection system, wherein a drive shaft supported in a casing is eccentric. A ring is mounted on the shaft section for sliding movement, the ring being arranged radially with respect to the drive shaft in the respective cylinder chamber. Cooperating with a plurality of pistons, said pistons being reciprocally movable in a radial direction in respective cylinder chambers by rotation of a drive shaft.

[0002]

2. Description of the Related Art In such radially supported radial piston pumps, in each case the base of the piston comes into contact with a ring mounted on a drive shaft. The piston is moved back and forth sequentially due to the eccentricity of the drive shaft. In this case, the stroke of the piston is constant and equal to twice the eccentric distance of the drive shaft.

In order to increase the efficiency of the internal combustion engine, it has been proposed to control the amount of fuel delivered into each cylinder chamber by means of a metering unit. If the cylinder is partially filled with fuel, the ring may tilt, especially at high rotational speeds, which may cause the piston to separate from the ring. In the worst case, the radial piston pump may fail.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radial piston pump which overcomes the aforementioned disadvantages. In particular, the transmission of the eccentric shaft movement to the piston during a high filling speed and partial filling of the cylinder chamber is invariably possible.

[0005]

According to the present invention, there is provided a radial piston pump for generating high fuel pressure in a fuel injection system of an internal combustion engine, in particular a common rail injection system, which is mounted in a casing. The drive shaft has an eccentrically configured shaft section, on which a ring is mounted for sliding movement, the ring being arranged radially with respect to the drive shaft in each cylinder. Co-operating with a plurality of pistons arranged in the room,
These pistons are reciprocally movable in a radial direction in respective cylinder chambers by rotation of a drive shaft. A ring is divided into a plurality of ring segments, and one ring is provided between each piston and the drive shaft. The solution is achieved by providing one ring segment. In pumps with multiple pistons, it is not possible to achieve a pure rolling motion with an integral ring, since the rolling motion between the piston base and the ring segment is partially reversed. . In pumps having multiple pistons, the introduction of piston motion through an integral ring causes opposing sliding motion between the ring and the piston base, which can result in significant slip wear. By dividing the ring into one ring segment for each piston,
These ring segments can perform a pure rolling motion independently of one another at the piston base belonging to them. There is no sliding movement between the piston base and the ring segment that leads to wear.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In one particular embodiment of the present invention,
The ring segments are circumferentially spaced from one another.
In this case, the spacing between the ring segments is advantageously chosen so that the ring segments can carry out the above-mentioned opposite movements.

In another particular embodiment of the invention, the coefficient of friction between the piston base and its associated ring segment is greater than the coefficient of friction between the drive shaft and the ring segment. This advantageously ensures that a pure rolling movement takes place between the piston base and the ring segment. On the other hand, a relative rotation takes place between the eccentrically arranged shaft section and the ring segment, which can be improved by forming a sliding bearing.

In another particular embodiment of the invention, the piston base or ring segment is provided with a groove,
This groove serves to receive the O-ring. The O-ring increases the coefficient of friction between the piston base and the associated ring segment.

[0009] In another particular embodiment of the invention, the surface or ring segment of the piston base facing the drive shaft is at least partially rubberized. The rubber coating forces a pure rolling motion between the piston base and the associated ring segment. Without such means, the ring segments may have a combined sliding and rolling motion at the piston base. However, the additional slippage results in a high sliding wear due to the operating load. If pure rolling motion takes place between the piston base and the associated ring segment, the operating load acts between the piston base and the ring segment in the form of a simple surface pressure. There is no sliding movement that causes attrition. Therefore, the ring segment and the piston base associated therewith need only be configured to withstand the surface pressure. The rotary movement and the sliding movement generated by the drive shaft of the radial piston pump are advantageously limited to the bearing between the eccentrically configured shaft section and the ring segment.

In another particular embodiment of the invention, a stop for the ring segments is mounted on the casing between the ring segments. These stops allow the tangential working range of the ring segment to be determined in an advantageous manner.

[0011] In another particular embodiment of the invention, in each ring segment two stops are provided for the piston base belonging to each ring segment. This solution is simple and inexpensive. The working range of the ring segment in the tangential direction is determined by a stopper formed on the ring segment itself.

In another particular embodiment of the invention, the piston is connected to a ring segment belonging to it. This measure prevents the individual ring segments from hitting each other during operation, as in the case of the stop described above. Furthermore, this connection ensures a defined rolling movement between the piston base and the ring segment.

[0013] In another particular embodiment of the invention, the piston base is configured as a plate. This increases the surface of the piston base. This has the advantage that a larger area is available for the rolling movement.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be specifically described below with reference to the embodiments shown in the drawings.

The radial piston pump shown in section in FIG. 1 is used in particular in a common-rail injection system for supplying fuel to diesel engines. In this case, “common rail” means “common conduit”. Unlike conventional high pressure injection systems where fuel is sent to the individual combustion chambers via separate conduits, the injection nozzles of the common rail injection system are supplied with fuel from a common conduit. The illustrated radial piston pump has a built-in required volume regulator. The supply and metering of the fuel takes place via a metering unit, not shown.

The radial piston pump shown in FIG.
It has a drive shaft mounted in a pump housing, not shown, which has an eccentrically shaped shaft section 1. On the eccentric shaft section 1, three ring segments 2, 3 and 4 are provided, with which the shaft section 1 is rotatable relative to these ring segments.
Each ring segment 2, 3 and 4 cooperates with one piston 5, 6 and 7, respectively. At the base of the pistons 5, 6 and 7, one plate 8, 9 and 10, respectively, is formed. Each plate 8, 9 and 10 is 1
The two ring segments 2, 3 and 4 are in contact. A sliding bearing 11 is formed between the eccentric shaft section 1 and the ring segments 2, 3 and 4.

The radial piston pump, shown only schematically in FIG. 1, serves to apply a high pressure to the fuel supplied from the tank by the pre-transport pump. The high pressure loaded fuel is then sent into the aforementioned common conduit. During the conveying stroke, the pistons 5, 6 and 7 are moved from the eccentric shaft section 1 via the ring segments 2, 3 and 4 to the pistons 5, 6 and 7, respectively.
And 7 are moved outward in a direction away from the axis of the drive shaft. During the suction stroke, the pistons 5, 6 and 7 move radially towards the axis of the drive shaft to draw fuel. This suction movement of the pistons 5, 6 and 7 is achieved by springs, not shown, which are pre-loaded against the plates 8, 9 and 10.

As can be seen in FIG. 1, three stops 17, 18, and 19 are mounted for the ring segments 2, 3, and 4 on the pump housing, schematically illustrated by three fixed bearings 14, 15, and 16. ing. These stops 17, 18, and 19 limit the tangential working range of the individual ring segments 2, 3, and 4. If one of the ring segments 2, 3 and 4 slips out of its desired position during operation, this ring segment is automatically returned to the target position by the stops 17, 18 and 19. By appropriately matching the friction coefficients between the plates 8, 9 and 10, the ring segments 2, 3 and 4 and the eccentric shaft section 1, the ring segments 2, 3 and 4 allow the plates 8, 9 and A pure rolling motion with respect to 10 is guaranteed.

FIG. 2 is a partial cross-sectional view of a radial piston pump according to a second embodiment of the present invention, which is vertical to the drive shaft of the radial piston pump. The eccentric shaft section 20 is rotatably mounted relative to the ring segment 21. A plate 22 is supported on the ring segment 21 and is fixed to a piston 23. Arrow 29 indicates the force acting on the piston during operation. This force is generated during the suction stroke by a spring, not shown, which is preloaded against the plate 22. During the transport stroke of the radial piston pump, a reaction force of the compressed fuel acts in the direction of arrow 29. Force flows are schematically illustrated by lines 24 and 25. At the edge of the force flow area, a groove 26 is cut out on the surface of the plate 22 facing the ring segment 21. A ring 28 made of an elastomeric plastic material is arranged in the groove 26. The size of the ring 28 is larger than the size of the groove 26. This allows plate 2
A large coefficient of friction between 2 and ring segment 21 is guaranteed.

FIG. 3 shows a diagram similar to FIG. In FIG. 3, a code obtained by adding 10 to the code of FIG. 2 is entered. To avoid repetition, a detailed description of FIG. 3 is omitted. The only difference between FIG. 3 and FIG. 2 is that the groove 36 is arranged in the ring segment 31 and not in the plate 32. The ring 38 located in the groove 36 performs the same function as the ring 28 in FIG.

FIG. 4 shows a diagram similar to FIG. The eccentric shaft section 40 is rotatably supported by slide bearings 41 relative to the ring segments 42, 43 and 44. Ring segment 4
2, 43 and 44 are in contact with plates 48, 49 and 50 formed on pistons 445, 46 and 47. Ring segments 42, 43 and 44 have radially extending stops 51, 52; 53, 54 and 55,
56 are configured. These stops 51 to 56 limit the movement of the ring segments 42 to 44 in the tangential direction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in a direction transverse to a drive shaft of a radial piston pump according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view in a vertical direction with respect to a drive shaft of a radial piston pump according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view in a vertical direction with respect to a drive shaft of a radial piston pump according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of a radial piston pump according to a fourth embodiment of the present invention, taken in a direction transverse to a drive shaft.

[Explanation of symbols]

1 axis section, 2, 3 and 4 ring segments,
5, 6, and 7 pistons, 8, 9, and 10 plates, 11 plain bearings, 14, 15, and 16 fixed bearings, 17, 18, and 19 stoppers, 20 shaft sections, 21 ring segments, 22 plates,
23 pistons, 24 and 25 lines, 26 grooves,
28 ring, 29 arrow, 30 axis section, 31
Ring segment, 32 plate, 33 piston, 34 and 35 line, 36 groove, 38 ring, 39 arrow, 40 shaft section, 41 sliding bearing, 42, 43 and 44 ring segment, 4
5, 46 and 47 pistons, 48, 49 and 50
Plates, 51, 52; 53, 54 and 55, 56
Stopper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F04B 9/02 F04B 9/02 C (72) Inventor Liner Heveler Bretten Eichenstrasse 32 Germany (72) Inventor Helmut Klaus Germany Eberdingen a Ugst-Remle-Strase 38

Claims (9)

[Claims] 1. A radial piston pump for generating high fuel pressure in a fuel injection system of an internal combustion engine, particularly a common rail injection system, wherein a drive shaft supported in a casing is formed eccentrically. A ring is mounted on this shaft section for sliding movement, which ring is arranged in particular in each cylinder chamber radially with respect to the drive shaft, in particular a plurality of pistons (5). , 6,7) in which the pistons are reciprocally movable in the radial direction in the respective cylinder chambers by rotation of the drive shaft, wherein the ring comprises a plurality of ring segments (2,3,4). Characterized in that one ring segment (2,3,4) is provided between each piston (5,6,7) and the drive shaft, respectively. Piston pump. 2. The radial piston pump according to claim 1, wherein the ring segments are circumferentially spaced from one another. 3. The friction coefficient between the piston base (8, 9, 10) and the associated ring segment (2, 3, 4) is determined by the drive shaft (1) and the ring segment (2, 3, 4).
The radial piston pump according to claim 1, wherein the radial piston pump has a coefficient of friction larger than the radial piston pump. 4. The piston base (22) or the ring segment (31) is formed with at least one groove (26; 36) which serves to receive the O-ring (28; 38). A radial piston pump according to any one of claims 1 to 3, characterized in that: 5. The piston shaft according to claim 1, wherein the surface of the piston base facing the drive shaft or the ring segment is at least partially rubber-coated. Radial piston pump according to the item. 6. A casing (1) between ring segments.
6. The method according to claim 1, wherein the at least one of the ring segments has a stop for the ring segment. Radial piston pump. 7. Each ring segment (42, 43, 4)
4), two stoppers (51, 52; 53, 54; 5)
Radial piston according to one of the preceding claims, characterized in that the radial piston (5, 56) is configured for a piston base (48, 49, 50) belonging to each ring segment. pump. 8. The method according to claim 1, wherein the piston is connected to a ring segment belonging to the piston.
The radial piston pump according to any one of claims 1 to 5. 9. The piston base is provided with a plate (8, 9, 1).
0).
The radial piston pump according to any one of claims 1 to 8.