EP1415092A1

EP1415092A1 - High pressure feed pump

Info

Publication number: EP1415092A1
Application number: EP02742623A
Authority: EP
Inventors: Fritz Spinnler
Original assignee: CRT Common Rail Technologies AG; CRT Common Rail Tech AG
Current assignee: CRT Common Rail Technologies AG; CRT Common Rail Tech AG
Priority date: 2001-08-08
Filing date: 2002-07-09
Publication date: 2004-05-06
Also published as: US20040156733A1; JP2004537005A; WO2003014569A1; CN1539060A; KR20040035730A

Abstract

The invention relates to a high pressure feed pump which comprises a delivery plunger (14) guided within a high pressure cylinder. Said delivery plunger is driven by a drive shaft (28) by way of an eccentric (36) on which a rounded-off multi-stage ring (40) is rotatably received. A plate-shaped spring element (62) is disposed between the multi-stage ring (40) and the delivery plunger (14) and is, for example, configured by the bottom (48) of a bucket tappet (46). The delivery plunger (14) has a concavely shaped section on its front end (50), thereby allowing the spring element (62) to bend into the recess (64) in accordance with the load on the delivery plunger (14). The contact surface (54) of the spring element (62) with the multi-stage ring (40) and the annular surface (62) with which the spring element (62) rests on the delivery plunger (14) is thereby increased. Surface pressure can thus be restricted to an acceptable degree even at very high working pressures.

Description

Hochdruσkförderpumpe

The present invention relates to a high-pressure feed pump with the features of the preamble of patent claim 1.

Such high-pressure feed pumps operating according to the reciprocating piston principle are used in particular for generating the injection pressure in fuel injection systems - e.g. Common rail systems - used for internal combustion engines. A generic high pressure feed pump is disclosed in EP-A-1 058 001.

High-pressure feed pumps of the generic type have a high-pressure cylinder or plunger cylinder and a cylindrical feed piston or plunger piston which can be reciprocated therein, the volume of the delivery space within the high-pressure cylinder being changed by the stroke movement of the plunger piston. During a filling stroke of the plunger, the delivery space can be connected via a filling valve to a storage space for a delivery medium, in order to fill the delivery space, which increases in displacement, with the delivery medium. During a subsequent delivery stroke with the filling valve closed, the pressure in the delivery chamber increases until a pressure valve opens and thereby connects the delivery chamber to a high-pressure room, for example the Cornmon Rail.

The plunger is driven by an eccentric drive, which comprises an eccentric mounted on an eccentric shaft, on which a rolling ring is rotatably mounted. To reduce its moment of inertia, it has a convex circumferential surface. During the rotation of the The eccentric bears the delivery piston biased in the direction against the eccentric shaft with a plate-like extension provided on its end on this side of the rolling ring. During operation, the rolling ring rotates back and forth and changes its direction of rotation twice per revolution of the eccentric shaft. The design and mode of operation of the high-pressure pump is described in EP-A-1 058 001, the disclosure of which is expressly made the content of the present application by this reference.

In the case of high-pressure feed pumps of the type mentioned, in particular if they are used for diesel injection systems, the material loads in the areas of contact between the rolling ring and the delivery piston are high. As a result, either the delivery pressures achievable with such pumps are limited, or the elements in question are dimensioned large.

It is therefore an object of the present invention to provide a high-pressure feed pump which overcomes the problems mentioned.

This object is achieved with a generic high-pressure feed pump, which has the features in the characterizing part of claim 1.

In a high-pressure feed pump according to the invention, the Hertz surface pressure between the rolling ring and the delivery piston (plunger) is considerably reduced in comparison with known high-pressure feed pumps. This is because, due to a plate-like spring element, a load-dependent adaptation to the curvature of the rolling ring takes place; the contact area between the rolling ring and the spring element moved with the delivery piston will increase with The load is also greater, which keeps the Hertz 'surface pressure between the rolling ring and the spring element as well as between this and the delivery piston within acceptable limits, even at very high delivery pressures.

Preferred embodiments of the high-pressure feed pump according to the invention are specified in the dependent claims.

The invention is explained in more detail with reference to the embodiments shown in the drawing. It shows purely schematically:

Fig. 1 shows a cross section through an inventive

High-pressure feed pump along the section line I-I of Fig. 2;

FIG. 2 shows the high-pressure feed pump shown in FIG. 1 in a longitudinal section along the line II-II of FIG. 1;

3 shows a partial section of part of the high-pressure feed pump shown in FIGS. 1 and 2 with a delivery piston which is concavely shaped on the end face and which rests on a bucket tappet, which on the other hand interacts with a rolling ring of a drive shaft;

4 shows, in the same representation as FIG. 3, a further embodiment of the high-pressure feed pump according to the invention with an adapter head movably mounted on a shaft of the feed piston;

5 shows a section along the line VV of the embodiment shown in FIG. 4; and 6, in the same representation as FIG. 3, a further embodiment in which the delivery piston is flat on the end face and the cup tappet has a concave recess.

1 and 2 show a cross section and a longitudinal section through a high-pressure feed pump with a housing 10, into which a high-pressure cylinder 12, also called a plunger cylinder, is inserted, in which a delivery piston 14, also called a plunger piston, is located in the direction of the longitudinal axis 14 '. can move back and forth. The high-pressure cylinder 12 is clamped with a flange-like extension between the housing 10 and a valve housing 16. The valve housing 16 is screwed to the housing 10 by means of screw bolts 17. An inlet valve 18 and an outlet valve 20 are provided in the valve housing 16. The inlet valve 18 opens and closes a passage 22 to a storage container for the medium to be conveyed and the outlet valve 20 opens a passage 24 to a high-pressure container. In the case of a high-pressure injection system for internal combustion engines, fuel, such as diesel or gasoline, is located in the storage container, and the high-pressure container is, for example, a common rail.

An eccentric drive 26 for driving the delivery piston 14 is also arranged in the housing 10 of the high-pressure feed pump. This has a drive shaft 28 continuously driven in the direction of the arrow, which is mounted in a generally known manner, freely rotatable about a rotation axis 30 on the housing 10 and a cover 32 closing it, via bearings, not shown. The drive shaft 28 carries between the bearing points 34, 34 'an eccentric pin 36 arranged eccentrically with respect to the axis of rotation 30 of the drive shaft 28, the center axis 38 of which runs parallel to the axis of rotation 30. On a rolling ring 40 is rotatably mounted with respect to the eccentric pin 36. The radially outer circumferential surface 42 of the rolling ring 40 is domed, that is, convex.

In a circular-cylindrical through bore 44 of the high-pressure cylinder 12, the delivery piston 14 is guided in a sealingly sliding manner. It engages with its end region facing the drive shaft 28 into a cup tappet 46, on the bottom 48 of which it rests with the end face 50 of a mushroom or plate-like extension 52. The cup tappet 46, on the other hand, rests on the rolling ring 40 with its base 48. The reference numeral 54 designates the point of contact or contact area between the rolling ring 40 and the bottom 48 of the cup pusher 46. The delivery piston 14 is moved in the opposite direction by means of a compression spring 56, which is supported on the one hand on the high pressure cylinder 12 and on the other hand on the extension 52 the rolling ring 40 biased.

The cup tappet 46 is guided with its jacket 58 on the housing 10 in the longitudinal direction and thus the direction of movement of the delivery piston 14. The transverse forces acting on the bucket tappet 46 from the drive shaft 28 and the rolling ring 40 are absorbed by the bucket tappet 46 and are not or only transmitted to the delivery piston 14 to a very small extent.

To compress and convey the medium, the delivery piston 14 is moved up and down by the eccentric drive 26 and the compression spring 56. When the delivery piston 14 moves downwards during a filling stroke, the delivery space 60 fills with the delivery medium via the inlet valve 18. If the delivery piston 14 moves upwards during the subsequent delivery stroke, the pressure in the delivery Room 60 with the inlet valve 18 closed until the outlet valve 20 opens and thereby connects the delivery chamber 60 to the high-pressure tank (common rail). The medium is pumped into the high pressure tank.

3 shows, with reference to FIGS. 1 and 2, enlarged, the delivery piston 14, the compression spring 56, the cup tappet 46, the rolling ring 40 and part of the drive shaft 28 which can be driven in the direction of the arrow, with the eccentric pin 36.

The cup tappet 46 is preferably made from hardened roller bearing steel. The plate-shaped bottom 48 of the cup tappet 46, which is flat in the unloaded state, has spring properties and, when interacting, serves on the one hand with the cambered circumferential surface 42 of the rolling ring 40 and on the other hand the concave end face 50 of the delivery piston 14 as a spring element 62 can be shaped, for example, as a cap or part of the lateral surface of a torus. Around the recess 64, the end face 50 of the delivery piston 14 has a flat annular surface 66, with which it rests on the bottom 48 in the unloaded or slightly loaded state and which, depending on the shape of the recess 64, can have an annular, oval or other shape ,

The aim should be that the longitudinal axis 14 ′ of the delivery piston 14 runs centrally to the recess 64 or ring surface 66 and to the cup tappet 46. Further, the axis 14 'runs in a preferred manner in a direction perpendicular to Rotati ^¬ onsachse 30 of the drive shaft 28 extending plane, which extends centrally through the contact surface 54th

Depending on the load on the delivery piston 14, the base 48, which acts as a spring element 62, bends of the cup tappet 46 into the recess 64 in such a way that, as the load increases, on the one hand the contact surface 54 between the base 48 and the rolling ring 40 and on the other hand the surface over which the base 48 bears against the delivery piston 14 are increased. As a result, the Hertz 'see surface pressure in the relevant parts is kept within limits, which enable a long service life of the high-pressure feed pump. The base 48 is preferably dimensioned in such a way that it rests over the entire area in the recess 64 on the delivery piston 14 when there is a certain load.

In the embodiment shown in FIGS. 4 and 5, only the delivery piston 14 is different in comparison with the embodiment shown in FIGS. 1 to 3. The mode of operation is the same as described above. Therefore, only the formation of the delivery piston 14 will be discussed.

The delivery piston 14 shown in FIGS. 4 and 5 has a shaft 68, on the hemispherically shaped end region facing the rolling ring 40, an essentially circular-cylindrical adapter 70 is seated. The end face 50 of the adapter 70 which cooperates with the bottom 48 of the cup tappet 46 is of the same design as that of the delivery plunger 14 according to FIG. 3. A recess 72 in the adapter 70 for receiving the end region of the shaft 68 on this side is of the same shape and shape has a circumferential groove 74 in a cylindrical casing part adjoining the hemisphere surface. Correspondingly, the shaft 68 is provided with a circumferential groove 76. As can be seen in particular in FIG. 5, a straight through bore 78 runs through the adapter 70, the axis of which extends through the circular center line of the toroidal one delimited by the groove 74 and the circumferential groove 76 Affects space. A section of a securing element formed from spring steel wire 80 runs through the through hole 78 and runs around it with a further section for attachment to the adapter 70. In this way, the adapter 70 is mounted on the shaft 68 with limited movement in a spherical manner. This enables only axial forces and no bending forces to act on the delivery piston 14.

The compression spring 56 is supported on a flange ring 82 which engages around two half flanges 84 and is in turn supported on these. The half flanges 84 engage with a bead 86 in a circumferential groove of the shaft 68 and are fastened to the shaft 68 in this way in the axial direction.

The embodiment of the high-pressure feed pump according to the invention shown in FIG. 6 is very similar to that according to FIG. 3, the valve body 14 being flat on its end face 50 and the bottom 48 of the cup tappet 46 through a recess 64 'on that of the feed piston 14 facing side is concave. Here, too, in the unloaded and slightly loaded state, the delivery piston 14 rests with an annular surface 66 on the bottom 48 of the cup tappet 46 acting as a spring element 62. The mode of operation is the same as described above in connection with the other embodiments.

In the embodiment shown in FIG. 6, the delivery piston 14 can be configured in the same way as shown in FIG. 3 or 4.

Preferably, the transition between the annular surface 66 and the recess 64 'itself is shaped in such a way according to the spring characteristic of the spring element 62 that, as the load increases, the surface with which rather the spring element rests on the delivery piston, increases continuously.

The recess 64 'can be matched to the coating of the rolling ring 40 in such a way that in the recess 64' at least approximately over the entire area of the spring element 62, this also bears against this over at least approximately the entire width of the rolling ring 40.

Claims

claims

1. High-pressure delivery pump with a high-pressure cylinder (12), a delivery piston (14) guided therein, and an eccentric (36) arranged on a drive shaft (28), on which a rolling ring (40) having a cambered peripheral surface (42) for the Drive of the feed piston (14) is rotatably mounted, characterized in that a plate-like spring element (62) is arranged between the feed piston (14) and the rolling ring (40), which on the one hand has a contact surface (54) on the peripheral surface (42) of the Rolling ring (40) and on the other hand abuts an annular surface (66) on the end face (50) of the delivery piston (14).

2. High-pressure feed pump according to claim 1, characterized in that the delivery piston (14) is concave on its end face (50).

3. High pressure feed pump according to claim 1 or 2, characterized in that the spring element (62) is concave on its side facing the feed piston (14).

4. High-pressure feed pump according to one of claims 1 to 3, characterized in that the feed piston (14) has a mushroom-shaped or plate-shaped extension (52) in its end region facing the spring element (62).

5. High-pressure feed pump according to claim 3, characterized in that the extension (52) by one, pre- is preferably formed on a shaft (68) of the delivery piston (14) movably mounted adapter (70).

6. High-pressure feed pump according to one of claims 1 to 5, characterized in that the spring element (62) through the bottom (48) of a with its cylindrical outer surface (58) in the direction of movement of the delivery piston (14) guided tappet (46) is formed.

7. High pressure feed pump according to one of claims 1 to 6, characterized in that the spring element (62)

- At maximum pressure load - with the area opposite the contact surface (54) lies flat against the end face (50) of the delivery piston (14).