EP1906011B1 - Fluid pump, in particular high pressure fuel pump for injection systems in combustion engines - Google Patents

Description

The present invention relates to a fluid pump, in particular high-pressure fuel pump for injection systems of internal combustion engines, according to the preamble of claim 1.

Such a fluid pump is for example from the DE 100 39 210 A1 and comprises a pump piston, which is guided for reciprocating movement in the direction of a pump piston axis in a pump cylinder, and a sleeve-shaped support body, which is guided on an outer peripheral surface of the pump cylinder in the direction of the pump piston axis and is in driving connection with the pump piston. The arrangement of the sleeve-shaped support body has the advantage that it can be introduced directly into a more or less rigid and rigid pump cylinder during operation of the pump transverse to the pump piston axis occurring transverse forces. On the pump piston then act only forces in the direction of the pump piston axis, which drive the piston to reciprocate. In the known pump, the intrinsically undesirable transverse forces are generated by an eccentric, in which an eccentric performs a wobbling movement and a connected to the pump piston shoe not only charged for the desired stroke of the pump piston in the direction of the pump piston axis, but also introduces lateral forces in the shoe ,

The known pump has a number of disadvantages. In the first place here is the relatively complex manner realized connection of the shoe on the one hand with the pump piston and on the other hand with the sleeve-shaped support body call. The connection is accomplished by a first and a second part, wherein the first part is fixedly connected to one end of the pumping piston (eg by means of a press fit) and in positive connection with the second part, which in turn is in positive connection with a shoulder of the pump sleeve-shaped support body is. Depending on the specific design here is also a special design of the pumping piston end and / or the sleeve-shaped support body required. In view of the confined space conditions as well as the desire for the least possible moving mass, the two connecting parts should be relatively small dimensions. However, this adversely affects the reliability or fatigue strength of the connection.

The publication US Pat. No. 4,355,546 is considered to be the closest prior art and discloses a fluid pump for injection systems of internal combustion engines, with at least one pump piston which is guided for reciprocating movement in the direction of a pump piston axis in a pump cylinder, and with a sleeve-shaped support body which is guided in the direction of the pump piston axis and is in driving connection with the pump piston, wherein the pump piston has an integrally formed with the pump piston, broadened pump piston foot and the driving connection is realized by a retaining ring which is partially disposed in an outer circumferential groove of the pump piston, the pump piston has a widened first foot portion of which the outer circumferential groove is arranged for the retaining ring.

It is an object of the present invention to easily and reliably form the driving connection between the pump cylinder and the sleeve-shaped support body in a fluid pump of the type mentioned.

This object is achieved by a fluid pump with the features of claim 1. The dependent claims relate to advantageous developments of the invention.

The fluid pump according to the invention is characterized in that the sleeve-shaped support body is guided on an outer peripheral surface of the pump cylinder, the retaining ring is partially disposed in an inner circumferential groove of the sleeve-shaped support body, wherein the pump piston also further an adjoining, projecting beyond one end of the sleeve-shaped support body, even further widened second foot portion, on which rests the end of the sleeve-shaped support body.

It is important for the invention, first, that the pump piston has an integrally formed with the pump piston, widened pump piston foot, which thus no longer a realized by separate parts connection with the actual pump piston or pump piston body (which goes back and forth in the pump cylinder) and advantageous even replace the shoe of the known construction. It is also essential for the invention that this one-piece design of a widened pump piston foot is simultaneously used for a particularly simple connection to the sleeve-shaped support body, which is realized by means of a securing ring.

It is noteworthy that, in comparison with the known pump construction with the invention, not only a plurality of expensive components to be manufactured and assembled are saved In addition, in practice, the reliability and durability of the construction can be improved.

Finally, the above-mentioned special design of the pump piston foot with the widened first foot section and an adjoining, even further widened second foot section, which are used in the manner described above, are essential for the invention. This can also z. For example, it can be achieved that a force introduced by a pump drive (eg eccentric drive) onto the pump piston foot in the direction of the pump piston axis in one direction (which normally corresponds to the so-called pump stroke) is largely or even substantially completely not via the securing ring, but instead the support of the support body is transmitted to the second body portion on the support body. For the driving connection in the opposite direction (suction stroke) also satisfies a relatively small dimensioned circlip connection, since the forces occurring in this stroke are usually relatively small.

In the context of the invention there is advantageously a great deal of freedom with regard to the shaping of both the sleeve-shaped support body and the integrally formed pump piston foot.

In particular, the construction according to the invention is compatible with very simply designed supporting bodies, since only one inner peripheral groove is to be provided on the supporting body, but the rest of the design is very variable.

With regard to the design of the pump piston foot is important that this shape can be optimally adapted to the expected during operation mechanical loads. In one embodiment, it is provided that the pump piston together with its pump piston foot is produced as a rotationally symmetrical milled part. Thus, the respective mechanical loads optimally adapted or weight-optimized pump piston can be formed inexpensively together with its outer circumferential groove. If necessary, subsequent machining of the pump piston foot can then take place, in particular in those areas which later come into contact with an eccentric drive component of the pump, which, however, does not represent any appreciable additional expenditure.

The invention is particularly suitable for use in a so-called radial piston pump, in particular a radial piston pump with a plurality of pump pistons, the z. B. can be arranged in a common plane. In one embodiment, for example, it is provided that the pump comprises an eccentric shaft for driving a plurality of conveyor units accommodated in a pump housing, each of which has a pump piston guided for reciprocating movement in the direction of a respective pump piston axis in a respectively associated pump cylinder.

In one embodiment, it is provided that the sleeve-shaped support body is guided substantially free of play on the outer peripheral surface of the pump cylinder. This can be z. B. accomplish in a simple manner by a cylindrical inner peripheral surface portion of the sleeve-shaped support body slides on a corresponding cylindrical outer peripheral surface portion of the pump cylinder. For this purpose, for. B. the relevant sections of the support body as well each of the pump cylinder have a hollow cylindrical shape.

In a particularly preferred embodiment, it is provided that the outer circumferential groove of the pump piston foot and the inner peripheral groove of the sleeve-shaped supporting body are substantially directly adjacent to one another. This advantageously results in a very direct introduction of acting on the pump piston stem transverse forces in the support body and a particularly resilient entrainment of these two components in the direction of the pump piston axis. If the outer peripheral groove of the pump piston foot and the inner circumferential groove of the sleeve-shaped support body are not adjacent to each other directly or slightly spaced, it is preferred that the material of the locking ring is arranged in the two grooves at least 90% in the direction of the pump piston axis (and accordingly at most 10) % is located outside the grooves).

In a preferred embodiment, the retaining ring extends continuously over at least 70% of the circumferential length of the two grooves, the retaining ring preferably having a uniform cross-section (eg rectangular or circular) along its continuous circumferential extent.

The maximum extent of the securing ring in the direction of the pump piston axis is preferably at least as great as the maximum extent of the securing ring in the transverse direction (orthogonal to the pump piston axis).

The locking ring can be formed in a particularly simple manner as a so-called snap ring or Seeger ring.

In known manner may be provided in the pump acting in the direction of the pump piston axis between the pump cylinder and the pump piston return spring, which biases the pump piston in the direction of the intake stroke. In this case, only the force acting in the direction of the pumping stroke must be exerted by the pump drive.

The above-mentioned return spring may be formed as a spiral compression spring and surrounding the sleeve-shaped support body, wherein the coil spring can be supported in the direction of the pump piston axis on the one hand on a shoulder of the pump cylinder or a housing portion and on the other hand on a shoulder of the sleeve-shaped support body. This usually requires a suitably adapted shape design of the support body. As in the invention, however, a widened pump piston foot is provided anyway, the second-mentioned support of the return spring can also be advantageous be provided directly on an outer peripheral region of the pump piston. For this purpose, in particular the training described above is well suited, in which one end of the sleeve-shaped support body rests on the pump piston or its second foot section. In one embodiment, for. B. provided that the return spring is supported on the one hand on a shoulder of the pump cylinder and on the other hand on the second foot portion.

Fig. 1

ist eine schematische Teilschnittansicht einer Fördereinheit einer Radialkolbenpumpe nach dem Stand der Technik, und

Fig. 2

ist eine der Fig. 1 entsprechende Ansicht einer Fördereinheit einer Radialkolbenpumpe gemäß eines Ausführungsbeispiels der Erfindung.

The invention will be further described by means of an embodiment with reference to the accompanying drawings. They show:

Fig. 1

is a schematic partial sectional view of a feed unit of a radial piston pump according to the prior art, and

Fig. 2

is one of the Fig. 1 corresponding view of a delivery unit of a radial piston pump according to an embodiment of the invention.

Fig. 1 illustrates the known construction of a delivery unit 1 of a high-pressure fuel pump, as it z. B. from the DE 100 39 210 A1 is known and described in detail there.

The illustrated delivery unit 1 is one of several pump delivery units that are operated by a shared eccentric shaft (not shown). The feed unit 1 is used to fuel (eg, diesel for a storage injection system) from a supply line 2 (suction) via a first check valve 3 in a pump working space 4 and then via a second check valve 5 with high Pressure (eg over 1,500 bar) in a discharge line 6 (pressure chamber) to promote.

The described components are housed in a housing structure, of which in Fig. 1 a first housing part 7 and a second housing part 8 can be seen.

The pump further comprises a pump piston 10, which is guided for reciprocating movement in the direction of a pump piston axis A in a pump cylinder 12, during a Saubhubs (in Fig. 1 Down) to promote fuel from the supply line 2 via the check valve 3 in the pump chamber 4 and during a pumping stroke (in Fig. 1 to top) to compress the fuel located in the pump working space 4 or to deliver via the check valve 5 under high pressure to the pressure chamber 6.

The pump cylinder 12 is in the illustrated embodiment, an integrally projecting from the housing part 8 and projecting into a cylindrical recess of the housing part 7 section.

Furthermore, the pump comprises a sleeve-shaped support body 14, which is guided on an outer peripheral surface of the pump cylinder 12 in the direction of the pump piston axis A and by means of a connection arrangement 16 is in driving connection with the pump piston 10.

When the eccentric shaft rotates, an eccentric ring 18 penetrated by an eccentric section of the eccentric shaft performs a tumbling motion whose component is transmitted to the pump piston 10 parallel to the pump piston axis A via a sliding shoe 20. At an in Fig. 1 downward movement the eccentric ring 18, the downward resetting of the piston 10 (suction stroke) by a return spring 22 (coil compression spring), the upper end is supported on a shoulder of the pump cylinder 12 and the lower end is supported on a shoulder of the support body 14, the lower end in turn such shaped with an outer periphery of the shoe 20 cooperates, that the force acting on the support body 14 spring force is transmitted to the shoe 20 and thus via the connection assembly 16 on the pump piston 10 and this leads down.

The connection assembly 16 is constructed comparatively complicated and problematic in terms of the reliability of the connection thus created.

Hereinafter, with reference to Fig. 2 a modification of the conveying unit 1 described above, in which these disadvantages are eliminated and, moreover, the support body has a simpler design. In the following description of this embodiment, the same reference numerals are used for equivalent components, each supplemented by a small letter "a" to distinguish the embodiment. In this case, essentially only the differences from the exemplary embodiment already described are discussed and, moreover, explicit reference is made here to the description of the preceding exemplary embodiment.

Fig. 2 shows a conveyor unit 1a, wherein for the sake of simplicity some components are omitted, which are not essential for the modification.

In the conveying unit 1a can be seen again a pump piston 10a, which is guided for reciprocating movement in the direction of a .Pumpkolbenachse A in a pump cylinder 12a, and a sleeve-shaped support body 14a, which is guided on an outer peripheral surface of the pump cylinder 12a in the direction of the pump piston axis A. ,

In contrast to the known embodiment described above, the pump piston 10a at its in Fig. 2 lower end of an integrally formed with the pump piston 10a, widened pump piston 30a on.

The pump piston foot 30a has a widened first foot section 32a and a second foot section 34a, which adjoins it at the bottom and projects beyond an end of the sleeve-shaped support body 14a.

The driving connection between the pump piston 10a and the support body 14a is realized by a snap ring 36a, which is partially disposed in an outer circumferential groove of the pump piston 30a and partially in an inner circumferential groove of the sleeve-shaped support body 14a.

In the illustrated embodiment, the outer circumferential groove of the pump piston foot 30a is arranged in the region of the first foot portion 32a and adjoins directly to the inner circumferential groove of the substantially hollow cylindrical supporting body 14a.

During operation of the fluid pump, the pump piston foot 30a, which is formed integrally with the pump piston 10a, serves as a tappet, which, for B. in a conventional manner by means of a Exzentertriebs in Direction of the pump piston axis A can be charged to drive the pump piston 10a upwards (pumping stroke). The provision of the pump piston 10a in the suction stroke is again by a return spring 22a, which is supported on the one hand on a shoulder of the pump cylinder 12a and on the other hand on the outer circumference of the second foot portion 34a. During the suction stroke, the restoring force of the spring 22a is thus exerted directly on the pump piston foot 30a and the pump piston 10a connected in one piece therewith.

The actuation force exerted on the pump piston foot 30a by the pump impulse used during the pumping stroke is likewise transmitted directly to the pump piston 10a and to the support body 14a, since the in Fig. 2 lower end of the support body 14a also rests on an upper side of the second foot portion 34a.

With the described construction, a cost-effective to produce and yet reliable conveyor unit 1a is created.

Special features of in Fig. 2 Of course, the design shown can be extensively modified in the context of the invention. As a particularly favorable it has z. However, for example, when a cross-sectional area or diameter of the pump plunger 10a initially gradually increases in a transitional area to the first leg portion 32a, the cross-sectional area or diameter of the first leg portion 32a (apart from the outer circumferential groove) is substantially constant, and the cross-section or the diameter at the transition to the second foot portion 34a increases again abruptly to a footprint for the Return spring 22a and / or provide the support body 14a.

Claims (4)

1. Fluid pump, in particular high-pressure fuel pump for injection systems of internal combustion engines, having at least one pump piston (10a) which is guided in a pump cylinder (12a) so as to perform a reciprocating movement in the direction of a pump piston axis (A), and having a sleeve-shaped support body (14a) which is guided in the direction of the pump piston axis (A) and which is in driving connection with the pump piston (10a), the pump piston (10) having a widened pump piston base (30a) which is formed in one piece with the pump piston, and the driving connection being realized by means of a locking ring (36a) which is arranged partially in an outer circumferential groove of the pump piston base (30a), the pump piston base (30a) having a widened first base section (32a) on which the outer circumferential groove for the locking ring (36a) is arranged, characterized in that the sleeve-shaped support body is guided on an outer circumferential surface of the pump cylinder, the locking ring is arranged partially in an inner circumferential groove of the sleeve-shaped support body (14a), and the pump piston base (30a) also has adjoining it a yet further widened second base section (34a) which projects beyond an end of the sleeve-shaped support body (14a) and on which the end of the sleeve-shaped support body (14a) bears.
2. Fluid pump according to Claim 1, the outer circumferential groove of the pump piston base (30a) and the inner circumferential groove of the sleeve-shaped support body (14a) being substantially directly adjacent to one another.
3. Fluid pump according to one of the preceding claims, comprising a restoring spring (22a) which acts between the pump cylinder (12a) and the pump piston (10a) in the direction of the pump piston axis (A).
4. Fluid pump according to Claim 3, the restoring spring (22a) being supported at one side on a shoulder of the pump cylinder (12a) and at the other side on the second base section (34a).

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