EP1022461B1 - High pressure pump - Google Patents

Description

The invention relates to a high-pressure pump, in particular a radial piston pump according to the claim 1.

Radial piston pumps are used to generate high pressures, For example, as a high-pressure fuel pump in common-rail injection systems used. These pumps stand out due to low leakage and high volumetric efficiency from, with the comparatively simple constructive Construction it allows sealing gaps with those for minimization the leakage required to carry out manufacturing tolerances.

DE 195 07 295 A1 discloses a high-pressure pump, in particular a radial piston pump, with at least one driven by a drive shaft pump unit with a Displacer housing 30 in which a piston 2 is guided axially displaceable, with a Sliding 62 abuts an eccentric ring, the one, the piston 2 at least partially encompassing at a distance, guided in the displacer housing 30 and in a Plant position biased support piston 34 is supported. At the However, piston 2 does not attack any return device (holding device), the piston 2 is located rather loosely on the shoe 62. The expressive movement The support piston is hydraulically controlled. In contrast, the subject of the present invention, a holding device 40, via which the extension movement of the Support piston 24 can be transferred to the piston 12.

US A 5,752,430 discloses a high pressure pump, in particular radial piston pump, with at least one driven by a drive shaft 100 pump unit with a Displacer housing 21 in which a piston 14 is guided axially displaceable. The pump unit has a shoe 37 and a support piston 36 which are integral with each other are trained Since it is the slide shoe 37 and the support piston 36 is a component, of course, not the a component (support piston) to be biased against the other component (shoe), as this The subject of the present invention is.

DE 197 27 29 4 A1 shows a high pressure pump, for example, three or five of one Eccentric shaft driven pumping units in a pump housing are included. Each of the pumping units has an in a positive displacement piston guided over a Slide shoe rests on an eccentric ring, which rotates an eccentric of the eccentric shaft is mounted. It lies the shoe on a flattening of the eccentric ring. During rotation of the drive shaft, the eccentric ring shifted with the flattening perpendicular to the piston axis, so that a corresponding relative movement and the associated Friction between the sliding block and the eccentric ring arises. At high speeds, this relative movement and the associated friction between the eccentric ring and shoe for tilting the eccentric ring and thus lead to destruction of the pump. To exclude this, in the prior art, a support piston in the displacer housing stored, which surrounds the piston in the distance and biased by a compression spring against the eccentric ring is, so that a tilting or twisting of the eccentric ring is practically excluded. In this construction is the piston via a retaining washer with the support piston connected so that the piston extract, i. the movement of the piston in the radial direction inward substantially caused by the coupling to the support piston, biased by the compression spring against the eccentric ring becomes.

The problem with this construction is that the above Relative movements also between the eccentric ring and the support piston, so that the investment area subjected to the eccentric a special wear is. This wear can be adjusted by selecting a reduce suitable sliding pairing, especially in applications in the automotive industry reach the achievable Service life of the pump, without any maintenance with a replacement the wearing parts is required, not from.

In contrast, the invention is based on the object to create a high-pressure pump in which the wear is reduced.

This task is accomplished by a high pressure pump with the Characteristics of claim 1 solved.

According to the invention the support piston - not as in State of the art - on the eccentric ring but on the Slider supported, so that there is no significant relative movement transverse to the support piston axis in the contact area of the support piston can come. That is, the supporting force of the Support piston is on the slide shoe on the eccentric ring transferred, with the relative movement between shoe and eccentric ring does not matter, since the shoe in terms his choice of material to an optimal anyway Slipperiness and abrasion resistance is selected. The invention covers exemplary embodiments, in which the Supporting piston directly is supported on the shoe.

It is preferred if the support piston with a driving shoulder is executed, which is to transfer the extension movement on the piston in contact with the holding device can be brought.

This holding device is advantageously as Holding disk designed with a hub-shaped central portion is placed on the piston and the peripheral portion to the piston extract in contact with the support piston can be brought. In this embodiment, the Support piston directly on the shoe on.

The support piston is preferably with a radial shoulder provided, in which the peripheral portion the retaining disk dives, so that this in the piston extraction movement (radially inward) of the support piston is taken.

The shoe is very easy to install, if he means of a locking ring in a frontal Recording of the support piston is fixed. The holding disc is preferably pressed onto the piston.

The contact pressure of the sliding shoe on the eccentric ring can be optimized even at high speeds, by providing breakthroughs in the support piston, can be introduced via the pressure medium in a pressure chamber to also to bias the shoe hydraulically against the eccentric ring.

Other advantageous developments of the invention are the subject of the further subclaims.

Figur 1 eine Rückansicht einer erfindungsgemäßen Radialkolbenpumpe;

Figur 2 einen Schnitt durch die Radialkolbenpumpe aus Figur 1 entlang der Linie A-A und

Figur 3 zwei Ausführungsbeispiele zur Ausgestaltung einer Pumpeinheit der Radialkolbenpumpe aus Figur 2.

In the following, preferred Auführungsbeispiele the invention are explained in more detail with reference to schematic drawings. Show it:

Figure 1 is a rear view of a radial piston pump according to the invention;

Figure 2 shows a section through the radial piston pump of Figure 1 along the line AA and

FIG. 3 two exemplary embodiments for the design of a pump unit of the radial piston pump from FIG. 2.

Figure 1 shows a rear view of a feed pump 1, such as For example, in common rail fuel injection systems is used for internal combustion engines. As a high pressure pump to pressurize the fuel with Pressing up to 2000 bar are usually radial piston pumps used in which several pumping units, for example three pumping units 2a, 2b, 2c in a pump housing 4 are included.

Figure 2 shows a partial view of a section through the radial piston pump according to FIG. 1 along the line A-A. Accordingly, each pump unit 2 has a displacer housing 6 with a cylinder head 8 and in the radial direction extending inwardly, relative to the cylinder head 8 radially recessed cylinder 10, which is in the pump housing 4 dips.

In the displacer 6, a piston 12 is guided, the rests on a cam ring 14 on a cam ring 16. The bearing surface of the eccentric ring 16 is by a Flattening formed in the representation according to Figure 2 extends perpendicular to the plane.

The eccentric ring 16 is on a sliding bush 18 an eccentric 20 of a drive shaft 22 mounted, in turn About slide bearing in the pump housing 4 is performed.

As explained above, it can be particularly at high Speeds for a twisting or tilting of the eccentric ring 16 come. To secure it in the illustrated in Figure 2 Embodiment on the outer circumference of the cylinder 10 a support piston 24 is guided, the one on the cylinder head 8 supported compression spring 26 in the direction of the eccentric ring 16 is biased. For further details the support piston 24 and thus in operative connection Components are related to the following statements referenced with FIG.

In the cylinder head is a suction channel 28 with a suction valve 30 arranged over which the pressure medium (fuel) can be fed. Pressure side is a pressure channel 32 in the cylinder head 8 is provided which leads to a pressure valve 34, in the parting plane between the cylinder head 8 and a Mounting flange of the pump housing 4 is arranged.

The output of the pressure valve 34 is via a pump housing side Pressure channel 36 with a not shown Connected to the manifold of the three pumping units 2a, 2b, 2c promoted pressure medium (fuel) a Consumable, in the present case fed to a common rail is.

The suction connection of the pump is via a pump housing side Suction channel 38 with the input of the suction valve 30th connected. The pressure valve 34 and the suction valve 30 are both as spring-loaded seat valves, in particular as Check valves executed.

The piston 12 is connected via a retaining disk with the support piston 24 connected so that a pull-out movement of the support piston 24 to the axis 42 of the drive shaft 22 toward the introduction a suction stroke is transmitted to the piston 12.

FIG. 3 shows the contact area of the support piston 24 shown on the shoe 14 in an enlarged view, wherein the drawing part shown on the left of the piston axis 44 a first embodiment and the right of the Piston axis 44 shown drawing part another Embodiment show.

The embodiment shown on the left corresponds essentially the construction as shown can be removed according to FIG.

The identical design in both embodiments Cylinder 10 has a cylinder bore 46 in which the Piston 12 is guided. The cylinder bore 46 is in the mouth area radially expanded, so that an annular space 48 is formed is from the piston 12, the shoe 14 and the Support piston 24 is limited.

The retaining washer 40 has a hub-shaped projection 50, with which they on the bottom in Figure 3 end portion of the piston 12 is pressed. To the pressing with to perform the required quality, the should Retaining disc 40 formed of a soft material be. The hub-shaped projection 50 dips into the annulus 48 on. The lower in Figure 3 end face of the retaining disc Aligns approximately with the adjacent end face of the piston 12, so that this and the retaining plate 40 flat on the Sliding shoe.

In the embodiment shown on the left in Figure 3 has guided on the outer circumference of the cylinder 10 Support piston 24 a radially expanded end portion 52, in whose end face a receptacle 54 for the shoe 14th is trained. The axial length of the receptacle 54 is here chosen so that the end face of the shoe 14 over the adjacent end face of the support piston 24 protrudes, so that the latter no contact with the eccentric ring 16 (see Figure 2).

An outer peripheral portion 56 of the retaining washer 40 extends into the receptacle 54, so that the support piston 24 with an annular end face 58 on the retaining disc 40 and this in turn rests on the shoe 14. that is, in the embodiment shown on the left is based the support piston 24 via the drive plate 40 on the Slide shoe 14 off. This is about one in an annular groove the recording 54 recorded circlip 60 in the axial direction secured to a shoulder of the shoe 14 is present. This shoulder is characterized by a demotion of the formed frontal support surface 62 of the shoe 14, so that the bearing surface of the shoe 62 is slightly reduced becomes. However, this is accepted as the Assembly of the shoe 14 by inserting the mounting ring 60 is considerably simplified.

In the annular skirt of the support piston 24 are two axiallybabstandete Breakthroughs 64, 66 formed by the lower Outer peripheral edge 68 of the cylinder 10 in succession on or are zuusteuerbar. The openings 64, 66 open in the region of the spring chamber of the support piston 24, with Pressure medium (for example, fuel) is filled. that is, through the apertures opened over the peripheral edge 68 64 and 66 can enter pressure medium in the annular space 48 and the retaining washer 40 and the shoe 14 in the direction biasing on the eccentric ring 16.

In the position shown, the piston 12 is located at its top dead center, in which the maximum pressurization the pressure medium takes place. According to Figure 3 is then the breakthrough 66 completely closed during the Breakthrough 68 is not fully controlled. In the Movement of the support piston 24 are successively the breakthroughs 64, 66 opened or closed, so that in dependence from the relative arrangement and geometry of the apertures 64, 66 in the annular space 48 a from the stroke of the control piston 24 dependent pressure can generate over which the retaining disc 40 and the shoe 14 in addition to the force of Compression spring 26 is pressed onto the eccentric ring 16. Regarding the exact functioning of this hydraulic Contact pressure of the shoe 14 to the Exenterring 16 is on the DE 197 27 247 mentioned in the introduction to the description A1, whose content in this regard is the content of is to be counted in the present application.

Although the wear of the retaining washer 40 against the described in the aforementioned patent application solution could be significantly reduced, showed test runs, that between the retaining disk whose position is vertical to the axis 44 of the piston 12 and the support piston 24 through the leadership of the piston 12 is determined in the cylinder 10, and the support piston 24 is still a relative movement, which, albeit to a lesser extent, causes wear the retaining disk 40 leads.

FIG. 3 shows an improved right of the central axis 44 Embodiment, which is substantially different from the above Embodiment differs in that the Support piston 24 not on the retaining plate 40 but directly is supported on the shoe 14. This will be included the illustrated embodiment achieved in that the retaining washer 40 not to the peripheral edge of the shoe is guided (as in the left embodiment), but in the distance ends. The support piston 24 has a Radial shoulder 70, the outer periphery of the retaining washer 40th surrounds and rests on the shoe 62. The holding disc 40 associated annular end face 58 is formed, that they with a minimal gap to the retaining disc 40 stands, so that virtually no support force on the retaining disc 40 is introduced into the shoe 14.

The other structure corresponds to that of the above Embodiment, so that for further explanations can be waived.

With the piston extract, i. during the movement of the support piston 24 runs down from its end position shown this in the embodiment shown on the right in Figure 3 with the annular end face 58 on the retaining disk 40th on, so that the piston 12 due to its connection with the retaining plate 40 is moved downward. In the investment area between the retaining washer 40 and the support piston 24th then act only those forces that the piston extract, i.e. for moving the piston 12 downwards in FIG. 3 required are. These forces are much lower as the forces of compression spring 26, the one shown on the left Embodiment on the support piston 24 in the Holding disc 40 and introduced from there into the shoe 14 become. That is, at the right in Figure 3 shown Embodiment, the wear of the retaining washer 58 is minimal, so that they in terms of choice of material to the optimal design of the pressure with the piston 12 adapted can be, because no special requirements to the Wear resistance are provided.

Claims (7)

1. High-pressure pump, in particular a radial piston pump, with at least one pump unit (2) driven by a drive shaft (22), with a piston housing (6) into which is inserted a piston (12) so that it can move axially, said piston having a sliding pad (14) which contacts against an eccentric ring (16), which is supported by a secondary piston (24) which is preloaded into a seated position and which surrounds the piston (12), with a space between them at least in some places, and which is inserted into the piston housing (6), whereby the withdrawal movement of the secondary piston (24) can be transmitted to the piston (12) via a retaining device (40), and whereby the secondary piston (24) is preloaded directly against the sliding pad (14).
2. High-pressure pump in accordance with Claim 1, characterised in that the secondary piston (24) has an engagement shoulder (58) which, for the purpose of transmitting withdrawal movements of the piston, can be brought into contact with the retaining device (40).
3. High-pressure pump in accordance with Claim 1 or 2, characterised in that the retaining device is a retaining disk (40) which is joined to the piston (12) by a hub-shaped section (50), and the peripheral region (56) of which is positioned in contact with the secondary piston (24) for the purpose of withdrawing the piston.
4. High-pressure pump in accordance with Claim 2, characterised in that in the area where it contacts the sliding pad (14), the secondary piston (24) has a radial step, into which a peripheral section (56) of the retaining disk (40) extends.
5. High-pressure pump in accordance with one of the preceding claims, characterised in that the secondary piston (24) has a recess (54) against which the face of the sliding pad (14) bears, whereby a circlip (60) is arranged in an annular groove in the surrounding sidewall of the recess (54) to fix the axial position of the sliding pad (14).
6. High-pressure pump in accordance with one of Claims 3 to 5, characterised in that the retaining disk (40) is pressed onto the piston (12).
7. High-pressure pump in accordance with one of the preceding claims, characterised in that in the sidewall of the secondary piston (24) there is at least one through-hole (64, 66) which can be opened during the axial movement of the secondary piston (24), so that pressure fluid can be introduced into a pressure space (48) adjacent to the sliding pad (14).

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