DE202012012656U1 - Pump unit with rolling tap - Google Patents

Abstract

Pump unit (1) for transmitting a mechanical actuating force to a hydraulic medium of a hydraulic system, in particular a hydraulic valve train of an internal combustion engine, wherein the pump unit (1) connectable to the hydraulic system housing (5, 15) for receiving a pump piston (7, 12 ) and an actuating head (2) of the pump piston (7, 12) is at least partially formed by a rollable actuating element (9).

Description

The innovation relates to a pump unit for transmitting a mechanical actuating force to a hydraulic medium of a hydraulic system, in particular a hydraulic valve train of an internal combustion engine. Furthermore, the innovation relates to such a hydraulic valve train with a pump unit.

Such a pump unit occurs, for example, in electro-hydraulically controlled valve trains for internal combustion engines. It serves to transmit the mechanical force of a camshaft via an actuating piston, which is referred to below pump piston, to a hydraulic medium of the electro-hydraulic valve train.

The pump units are mounted in a receptacle, which ensures the connection to the hydraulic medium. For this purpose, the housing of the pump unit typically has to be insertable into a receptacle of a valve cover or actuator, which is sometimes also called a "brick". Possible options here consist of a simple pressing or screwing into the receptacle.

The actuating head of the pump unit is actuated by a cam of the camshaft at regular intervals, according to the respective engine cycle. The pump piston is moved in the actuating direction by the cam movement in the piston guide of the housing. The countermovement is usually ensured by a restoring spring element. Known pump units are constructed in several parts and have a concentric with the actuating piston arranged spring, which causes the said provision of the actuating piston.

When using a bucket tappet on the pump unit, it is disadvantageous that the rotational movement of the cam on the running surface of the cup leads to a higher friction.

Another problem is the use of roller tappets, especially since the tread of the cup is also rubbed. In addition, the weight of the roller tappet is so high that the moving masses increase in pumping operation. As a consequence, disadvantageously, a stiffer spring or spring element must be used.

Summary of the innovation

The innovation is based on the object to ensure a low-friction power transmission from a cam on the pump unit, with little space used and a small number of components is implemented to provide a cost-effective pump unit.

This object is achieved in a pump unit of the type mentioned above in that the pump unit has a connectable to the hydraulic system housing for receiving an actuating piston and an actuating head of the actuating piston is at least partially formed by a rollable actuator.

As already indicated at the outset, the hydraulic system may be a valvetrain of an internal combustion engine, but also any other hydraulic system actuated at periodic intervals, which is ideally driven via a shaft with cams. However, an actuation outside the hydraulic system - quasi as wave replacement - can also be linear.

The housing can be screwed or pressed into a receptacle, for example, wherein it is a part of the hydraulic system in the recording. The component may for this purpose have a plurality of lines for the hydraulic medium or be otherwise configured for receiving the hydraulic medium. In particular, the component but also the entire hydraulic system can have multiple receptacles for several pump units and / or other hydraulic units. In particular, the hydraulic system may be a so-called uni-air system, which represents an electrohydraulic valve drive of an internal combustion engine.

The housing of the pump unit is provided for receiving a pump piston. The pumping action is achieved in that the fixed housing of the actuating piston at different stages of the movement occupies different amounts of volume of the housing interior and thus a corresponding volume of the hydraulic medium can be moved. The movement of the pump piston can take place in the direction of actuation or counter to the direction of actuation, which is always a relative movement to the housing.

The mechanical connection of the pump piston to the mechanical actuator is the actuator head. For example, the actuating head may be operatively connected to a cam formed on a camshaft. Since the pump piston and the housing sealingly close to each other, the pump piston or its actuation causes a transfer of the actuating force to the hydraulic medium.

Innovation is now provided that the actuating head of the pump piston at least partially formed by a rollable actuator. Due to the rollability of the actuating element, it is possible to circumvent the problem of sliding friction and instead to support a rolling movement or rotational movement. In this way, the movement of the actuator element is separable in two movements. On the one hand this is the rotational movement of the actuating element and on the other hand, it is the linear actuation of the pump piston in the actuating direction within the receptacle of the housing of the pump unit along.

For example, assuming a classic cam of a camshaft, the adverse effects caused by the rotational motion of the shaft can be compensated. Advantageously, the pump piston is not tilted during its movement in the housing, or its actuator head is not damaged or otherwise affected.

In an advantageous embodiment, the actuating element is a slide-mounted or roller-mounted ring. In a slide bearing the resulting friction is effectively intercepted by means of a plain bearing, so that the wear-prone surfaces of the plain bearing can be designed specifically for this purpose. This is better accomplished, for example, in a radial sliding bearing, as in a flat frictional contact on an actuating head, which is designed for example as a cup.

In a roller bearing ring as an actuator, the friction is further reduced because it comes at any point to a sliding friction, but only a Wälzreibung beats to book, which is extremely low compared to the aforementioned friction. The roller bearing ring may for example be mounted on an axle or a bolt, wherein the axle or the bolt can be held in a fork.

Advantageously, the ring is roller-mounted with respect to a shaft held in a fork. It is advantageous that the fork, the rolling elements, which may for example be cylindrical, can axially hold in their career, so no rolling bearing cage would be required. It is irrelevant whether the axis is rotationally secured in the rolling direction or not. Ideally, the axle is fixed to the fork. The ring includes the rolling elements and also the underlying axis radially, wherein the ring is also axially held by the fork in position.

Advantageously, the fork is in one piece, in particular einmaterialig, formed with the pump piston. Since the actuator is indirectly held by the fork, the fork transmits the actuating force to the actuating piston. For stability reasons, it is therefore advantageous to carry out the fork in one piece with the same. In this way, unwanted breakages are avoided and reduces the number of components. This can be realized particularly easily if fork and actuating piston are formed in one material and have been machined out of the same workpiece.

In an advantageous embodiment, the pump unit has an anti-twist device. The anti-rotation prevents rotation of the pump piston relative to the housing around the piston axis. Since the pump piston is usually formed substantially cylindrical and is guided in a hollow cylindrical guide of the housing, this can also be moved around the piston axis (this coincides with the direction of movement) around relative to the housing. Other geometries usually have disadvantageous properties. In order to prevent now that the fork with respect to the externally actuated element, such as the cam above cam, assumes an incorrect position, the anti-rotation device is used. The purpose of the anti-twist device is to protect the fork from damage by the actuating element, which would inevitably occur if the pump piston could rotate about its axis extending in the direction of actuation. The rollable actuator can now be aligned thanks to the rotation in an optimal, operational angle to the externally actuated element. If, for example, it is an annular actuating element, then it makes sense that the outer circumference of the annular actuating element can roll along the cam. An incorrect orientation of the actuating element would lead to the suppression of the rolling motion and thus at least cause sliding friction again, if not even the actuating element or possibly the fork would be damaged.

Advantageously, the anti-rotation is based on a positive connection. This positive connection should be brought about between the pump piston and the piston guide or the housing. A positive connection can be realized in that a guide groove is formed on the pump piston or on the housing, into which a guide element engages, wherein the guide element and guide groove are displaceable relative to one another. The said shift takes place in the direction of actuation or in the opposite direction (return direction). The length of the guide is at least the maximum operating distance (stroke).

The guide element must be suitable to produce a positive connection in the circumferential direction in the guide groove. For this purpose, the guide element can take various forms, such as z. B. a cone shape or spherical shape. Correspondingly, the cross section of the guide groove would be either triangular or would form a semicircle. Other geometric designs are conceivable.

If a guide groove is formed on the pump piston or on the housing, then the guide element is designed or fixed correspondingly on the housing or pump piston. In other words, the guide groove can be introduced into the housing and the guide element can be firmly attached to the movable pump piston. Conversely, it is possible to form the guide element on the housing and the guide groove on the pump piston. In all cases, it must be taken into account that the housing and the pump piston adjoin one another in such a way that a seal, for example a gap seal, is formed for the hydraulic medium.

Advantageously, the pump piston is biased relative to the housing via a spring element. This spring element ensures that the pump piston is moved back into the starting position after an actuation has been caused by the external element. In this case, the spring element may for example be designed as a spring and disposed within the piston or outside, but always concentric with this, be arranged.

Further advantageous embodiments and preferred developments of the innovation can be found in the description of the figures and / or the dependent claims.

In the following, the innovation will be described and explained in more detail with reference to the exemplary embodiments illustrated in the figures.

Brief description of the figures

Show it:

1 a pump unit in a sectional view with an internal spring element and a roller bearing ring-shaped actuating element,

2 an outside view of the pump unit 1

3 another, external view of the pump unit 1 and

4 a sectional view of a pump unit with anti-rotation and movable guide.

1 shows a sectional view of a pump unit with a housing 5 , which is the piston guide for the pump piston 7 forms and on the outside means are attached, which is an attachment of the housing 5 in a receptacle of the hydraulic system. The recording of the hydraulic system is not shown, but may for example be formed by a so-called actuator having a plurality of hydraulic units and forms a connecting line system in which the hydraulic medium is guided or pressurized.

The pump piston 7 has an actuating head 2 up, out of a fork 20 , a bolt 11 and a ring 9 is formed, the ring 9 on the bolt 11 is stored on roller bearings. The fork 20 is einmaterialig with the pump piston 7 formed, with the fork 20 also the rolling elements 21 that is radial between the bolt 11 and the ring 9 are arranged, with a game holds axially in position. The bolt 11 thus forms an axis 11 which are in openings of the fork 20 is pressed. The actuating head 2 could be installed in the following ways:
First, the rolling elements 21 on the inner circumference of the ring 9 attached and attached there by means of the grease. Subsequently, the ring 9 with the rolling elements 21 arranged in the fork, so that the fork openings with the ring of rolling elements 21 aligned. Subsequently, the bolt 11 pressed in, so the ring 9 opposite this on the rolling elements 21 is stored.

The circlip 13 is in the case 5 stored as a transport lock and prevents loss of the pump piston 7 out of the case 5 out. Alternatively, a captive also by a stop of the ball 3 be realized opposite to the direction of actuation.

The rotation is implemented by a guide element 3 , which is designed as a ball and the pump piston 7 tight. Furthermore, the anti-rotation device has a guide groove 4 on that in the case 4 is introduced at the piston guide. Thus, the guide element moves 3 in the guide groove 4 in the direction of the direction of actuation B and opposite to this depending on the operating state.

The pump function is ensured by the fact that the actuator head 2 by a cam of a camshaft, which is not shown, is actuated and in the housing 5 on the opening 6 is moved, wherein the spring element 8th , which is designed as a spring, is elastically stressed.

Advantageously, the spring element 8th inside the pump piston 7 and inside the case 5 arranged, wherein both components are braced to each other. Thus, there is the spring element 8th in the pressure chamber of the hydraulic medium. The hydraulic medium is through the opening 6 in the case 5 and moved out of this.

It is also important that the guide groove 4 in the direction of movement must be at least as long as the maximum stroke of movement, but not so long that the cylindrical sealing gap between the housing 5 and the pump piston 7 with regard to its sealing effect.

Advantageously, the housing 5 Press-fit by pushing force in the vicinity of the locking ring 13 on the case 5 is transmitted in the direction of actuation, whereby the actuating head 2 does not have to be charged. Alternatively, on the outside of the housing 5 formed an external thread.

2 and 3 show the receiving unit 1 out 1 in uncut views. The reference numerals of 2 and 3 correspond to those of 1 ,

4 shows a further embodiment of a pump unit with an actuating head 2 with rollable actuator 9 , The cutting plane is perpendicular to the axis 11 or to the bolt 11 , indicating the number of rolling elements 10 that the ring 9 on the axis 11 store, is recognizable.

The embodiment corresponds essentially to that of 1 , where the rotation was realized differently:
The ball 14 is on the inside of the case 15 introduced, bringing the ball 14 as a guide element 14 within the guide groove 16 serves. The guide groove 16 has a semi-circular cross section, so the ball 14 in the circumferential direction around the pump piston 7 form a positive connection. The length of the guide groove 16 is greater than the maximum stroke length, but can also be extended if necessary, as long as the sealing properties of the gap seal are not affected.

The advantage of this embodiment over the 1 is that the ball 14 not with the pump piston 12 has to be moved, whereby a smaller mass is movable.

Advantageously, the pump piston is extruded and is provided at the upper end with a fork shape. The roller unit at the upper end forms the actuating head 2 , With regard to the production, the embodiment of the 1 easier to handle than that 4 because the ball seat in the pump piston 7 a lighter introduction of the pump piston 7 with the stuck ball 3 from the outside into the housing 5 supported, especially the leadership 4 without further ado up to the upper end of the housing 5 can reach. Conversely, it is in the embodiment of 4 not possible, the guide groove 16 to extend in this way, because the ball 14 before the introduction of the pump piston 12 anyway within the case 15 must be stored.

In summary, the innovation relates to a pump unit for a hydraulic system, such as a hydraulic valve train of an internal combustion engine. The aim should be to provide a cost-saving pump unit, which has a long service life and at the same time has a low number of components. The service life extension is realized by a friction minimization through the use of a rolling actuator, wherein rollable implies a rotation, which is associated with, for example, a rolling contact of the rotating element. Thus, trained as a role actuator head with non-rotating pump piston ensure that harmful movements of a camshaft or its cam is counteracted by positive locking.

LIST OF REFERENCE NUMBERS

B

operating direction

1

pump unit

2

actuating head

3

Guide element, ball

4

guide

5

casing

6

opening

7

pump pistons

8th

Spring element, spring

9

Actuator, ring

10

rolling elements

11

Axle, bolt

12

pump pistons

13

circlip

14

Guide element, ball

15

casing

16

guide

20

fork

21

rolling elements

Claims (10)

Pump unit ( 1 ) for transmitting a mechanical actuating force to a hydraulic medium of a hydraulic system, in particular a hydraulic valve train of an internal combustion engine, wherein the pump unit ( 1 ) a connectable to the hydraulic system housing ( 5 . 15 ) for receiving a pump piston ( 7 . 12 ) and an actuating head ( 2 ) of the pump piston ( 7 . 12 ) at least partially by a rollable actuator ( 9 ) is formed. Pump unit ( 1 ) according to claim 1, wherein the actuating element ( 9 ) a sliding bearing or roller bearing ring ( 9 ). Pump unit ( 1 ) according to claim 2, wherein the ring ( 9 ) opposite one in a fork ( 20 ) axis ( 11 ) is roller-mounted. Pump unit ( 1 ) according to claim 3, wherein the fork ( 20 ) in one piece, in particular einmaterialig, with the pump piston ( 7 . 12 ) is trained. Pump unit ( 1 ) according to one of the preceding claims, wherein the pump unit ( 1 ) an anti-twist device ( 3 . 4 ; 14 . 16 ) having a rotational movement of the pump piston ( 7 . 12 ) relative to the housing ( 5 . 15 ) is prevented by the actuating direction (B). Pump unit ( 1 ) according to claim 5, wherein the anti-twist device ( 3 . 4 ; 14 . 16 ) based on a form fit. Pump unit ( 1 ) according to claim 6, wherein on the pump piston ( 12 ) or on the housing ( 5 ) a guide groove ( 4 . 16 ) is formed, in which a guide element ( 3 . 14 ), wherein guide element ( 3 . 14 ) and guide groove ( 4 . 16 ) are displaceable relative to each other. Pump unit ( 1 ) according to claim 7, wherein on the pump piston ( 12 ) or on the housing ( 5 ) a guide groove ( 4 . 16 ) is formed and the guide element ( 3 . 14 ) on the housing ( 5 ) or on the pump piston ( 12 ) is formed or fixed. Pump unit ( 1 ) according to one of the preceding claims, wherein the pump piston ( 7 . 12 ) opposite the housing ( 5 . 15 ) via a spring element ( 8th ) is biased. Hydraulic valve drive with a pump unit according to one of claims 1 to 9.

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