DE102004023599A1 - Hydraulic play compensation device for engine components e.g. valve timing mechanism, has ventilation path connecting piston guide gap to oil supply chamber in piston - Google Patents

Abstract

A piston (8) displaceable axially in a cylinder (6) has oil inlet (30) on top and outlet (28) at the bottom open to the pressure chamber (12) formed between the piston and the closed base (2) of the cylinder. The outlet (28) is controlled by a non-return valve (26). A ventilation path (36) connecting the oil supply chamber to the guide gap (10) between piston and cylinder is formed downstream of the inlet.

Description

Territory of invention

The The invention relates to a hydraulic lash adjuster, especially for the Use on internal combustion engines, preferably in valve trains or Belt or chain drives, according to the preamble of claim 1.

background the invention

hydraulic Lash adjusters are coupling elements between two machine elements, which change their relative play to each other during operation. To the Compensation of this undesirable Game serve the said hydraulic lash adjusters, the at least two displaceable by hydraulic pressure to each other Consist of components. The mentioned Machine elements can For example, a gas exchange valve and an actuating this Be part of a reciprocating internal combustion engine. Likewise they find Use in the course of a camshaft drive or Nebenag gregattriebes as a tensioner, wherein the two machine elements a stationary base and e.g. a shoe acting on a chain.

Problematic for the Operation of such lash adjusters is air, which in contain the supplied oil is or otherwise penetrates into the device while in their High pressure part passes. This leads to a partial or total loss of the game-compensating Properties, which adverse effects on the machine elements involved may have. This problem can be exacerbated by unfavorable mounting positions, e.g. by a tendency towards horizontal obstruction arrangement.

From the generic US 3,304,925 is a hydraulic lash adjuster in the valve train of an internal combustion engine is known, with an outer, closed on one side with a bottom cylinder part in which an internal piston element is guided longitudinally displaceable leaving a functionally necessary guide gap, and formed between this bottom and the piston element oil pressure chamber and a formed within the piston element oil reservoir. In addition, this clearance compensation device is equipped with an oil supply to the oil reservoir and a controlled by a check valve connecting channel between the oil reservoir and oil pressure chamber. To avoid inadmissibly high hydraulic pressures, this known device in the interface between the cylinder part and the piston element on a pressure-limiting and an oil leak current permitting flattening.

From the US 4,688,525 a hydraulic lash adjuster (HVA) integrated into a bucket tappet of a gas exchange valve train is known. For a venting of the oil, a cup-like venting element is arranged in a comparatively complicated manner between a cup bottom and the HVA. Its bottom is facing the bottom of the cup, while the open side partially surrounds the HVA. As a result, a labyrinth-like oil flow forced, resulting in a prolonged period for degassing. The thereby expelled air bubbles are discharged through several breather holes or ventilation channels in the bottom of the pot and bottom of the cup. The longitudinally displaceable piston element of the HVA is in abutment with the HVA side facing the pot bottom, wherein a plurality of notches are used to the oil from the outside into the HVA and the discharge of air bubbles to the outside.

Out DE 41 03 055 A1 it is known for the removal of air trapped in the high-pressure chamber of an HVA to arrange in the gap remaining between the cylinder part and the piston element over an axially limited length extending longitudinal grooves.

In EP 0 552 369 A1 It is proposed to provide for the removal of air trapped in a blind hole of a cylinder head during assembly of a HVA in this blind hole on the outer periphery of the blind hole facing cylinder part outer surface a helically extending vent groove.

Of the Invention is based on the object, a hydraulic lash adjuster indicate which, in a comparatively simple way, admission of air in the oil pressure room as far as possible or completely avoids.

The solution This object is achieved with the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

Summary the invention

The invention is based on the finding that the harmful for the operation of a hydraulic lash adjuster harmful air inlet into the oil pressure chamber with reduced effort can be avoided or significantly reduced if it succeeds in the oil volume located before entering the oil pressure space under a degassing extensive use of existing paths to realize.

The Asked task is solved by a hydraulic lash adjuster, with an outer one-sided with a bottom sealed cylinder part, in which one inside piston element longitudinally displaceable is performed while leaving a functionally necessary guide gap, with an oil pressure space formed between this bottom and the piston element and an oil reservoir formed within the piston member, with a the oil storage room supplying oil feed and one controlled by a check valve Connecting channel between oil reservoir and oil pressure room, being downstream of the oil inlet and upstream of the communication passage in the piston member, the oil reservoir and the guide gap connecting venting path is trained.

This Construction has the advantage that, taking advantage of the between cylinder part and piston element existing leak oil path through a connection between the oil reservoir and the leak oil path forming guide gap ensures safe air removal is before this air overcomes of the connecting channel in the oil pressure chamber can get.

Prefers is that the piston element is a substantially hollow cylindrical Piston shirt in the area between the oil reservoir and cylinder part and the venting path in this piston skirt is trained. This piston skirt offers itself because of its cylindrical Design for the arrangement of the vent path at.

Of the venting path itself is favored in the form of a venting channel, the again preferably arranged to extend substantially radially is. This allows in the venting path a reduction of the flow resistance such that the air bubbles get into the leakage gap in a comparatively short way.

to Optimization between on the one hand a facilitated air discharge and on the other hand as possible high resistance against leakage oil losses over the venting path It is preferably provided that the at least one venting channel arranged in a labyrinthine manner.

to further optimization with regard to insensitivity to critical ones Installation positions, it may be preferred in the piston skirt provisionally distributed several in the lead gap opens Provide venting channels. Thus, at oblique or lying obstruction always a safe air discharge to the top guaranteed.

Thereby, that the venting path in the flow path between oil feed and connecting channel relatively closer to the oil feed and arranged correspondingly relatively remote from the connection channel is, can be achieved in an advantageous embodiment that the oil pressure loss through the venting path is less than that which is in the guide gap on the oil path between the oil pressure space and junction the ventilation ducts in these guide gap occurs.

In order to is a sucking effect of between oil inlet and mouth of the venting path in the lead gap lying part of the leakage gap on the rest of this part Leak gap distance avoided, which otherwise leads to an increased leakage oil flow the oil pressure room could lead. Therefore is one possible closely adjacent arrangement to the oil inlet prefers.

For another Optimization regarding the pressure and flow conditions It is preferably provided that the guide gap has a width between 0.003 mm and 0.15 mm, preferably between 0.005 mm and 0.1 mm. In a further embodiment, the venting channel has a width and / or Depth between 0.003 mm and 0.3 mm, preferably between 0.005 mm and 0.175 mm. In this case, depending on the diameter of the piston element each an optimal compromise in terms of maximum air removal and minimized oil loss be set.

Of the minimized oil loss advantageously avoids leakage of the lash adjuster while a stoppage phase. Overall, an optimal combination of number of ventilation channels and their Length in Connection with her cross section can be found.

For another Optimization in terms of vent path design can be be preferred that the piston element from a the oil pressure chamber facing piston lower part and a the oil inlet facing piston upper part is formed, and the ventilation path arranged in the parting plane between piston upper part and piston lower part is. This has the advantage that the design of the ventilation channels essential is relieved, since these now facing each other through the two faces are limited.

there It may be provided that one of the two end faces plan is formed while the other contoured, for example in the form of labyrinthine or meandering Grooves, the other part of the ventilation duct provides.

Alternatively, the contoured in the trained end face lying part of the venting channel also be designed as a at least a comparatively high resistance to oil loss bidding, circumferential spiral groove.

in this connection it is preferred that these spiral grooves are between minimally 0.003 mm and a maximum of 0.3 mm deep, preferably between 0.005 mm and 0.175 mm. With optimized design of this spiral groove depth and their cross-sectional area there are greater freedoms in the choice of the width of the guide gap between cylinder part and piston upper part.

Basically, the Labyrinthnuten formed in one of the two facing end surfaces However, combinations are also conceivable. Especially good Results were e.g. with a labyrinth groove width of approx. 0.3 mm and a number of 5 Labyrinthnuten scored, with a smaller Piston element diameter also a good number of 4 labyrinth grooves Results provided.

The Invention is independent of special requirements in a large number of different use cases applicable, for example in valve trains in HVA's, in the course of with pushrods equipped valve drives or in chain or belt tensioners from e.g. Accessory drives.

Short description the drawings

The Invention will be described below with reference to the accompanying drawings an embodiment explained in more detail. In this shows

1 a cross section through a hydraulic lash adjuster,

2 a cross section through an embodiment of a piston upper part according to 1 , and

3 a plan view of the front side of the piston upper part according to 2 ,

detailed Description of the drawings

A hydraulic lash adjuster used in a valve train, not shown, of an internal combustion engine has 1 one with a floor 2 closed cylinder part 4 on. This cylinder part 4 is used with its outer contour in a not shown housing of the internal combustion engine, wherein the bottom 2 is in operative connection with a gas exchange valve. In a hollow cylindrical receptacle 6 is one to the cylinder part 4 inside, longitudinally displaceable piston element 8th leaving a functionally necessary guide gap 10 used, which has a width in the range of 0.005 mm to 0.1 mm.

Between ground 2 and piston element 8th is in an oil pressure room 12 a compression spring 14 employed such that the piston element 8th maximum up to a locking ring effective as a stop 16 strikes, which in a groove 18 of the piston element 8th is used.

Inside the from a piston top 20 and a piston bottom 22 formed piston element 8th is an oil storage room 24 formed, which via one of a check valve 26 dominated connection channel 28 with the oil pressure room 12 can be brought into flow communication.

The piston upper part 20 points as part of an oil intake 30 a feed cone 32 on, with this piston upper part 20 on his from the oil storeroom 24 opposite side acted upon by a push rod, not shown, and supplied with oil.

The two parts of the piston element 8th , the piston top 20 and the piston lower part 22 , abut each other in a parting plane T, which in the region of a hollow cylindrical piston skirt 34 is arranged. Located in this parting plane T is downstream of the oil inlet 30 and upstream to the connection channel 28 a vent path 36 formed, which the oil reservoir 24 with the guide gap 10 combines.

This ventilation path 36 has a plurality of substantially radially extending ventilation channels 38 on which circumferentially distributed in the piston skirt 34 are arranged. In a straight or curved course, the venting channels 38 preferably a width and / or depth in the size of 0.005 mm to 0.3 mm.

Piston top and piston bottom 20 and 22 each border with one of their faces 40 and 42 to the dividing plane T. While the front side 42 of the piston lower part 22 is ground flat in this embodiment, the front side 40 of the piston upper part 20 contoured formed such that the ventilation channels on the one hand by the corresponding planar part, on the other hand by labyrinth-like grooves 38 are trained and limited ( 3 ).

The contoured trained face 40 indicates according to 3 meandering grooves 38 on, between which raised baffles 46 are arranged. The grooves 38 each consist of an oil and gas receiving collection path, an oil passage and a discharge path. In this embodiment, the grooves 38 transverse to the flow direction along the individual sections, a width of about 0.3 mm and a depth of about 0.005 mm to 0.3 mm.

Alternatively, the vent channel 38 the venting path may be formed as a spiral groove-like groove whose depth is in the range of 0.005 mm to 0.3 mm.

2

ground

4

cylinder part

6

admission

8th

piston element

10

guide gap

12

Oil pressure chamber

14

compression spring

16

circlip

18

groove

20

Piston crown

22

Piston part

24

Oil reservoir

26

check valve

28

connecting channel

30

oil supply

32

intake cone

34

skirt

36

venting path

38

groove vent channel

40

front

42

front

46

baffle

T

parting plane

Claims (13)

Hydraulic clearance compensation device, in particular for use on internal combustion engines, preferably in valve drives or belt or chain drives, with an outer, one-sided with a bottom ( 2 ) sealed cylinder part ( 6 ), in which an internal piston element ( 8th ) longitudinally displaceable leaving a functionally necessary guide gap ( 10 ), with one between this floor ( 2 ) and the piston element ( 8th ) formed oil pressure space ( 12 ) as well as within the piston element ( 8th ) formed oil reservoir ( 24 ), and with an oil reservoir ( 24 ) supplying oil ( 30 ) and one of a check valve ( 26 ) dominated connection channel ( 28 ) between oil reservoir ( 24 ) and oil pressure space ( 12 ), characterized in that downstream of the oil feed ( 30 ) and upstream of the connection channel ( 28 ) in the piston element ( 8th ) an oil reservoir ( 24 ) and the guide gap ( 10 ) connecting venting path ( 36 ) is trained. Play compensation device according to claim 1, characterized in that the piston element ( 8th ) a substantially hollow cylindrical piston skirt ( 34 ) in the area between the oil reservoir ( 24 ) and cylinder part ( 4 ) and the venting path ( 36 ) in this piston shirt ( 34 ) is trained. Play compensation device according to claim 2, characterized in that the venting path ( 36 ) at least one venting channel ( 38 ). Play compensation device according to claim 3, characterized in that the venting channel ( 38 ) is arranged substantially radially. Play compensation device according to claim 3 or 4, characterized in that the venting channel ( 38 ) is formed like a labyrinth. Play compensation device according to at least one of claims 3 to 5, characterized in that in the piston skirt ( 34 ) several distributed in the guide gap ( 10 ) venting channels ( 38 ) are arranged. Play compensation device according to one or more of the claims, characterized in that the venting path ( 38 ) in the flow path between oil inlet ( 30 ) and connecting channel ( 28 ) relatively closer to the oil feed ( 30 ) and correspondingly relatively remote to the connection channel ( 28 ) is arranged. Play compensation device according to one or more of the preceding claims, characterized in that the guide gap ( 10 ) has a width between 0.003 mm and 0.15 mm, preferably between 0.005 mm and 0.1 mm. Play compensation device according to one or more of the preceding claims 3 to 8, characterized in that the venting channel ( 38 ) has a width and / or depth between 0.003 mm and 0.3 mm, preferably between 0.005 mm and 0.175 mm. Play compensation device according to one or more of the preceding claims, characterized in that the piston element ( 8th ) from an oil pressure room ( 12 ) facing piston lower part ( 22 ) and an oil feed ( 30 ) facing piston upper part ( 20 ) is formed and the venting path ( 36 ) in the parting plane (T) between piston upper part (T) ( 20 ) and piston lower part ( 22 ) is arranged. Play compensation device according to claim 10, characterized in that the piston upper part ( 20 ) or the piston lower part ( 22 ) each with their Front side ( 40 respectively. 42 ) to the parting plane (T) and the venting path ( 36 ) by a plane-shaped end face ( 40 or 42 ) and a contoured end face ( 42 or 40 ) is limited. Play compensation device according to claim 11, characterized in that the contoured end face ( 42 or 40 ) labyrinth-like venting channels ( 38 ) having. Play compensation device according to claim 11, characterized in that the contoured end face ( 42 or 40 ) at least one spiraling venting path ( 36 ) or venting channel ( 38 ) having.