DE10239748A1 - Intake device for flow medium-actuated variable valve drive of IC engine has piston projection with slot having drilled wider part in its base to prevent pressure peaks - Google Patents

Abstract

The device has a housing with intake piston having a projection (13) on one end face. A slot (14) in a projection end face (15) has a drilled wider part (19) in its base (18) away from the end face. The slot extends through the outer jacket (16) of the projection. The wider part consists of two bores, located above each other, with the uppermost bore being the smaller one. The projection is formed integrally with the piston.

Description

Field of the Invention

The invention relates to a slave unit of a fluid operated variable Valve train of an internal combustion engine, with one in one receptacle a cylinder head built-in housing, in its bore axially movable slave piston runs, one end face a pressure room for Hydraulic fluid limited and the other end face at least acts indirectly on at least one gas exchange valve, whereby the pressure chamber axially from one end face towards the one Gas exchange valve extends far bottom of the housing, which floor one the pressure room with an overlying one Opening connecting pressure chamber has, with a reduced diameter from one end face Approach that starts before an end of a closing movement of the slave piston into the opening moves and wherein at least one slot in an end face of the Approach as at least a part of leakage gap means for braking the valve placement speed is applied, which slot an outer jacket of the approach cuts and has parallel walls.

Such a slave unit with slotted attachment on the slave piston in a hydraulic valve train for throttle-free load control is the state of the art Technology known. When the slave piston closes, it moves Approach into the opening of the housing. The deeper the approach goes, the smaller the released discharge area for the hydraulic medium, the The cross section of the slot is reduced. In the now remaining annular Pressure chamber thus increases the pressure and the slave piston becomes Always stronger braked. The hydraulic fluid is compressed further and further thus stiffens. In the worst case Case can be in the closing phase the slave piston does not have enough hydraulic fluid drain through the remaining slot cross section and the hydraulic fluid is compressed so much that the slave piston again in the opening direction rebounds. It can become undesirable delay of closing of the corresponding gas exchange valve.

The object of the invention is therefore to create a slave unit of the aforementioned type, in which the dangerous Pressure peaks are reduced, resulting in a more even braking of the Slave piston is achieved.

Summary the invention

According to the invention, this object solved, that the Slot in the section of its base distant from the end face into a bored extension passes over.

As a result, there is a slave unit before, the slave piston now goes into its seat virtually "bumpless". rebounds are excluded. It is now at the immediate end of the deceleration phase Slave piston, especially important at very high speeds from this, still a sufficiently large cross-sectional area for Deriving the fluid from the rest of the pressure chamber in a ring around the retracted attachment to disposal. This should according to the invention Extension be made as a hole. This makes it particularly easy to use and inexpensive produce.

Of course, several can be distributed over the circumference Slits can be applied with one or more holes, where the slots do not necessarily cut completely radially through the shoulder have to.

The slot itself preferably runs in the direction of the axial line of the slave unit and is, for example using a suitable saw or milling tool manufactured.

Obtain further subclaims appropriate functional configurations the expansion. This can consist of two or more, for example axially one above the other lying holes exist, the top hole then advantageously has the smallest diameter. It is conceivable and envisaged but also to make the top hole with the largest diameter. Likewise it is provided that two or more are seen in the circumferential direction to apply adjacent holes or a combination from side by side and on top of each other horizontal holes may be useful, the diameter of which is not the same have to be.

Finally, it is suggested to produce the approach and the slave piston in one piece. This lowers the manufacturing effort. If necessary, is also a multi-part Training possible.

The slave piston with attachment does not have to necessarily in a separate housing run. It is also a direct installation in the cylinder head or similar to one suitable component possible.

The invention is useful based on the drawing explained. Show it:

1 a slave unit in the installed state and the

2 to 4 in schematic representations, the approach of the slave piston with a slot designed according to the invention.

Full Description of the drawing

1 discloses a slave unit according to the invention 1 of a fluid-operated (engine oil) variable valve train of an internal combustion engine. This consists of a housing 4 that here in a cylinder head 3 an internal combustion engine is screwed. In a hole 5 of the housing 4 a slave piston moves axially 6 , This acts in the area of its other face 9 at least indirectly to a gas exchange valve, not shown in the drawing.

In the area of its one end 7 limits the slave piston 6 a pressure chamber in an axial direction 8th for hydraulic fluid. This pressure room 8th is in the other axial direction from a floor 10 of the housing 4 limited. The floor has 10 an opening 12 to accommodate a cylindrical approach 13 of the slave piston 6 , The slave piston 6 starts to approach immediately before the end of its closing movement 13 into the opening 12 for the purpose of braking the valve touchdown speed.

Starting from an end face 15 of the cylindrical approach 13 runs a channel 20 , This is on its inner edge 21 from a spring-loaded check valve 22 towards the pressure room 8th locked.

Furthermore, the expert can 1 remove that from the ring-shaped here one end face 7 two diametrically opposite paths 23 to one below the check valve 22 lying room 24 to lead. These latter means serve to accelerate the opening movement of the slave piston 6 through the early formation of sufficiently large hydraulic surfaces (front surface 15 , annular face 7 ).

The one out 1 Slightly emerging slot 14 is from the 2 to 4 in its configuration according to the invention can be seen in more detail. It is radially continuous here and extends from the end face 15 with his reason 18 seen in the height direction only up to just before one end 7 , The slot 14 is through two parallel walls 17 limited that on the side of the bottom 18 into a drilled extension 19 pass.

According to 2 is this extension 19 formed from two bores one above the other, with the upper one having the smaller radius.

To 3 there is expansion 19 from several holes lying next to each other in the circumferential direction. The hole shown in dashed lines indicates that a combination of the measures according to 2 and 3 is conceivable.

4 What represents the cheapest variant in terms of production technology only reveals a through hole as an extension 19 ,

The slave piston now moves 6 when the fluid is shut off, for example for the purpose of cutting off the valve stroke at a very high speed, via its approach 13 into the opening 12 a, the free height of the slot decreases with increasing entry depth 17 with extension 19 , Through the drilled extension 19 is now just before the slave piston closes 6 a sufficiently large cross-sectional area is available for draining the fluid. Pressure peaks at the end of the braking phase and rebound, if any, no longer occur.

1

receiver unit

2

admission

3

cylinder head

4

casing

5

drilling

6

slave piston

7

front

8th

pressure chamber

9

front

10

ground

11

pressure chamber

12

opening

13

approach

14

slot

15

face

16

outer sheath

17

wall

18

reason

19

extension

20

channel

21

edge

22

check valve

23

path

24

room

Claims (6)

Slave unit ( 1 ) a fluid-operated variable valve train of an internal combustion engine, with one in a receptacle ( 2 ) of a cylinder head ( 3 ) built-in housing ( 4 ), in its bore ( 5 ) an axially movable slave piston ( 6 ) runs, one end face ( 7 ) a pressure room ( 8th ) for hydraulic fluid and the other end face ( 9 ) acts at least indirectly on at least one gas exchange valve, the pressure chamber ( 8th ) axially from one end face ( 7 ) towards a floor far from the gas exchange valve ( 10 ) of the housing ( 4 ) which floor ( 10 ) the pressure room ( 8th ) with an overlying pressure chamber ( 11 ) connecting opening ( 12 ), with one end face ( 7 ) a reduced diameter approach ( 13 ) which comes before an end of a closing movement of the slave piston ( 6 ) in the opening ( 12 ) and at least one slot ( 14 ) in one end face ( 15 ) of the approach ( 13 ) is applied as at least part of leakage gap means for braking the valve attachment speed, which slot ( 14 ) an outer jacket ( 16 ) of the approach ( 13 ) cuts as well as parallel walls ( 17 ), characterized in that the slot ( 14 ) in the section of its from the face ( 15 ) distant reason ( 18 ) in a drilled extension ( 19 ) transforms ( 2 - 4 ). Slave unit according to claim 1, characterized in that the slot ( 14 ) with the extension ( 19 ) the outer jacket on both of its outer sides ( 16 ) of the approach ( 13 ) cuts, radial or arches like through the attachment ( 13 ) is performed. Slave unit according to claim 1 or 2, characterized in that the extension ( 19 ) consists of at least two bores lying axially one above the other, which merge into one another, the end face ( 15 ) closer hole with smaller radius compared to the distant one ( 2 ). Slave unit according to claim 1 or 2, characterized in that the extension ( 19 ) consists of at least two bores lying next to one another in the circumferential direction at a height, which merge into one another and in the region of their common center from the slot ( 14 ) are cut ( 3 ). Slave unit according to claim 1 or 2, characterized in that the extension ( 19 ) consists of at least two bores lying next to one another in the circumferential direction at a height, which merge into one another and in the region of their common center from the slot ( 14 ) are cut, these bores of at least one further bore lying axially above this through the slot as part of the extension ( 14 ) are cut ( 3 ). Slave unit according to claim 1, characterized in that the attachment ( 13 ) in one piece with the slave piston ( 6 ) is trained.