DE102011101239A1 - Hydraulic plunger for balancing valve clearance at inlet and exhaust valves of combustion engine, has low-pressure chamber connected to first oil supply, and high-pressure chamber impinged with hydraulic pressure by second oil supply - Google Patents

Abstract

The plunger (1) has a piston (3) arranged in an axial-movable cylinder (2) that is formed between the piston and a hydraulic high-pressure chamber (4). The piston includes a low-pressure chamber (7) fluidly connected to a first oil supply (13). The low pressure chamber fluidly connects an input oil passage (36) with the high-pressure chamber. The cylinder comprises a second oil supply (34). A high-pressure chamber is impinged with hydraulic pressure by the second oil supply. The input oil passage comprises a throttle (31) between the low-pressure chamber and the high-pressure chamber.

Description

The invention relates to a hydraulic tappet for compensating valve clearance in an internal combustion engine.

Hydraulic tappets are used to compensate for valve clearance on the intake and exhaust valves of an internal combustion engine. They are essentially made up of a cylinder and a piston. As actuating means for opening intake and exhaust valves usually camshafts are used. Valves are usually closed by valve springs and pressed firmly against a valve seat. Hydraulic tappets are arranged in a mechanical acting between the camshaft and the valve so that they are loaded axially when opening the valves. Depending on the active device used, hydraulic tappets may, for example, be arranged directly above a valve or support a finger follower. When a hydraulic tappet is loaded axially, an oil column disposed in a high-pressure chamber transmits the operating force. When the valve play is present, the hydraulic tappet is relieved axially and a spring acting between the cylinder and the piston pushes the piston away from the closed side of the cylinder. In this case, oil flows from a low-pressure chamber into the high-pressure chamber.

Due to an exhaust gas turbocharging, relatively high pressures can occur in an exhaust gas outlet since the exhaust gas is dammed up in front of an inlet of the turbine. The high pressures can occasionally lead to an exhaust valve being opened unintentionally. In this case, the hydraulic tappet is relieved, which can lead to a subsequent flow of oil in the high-pressure chamber (inflating the hydraulic valve). The exhaust valve may then no longer be pushed with sufficient force into its valve seat, so that it can be more easily opened, especially in the next cycle. The flow of oil into the high-pressure chamber of the hydraulic tappet in the event of unintentional opening of the valve can be counteracted by the use of reinforced valve springs. However, this leads to the fact that the camshaft must act against high forces and is correspondingly difficult to turn, which in turn leads to increased friction losses in the internal combustion engine.

It can be regarded as an object underlying the invention to avoid these disadvantages.

The object is solved by the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims, which can be combined with each other in a technologically meaningful way. The description, in particular in conjunction with the drawing, additionally characterizes and specifies the invention.

Accordingly provided is a hydraulic tappet for compensating a valve clearance in an internal combustion engine, the hydraulic tappet having a cylinder and an axially movably disposed in the cylinder piston, wherein in the cylinder between the piston and the cylinder hydraulically effective high-pressure chamber is formed and wherein the piston has a low-pressure space , which is fluidly connected to a first oil supply, and wherein the piston further comprises a low pressure chamber fluidly connected to the high-pressure chamber connecting oil passage, wherein the cylinder further comprises a second oil supply for pressurizing the high-pressure chamber with a hydraulic pressure.

The first oil supply is used to compensate for leakage during operation of the internal combustion engine. Preferably, the first oil supply is always open. The low pressure space of the hydraulic tappet is supplied with oil via the first oil supply during operation with oil to compensate for leakage between the piston and the cylinder. The first oil supply is formed from a first arranged in a cylinder head supply channel and holes in the hydraulic tappet. The same applies to the second oil supply, which supplies the high-pressure chamber with oil. Preferably, the second supply line can be switched off and is only briefly acted upon by a start of the internal combustion engine with pressure to compensate for the valve clearance. When the valves are actuated, a relatively high pressure prevails in the high-pressure chamber, which pressure can exceed the pressure prevailing in the second supply line. This pressure can be hydraulically supported on a check valve, which can be arranged between the low-pressure chamber and the high-pressure chamber. As soon as the pressure subsides, for example during an axial unloading of the hydraulic tappet, oil can flow from the low-pressure space through the check valve into the high-pressure space.

In an advantageous development of the invention, the compensating oil passage between the low-pressure chamber and the high-pressure chamber has a means for limiting a fluid flow. By the means for limiting the fluid flow, the subsequent flowing oil is braked with an axial relief of the hydraulic tappet. In this way, the oil flow is limited and the incorrectly interpreted as a valve clearance axial relief of the hydraulic tappet does not equal to a pumping of the hydraulic tappet. Namely, pumping up the hydraulic tappet could result in the force with which the valve passes through the valve spring in the closed position is held, is reduced due to an increased fluid pressure in the high-pressure chamber and thus the valve can be opened by gas forces unintentionally easier.

In an advantageous embodiment, the means for limiting a fluid flow may be formed by a throttle or a diaphragm. Furthermore, it may be formed by a narrowing cross-section. With a throttle is meant an inserted, for example, screwed or pressed-in element, which opposes the hydraulic flow resistance. A diaphragm may be formed in the material of the piston, for example by a projecting into the compensation channel collar-like projection. By a narrowed cross-section is meant a cross-section of less than 1 mm, in particular less than 0.7 mm. In contrast, in conventional hydraulic tappets, the compensating oil channel is generally dimensioned so that the hydraulic flow can flow as unhindered as possible.

According to an advantageous development of the invention, in the region of the second oil feed, the cylinder has a non-return valve which opens into the high-pressure space in the fluid direction. The check valve allows the inflow of oil in the high-pressure chamber, but locks in the opposite direction.

To accommodate the hydraulic tappet is a cylinder head having a corresponding recess into which a first supply line for supplying the low-pressure chamber and a second supply line for supplying the high-pressure chamber open. The hydraulic tappet can be arranged in the recess. The supply lines are preferably arranged so that provide a fluid-conducting connection to the corresponding oil feeders with inserted hydraulic tappet.

In an alternative embodiment, a check valve is arranged in a leading to the hydraulic tappet second supply line arranged in the cylinder head. The check valve in the second oil supply should be arranged as close as possible to the high-pressure chamber or the receptacle for the hydraulic tappet, so that the hydraulic capacity can be kept low. Check valves exist on the market as screw-in hydraulic elements, so that an upgrade of existing engine designs with hydraulic tappets can be performed in a simple manner according to the nature described here.

According to a particularly preferred embodiment, the second supply line has a device for interrupting the flow of oil, for example a switching valve. The switching valve can be actuated hydraulically or electromechanically and simultaneously shut off a plurality of second oil feeds arranged on a cylinder head. As a result, after a start of the internal combustion engine, the valve clearance can be compensated quickly. After balancing the valve clearance, the oil flow restriction device may interrupt the flow of oil. The hydraulic ram is then supplied only by the first supply line with oil.

There are various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, reference is made to the following explanation of some preferred embodiments with reference to the drawings. In this drawing show:

1 FIG. 2: a schematic representation of a hydraulic tappet with a cylinder and a piston arranged axially movably therein, FIG.

2 a sectional view through an area of a cylinder head of an internal combustion engine, with a valve train formed by a finger follower and a camshaft.

1 schematically shows the structure of a hydraulic tappet 1 with a cylinder 2 and a piston 3 , The cylinder 2 is open on one side and the piston 3 partially protrudes from the cylinder 2 out. In the assembled state, the piston 3 with each actuation of a valve axially against the cylinder 2 pressed. It transmits one in a high pressure room 4 existing oil column the operating force. With an axial relief of the hydraulic tappet 1 pushes one in the high pressure room 4 arranged spring 5 the piston 3 from the cylinder 2 path. It can by a arranged in the piston check valve 5 Oil from a low pressure room 7 in the high pressure room 4 naturally replenished. The check valve 6 is by a ball 8th formed when pressurizing the high-pressure chamber 4 against a valve seat 9 in the ground 10 of the piston 3 is pressed and thus the high-pressure chamber 4 seals. The ball 8th is by a check valve spring 11 always in the valve seat 9 held. The check valve spring 11 however leaves a flow of oil from the low pressure space 7 in the high pressure room 4 to. The check valve spring 11 is through a cup-shaped cage 12 guided and supported.

At about halfway up, the cylinder points 2 a first oil supply 13 on, over which oil from a first supply line (reference numeral 29 , please refer 2 ) through a hole 14 in the cylinder wall 15 in the low pressure room 7 can get. The piston 3 also has a hole for this purpose 16 on, the fluid-conducting in the low-pressure space 7 empties.

Furthermore, the piston 3 a line 17 to supply a head 18 with lubricating oil. The lubricating oil is the same oil as the oil in the low-pressure space 7 or in the high pressure room 4 ,

To ensure that the oil through the first oil supply 13 in the low pressure room 7 can reach, the piston points 2 a circumferential groove 19 on. In the groove 19 can collect oil, which through the holes 16 in the low pressure room 7 can flow.

The hydraulic tappet 1 can in a valve drive 38 a cylinder head 20 be arranged as in 2 shown. The valve drive 38 is essentially a camshaft 21 , one pivotally on the cylinder head 20 arranged drag levers 22 as well as the hydraulic tappet 1 educated. In the in 2 illustrated embodiment presses upon rotation of the camshaft 21 a rotationally fixed to the camshaft 21 arranged cam 23 the rocker arm 22 down and opens such a valve 24 , By in the hydraulic tappet 1 arranged spring 5 becomes any play in the valve drive 38 automatically balanced.

Once a clearance between between the drag lever 22 and the valve 24 or between the hydraulic tappet 1 and the rocker arm 22 is present, pushes the spring 5 the piston 3 to the top and thus compensates for the free space or the game. Between on the cylinder head 20 and an end area 25 of the valve 24 are heels 26 arranged between which a valve spring, not shown, can be arranged, which the valve 24 with decreasing operating force closes again and firmly against a valve seat 35 suppressed.

The valve 24 provides a switchable connection between a combustion chamber 27 and a gas tower, especially an exhaust tract 28 , ready. Particularly in the case of an exhaust gas turbocharging, very high pressures can occasionally arise in the exhaust tract caused by damming of the exhaust gas in front of a turbine inlet, not shown, which causes the valve 24 press down and thus can open. In the valve train 38 then there is game, which by the in a recess 37 arranged hydro tappets 1 can be compensated. Subsequently, the valve spring, not shown, presses the valve 24 Although back up, under certain circumstances, the valve spring pushes the valve 24 but not strong enough in his valve seat 35 if there is too much oil in the high pressure room 4 is located and there is a correspondingly high pressure in it. The pressure in the hydraulic tappet 1 can through a between the piston 3 and the cylinder 2 escape occurring leakage again. In particular, in the case of unintentional opening of the valve 24 The next cycle can be the valve 24 However, if necessary, be opened more easily, which can lead to compression losses. In an advantageous embodiment, in the compensating oil passage 36 (please refer 1 ) means for limiting the volume flow, z. B. a throttle 31 be arranged or only the cross section of the compensating oil passage 36 be kept relatively low. As a result, the volume flow of nachfließendem oil in the high-pressure chamber 4 limited. In this way it can be prevented that the hydraulic tappet 1 in the event of unintentional opening of the valve 24 too quickly "pumped up", the compensation of play by leakage is however guaranteed.

It is proposed in an essential aspect of the invention, in addition to a first supply line 29 , which through the first oil supply 13 the low pressure room 7 (please refer 1 ) supplied with oil, a second supply line 30 provided.

As schematically represented by a corresponding fluidic character, the first supply line 29 constantly in operation via a pump 32 supplied with oil. The pump 32 can be the existing in almost every engine oil pump. As a result, valve clearance during operation can be compensated at any time.

Especially after a state of the engine, the hydraulic tappets relax 1 usually by leakage. This oil flows from the high-pressure chamber 4 and it forms a valve clearance. This game is to compensate for a start of the engine quickly back. This is the second supply line 30 provided, which via a check valve 33 directly into the high pressure room 4 empties. The check valve 33 can be like in 1 also shown on or in the cylinder 2 to be ordered. For this purpose, the cylinder 2 a corresponding second oil supply 34 on, similar to the first described above oil supply 13 can be trained.

The check valve 33 is required to work in the high pressure room 4 supporting high pressures. In order to keep the hydraulic capacity as small as possible and to produce no elasticities in the system, the check valve should 33 as close to the high pressure room 4 or even arranged in it.

Preferably, the second supply line 30 switched off, so that after a start of the engine, the valve clearance quickly compensated and then over the first supply line 29 only leakage is compensated. For this purpose, a switching valve 39 be used. At a start of the engine becomes the second supply line 30 temporarily pressurized with oil, until the attributable to valve clearance, audible "ticking" of the engine has stopped.

Although some possible embodiments of the invention have been disclosed in the foregoing description, it is to be understood that numerous other variants of embodiments exist through the possibility of combining all of the cited and further all of the obvious technical features and embodiments. It is further understood that the embodiments are to be understood as examples only, which in no way limit the scope, applicability and configuration. Rather, the foregoing description would suggest a suitable way for the skilled person to realize at least one exemplary embodiment. It should be understood that in an exemplary embodiment, numerous changes in the function and arrangement of the elements may be made without departing from the scope and equivalents disclosed in the claims.

LIST OF REFERENCE NUMBERS

1

hydraulic tappets

2

cylinder

3

piston

4

High-pressure chamber

5

feather

6

check valve

7

Low-pressure chamber

8th

Bullet

9

valve seat

10

ground

11

Check valve spring

12

Cage

13

first oil supply

14

drilling

15

cylinder wall

16

drilling

17

management

18

head

19

circumferential groove

20

cylinder head

21

camshaft

22

cam follower

23

cam

24

Valve

25

end

26

paragraph

27

combustion chamber

28

exhaust tract

29

first supply line

30

second supply line

31

throttle

32

oil pump

33

check valve

34

second oil supply

35

valve seat

36

Balance oil passage

37

recess

38

valve drive

39

switching valve

Claims (7)

Hydro tappets ( 1 ) for balancing a valve clearance in an internal combustion engine, the hydraulic tappet ( 1 ) comprising a cylinder ( 2 ) and an axially movable in the cylinder ( 2 ) arranged piston ( 3 ), wherein in the cylinder ( 2 ) between the piston ( 3 ) and the cylinder ( 2 ) hydraulically effective high-pressure chamber ( 4 ) and wherein the piston ( 3 ) a low-pressure space ( 7 ), the fluid-conducting with a first oil supply ( 13 ), and wherein the piston ( 3 ) continue the low pressure space ( 7 ) with the high-pressure chamber ( 4 ) fluid-conducting connecting compensation oil channel ( 36 ), wherein the cylinder ( 2 ) further comprises a second oil feed ( 34 ) for impinging the high-pressure space ( 4 ) having a hydraulic pressure. A hydraulic tappet according to claim 1, wherein the compensating oil channel ( 36 ) between the low pressure space ( 7 ) and the high-pressure chamber ( 4 ) a means for limiting a fluid flow ( 31 ) having. A hydraulic tappet according to claim 2, wherein the means for limiting fluid flow through a throttle ( 31 ) or a diaphragm is formed. Hydro tappets ( 1 ) according to claim 1, wherein the cylinder ( 2 ) in the region of the second oil feed ( 34 ) in a fluid direction in the high-pressure chamber ( 4 ) opening check valve ( 33 ) having. Cylinder head ( 20 ), having a recess ( 37 ) for receiving a hydraulic tappet ( 1 ) according to one of the preceding claims, wherein the cylinder head ( 20 ) a first in the recess ( 37 ) supply line ( 29 ) for the supply of the low pressure space ( 7 ) via the first oil feed ( 13 ) and a second in the recess ( 37 ) supply line ( 30 ) for the supply of the high-pressure chamber ( 4 ) via the second oil feed ( 34 ) having. Cylinder head ( 20 ) according to claim 5, wherein the cylinder head ( 20 ) in the second supply line ( 30 ) adjacent to the receptacle a check valve ( 33 ) having. Cylinder head ( 20 ) according to claim 1, wherein the second supply line ( 30 ) means for interrupting the flow of oil ( 39 ) having.

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