DE10237104A1 - Valve drive for a piston combustion engine has a variable lift control with transmission and actuator elements fixed together - Google Patents

Abstract

A valve drive for a piston combustion engine comprises a drive shaft (2), cam (3), a second shaft (4), a transmission element (5) and actuators (6,6') which are fixed together and connected to a gas exchange valve (9,9') through a control rail (7,7') and an intermediate element (8,8'). The second shaft turns about a first axis (10).

Description

The invention relates to a valve train for one Reciprocating internal combustion engine according to the features in the preamble of claim 1.

It starts from the European patent application EP 1 143 119 A2 from, in which a valve train for a reciprocating piston internal combustion engine with a variable stroke valve control is described. In the variable stroke valve control, a cam of a camshaft actuates a transmission lever at one end, while it is arranged at its other end via a helical toothing on an output shaft. A cam is also arranged on both sides of the transmission lever via helical teeth on the output shaft. The helical teeth of the output cam and transmission lever are opposed to each other. When the internal combustion engine is operating, the camshaft rotates and the cam actuates the transmission lever, which transmits the resulting swiveling movement to the output shaft due to the helical teeth. The control cams of the cams, which are also connected to the output shaft via helical gearing, act on the role of a roller finger follower, which is supported on the one hand in a stationary manner in the cylinder head on a hydraulic valve lash adjuster and, on the other hand, presses on a gas exchange valve to open it. The control curve has a zero stroke curve and a stroke curve. If the output shaft is moved in the axial direction, the transmission lever and the cams are secured in position, the relative position angle changes from the cam to the transmission element due to the opposing helical toothing, whereby the proportion of zero stroke curve and stroke curve that acts on the gas exchange valve via the rocker arm is shifted , Depending on the axial position of the output shaft, a stroke adjustment or stroke adjustment of the gas exchange valve is thus possible.

A disadvantage of the design of the Stroke variable valve train are those in the stroke adjustment and in Operation occurring high friction forces in the helical gear Act. Further must the cams and the transmission lever across from the position of the strong, axial displacement forces.

Object of the present invention is for a generic stroke variable Valve train a lower friction Provide adjustment device.

This task is based on the characteristics solved in the characterizing part of claim 1.

Step through the configuration according to the invention no axial forces, as well as significantly lower friction losses. As a result, the use of energy Stroke adjustment of the gas exchange valves much less than that cited prior art.

In a configuration according to claim 2 align the first axis of rotation and the second axis of rotation as long as the rolling element with the zero stroke curve of the control path is connected. The zero stroke curve is the part of the control path that is designed as a radius and where no hub for the gas exchange valves are generated, d. H. the gas exchange valves are closed. When the stroke of the Gas exchange valves changed the roller advantageously only its position on the zero stroke curve, which ensures that the role of the roller rocker arm with the control track and the transmission element always in contact with the cam remain and prevent individual components from being separated from one another is. Premature wear will thus avoided.

The transmission element and that Can control according to claim 3 positive and / or material be connected to one another or manufactured in one piece from the same material become. Depending on the manufacturing process, whether cutting or non-cutting Manufacturing, such as B. sintering or casting, can be the optimal and most economical design selected become.

The design according to the claims 4 to 7 on the one hand, enables the optimal mechanical mounting of the variable-stroke valve train in the cylinder head, as well as an integrated, inexpensive and easy-to-manufacture adjustment option. The bearing elements can either be bolts or stub shafts which engage in bores in the holding elements or bores in which corresponding bolts or stub shafts arranged fixed to the cylinder head engage.

According to the claims 8th and 9 at least one actuator is operatively connected to at least one holding element. This can act mechanically and / or electrically and / or hydraulically. Depending on the required adjustment speed or existing operating media or available installation space, the most suitable actuator can advantageously be selected and used.

The proposed according to claim 10 Actuator as an eccentric is a simple, robust way a maintenance-free and inexpensive Realize actuator.

To minimize friction in the variable stroke valve train is according to claim 11 a roller element, which can be supported by a needle, is proposed, which rolls on the cam.

An embodiment according to the claims 12 to 14 also serves to minimize friction in the variable-stroke valve train and to ensure that there is no play between the individual input and output elements. These measures will go beyond that minimizes wear and maximizes service life.

A control track according to claim 15 largely corresponds to a conventional cam design for camshafts of internal combustion engines. While the zero stroke curve for ensures a closed position of the gas exchange valve, opens the Stroke curve of the gas exchange valve. So that the acceleration from the Zero stroke curve to the stroke curve not due to the inertia forces for the gas exchange valve growing up a ramp is arranged between the zero stroke curve and the stroke curve, which has a flat gradient of gradient by which during acceleration forces occurring to reduce.

According to claim 18 is a stroke variable valve control for At least one combustion chamber is provided, for package or cost reasons however also possible a stroke-variable valve control for the whole Intake side or exhaust side of the cylinder head of an internal combustion engine provided.

An embodiment according to the claims 19 allows the gas exchange valves of a combustion chamber to act and be opened at different times. This makes so-called "valve stroke phasing" possible, with which a tumble or swirl flow in the combustion chamber can be advantageously set to optimize charge movement and combustion.

The invention is described below of two preferred embodiments closer in three figures explained.

1 shows a stroke-variable valve train according to the invention, in which a transmission element is provided for two gas exchange valves,

2 shows a stroke variable valve train according to the invention, in which a transmission element is provided for each gas exchange valve,

3 shows an example of six gas exchange valve lift curves.

The reference numerals from 1 apply to the same components in 2 ,

1 shows a stroke variable valve train according to the invention 1 in a first embodiment, in which for two gas exchange valves 9 . 9 ' a single transmission element 5 is provided. The variable stroke valve train 1 consists essentially of a drive shaft 2 , with at least one cam 3 as well as one to the drive shaft 2 second shaft arranged in parallel 4 , The second wave 4 is both ends in a holding element 14 . 14 ' rotatably mounted. Between the support elements 14 . 14 ' is on the outer circumference of the second shaft 4 the transmission element 5 stored, which is in one piece and uniform with two materials on both sides of the transmission element 5 also around the outer circumference of the second shaft 4 stored control elements 6 . 6 ' is. The transmission element 5 forms in connection with the control elements 6 . 6 ' together a single actuator 23 , Every actuator 6 . 6 ' has a radial control path consisting of a zero stroke curve 11 , a ramp 11a . 11a 'as well as a stroke curve 11b . 11b ', on. The control lanes 7 . 7 ' are each in the form of a contact line on a rolling element 12 . 12 ' an intermediate element 8th . 8th' on. The intermediate elements 8th . 8th' are roller finger followers and are on the one hand each on a play compensation element 19 . 19 ' , a hydraulic valve lash adjuster, and on the other hand on each valve stem of the gas exchange valves 9 . 9 ' , Radially around each gas exchange valve 9 . 9 ' is a valve spring in the direction of the valve stem 20 . 20 ' arranged. These are against an upper spring plate 21 . 21 ' as well as a lower spring plate 21 . 21 ' biased. The valve springs 20 . 20 ' are supported by the lower spring plates 21 . 21 ' on a cylinder head, not shown. A spring force of the springs 20 . 20 ' presses the gas exchange valves 9 . 9 ' in a closed position and at the same time clamps the valve train components of the variable stroke valve control 1 in front. Every holding element 14 . 14 ' has a storage element 15 . 15 ' on. In the present case, this is a stub shaft, alternatively a bore could be provided for the bearing. In addition, each holding element 14 . 14 ' a tour 17 . 17 ' on, in the present case an elongated hole, other design variants are also possible here. In every slot 17 . 17 ' grips an eccentric 16 . 16 ' on. The eccentric 16 . 16 ' are about a wave 24 fixedly connected to each other. The eccentric 16 . 16 ' in connection with the shaft 24 and the oblong holes 17 . 17 ' together form an actuator 13 , Become the eccentric 16 . 16 ' with the wave 24 twisted, so the holding elements 14 . 14 ' together with the second wave stored in it 4 around the first axis of rotation 10 pivoted. This changes the contact lines between the rolling elements 12 . 12 ' and the control lanes 7 . 7 ' , According to a position of the actuator 13 become the zero stroke curves 11 . 11 ' that on the rolling elements 12 . 12 ' act, shifted and thus the effective part of the zero stroke curve 11 . 11 ' enlarged or reduced at the valve adjustment. In the position shown, the gas exchange valves have 9 . 9 ' the maximum valve lift. When turning the actuator 13 , as in 1 shown, the valve lift height of the gas exchange valves 9 . 9 ' reduced until only the zero stroke is set after a 180 ° rotation of the actuator. By changing the position of wave 24 and the first axis of rotation 10 and the second wave 4 to each other, other adjustment angles are also possible. In the case of the zero stroke, the gas exchange valve remains closed, for example to implement a valve shutdown or a cylinder shutdown for the internal combustion engine. Are the rolling elements 12 . 12 ' of the intermediate elements 8th . 8th' on the zero stroke curves 11 . 11 ' on, so are the first axis of rotation 10 and the second axis of rotation 12a the rolling element 12 . 12 ' in flight. This arrangement has the advantage that there is a stroke adjustment when the rolling elements 12 . 12 ' on the zero stroke curves 11 . 11 ' rest, there is no detachment of the individual valve train components. Absolute freedom from play is thus guaranteed with minimal adjustment forces.

For 2 , in which a second exemplary embodiment is shown, the description of 1 , The difference between the two embodiments is that in 2 each gas exchange valve has its own actuator 23 . 23 ' , each consisting of a transmission element 5 . 5 ' and an actuator 6 . 6 ' assigned. Furthermore, each actuator 23 . 23 ' its own cam 3 . 3 ' assigned. A holding element lying on top in the viewing direction of the viewer 14 . 14 ' is not shown to maintain clarity. This embodiment has the great advantage that each gas exchange valve 9 . 9 ' can be controlled separately, that is to say with a different cam contour and / or eccentric contour, which also means valve stroke phasing, which means different stroke control for the gas exchange valves 9 . 9 ' , or individual valve shutdown or, as in the first embodiment, a cylinder shutdown is possible. Valve stroke phasing can have a favorable influence on the charge movement of the combustion air into the combustion chamber, thus optimizing mixture formation and combustion. In addition, the moving masses are in the variable stroke valve control 1 in 2 smaller than in 1 , which is why this second embodiment is particularly suitable for high-speed internal combustion engines. As already in 1 are explained, the drive shaft 2 , the game balancing elements 19 . 19 ' the valve stem guides 22 . 22 ' stationary in the cylinder head, not shown, while the holding elements 14 . 14 ' are rotatably mounted in the cylinder head.

In further exemplary embodiments, not shown, the actuator can 13 Instead of a mechanical eccentric control, there can also be a hydraulic actuator or electric actuator with a worm and a gear. Stepper motors can also be used. In principle, any combination of mechanical and / or electrical and / or hydraulic actuators is possible. It is also possible to have a separate actuator for each cylinder 13 provide or a common actuator for all cylinders on the intake side or exhaust side of the internal combustion engine 13 provided. Through different elevation curves of the control tracks 7 . 7 ' , or the cam contours of the cams 3 . 3 ' or the eccentric contours can be used for the equivalent gas exchange valves 9 . 9 ' different valve lift curves of a cylinder can be achieved. This measure enables the charge movement in the combustion chamber, a swirl or tumble movement, to be influenced in a targeted manner. Swirl movement is an air vortex around the cylinder axis, tumble movement is an air vortex perpendicular to the cylinder axis.

3 shows an example of six gas exchange valve elevation curves 25 for six different actuator settings 13 , The valve stroke is shown in [mm] on the Y axis, while an angle of rotation of the drive shaft is shown on the X axis 2 is recorded. The angle of rotation of the drive shaft is clearly recognizable 2 related rigid position of the maximum valve lifting point. A change in the lifting height therefore does not lead to a change in the position of the maximum gas exchange valve opening.

1

Hubvariable valve control

2

drive shaft

3, 3 '

cam

4

Second wave

5, 5 '

transmission element

6 6 '

steep element

7, 7 '

control track

8th, 8th'

intermediate element

9 9 '

Gas exchange valve

10

First axis of rotation

11 11 '

zero stroke

11a, 11a '

ramp

11b, 11b '

stroke curve

12 12 '

rolling elements

12a

Second axis of rotation

13

actuator

14 14 '

retaining element

15 15 '

storage element

16 16 '

eccentric

17 17 '

guide

18 18 '

role

19 19 '

Lash adjuster

20 20 '

valve spring

21 21 '

spring plate

22 22 '

Valve stem guide

23 23 '

actuator

24

wave

25

Gas exchange valve lift curve

Claims (20)

Valve train for a reciprocating piston internal combustion engine with a variable stroke valve control ( 1 ) with a drive shaft ( 2 ) with at least one cam ( 3 ) and one, to the drive shaft ( 2 ) parallel second shaft ( 4 ) and a transmission element ( 5 ), on the one hand on the outer circumference of the second shaft ( 4 ) is mounted and on the other hand with the cam ( 3 ) is in operative connection and at least one radially on the outer circumference of the second shaft ( 4 ) arranged actuator ( 6 . 6 ' ) with a control track ( 7 . 7 ' ) that have an intermediate element ( 8th . 8th' ) with a gas shuttle valve ( 9 . 9 ' ) is in operative connection, characterized in that the transmission element ( 5 ) and the control element ( 6 . 6 ' ) are fixed to each other and the second shaft ( 4 ) around a first axis of rotation ( 10 ) is pivotable. Valve train according to claim 1, wherein the control path ( 7 . 7 ' ) at least one zero stroke curve ( 11 . 11 ' ) and the intermediate element ( 8th . 8th' ) via a rolling element ( 12 . 12 ' ) with a second axis of rotation ( 12a . 12a ' ) with the control track ( 7 . 7 ' ) is in operative connection, characterized in that in the case of an existing operative connection between rolling elements ( 12 . 12 ' ) and zero stroke curve ( 11 . 11 ' ) the first axis of rotation ( 10 ) with the second axis of rotation ( 12a ) is in flight. Valve train according to claim 1 or 2, characterized in that the transmission element ( 5 ) and the steep element ( 6 . 6 ' ) are positively and / or cohesively connected to one another or are in one piece and uniform in material. Valve train according to one of the claims 1 to 3 , characterized in that the second wave ( 4 ) of at least one holding element ( 14 . 14 ' ) is held. Valve train according to one of the claims 1 to 4 , characterized in that the holding element ( 14 . 14 ' ) a lever arm for the second shaft ( 4 ) to the axis of rotation ( 10 ) is. Valve train according to claim 4 or 5, characterized in that the holding element ( 14 . 14 ' ) at least one coaxial to the first axis of rotation ( 10 ) aligned bearing element ( 15 . 15 ' ) having. Valve train according to claim 6, characterized in that the bearing element ( 15 . 15 ' ) is a bore or a stub shaft. Valve train according to one of the aforementioned claims, characterized in that at least one holding element ( 14 . 14 ' ) with an actuator ( 13 ) is in operative connection. Valve train according to claim 8, characterized in that the actuator ( 13 ) acts mechanically and / or electrically and / or hydraulically. Valve train according to claim 8 or 9, characterized in that the actuator ( 13 ) is an eccentric with a guide ( 17 . 17 ' ) in the holding element ( 14 . 14 ' ) is in operative connection. Valve train according to one of the aforementioned claims, characterized in that the transmission element ( 5 ) a role on the drive shaft side ( 18 . 18 ' ) with the cam ( 3 ) is in operative connection. Valve train according to one of the aforementioned claims, characterized in that the intermediate element ( 8th . 8th' ) is a roller rocker arm or a roller tappet or a rocker arm. Valve train according to one of the aforementioned claims, characterized in that the intermediate element ( 8th . 8th' ) on the gas exchange valve ( 9 . 9 ' ) opposite side on a game compensation element ( 19 . 19 ' ) rests. Valve train according to claim 13, characterized in that the play compensation element ( 19 . 19 ' ) is a hydraulic valve lash adjuster. Valve train according to one of the aforementioned claims, characterized in that the control track ( 7 . 7 ' ) from the zero stroke curve ( 11 . 11 ' ) and an adjoining ramp ( 11a . 11a ') and a subsequent stroke curve ( 11b . 11b ') is composed. Valve train according to one of the aforementioned claims, characterized in that a transmission element ( 5 ) for at least one gas exchange valve ( 9 . 9 ' ) is provided. Valve train according to one of the aforementioned claims, characterized in that a cam ( 3 ) for at least one transmission element ( 5 ) is provided. Valve train according to one of the aforementioned claims, wherein the internal combustion engine has at least one combustion chamber, characterized in that a stroke-variable valve control ( 1 ) is provided for at least one combustion chamber. Valve train according to one of the aforementioned patent claims, wherein at least two inlet gas exchange valves are provided for each combustion chamber and a separate cam is provided for each inlet gas exchange valve, characterized in that at least two cams ( 3 ) for the inlet gas exchange valves ( 9 . 9 ' ) of a combustion chamber are provided, have different elevation curves. Valve train according to one of the aforementioned claims, wherein at least two inlet gas exchange valves and a separate eccentric is provided for each combustion chamber, characterized in that at least two eccentrics for the inlet gas exchange valves ( 9 . 9 ' ) of a combustion chamber are provided, have different elevation curves.