DE102010055056A1 - Valve-train for use in gas shuttle valve to improve thermodynamic properties of e.g. 6-cylinder V-engine, has camshaft rotatable around rotational axis, where two portions of gearings are arranged between another two sets of portions - Google Patents

Abstract

The valve-train (1) has a base camshaft (3) rotatable around a rotational axis, and cam carriers (4) axially displaceable in relation to the camshaft. A clearance between an internal gearing of the carriers and an external gearing of the camshaft in first and second circumferential portions of the gearings is smaller than that in third and fourth circumferential portions of the gearings. The third and fourth portions are respectively arranged between the first and second portions, where each portion extends over a circumferential angle in a range between 60 and 90 degrees.

Description

The invention relates to a valve train for gas exchange valves of an internal combustion engine according to the preamble of claim 1.

To improve the thermodynamic properties of internal combustion engines valve trains are known in which the working cycle can be influenced, for example, to allow a speed-dependent change in the opening times and / or the stroke of the gas exchange valves.

From the EP 1 608 849 B1 a valve train of the type mentioned for a four-cylinder in-line engine is already known, in which the intake valves and the exhaust valves of the four cylinders are controlled by means of an inlet base camshaft and a Auslassgrundnockenwelle. In each case on the intake base camshaft and on the Auslaßgrundnockenwelle four cam carrier rotatably and axially displaceably arranged, each of which controls the inlet and exhaust valves of a cylinder. Each cam carrier has on its inner circumference a meshing with an outer toothing of the base camshaft, ie in meshing with the external toothing internal teeth and on its outer periphery two axially offset pairs of cams, each of which comprises two cams with different cam profiles. By axial displacement of the cam carrier on the base camshaft along the teeth between two displacement or end positions, one of the two cams of each pair of cams can be brought into abutting contact with one roller of a roller cam follower by one of the valves, thereby increasing the stroke and / or opening times of the valve to adjust to different operating conditions can be adjusted. The axial displacement of each cam carrier on the camshaft in opposite directions takes place with the aid of two worm drives at the front ends of the cam carrier. In order to provide a low-friction axial displacement, engage the outer teeth of the base camshaft and the inner toothing of the cam carrier with play into each other. This clearance usually involves a backlash between opposing tooth flanks of the internal gear and the external gear and a head clearance between the gear teeth of the internal and external teeth and opposite areas at the bottom of the tooth gaps. As a result of the contact pressure of the role of Rollenschlepphebels against the cam carrier, a torque is exerted on the cam carrier during operation of the internal combustion engine, which is opposite to a large part of the rotation of the basic camshaft to the drive torque. This has the consequence that normally in the direction of rotation of the base camshaft front tooth flanks of the outer teeth of the base camshaft are pressed against the opposite tooth flanks of the inner teeth of the cam carrier play, while the backlash between the rear in the direction of rotation tooth flanks of the outer teeth of the base camshaft and the opposite tooth flanks of the internal teeth of the cam carrier increased. This enlarged game is called a backlash.

As the role of the roller rocker arm moves along the cam profile during operation of the engine, the torque applied by the roller to the cam increases along the forwardly ascending trailing edge of the cam due to the increasing radius, and then reverses suddenly as the rotor rotates Roller moved across the top of the cam. This reversal of direction of the torque causes a sudden change of contact between the inner teeth of the cam carrier and the outer teeth of the basic camshaft, since now in the direction of rotation of the basic camshaft rear tooth flanks of the outer teeth of the basic camshaft are pressed against the opposite tooth flanks of the internal teeth of the cam carrier play, while the front in the direction of rotation Tooth flanks of the external toothing of the basic camshaft and the opposite tooth flanks of the internal toothing of the cam carrier a larger backlash is present. This situation continues as long as the roller moves beyond the rear trailing edge of the cam in the direction of rotation. Thereafter, it comes again to a system change, in which again the front tooth flanks of the external teeth of the basic cam shaft are pressed against the opposite tooth flanks of the internal teeth of the cam carrier back, but with this investment change, the difference in the amounts of torque is significantly lower immediately before and after the investment change ,

However, in the case of abrupt change of gears during the movement of the roller over the cam tips, the difference in the amounts of the torques immediately before and after the system change is very high. As a result, the flanks of the internal and external teeth that come into contact strike each other with great force. This causes audible "ticker" sounds, which are particularly disturbing in idle mode of the internal combustion engine.

Proceeding from this, the present invention seeks to improve a valve train of the type mentioned in that eliminate the disturbing noise or at least reduce.

This object is achieved in that a clearance between the inner teeth and the outer teeth in a radially inwardly located from the cam first peripheral portion of the teeth and in a second circumferential portion of the teeth opposite thereto, ie on the opposite side to the cam cam carrier, is smaller than in a third and fourth peripheral portion, which are arranged between the first and the second peripheral portion.

By this measure, the inner teeth of the cam carrier in the third and fourth peripheral portion is no longer supported on the external teeth when the role of Rollenschlepphebels moves over the cam tip away, so that the cam carrier by the force exerted by the roller rocker on the cam tip force so far in the direction the force is displaced until a tooth located radially inwardly from the cam of the internal toothing of the cam carrier or of the external toothing of the basic camshaft is pressed without play into the opposite tooth gap and thus the rotational backlash is completely eliminated or removed.

Since this is the case at the latest when the contact force exerted by the roller on the cam tip extends radially through the cam tip and the cam with respect to the axis of rotation of the base camshaft, a sudden change of bearing can be avoided at that moment and delayed until a certain point which moves the role of Rollenschlepphebels over the falling edge of the cam. Since the torque exerted by the roller on the cam is smaller because of the shorter power arm in such a subsequent system change, the impact forces occurring during the system change between the flanks coming into contact and thus also the noise level can be at least reduced.

In the context of this invention, a "radially inwardly located from the cam first peripheral portion of the teeth" is understood a peripheral portion extending on both sides of a extending through the cam tip and the axis of rotation longitudinal center plane of the cam carrier over an angular range, which may be from 20 to 45 degrees and does not necessarily need to be symmetrical to the longitudinal center plane. In other words, when viewed in an XY coordinate system perpendicular to the rotation axis in which the cam tip lies on the Y axis and faces upward, the first peripheral portion on either side of the Y axis in the 1st and 4th quadrants is the second peripheral portion on both sides of the Y-axis in the 2nd and 3rd quadrant, the third peripheral portion on both sides of the X-axis in the 1st and 2nd quadrant and the fourth peripheral portion on both sides of the X-axis in the 3rd and 4th quadrant. This also applies to cases where the cam carrier carries a plurality of cams whose cam tips are not aligned with each other in the axial direction of the cam carrier, but in the circumferential direction are slightly offset from each other to provide for a different opening times of the gas exchange valves. In this case, the cam tip is expediently the cam tip of the higher cam or an imaginary cam tip between the cam tips of the two cams.

A preferred embodiment of the invention provides that in the first and in the second circumferential portion, the backlash between opposing tooth flanks of the internal toothing and the external toothing is smaller than in the third and fourth peripheral portion. For this purpose, in the third and fourth peripheral sections expediently the backlash is increased so far that in these two peripheral portions, the internal teeth of the cam carrier can not be supported on the outer teeth of the basic cam before the Verdrehflankenspiel between a radially inwardly located from the cam tooth of the internal teeth of the cam carrier or ., the external toothing of the base camshaft and the associated tooth gap has been completely eliminated.

The enlargement of the backlash in the third and fourth peripheral portion is preferably carried out in that with identical tooth width of the teeth of the external toothing of the basic cam over the entire circumference in the third and fourth peripheral portion of the tooth width of the teeth of the inner toothing of the cam carrier compared to the tooth width of the teeth of the internal teeth of the cam carrier slightly reduced in the first and second peripheral portion and thus the width of the tooth gaps is slightly increased.

Alternatively, a similar result can also be achieved by completely removing the teeth of the inner teeth of the cam carrier or of the outer teeth of the basic camshaft in the third and fourth circumferential sections. The removal of the teeth is harmless because after running in the operation of the valve train or the internal combustion engine usually only a part of the teeth of the meshing gears comes to fruition. Preferably, the teeth of the internal teeth of the cam carrier are removed, and expediently over the entire length of the cam carrier in order to simplify the processing.

In the following the invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it:

1 FIG. 4 is a top view of parts of a valve train for intake valve pairs of three cylinders of a six-cylinder V-engine having a plurality of cam carriers slidable on a base camshaft; FIG.

2 FIG. 2: a schematic cross-sectional view of a cam carrier along the line II-II of FIG 1 ;

3 : a section III magnification magnification 2 ;

4 : a detail of cutting IV in 2 ;

5 FIG. 2 is a simplified schematic cross-sectional view of the basic camshaft and the cam carrier from FIGS 1 to 3 to explain the operation;

6 a schematic cross-sectional view corresponding 2 but from a modified cam carrier;

7 : A simplified schematic cross-sectional view of the base camshaft and the cam carrier off 6 to explain the operation;

8th to 11 FIG. 2: simplified schematic cross-sectional views of a conventional basic camshaft and a conventional cam carrier for explaining the play between the basic camshaft and the cam carrier.

In the valve drive only partially shown in the drawing 1 for pairs of intake valves of three cylinders 2 a V-type 6-cylinder diesel engine with an overhead camshaft rotatably mounted in a cylinder head housing of the diesel engine 3 let the stroke and the opening times of the two of the basic camshaft 3 operated intake valves of each cylinder 2 adjust.

The valve train 1 includes for each cylinder 2 or for each pair of intake valves a rotationally fixed and axially displaceable on the base camshaft 3 mounted cam carrier 4 , as well as an actuator 5 for moving the cam carrier 4 between two axially spaced defined shift positions.

The three hollow cylindrical cam carriers 4 have at their outer periphery in each case two axially spaced cam pairs 6 . 7 on, each of which consists of two cams 8th . 9 exists with different cam contours. Each of the two cam pairs 6 . 7 interacts with a roller of a pivotally mounted roller cam follower (not shown) of the associated inlet valve. By an axial displacement of the cam carrier 4 Can the roll as needed with one of the two cams 8th . 9 of the cam pair 6 respectively. 7 be brought into abutting contact so that they move during each revolution of the basic camshaft 3 once over the cam contour of the cam 8th . 9 moved away while the roller rocker arm pivoted under opening the valve. Through different cam contours of the two cams 8th . 9 For example, the stroke and opening time of each valve may vary depending on the displacement position of the cam carrier 4 regardless of the stroke and the opening time of the valves of the other cylinders 2 be changed depending on the speed, for example.

The axial displacement of a cam carrier 4 on the base camshaft 3 in one of the two defined displacement positions for adjusting the stroke and / or the opening times of the associated intake valves takes place as needed and is always made when Grundkreisabschnitte the cam pairs 6 . 7 opposite to the rollers of the associated drag levers. To shift each of the actuator 5 actuated, the two adjacent drivers 10 that emerges from the actuator 5 extend. When operating the actuator 5 becomes one of the two drivers 10 when extending into a left- or right-handed helical groove 11 in the outer circumference of the cam carrier 4 meshed, the lane taker 10 in one of the two displacement positions opposite. This will be the cam carrier 4 during a subsequent revolution of the basic camshaft 3 as a result of the movement of the driver 10 through the helical groove 11 moved to the left or to the right in the other displacement position.

To the axial displacement of the cam carrier 4 on the base camshaft 3 to allow the hollow cylindrical cam carrier 4 on its inner circumference an internal toothing 12 on that with an external toothing 13 on the base camshaft 3 meshes and between the base camshaft 3 and every cam carrier 4 forms a spline connection with the axial relative mobility, which serves a drive torque M _A ( 10 and 11 ) from the basic camshaft 3 on the cam carrier 4 transferred to. The internal toothing 12 and the external teeth 13 each have a plurality of teeth 14 respectively. 15 on, preferably 24 at the valve gear in the 1 to 4 , To the displacement of the cam carrier 4 To facilitate, grasp the teeth 14 the internal toothing 12 each with game S in one opposite tooth gap between two adjacent teeth 15 the external toothing 13 one, while the teeth 15 the external toothing 12 each with play in an opposite tooth gap between two adjacent teeth 14 the internal toothing 12 intervention. The game S includes a backlash FS between opposing tooth flanks 16 . 17 the teeth 14 . 15 the internal and external teeth 13 . 12 , as well as a head play KS between the teeth of the teeth 14 . 15 and the reason of the associated tooth gaps, as in 3 and 4 shown.

As in the 8th to 11 for the interaction of a conventional cam carrier 18 and a conventional basic camshaft 19 whose interlocking for ease of understanding in the 8th to 11 are shown only schematically with four teeth, the backlash FS leads between the teeth in the event of attack of a lateral force F ₁ on the cam 20 ( 8th ) that in the direction of rotation A of the basic camshaft 19 and the cam carrier 18 front tooth flanks of the teeth of the external toothing of the basic camshaft 19 backlash against the opposite tooth flanks of the teeth of the internal teeth of the cam carrier 18 be pressed while the backlash increases between the direction of rotation A rear tooth flanks of the teeth of the outer teeth of the base camshaft and the opposite tooth flanks of the teeth of the inner toothing of the cam carrier. This enlarged game is referred to as a backlash VFS and is in 8th shown.

Next leads the head play KS in case of one on the top of the cam 20 applied radial force F ₂ ( 9 ) in that when viewed in a direction perpendicular to the axis of rotation of the basic camshaft XY coordinate system with the zero point in the axis of rotation of the basic camshaft 19 in which the cam 20 symmetrical to the Y-axis facing up, the internal teeth of the cam carrier 18 below the cam 20 in the negative direction of the Y-axis from above against the external toothing of the basic camshaft 19 is pressed while on the opposite side of the cam carrier 18 down to slightly stronger from the outer teeth of the basic camshaft 19 is lifted. This is called high play HS and is in 9 shown.

How to get out 9 sees, stays with conventional cam carriers 18 and basic camshafts 19 despite the reduced as a result of the high game HS backlash FS both sides of the upwardly facing tooth of the external teeth of the basic camshaft 19 there is still a residual backlash RFS left over.

The on the cam 20 acting force F is mainly a force generated by the compression of the valve spring of the intake valve, which is the rolling over the cam contour role of Rollenschlepphebels against the cam 20 presses. How best in the 8th to 11 shown is that of the roller on the cam 20 applied force F generally perpendicular to the surface of the cam contour. As a result, the one due to the force F on the cam carrier 18 applied torque M about the axis of rotation of the basic camshaft 19 to that of the basic camshaft 19 on the cam carrier 18 applied driving torque M _{A is} opposite, while the role of the front in the direction of rotation rising edge of the cam 20 moves as indicated by the arrows F ₁ and M ₁ in 10 shown. On the other hand, the torque M reverses its direction as the roller passes over the top of the cam 20 is moved, and is rectified with the drive torque M _A , while the role of the rear in the direction of rotation descending flank of the cam 20 moved as indicated by the arrows F ₂ and M ₂ in 11 shown.

As if from a comparison of 10 and 11 it can be seen, the direction reversal of the torque M leads to a sudden contact change between the internal toothing of the cam carrier 18 and the external teeth of the basic camshaft 20 , This sudden change in the system or edge causes a "ticker" sound, which is especially annoying when the internal combustion engine is idling.

To eliminate or reduce this "ticker" noise points in the in the 1 to 4 illustrated cam carriers 4 the internal toothing 12 an altered geometry through which the backlash FS between the internal teeth 12 and the external teeth 13 the basic camshaft 3 in a radially inward direction from the cam 8th located first peripheral portion 21 the gears 12 . 13 and in a second circumferential section opposite thereto 22 the gears 12 . 13 is smaller than in a third and fourth peripheral portion 23 respectively. 24 the gears 12 . 13 between the first and second peripheral sections 21 and 22 are arranged.

As best by comparing the enlarged section III of the peripheral portion 21 in 3 with the enlarged section IV of the peripheral portion 23 in 4 is visible, the backlash FS is in the peripheral portion 23 larger than in the peripheral section 21 , The backlash FS in the peripheral section 22 corresponds to the backlash FS in the peripheral portion 21 while the backlash FS in the peripheral portion 24 the backlash FS in the peripheral portion 23 equivalent. The larger backlash FS in the two peripheral sections 23 and 24 is achieved in that there compared to the peripheral sections 21 and 22 the width of the teeth 14 the internal toothing 12 of the cam carrier 4 reduced or the width of the tooth gaps between the teeth 14 is enlarged, while the geometry of the teeth 15 and the tooth spaces of the external teeth 13 the basic camshaft 3 remains unchanged and around the entire circumference of the basic camshaft 3 it is the same.

This causes the internal teeth 12 of the cam carrier 4 in the third and fourth peripheral sections 23 and 24 no longer on the external teeth 13 the basic camshaft 3 supported, but only in the first peripheral portion 21 when the role of the roller cam follower moves over the cam tip. At the latest when the role of the roller finger follower passes the cam tip, the cam carrier becomes 4 by the force exerted on the cam tip by the roller rocker radial force so far in the direction of the second peripheral portion 22 , ie in the direction of the cam 8th opposite side of the cam carrier 4 , displaced until a tooth located radially inward of the cam 15 the external toothing 13 the basic camshaft 3 or a tooth located radially inward of the cam 14 the internal toothing 12 of the cam carrier 4 is pressed without play in the opposite tooth gap and thus the circumferential backlash VFS is completely eliminated or taken out.

This process is in 5 shown where the gears 12 . 13 of the cam carrier 4 and the basic camshaft 3 like in the 8th to 10 for clarity and simplification only schematically with four teeth 14 . 15 are shown. How to get out 5 it has the tip of the cam there 20 acting force F results in that the radially inward of the cam 8th located tooth 14 without play engages in the associated tooth gap or even something in the tooth gap "jammed". As a result, a sudden change in the system is prevented at this moment and ensures that the system change is delayed until a point in time in which the role of Rollenschlepphebels already on the rear in the direction of rotation falling edge of the cam 20 emotional. Since there the lever arm of the force acting on the cam F ₂ (see. 11 ) is shorter, also caused by the force F ₂ torque M _{2 is} lower, whereby the volume of the "ticker" noise can be significantly reduced.

The same result is achieved when in the peripheral sections 23 and 24 the teeth 14 the internal toothing 12 of the cam carrier 4 completely removed, as in 6 shown, so that the torque transmission only in the peripheral sections 21 and 22 he follows. By removing the teeth 14 the internal toothing 12 in the two peripheral sections 23 and 24 is there also the game S increased so that the internal teeth 12 of the cam carrier 4 only in the first peripheral section 21 on the external teeth 13 the basic camshaft 3 supports when the role of the roller rocker over the top of the cam 8th moved away. As in 7 schematically, is also in this case, the internal teeth 12 of the cam carrier 4 by the radial force F exerted on the cam tip by the roller rocker arm in the first peripheral section 21 radially against the external teeth 13 the basic camshaft 3 pressed while along the third and fourth peripheral portion 22 . 24 no support takes place. As a result, here also the cam carrier 4 be displaced in the direction of the force F until a tooth located radially inwardly of the cam 15 the external toothing 13 the basic camshaft 3 is pressed play into the associated tooth gap, as in 7 shown schematically, and thus the backlash is completely eliminated.

LIST OF REFERENCE NUMBERS

1

valve train

2

cylinder

3

base camshaft

4

cam support

5

actuator

6

cam pair

7

cam pair

8th

cam

9

cam

10

takeaway

11

helical groove

12

internal gearing

13

external teeth

14

tooth

15

tooth

16

tooth flank

17

tooth flank

18

cam support

19

base camshaft

20

cam

F

force

F ₁

force

F ₂

force

M _A

drive torque

M ₁

torque

M ₂

torque

A

direction of rotation

FS

backlash

KS

head game

VFS

backlash

HS

high game

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1608849 B1 [0003]

Claims (10)

Valve gear for gas exchange valves of an internal combustion engine with at least one rotatable about an axis of rotation base camshaft having an external toothing, and at least one with respect to the base camshaft axially displaceable cam carrier, which has a meshing with the external teeth internal teeth and at least one cam, characterized in that a game between the internal toothing ( 12 ) of the cam carrier ( 4 ) and the external teeth ( 13 ) of the basic camshaft in a radially inward direction from the cam ( 8th ) located first peripheral portion ( 21 ) of the gears ( 12 . 13 ) and in a second circumferential section (cf. 22 ) of the gears ( 12 . 13 ) is smaller than in a third and fourth peripheral portion ( 23 . 24 ) of the gears ( 12 . 13 ), each between the first and the second peripheral portion ( 21 . 22 ) are arranged. Valve gear according to claim 1, characterized in that in the first and in the second peripheral portion ( 21 . 22 ) of the gears ( 12 . 13 ) a backlash (FS) between opposing tooth flanks ( 16 . 17 ) of teeth ( 14 respectively. 15 ) of the internal toothing ( 12 ) and the external teeth ( 13 ) is smaller than in the third and fourth peripheral sections ( 23 . 24 ). Valve gear according to claim 1 or 2, characterized in that the clearance between the internal teeth ( 12 ) and the external teeth ( 13 ) in the first, second, third and fourth peripheral sections ( 21 . 22 . 23 . 14 ) is dimensioned such that a radially inwardly from a cam tip of the cam ( 8th . 9 ) located tooth ( 14 respectively. 15 ) of the internal toothing ( 12 ) of the cam carrier ( 4 ) or the external toothing ( 13 ) the basic camshaft is pressed without play in an opposite tooth gap when a radial force F on the tip of the cam ( 8th . 9 ) is exercised. Valve gear according to one of the preceding claims, characterized in that the internal toothing ( 12 ) of the cam carrier ( 4 ) and / or the external toothing ( 13 ) of the basic camshaft ( 3 ) in the first and second peripheral sections ( 21 . 22 ) Teeth ( 14 respectively. 15 ) having a tooth width which differs from the tooth width of teeth ( 14 respectively. 15 ) of the internal toothing ( 12 ) of the cam carrier ( 4 ) and / or the external toothing ( 13 ) of the basic camshaft ( 3 ) in the third and fourth peripheral sections ( 23 . 24 ) is different. Valve gear according to claim 4, characterized in that the tooth width of the teeth ( 14 ) of the internal toothing ( 12 ) of the cam carrier ( 4 ) in the first and second peripheral sections ( 21 . 22 ) is greater than the tooth width of the teeth ( 14 ) of the internal toothing ( 12 ) of the cam carrier ( 4 ) in the third and fourth peripheral sections ( 23 . 24 ). Valve gear according to claim 4 or 5, characterized in that the external toothing ( 13 ) of the basic camshaft ( 3 ) in the first, second, third and fourth peripheral sections ( 21 . 22 . 23 . 24 ) Teeth ( 15 ) having the same cross-sectional dimensions or the same tooth width. Valve gear according to one of claims 1 to 3, characterized in that the internal toothing ( 12 ) of the cam carrier ( 4 ) and / or the external toothing ( 13 ) of the basic camshaft ( 3 ) in the third and fourth peripheral sections ( 23 . 24 ) has no teeth. Valve gear according to one of the preceding claims, characterized in that the first, second, third and fourth peripheral portions ( 21 . 22 . 23 . 24 ) each extend over a circumferential angle of about 60 to 90 degrees. Valve gear according to one of the preceding claims, characterized in that the smaller clearance between the internal toothing ( 12 ) of the cam carrier ( 4 ) and the external teeth ( 13 ) of the basic camshaft ( 3 ) in the first and second peripheral sections ( 21 . 22 ) over the entire length of the cam carrier ( 4 ) is available. Internal combustion engine, characterized by at least one valve drive ( 1 ) according to one of the preceding claims.

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