Variable valve drive having a rocker lever

Abstract

A variable valve drive for a lifting valve, such as a charge-exchange valve of an internal combustion engine, that is periodically movable between closed and open positions indirectly by way of a cam via a rocker lever. The variable valve drive includes a switchable rocker lever arrangement for the actuation of the lifting valve, having a transmission rocker lever and a valve rocker lever which are mounted pivotably on different rocker lever axles parallel to the camshaft axis. The valve rocker lever, is in operative contact with the lifting valve at a first end, and has a roller, at a second end. The transmission rocker lever, is in engagement with a cam of the camshaft and, is operatively connected to the roller of the valve rocker lever.

Claims

1. A variable valve drive for a lifting valve, which is periodically movable between a closed position and an open position indirectly by way of a cam of a camshaft, the variable valve drive comprising: a switchable rocker lever arrangement for actuation of a lifting valve, having a transmission rocker lever and a valve rocker lever mounted so as to be pivotable on different rocker lever axles which are each parallel to a camshaft axis, wherein the valve rocker lever is in operative contact with the lifting valve at a first distal end and has a roller at a second distal end and pivots about a fulcrum located between the first and second distal ends, wherein the transmission rocker lever is in engagement with a cam of the camshaft at a first end and is operatively connected, by way of a contour surface to the roller of the valve rocker lever at a second end, in such a way that a rocking movement of the transmission rocker lever generates a rocking movement of the valve rocker lever, during which the roller of the valve rocker lever rolls on the contour surface, and wherein the contour surface (a) has a first rolling region which forms a base circle contour which generates no valve lift when the roller of the valve rocker lever rolls on the base circle contour, and (b) has a second rolling region which adjoins the first rolling region and which has a ramp contour; and an actuating device for the switching of the rocker lever arrangement, wherein the contour surface can be rotated about the rocker lever axle of the transmission rocker lever to generate a displacement of a rolling region of the roller of the valve rocker lever on the contour surface.

2. A variable valve drive according to claim 1, wherein the lifting valve is a charge-exchange valve of an internal combustion engine.

3. The variable valve drive according to claim 1, wherein the contour surface has a third rolling region which adjoins the second rolling region and which generates a valve position with maximum valve lift when the roller of the valve rocker lever rolls on the third rolling region.

4. The variable valve drive according to claim 1, wherein the transmission rocker lever has a first lever, which is in engagement with the cam of the camshaft, and a second lever, having the contour surface which is operatively connected to the roller of the valve rocker lever, wherein the first lever and the second lever are coupled to one another such that a rocking movement of the first lever generated by the cam leads to a corresponding rocking movement of the second lever about the rocker lever axle of the transmission rocker lever, and wherein, by way of the actuating device, a rotational position of the second lever relative to the first lever can be varied in order to vary a rolling region of the roller of the valve rocker lever on the contour surface.

5. The variable valve drive according to claim 4, wherein the actuating device is designed to vary a rotational position of the second lever relative to the first lever in continuously variable fashion.

6. The variable valve drive according to claim 4, wherein the actuating device is designed to vary a rotational position of the second lever relative to the first lever into two predetermined positions, such that switching is possible between two different valve lifts.

7. The variable valve drive according to claim 4, wherein the actuating device is designed as a hydraulic switching unit.

8. The variable valve drive according to claim 4, wherein the actuating device has a hydraulically actuated switching pin which, at one end, is fastened to the first lever and, at another end, is fastened to the second lever, and wherein a deployment of the hydraulically actuated switching pin varies a rotational position of the second lever relative to the first lever.

9. The variable valve drive according to claim 4, wherein the actuating device is designed as an electrical or mechanical actuating device.

10. The variable valve drive according to claim 4, wherein the first lever and the second lever are coupled to one another by way of a driver.

11. The variable valve drive according to claim 1, wherein the transmission rocker lever is preloaded by way of a restoring spring such that the transmission rocker lever is pushed against the camshaft.

12. The variable valve drive according to claim 4, wherein the first lever of the transmission rocker lever is preloaded by way of a restoring spring such that the transmission rocker lever is pushed against the camshaft.

13. The variable valve drive according to claim 3, wherein the contour surface has a fourth rolling region, which adjoins the third rolling region and which forms a ramp contour, and a fifth rolling region, which adjoins the fourth rolling region, and wherein the fifth rolling region has a constant radial spacing to the axis of the rocker lever axle of the transmission lever, which spacing is greater than the radial spacing of the third rolling region and the radial spacing of the first rolling region.

14. The variable valve drive according to claim 1, wherein the valve rocker lever, at its valve-side end, has a receptacle in which there is received a hydraulic valve-clearance compensating element or a screw with an elephant-foot configuration.

15. A motor vehicle having a variable valve drive for a lifting valve, which is periodically movable between a closed position and an open position indirectly by way of a cam of a camshaft, the variable valve drive comprising: a switchable rocker lever arrangement for actuation of the lifting valve, having a transmission rocker lever and a valve rocker lever mounted so as to be pivotable on different rocker lever axles which are each parallel to camshaft axis, wherein the valve rocker lever, is in operative contact with the lifting valve at a first distal end and has a roller at a second distal end and pivots about a fulcrum located between the first and second distal ends, wherein the transmission rocker lever is in engagement with a cam of the camshaft at a first end and, is operatively connected, by way of a contour surface to the roller of the valve rocker lever at a second end, in such a way that a rocking movement of the transmission rocker lever generates a rocking movement of the valve rocker lever, during which the roller of the valve rocker lever rolls on the contour surface, and wherein the contour surface (a) has a first rolling region which forms a base circle contour which generates no valve lift when the roller of the valve rocker lever rolls on the base circle contour, and (b) has a second rolling region which adjoins the first rolling region and which has a ramp contour; and an actuating device for the switching of the rocker lever arrangement, wherein the contour surface can be rotated about the rocker lever axle of the transmission rocker lever to generate a displacement of a rolling region of the roller of the valve rocker lever on the contour surface.

16. The motor vehicle according to claim 15, wherein the motor vehicle is a utility vehicle.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a side view of a valve drive according to an embodiment of the present disclosure;

(2) FIG. 2 shows a perspective side view of a valve drive according to an embodiment of the present disclosure;

(3) FIG. 3 shows a detail view of the coupling between valve rocker lever and transmission rocker lever according to an embodiment of the present disclosure;

(4) FIG. 4 shows a side view of a second lever of the transmission rocker lever according to an embodiment of the present disclosure;

(5) FIG. 5 shows a side view of a second lever of the transmission rocker lever according to a further embodiment of the present disclosure;

(6) FIG. 6 shows an illustration of various settable lift curves of the lifting valve;

(7) FIG. 7 shows a perspective illustration of the transmission rocker lever in a first switching state according to an embodiment of the present disclosure; and

(8) FIG. 8 shows the transmission rocker lever from FIG. 7 in a second switching state.

(9) Identical parts are denoted by the same reference designations in the figures, such that the various views of the valve drive shown in the figures can be understood from this also.

DESCRIPTION

(10) FIGS. 1 and 2 show a side view and a perspective side view, respectively, of a variable valve drive 1 according to an embodiment of the present disclosure. The valve drive 1 serves for the actuation of charge exchange valves (not shown) of an internal combustion engine, which charge exchange valves are periodically movable between a closed position and an open position indirectly by way of a cam 2 of a camshaft 3.

(11) The valve drive 1 comprises a switchable rocker lever arrangement for the actuation of the lifting valves. The rocker lever arrangement comprises a first rocker lever (valve rocker lever) 20, which is mounted so as to be pivotable about a rocker lever axle 23, and a second rocker lever (transmission rocker lever) 10, which is mounted so as to be pivotable about a further rocker lever axle 13. The two rocker lever axles 13, 23 are spatially separate but are both parallel to the axis of the camshafts 3.

(12) The valve rocker lever 20 is, at a valve-side end 21, that is to say by way of its valve-side lever arm 21, in operative contact with two lifting valves (not shown). The valve-side lever arm 21 of the valve rocker lever 20 is, for this purpose, designed as a two-valve lever arm for the purposes of actuating two charge exchange valves simultaneously. For this purpose, the valve-side lever arm 21 is of forked form, as can be seen in FIG. 2. As can also be seen in FIG. 2, two such valve rocker lever arrangements 10, 20 are arranged one behind the other in an axial direction of the camshaft for the purposes of actuating four lifting valves. A receptacle 24 is arranged at each valve-side end of the lever arm 21. The receptacle 24 may be used for the mounting of a hydraulic valve-clearance compensating element 25 such as is known per se. Instead of a hydraulic valve-clearance compensating element, it is also possible, with corresponding machining, for there to be received in the receptacle 24 a screw with an elephant-foot configuration, by way of which a valve clearance can be manually readjusted.

(13) Hydraulic valve-clearance compensating elements in internal combustion engines are known per se and serve for compensating in particular the changes in length dimensions of the charge exchange valves over the service life, in such a way that reliable valve closure is ensured in the base circle phase of the cam that actuates the valve. Here, it is on the other hand sought for the cam lift to be transmitted to the valve, and thus converted into a valve lifting movement, without losses. The mode of operation of such hydraulic valve-clearance compensating elements which are arranged in the force flow of a valve controller, in particular of an internal combustion engine, is assumed to be known.

(14) The valve rocker lever 20 is held on a rocker lever bearing block (not shown), wherein the rocker lever axle 23 is arranged on the rocker lever bearing block, onto which rocker lever axle the valve rocker lever 20 is, by way of an associated bore, pivotably mounted and held by way of an axial position-securing means. In the present exemplary embodiment, the axial position-securing means is designed as an engagement element-counterpart element connection between the bearing block and the rocker lever, in the case of which an engagement element oriented transversely with respect to the axial direction, for example in the form of a ring-shaped web 27, engages pivotably into an associated counterpart element (not illustrated) with axial flank support. The axial position-securing means may however also be realized, in a manner known per se, by way of abutment surfaces on the rocker lever flanks. Said flanks may be created for example by calibration of the forged blank or by mechanical machining. At the bearing block side, the fixing may likewise be realized by way of correspondingly machined surfaces and by way of discs and securing rings. Furthermore, axial position-securing means between a rocker lever and the axle are known. For example, for this purpose, a region of the axle which is surrounded by the bore of the rocker lever has a ring-shaped groove in which there runs a circlip, which simultaneously runs by way of its outer ring-shaped section in a ring-shaped groove of the rocker lever.

(15) At its opposite end 22 in relation to the rocker axle 23, that is to say at the camshaft-side lever arm 22, a roller 26 is arranged on the distal end of the lever arm 22.

(16) The transmission rocker lever 10 is in engagement, at a camshaft-side end 11, with the cam 2 of the camshaft 3. For this purpose, a roller 18, for example a thrust roller, is arranged on the camshaft-side end 11, which roller rolls on the cam 2 of the camshaft 3 and thus picks off the cam movement. The transmission rocker lever 10 is furthermore, at the other end 12 in relation to the rocker lever axle 13, operatively connected by way of a lift-defining surface, referred to as contour surface 16, to the roller 26 of the valve rocker lever 20, that is to say the roller 26 of the valve rocker lever 20 rolls on the contour surface 16 during a rocking movement of the transmission rocker lever 10 generated by the cam movement, whereby a corresponding rocking movement of the valve rocker lever 20 is generated. The transmission rocker lever 10, by way of its rocking movement, transmits the cam movement to the valve rocker lever 20, which in turn, by way of its correspondingly resulting rocking movement, generates the valve lift. In this way, the transmission rocker lever 10 and valve rocker lever 20 are connected in series. The camshaft 3 and valve rocker lever 20 may, for this purpose, be designed in a manner known per se, and are coupled to one another in terms of movement by way of the transmission lever 10 arranged in between.

(17) The contour surface 16 on which the valve rocker lever roller 26 is supported serves as a rolling region on which the valve rocker lever roller 26 rolls back and forth during the transmission of the rocking movement of the transmission rocker lever 10 to the valve rocker lever 20. The lift characteristic of the lifting valve can thus be predefined, and also varied, by way of the design of said contour surface 16 which serves as rolling surface.

(18) FIG. 3 shows a detail view of the coupling between valve rocker lever 20 and the transmission rocker lever 10 at the contour surface 16. In this exemplary embodiment, the contour surface 16 has three different regions 16a, 16b and 16c, which can serve as rolling regions for the roller 26.

(19) The first rolling region 16a forms the base circle contour, that is to say the valve rocker lever 20 generates no valve lift when the roller 26 rolls on said region. The spacing of the points on the first rolling surface 16a to the axis of the rocker lever axle 13, that is to say the radial spacing R1 thereof, is constant. The contour surface 16 furthermore comprises a second rolling region 16b which directly adjoins the first rolling region 16a and which has a ramp contour. On the second rolling region, the radial spacing of the rolling points increases from a value R1 to a value R2. Thus, if the roller 26 rolls on the second region 16b proceeding from the first region 16a, the valve rocker lever 20 rocks more the further the roller 26 rolls on the second rolling region 16b. Consequently, the valve lift that is generated is greater the further the roller 26 of the valve rocker lever 20 rolls on the second rolling region 16b proceeding from the first rolling region 16a.

(20) The second rolling region 16b is adjoined by a third rolling region 16c, which has a constant radial spacing R2 and which generates a valve position with maximum valve lift if the roller 26 of the valve rocker lever 20 rolls on the third rolling region 16c.

(21) The valve drive 1 furthermore comprises an actuating device 30 for the switching of the rocker lever arrangement 10, 20, by way of which actuating device the contour surface 16 can be rotated about the rocker lever axle 13 of the transmission rocker lever 10 in order to generate a displacement of a rolling region of the roller 26 of the valve rocker lever 20 on the contour surface 16. In this way, that region of the contour surface 16 which is rolled on, that is to say picked off, by the roller of the valve rocker lever is varied, along with the resulting valve lift and/or the valve opening and/or closing times.

(22) For this purpose, the embodiment of the transmission rocker lever 10 shown in FIG. 1 comprises a first lever 14, hereinafter also referred to as cam follower lever, which is in engagement, by way of a roller 18, with the cam 2 of the camshaft 3. The transmission rocker lever 10 furthermore comprises a second lever 15, hereinafter referred to as contour lever, which has the contour surface 16 which is operatively connected to the roller 26 of the valve rocker lever 20.

(23) The cam follower lever 14 and the contour lever 15 are coupled to one another in terms of movement, in such a way that a rocking movement of the cam follower lever 14 generated by the cam 2 leads to a corresponding rocking movement of the contour lever 15 about the rocker lever axle 13 of the transmission rocker lever 10. By way of an actuating device 30, however, a rotational position of the contour lever 15 relative to the cam follower lever 14 can be varied in order to vary a rolling region of the roller 26 of the valve rocker lever 20 on the contour surface. In each of the different settable rotational positions, the cam follower lever 14 and contour lever 15 are then again coupled in terms of movement with regard to a pivoting movement (rocking movement) about the rocker lever axle 13.

(24) The different settable rolling regions are illustrated in FIG. 4. FIG. 4 shows a side view of the contour lever 15 of the transmission rocker lever 10 according to an embodiment of the present disclosure.

(25) For example, the actuating device, which is discussed in more detail below on the basis of FIGS. 7 and 8, may be designed to set to different rotational positions of the contour lever 15 relative to the cam follower lever 14, resulting in two different rolling regions a1 and a2 for the roller 26 of the valve rocker lever 10.

(26) In a first set rotational position, during a rocking movement of the transmission rocker lever 10 or of the contour lever 15 generated by the cam 2, the roller 26 rolls back and forth on the first rolling region a1, which encompasses almost the entire first rolling region 16a and a first subregion of the second rolling region 16b. By contrast, in a second set rotational position, during a rocking movement of the transmission rocker lever 10 or of the contour lever 15 generated by the cam 2, the roller 26 rolls back and forth on the second rolling region a2, which encompasses almost the entire second rolling region 16b and a subregion of the third rolling region 16c.

(27) If the valve drive 1 is switched from the rolling region a1 to the rolling region a2, the valve lift that can be generated by the camshaft 3 is increased. As can be seen in FIG. 4, the radial spacing at the right-hand end region of the region a2 is still equal to the radial spacing in the first rolling region 16a, such that, at this location, a closed position of the lifting valves is generated.

(28) The actuating device may be designed such that it can set a rotational position of the second lever relative to the first lever into two predetermined positions, such that switching is possible between two different, predetermined rolling regions on the contour surface 16, and thus valve lifts. Alternatively, the actuating device may also be designed such that more than two predetermined rotational positions can be set, or the rotational position is continuously variable within predefined limits. In the latter variant, the valve lift can be varied in continuous fashion.

(29) FIG. 5 shows a side view of the contour lever 515 of the transmission rocker lever 10 according to a further embodiment of the present disclosure. In this embodiment, the contour lever has a contour surface 516 with five different rolling regions 16a-16e. The first rolling region 16a again forms the base circle contour with constant radial spacing R1 to the axis of the axle 13. The adjoining second rolling region 16b in turn forms a ramp contour with an increasing radial spacing, which radial spacing has increased to the value R2 at the end of the second rolling region. The adjoining third rolling region 16c then in turn forms a region with a constant radial spacing R2. Said third rolling region 16c is then adjoined, in the rolling direction, by a fourth rolling region 16d, which in turn forms a ramp contour. At the end of the fourth rolling region 16d, the radial spacing has increased to the value R3. The fourth region is then adjoined by a fifth rolling region 16e, which in turn has a constant radial spacing. The rolling points on the fifth rolling region 16e have a constant radial spacing to the axis of the rocker lever axle of the transmission lever. The radial spacing R3 of the fifth rolling region 16e is greater than the radial spacing R2 of the third rolling region 16c and greater than the radial spacing R1 of the first rolling region 16a. In this design variant with five rolling regions, the third region 16c forms a middle position, in which the lifting valve is briefly, that is to say when the roller 26 rolls on the third region 16c, held open in an open position with a constant lift height which is smaller than the maximum lift height.

(30) FIG. 6 illustrates different lift curves that can be set by way of the valve drive. The angle of rotation a of the camshaft 3 is plotted on the abscissa. The valve lift d is plotted on the ordinate. The curves 61 to 64 show four different settable valve lift profiles as a function of the angle of rotation of the camshaft. Each of the four curves 61 to 64 corresponds to a particular rotational position, set by way of the actuating device, of the second lever 15 relative to the first lever 14 of the transmission rocker lever 10. Here, the curve 61 corresponds to a set rotational position which generates the largest valve lift and the shortest valve closing times, whereas, by contrast, the curve 65 generates the smallest valve lift and the longest valve closing times.

(31) FIGS. 7 and 8 illustrate the mode of operation of the hydraulic actuating device. Here, FIG. 7 is a perspective illustration of the two-part construction of the transmission rocker lever 10 in a first switching state.

(32) It has already been discussed above that the transmission rocker lever 10 has a two-part construction. Here, the transmission rocker lever 10 has a first lever (cam follower lever) 14, which is in engagement with the cam 2 of the camshaft 3, and a second lever (contour lever) 15, which has the contour surface 16 which is operatively connected to the roller 26 of the valve rocker lever 20.

(33) The cam follower lever 14 and the contour lever 15 are coupled to one another in terms of movement by way of the driver 32, which presses against the abutment surface 19, in such a way that a rocking movement of the cam follower lever 14 generated by the cam 2 leads to a corresponding rocking movement of the contour lever 15 about the rocker lever axle 13 of the transmission rocker lever 10. Said movement coupling of cam follower lever 14 and contour lever 15 may also be realized not by way of the driver that is shown but by way of other positively locking or hydraulic connections, for example by way of an internal toothing, a pivoting motor principle, etc., and may be attached at a location other than that shown.

(34) By way of a hydraulic actuating device 30, however, a rotational position of the contour lever 15 relative to the cam follower lever 14 can be varied in order to vary a rolling region of the roller 26 of the valve rocker lever 20 on the contour surface 16.

(35) For this purpose, the hydraulic actuating device 30 comprises a hydraulically actuated pin 31, also referred to in this document as switching pin 31, which is fastened by way of one end to the cam follower lever 14 and which is arranged by way of another end on the contour lever 15.

(36) As can be seen in FIGS. 7 and 8, the cam follower lever 14 has, for this purpose, a pin receptacle 33 for holding the switching pin 31, in which pin receptacle there is arranged a pressure chamber (not shown) which can be charged with a hydraulic liquid. The hydraulic lines for the supply to the pressure chamber and the control lines of the actuating device 30 are not illustrated. The other end of the switching pin is held in a receptacle on the contour lever 15, wherein the receptacle simultaneously forms the driver 32.

(37) Upon activation of the actuating device, the pressure chamber is charged with hydraulic liquid, whereby the switching pin 31 is moved from the retracted state shown in FIG. 7 into the deployed state shown in FIG. 8.

(38) As a result of the deployment of the switching pin 31, the contour lever 15 rotates clockwise into a different rotational position relative to the cam follower lever 14. As a result, the contour surface 16 likewise rotates clockwise. Thus, the rolling region for the roller 26 of the valve rocker lever 20 changes. Depending on the design of the actuating device 30, different deployment positions of the switching pin 31, and thus different rotational positions, can be set by controlling the pressure level in the pressure chamber.

(39) The cam follower lever 15 is preloaded by way of a restoring spring 17 via a restoring spring abutment point 17a, such that the entire transmission rocker lever 10 is forced against the camshaft 3 by the spring force of the restoring spring.

(40) Even though the present disclosure has been described with reference to particular exemplary embodiments, it is self-evident to a person skilled in the art that numerous changes may be made, and equivalents used as substitutes, without departing from the scope of the present disclosure. Furthermore, numerous modifications may be made without departing from the associated scope. Consequently, the present disclosure is not intended to be restricted to the exemplary embodiments disclosed, but rather is intended to encompass all exemplary embodiments which fall within the scope of the appended patent claims. In particular, the present disclosure also claims protection for the subject matter and the features of the subclaims independently of the claims to which reference is made.

LIST OF REFERENCE DESIGNATIONS

(41) 1 Variable valve drive 2 Cam 3 Camshaft 10 Transmission rocker lever 11 First end 12 Second end 13 Rocker lever axle of the transmission rocker lever 14 First lever or cam follower lever 15, 515 Second lever or contour lever 16, 516 Contour surface 16a, 16b, 16c, 16d, 16e Rolling regions 17 Restoring spring 17a Abutment point for restoring spring 18 Roller 19 Abutment surface 20 Valve rocker lever 21 First end or valve-side lever arm 22 Second end or camshaft-side lever arm 23 Rocker lever axle of the valve rocker lever 24 Receptacle 25 Hydraulic valve-clearance compensating element 26 Roller 27 Ring-shaped web 30 Actuating device 31 Hydraulic switching pin 32 Driver 33 Receptacle 61-65 Valve lift profile curve a1 First rolling region a2 Second rolling region R1, R2, R3 Radial spacing of the rolling region to the axis of the rocker lever axle