Valve operating device, in particular for an internal combustion engine

Abstract

A valve operating device, in particular for an internal combustion engine, has a camshaft, a cam unit mounted in an axially moveably manner on the camshaft, and an actuator unit which has an actuator for displacing the cam unit on the camshaft. The actuator is periodically mechanically forcibly decoupled during operation.

Claims

1. A valve operating device for an internal combustion engine, comprising: a camshaft; a cam unit mounted on the camshaft in an axially moveable manner; and an actuator unit which has an actuator having an electric motor and a spindle for adjusting the cam unit; wherein the camshaft is connected by toothing to an engagement element via which the cam unit is coupled to the actuator unit; wherein, by rotating the spindle using the electric motor, a switching element is shiftable in an axial direction of the spindle and axially relative to the camshaft; and wherein the switching element periodically mechanically decouples from the engagement element and is always disengaged from the engagement element when the cam unit is not adjusted, thereby periodically temporarily forcibly decoupling the actuator from the cam unit during operation relative to a rotational angle of the camshaft and always decoupling the actuator from the cam unit while valves are being operated by the cam unit.

2. The valve operating device according to claim 1, wherein the engagement element is partially interrupted along a circumference of the cam unit.

3. The valve operating device according to claim 1, wherein the engagement element is a crescent-shaped gill.

4. A motor vehicle, comprising: an internal combustion engine; and the valve operating device according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic depiction of a motor vehicle having an internal combustion engine which comprises a valve operating device according to the invention, and having a multi-stage transmission in a schematic depiction;

(2) FIG. 2 is a schematic depiction of the valve drive device according to the invention, having a camshaft, a cam unit and an actuator unit; and

(3) FIG. 3 shows the valve operating device according to the invention having the camshaft, the cam unit and the actuator unit in a schematic sectional depiction along sectional line III-III of FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 schematically shows a motor vehicle 17. The motor vehicle 17 comprises a drive train, by means of which the drive wheels 18 not visible in more detail of the motor vehicle 17 are driven. The drive train comprises an internal combustion engine 11, The internal combustion engine 11 is formed by a combustion motor. Furthermore, the motor vehicle 17 has a multi-stage transmission 19. The internal combustion engine 11 has a driven crankshaft which is connected to a transmission input element of the multi-stage transmission 19. The multi-stage transmission 19 is formed by a motor vehicle transmission. The multi-stage transmission 19 forms part of the drive train of the motor vehicle 17. The internal combustion engine 11 comprises at least one valve operating device 10. Preferably, the internal combustion engine 11 comprises several valve operating devices 10. The internal combustion engine 11 is designed as a motor vehicle internal combustion engine which is provided to convert chemical energy into kinetic energy which serves in particular to propel a motor vehicle 17. The internal combustion engine 11 has several cylinders which each have several valves 20, 20′. The internal combustion engine 11 has two valves 20, 20′, each designed as inlet valves for one cylinder and two valves each designed as exhaust valves for each cylinder. In principle, it is also conceivable that the internal combustion engine 11 has a different number of valves 20, 20′. Here, the valves 20, 20′ are schematically depicted by their actuation plane in FIG. 2.

(5) The valve operating device 10 is provided to actuate the valves 20, 20′ of the internal combustion engine 11. The valve operating device 10 has a camshaft 12. The valve operating device 10 has the camshaft 12 for actuating the valves 20, 20′. In FIG. 2, only part of the camshaft 12, which is assigned to a cylinder that is not depicted in detail, is depicted. In addition, the valve operating device 10 has another camshaft which is not depicted in detail. The camshaft 12 depicted is, for example, formed as an intake camshaft, and the camshaft not depicted in detail is an exhaust camshaft. In the following, only the part of the camshaft 12 described in FIGS. 2 and 3 is described in more detail. The description can be applied to the part of the camshaft 12 which is not depicted in detail as well as the camshaft not depicted in detail.

(6) The camshaft 12 is rotatably supported by a camshaft bearing not depicted in detail. For this purpose, the camshaft bearing comprises several support elements fixed to the housing which store the camshaft 12. Here, the camshaft 12 is rotatably mounted about an axis of rotation 21. The axis of rotation 21 of the camshaft 12 is aligned substantially in parallel to an axis of rotation of a crankshaft of the internal combustion engine 11. The camshaft 12 is driven by the crankshaft via a coupling not depicted in detail. The valve operating device 10 comprises one cam unit 13 per cylinder. FIG. 2 shows an example of a cam unit 13. The cam unit 13 is mounted in an axially moveable manner on the camshaft 12. The cam unit 13 is non-rotatably coupled to the camshaft 12. In particular, the cam unit 13 is connected to the camshaft 12 via a toothing 22. The cam unit 13 is provided for actuating the valves 20, 20′. The cam unit 13 has a multi-track cam 23, 23′ for each valve 20, 20′. The cam unit 13 has two multi-track cams 23, 23′. Each of the multi-track cams 23, 23′ has three cam tracks 24, 24′, 25, 25′, 26, 26′. In principle, it is also conceivable that the cam unit 13 has only two or more than three cam tracks 24, 24′, 25, 25′, 26, 26′ for each multi-track cam 23, 23′. The cam tracks 24, 24′, 25, 25′, 26, 26′ each have different contours and thus actuate the respective valve 20, 20′ with correspondingly different valve strokes. In a first switching position of a cam unit 13, the first cam tracks 24, 24′ actuate the respective valve 20, 20′. The valves 20, 20′ are actuated with a medium stroke, for example. In a second switching position of the cam unit 13, the second cam tracks 25, 25′ actuate the respective valve 20, 20′. The valves 20, 20′ are actuated with a large stroke, for example. In a third switching position of the cam unit 13, the third cam tracks 26, 26′ actuate the respective valve 20, 20′ (FIG. 2). The valves 20, 20′ are actuated with a small stroke, for example. The actuation of a valve 20, 20′ by a cam track 24, 24′, 25, 25′, 26, 26′ is carried out in a manner known to a person skilled in the art.

(7) Furthermore, the valve operating device 10 has an actuator unit 14. The valve operating device 10 has an actuator unit 14 for adjusting the cam unit 13 on the camshaft 12 between the three switching positions. The actuator unit 14 has an actuator 15. The actuator 15 is formed by a shift actuator. The actuator 15 is provided for adjusting the cam unit 13 on the camshaft 12. The actuator 15 is provided to move the cam unit 13 axially on the camshaft 12 in order to bring the different cam tracks 24, 24′, 25, 25′, 26, 26′ of the multi-track cams 23, 23′ into engagement with the respective valve 20, 20′. Here, the actuator 15 is designed as an electronically controlled unit. The actuator 15 comprises an electric motor 27 and a spindle 28, which can be driven by the electric motor 27 in both directions of rotation. To convert the rotation of spindle 28 into a linear movement, the actuator 15 has a switching element 29. The switching element 29 is designed as a threaded nut. The switching element 29 has an internal thread not depicted in detail, via which the switching element 29 is supported on the spindle 28. By rotating the spindle 28 by means of the electric motor 27, the switching element 29 can be shifted in the axial direction of spindle 28. Instead of a spindle 28, a guide rail or a cable device can be used as a support for the switching element 29. The actuator 15 is arranged in parallel offset to the camshaft 12.

(8) The cam unit 13 also has an engagement element 16. The cam unit 13 is coupled to the actuator unit 14 via the engagement element 16. The cam unit 13 is coupled to the actuator 15 via the engagement element 16. The axially moveable switching element 29 of the actuator 15 is operatively connected to the engagement element 16. The engagement element 16 is designed as a narrow peripheral gill. The actuating element 16 is partially interrupted along a periphery of the cam unit 13. The actuating element 16 is interrupted in the peripheral direction of the cam unit 13. Thus in the peripheral direction around the cam unit 13, the engagement element 16 does not extend completely around the cam unit 13. The engagement element 16 is designed as a gill. The engagement element 16 is formed by a gill rotating around 180° of the periphery. The engagement element 16 is formed by a crescent-shaped gill. The engagement element 16 is designed as a crescent moon-shaped gill. In principle, however, a different design of the engagement element 16, which would appear useful to a person skilled in the art, would also be conceivable. The engagement element 16 is designed without an incline in the axial direction and has a constant width in the peripheral direction of the camshaft 12. The engagement element 16 is arranged between the multi-track cams 23, 23′ of the cam unit 13. The switching element 29 is temporarily connected positively to the engagement element 16. For this purpose, the switching element 29 has a recess in which the engagement element 16 formed as a gill engages. The engagement element 16 forms an interface for applying a displacement force acting in the axial direction to the cam unit 13. In the exemplary embodiment shown, the displacement force acting in the axial direction is only applied by the actuator 15. It is independent of a rotational movement of the camshaft 12.

(9) The actuator 15 is periodically mechanically forcibly decoupled during operation. During operation, the actuator 15 is periodically temporarily decoupled from the cam unit 13 relative to a speed of the camshaft 12. During operation, the actuator 15 is periodically temporarily forcibly decoupled from the cam unit 13 relative to an angle of rotation of the camshaft 12. Furthermore, the actuator 15 is always temporarily forcibly decoupled from the cam unit 13 when the cam unit 13 should not be adjusted, i.e., especially when the valves 20, 20′ are being operated by the cam unit 13. The forced decoupling is carried out mechanically by means of the engagement element 16. The engagement element 16 has the interruption for this purpose. The interruption has such an arrangement that, when the interruption is facing the actuator 15, the cam unit 13 is actuating the valves 20, 20′. The interruption thus always faces the actuator 15 when the cam unit 13 should not be adjusted, especially when at least the valves 20, 20′ are operated by the cam unit 13. In a position facing the actuator 15, the interruption causes a forced decoupling of the actuator 15. The actuator 15 is therefore temporarily disengaged from the engagement element 16 during operation. The switching element 29 of the actuator 15 is temporarily disengaged from the engagement element 16 during operation. The switching element 29 of the actuator 15 is always disengaged from the engagement element 16 if the cam unit 13 should not be adjusted.

(10) At each half camshaft revolution—whenever a switchover is mechanically possible the engagement element 16 enables an interaction between the actuator 15 and the cam unit 13. Whenever an attempt to switch over could lead to damage, no traction between the actuator 15 and the cam unit 13 is possible. This can prevent an incorrectly timed adjustment of the cam unit 13.

(11) To actuate the actuator 15, the valve operating device 10 has a control and regulating unit which is not depicted in detail. The control unit is intended to control the electric motor 27 of the actuator 15 and thereby actuate the actuator 15. The control and regulating unit is designed as part of a motor control. In principle, it is also conceivable that the control and regulating unit is designed as a separate control unit. By controlling the control and regulating unit, the electric motor 27 of the actuator 15 can be driven in both directions, allowing the switching element 29 to be moved in both axial directions.

LIST OF REFERENCE CHARACTERS

(12) 10 valve operating device 11 internal combustion engine 12 camshaft 13 cam unit 14 actuator unit 15 actuator 16 engagement element 17 motor vehicle 18 drive wheel 19 multi-stage transmission 20 valve 21 rotation axis 22 toothing 23 cam 24 cam track 25 cam track 26 cam track 27 electric motor 28 spindle 29 switching element