VALVE TRAIN FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A valve train may include a camshaft having first and second slide guides, first and second cams mounted axially adjacent in torque-proof manners on the camshaft, and a cam follower adjustable between a first position, in which the cam follower is drivingly connected with the first cam, and a second position, in which the cam follower is drivingly connected with the second cam. The valve train may also include an adjustment arrangement having adjustable mechanical first and second engagement elements for axially adjusting the cam follower between first and second positions. Each engagement element may be adjustable between basic positions, in which no contact exists with a respective one of the slide guides, and switching positions, in which the respective engagement element cooperates with the slide guide. Each engagement element may have a spring that prestresses it into the switching position. The valve train may further include an arresting device and an actuator for each engagement element, wherein the arresting device, when in a locked position, holds the associated engagement element in the basic position, and the actuator releases the arresting device

Claims

1. A valve train for an internal combustion engine, comprising: a camshaft having a first slide guide and a second slide guide thereon; a first cam mounted in a torque-proof manner on the camshaft, and a second cam arranged in a torque-proof manner on the camshaft axially adjacent to the first cam; a cam follower adjustable between a first position, in which the cam follower is drivingly connected with the first cam, and a second position, in which the cam follower is drivingly connected with the second cam; and an adjustment arrangement for an axial adjustment of the cam follower between a first position and a second position, the adjustment mechanism having: an adjustable mechanical first engagement element for axially adjusting the cam follower from the first position into the second position, the first engagement element cooperating with at least the first slide guide, the first engagement element being adjustable between a basic position, in which no contact exists with the first slide guide, and a switching position, in which the first engagement element cooperates with the first slide guide, the first engagement element having a spring that prestresses the first engagement element into the switching position; and an adjustable mechanical second engagement element for axially adjusting the cam follower from the second position into the first position, the second engagement element cooperating with at least the second slide guide, the second engagement element being adjustable between a basic position, in which no contact exists with the second slide guide, and a switching position, in which the second engagement element cooperates with the second slide guide, the second engagement element having a spring that prestresses the second engagement element into the switching position; an arresting device and an actuator for each engagement element, wherein the arresting device, when in a locked position, holds the associated engagement element in the basic position, and the actuator releases the arresting device.

2. The valve train according to claim 1, wherein the arresting device has a locking element, which in the locked position cooperates with a locking contour on the associated engagement element.

3. The valve train according to claim 2, wherein the arresting device is prestressed into the locked position by a spring.

4. The valve train according to claim 1, wherein the actuator is configured as one of an electric actuator, a hydraulic actuator, and a pneumatic actuator.

5. The valve train according to claim 1, wherein each engagement element has a wedge-shaped ramp laterally provided thereon for prestressing the associated arresting device.

6. The valve train according to claim 1, wherein the cam follower has a roller pin and a roller mounted rotatably thereon.

7. The valve train according to claim 6, wherein the arresting device is arranged in the roller pin.

8. The valve train according to claim 1, wherein at least one of: the first slide guide has a ramp structure, configured such that the first engagement element is brought out of engagement with the first slide guide and into the basic position; and the second slide guide has a ramp structure, configured such that the second engagement element is brought out of engagement with the second slide guide and into the basic position.

9. The valve train according to claim 1, further comprising an adjustment arrangement for returning the respective engagement element.

10. An internal combustion engine comprising a valve train having: a camshaft having a first slide guide and a second slide guide thereon; a first cam mounted in a torque-proof manner on the camshaft, and a second cam arranged in a torque-proof manner on the camshaft axially adjacent to the first cam; a cam follower adjustable between a first position, in which the cam follower is drivingly connected with the first cam, and a second position, in which the cam follower is drivingly connected with the second cam; and an adjustment arrangement for an axial adjustment of the cam follower between a first position and a second position, the adjustment mechanism having: an adjustable mechanical first engagement element for axially adjusting the cam follower from the first position into the second position, the first engagement element cooperating with at least the first slide guide, the first engagement element being adjustable between a basic position, in which no contact exists with the first slide guide, and a switching position, in which the first engagement element cooperates with the first slide guide, the first engagement element having a spring that prestresses the first engagement element into the switching position; and an adjustable mechanical second engagement element for axially adjusting the cam follower from the second position into the first position, the second engagement element cooperating with at least the second slide guide, the second engagement element being adjustable between a basic position, in which no contact exists with the second slide guide, and a switching position, in which the second engagement element cooperates with the second slide guide, the second engagement element having a spring that prestresses the second engagement element into the switching position; an arresting device and an actuator for each engagement element, wherein the arresting device, when in a locked position, holds the associated engagement element in the basic position, and the actuator releases the arresting device.

11. The valve train according to claim 2, wherein the locking element is one of a locking catch and a locking pin.

12. The valve train according to claim 2, wherein the locking contour is a groove.

13. The valve train according to claim 3, wherein the actuator is configured as an electromagnet.

14. The valve train according to claim 9, wherein the adjustment arrangement is one of hydraulic, pneumatic, electromagnet, mechanical, and electric.

15. The valve train according to claim 2, wherein the actuator is configured as one of an electric actuator, a hydraulic actuator, and a pneumatic actuator.

16. The valve train according to claim 2, wherein each engagement element includes a wedge-shaped ramp provided laterally thereon for prestressing the associated arresting device.

17. The valve train according to claim 2, wherein the cam follower has a roller pin and a roller mounted rotatably thereon.

18. The valve train according to claim 17, wherein the arresting device is arranged in the roller pin.

19. The valve train according to claim 1, wherein at least one of: the first slide guide has a ramp structure configured such that the first engagement element is brought out of engagement with the first slide guide and into the basic position; and the second slide guide has a ramp structure configured such that the second engagement element is brought out of engagement with the second slide guide and into the basic position.

20. A valve train for an internal combustion engine, comprising: a camshaft having a first slide guide and a second slide guide thereon; a first cam mounted in a torque-proof manner on the camshaft, and a second cam arranged in a torque-proof manner on the camshaft axially adjacent to the first cam; a cam follower adjustable between a first position, in which the cam follower is drivingly connected with the first cam, and a second position, in which the cam follower is drivingly connected with the second cam; and an adjustment arrangement for an axial adjustment of the cam follower between a first position and a second position, the adjustment mechanism having: an adjustable mechanical first engagement element for axially adjusting the cam follower from the first position into the second position, the first engagement element cooperating with at least the first slide guide, the first engagement element being adjustable between a basic position, in which no contact exists with the first slide guide, and a switching position, in which the first engagement element cooperates with the first slide guide, the first engagement element having a spring that prestresses the first engagement element into the switching position; and an adjustable mechanical second engagement element for axially adjusting the cam follower from the second position into the first position, the second engagement element cooperating with at least the second slide guide, the second engagement element being adjustable between a basic position, in which no contact exists with the second slide guide, and a switching position, in which the second engagement element cooperates with the second slide guide, the second engagement element having a spring that prestresses the second engagement element into the switching position; wherein for each engagement element, an arresting device, an actuator, and a spring, the arresting device having one of a locking catch and a locking pin, the spring prestressing the arresting device in a locked position in which the one of the locking catch and the locking pin cooperate with a locking contour on the associated engagement element to hold the associated engagement element in the basic position, the actuator releasing the arresting device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] There are shown, respectively diagrammatically,

[0020] FIG. 1 a valve train according to the invention for an internal combustion engine in an oblique view,

[0021] FIG. 2 an illustration as in FIG. 1, but with a different adjustment arrangement and in a front view,

[0022] FIGS. 3, 4 a highly diagrammatic illustration of an adjustment arrangement of different embodiments.

DETAILED DESCRIPTION

[0023] According to FIGS. 1 and 2, a valve train 1 according to the invention for an otherwise only indicated internal combustion engine 2 has a camshaft 3 and a cam follower 4. A first cam 5a and a second cam 5b, axially adjacent thereto, are arranged here on the camshaft 3 in a torque-proof manner, which cams have different cam profiles. For example, one of the two cams 5a, 5b can have only a base circle and therefore no cam lobe, so that via this a cylinder disconnection is possible. In order to be able to change between the cam profiles of the two cams 5a, 5b, the cam follower 4 is axially adjustable, i.e. in relation to the axial direction 6 of the camshaft 3 and namely between a first position, in which it is drivingly or respectively operatively connected with the cam 5a (cf. FIG. 1) and a second position, in which it is drivingly or respectively operatively connected with the second cam 5b (cf. FIG. 2). An adjustment arrangement 7 is likewise provided for the axial adjustment of the cam follower 4 between the first and the second position, which adjustment arrangement has an adjustable first mechanical engagement element 8a, which for the axial adjusting of the cam follower 4 from the first into the second position cooperates with at least a first slide guide 9a present on the camshaft 3 or engages therein. Furthermore, the adjustment arrangement 7 has an adjustable second mechanical engagement element 8b, which for the axial adjusting of the cam follower 4 from the second back into the first position cooperates with at least a second slide guide 9b present at the camshaft 3. The first and the second engagement element 8a, 8b are adjustable here respectively between a basic position (cf. the position of the engagement element 8a in FIGS. 1-4), in which there is no contact with the associated slide guide 9a, 9b, and a switching position (cf. the position of the second engagement element 8b in FIGS. 2 to 4), in which the respective engagement element 8a, 8b cooperates with the associated slide guide 9a, 9b. The respective engagement element 8a, 8b can be in one piece here, as is illustrated in FIGS. 1, 2 and in the respective engagement element 8b of FIGS. 3 and 4, or else in several parts (cf. engagement elements 8b in FIGS. 3 and 4). Furthermore, the adjustment arrangement 7 has for each engagement element 8a, 8b a spring 10a, 10b, which it prestresses into its switching position. Likewise, an arresting device 11 is provided, which holds the associated engagement element 8a, 8b in its basic position with a locking element 12 situated in its locked position. This is the case for example according to FIGS. 2 and 3 with the first engagement element 8a. Furthermore, an associated actuator 13 is provided for releasing the arresting device 11, i.e. for unlocking the locking element 12 from its locked position (cf. the locking element 12 according to FIGS. 2 and 3, 4 with engagement element 8b).

[0024] The arresting device 11 can have here as locking element 12 for example a locking catch 14 (cf. FIGS. 3, 4) or a locking pin 15 (cf. FIG. 2). The arresting device 13 and in particular its respective locking element 12 are prestressed here by means of a spring 16 into their locked position, as can be clearly seen for example with the locking elements 12 with respect to the first engagement element 8a in FIGS. 2 and 3. Here, as spring 16 for example a helical spring 16a (cf. FIG. 2) or else a leg spring 16b (cf. FIGS. 3, 4) can be used. In the configuration of the locking element 12 as locking catch 14, the latter cooperates in the locked position with an associated locking contour 20 (cf. FIGS. 3, 4) on the engagement element 8a, 8b, wherein the locking contour 20 can be configured for example as a groove.

[0025] The actuator 13 is preferably configured as an electric actuator, in particular as an electromagnet, as a hydraulic actuator or as a pneumatic actuator, and serves only for releasing the arresting device 11, whereupon the latter draws the respectively associated locking element 12 out from its locked position, so that the associated engagement element 8a, 8b, owing to the respectively associated spring 10a, 10b, is abruptly adjusted into its switching position. In addition to the extremely quick switching time, the valve train 1 according to the invention, and in particular also the adjustment arrangement 7 according to the invention, offers the great advantage that it is configured in a structurally extremely simple manner, is accommodated in a space-saving manner and, in addition, is able to be produced at a favourable cost.

[0026] Observing FIG. 2 further, it can be seen that on the first and second engagement element 8a, 8b respectively laterally a wedge-shaped ramp 17 is provided for prestressing the locking element 12. Through the wedge-shaped ramp 17, in particular a second actuator necessary for the drawing back of the respective locking element 12 can be dispensed with here, whereby the variety of parts can be reduced, and thereby also the costs for storage and logistics can be lowered.

[0027] A resetting of the respective engagement element 8a, 8b takes place here via a ramp structure, not designated in further detail, which is arranged in the respectively associated slide guide 9a, 9b and at the same time is configured in such a way that the first engagement element 8a is brought out of engagement with the first slide guide 9a and additionally is brought into its basic position. In the same way, the second slide guide 9b has a ramp structure, which is configured in such a way that the second engagement element 8b is transferred out of engagement with the second slide guide 9b and thereby into its basic position.

[0028] Alternatively thereto, the returning of the respective engagement element 8a, 8b can also take place via an adjustment arrangement 22 (cf. FIG. 4 for the engagement element 8a), which is operated for example hydraulically, pneumatically, electromagnetically, mechanically or electrically. In this case, the majority of parts of the adjustment arrangement 7 are therefore decoupled from the movement of the cam follower 4.

[0029] The cam follower 4 itself usually has a roller pin 18, on which a rotatably mounted roller 19 is arranged. Via this roller 19, the picking up takes place of the cam profile of the cam 5a, 5b which is respectively passed over. In a particularly preferred embodiment of the valve train 1 according to the invention, the arresting device 11, i.e. in particular the actuators 13 or respectively the locking elements 12, in particular the locking pins 15, is/are arranged in the roller pin 18, whereby an embodiment is possible which is particularly optimized with regard to installation space.

[0030] When the switching is triggered in a delayed manner owing to different influencing factors, or for cost reasons a slow/inaccurate actuator 13 is used (slow in relation to the time which is required in order to carry out a crankshaft revolution), it can occur that the engagement element 8a, 8b can no longer engage into the associated groove of the slide guide 9a, 9b, which brings it about that the engagement element 8a, 8b is pushed back into its arresting position, without having carried out the switching process. This can be counteracted by the active actuator 13 only then being deactivated (travels again in locking position), when the cam follower 4 has reached the new position. Thereby, it is ensured that a switching process takes place, even when the switching- and reaction times of the actuator 13 are reduced over its lifetime. This can then also take place only two or three camshaft revolutions later. Here, the moved-out engagement element 8a, 8b runs on the slide element until it can engage into the slide guide 9a, 9b. Therefore, slower or more favourable actuators 13 can also be used, because an arresting of the engagement element 13 only begins again after the switching process has been completely terminated.

[0031] Observing the embodiments of FIG. 3 further, it is noticeable that the spring 10a rests on a fixed component of the valve train 1, whereas the spring 10b rests on the roller pin 18. It is merely important here that the spring 10a, 10b prestresses the associated multi-part engagement element 8a or the associated single-part engagement element 8b into its switching position.

[0032] Here, the actuator 13 in the left-hand illustration of FIG. 3 is fixed, and the multi-part engagement element 8a has at its upper part such a large plate 21, which can cooperate with the lower part of the engagement element 8a irrespective of the axial position of the cam follower 4. Hereby, the number of moving parts can be distinctly reduced. In this case, therefore, the ramp structure in the slide guide 9a can bring about the resetting of the associated engagement element 8a. The actuator 13 (right-hand illustration in FIG. 3), actuating the engagement element 8b, can, but does not necessarily have to, adjust with the cam follower 4 in axial direction, as also the actuator 13 in FIG. 4, actuating the engagement element 8b, in so far as the locking catch 14 is long enough.

[0033] With the valve train 1 according to the invention, and the internal combustion engine 2 according to the invention, it is therefore possible to provide a simply constructed and, at the same time, quickly switching valve train 1, which at the same time is able to be produced at a favourable cost.