Valve drive

Abstract

A valve drive comprising a camshaft with base shaft, a lobe pack mounted on the base shaft and comprising three cam lobes. Two actuator bodies are associated with two actuator pins each connected to a valve of a cylinder of the engine. The lobe pack is axially displaceable along the base shaft so as to for each actuator body change cam lobe aligned therewith. A middle cam lobe has a shape leaving an actuator body aligned therewith uninfluenced thereby. In a first position of the lobe pack a first of the actuator bodies is aligned with and hit and moved by a first cam lobe and the other, second actuator body is aligned with the middle cam lobe, and in a second position the second actuator body is aligned with and hit and moved by a third cam lobe and the first actuator body is aligned with the middle cam lobe.

Claims

1. A valve drive for use in an internal combustion engine comprising: a camshaft comprising: a base shaft configured to rotate about a longitudinal axis; and a lobe pack mounted on said base shaft and comprising a first, a second, and a third respective cam lobe, where each cam lobe is differently shaped from each of said other cam lobes; and first and second actuator bodies each associated with respective actuator pins, where each actuator pin is connected to a respective valve of a cylinder of the internal combustion engine and said first and second actuator bodies are configured to be moved when contacted by one of said first and third cam lobes aligned therewith and, which contact thereby lifts the valve associated with said first or second actuator body from a closed position to an open position, wherein said second cam lobe of said lobe pack is located between said first and third cam lobes and has a shape that does not move said first or second actuator bodies when aligned therewith via rotation of said camshaft, and that said second cam lobe is in common to both first and second actuator bodies, and wherein said lobe pack is configured to be axially moveable along said base shaft between a first position, in which said first actuator body is aligned with and contacted by said first cam lobe via rotation of said camshaft and said second actuator body is aligned with said second cam lobe, and a second position, in which said second actuator body is aligned with and contacted by said third cam lobe via rotation of said camshaft and said first actuator body is aligned with said second cam lobe.

2. The valve drive according to claim 1, wherein said first actuator body and said first cam lobe are configured to co-operate to lift the valve associated with said first actuator body to the open position, where such open position is located at a different distance to the closed position of that the valve than a distance to the closed position of the open position to which said second actuator body and said third cam lobe are configured to lift the valve associated with said second actuator body.

3. The valve drive according to claim 2, wherein said first and third cam lobes are differently shaped and have respective surfaces configured to bear upon said respective first and second actuator bodies that have a different maximum distance to said longitudinal axis of said base shaft.

4. The valve drive according to claim 1, wherein said first actuator body is associated with two of said actuator pins so as to lift the respective valve associated with each of said two actuator pins when said first actuator body is aligned with said first cam lobe.

5. The valve drive according to claim 4, wherein said second actuator body lifts the valve associated with said actuator body when said second actuator body is aligned with said third cam lobe.

6. The valve drive according to claim 1, wherein the valves associated respectively with the first and second actuator bodies are exhaust valves and said first and second actuator bodies are configured to lift said exhaust valves.

7. The valve drive according to claim 6, wherein said second actuator body is in the second position of the lobe pack and is configured to be contacted and moved by said third cam lobe at a position close to an upper dead point of a piston in the cylinder in a compression stroke of that cylinder so as to act as a compression release brake.

8. The valve drive according to claim 7, wherein said second actuator body is associated with one of said actuator pins to lift the valve associated with said actuator pin when aligned with said third cam lobe, and wherein said second actuator body is, in the second position of the lobe pack, configured to be contacted and moved by said third cam lobe at a position close to the upper dead point of the piston of the cylinder also in an exhaust stroke of that cylinder so as to act as the compression release brake.

9. A valve drive according to claim 8, wherein said first actuator body and said first cam lobe are configured to co-operate to lift the valve associated with said first actuator body to the open position, where such open position is located at a different distance to the closed position of that the valve than a distance to the closed position of the open position to which said second actuator body and said third cam lobe are configured to lift the valve associated with said second actuator body, wherein said distance between the closed and open position is shorter for the valve associated with said second actuator body associated with the compression release brake than for the valve associated with said first actuator body.

10. A valve drive according to claim 9, wherein said second actuator body lifts the valve associated with said actuator body when aligned with said third cam lobe, and wherein said second actuator body is, in the second position of the lobe pack, configured to be contacted and moved by said third cam lobe at a position close to the upper dead point of the piston of the cylinder also in the exhaust stroke of that cylinder so as to act as the compression release brake.

11. The valve drive according to claim 7, wherein said first actuator body and said first cam lobe are configured to co-operate to lift the valve associated with said first actuator body to the open position, where such open position is located at a different distance to the closed position of that the valve than a distance to the closed position of the open position to which said second actuator body and said third cam lobe are configured to lift the valve associated with said second actuator body, wherein said distance between the closed and open position is shorter for the valve associated with said second actuator body associated with the compression release brake than for the valve associated with said first actuator body.

12. The valve drive according to claim 7, wherein said first actuator body is associated with two of said actuator pins so as to lift the respective valve associated with each of said two actuator pins when said first actuator body is aligned with said first cam lobe, and wherein, during normal combustion of the internal combustion engine, the lobe pack is in said first position so as to obtain lifting of the respective valve associated with said two actuator pins by said first actuator body.

13. The valve drive according to claim 7, wherein said second actuator body lifts the valve associated with said actuator pin when aligned with said third cam lobe, and wherein, to obtain braking of the engine by the compression release brake, said lobe pack is located in the second position so that said third cam lobe contacts said second actuator body and thereby lifts the valve associated with said second actuator body.

14. The valve drive according to claim 1, wherein the valves associated respectively with the first and second actuator bodies are inlet valves and said first and second actuator bodies are configured to lift said inlet valves.

15. The valve drive according to claim 1, wherein the second cam lobe has a width as seen in an axial direction of the camshaft allowing both first and second actuator bodies to be simultaneously aligned therewith, and that said lobe pack is positionable along the base shaft to a third middle position between said first and second positions in which both said first and second actuator bodies are aligned with said second cam lobe.

16. An internal combustion engine including a valve drive for use with the internal combustion engine, wherein said valve drive comprises: a camshaft comprising: a base shaft configured to rotate about a longitudinal axis; and a lobe pack mounted on said base shaft and comprising a first, a second, and a third respective cam lobe, where each cam lobe is differently shaped from each of said other cam lobes; and first and second actuator bodies each associated with respective actuator pins, where each actuator pin is connected to a respective valve of a cylinder of the internal combustion engine and said first and second actuator bodies are configured to be moved when contacted by one of said first and third cam lobes aligned therewith and, which contact thereby lifts the valve associated with said first or second actuator body from a closed position to an open position, wherein said second cam lobe of said lobe pack is located between said first and third cam lobes and has a shape that does not move said first or second actuator bodies when aligned therewith via rotation of said camshaft, and that said second cam lobe is in common to both first and second actuator bodies, and wherein said lobe pack is configured to be axially moveable along said base shaft between a first position, in which said first actuator body is aligned with and contacted by said first cam lobe via rotation of said camshaft and said second actuator body is aligned with said second cam lobe, and a second position, in which said second actuator body is aligned with and contacted by said third cam lobe via rotation of said camshaft and said first actuator body is aligned with said second cam lobe.

17. A motor vehicle including an internal combustion engine and a valve drive for use with the internal combustion engine, wherein said valve drive comprises: a camshaft comprising: a base shaft configured to rotate about a longitudinal axis; and a lobe pack mounted on said base shaft and comprising a first, a second, and a third respective cam lobe, where each cam lobe is differently shaped from each of said other cam lobes; and first and second actuator bodies each associated with respective actuator pins, where each actuator pin is connected to a respective valve of a cylinder of the internal combustion engine and said first and second actuator bodies are configured to be moved when contacted by one of said first and third cam lobes aligned therewith and, which contact thereby lifts the valve associated with said first or second actuator body from a closed position to an open position, wherein said second cam lobe of said lobe pack is located between said first and third cam lobes and has a shape that does not move said first or second actuator bodies when aligned therewith via rotation of said camshaft, and that said second cam lobe is in common to both first and second actuator bodies, and wherein said lobe pack is configured to be axially moveable along said base shaft between a first position, in which said first actuator body is aligned with and contacted by said first cam lobe via rotation of said camshaft and said second actuator body is aligned with said second cam lobe, and a second position, in which said second actuator body is aligned with and contacted by said third cam lobe via rotation of said camshaft and said first actuator body is aligned with said second cam lobe.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) With reference to the appended drawing, below follows a specific description of an embodiment of the invention cited as an example. In the drawing:

(2) FIGS. 1 and 2 are schematic views illustrating parts of an internal combustion engine provided with a valve drive according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) The construction and function of a valve drive according to an embodiment of the invention of an internal combustion engine 1 in a motor vehicle 2 will now be disclosed while referring to FIGS. 1 and 2. The engine has a camshaft 3 with a base shaft 4 configured to rotate about a longitudinal axis 5. A lobe pack 6 provided with three consecutive lobes 7-9 is mounted on the base shaft 4, and an arrangement 10 controllable to displace the lobe pack axially along the base shaft is indicated by a box 10 in FIG. 1 and may be of any conceivable type and controllable by the driver of the vehicle or by an electronic control unit of the vehicle based upon the value of certain parameters sensed.

(4) The valve drive further comprises two actuator bodies 11, 12 in the form of valve rocker levers associated with two actuator pins 13, 14 each connected to a valve 15, 16, which are here assumed to be exhaust valves of a cylinder 17 of the engine 1.

(5) The actuator body 11 is acting upon a valve bridge 18 pressing on both valve pins 13, 14, whereas the second actuator body 12 acts directly on the valve pin 14 through a through-hole 19 in the bridge 18. This is possible since the valve pin 14 is at the valve remote end divided in two parts.

(6) The lobe pack 6 is transferrable through said arrangement between two positions, namely a first position in which the first actuator body 11 is aligned with and hit and moved by a first 7 of the cam lobes by rotation of the camshaft (see FIG. 2), and a second position, in which the second actuator body 12 is aligned with and hit and moved by a third cam lobe 9 by rotation of the camshaft. The second, middle cam lobe 8 has a shape leaving an actuator body aligned therewith uninfluenced thereby by rotation of the camshaft, and this middle cam lobe is in common to both actuator bodies, so that the second actuator body 12 will be aligned therewith in said first position shown in FIG. 2 and the first actuator body 11 will be aligned therewith in the second position shown in FIG. 1.

(7) The function of the valve drive will be as follows. During normal drive of the internal combustion engine and by that of the motor vehicle for propulsion thereof the lobe pack 6 is kept in the first position shown in FIG. 2, which means that the first actuator body is aligned with the first cam lobe 7 for lifting both exhaust valves 15, 16 for letting exhaust gases out of the cylinder resulting in a most efficient propulsion of the vehicle. Lifting is as seen in the figures in fact a pressing or pushing of the valves 15, 16 down into the cylinder so as to allow exhaust gases to pass the valves.

(8) In the case using the compression release brake of the valve drive the arrangement 10 is controlled to displace the lobe pack 6 to the position shown in FIG. 1, i.e. said second position, in which the second actuator body 12 is aligned with the third cam lobe 9 and the first actuator body 11 is aligned with the middle cam lobe 8. This means that only the valve 16 will be influenced by rotation of the camshaft, and the cam lobe 9 will preferably be designed to co-operate with the actuator body 12 so that the valve 16 will be pressed down into the cylinder close to the upper dead point of a piston of the cylinder in the compression stroke of that cylinder, so that air compressed in the cylinder is released and no energy is returned to the crank shaft of the engine. Energy is instead absorbed and the torque to rotate the crank shaft will increase and the engine brake. It is also possible to design the second actuator body 12 and the third cam lobe 9 to co-operate so as to bring the exhaust valve 16 to open earlier, so that it may be open during the expansion stroke and by that let an over pressure from the exhaust side into the cylinder, so that this earlier opening of the exhaust valve will then result in an earlier closing of the valve during the exhaust stroke, which results in an additional compression stroke in the operation cycle of the piston and the braking of the engine increases.

(9) The second position shown in FIG. 1 may except for braking the vehicle be chosen for obtaining hotter exhaust gases for increasing the temperature and efficiency of a cold catalytic converter of the vehicle or assisting a vehicle cruise control to keep a constant speed of the vehicle when driving an undulating downhill road path.

(10) The invention is of course in no way restricted to the embodiment described above, since many possibilities to modifications thereof are likely to be obvious to one skilled in the art without having to deviate from the scope of invention defined in the appended claims.

(11) It is possible to control only one, some or all cylinders of an engine by a valve drive according to the invention.