Valve drive for an internal combustion engine

Abstract

A valve drive for a cylinder head of an internal combustion engine has a first camshaft which is rotatably mounted in a first and a second camshaft bearing and which includes at least one cam with a first cam curve and a second cam curve that differs from the first cam curve. A gas exchange valve is actuated by the first or the second cam curve. A camshaft section is provided, by which the cam can be moved by an actuator such that the gas exchange valve can be actuated either via the first or the second cam curve. The first camshaft and the cam have a fixed position relative to each other. The first camshaft can be axially moved in the first and the second camshaft bearing, and an axial lock is provided for the camshaft.

Claims

1. A valve drive for a cylinder head of an internal combustion engine, the valve drive comprising: a first camshaft mounted rotatably in first and second camshaft bearings, the first camshaft including: at least one cam with a first cam lobe and a second cam lobe different from the first cam lobe, the first cam lobe and the second cam lobe are configured to alternately actuate a gas exchange valve, and a camshaft section configured to axially displace the at least one cam via an actuator such that a selected one of the first cam lobe and the second cam lobe actuates the gas exchange valve; and an axial lock operatively coupled with the first camshaft, the axial lock comprises a slotted guide that runs around an outer circumference of the first camshaft, the slotted guide including a first slotted guide track and a second slotted guide track axially adjacent one another via an interposed cylindrical section, and an axial groove over the first and second slotted guide tracks and the cylindrical section, wherein the at least one cam is fixed on the first camshaft, and wherein the first camshaft is configured to be axially displaced in the first and the second camshaft bearing, and wherein a locking element is configured to alternately engage the first and the second slotted guide tracks.

2. The valve drive according to claim 1, wherein the locking element is prestressed toward the slotted guide via a spring.

3. The valve drive according to claim 2, wherein the first and the second slotted guide tracks each form an angle between 2° and 45° with respect to an axis of the first camshaft.

4. The valve drive according to claim 2, wherein the slotted guide is mounted on the first camshaft via an anti-friction bearing or a plain bearing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a plan view of a valve drive according to an embodiment of the invention.

(2) FIG. 2 is a plan view of the valve drive with a locking apparatus.

(3) FIG. 3 is a section through a locking element of the axial lock.

(4) FIG. 4 is a section through the axial lock.

(5) FIG. 5 is a section through the locking element in an operative connection with the axial lock.

(6) In the following text, the same designations apply to identical components in FIGS. 1 to 5.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 shows a plan view of a valve drive 1 for a cylinder head of an internal combustion engine. The cylinder head (without designation) is shown without a valve cover, in order that the valve drive 1 is visible. The valve drive 1 is arranged on the inlet side and is provided for two cylinders with four gas exchange valves of identical action which are shown in FIG. 2.

(8) The valve drive 1 has a first camshaft 4 which is mounted rotatably in a first and a second camshaft bearing 2, 3 and in further camshaft bearings that are not designated. A second camshaft without designation is provided on the outlet side. In the present exemplary embodiment, the first camshaft 4 has four cams 5 for four gas exchange valves (not shown) for two cylinders of the internal combustion engine, only one cam 5 being designated. The cam 5 has a first cam lobe 6 (curve) and a second cam lobe (curve) 7 which is different than the first cam lobe 6. During the operation of the internal combustion engine, the gas exchange valve can be actuated either by the first or by the second cam lobe 6, 7 via an intermediate element, such as a sliding rocker arm.

(9) Furthermore, a camshaft section 8 is provided, with radially outwardly circumferential control grooves, into which a pin (not visible) of an actuator 9 engages, with the result that the camshaft 4 can be displaced with the cam 5 in such a way that the gas exchange valve can be actuated either via the first or the second cam lobe 6, 7.

(10) The camshaft 4 and the cam 5 are preferably made from the same material and in one piece. In a further embodiment, the cam can also be shrink-fitted or joined onto the camshaft 4. A spur gear wheel 17 which can be driven by a further gearwheel without designation is provided for driving the camshaft 4.

(11) In order to reduce the load of the pin of the actuator 9 during the operation of the internal combustion engine, an axial lock 10 which is shown in the following figures is provided for the axially displaceable camshaft 4.

(12) FIG. 2 shows a plan view of the axial lock 10 for the first camshaft 4. In FIG. 2, the first camshaft 4 has two cams 5, only a single cam 5 once again being designated. The first cam lobe 6 and the second cam lobe 7 which is different than the first cam lobe 6 can be seen clearly in FIG. 2. Gas exchange valves 19 can also be seen in the illustration in FIG. 2, with in each case one valve spring 20, of which gas exchange valves 19 in each case only one is designated. A drive gearwheel, the spur gear wheel, for the camshaft 4 is in turn designated by 17. The axial lock 10 is a slotted guide 11 which is shown in FIG. 4, runs radially around the camshaft 4, and has a first and a second slotted guide track 12, 13 which are axially adjacent with respect to one another and into which a locking element 15 which is prestressed by way of a spring 14 engages. The locking element 15 which is prestressed by way of the spring 14 is arranged in a bracket 21. The axial lock 10 is mounted onto the first camshaft 4 by way of a screw connection 18.

(13) FIG. 3 shows a section through the bracket 21 with the locking element 15 which is prestressed by way of the spring 14. The bracket 21 has two fastening bores 23. The locking element 15 is a pin which is prestressed by way of the spring 14, it being possible for the prestress to be set by way of a cap nut 22.

(14) FIG. 4 shows a section through the axial lock 10 without the prestressed locking element 15. The slotted guide 11 with the first and the second slotted guide track 12, 13 which are axially adjacent with respect to one another is mounted radially on the camshaft 4 in the present exemplary embodiment via an anti-friction bearing 25, a ball bearing in the present exemplary embodiment. It can also be a plain bearing in another exemplary embodiment. A camshaft axis is denoted by 16. An angle between the second slotted guide track 13 and the camshaft axis 16 is denoted by a. Furthermore, in the present exemplary embodiment, the first and the second slotted guide track 12, 13 are spaced apart axially from one another by way of a cylindrical section 24. The first and the second slotted guide track 12, 13 preferably form an angle of between 2° and 45° with the camshaft axis 16.

(15) FIG. 5 shows a section through the locking element 15 and the slotted guide 11. The prestress by way of the spring 14 is shown by way of an arrow onto the locking element 15 in the direction of the slotted guide 11. A displacement travel of the locking element 15 over the slotted guide 11 is denoted by 26. The displacement travel 26 corresponds to the width of a cam lobe 6, 7. An angle between the slotted guide tracks 12, 13 is denoted by β.

(16) In a further particularly preferred exemplary embodiment, the slotted guide 11 has an axial groove over the slotted guide tracks 12, 13 and the cylindrical section 24, in which axial groove the locking element 15 can be displaced axially.

(17) A relative movement which is produced of the first camshaft 4 with respect to the pin of the actuating element 9 can be minimized by way of the use of the axial lock 10 according to the invention. This makes a single-piece sliding camshaft possible.

LIST OF DESIGNATIONS

(18) 1 Valve drive 2 First camshaft bearing 3 Second camshaft bearing 4 First camshaft 5 Cam 6 First cam lobe (curve) 7 Second cam lobe (curve) 8 Camshaft section 9 Actuator 10 Axial lock 11 Slotted guide 12 First slotted guide track 13 Second slotted guide track 14 Spring 15 Locking element 16 Camshaft axis 17 Spur gearwheel 18 Screw connection 19 Gas exchange valve 20 Valve spring 21 Bracket 22 Cap nut 23 Fastening bore 24 Cylindrical section 25 Anti-friction bearing 26 Displacement travel α Angle between the camshaft axis and the slotted guide track β Angle between the slotted guide tracks

(19) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.