Variable valve train of a combustion engine

Abstract

A variable valve train (1) of a combustion engine for applying a load on two equally acting gas exchange valves (2, 3) for each cylinder of the combustion engine is provided, including a switchable valve train element (4, 5) with an outer part and an inner part ((6, 7), (8, 9)) that can move relative to each other allocated to each of the two gas exchange valves (2, 3). The outer and inner parts ((6, 7), (8, 9)) are selectively connectable to each other by an associated coupling slide mechanism (10, 11). The valve train (1) further includes a control shaft (12), on which a control cam (13, 14) is applied for each coupling slide mechanism (10, 11), and the control cams contact an outer end face (15, 16) of the respective coupling slide mechanisms (10, 11) for displacement thereof in one direction, and the two control cams (13, 14) can rotate separately from each other on the common control shaft (12).

Claims

1. A variable valve train of an internal combustion engine for applying a load on two equally acting gas exchange valves for each cylinder of the internal combustion engine, the variable valve train comprising: two switchable valve train elements, each having an outer part and inner part that can move relative to each other, one of the switchable valve train elements respectively allocated at least indirectly to each one of the two gas exchange valves; two coupling slide mechanisms, one associated with each of the switchable valve train elements, that selectively connect the outer part and the inner part to each other so that when the outer part and the inner part are coupled together, a large travel is provided, and when the outer part and the inner part are decoupled a relatively smaller or zero travel of the gas exchange valve is realized; a common control shaft including first and second shaft parts and having two control cams, one for each said coupling slide mechanism, each said control cam at least indirectly contacts a respective outer end face of the coupling slide mechanism associated therewith for displacement in one direction, and said control cams are rotatable separately from each other on the common control shaft; and a first servo mechanism and a second servo mechanism each formed as rotary actuators or pivoting actuators, the first and second servo mechanisms each apply a load to each of the shaft parts, the first and second servo mechanisms are electrically or hydraulically actuatable, the first servo mechanism contacts an end face of the respective shaft part, and the second servo mechanism contacts a middle area of the respective shaft part, the middle area being defined between the two control cams.

2. The valve train according to claim 1, wherein the two shaft parts are built concentrically one inside the other and each is rotatable by a respective one of the first and second servo mechanisms, and each of the shaft parts is in a rotationally locked connection with a respective one of the control cams.

3. The valve train according to claim 2, wherein the two control cams both sit on the outer shaft part, one of the control cams is directly locked in rotation with the outer shaft part and the other of the control cams is fixed in an axial direction and rotatable on the outer shaft part, said other control cam is locked in rotation with a radial finger protruding from the inner shaft part and extending through a slot in the outer shaft part.

4. The valve train according to claim 1, wherein the switchable valve train elements comprise finger levers, and for each of the finger levers, the outer part forms a main finger lever arm and has, on a bottom side thereof, an at least indirect valve contact on one end and a pivot bearing for a support element on an other end, the inner part forms a secondary finger lever arm having a pawl-shaped profile having one end connected in an articulated manner to the outer part, and the coupling slide mechanism includes a coupling pin in the outer part located on the other end, with said pin protruding from the outer part with the outer end face thereof.

5. The valve train according to claim 1, wherein each said coupling slide mechanism contacts the associated control cam in an elastically pretensioned manner.

6. The valve train according to claim 5, further comprising a pressure cap preassembled on each said coupling slide mechanism to provide the pretensioning for each said coupling slide mechanism, the pressure cap is loaded by a compression spring away from the coupling slide mechanism and directly contacts the control cam.

7. The valve train according to claim 1, further comprising an elastic pretensioning element for each said coupling slide mechanism that biases the respective coupling slide member against the associated control cam.

8. The valve train according to claim 7, wherein the elastic pretensioning element includes a pressure cap loaded by a compression spring away from the coupling slide mechanism that directly contacts the control cam.

9. A variable valve train of an internal combustion engine for applying a load on two gas exchange valves for each cylinder of the internal combustion engine, the variable valve train comprising: first and second switchable valve train elements, each of the switchable valve train elements including: an outer part; inner part that can move relative to the outer part; a coupling slide mechanism that selectively connects the outer part and the inner part so that when the outer part and the inner part are coupled together, a large travel is provided, and when the outer part and the inner part are decoupled a relatively smaller or zero travel of the gas exchange valve is realized; a common control shaft including first and second shaft parts and having two control cams, one for each said coupling slide mechanism, each said control cam acts on a respective outer end face of the coupling slide mechanism associated therewith for displacement in one direction, and said control cams are rotatable separately from each other on the common control shaft, a first servo mechanism and a second servo mechanism each formed as rotary actuators or pivoting actuators, the first and second servo mechanisms each apply a load to each of the shaft parts, the first and second servo mechanisms are electrically or hydraulically actuatable, the first servo mechanism contacts an end face of the respective shaft part, and the second servo mechanism contacts a middle area of the respective shaft part, the middle area being defined between the two control cams.

10. The valve train according to claim 9, wherein the first and second shaft parts that are built concentrically one inside the other.

11. The valve train according to claim 9, wherein the first and second control cams are located on the outer shaft part, the first control cam is locked in rotation with the outer shaft part, and the second control cam is axially fixed and rotatable on the outer shaft part and locked in rotation with a radial finger protruding from the inner shaft part that extends through a slot in the outer shaft part.

12. The valve train according to claim 9, wherein the switchable valve train elements comprise finger levers, and for each of the finger levers, the outer part forms a main finger lever arm and has, on a bottom side thereof, an at least indirect valve contact on one end and a pivot bearing for a support element on an other end, the inner part forms a secondary finger lever arm having a pawl-shaped profile having one end connected in an articulated manner to the outer part, and the coupling slide mechanism includes a coupling pin in the outer part located on the other end, with said pin protruding from the outer part with the outer end face thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows a schematic view of a variable finger lever drive;

(3) FIG. 2 shows a cross section through the control shaft in longitudinal section of the cam connected to the outer shaft section, and

(4) FIG. 3 shows a cross section through the control shaft in longitudinal section of the cam connected to the inner shaft section.

DETAILED DESCRIPTION

(5) From FIG. 1, a lift-variable valve train 1 of a combustion engine for loading two equally acting gas exchange valves 2, 3 of a cylinder of the combustion engine can be seen.

(6) A switchable valve train element 4, 5 that is here provided as a finger lever that can be disconnected is allocated to each gas exchange valve 2, 3. Each valve train element 4, 5 has an elongated outer part 6, 8 as the main finger lever arm. A pawl-like inner part 7, 9 that can be disconnected relative to the outer part is held in a space of the outer part as a secondary finger lever arm that has a pivot center on the side of one end 22.

(7) Each outer part 6, 8 acts with a lifting function on a bottom side 21 on the end 22 by a valve contact 23, 34 on its gas exchange valve 2, 3. On the other end 29, each outer part 6, 8 has a spherical cap-shaped pivot bearing 24, 35. By this bearing it is supported on a support element 32, 33 that is a mechanical or hydraulic part.

(8) Above each pivot bearing 24, 35, the respective outer part 6, 8 has a coupling slide mechanism 10, 11 that is provided as a pin and can be moved longitudinally in the finger lever arm direction. As can be seen, the latter protrudes from the outer part 6, 8 with its outer end face 15, 16. The two coupling slide mechanisms 10, 11 are shown in their retracted position, i.e., disengaged from an engagement surface 35, 36 on the free pivot end of the inner part 7, 9. In this way, the cam lift is deactivated and both gas exchange valves remain closed, as can be provided according to the use of the valve train 1 if residual gas recirculation is not desired or if the cylinder is deactivated.

(9) In addition, the valve train 1 includes a control shaft 12 that runs parallel to a camshaft 30, with a cam lift 31 extending from this camshaft 30, for example, in contact with the here rear valve train element 5, more exactly stated, its inner part 9. The control shaft 12 is formed of two shaft parts 17, 18 that are built concentrically one inside the other and can each rotate individually by a separate servo mechanism M1, M2. An electric rotary actuator can be provided as each servo mechanism M1, M2.

(10) FIG. 1 shows that a control cam 13 sits rigidly on the outer shaft part 17 (see also FIG. 2). This is in contact with the outer end face 15 of the coupling slide mechanism 10 of the first valve train element 4 shown in the foreground.

(11) A control cam 14 that contacts the outer end face 16 of the coupling slide mechanism 11 of the here rear valve train element 5 is connected to the inner shaft part 18. The exact type of connection of this control cam 14 can be seen in FIG. 3. Accordingly, the control cam 14 is likewise on the outer shaft part 17 but can rotate relative to this part. It is actuated by a radial finger 20 protruding from the inner shaft part 18 and extending through a segment-like slot 19 of the outer shaft part 17.

(12) From FIG. 1 it can also be seen that the two coupling slide mechanisms 10, 11 contact their control cams 13, 14 in an elastically pretensioned way. For realizing the pretensioning for the respective coupling slide mechanism 10, 11, on the outer end face, a pressure cap 25, 26 is applied that is loaded by a spiral compression spring as compression spring mechanism 27, 28 away from the coupling slide mechanism 10, 11. The respective pressure cap 25, 26 directly contacts the respective control cam 13, 14. In this way, the respective coupling slide mechanism 10, 11 can be pretensioned by the control cam 13, 14 outside of a cam root circle contact.

(13) The two valve train elements 4, 5 can be switched independently of each other, so that a total of 3 or 4 total gas exchange cross sections can be produced for each cylinder of the combustion engine. For example, by a segment-by-segment rotation of just the control shaft 17 using the electrical rotary actuator M1, only the coupling slide mechanism 10 can be moved mechanically, so that, stated briefly, the inner part 7 of the front valve train element 4 is coupled and this performs a lift on the gas exchange valve 2 when the gas exchange valve 3 is deactivated.

(14) Four total gas exchange cross sections are then produced if the inner parts 7, 8 of the valve train elements 4, 5 configured here as finger levers that can be disconnected are loaded by cams with different cam lift profiles with respect to each other, which then makes a specially prepared camshaft necessary.

(15) It is also conceivable and provided to construct one of the valve train elements 4, 5 as an element that can be disconnected (only one cam per valve train element) and the other as a switchable element (two cams for each valve train element (large cam lift, small cam lift)) or to construct both as switchable elements. Altogether, what is important is the ability to individually actuate the valve train elements 4, 5 of a cylinder of the combustion engine.

LIST OF REFERENCE NUMBERS AND SYMBOLS

(16) 1) Valve train

(17) 2) Gas exchange valve

(18) 3) Gas exchange valve

(19) 4) Valve train element

(20) 5) Valve train element

(21) 6) Outer part

(22) 7) Inner part

(23) 8) Outer part

(24) 9) Inner part

(25) 10) Coupling slide mechanism

(26) 11) Coupling slide mechanism

(27) 12) Control shaft

(28) 13) Control cam

(29) 14) Control cam

(30) 15) Outer end face

(31) 16) Outer end face

(32) 17) Shaft part

(33) 18) Shaft part

(34) 19) Slot

(35) 20) Radial finger

(36) 21) Bottom side

(37) 22) One end

(38) 23) Valve contact

(39) 24) Pivot bearing

(40) 25) Pressure cap

(41) 26) Pressure cap

(42) 27) Compression spring mechanism

(43) 28) Compression spring mechanism

(44) 29) Other end

(45) 30) Camshaft

(46) 31) Cam lobe

(47) 32) Support element

(48) 33) Support element

(49) 34) Valve contact

(50) 35) Engagement surface

(51) 36) Engagement surface

(52) M1) Servo mechanism

(53) M2) Servo mechanism