DE202015003059U1 - Valve gear for the switchable operation of an internal combustion engine in two- or four-stroke - Google Patents

Abstract

A valve train for an internal combustion engine, having a camshaft rotating at half the crankshaft speed and having a cam (6), the cam (6) having a base circle phase and a projection phase, and a gas exchange valve (4) having a valve stem (15), characterized in that Cam contour of two on the same valve (4) acting cam followers, more precisely a tilt (7) and a drag lever (5), is tapped, wherein the sampling points (12, 13) of the two cam followers (5, 7) by half a revolution of Camshaft are staggered so that during a complete revolution of the camshaft both cam followers (5, 7) each undergo a deflection, the cam lift is translated via one of the cam follower (5 or 7) permanently in a valve lift, whereas the other cam follower (5 or 7) by the support of the bearing forces of one of its three bearing points (sampling point (12, 13), lever axis (8, 10), action point (11, 16)) on a Schaltele ment (9, 17), which receives the corresponding bearing forces in the locked state, but does not absorb the corresponding bearing forces in the unlocked state and permits a lost movement, so that in the locked state, a valve lift and in the unlocked state, the lost movement instead of a valve, switchable is executed, which is implemented by the permanently active cam follower (5 or 7) a valve lift per two crankshaft revolutions, as is required for the four-stroke operation of the internal combustion engine, and by switching the second cam follower (5 or 7) via the locking of the switching element ( 9, 17), a further valve opening is achieved, so that a valve lift per crankshaft revolution is achieved, which allows the charge cycle for two-stroke operation.

Description

Conventional internal combustion engines can be operated according to the prior art usually only stationary either in two- or four-stroke. Both working cycles offer certain advantages as well as disadvantages. Thus, due to the double explosion frequency of the two-stroke engine at the same crankshaft speed more, if not twice, generated power. However, due to flushing losses, more unburned fuel components are contained in the exhaust gas than in engines operated in four-stroke mode, which causes problems, inter alia, when using catalytic converters. The question of whether a two-stroke or a four-stroke engine is the right alternative for use in z. As the automotive industry would be, especially in the field of mopeds not conclusively clarified. Both types of engine can be operated with a variety of fuels, such as gasoline, diesel, alcohol or gaseous fuels. The fuel can be brought into the combustion chamber of the engine via a variety of technical solutions, including carburetor, injection into the intake tract or direct injection. The ignition of the air-fuel mixture can be foreign by, for example, a spark or even by the compression.

There are known some inventions, which try to combine the advantages of a two-stroke engine with those of a four-stroke engine, in order to achieve the best mix of fuel consumption, pollutant emissions, power output, noise emissions, vibrations, space, mass, etc. This is usually resorted to a valve train for controlling the charge exchange, which provides the required variability for switching between two- and four-stroke. This can be achieved either by fully variable systems with, for example, electromechanical or hydraulic valve drive, but also mechanical solutions are known. In addition, the ignition and the fuel supply must be adjusted.

For example, solutions are known in which a camshaft is used as lifting element. Here, for example, on a camshaft, which rotates at half crankshaft speed, a 180 ° offset cam pair can be attached. Both of these cams are tapped by a separate cam follower. The two cam followers can be mechanically interlocked, whereby, depending on whether locked or not, an opening of the corresponding valve is achieved each crankshaft revolution (two-stroke) or every other crankshaft revolution (four-stroke). (See this GB 2470025 A )

The invention relates to a valve train, which can be applied for example to an internal combustion engine, each with an inlet and outlet valve per cylinder. The valve train according to the invention allows the optional operation of an internal combustion engine in two- or four-stroke. The lifting element used is a camshaft rotating at half the crankshaft speed. On this there is a cam per valve ( 6 ), which has a base circle phase and a survey phase. This cam ( 6 ) is, by two acting on the same valve cam follower, a drag lever ( 5 ) and a rocker arm ( 7 ), tapped. The sampling points ( 12 . 13 ) of the two cam followers are arranged offset by 180 °. As a result, each camshaft revolution is tapped twice, or each crankshaft revolution once, the cam lift from one of the cam followers. Between the ends of the levers opposite their sampling points, henceforth action points ( 11 . 16 ) called, there is a mechanical connection. According to the invention, each deflection of one of the two cam followers is converted by the passing cam into a valve stroke, whereas the corresponding remaining second cam follower is moved at one of its bearing points (sampling point (FIG. 12 . 13 ), Lever axis ( 8th . 10 ) or action point ( 11 . 16 )) on a corresponding switching element ( 9 . 17 ) is stored. This switching element ( 9 . 17 ) allows, either in the locked state, the tapped cam lift to the valve ( 4 ) or, in the unlocked state, to translate the cam lift into a "lost motion" so that no opening of the valve takes place. Switching elements of this type are well known in the art and are currently used, for example, in solutions of selective cylinder deactivation or in the Hubumschaltung of engine valves. For example, there are switchable valve cups ( 9 ) (cf et al DE 10 2006 034 624 A1 ) as used on the Porsche VarioCamPlus system or supporting elements ( 17 ) for the axles of rocker arms or towing levers, for example, for the shutdown of the drag lever for the cylinder deactivation used in Mercedes Benz engine M152. The switching elements which can be used according to the invention have in common that in the unlocked state they can receive the "lost path" by telescoping in the manner of a telescope and in the locked state this collapse is prevented so that they can support an axial force. The locking mechanism is usually actuated hydraulically, but other operating media are also conceivable.

According to the invention, the switching element ( 9 . 17 ) be installed in different places. These possible arrangements are in the to outlined. Thus, according to claims 1 and 2, the switching element ( 9 . 17 ) in the form of a switchable valve cup ( 9 ), as in outlined between the Action points ( 11 . 16 ) of tilting ( 7 ) and the rocker arm ( 5 ), so that the action of the rocker arm ( 7 ) on the valve ( 4 ) is switchable, with both cam followers directly on the valve stem ( 15 ) Act. Likewise, according to claims 1 and 3, as in outlined, between tipping ( 7 ) and drag lever ( 5 ) a push rod ( 14 ), on which the switchable valve cup ( 9 ), so that the action of the rocker arm ( 7 ) on the push rod ( 14 ), which are on the rocker arm ( 5 ), which in turn on the valve stem ( 15 ), becomes switchable. Further, according to claims 1, 4 and 5, the rocker shaft axis ( 8th ) (see. ) or alternatively the cam follower axis ( 10 ) (see. ) on a switching element ( 17 ) are supported.

In is an example of an inventive valve train according to claims 1, 3 and 6 with two overhead camshafts ( 6 ), in which the switching elements ( 9 ) the connection between the rocker arms ( 7 ) and drag levers ( 5 ) form.

LIST OF REFERENCE NUMBERS

1

cylinder head

2

intermediate plate

3

valve cover

4

Gas exchange valve

5

cam follower

6

Cam on camshaft

7

rocker arm

8th

rocker shaft

9

Switchable valve cup

10

Rocker arm shaft

11

Action point rocker arm

12

Sampling point rocker arm

13

Sampling point drag lever

14

pushrod

15

valve stem

16

Action point rocker arm

17

Switchable support element

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• GB 2470025 A [0003]
• DE 102006034624 A1 [0004]

Claims (6)

Valve train for an internal combustion engine, with a camshaft rotating at half the crankshaft speed with a cam ( 6 ), wherein the cam ( 6 ) has a base circle phase and an elevation phase, and a gas exchange valve ( 4 ) with a valve stem ( 15 ), characterized in that the cam contour of two on the same valve ( 4 ) acting cam followers, more precisely a tilting ( 7 ) and a drag lever ( 5 ), the sampling points ( 12 . 13 ) of the two cam followers ( 5 . 7 ) are offset by half a revolution of the camshaft, so that during one complete revolution of the camshaft both cam followers ( 5 . 7 ) experience a deflection, wherein the cam lift via one of the cam followers ( 5 or 7 ) is permanently translated into a valve lift, whereas the other cam follower ( 5 or 7 ) by the support of the bearing forces of one of its three bearing points (sampling point ( 12 . 13 ), Lever axis ( 8th . 10 ), Action point ( 11 . 16 )) on a switching element ( 9 . 17 ), which receives the corresponding bearing forces in the locked state, but does not absorb the corresponding bearing forces in the unlocked state and permits a lost movement, so that in the locked state, a valve lift and in the unlocked state, the lost movement instead of a valve lift, is switchable, which with the permanently active cam follower ( 5 or 7 ) a valve lift is implemented for each two crankshaft revolutions, as is necessary for the four-stroke operation of the internal combustion engine, and by switching on the second cam follower ( 5 or 7 ) via the locking of the switching element ( 9 . 17 ) a further valve opening is achieved so that a valve lift per crankshaft revolution is achieved, which allows the charge cycle for the two-stroke operation. Valve gear according to claim 1, characterized in that the drag lever ( 5 ) directly on the valve stem ( 4 ) and the rocker arm ( 7 ) on a switchable valve cup ( 9 ) on the valve stem ( 4 ), acts, so that the deflection of the finger lever ( 5 ) is permanently converted into a valve lift, whereas the deflection of the rocker arm ( 7 ) depending on the locking state of the switching cup ( 9 ) either in a lost movement of the switchable valve cup ( 9 ) relative to the valve stem ( 4 ) or in a valve lift can be implemented. Valve gear according to claim 1, characterized in that the drag lever ( 5 ) on the valve stem ( 4 ) and the rocker arm ( 7 ) on a switchable valve cup ( 9 ) as a switching element, which on a push rod ( 14 ) as an extension of the valve stem ( 4 ) sitting on the rocker arm ( 5 ) and thus indirectly on the valve stem ( 4 ), so that the deflection of the finger lever ( 5 ) is permanently converted into a valve lift, whereas the deflection of the rocker arm ( 7 ) depending on the locking state of the switching cup ( 9 ) either in a lost movement of the switchable valve cup ( 9 ) opposite the push rod ( 14 ) or in a valve lift can be implemented. Valve gear according to claim 1, characterized in that the rocker shaft ( 8th ) on a switchable support element ( 17 ) is mounted so that the deflection of the rocker arm ( 7 ) can be converted into either a lost motion or a valve lift. Valve gear according to claim 1, characterized in that the cam follower axis ( 10 ) on a switchable support element ( 17 ) is mounted so that the deflection of the finger lever can be converted either into a lost motion or a valve lift. Valve gear according to claim 1 and 3, characterized in that the push rod ( 14 ) a component of the switching cup ( 9 ).

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