DE102011014308A1 - Internal combustion engine with mixed camshaft - Google Patents

Abstract

The invention relates to an internal combustion engine, in particular a diesel engine, in particular a motor vehicle, with at least one working cylinder, with at least two intake valves (78) and at least one exhaust valve (80) being associated with each working cylinder, at least two camshafts (16, 18) being provided by which at least one mixed camshaft (18) actuates both at least one intake valve (78) and at least one exhaust valve (80), with at least one mixed camshaft (18) having both at least one intake valve (78) and at least one exhaust valve (80 ) actuated, an adjuster (28) is arranged, which adjusts the valve timing of the mixed camshaft (18) associated intake and exhaust valves (78, 80) with respect to the valve timing of the at least one other camshaft (16) either early or late. At least one cam carrier (54) is provided at least on the mixed camshaft (18), the cam carrier (54) being arranged on the mixed camshaft (18) in a rotationally fixed and axially displaceable manner relative to this mixed camshaft (18), the at least one Cam carrier (54) has at least one cam (24, 26) on which at least two different cam tracks (60, 62, 64, 66) are formed, wherein means (92, 96, 56, 58) for axially displacing the at least one cam carrier (54) are provided opposite the mixed camshaft (18) between a first axial position and at least a second axial position.

Description

The invention relates to an internal combustion engine, in particular a diesel engine, in particular a motor vehicle, with at least one working cylinder, wherein each cylinder at least two intake valves and at least one exhaust valve is assigned, wherein at least two camshafts are provided, of which at least one mixed camshaft both at least one inlet valve and actuated at least one exhaust valve, wherein at least one mixed camshaft which actuates both at least one inlet valve and at least one exhaust valve, a phaser is arranged which valve timing of the mixed camshaft associated intake and exhaust valves against the valve timing of the at least one other camshaft optional after Early or late adjusted, according to the preamble of claim 1.

From the DE 44 26 557 A1 It is known, working cylinders of an internal combustion engine functionally identical valves, so for example, two intake valves or two exhaust valves to arrange diagonally opposite, so that two camshafts each control a portion of the intake valves. In this way, two separate inlet systems are provided, which have different timing, but these timing are fixed.

In the familiar Miller / Atkinson cycle, the point in time "intake valve closes" (ES) is postponed. In this way, fresh gas already in the cylinder z. T. pushed out again. This means a filling disadvantage, which can be compensated but via a charge with a suitable boost pressure. In this case, the boost pressure in the volume between the loader outlet and the engine inlet is to be regulated in such a way that the boost pressure in each Miller operating point, ie. H. each operating point in which the "MillerCycle" is used, the theoretical compression end pressure in the working cylinders of the internal combustion engine at the time intake valve closes corresponds. For the control, optionally also control, come pressure and / or temperature and / or mass flow sensors or useful combination sensors of the three types of sensor used.

The positive effect of the Miller / Atkinson cycle on the NO _x emission and homogenization of the diesel mixture by means of an early or late point in time for closing the inlet valve is known. Furthermore, in the case of Otto engine applications, the tendency to knock when being supercharged can be significantly reduced. In contrast to the gasoline engine, which can work due to lack of geometric constraints with positive valve overlap, in the diesel engine, a simple implementation of the method using a phaser is generally not possible. The reason for this is a mechanical collision of the valve with the piston during early adjustment and increased pumping work with retardation.

From the pamphlets DE 42 30 877 and DE 199 08286 a valve train is known in which a cam carrier is arranged rotationally fixed and axially displaceable on a base camshaft. The cam carrier consists of a tubular material, on which at least one cam is arranged, in which emerge from a common base circle axially offset several different cam tracks. By the axial displacement of the cam piece on the base camshaft, a gas exchange valve can be actuated by the differently shaped cam tracks in different ways, with the cam tracks differ in the Hubkontur and / or in the phase position.

The object of the invention is to improve or optimize intake and exhaust timing for the thermodynamic optimization of engine operation in the map.

This object is achieved by an internal combustion engine o. G. Art solved with the features characterized in claim 1. Advantageous embodiments of the invention are described in the further claims.

For this it is in an internal combustion engine o. G. Art provided according to the invention that at least on the mixed camshaft at least one cam carrier is provided, wherein the cam carrier relative to this mixed camshaft rotatably and axially displaceably on the mixed camshaft is arranged, wherein the at least one cam carrier has at least one cam on which at least two different Cam tracks are formed, wherein means for axially displacing the at least one cam carrier relative to the mixed camshaft between a first axial position and at least one second axial position are provided.

This has the advantage that a cam switch with a reduced number of cam positions is available, since, for example, an actuator converts both an intake cam and an exhaust cam.

A high mechanical stability with over many cycles functionally reliable displacement of the cam carrier is achieved by the fact that the at least one cam carrier is included for supporting the at least one camshaft of at least one cylinder head fixed camshaft bearing.

A particularly well optimizable adaptation of valve timing to an operating state of the internal combustion engine is achieved in that the adjuster is designed such that it has an adjustment range for the valve timing of 60 ° CA +/- 20 °.

A particularly good and optimized gas exchange during operation of the internal combustion engine is achieved in that each cylinder two exhaust valves are assigned, wherein two camshafts are provided, wherein a first camshaft one half of the intake and exhaust valves and a second camshaft, the other half of the Ein - And exhaust valves actuated, the first camshaft having fixed timing for the camshaft associated valves and is arranged on the second camshaft of the adjuster.

A particularly large adjustment range even in diesel engines without collision between valves and reciprocating is achieved in that the second camshaft is designed such that at an adjustment angle of 0 ° KW the second camshaft associated exhaust valves close earlier than the first camshaft associated exhaust valves and the Open the intake valves associated with the second camshaft later and close later than the intake valves associated with the first camshaft.

A further improvement of the thermodynamic optimization of the operation of the internal combustion engine is achieved in that the second camshaft is designed such that close at an adjustment angle of 0 ° KW, the intake valves associated with the second camshaft at the same time with the intake valves associated with the first camshaft. In this case, only a late adjustment takes place.

A particularly simple and functionally reliable axial displacement of the cam carrier is achieved in that the means for axially displacing the at least one cam carrier relative to the mixed camshaft between a first axial position and at least a second axial position at least one axially fixed relative to the blended camshaft and radially between a first and a second pin position displaceable bolt which engages in the second pin position in a formed on the cam carrier, in the radial direction circumferential groove and spaced in the first pin position of this groove, wherein the groove is formed such that the cam carrier of an axial position on the mixed camshaft shifts to a different axial position on the mixed cam shaft when the bolt engages in the groove.

A particularly fast and repeatable axial displacement of the cam carrier is achieved by providing at least one first pin which selectively engages a first groove and at least one second pin spaced axially with respect to the mixed cam shaft from the first pin engages the second groove spaced axially from the first groove with respect to the blended camshaft, wherein the cam carrier moves from the first axial position on the blended camshaft to the second axial position on the blended camshaft as the first bolt engages and disengages the first cam groove second axial position on the blended camshaft moves to the first axial position on the blended camshaft when the second bolt engages the second groove.

The invention will be explained in more detail below with reference to the drawing. This shows in

1 a preferred embodiment of an internal combustion engine according to the invention in a schematic view,

2 a schematic representation of the camshaft assembly in the internal combustion engine according to the invention 1 .

3 a graphical representation of the valve movement of intake and exhaust valves of the various camshafts and the piston movement at an adjustment angle of 0 ° KW,

4 a graphical representation of the valve movement of intake and exhaust valves of the various camshafts and the piston movement with maximum displacement in the direction of early and

5 a graphical representation of the valve movement of intake and exhaust valves of the various camshafts and the piston movement at maximum displacement in late direction.

In the 1 illustrated, preferred embodiment of an inventive internal combustion engine comprises a cylinder head 10 , in which working cylinders not shown are arranged, in which each a reciprocating piston (not shown) moves in an oscillating manner. The cylinder head 10 has an outlet side 12 on which exhaust gases are discharged from the working cylinders, and an inlet side 14 on, at the working cylinders fresh gas is supplied.

Each working cylinder is associated with two intake valves (not shown) and two exhaust valves (not shown), wherein a first camshaft 16 and a second camshaft 18 are provided. The first camshaft 16 carries intake cams 20 . each actuating an intake valve and exhaust cams 22 , each actuate an exhaust valve. Likewise, the second camshaft carries 18 intake cams 24 each actuating an intake valve and exhaust cams 26 , each actuate an exhaust valve. On both camshafts 16 . 18 alternate in the longitudinal direction each intake cam 20 . 24 and exhaust cams 22 . 26 from. In this way, the two intake valves and exhaust valves of each working cylinder of different camshafts 16 . 18 actuated. As especially in addition 2 Thus, each of the camshafts is 12 . 14 a so-called mixed camshaft, ie each camshaft 12 . 14 operates both intake and exhaust valves via respective intake cams 20 . 24 or exhaust cams 22 . 26 ,

The timing of the first camshaft 16 for the associated intake and exhaust valves are fixed unchangeable. At the second camshaft 18 is an adversary 28 arranged, which the timing of the associated intake and exhaust valves with respect to the timing of the first camshaft 16 changed by the second camshaft 18 by the Versteller 28 relative to the first camshaft 16 is twisted. The first camshaft 16 is the camshaft that comes with 30 is driven by a crankshaft, not shown, of the internal combustion engine. The first camshaft 16 in turn drives over gears 32 the second camshaft 18 at.

In the 3 to 5 is on a horizontal axis 34 a crank angle and on a vertical axis 36 applied a lifting movement. On the horizontal axis 34 is at 38 a bottom dead center (UT) of the reciprocating piston before the charge cycle, at 40 a top dead center (TDC) of the reciprocating piston during the charge exchange and at 42 a bottom dead center (UT) of the reciprocating piston applied after the charge change. A first graph 44 illustrates the lifting movement 36 over the crank angle 34 for the piston, a second graph 46 illustrates the lifting movement 36 over the crank angle 34 for those exhaust valves coming from the exhaust cams 22 the first camshaft 16 be controlled, a third graph 48 (dashed) illustrates the lifting movement 36 over the crank angle 34 for those exhaust valves coming from the exhaust cams 26 the second camshaft 18 be controlled, a fourth graph 50 illustrates the lifting movement 36 over the crank angle 34 for those intake valves coming from the intake cams 20 the first camshaft 16 be controlled and a fifth graph 52 (dashed) illustrates the lifting movement 36 over the crank angle 34 for those intake valves coming from the intake cams 24 the second camshaft 18 to be controlled.

In 3 is a position of the Verstellers 28 shown at 0 ° CA, ie the camshafts 16 . 18 are not twisted against each other. In 4 is a position of the adjuster at maximum displacement towards late and in 5 is a position of the adjuster at maximum adjustment shown in the morning. Like from the 2 to 5 Immediately apparent, the lifting movement of the valves of the first crankshaft remains 16 (second graph 46 and fourth graph 50 ) relative to the crankshaft unchanged, whereas the lifting movement of the valves of the second crankshaft 18 (third graph 48 and fifth graph 52 each dashed) are moved together for the associated intake valves and exhaust valves. As a result, on the one hand by the shifted opening times between the intake valves of the first crankshaft 16 (Intake cam 20 ; fourth graph 50 ) and the intake valves of the second crankshaft 18 (Intake cam 24 ; fifth graph 52 ) a miller effect can be simulated ( 3 On the other hand, a collision between the intake valves and the reciprocating piston is prevented.

The prerequisite for this simulated Miller is the presence of at least two intake valves per cylinder and one, preferably two, exhaust valves per cylinder, the intake valves of each cylinder being actuated by different crankshafts. Here serves a camshaft 16 half of all intake and exhaust valves with conventional timing. Alternatively, the inlet side is optimized for maximum filling at a specific operating point, for example for the cold start operating point. The second camshaft 18 operates the remaining intake and exhaust valves and, with regard to the cam contour for "exhaust valve closes" and "intake valve opens", is designed so that an adjustment range of this camshaft 18 from about 60 ° CA +/- 20 ° can take place without piston collision.

The Millereffekt is achieved by the earliest "intake valve opens" of a camshaft 16 and the latest "intake valve closes" the other camshaft 18 assigned to different valves for each cylinder, see. 4 ,

An increase of the compression end temperature is possible by the fact that at "intake valve closes" the fixed camshaft 16 (fourth graph 50 ) in the UT 42 the second camshaft 18 (Miller wave) is also moved towards early (fifth graph 52 ; see. 5 ). At the same time, an increase in exhaust gas temperature (important for exhaust aftertreatment) can be achieved by prematurely pushing the "exhaust valve opens" of the Miller shaft 18 (third graph 48 ), as in 5 shown. This can assist a rapid heating of an exhaust catalyst after a cold start.

The first camshaft 16 has an ES at approx. = UT 42 to the maximum compression ratio with advance adjustment of the second camshaft 18 to achieve. Alternatively to the in 3 illustrated situation at 0 ° -Verstellung of the adjuster 28 can also do this as a 0 ° position for the second camshaft 18 be considered, so that then only a retardation takes place. In any case, it is important that the intake cam from the first camshaft 16 in comparison to, for example, in diesel engines usual ES at about 10 ° -25 ° KW to UT is shortened such that the UT position ES can be achieved by both cams.

6 shows a portion of the second mixed camshaft 18 on the axially spaced, for example, four formed as a hollow shaft cam carrier 54 are arranged, in 6 only one of the cam carriers 54 is shown. The following description refers only to the illustrated cam carrier 54 , but also applies to all other, not shown cam carrier on the second camshaft 18 , The cam carrier 54 is on the second camshaft 18 axially displaceable but rotatably mounted. At both ends of the cam carrier 18 is a worm drive with an axial curve formed as a depression or groove 56 respectively. 58 arranged, which winds helically around a cam carrier axis. In other words, the grooves are lost 56 . 58 in the circumferential direction around the cam carrier 54 around. On the cam carrier 54 two cams are arranged, with each cam from the same base circle axially offset two different cam tracks 60 . 62 respectively. 64 . 66 emerge. The cylindrical area of the lateral surface of each cam piece located between the two cams 54 is as a bearing surface for a camshaft bearing 68 educated.

Each cam carrier 54 is with this cylindrical bearing surface in a camshaft bearing block 68 a cylinder head (not shown) rotatably and axially displaceably mounted. The two the camshaft bearing block 68 facing end faces of the cams are as contact surfaces 70 and 72 educated. Accordingly, the cam facing end surfaces of the camshaft bearing 68 as a contact surface 74 respectively. 76 educated. The distance between the two contact surfaces 70 and 72 The cam is larger than the distance between the contact surfaces 74 and 76 of the camshaft bearing 68 , The maximum distance corresponds to the contact surfaces 70 and 72 , or the contact surfaces 74 and 76 can have from each other, the width of the cam tracks 60 . 62 . 64 . 66 , as well as the route that a cam carrier 54 through the axial curves 56 and 58 the worm gear in the axial direction relative to the second camshaft 18 can be moved. Gas exchange valves 78 . 80 The internal combustion engine are from the cam via cam followers 82 . 86 operated to reduce friction with a roller 84 are formed. Here is, for example, a gas exchange valve 78 an inlet valve and the other gas exchange valve 80 an outlet valve.

The rocker arms 82 . 86 associated in a conventional known manner formed in the cylinder head clearance compensation element 88 respectively. 90 ,

In the first position of the cam carrier 54 , as in 6 shown in which the contact surface 70 of the intake cam 24 at the contact surface 74 of the camshaft bearing 68 is present, and in the second position of the cam carrier 54 in which the contact surface 72 the exhaust cam 26 at the contact surface 76 of the camshaft bearing 68 is present, is the cam carrier 54 each fixed in the axial direction by a releasable locking device, as in 6 in the broken exhaust cam 26 is indicated. In this way is the cam carrier 2 fixed for both axial positions.

The adjustment of the Hubventilsteuerung of the in 6 shown operating state in the second position (not shown), takes place in that a driving pin 92 an arranged in the cylinder head electrical actuator 94 , which is the axial curve 56 is assigned, in the recess formed as a groove or axial curve 56 intervenes. By the rotation of the camshaft 18 and the cam carrier 54 is caused by touching contact between the driving pin 92 and the groove walls of the axial curve 56 the cam carrier 54 moved axially to the left. It moves the contact surface 72 the exhaust cam 26 on the contact surface 76 of the camshaft bearing 68 to and device with this in axial contact. The cam carrier 54 is axially fixed in this second position corresponding to a second operating state of the Hubventilsteuerung. The driving pin 92 is by means of the electric actuator 94 in a known manner again from the axial groove formed as a circumferential groove 56 pulled out. To adjust the lift valve control from the second position back to the in 6 shown first position, which corresponds to a first operating state of the Hubventilsteuerung, another Mitnehmerstift 96 one of the axial curve 58 assigned and arranged in the cylinder head electrical actuator 98 from the actor 98 in the formed as a recess or groove other axial curve 58 introduced.

By the rotation of the camshaft 18 over the contact contact between the groove walls of the axial curve 58 and the takeaway pen 96 becomes the cam carrier 54 in 6 axially shifted to the right, so that the contact surface 70 of the intake cam 24 in touching contact with the contact surface 74 of the camshaft bearing 68 comes. The cam carrier 54 is through the plant between investment surface 70 of intake cam 24 and the contact surface 74 of the Lagerbo3 camshaft bearing 68 on the one hand and by the locking device on the other hand fixed axially in both directions. The driving pin 96 is done with the help of the electric actuator 98 in a known manner from the circumferential groove of the axial curve 58 pulled out. The actuation of the electric actuators 94 . 98 is controlled in a known, not shown manner by an engine control unit, not shown.

The on the second camshaft 18 arranged cam carrier 54 can be personalized in this way by the assigned actuators 94 respectively. 98 be adjusted between their two operating positions for Hubventilsteuerung. According to the invention, such a configuration is the adjustment of the lift valve control for a mixed camshaft which controls both intake valves and exhaust valves 18 with camshaft adjuster 28 intended.

LIST OF REFERENCE NUMBERS

10

cylinder head

12

outlet

14

inlet side

16

first camshaft

18

second camshaft

20

Intake cam of the first camshaft 16

22

Exhaust cam of the first camshaft 16

24

Intake cam of the second camshaft 18

26

Exhaust cams of the second camshaft 28

28

adjuster

30

Drive first camshaft 16

32

gears

34

horizontal axis: crank angle

36

vertical axis: lifting movement

38

bottom dead center (UT) of the reciprocating piston before the charge cycle

40

top dead center (TDC) of the reciprocating piston during the charge cycle

42

bottom dead center (UT) of the reciprocating piston after the charge change

44

first graph: stroke movement piston

46

second graph: stroke movement exhaust valves first camshaft 16

48

third graph: stroke movement exhaust valves second camshaft 18

50

fourth graph: stroke movement intake valves first camshaft 16

52

fifth graph: stroke movement intake valves second camshaft 18

54

cam support

56

groove

58

groove

60

Cam track

62

Cam track

64

Cam track

66

Cam track

68

camshaft bearings

70

Contact surface on the end face of the cams

72

Contact surface on the end face of the cams

74

Contact surface of the camshaft bearing 68

76

Contact surface of the camshaft bearing 68

78

Cylinder valve / inlet valve

80

Cylinder valve / exhaust valve

82

cam follower

84

role

86

cam follower

88

Lash adjuster

90

Lash adjuster

92

Carrier pin

94

actuator

96

Carrier pin

98

actuator

100

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

• DE 4426557 A1 [0002]
• DE 4230877 [0005]
• DE 19908286 [0005]

Claims (8)

Internal combustion engine, in particular a diesel engine, in particular a motor vehicle, having at least one working cylinder, each working cylinder having at least two inlet valves ( 78 ) and at least one outlet valve ( 80 ), wherein at least two camshafts ( 16 . 18 ) are provided, of which at least one mixed camshaft ( 18 ) at least one inlet valve ( 78 ) as well as at least one outlet valve ( 80 ), wherein at least one mixed camshaft ( 18 ), which has at least one inlet valve ( 78 ) as well as at least one outlet valve ( 80 ), an adjuster ( 28 ), which valve timing of the mixed camshaft ( 18 ) associated intake and exhaust valves ( 78 . 80 ) with respect to the valve timing of the at least one other camshaft ( 16 ) is adjusted either early or late, characterized in that at least at the mixed camshaft ( 18 ) at least one cam carrier ( 54 ) is provided, wherein the cam carrier ( 54 ) relative to this mixed camshaft ( 18 ) rotationally fixed and axially displaceable on the mixed camshaft ( 18 ), wherein the at least one cam carrier ( 54 ) at least one cam ( 24 . 26 ), on which at least two different cam tracks ( 60 . 62 . 64 . 66 ), where means ( 92 . 96 . 56 . 58 ) for axially displacing the at least one cam carrier ( 54 ) compared to the mixed camshaft ( 18 ) are provided between a first axial position and at least one second axial position. Internal combustion engine according to claim 1, characterized in that the at least one cam carrier ( 54 ) for supporting the at least one camshaft ( 18 ) of at least one cylinder head fixed camshaft bearing ( 68 ) is included. Internal combustion engine according to at least one of the preceding claims, characterized in that the adjuster ( 28 ) is designed such that it has an adjustment range for the valve timing of 60 ° CA +/- 20 °. Internal combustion engine according to at least one of the preceding claims, characterized in that each exhaust cylinder has two exhaust valves ( 80 ), wherein two camshafts ( 16 . 18 ) are provided, wherein a first camshaft ( 16 ) one half of the intake and exhaust valves and a second camshaft ( 18 ) actuates the other half of the intake and exhaust valves, wherein the first camshaft ( 16 ) fixed timing for the camshaft ( 16 ) associated with valves and on the second camshaft ( 18 ) the adjuster ( 28 ) is arranged. Internal combustion engine according to claim 4, characterized in that the second camshaft ( 18 ) is formed such that at an adjustment angle of 0 ° KW that of the second camshaft ( 18 ) associated exhaust valves ( 80 ) close earlier than the first camshaft ( 16 ) associated exhaust valves and the second camshaft ( 18 ) associated intake valves ( 78 ) open later and close later than the first camshaft ( 16 ) associated with intake valves. Internal combustion engine according to claim 4, characterized in that the second camshaft ( 18 ) is formed such that at an adjustment angle of 0 ° KW that of the second camshaft ( 18 ) associated intake valves ( 78 ) simultaneously with the first. Camshaft ( 16 Close associated intake valves. Internal combustion engine according to at least one of the preceding claims, characterized in that the means for axially displacing the at least one cam carrier relative to the mixed camshaft between a first axial position and at least one second axial position at least one relative to the mixed camshaft ( 18 ) axially fixed and radially displaceable between a first and a second pin position bolt ( 92 ), which in the second pin position in one on the cam carrier ( 54 ) formed in the radial direction circumferential groove ( 56 ) engages and in the first bolt position of this groove ( 56 ), wherein the groove ( 56 ) is designed such that the cam carrier ( 54 ) from an axial position on the mixed camshaft ( 18 ) in a different axial position on the mixed camshaft ( 18 ) moves when the bolt ( 92 ) into the groove ( 56 ) intervenes. Internal combustion engine according to claim 7, characterized in that at least one first bolt ( 92 ) is provided which optionally in a first groove ( 56 ) and at least one axially with respect to the mixed camshaft ( 18 ) from the first bolt ( 92 ) complained second bolt ( 96 ) is provided, which optionally in one of the first groove ( 56 ) axially with respect to the mixed camshaft ( 18 ) spaced second groove ( 58 ) engages, wherein the cam carrier ( 54 ) from the first axial position on the mixed camshaft ( 18 ) in the second axial position on the mixed camshaft ( 18 ) moves when the first bolt ( 92 ) into the first groove ( 56 ) and from the second axial position on the mixed camshaft (FIG. 18 ) in the first axial position on the mixed camshaft ( 18 ) moves when the second bolt ( 96 ) into the second groove ( 58 ) intervenes.

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