WO1997007324A2

WO1997007324A2 - Internal combustion engine and process for operating the valve gear mechanism of an internal combustion engine

Info

Publication number: WO1997007324A2
Application number: PCT/DE1996/001538
Authority: WO
Inventors: Erwin Korostenski; Armin Bertsch; Reiner Walter
Original assignee: Erwin Korostenski; Armin Bertsch; Reiner Walter
Priority date: 1995-08-19
Filing date: 1996-08-19
Publication date: 1997-02-27
Also published as: AU7617696A; WO1997007324A3

Abstract

An internal combustion engine is disclosed with a device for cyclically changing the speed of rotation of a gas exchange control cam with two similar valves per combustion chamber. A cam is associated to each valve and at least one of the cams is linked to the device and controlled in such a way that its associated valve is completely open at a different moment in time than the other valves. The valves are fully open at the same time in the higher speed of rotation and/or load range and are offset in time in the lower speed of rotation and/or load range. According to the disclosed process for operating a valve gear mechanism of an internal combustion engine, in the lower speed of rotation and/or load range both inlet valves are preferably separately driven. Starting from a position in which both inlet valves are completely open at the same time, one of the cams is controlled in such a way that its associated inlet valve opens completely at an earlier moment in time and the other cam is controlled in such a way that its associated inlet valve opens completely at a later moment in time.

Description

Internal combustion engine and working method of a valve train of an internal combustion engine

The invention relates to an internal combustion engine with a device for cyclically changing the rotational speed of a cam for gas exchange control and a working method of a valve drive of an internal combustion engine with a device for cyclically changing the rotational speed of a cam for gas exchange control.

In internal combustion engines with two intake valves per cylinder, it has been considered to switch off an intake valve in the lower speed range in order to generate a strong swirl with the charge which enters the combustion chamber via the other intake valve. This improves the mixture preparation and a relatively large proportion of residual gas, that is to say combustion gas, can be permitted in the combustion chamber, as a result of which the fuel consumption can be reduced. However, a relatively large effort is required for valve shutdown.

WO 95/02116 describes a method and a device for variably controlling a valve of an internal combustion engine for throttle-free load control of an Otto engine via the lifting function of one or more intake valves per cylinder. This document suggests intake valves to be closed at different times

REPLACEMENT BLAπ (RULE 26) open so that a specific charge movement is caused in the combustion chamber.

In the German patent application 195 02 834.1 not yet published before the priority date of the present application, a valve train is described in which the

Current speed and the phase position of two identical cams relative to the camshaft and thus the

Opening time and the spread of the valves operated by these cams can be changed. Similar valves are either two inlet valves or two

Exhaust valves. Under the term "spread" the

Distance of the highest valve lift from top dead center

(OT) understood the associated piston of the valve lift curve.

The problem on which the invention is based is to adapt the inflow conditions of the fresh gas and / or the outflow conditions of the combustion gas and the charge movement in the combustion chamber in an internal combustion engine to the requirements in different operating points of the internal combustion engine as optimally as possible without increasing the construction effort of the internal combustion engine inadmissibly.

The solution to this problem is given in the claims.

In particular, an internal combustion engine is proposed with a device for cyclically changing the speed of rotation of a cam for gas exchange control with two identical valves per combustion chamber, each of which is assigned a cam, at least one of the cams being operatively connected to the device for cyclically changing the speed of rotation of a cam, and so on controllable is that the valve assigned to it is fully open with a time offset compared to the other similar valve, and the Valves of the same type are fully open at the same time in the upper speed range and / or in the upper load range and are fully open at different times in the lower speed range and / or in the lower load range.

In the internal combustion engine according to the invention, one intake valve in particular is thus later fully opened in the lower speed range than the other intake valve, so that the majority of the charge flows into the combustion chamber via the other intake valve and generates the desired swirl there.

A time offset of the times of the different opening of the valves of the same type, in particular of the inlet valves, is preferably limited to a speed of less than 50% of the maximum speed and / or a load range of less than 50% of the maximum load, one as a measure of the maximum load maximum throttle valve opening, a maximum injection quantity or a maximum boost pressure can be selected.

In a preferred embodiment of the invention,

Range of the highest piston speed, that means in the range from about 65 ° to TDC to about 85 ° to TDC, in particular at 75 ° to TDC, the stroke of one intake valve is significantly smaller than that of the other intake valve, the stroke of the one that is less open in this area Intake valve is about 50% of the stroke of the other intake valve. The stroke of the inlet valve which later reaches its maximum stroke is preferably about 30% of the maximum valve stroke in this area.

In a preferred embodiment of the invention, the cams of both inlet valves can be controlled independently of one another and accordingly their speed of rotation can be changed cyclically independently of one another. This enables the change to be made in opposite directions, so that the spread of one intake valve is reduced and the spread of the other intake valve is increased. As a result, the one inlet valve opens earlier and the other inlet valve later, which increases the distance between the times at which the respective inlet valves are fully open and accordingly the vast majority of the charge flows into the combustion chamber via the earlier opening inlet valve.

There is also the possibility of shaping the two cams so that the two inlet valves have different maximum strokes and / or a different opening duration. In a preferred embodiment, the cams are shaped such that one inlet valve opens later and closes earlier and has a smaller maximum stroke than the other inlet valve.

An exemplary embodiment of the invention is described below with reference to the drawings. It shows:

1 is a partial longitudinal section of a valve train with two rotatable cams for the actuation of two intake valves of a cylinder,

2 shows a section along line 2-2 in FIG. 1,

3 shows a schematic illustration of the eccentrics assigned to the two intermediate members in the position of the maximum displacement of the intermediate members,

4 shows the valve lift curves of the two intake valves, which result in the eccentric in the position shown in FIG. 3, 5 shows a schematic representation of the eccentrics in the position in which the spread of one inlet valve increases and that of the other inlet valve is reduced,

6 shows the valve lift curves of the two intake valves, which results from the position of the eccentric shown in FIG. 5,

7 shows a representation of the valve lift curves for the exhaust valves EX and the intake valves IN, wherein in addition to the basic setting, a valve lift curve shifted in the early direction and a valve shift curve shifted in the late direction is shown for the intake valves.

FIG. 8 shows a representation corresponding to FIG. 7, wherein in addition to the respective base curves, five valve lift curves for an inlet valve are shown which are shifted differently in the direction of early,

FIG. 9 shows a representation corresponding to FIG. 8, five valve lift curves for an intake valve being shifted differently in the late direction, and

10 is a representation in which the curves shifted in the early and late directions according to FIGS. 8 and 9 are shown together.

Reference is first made to FIGS. 1 and 2. On the camshaft 1, the axis of rotation of which is denoted by 2, are rotatably mounted first and second cams 3 and 4, which actuate first and second inlet valves of a cylinder of an internal combustion engine (not shown) via key tappets 5 and 6.

The adjustment devices for the two cams 3 and 4 are identical, so that only the following Adjustment device for the first cam 3 and its mode of operation is described. The parts of the adjusting device for the second cam 4 are identified by the same reference numerals, but with a dash.

In addition to the cam 3, an inner eccentric 7 is mounted on the camshaft 1, which has an eccentric outer circumferential surface 8 on which an outer eccentric 9 is rotatably mounted. On the outer surface 10 of the outer eccentric 9, which is eccentric to its bearing surface (= circumferential surface 8), an annular intermediate member 11 is rotatably mounted, on the one hand being drivingly connected to the camshaft 1 and on the other hand to the cam 3. The connection to the camshaft 1 takes place in the embodiment by means of a radially arranged pin 12, which is articulated with a cylindrical head 13 in a bore 14 in the intermediate member 11 parallel to the axis of rotation 2 of the camshaft 1 and is displaceable through a radial bore 15 in the camshaft 1 extends. On its side facing the cam 3, the intermediate member 11 has a sliding guide in the form of a radial groove 16. A transmission element 17 in the form of a pin is rotatably mounted in an axially parallel bore 18 in the cam 3 and carries a sliding block 19 which engages in the radial groove 16. The inner eccentric 7 carries an outer ring gear 20 which is coaxial with the camshaft axis of rotation 2. On an outer surface 21 of the inner eccentric 7 which is coaxial with the camshaft axis of rotation 2, an outer ring gear 22 is mounted which engages with a lug 23 in a radial groove 24 on the outer eccentric 9. The inner eccentric 7 and the outer eccentric 9 can be rotated together or relative to one another by adjusting wheels (not shown) which engage in the outer ring gear 20 and 22, as a result of which the intermediate member 11 is displaced relative to the camshaft 1. The rotation of the camshaft 1 is transmitted to the intermediate member 11 via the pin 12. The resulting rotation of the intermediate member 11 is transmitted to the cam 3 via the sliding block 19 engaging in the radial groove 16. If the eccentricity el of the circumferential surface 8 of the inner eccentric 7 is equal to the eccentricity e2 of the circumferential surface 10 of the outer eccentric 9 and both eccentrics 7 and 9 are at such an angular position that their eccentricities are opposite one another, as shown in FIGS. 1 and 2 , the intermediate member 11 is in a position in which its axis of rotation Z coincides with the camshaft axis of rotation 2. In this position, the cam 3 rotates synchronously with the camshaft 1. As will be described later in connection with FIGS. 3 to 6, the intermediate member 11 can be displaced relative to the camshaft rotation axis 2 by appropriate rotation of the inner and outer eccentric. In the case of a radial displacement in the direction of the valve axis V (FIG. 3), the angular velocity of the cam 3 relative to the camshaft 1 is changed cyclically and the opening duration of the intake valve is thus changed so that it is actuated via the tappet 5. When the intermediate member 11 is displaced at an angle to the valve axis V (FIG. 5), the spreading of the inlet valve, that is to say the distance between its largest valve elevation and TDC, is also changed.

3, the eccentrics 7, 9 and 7 ¹ , 9 ^{1 are} rotated 90 ° in the opposite direction from the position shown in FIG. 2, so that the axes of rotation Z of the intermediate members in the

Valve axis V are shifted radially outwards by the sum e of the eccentricities el and e2 with respect to the camshaft axis of rotation 2. The angular velocity of the cams, which are driven by the intermediate members, changes cyclically relative to the angular velocity of the camshaft such that the opening duration of the Intake valves is reduced. 4, the valve lift curve Eι_ of the first valve actuated by the cam 3 and the valve lift curve E ₂ of the second valve actuated by the cam 4 are shown in solid lines in the position of the inner and outer eccentrics shown in FIGS. The cams 3 and 4 have different shapes in the exemplary embodiment, so that the first inlet valve has a larger opening duration and a greater maximum thrust than the second inlet valve. Due to the rotation of the eccentrics 7, 9 and 7 ', 9', the valve lift curves are given the shape Ei 'or E2' shown in broken lines. It can be seen that both intake valves open later and close earlier. With such a radial displacement of the axes of rotation Z of the intermediate members, the spread of the inlet valves, ie the distance Si or S2 of the maximum stroke from TDC, remains unchanged. Any intermediate positions of the outer and / or inner eccentrics are also possible in order to give the valve lift curves a certain shape.

5, the inner and outer eccentrics 7, 9 are common from the position of FIG. 3 by an angle φ i against the direction of rotation D of the camshaft and the inner eccentrics 7 ', 9' are common by the same angle U> 2 i ⁿ the direction of rotation D rotated. This results in a corresponding displacement of the axes of rotation Z of the intermediate links, which has the effect that, as shown in FIG. 6, the stroke curve Ei 'is shifted to the left compared to FIG. 4 and the stroke curve E2' is shifted to the right. With a constant opening duration, the spread Si 'of the first inlet valve is thus reduced and the spread S ₂ ' of the second inlet valve is increased. It can be seen that now the second inlet valve opens much later than the first inlet valve, so that the major part of the charge flows through the first inlet valve into the combustion chamber and generates the desired swirl there. If the valve lift curves are rotated accordingly by and / or external eccentrics are placed in such a way that in the region of the greatest piston speed, which occurs approximately at 75 ° KW after TDC, the stroke h _{2 of the} second inlet valve is substantially smaller than the stroke hi of the first inlet valve and is, for example, only about 50% of the same , the effect of a complete shutdown of the second inlet valve is largely achieved.

As can be seen from the diagram in FIG. 6, even if the spread Si of the first inlet valve were reduced, the charge in the region of the greatest piston speed would predominantly flow via the first inlet valve. This effect is intensified by the simultaneous increase in the spread S _{2 of} the second inlet valve. This enlargement of the spread S ₂ is particularly expedient if the cam actuating the second inlet valve has such a shape that the stroke curve E ₂ generated by it is closer to the stroke curve Ei in order to achieve a greater filling in the upper speed range. It is also conceivable that only by increasing the spread S ₂ a flow of the charge via the first inlet valve sufficient to generate a swirl in the combustion chamber is achieved.

From the above, it can be seen that the angles ψ 1 and ιJ> ₂ do not have to be the same, but can be different depending on the desired change in the spread.

7 shows a valve lift curve EX for an exhaust valve and a valve lift curve IN for an intake valve. The curves EX and IN referred to as base curves correspond to the control times which are provided for the upper speed and / or load range, in particular for the upper speed range. In the exemplary embodiment shown there, the cam shape and thus the opening duration and the maximum stroke are similar valves equal. In the lower speed and / or load range, in particular in the lower speed range, an eccentricity is set in each case, which has the consequence that the spread and the valve opening duration of an intake valve is shortened (curve 1), while the spread of the second intake valve is greater when the opening duration is also shortened is set (curve 2).

8 shows the valve lift curves for five different eccentricities from e = 0.5 mm to e = 2.5 mm for an angle LP of + 50 °.

FIG. 9 shows the valve lift curves for the same eccentricities as in FIG. 8, but with a phase angle U> of -30 °.

10 shows the valve lift curves of FIGS. 8 and 9 in a common representation. This shows how a desired temporal offset of the valve lift curves of two intake valves can be achieved by gradually increasing the eccentricity.

The invention can also be advantageously used in diesel internal combustion engines with two intake valves per cylinder. So far, a swirl duct and a filling duct have been provided in such internal combustion engines in order to achieve a strong swirling of the injected fuel with the air with the swirl generated by the swirl duct, which is particularly important in the lower speed range. However, the swirl channel reduces the filling and thus the performance in the upper speed range. In a diesel internal combustion engine with a valve train operating according to the invention, both inlet channels can be designed as filling channels, since the late opening of one inlet valve in the lower speed range causes the combustion air to flow predominantly into the combustion chamber via the other inlet valve and there the desired swirl is generated, even if the inlet duct assigned to this other inlet valve is designed as a filling duct, possibly with a small swirl effect.

Eε εei mentions that the change in the opening time of the expansion described above in connection with two inlet valves can in principle also be carried out with two outlet valves using the same adjusting devices. This can be useful, for example, in an internal combustion engine with an exhaust gas turbocharger, in which one exhaust duct is connected to the turbine of the exhaust gas turbocharger and the other exhaust duct is connected to a bypass line that bypasses the turbine. By changing the spread and the opening duration of one or both exhaust valves in such a way that the exhaust valve, which is assigned to the exhaust duct connected to the bypass line, opens later than the other exhaust valve, the exhaust gas flow is predominantly supplied to the turbine. To reduce or limit the boost pressure, the opening of the first-mentioned exhaust valve is started earlier, so that a larger partial flow of the exhaust gas can flow past the trubine into the bypass line.

Claims

claims

1. Internal combustion engine with a device for cyclically changing the rotational speed of a cam

Gas exchange control,

with two identical valves per combustion chamber, to which a cam (3, 4) is assigned,

wherein at least one of the cams (3, 4) is operatively connected to the device for cyclically changing the speed of rotation of a cam and can be controlled such that the valve associated therewith is fully opened with a time offset with respect to the other similar valve, and

the similar valves in the upper

Speed range and / or in the upper load range are fully open at the same time and in the lower

Speed range and / or in the lower load range are fully open with a time delay.

2. Internal combustion engine according to claim 1, wherein the lower speed range is defined by a speed of less than 50% of the maximum speed and the lower load range by a load of less than 50% of the maximum load.

3. Internal combustion engine according to claim 2, wherein the measure for the maximum load is a maximum throttle valve opening, a maximum injection quantity or a maximum boost pressure.

4. Internal combustion engine according to one of the preceding claims, wherein the similar valves are intake valves.

5. Internal combustion engine according to claim 4, wherein in the region of the highest piston speed of the internal combustion engine the stroke of an intake valve is substantially smaller than that of the other intake valve.

6. Internal combustion engine according to claim 5, wherein in the region of the highest piston speed of the internal combustion engine, the stroke of one intake valve is approximately 50% of the stroke of the other intake valve.

7. Internal combustion engine according to claim 5 or 6, wherein in the region of the highest piston speed of the internal combustion engine the stroke of the intake valve later reaching its maximum stroke is approximately 30% of the maximum Ventilhubε.

8. Internal combustion engine according to one of claims 4 to 7, the range of the highest piston speed of the internal combustion engine being the range from 65 ° to TDC to 85 ° to TDC, in particular 75 ° to TDC.

9. Internal combustion engine according to one of the preceding claims, wherein the cams (3, 4) of both intake valves

* - ^ their rotation speed can be changed cyclically independently of each other.

10. Internal combustion engine according to claim 9, wherein starting from a position in which both intake valves are fully open at the same time, a cam (3) can be controlled so that the associated intake valve is fully opened earlier, and the other cam (4) can be controlled is that the inlet valve assigned to it is later fully opened.

11. Internal combustion engine according to one of the preceding claims, wherein the two identical cams (3, 4) are shaped and arranged such that the respectively assigned valves have different maximum strokes, Spread and / or have a different opening time.

12. Internal combustion engine according to one of the preceding claims, wherein the device for cyclically changing the rotational speed of a cam has a camshaft (1) surrounding an annular intermediate member (11), on the one hand with the camshaft (1) and on the other hand with that on the camshaft (1 ) mounted cams (3, 4) drive-connected and radially displaceable to the axis of rotation (2) of the camshaft (1), whereby the

Current speed and the phase position of the cam

(3, 4) opposite the camshaft (1) and thus the

Opening time and the spread of the associated valve is changeable.

13. Internal combustion engine according to claim 12, wherein the intermediate member (11) is rotatably mounted on an outer eccentric (9) which is rotatably mounted on an eccentric circumferential surface (8) of an inner eccentric (7) rotatably mounted on the camshaft (1).

14. Working method of a valve train ^"of an internal combustion engine with a device for cyclically changing the rotational speed of a cam for gas exchange control and with two identical valves per combustion chamber, each of which is assigned a cam (3, 4), at least one of which with the device for cyclically changing the rotational speed of a cam is operationally connected,

whereby at least one of the cams (3, 4) is driven in a manner dependent on the load and / or speed so that the valve associated therewith is fully opened with a time offset compared to the other similar valve, and the similar valves in the upper

Speed range and / or in the lower load range are fully open with a time delay.

15. Working method according to claim 14, the lower speed range being defined by a speed of less than 50% of the maximum speed and the lower load range being defined by a load of less than 50% of the maximum load.

16. Working method according to claim 15, wherein a maximum throttle valve opening, a maximum injection quantity or a maximum boost pressure is selected as a measure of the maximum load.

17. Working method according to claim 14, 15 or 16, wherein the similar valves are intake valves.

18. Working method according to claim 17, wherein the control is carried out so that the stroke of an intake valve is substantially smaller than that of the other intake valve in the region of the highest piston speed of the internal combustion engine.

19. Working method according to claim 18, wherein the control takes place in such a way that in the area of the highest piston speed of the internal combustion engine, the stroke of an inlet valve is approximately 50% of the stroke of the other

Intake valve is.

20. Working method according to claim 18 or 19, wherein the control takes place so that in the area of the highest piston speed of the internal combustion engine the stroke of the ε later ε its maximum stroke intake valve is about 30% of the maximum valve lift.

21. Working method according to one of claims 18 to 20, wherein the range of the highest piston speed of the internal combustion engine is the range from 65 ° to TDC to 85 ° to TDC, in particular 75 ° to TDC.

22. Working method according to one of claims 14 to 21, wherein the cams (3, 4) of both inlet valves are changed independently of one another cyclically in their rotational speed.

23. Working method according to claim 22, wherein, starting from a position in which both intake valves are fully open at the same time, a cam (3) is actuated such that the intake valve assigned to it is opened fully earlier, and the other cam (4) is actuated in this way is that the inlet valve assigned to this is later fully open.