WO2007079510A2

WO2007079510A2 - Internal combustion engine

Info

Publication number: WO2007079510A2
Application number: PCT/AT2006/000532
Authority: WO
Inventors: Paul Kapus
Original assignee: Avl List Gmbh
Priority date: 2006-01-10
Filing date: 2006-12-21
Publication date: 2007-07-19
Also published as: WO2007079510A3; DE112006003583A5

Abstract

The invention relates to an internal combustion engine comprising at least one first camshaft (2) and at least one second camshaft (3). Said camshafts (2, 3) are interlinked via a coupling gear (4), the first camshaft (2) being rotatable by a first phase shifter (5). The aim of the invention is to reduce the power of friction in the traction mode with minimum complications. For this purpose, the second camshaft (3) can be rotated by a second phase shifter (6) in such a manner that phase-shift of the second camshaft (3) is the result of the sum of adjustment movements of the two phase shifters (5, 6).

Description

Internal combustion engine

The invention relates to an internal combustion engine with at least one first camshaft and at least one second camshaft, which camshafts are interconnected by a coupling drive, wherein the first camshaft is rotatable by a first phase shifter. Furthermore, the invention relates to a method for lowering the friction power in towing operation in an internal combustion engine having a first camshaft and a second camshaft, which camshafts are interconnected by a coupling drive, wherein the first camshaft, a first phase shifter is connected. Furthermore, the invention relates to a method for operating a spark-ignited internal combustion engine with direct fuel injection, which has at least one exhaust gas turbocharger and at least one exhaust aftertreatment device, with at least one means for varying the intake and / or Auslasssteuerzeit, the internal combustion engine, in particular at low speed with a defined valve overlap is operated by intake and exhaust valves for purging the combustion chamber, and wherein the valve overlap is changed in response to at least one engine operating parameter.

Overflow, throttling and friction losses are exploited for the engine braking effect of an internal combustion engine in overrun operation. However, there are operating conditions in which a lower engine braking effect or a reduction of the friction power during towing operation is desired. Such operating states may be required, for example, in hybrid drive concepts, in order to reload a higher amount of energy via an electric machine into an energy store during overrun operation. Even with purely electromotive operation of a hybrid vehicle, it may be advantageous in certain operating areas, when the internal combustion engine is driven in towing by an electric machine, wherein the electric machine also drives the vehicle. In these operating areas, minimum friction losses during towing are desirable.

It is known to use phase shifters for adjusting the control time of a camshaft, which is connected via a coupling drive with a second camshaft. By actuating the phase shifter, the control time of both camshafts can thus be adjusted synchronously to early or late. However, this arrangement is poorly suited for lowering the friction power during towing operation owing to the relatively small adjustment range and the comparatively small adjustment speed. A displacement of the engine operating points, which is achieved by reducing the displacement, toward more fuel-efficient characteristic map points represents an effective measure for reducing fuel consumption in diesel internal combustion engines and in spark-ignition internal combustion engines. To maintain the driving performance, an increase in the power density of the engine through charging is required. Turbocharging is advantageous for various known reasons. However, the disadvantage of this type of charging is a fundamental weakness in stationary and in particular in transient behavior at low engine speeds. The optimization of the charge cycle at very low speeds is a prerequisite for the best possible use of the turbocharger, or other supercharger and thus for a wide usable speed range.

Important for low full load speeds is a purging charge cycle, on the one hand because of an efficient residual gas purging and a high degree of delivery, on the other hand, because of an increase in the mass flow through the turbine. This causes higher turbine work and increasing boost pressure. The risk of compressor pumping is counteracted insofar as the operating points in the compressor map with a purging charge change shift significantly to the right, towards larger throughputs.

At low engine speeds, a large valve overlap is used to push the turbocharger into a better efficiency range. Rinsing is limited by exothermic reactions in the catalyst. Since the catalyst would heat up too much in the stationary state, if it were driven to a constant low speed over a long period of time, the optimal overlap for the best torque build-up is usually not applied in order to avoid excessive catalyst aging.

In turbo engines phase shifters are used to improve the engine torque at low speeds. In this purge strategy there is an increase in HC emissions and the oxygen content in the exhaust gas. This leads to an exothermic reaction in the catalyst and further to catalyst aging, or overheating of the catalyst. Therefore, the overlap, or purging must be limited.

It is known to carry out the valve overlap as a function of the engine temperature, for example from JP 2004-176680 A2 or US Pat. No. 6,109,225 A. However, this permits only a quasi-stationary, in no way a dynamic change of the camshaft position in order to support the boost pressure build-up of a turbocharger. It is the object of the invention to avoid these disadvantages and to provide a device and a method with which the friction of an internal combustion engine can be adjusted quickly and effectively in towing operation. Another object of the invention is to achieve optimum operation of the exhaust gas turbocharger in the transient case.

According to the invention, this takes place in that the second camshaft is rotatable by a second phase shifter so that the phase adjustment of the second camshaft results as the sum of the actuating movements of the two phase shifters. The second phase shifter is arranged between the first and second camshaft, preferably between the coupling drive and the second camshaft. But it is also possible to arrange the second phase shifter between the first and second camshaft. The first camshaft forms an exhaust camshaft, the second camshaft an intake camshaft.

The method according to the invention is characterized in that a second phase shifter between the coupling drive and the second camshaft is connected to the second camshaft and that in at least one predefined engine operating range the second camshaft is rotated by the first and second phase shifters, the rotation of the second camshaft being the sum the torsional movements resulting from the first and the second phase shifter.

To lower the friction power, the exhaust camshaft and / or the intake camshaft are retarded, wherein preferably the retardation of the intake camshaft is greater than the retardation of the exhaust camshaft.

The adjustment ranges for the exhaust camshaft is about 40 ° to 60 °, for the intake camshaft 40 ° to 120 °. It is essential that the adjustment of the second camshaft results by adding the adjustment of the first and the second phase shifter. The coupling drive adds the adjustment paths and the adjustment speeds of the two phase shifters.

It is particularly advantageous if the outlet opening takes place at the latest at 210 ° crank angle, preferably at the latest at 200 ° crank angle after top dead center of the combustion. The inlet closure should be at least at 610 °, preferably at least only at 630 ° crank angle. The intake port of conventional internal combustion engines is in comparison between about 540 ° and 610 ° crank angle. All timing refers to 1 mm valve lift.

Even after phasing the camshafts, there should be minimal valve overlap. Preferably, it is provided that in the cutting range, the stroke of the intersecting valves is at least 0.1 mm, preferably at least 0.3 mm.

This makes it possible, in towing mode with delayed position of both phase shifters (control time, inlet and outlet) to lower the compression, to minimize the filling and thereby reduce the friction loss.

As a result, the internal combustion engine in overrun mode can recharge more energy via the electric machine (generator mode) into the energy store. It is equally possible that the internal combustion engine with low engine braking effect can be operated in overrun mode. Furthermore, a hybrid drive can be operated purely electrically. The internal combustion engine is driven by the electric machine during towing operation. The electric machine also drives the vehicle.

Despite this operation, an operation with an early intake closing and large valve overlap is possible at the full load of the internal combustion engine, that is, the engine delivers even at low speeds torque (for example, turbo hybrid with recharge in any operating condition). For this operation with high torque at low speeds, a timing adjustment is necessary. Since phase splitters are usually required in supercharged internal combustion engines anyway, no additional expenses are required for operation with a late intake deadline.

An optimal operation of the exhaust gas turbocharger can be achieved if the purge is limited or reduced after reaching a threshold value of the engine operating parameter - for example, the boost pressure, an elapsed time, the exhaust gas temperature, the temperature in the catalyst, the engine torque - preferably the valve overlap in the transient operating case is changed.

It is particularly advantageous if, before reaching the threshold value, the valve overlap is set for maximum charge pressure and, after reaching the threshold value, reduced (reduced) to the value for maximum permissible temperature in the catalytic converter.

In the transient case - the acceleration - the critical speed of the turbocharger is only briefly passed through. If the internal combustion engine is operated stationarily in the critical speed range with large overlap, the overlap can be reduced to the catalyst-compatible level. This reduction of the overlap (or purging, or the adjustment of the intake or exhaust camshaft or both camshafts) may be dependent on various calculated or measured engine parameters, such as the pressure, the engine torque, the exhaust gas temperature, the temperature in the exhaust aftertreatment device, or a specific operating time in a particular engine operating condition.

Thus, the torque of the internal combustion engine can be improved by the valve overlap, or the adjustment of the camshaft is adapted to the behavior of the internal combustion engine, or the catalyst.

The invention will be explained in more detail below with reference to FIGS. Show it:

Fig. 1 shows schematically a camshaft arrangement of an internal combustion engine according to the invention;

Fig. 2 is a valve lift diagram; and

Fig. 3 operating parameters in the transient case, plotted over time.

The valve actuating device 1 shown in FIG. 1 has a first camshaft 2 and a second camshaft 3, wherein the first camshaft 2 is designed as an exhaust camshaft and the second camshaft 3 as an intake camshaft. The first camshaft 2 is driven, for example via a traction means 7 by a crankshaft, not shown. By way of first cams 2 a, exhaust valves, not shown further, and inlet valves (not shown further) via second cams 3 a are actuated. The first and the second camshaft 2, 3 are connected to each other via a coupling drive 4, for example a spur gear or a traction mechanism. The first camshaft 2 can be rotated via a first phaser 5. In the exemplary embodiment, a second phase adjuster 6 is arranged between the coupling drive 4 and the second camshaft 3, via which the second camshaft 3 can be rotated relative to the first camshaft 2. But it is also possible to arrange the second phase divider 6 between the first camshaft 2 and the coupling drive 4, as indicated in Fig. 1 by dashed lines. The adjustment of the second camshaft 3 is composed of the sum of the rotational movements due to the first phase adjuster 5 and the second phase adjuster 6, wherein not only the adjustment paths, but also the adjustment speeds of the two phase shifters 5, 6 for the second camshaft 3 add.

In FIG. 2, the valve strokes H for exhaust and intake valves are shown above the crank angle KW, the reference numbers A indicating the valve strokes for the exhaust valves and E the valve strokes for the intake valves. It can be seen that the adjustment of the exhaust valves between 40 ° to 60 ° and the adjustment of the intake valves between 40 ° and 120 °. The intake port is preferably after 610 ° crank angle KW after top dead center the ignition. The start of the outlet opening - based on 1 mm stroke - is a maximum of 210 ° crank angle. Even after the adjustment there should be a minimum overlap of the inlet and outlet valves. By retarding the exhaust timing and the intake timing to the extent indicated, the compression can be lowered in tow mode, the charge can be minimized, and the friction can be reduced. This makes it possible to recharge more energy by means of the electric machine in an energy storage in a hybrid drive via the internal combustion engine in overrun. Furthermore, the internal combustion engine with low engine braking effect can be operated in overrun mode.

In particular, in a so-called mild-hybrid (crankshaft starter generator or belt-driven generator) can be driven electrically, wherein the internal combustion engine is driven in towing by the electric machine, which also drives the vehicle.

Despite this operation, operation at the full load of the engine is possible with early intake closure and large valve overlap. This means that the internal combustion engine delivers torque even at low speeds. Turbo-hybrid drives can be recharged into an energy storage device in any operating state. For this operation with high torque at low speeds anyway a timing adjustment is necessary. For operation with late entry deadline, no or only a small additional effort is required.

The inventive method can be particularly advantageous in internal combustion engines with four gas exchange valves per cylinder realize.

FIG. 3 shows the accelerator pedal position FP, the intake camshaft position adjusting path ENS, the exhaust camshaft position adjusting path ANS, the parameter P (for example the boost pressure) determining the camshaft displacement, and the temperature T in the catalytic converter over the time t. When indicated by the accelerator pedal position FP load request from low load of the intake camshaft actuator and / or the exhaust camshaft actuator is moved in the direction of early or late, so that the valve overlap is changed in terms of a purging charge exchange. Upon reaching a predetermined threshold by the parameter P (time, boost pressure, exhaust gas temperature, or the like) threshold S, the overlap is reduced to the maximum level, which is determined for example by the exhaust gas temperature in the catalyst. As can be seen from the lowest curve T, the temperature T in the catalytic converter rises during the boost pressure build-up and drops again after the valve overlap has been reduced.

Claims

1. Internal combustion engine with at least one first camshaft (2) and at least one second camshaft (3), which camshafts (2, 3) by a coupling drive (4) are interconnected, wherein the first camshaft (2) by a first phase shifter (5 ) is rotatable, characterized in that the second camshaft (3) by a second phase shifter (6) is rotatable so that the phase adjustment of the second camshaft (3) as the sum of the actuating movements of the two phase shifter (5, 6) results.

2. Internal combustion engine according to claim 1, characterized in that the second phase shifter (6) between the first and second camshaft (2, 3), preferably between the coupling drive (4) and the second camshaft (3) is arranged.

3. Internal combustion engine according to claim 1 or 2, characterized in that the first camshaft (2) as the exhaust camshaft and the second camshaft (3) is designed as an intake camshaft.

4. A method for lowering the friction power in towing mode in an internal combustion engine with a first camshaft (2) and a second camshaft (3), which camshafts (2, 3) by a coupling drive (4) are interconnected, with the first camshaft ( 2) a first phase shifter (5) is connected, characterized in that with the second camshaft (3) a second phase shifter (6) between the first and second camshaft (2, 3) is connected and that in at least one predefined engine operating range, the second camshaft (3) is rotated by the first and second phase shifters (5, 6).

5. The method according to claim 4, characterized in that the rotation of the second camshaft results as the sum of the rotational movements due to the first and the second phase shifter (5, 6).

6. The method according to claim 4 or 5, characterized in that for lowering the friction power designed as exhaust camshaft first camshaft (2) and formed as an intake camshaft second camshaft (3) is retarded, preferably wherein the adjustment of the second camshaft (3 ) is greater than the adjustment of the first camshaft (2).

7. The method according to any one of claims 4 to 6, characterized in that in at least one engine operating range designed as exhaust camshaft first camshaft (2) is rotated by 40 ° to 60 ° late.

8. The method according to any one of claims 4 to 7, characterized in that in at least one engine operating range designed as the intake camshaft second camshaft (3) is adjusted by 40 ° to 100 ° to late.

9. The method according to any one of claims 4 to 8, characterized in that the exhaust opening at the latest at 210 ° crank angle, preferably at the latest at 200 ° crank angle after top dead center of the combustion - based on 1 mm valve lift - takes place.

10. The method according to any one of claims 4 to 9, characterized in that the inlet closing later than 610 ° crank angle, preferably later than 630 ° crank angle after the top dead center of the combustion - based on 1 mm valve lift - takes place.

11. The method according to any one of claims 4 to 10, characterized in that the overlap between exhaust and intake stroke is greater than 0 ° crank angle.

12. The method according to claim 11, characterized in that in the overlap region of the stroke of the intersecting valves is at least 0.1 mm, preferably at least 0.3 mm.

13. A method for operating a spark-ignited internal combustion engine with direct fuel injection, which has at least one exhaust gas turbocharger and at least one exhaust aftertreatment device, with at least one device for changing the intake and / or Auslasssteuerzeit, the internal combustion engine, in particular at low speed with a defined valve overlap of Ein. and exhaust valves are operated for purging the combustion chamber, and wherein the valve overlap is changed in response to at least one engine operating parameter, characterized in that the purging is limited or reduced after reaching a threshold value of the engine operating parameter.

14. The method according to claim 13, characterized in that before reaching the threshold, the valve overlap is set for maximum boost pressure and after reaching the threshold value is reduced for maximum allowable temperature in the catalyst after reaching the threshold.

15. The method according to claim 13 or 14, characterized in that the engine operating parameter is the boost pressure.

16. The method of claim 13, wherein the engine operating parameter is a calculated or measured engine torque.

17. The method according to any one of claims 13 to 16, characterized in that the engine operating parameter is a measured or calculated temperature at the exhaust gas aftertreatment device.

18. The method according to any one of claims 13 to 17, characterized in that the engine operating parameter is a predefined operating time.

19. The method according to any one of claims 13 to 18, characterized in that the valve overlap is changed in the transient operating case.