This object is achieved by the methods described in Claims I and 3 and
also by the control system defined in claim 7.
On the one hand, the invention is based on the knowledge that the switches in operating mode should be performed dependent on the operational situation and/or the user behaviour. Therefore the operational situation, for example the travelling situation of a motor vehicle equipped with the internal combustion engine, and/or the user behaviour, for example the behaviour of the driver of a motor vehicle equipped with the internal combustion engine, is classified. This classification can be carried out with regard to the number of load switches taking place, the number of time gradients of the load requests etc., as is known for example in the case of adaptive gearbox controllers for internal combustion engines. The operating mode is then chosen, dependent on the classification, in such a way that the requested torque can be produced. Unnecessary switches in operating mode are rendered avoidable by taking the user behaviour and/or the operational situation into consideration.
3 The advantageous way of taking these factors into consideration is to define a changeover curve that reflects the torque produced by the internal combustion engine as a function of the rotational speed. In the case of torque requests lying above the changeover curve, an operating mode is chosen in which the internal combustion engine has a higher rotational speed dependent torque, lambda- I -regulated operation for example. In the case of torque requests lying below the changeover curve, an operating mode is chosen in which the internal combustion engine has a lower rotational speed dependent torque, homogeneous-lean or layered-lean operation for example. It is naturally also possible to provide multiple changeover curves. This changeover curve or these changeover curves is/are then modified, displaced for example, according to the classification of the user behaviour and/or the operational situation. This means, for example, that in the case of a driver who is interested in the power of the vehicle, the number of switches in operating mode is reduced because as a result of the classification the changeover curves are modified in such a way that the leaner operating modes are selected later and fewer switches in operating mode occur. A different behaviour results for a deliberately economy-minded driver, in which case the internal combustion engine is preferentially operated with higher lambda values.
On the other hand, the invention is based on the knowledge that in the case of an internal combustion engine which drives a controllable gearbox the choice of the gearbox setting, in other words normally the selected gear, is linked to the choice of the operating mode. In this situation, the operating mode is selected and the gear shift is effected in such a way that the torque requested by the user can be produced and the fuel consumption of the internal combustion engine involved in doing so is minimal.
4 By preference, the internal combustion engine is kept in the layeredlean operating mode in this situation because throttle-valve losses do not then apply. On the one hand, this happens for as long as the requested torque can be produced. If necessary the gearbox setting, i.e. the gear, is changed in such a way as to effect an increase in rotational speed, as a consequence of which the torque produced by the internal combustion engine naturally increases. On the other hand, the increased fuel consumption resulting from throttlevalve losses in the homogeneous-lean or lambda-I operating modes must be greater than the increased fuel consumption resulting from the increase in rotational speed.
In the control system according to the invention, a normally present operations control unit and a gearbox control unit, which is similarly normally present in the case of controllable gearboxes, are networked by means of a communications line in such a way that a classification signal generated in the gearbox control unit is fed to the operations control unit and a torque request signal generated in the operations control unit is fed to the gearbox control unit. This means that the gearbox control unit can effect the setting of the reduction in the gearbox dependent on the torque request signal, and the operations control unit can effect selection of the operating mode dependent on the classification signal.
In a preferred embodiment, the control system has a synchronisation line between the operations control unit and the gearbox control unit, over which these two units exchange appropriate signals, thereby enabling the gearbox stage changeovers to be synchronised with the switches in operating mode in the case of a gearbox which is adjustable in stages.
Useful further embodiments of the invention are set down in the subclaims.
Embodiments of the invention will be described in detail in the following with reference to the drawings. In the drawings:
Figure I shows the torques which can be produced by an internal combustion engine in different operating modes, Figure 2 shows curves giving the maximum torque as a function of the rotational speed, and Figure 3 shows a schematic representation of a control system for an internal combustion engine with an adjustable gearbox.
An internal combustion engine which can be operated in different operating modes identified by different lambda values produces a different maximum torque according to the operating mode. An example of an internal combustion engine of this type is an internal combustion engine with direct petrol injection.
Fig. I shows the torques M which can be produced in the respective operating modes. Duning lambda-1 operation, load control for the internal combustion engine is effected by way of a throttle controller in the intake section. To this end, a throttle valve is controlled appropriately. In this operating mode, the torque which can be produced by the internal combustion engine is freely modifiable between idling and full load.
In homogeneous-lean operating mode at a lambda value of 1.4, load control is similarly effected by way of throttle-valve control. The maximum 6 torque produced by this operating mode is however less than in lambda-I operation.
Although the lambda range between 1.0 and 1.4 can in theory be set on an internal combustion engine, this lambda range should however be avoided for reasons concerning exhaust gas.
The third operating mode is the layered-lean operating mode with lambda values of 1.8 and greater. In this operating mode the throttle valve is fully open and the load control of the internal combustion engine is effected by way of the injected fuel quantity.
An internal combustion engine cannot be operated with lambda values between 1.4 and 1.8 because a homogeneously lean mixture would be weakened to such an extent at lambda values in excess of 1.4 that reliable ignition is no longer guaranteed. A layered-lean mixture cannot be produced at lambda values below 1.8, however, because the high mixture concentrations which would be required for this cannot be produced and/or cannot be maintained until the point of ignition. This would result in misfirings or excessive soot formation.
The torque which can be produced by the internal combustion engine is naturally dependent not only on the lambda value but also on the rotational speed n. The curve I drawn in Fig. 2 represents a typical fullload characteristic curve for the lambda- I operating mode. As can be seen, the torque M provided by the internal combustion engine under full load conditions rises with the rotational speed n to a maximum value and then drops off slightly.
7 Reference will be made later to the curves 2 and 3 shown in Fig. 2. There are a number of possible methods for selection of the operating mode in the case of an internal combustion engine which can be operated in the operating modes described above.
1. Driver and driving situation classification In the case of an internal combustion engine which is powering a vehicle, the driver who actuates the accelerator pedal of the vehicle is classified. Through the accelerator pedal, the driver causes the internal combustion engine to operate and thereby to produce the requested torque. Since the switch from one operating mode to another requires a specific amount of time and the requested torque sometimes cannot be implemented in every operating mode, switches in operating mode are unavoidable.
If the internal combustion engine is always operated in the leanest operating mode, which would be the obvious course of action for reasons of fuel consumption, certain limitations in respect of response behaviour and/or comfort must then be taken into account because of the occurrence of frequent switches in operating mode. These effects are intensified if the driver frequently requests different torques. The underlying cause for this driver behaviour may be a performance-orientated manner of driving, restricted driving experience, or driving situations involving frequent load switches (such as winding country roads).
In order to be able to decide when a switch in operating mode should be performed or which operating mode is to be selected, a changeover curve is defined which is entered as curve 2 in Fig. 2 by way of example. In the case of torque requests above the changeover curve, the internal combustion 8 engine is operated in lambda- I -regulated operating mode; in the case of torque requests beneath the changeover curve, it is operated in homogeneouslean operating mode. Naturally, a similar changeover curve is defined for the transition between homogeneous-lean and layered-lean operating modes, but for the sake of clarity this has not been entered in Fig. 2. What has- been stated in relation to the changeover curve reproduced in curve 2 also applies by analogy to the changeover curve between homogeneous-lean operating mode and layered-lean operating mode.
In the case of a driver exhibiting a performance-orientated manner of driving or in the case of a driving situation involving frequent load switches, the changeover curve is then modified such that the curve 2 is shifted down on the torque scale by the amount d, producing curve 3. Through this modified changeover curve, a switch in operating mode to lean operation when the requested torque M drops is actually performed later than would be provided for by the changeover curve according to curve 2.
The number of switches in operating mode is consequently reduced in the case of a driving perfonnance orientated driver.
Similarly, in the case of an economy-minded driver or a corresponding driving situation where few load changes occur with a generally lower torque requirement, it is possible to shift the changeover curve up on the torque scale relative to curve 2. When a changeover curve is shifted in this way, lean operating modes are selected wherever possible, resulting in more efficient fuel consumption by the internal combustion engine.
9 The classification of the driver and/or the driving situation is known in the case of gearbox controllers. Common algorithms can therefore be used for the classification described above.
It is advantageous to select the displacement d of the changeover curve, dependent on the classification result, between zero and a maximum value because this produces better results than simply activating or deactivating a predefined displacement.
If the internal combustion engine in the vehicle drives a controllable gearbox, the classification result which is present in any case in the gearbox controller can be used for the displacement of the changeover curve.
A schematic representation of such an arrangement is shown in Fig. 3: An internal combustion engine 6, which can be operated in different operating modes as previously mentioned, drives via an output 9 a variable gearbox 7 which takes the power of the internal combustion engine 6 to the drive shaft 8. The variable gearbox 7 can be an automatic multi-stage gearbox with torque converter, an automatic gear-change gearbox, or a continuously variable transmission (CVT). The operation of the internal combustion engine 6 is controlled via lines 15 by an operations control unit 5. To this end, the operations control unit 5 reads in operating parameters via lines 16 and receives the signal fed from an accelerator pedal 10.
The operations control unit 5 has a driver interpretation module I I to which the signal from the accelerator pedal 10 is fed. The driver interpretation module I I is connected to an operating mode selection module 12 which activates appropriate operating mode blocks 13a to 13c by setting a switch 14. The output from the driver interpretation module I I is connected via a communications line 17 to the gearbox control unit 4.
The gearbox control unit 4 has a driver classification module 19 and a driving situation recognition module 20. These two modules receive information via lines (not shown) which the modules require for classification purposes, for example the signal from the accelerator pedal 10. Both modules feed a gear selection circuit 21 which drives a gear change module 22. In the case of a continuously variable transmission 7, the gear selection circuit 21 and the gear change module 22 are naturally combined to form a single transmission setting circuit.
The gear selection circuit 21 is connected to the communications line 17. The output from the driver classification module 19 is connected via a communications line 18 to the operating mode selection module 12. Optionally, the output from the driving situation recognition module 20 can also be connected to this communications line 18.
Via the communications line 18, the results of the driver classification process and optionally also of the driving situation recognition process, which take place in the driver classification module 19 and the driving situation recognition module 20 of the gearbox control unit 4 respectively, are notified to the operating mode selection module 12 where the results are evaluated and used for determining the amount of the displacement d of the changeover curve or curves.
In the driver interpretation module 11, the operations control unit 5 interprets the signal from the accelerator pedal 10, thereby enabling it to determine the torque requested by the internal combustion engine 6. This torque is fed to the operating mode selection module 12 which selects the operating mode for the internal combustion engine by taking into consideration the results of the driver classification and, where appropriate, the driving situation recognition processes notified by way of the communications line 18. Depending on the outcome of this, the appropriate operating mode block 13a, 13b or 13c is activated by way of the switch 14 in such a way that it determines the operating mode for the internal combustion engine 6 by way of the lines 15.
2. Combination of operating mode selection and gearbox control In the changeover system represented in Fig. 3, the operations control unit 5 and the gearbox control unit 4 can act together in such a way that the torque requested by the driver is fed by the driver interpretation module I I via the communications line 17 to the gear selection circuit 21 together with other control and information signals. The gear selection circuit 21 then chooses the gear and thus the reduction ratio of the gearbox 7 in such a way that the requested torque can be produced in the most fuel-efficient operating mode, i.e. in the leanest operating mode.
This process can be explained in more detail with reference to Fig. 2. As can be seen from Fig. 2, by increasing the rotational speed n it is possible to increase the torque M of the internal combustion engine. So if a particular torque is requested by the driver, for example the torque MI in Fig. 2, this torque request can then be handled by increasing the rotational speed above nI without switching to the operating mode using a richer mixture because for rotational speeds in excess of nI the torque MI lies beneath the changeover curve 2.
12 The fuel economy achieved in this way is particularly significant in situations when it is possible to keep the internal combustion engine 6 running in the layered-lean operating mode. The internal combustion engine should be kept in this operating mode where the load control is achieved without throttle action for as long as possible until the increased fuel consumption caused by the increase in rotational speed exceeds the increased fuel consumption resulting from throttle-action losses minus the reduced fuel consumption resulting from the reduction in rotational speed which would occur in the homogeneous-lean or lambda- I - regulated operating modes.
To this end, the driver interpretation module I I and the operating mode selection module 12 communicate constantly via a communications line (not shown in Fig. 3) and calculate the increased fuel consumption resulting from the fact that the rotational speed of the internal combustion engine 6 needs to be increased in order to be able to produce a requested torque in the layered-lean operating mode. If both modules ascertain that, when the gearbox changes to a higher gear with a lower reduction, the increased fuel consumption resulting from throttle-action losses minus the reduced fuel consumption resulting from the reduction in rotational speed is less than the increased fuel consumption resulting from the increase in rotational speed in the layered-lean operating mode, the operating mode selection module 12 initiates an appropriate gear change in the gear change module 22 via a communications line 25. This gear change is synchronised with the switch in operating mode. The synchronised changes provide for a greater level of comfort than would be achieved if the changes took place independently and were not synchronised.
13 This particular benefit of synchronised changes naturally has general applicability and does not only apply on leaving the layered-lean operating mode.
This description of two embodiments should not be thought of as restrictive, however, as individual features of these embodiments may also be omitted within the framework of the claims, or features from the two embodiments may be combined.
14 CLAIMS 1. Method for the selection of the operating mode for an internal combustion engine operated in a user-dependent fashion which can be operated in different operating modes, where the rotational speed dependent maximum torque of the internal combustion engine is different in each of the operating modes, in which method - the torque requested by the user is determined, - a classification of the user behaviour and/or the operational situation is performed, and - depending on the result of the classification, the operating mode is selected in such a way that the requested torque can be produced.
2. Method in accordance with Claim 1, in which a changeover curve (1,2,3) showing the torque (M) of the internal combustion engine (6) as a ftinction of the rotational speed (n) is defined, characterised in that in the case of torque requests occurring above the changeover curve (1,2,3) an operating mode is chosen in which the internal combustion engine (6) has a higher rotational speed dependent torque (M), in the case of torque requests occurring beneath the changeover curve (1,2,3) an operating mode is chosen in which the internal combustion engine (6) has a lower rotational speed dependent torque (M), where the changeover curve (1,2,3) is modified according to the result of the classification.
3. Method for the selection of the operating mode for an internal combustion engine operated in a user-dependent fashion which can be operated in different operating modes and drives a controllable gearbox (7), where the rotational speed dependent maximum torque and the rotational speed dependent fuel consumption of the internal combustion engine (6) are different in each of the operating modes, in which method the torque requested by the user is determined, - the operating mode is selected in such a way and the gearbox (7) setting is controlled such that the requested torque can be produced and the fuel consumption of the internal combustion engine (6) is minimised.
4. Method in accordance with Claim 3, characterised in that in the case of a gearbox (7) which is adjustable between individual stages, a switch in operating mode is synchronised with a switch in gearbox stage.
5. Method in accordance with one of the above claims, characterised in that the operating modes include lambda- I -regulated operation, homogeneous-lean operation or layered-lean operation.
6. Method in accordance with Claim I and one of the above claims in conjunction with Claim 3 for an internal combustion engine whose load control is performed in the layered-lean operating mode without throttlevalve actuation, characterised in that the internal combustion engine is operated, through suitable choice of the gearbox setting, in the layered-lean operating mode for as long as the requested torque can be produced and the increased fuel consumption resulting from throttle-valve losses in the other operating modes would be greater than the increased fuel consumption resulting from the increase in rotational speed which is necessary in order to produce the requested torque.
16 7. Control system for an internal combustion engine (6) operated in a user-dependent fashion which can be operated in different operating modes and drives a controllable gearbox (7), which control system contains: - a gearbox control unit (4) which sets a reduction in the gearbox (7), - an operations control unit (5) which places the internal combustion engine (6) into the relevant operating mode and implements load control for the internal combustion engine (6), - a communications line (17, 18) between gearbox control unit (4) and operations control unit (5), where - the gearbox control unit (4) contains a classification unit (19, 20) which generates a classification signal dependent on the user behaviour and/or the operating situation, which signal is fed to a gearbox setting unit (21, 22) which, dependent on this signal and on a similarly fed torque request signal generated by the operations control unit (5), effects the setting of the reduction in the gearbox (7), and - the operations control unit (5) which generates the torque request signal dependent on a user signal and, dependent on this and on the similarly fed classification signal, effects operating mode selection and load control for the internal combustion engine (6).
8. Control system in accordance with Claim 7 for an internal combustion engine (6) which can be operated in the operating modes lambdaI-regulated operation, homogeneous-lean operation or layered-lean operation, where the rotational speed dependent maximum torque and the rotational speed dependent fuel consumption of the internal combustion engine (6) are different in each of the operating modes and the load control 17 for the internal combustion engine (6) is performed in the layered-lean operating mode without throttle-valve actuation, characterised in that the operations control unit (5) controls a throttle valve located in the intake section of the internal combustion engine and a fuel injection device which provides fuel to the internal combustion engine in such a way, and prescribes a reduction to the gearbox control unit (4) by way of the communications line (17) such that the internal combustion engine (6) runs in the layered-lean operating mode for as long as a requested torque can be produced and the increased fuel consumption resulting from throttle-valve losses in the other operating modes would be greater than the increased fuel consumption resulting from the increase in rotational speed which is necessary in order to produce the requested torque.
9. Control system in accordance with one of the Claims 7 or 8, characterised by a synchronisation line (25) over which the operations control unit (5) and the gearbox control unit (4) exchange suitable signals in order to synchronise gearbox stage changeovers with switches in operating mode in the case of a gearbox which is adjustable in stages (7).