DE10218012A1 - Method and device for controlling the drive unit of a vehicle - Google Patents

Abstract

The invention relates to a method and a device (10) for controlling the drive unit (1) of a vehicle (5), which enable the driver of the vehicle (5) to specify the fuel consumption, which the vehicle (5) also does is actually observed. In the method, an operating point of the drive unit (1) is selected as a function of a specification for a fuel consumption.

Description

State of the art

The invention relates to a method and one Device for controlling the drive unit of a vehicle according to the genre of independent claims.

In motor vehicles, it is common for the driver to use a appropriate display means to give feedback on how his current driving style on fuel consumption effect. To do this, either the current consumption, for example in liters per hundred kilometers, or one correspondingly, over a certain period of time in the Past averaged consumption value is displayed.

The current consumption does indeed provide during journeys constant speed is a good guideline for However, the displayed values do not allow dynamic processes Conclusion on the actual consumption. You can for example when accelerating from a standstill Vehicle very high or often no longer at all displayable measuring range. The average consumption leaves again no conclusion about the current consumption, because the displayed value refers to the past.

Furthermore, devices are known that the driver in Vehicles with manual transmission or partially automated transmissions Show suggestions, one for the Consumption to choose cheaper gear. Such facilities, the driver when choosing a cheaper gear or Operating point are advantageous, but do not allow quantifiable conclusions as to which Savings from the proposed measures actually be achieved.

Advantages of the invention

The inventive method and the inventive Device for controlling the drive unit of a vehicle with the features of the independent claims in contrast, the advantage that a working point of the drive unit depending on a default size for one Fuel consumption is selected. This way it is possible to get a To make specification about fuel consumption by the Drive unit of the vehicle is actually observed becomes. This frees the driver from being relatively inaccurate or little meaningful ads to watch and about the entire discipline to be through Driving behavior does not increase the displayed fuel consumption exceed.

By the measures listed in the subclaims advantageous further developments and improvements of Method and device for controlling the drive unit a vehicle possible according to the independent claims.

It is particularly advantageous if the working point the drive unit is selected so that the default size for the fuel consumption on average over time is exceeded. This way it will be the driver allows a momentary in certain driving situation Exceeding the default size for fuel consumption realize, the short-term additional consumption by a Falling below the specified size for fuel consumption is compensated for in other driving situations. On this way the contradicting desires on which saving costs and fuel on one side, and on the other other side to experience dynamic driving pleasure, bill carried.

It is particularly advantageous if the default size for the Fuel consumption of a default size for the Fuel price per driving distance is derived. In this case the operating point of the drive unit can be selected that specified fuel costs are met.

drawing

Embodiments of the invention are in the drawing shown and in the description below explained. Show it

Fig. 1 is a block diagram for a first embodiment with a device for controlling the drive unit of a vehicle,

Fig. 2 is a flowchart for describing the method according to the invention,

Fig. 3 is a graph showing the specific fuel consumption as a function of an operating point of the drive unit,

Fig. 4 is a graph showing the specific fuel consumption and the power as a function of the operating point,

Fig. 5 is a diagram showing an efficiency of the drive unit in dependence of the vehicle speed,

Fig. 6 is a diagram showing the minimum consumption for different engine powers and

Fig. 7 is a block diagram for a second embodiment of the inventive apparatus for controlling the drive unit of a vehicle.

Description of the embodiments

In Fig. 1, 5 denotes a vehicle. The vehicle 5 comprises a drive unit 1 . The drive unit 1 is controlled by a device 10 of the vehicle 5 . The device 10 is therefore referred to below as a control unit. A suitable operating point is set by the control unit 10 for the respective operating state of the drive unit 1 as a function of the specified variables. Such default values include, for example, a driver's desired torque that can be derived from an accelerator pedal position. Further predefined variables that predefine a torque to be set by the drive unit 1 can be predefined, for example, by a traction control system (not shown in FIG. 1), an anti-lock braking system, or the like. A block 25 is shown in FIG. 1, which specifies a target torque to be set by the drive unit 1 as a representative of all possible sources of torque. This predetermined target torque is received by first means 30 of the control unit 10 . The control unit 10 further comprises second means 20 , which are connected to an input unit 35 and receive a predefined quantity for a fuel consumption. The driver of the vehicle 5 can enter this default size on the input unit 35, for example by means of a keyboard or by voice input. The first means 30 and the second means 20 are connected to third means 15 of the control unit 10 . The third means 15 receive the predetermined target torque from the first means 30 and the predetermined variable for the fuel consumption from the second means 20 . The third means 15 determine and control a working point of the drive unit 1 from the predetermined setpoint torque and the default size for the fuel consumption and possibly further operating parameters or operating parameters of the drive unit 1 supplied to the control unit 10, such as the current driving speed of the vehicle, oil pressure, engine temperature or also ambient pressure Drive unit 1 for setting this operating point accordingly. In FIG. 1, 40 denotes a block, which represents the acquisition of any further operating variables. This block 40 is also connected to the control unit 10 . The control unit 10 comprises fourth means 45 , which receive the further operating parameters from the block 40 and also feed them to the third means 15 .

The operating point of the drive unit 1 can be set in various ways using different manipulated variables, such as, for example, the ignition angle setting, the filling, the injection time and / or the like. This can be implemented by suitable coordination by the third means 15 . According to the invention, it is now a matter of the driver of the vehicle 5 entering the default size for the fuel consumption on the input unit 35 and thus specifying the maximum fuel consumption that he wants to allow. The choice of the operating point of the drive unit 1 is made by the control unit 10 or the third means 15 in such a way that the specified fuel consumption is actually maintained. For this purpose, both the motor and the transmission of the drive unit 1 can be suitably controlled by the third means 15 . For this purpose, the third means 15 can comprise an engine control and a transmission control. The method according to the invention is therefore particularly suitable for vehicles with automatic transmissions, automatic manual transmissions or continuously variable automatic transmissions or the like.

Based on the specification of the fuel consumption, it can happen that the third means 15 select an operating point of the drive unit 1 at which the dynamics and the power of the vehicle 5 are restricted compared to the maximum dynamics and power that can be provided by the drive unit 1 .

The current fuel consumption of the drive unit 1 and thus of the vehicle 5 can be determined for a known operating point of the drive unit 1 using a consumption map of the drive unit 1 . In the following, it should be assumed as an example that the operating point is defined by an engine speed n and a torque T to be output by the drive unit 1 . In Fig. 3, the fuel consumption map is n as a function of engine speed and to be discharged from the drive unit 1 torque T shown. The engine speed n is shown on the abscissa in revolutions U per minute, whereas the ordinate shows the torque T to be output by the drive unit 1 in Nm. Registered in the fuel consumption map of FIG. 3 then isolines same specific consumption Ver are in g / kWh. The specific fuel consumption Ver for each operating point can thus be taken from the consumption map based on the engine speed n and the torque T to be output by the drive unit 1 .

The current engine power P in kW is calculated as:

P = nTπ / 30,000 (1)

Lines of constant engine power P can be shown in the form of hyperbolas superimposed on the consumption map of the drive unit 1 , as shown in FIG. 4. FIG. 4 shows the consumption map known from FIG. 3, to which the isolines of the power P in kW are additionally superimposed.

With the specific density G of the fuel in g / l and the vehicle speed V in km / h, the total consumption Ver_ges in l / (100 km) can be determined:

Ver_ges = P.Ver.100 / (DV) (2)

For journeys at constant speed on the plane, an assignment of the engine power P to the vehicle speed V can be specified with additional simplifications:

P = Fw.V.Eta / 3600 (3)

With

Fw = Broll.mg + 0.0386.Bluft.cw.AVV (4)

in which
Fw the driving resistance force in N,
Eta the efficiency of the drive unit 1 ,
Broll the rolling resistance coefficient,
m is the vehicle mass in kg
g is the acceleration due to gravity in m / (ss),
Blows the air density in kg / (mmm)
cw is the drag coefficient and
A is the cross-sectional area of the vehicle 5 in mm
is.

The efficiency Eta of the drive unit 1 can be specified in a simplified manner as a function of the vehicle speed V according to the diagram in FIG. 5, the vehicle speed V in km / h being plotted on the abscissa and the efficiency Eta of the drive unit 1 being plotted on the ordinate. The example of FIG. 5 shows that the maximum efficiency Eta of the drive unit 1 is approximately in the range of 90 km / h and approximately 0.9.

As a result, a minimum fuel consumption can be assigned to each vehicle speed V under the given conditions, ie driving in the plane with a constant vehicle speed V, if the operating point of the drive unit 1 is selected at which the specific fuel consumption Ver for the necessary engine power P is lowest.

An example of the minimum fuel consumption as a function of the vehicle speed V is given in Table 1. Table 1

The line of the minimum fuel consumption for different engine outputs P is shown for clarification according to FIG. 6 superimposed on the consumption map known from FIG. 3. Here, in Fig. 6 again, the contour lines for the specific fuel consumption Ver as shown in FIG. 3 and FIG. 4, as well as the contour lines for the engine power P as shown in Fig. 4, is shown. In addition, the line of minimum consumption for the various engine powers P is shown in FIG. 6 and is identified by the reference symbol 50 .

As described according to the invention, the third means 15 select an operating point of the drive unit 1 as a function of the predefined size for the fuel consumption. In the following, several options are presented as to how this selection of the operating point of the drive unit 1 can be implemented as a function of the specified size for the fuel consumption. A first possibility is shown in the flow chart according to FIG. 2. At a first program point 100, the default value for the fuel consumption is received in the control unit 10 by the second means 20 . The default size for the fuel consumption is then forwarded to the third means 15 of the control unit 10 . The program then branches to a program point 105 . At program point 105 , the fourth means 45 receive the current driving speed V of the vehicle 5 as an operating parameter from the block 40 and also pass it on to the third means 15 . The program then branches to a program point 110 . At program point 110 , the third means 15 for the determined driving speed V select the working point with the minimum specific consumption with the aid of the consumption map according to FIG. 6, which can be stored in the third means 15 . For the special case of driving in the plane with a constant driving speed V, the working point with minimal consumption can also be found in table 1 or a more extensive table with a larger number of different driving speed values, which can also be stored in the third means 15 . The program then branches to a program point 115 . At program point 115 , the third means 15 check whether this minimum consumption is less than the default size for the fuel consumption. If this is the case, the program is exited, otherwise the program branches to a program point 120 . At program point 120 , the third means 15 cause the drive unit 1 to reduce the driving speed V, for example by decrementing a predetermined value, by influencing suitable manipulated variables of the drive unit 1 , such as, for example, ignition angle, filling, injection time or the like. The program then branches back to program point 105 .

In the procedure described, an operating point is ultimately sought at which the specified size for the fuel consumption is not exceeded. This can be realized in particular for an operating state of the drive unit 1 in which the vehicle 5 is to travel in the plane at a constant driving speed V. This operating state is referred to here as the first operating state.

In the procedure described for the first operating state, the corresponding operating point on the line 50 of the minimum consumption is therefore selected, with a limitation being carried out in such a way that no operating point is selected which requires a higher fuel consumption than the specified size for the fuel consumption.

It is essential for the acceptance of the setting according to the invention of the operating point of the drive unit 1 as a function of the default size for the fuel consumption that, in certain driving situations, it should be possible to temporarily exceed the default size for the fuel consumption. The short-term additional consumption can then be compensated for by falling below the specified size for the fuel consumption in other situations or operating states of the drive unit. Operating conditions such as driving on the freeway, driving with the cruise control switched on, deceleration phases or driving downhill are particularly suitable when the fuel consumption falls below the specified size. The detection of such operating states is known, for example, from DE 199 63 749 A1 and from DE 100 10 764. The detection of such situations can also be supplied to the third means 15 for evaluation via the block 40 and the fourth means 45 .

Situations where over fuel consumption the default size for fuel consumption For example, trips in the City, overtaking, cold starts or safety critical Conditions such as kick down.

An operating state in which the specified size for the fuel consumption is undershot is referred to below as the second operating state of the drive unit 1 . An operating state in which additional consumption is permitted in comparison with the stipulated quantity for fuel consumption is referred to below as the third operating state.

It can now be provided that the third means 15 select the operating point of the drive unit 1 in such a way that the specified size for the fuel consumption is not exceeded on average over time. In this way, driving situations in the third operating state, which are characterized by a short-term additional consumption, can be compensated for in terms of fuel consumption by driving situations in the second operating state, which are characterized by the fuel consumption falling below the specified size.

The contradicting wishes of the driver, on the one hand Saving costs and fuel on the arideren Side experiencing dynamic driving pleasure is this way Taken into account.

In addition, it can be provided to compile statistics on the driving style of the driver and to store them in the third means 15 or in a memory assigned to the third means 15 . If it turns out, for example, that a driver travels most of his driving performance at low speed on the freeway, this driver can be permitted a high additional consumption for a dynamic driving style in the city because he can compensate for this on the freeway. The default size for fuel consumption is then not necessarily adhered to on each individual trip by the third means 15 or the drive unit 1 controlled thereby, but on the average of its mileage.

A driving force for reducing the Fuel consumption is in addition to the legal regulations and the Environmental protection more and more the fuel price. It can therefore be provided that the presented invention Procedures can also be implemented in the form that instead the default size for fuel consumption Specified size for the fuel price per driving distance and from this the default size for fuel consumption is derived.

In a second embodiment according to FIG. 7, the same reference numerals designate the same elements as in FIG. 1. The structure of the second embodiment according to FIG. 7 corresponds to the structure of the first embodiment according to FIG. 1 with the difference that instead of the second means 20 fifth ones Means 55 are provided in the device 10 , which receive the default size for the fuel price per driving distance from the input unit 35 instead of the default size for the fuel consumption. In the second exemplary embodiment according to FIG. 7, the driver enters the default value for the fuel price per driving distance on the input unit 35 . It can now be provided that the fifth means 55 convert the default size for the fuel price per driving distance into the default size for the fuel consumption and forward the default size for the fuel consumption to the third means 15 . However, it can also be provided that the fifth means 55 forward the received specification for the fuel price per driving distance to the third means 15 , and that the third means 15 derive the specification for the fuel consumption based on the specification for the fuel price per driving distance. For this purpose, it is then additionally required that the fuel price per liter is known in the means which carry out the conversion from the standard value for the fuel price per driving distance to the standard value for the fuel consumption. This can also be entered by the driver via the input unit 35 and stored in a memory assigned to the fifth means 55 or the third means 15 , depending on which of the two means 15 , 20 carries out the conversion.

Claims (9)

1. A method for controlling the drive unit ( 1 ) of a vehicle ( 5 ), characterized in that an operating point of the drive unit ( 1 ) is selected as a function of a predefined size for fuel consumption. 2. The method according to claim 1, characterized in that at least a first operating state of the drive unit ( 1 ) is provided, in which the operating point is selected so that the predetermined size for the fuel consumption is not exceeded. 3. The method according to claim 1 or 2, characterized in that at least a second operating state is provided, in which the operating point of the drive unit ( 1 ) is selected so that the specified size for the fuel consumption is not reached. 4. The method according to any one of the preceding claims, characterized in that the operating point of the drive unit ( 1 ) is selected so that the specified size for the fuel consumption is not exceeded on average over time. 5. The method according to any one of the preceding claims, characterized characterized that the default size for the Fuel consumption of a default size for the fuel price is derived per driving distance. 6. The method according to any one of the preceding claims, characterized in that the operating point is set by an engine speed and a torque to be output by the drive unit ( 1 ). 7. Device ( 10 ) for controlling the drive unit ( 1 ) of a vehicle ( 5 ), characterized in that means ( 15 ) for selecting a working point of the drive unit are provided as a function of a predefined size for fuel consumption. 8. The device according to claim 7, characterized in that means ( 20 ) are provided for receiving the default size for fuel consumption. 9. The device according to claim 7 or 8, characterized in that means ( 15 , 55 ) are provided for receiving a default size for the fuel price per driving distance and its conversion into the default size for fuel consumption.