EP1184553B1 - Method and apparatus to operate an internal combustion engine with direct injection - Google Patents

Description

The invention relates to a method for operating a direct-injection internal combustion engine of a motor vehicle, wherein the internal combustion engine is operated in at least a first and a second operating mode. In this case, a moment of the internal combustion engine in the first operating mode substantially depends on a throttle position. In the second mode, the internal combustion engine is operated almost unthrottled. At least on the basis of an accelerator pedal position of the motor vehicle, a driver's desired torque of the internal combustion engine requested by the driver of the motor vehicle is determined. The invention also relates to a corresponding internal combustion engine of a motor vehicle, a corresponding control device for an internal combustion engine, a corresponding computer program with program code means and a corresponding computer program product with program code means.

State of the art

From DE 41 41 947 A1 a control system for a drive unit in a vehicle is known. At this known device, a desired value for the output torque of the drive train of a vehicle is formed at least depending on the driver's request, which is converted into a translation of an operating unit and a target value for the output from a drive unit of the vehicle torque. This desired value is fed to a further device which, taking into account variables affecting the torque, provides a torque corresponding to the predetermined desired value by setting the performance parameters of the drive unit. It is provided, inter alia, the torque requirement in addition to consumers, to whose operation the drive unit has to apply a certain torque such. As air conditioning, power steering, etc., to take into account the loss moment of the drive unit by means of maps and the torque correction of an idle controller.

DE 196 19 324 A1 discloses a method and a device for controlling a drive unit of a vehicle. Here, a desired value for a torque to be generated by the drive unit is derived from the degree of actuation of a control element. In this case, the derived from the degree of actuation target torque is related to a predetermined maximum and a predetermined minimum torque. The predetermined maximum and the predetermined minimum torque are each currently taken from speed-dependent maps and fed to an interpolation unit. Depending on the operation of the accelerator pedal and the current engine speed, a torque request of the driver of the motor vehicle is taken from another map and also fed to the interpolation unit. The interpolation unit determines, based on the torque request of the driver and the maximum and the minimum torque as output variable, a driver setpoint torque.

Modern direct-injection internal combustion engines in motor vehicles can be operated in different operating modes, wherein the torque generated by the engine not only, as in an internal combustion engine according to DE 196 19 324 A1, is dependent on the adjustable by the throttle air filling of the combustion chamber, but in certain modes the torque of the internal combustion engine is determined by the injected amount of fuel. Due to this different type of torque dependence in the various operating modes, the implementation of an accelerator pedal actuation by the driver of the motor vehicle into a corresponding desired torque of the driver of the motor vehicle is made more difficult.

task

It is therefore the object of the present invention to provide a method and a device which in each case reliably determines from the accelerator pedal setting a driver's desired torque of the internal combustion engine requested by the driver of the motor vehicle. This object is achieved with the features of the independent claims. Advantageous developments emerge from the subclaims.

Advantages of the invention

A method of operating a direct injection internal combustion engine of a motor vehicle, wherein the internal combustion engine is operated in at least a first and a second mode, wherein a torque of the internal combustion engine in the first mode substantially depends on a throttle position, wherein the Internal combustion engine is operated virtually unthrottled in the second mode, wherein at least on the basis of an accelerator pedal position of the motor vehicle requested by the driver of the motor vehicle driver's desired torque of the engine is further developed over the prior art in that when determining the driver's desired torque at least one moment difference from current torque losses and minimum torque losses. By this development of the invention over the prior art is achieved that in each mode, the same accelerator pedal position is converted into the same driver's desired torque. As a result, in particular a jerk when switching between the modes is avoided. A switchover from the second to the first operating mode can take place, for example, in order to initiate a regeneration of a storage catalytic converter. After regeneration would be transferred with unchanged accelerator pedal position back to the second mode.

Advantageous developments provide that the current torque losses take into account at least throttle losses and friction losses in the current operating mode, that the minimum torque losses are determined at least taking into account a minimum pressure difference of ambient pressure and intake manifold pressure and that the driver's desired torque is determined as an internal torque of the internal combustion engine. These refinements of the invention ensure an exact implementation of the method according to the invention, so that the determination of the driver's desired torque takes place exactly in each operating state.

A development of the method according to the invention provides that the minimum torque losses as a function of the speed of the internal combustion engine and the minimum pressure difference from ambient pressure and intake manifold pressure are taken from an applicable map or that a minimum engine torque is determined, which takes into account at least the sum of minimum torque losses and other torque losses, the further torque losses take into account at least the torque losses by ancillaries. This development according to the invention makes it possible to determine the minimum torque losses in a particularly simple manner.

A preferred development provides that a maximum engine torque is determined which is independent of the current operating mode. Through this development can be dispensed with the separate determination of the maximum torque in all modes, resulting in advantages in terms of storage space and speed of the control unit in the motor vehicle.

A preferred embodiment provides that a relative driver's request and / or an absolute driver's request is formed at least on the basis of the accelerator pedal position and an engine speed.

The preferred development provides that the driver's desired torque is determined either (relative driver's request) from the sum of the minimum engine torque, the torque difference and the product of relative driver's request and the difference of maximum engine torque and minimum engine torque or or (absolute driver's request) from the Sum of the minimum engine torque, the torque difference and absolute driver's request is determined.

A direct injection internal combustion engine of a motor vehicle, the at least in a first and a second mode is operable, wherein a moment of the internal combustion engine in the first mode substantially depends on a throttle position, wherein the internal combustion engine in the second mode is almost unthrottled operable, with an accelerator pedal,
with means to determine at least on the basis of an accelerator pedal position requested by the driver of the motor vehicle driver's desired torque of the internal combustion engine is further developed over the prior art that means are available to determine at least a torque difference from current torque losses and minimum torque losses in the determination of the driver's desired torque consider. The internal combustion engine according to the invention offers the advantages compared to the prior art of the methods described above.

Of particular importance is the realization of the method according to the invention in the form of a control device for an internal combustion engine, in particular of a motor vehicle. In this case, means for carrying out the steps of the method described above are provided.

Of particular importance are also the implementations in the form of a computer program with program code means and in the form of a computer program product with program code means. The computer program according to the invention has program code means for carrying out all steps of the method according to the invention when the program is executed on a computer, in particular a control unit for an internal combustion engine of a motor vehicle. In this case, the invention is thus realized by a program stored in the control unit, so that this control unit provided with the program represents in the same way the invention as the method to whose execution the program is suitable. The invention Computer program product has program code means which are stored on a computer-readable data carrier in order to carry out the method according to the invention when the program product is executed on a computer, in particular a control unit for an internal combustion engine of a motor vehicle. In this case, therefore, the invention is realized by a data carrier, so that the inventive method can be performed when the program product or the data carrier is integrated into a control device for an internal combustion engine, in particular a motor vehicle. As a data carrier or as a computer program product, in particular an electrical storage medium can be used, for example a read-only memory (ROM), an EPROM or even an electrical non-volatile memory such as a CD-ROM or DVD.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the following figures. All described or illustrated features, alone or in any combination form the subject of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or their representation in the drawing.

Description of exemplary embodiments

FIG. 1

shows an internal combustion engine according to the invention,

FIG. 2

shows an overview of the torques in the drive train of a motor vehicle,

FIG. 3

shows a first embodiment of the method according to the invention and

FIG. 4

shows a second embodiment of the method according to the invention.

1 shows an internal combustion engine 1 is shown, in which a piston 2 in a cylinder 3 back and forth. The cylinder 3 is provided with a combustion chamber 4, to which via valves 5, an intake pipe 6 and an exhaust pipe 7 are connected. Furthermore, an injection valve 8 that can be controlled with a signal TI and a spark plug 9 that can be activated with a signal ZW are connected to the combustion chamber 4. The signals TI and ZW are in this case transmitted from a control unit 16 to the injection valve 8 and the spark plug 9.

The intake pipe 6 is provided with an air mass sensor 10 and the exhaust pipe 7 with a lambda sensor 11. The air mass sensor 10 measures the air mass of the fresh air supplied to the intake pipe 6 and generates a signal LM in response thereto. The lambda sensor 11 measures the oxygen content of the exhaust gas in the exhaust pipe 7 and generates a signal lambda in dependence thereon. The signals of the air mass sensor 10 and the lambda sensor 11 are supplied to the control unit 16.

In the intake manifold 6, a throttle valve 12 is housed, the rotational position is adjustable by means of a signal DK. Furthermore, the exhaust pipe 7 may be connected via a not shown here exhaust gas recirculation line with the intake pipe 6. The control of the exhaust gas recirculation can, for example, via a controllable by the control unit 16, also not shown here, the exhaust gas recirculation valve.

In a first operating mode, the homogeneous operation of the internal combustion engine 1, the throttle valve 12 is partially opened or closed depending on the desired, supplied air mass. The fuel is from the injection valve 8 is injected into the combustion chamber 4 during a suction phase caused by the piston 2. By simultaneously sucked air, the injected fuel is swirled and thus distributed in the combustion chamber 4 is substantially uniform / homogeneous. Thereafter, the fuel-air mixture is compressed during the compression phase, to then be ignited by the spark plug 9. Due to the expansion of the ignited fuel, the piston 2 is driven.

In a second mode, the shift operation of the internal combustion engine 1, the throttle valve 12 is opened wide. The fuel is injected from the injection valve 8 during a caused by the piston 2 compression phase in the combustion chamber 4. Then, the fuel is ignited with the aid of the spark plug 9, so that the piston 2 is driven in the now following working phase by the expansion of the ignited fuel.

In stratified operation as well as in homogeneous operation, a crankshaft 14 is set into rotary motion by the driven piston, over which ultimately the wheels of the motor vehicle are driven. On the crankshaft 14, a gear is arranged, the teeth of which are scanned by a directly opposite rotational speed sensor 15. The speed sensor 15 generates a signal from which the rotational speed n of the crankshaft 14 is determined and transmits this signal n to the control unit 16.

The fuel mass injected from the injection valve 8 into the combustion chamber in stratified operation and in homogeneous operation is controlled and / or regulated by the control unit 16, in particular with regard to low fuel consumption and / or low pollutant development. The inventive definition of Ignition angle ZW takes place in the control unit 16. For this purpose, the control unit 16 is provided with a microprocessor which has stored in a storage medium program code which is adapted to carry out the entire control and / or regulation of the internal combustion engine 1 according to the invention.

The control unit 16 is acted upon by input signals representing operating variables of the internal combustion engine measured by means of sensors. For example, the control unit 16 with the air mass sensor 10, the lambda sensor 11 and the speed sensor 15 is connected. Furthermore, the control unit 16 is connected to an accelerator pedal sensor 17, which generates a signal FP, which indicates the position of a driver-actuatable accelerator pedal / accelerator pedal and thus the torque requested by the driver. This moment is referred to below as the driver's desired torque. The control unit 16 generates output signals with which the behavior of the internal combustion engine 1 can be influenced by actuators in accordance with the desired control and / or regulation. For example, the control unit 16 is connected to the injection valve 8, the spark plug 9 and the throttle valve 12 and generates the signals required for their control TI, ZW and DK.

In the control unit 16, the inventive method is further implemented, which will be explained in more detail below.

FIG. 2 shows an overview of the torques in the drive train of a motor vehicle. The operating behavior of an engine 201 and thus also the torque generated by the engine depend significantly on the air mass 202, the fuel mass 203 and the ignition angle or the ignition time 204. These are the authoritative ones Influencing factors that influence the torque generated by the motor 201. Of course, there are other possibilities of influence, which will not be discussed in detail in the context of this description. The torque 205 generated by the engine 201 directly from the combustion is referred to below as the internal torque 205 of the internal combustion engine. If the charge cycle and friction losses 206 are subtracted from the inner torque 205, the actual engine torque 207 which can be tapped approximately at the crankshaft of the engine is obtained. The engine torque 207 is referred to below as indexed torque 207. Be deducted from the indexed moment 207, the torque components that must be spent on ancillaries such as generator, air compressor, etc., so there is the clutch torque 209, which is available at the clutch of the internal combustion engine. If the clutch losses 210 are subtracted from the clutch torque 209 which is available at the input of the clutch, the transmission torque 211 available at the input of the transmission is obtained. The transmission torque 211 available at the input of the transmission is increased again by gearbox and gearbox torque Translation losses 212 reduced to finally get the actual drive torque 213. The drive torque 213 may also be referred to as wheel torque.

The core of the method according to the invention which is described in more detail below in the context of FIGS. 3 and 4 is to determine an operator request torque of the internal combustion engine as internal torque 205 of the internal combustion engine based on an accelerator pedal position of the motor vehicle. The control unit 16 shown in FIG. 1 contains a function (moment coordinator) for requesting the information requested by the driver of the motor vehicle To coordinate driver request torque with the other present torque requirements, eg from a vehicle dynamics control, to a coordinated total torque. The coordinated total torque is thus the relevant desired torque that is to be generated by the internal combustion engine.

FIG. 3 shows a first embodiment of the method according to the invention. Here, the accelerator pedal operation is interpreted by the driver of the motor vehicle as a relative moment request. Depending on an accelerator pedal position 301 (pedal) and the current engine speed 302 (nmot), a relative driver request 304 (mrfa) is taken from an applicable map 303 (kfmrel). This relative driver request (mrfa) is supplied to a multiplication unit 305. Furthermore, the multiplication unit 305 is supplied with the difference between the maximum engine torque 306 (mimax) and the minimum engine torque 307 (mimin_min). The result of the multiplication block 305 is supplied to the addition unit 308. Here, to the output torque of the multiplication unit 305, the minimum motor torque 307 (mimin_min) is added. The result or output torque of the block 308 is supplied to an adder 309. The adder 309 is further supplied with the moment difference 310 (mdslw) according to the invention. The moment difference 310 (mdslw) results as the result of the subtraction unit 311, to which the input side the actual torque losses 312 (mds) and the minimum torque losses 313 (mds_min) are supplied. The current torque losses 312 (mds) and the minimum torque losses 313 (mds_min) are the output 317 of a map 314 (kfmds), which torque losses as a function of the speed of the internal combustion engine (nmot) and the minimum pressure difference (dpmin) from ambient pressure (pu) and intake manifold pressure (ps) contains. The map 314 is permanently supplied with the engine speed 302 (nmot). The map 314 (kfmds) is now alternately or by the shown in Figure 3 or indicated switches with the current pressure difference 315 (dp) from ambient pressure (pu) and intake manifold pressure (ps) and the minimum pressure difference 316 (dpmin) from ambient pressure (pu) and intake manifold pressure (ps) addressed. As output signal 317 of the characteristic map 314 (kfmds), the current torque losses (mds) or the minimum torque losses (mds_min) are thus alternately available, depending on the addressing of the input of the characteristic map. The output signals of the characteristic map 314 (kfmds) are buffered in a buffer, not shown in FIG. 3, so that the current torque losses 312 (mds) and the minimum torque losses 313 (mds_min) are available at the inputs of the subtraction block 311 at all times. The moment difference 310 (mdslw) according to the invention results from the difference between the instantaneous torque losses 312 (mds) and the minimum torque losses 313 (mds_min). As the output signal of the adder 309, the desired driver input torque 318 is available as internal engine torque (mifa).

As an alternative to the intermediate storage of the output signals 317 of the map 314, it may of course be provided to provide two maps corresponding to map 314, so that the determination of the current torque losses (mds) and the minimum torque losses (mds_min) can be done in parallel at any time.

The maximum engine torque (mimax) is the maximum possible internal engine torque from combustion. This maximum possible engine torque can according to the invention for all modes (both throttled, throttled as well as unthrottled operating modes) are the same.

The minimum engine torque (mimin_min) results from the sum of minimum torque losses (mds_min) and the losses by ancillaries and other consumers (mdv), where the sum of the two torque components can be provided with a scaling factor, for example, the difference of engine speed (nmot) and idle speed can result.

The current torque losses (mds) and the minimum torque losses (mds_min) each contain the torque losses due to throttling and friction.

The consequence of the determination according to the invention of the driver command torque (mifa) is that the constant clutch pedal position (pedal) when switching to a different operating mode sets the identical clutch torque for both the output and the target operating mode. This ensures that the driver of the motor vehicle feels no jolt of the motor vehicle by jumping the clutch torque.

FIG. 4 shows a further embodiment of the method according to the invention. In the context of Figure 4, and here is the difference to Figure 3, the predetermined by the driver of the motor vehicle accelerator pedal position is interpreted as an absolute driver's request.

In accordance with the accelerator pedal position 401 (pedal) and the current engine speed 402 (nmot), an absolute driver request 404 (mi_soll) is taken from an applicable map 403 (kfmabs), which is fed to an addition unit 408. The addition unit 408, the minimum engine torque 407 (mimin_min) continues to be supplied. In this case, the minimum motor torque 407 corresponds to that after 307 in FIG. 3. The result of the addition block 408 is supplied to a further addition block 409 to which the torque difference 410 (mdslw) is fed as a further input signal. The moment difference 410 can also be seen analogously to the moment difference 310 in FIG. The result of the addition block 409 is equivalent to FIG. 3 an inner driver request torque 411 (mifa).

Claims (15)

1. Method for operating a direct-injection internal combustion engine of a motor vehicle,

   - wherein the internal combustion engine is operated in at least a first operating mode and a second operating mode,

   - wherein a torque of the internal combustion engine in the first operating mode (HOM) depends essentially on a throttle valve position,

   - wherein the internal combustion engine is operated in a virtually unthrottled fashion in the second operating mode (SCH),

   - wherein a driver request torque (mifa) - requested by the driver of the motor vehicle - of the internal combustion engine is determined at least by reference to an accelerator pedal position (pedal) of the motor vehicle, characterized in that when the driver request torque (mifa) is determined at least one torque difference (mdslw) formed between current torque losses (mds) and minimum torque losses (mds_min) is taken into account.
2. Method according to Claim 1, characterized in that the current torque losses (mds) take into account at least throttle losses and friction losses in the current operating mode.
3. Method according to Claim 1, characterized in that the minimum torque losses (mds_min) are determined at least taking into account a minimum pressure difference (dpmin) formed between the ambient pressure (pu) and intake manifold pressure (ps).
4. Method according to Claim 1, characterized in that the driver request torque (mifa) is determined as an internal torque (205) of the internal combustion engine.
5. Method according to Claim 3, characterized in that the minimum torque losses (mds_min) are extracted from an applicable characteristic diagram (kfmds) as a function of the speed of the internal combustion engine (nmot) and the minimum pressure difference (dpmin) formed between the ambient pressure (pu) and intake manifold pressure (ps).
6. Method according to Claim 3, characterized in that a minimum engine torque (mimin_min) is determined which takes into account at least the sum of minimum torque losses (mds_min) and further torque losses (mdv).
7. Method according to Claim 6, characterized in that the further torque losses (mdv) take into account at least the torque losses due to secondary assemblies.
8. Method according to Claim 1, characterized in that a maximum engine torque (mimax) is determined which is independent of the current operating mode (HOM, SCH).
9. Method according to Claim 1, characterized in that a relative driver request (mrfa) and/or an absolute driver request (mi_soll) is formed at least by reference to the accelerator pedal position (pedal) and an engine speed (nmot).
10. Method according to Claims 6, 8 and 9, characterized in that the driver request torque (mifa) is determined from the sum of

    - the minimum engine torque (mimin_min),

    - the torque difference (mdslw) and

    - the product of the relative driver request (mrfa) and the difference between the maximum engine torque (mimax) and minimum engine torque (mimin_min), (mifa = mimin_min + mdslw + mrfa x (mimax-mimin_min)).
11. Method according to Claims 6, 8 and 9, characterized in that the driver request torque (mifa) is determined from the sum of

    - the minimum engine torque (mimin_min),

    - the torque difference (mdslw) and

    - absolute driver request (mi_soll),

    (mifa = mimin_min + mdslw + mi_soll).
12. Direct-injection internal combustion engine of a motor vehicle which can be operated at least in a first and a second operating mode,

    - wherein a torque of the internal combustion engine in the first operating mode (HOM) depends essentially on a throttle valve position,

    - wherein the internal combustion engine can be operated in a virtually unthrottled fashion in the second operating mode (SCH),

    - having an accelerator pedal,

    - having means for determining, at least by reference to an accelerator pedal position (pedal), a driver request torque (mifa) - requested by the driver of the motor vehicle - of the internal combustion engine, characterized in that means are provided in order to take into account, during the determination of the driver request torque (mifa), at least a torque difference (mdslw) formed between current torque losses (mds) and minimum torque losses (mds_min).
13. Control unit for an internal combustion engine, in particular of a motor vehicle, having means for carrying out the steps of the method according to at least one of Claims 1 to 11, characterized in that means are provided for taking into account, in the determination of the driver request torque (mifa), at least a torque difference (mdslw) formed between current torque losses (mds) and minimum torque losses (mds_min).
14. Computer program with program code means for carrying out all the steps of any of Claims 1 to 11 if the program is executed on a computer, in particular a control unit for an internal combustion engine.
15. Computer program product with program code means which are stored on a computer-readable data carrier for carrying out the method according to any of Claims 1 to 11 if the program product is executed on a computer, in particular a control unit for an internal combustion engine.

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