U.S. patent application number 09/725344 was filed with the patent office on 2001-05-31 for method and device for controlling a prime mover.
Invention is credited to Frohlich, Johann, Zhang, Hong.
Application Number | 20010002090 09/725344 |
Document ID | / |
Family ID | 7869421 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002090 |
Kind Code |
A1 |
Frohlich, Johann ; et
al. |
May 31, 2001 |
Method and device for controlling a prime mover
Abstract
A prime mover has an internal combustion engine and a motor
generator. A setpoint of a torque depends on a variable
representing the wish of an operator of the prime mover and on
operating variables of the internal combustion engine. Actuating
signals for actuators of the internal combustion engine depend on
the setpoint of the indicated torque. An actuating signal for the
motor generator which is arranged on the output shaft of the
internal combustion engine depends on the setpoint of the
torque.
Inventors: |
Frohlich, Johann; (Landshut,
DE) ; Zhang, Hong; (Tegernheim, DE) |
Correspondence
Address: |
Lerner and Greenberg, P.A.
P.O. Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7869421 |
Appl. No.: |
09/725344 |
Filed: |
November 29, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09725344 |
Nov 29, 2000 |
|
|
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PCT/DE99/02420 |
Aug 19, 1998 |
|
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Current U.S.
Class: |
290/40R |
Current CPC
Class: |
B60W 2050/0042 20130101;
B60W 2710/0616 20130101; B60W 2710/083 20130101; F02D 2200/1006
20130101; B60W 20/00 20130101; Y02T 10/62 20130101; Y02T 10/40
20130101; B60W 20/40 20130101; B60W 10/08 20130101; B60L 2240/423
20130101; F02D 41/28 20130101; B60K 6/485 20130101; B60W 2510/0628
20130101; Y02T 10/64 20130101; B60W 10/06 20130101; B60W 2050/0052
20130101; B60W 2710/0666 20130101 |
Class at
Publication: |
290/40.00R |
International
Class: |
F02N 011/06; H02P
009/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 1998 |
DE |
198 24 253.0 |
Claims
We claim:
1. A method of controlling a prime mover having an internal
combustion engine, which comprises: determining a setpoint of a
torque in dependence on a variable representing a driver's wish and
operating variables of an internal combustion engine; defining
actuating signals for actuators of the internal combustion engine
in dependence on the setpoint of the torque; determining an
estimated value of a maximum or minimum torque that can be set via
the actuators of the internal combustion engine within a predefined
time period; and defining an actuating signal for a motor generator
connected to an output shaft of the internal combustion engine in
dependence on the setpoint of the torque and the estimated value of
the maximum or minimum torque.
2. The method according to claim 1, wherein the actuator is one of
a spark plug and an injection valve, and the method further
comprises determining an estimated value of the actual motor
generator torque, and setting an actuating signal for the actuator
in dependence on the setpoint of the torque and the estimated value
of the actual motor generator torque.
3. The method according to claim 1, wherein the actuating signal
for the motor generator depends on the difference between the
setpoint of the torque and the estimated value of the maximum or
minimum torque.
4. The method according to claim 1, which comprises operating the
motor generator as a motor if the estimated value of the maximum
torque is less than the setpoint of the torque.
5. The method according to claim 1, which comprises operating the
motor generator as a generator if the estimated value of the
minimum torque is greater than the setpoint of the torque.
6. The method according to claim 1, which comprises operating the
motor generator as a motor if a difference between the setpoint of
the torque and the estimated value of the maximum torque is greater
than a predefined threshold value.
7. The method according to claim 1, which comprises defining the
predefined time period by a time period of one crank shaft
segment.
8. A device for controlling a prime mover having an internal
combustion engine, comprising: a device for determining a setpoint
of a torque in dependence on a variable representing a wish of a
driver and operating variables of the internal combustion engine; a
device for generating actuating signals for actuators of the
internal combustion engine in dependence on the setpoint of the
torque; a device for determining an estimated value of a maximum or
minimum torque that can be set via the actuators of the internal
combustion engine within a predefined time period; and a device for
generating an actuating signal for a motor generator, arranged on
an output shaft of the internal combustion engine, in dependence on
the setpoint of the torque and the estimated value of the maximum
or minimum torque.
9. A device for controlling a prime mover having an internal
combustion engine and a motor generator arranged on an output shaft
of the internal combustion engine, comprising: a torque setpoint
controller programmed to determine a setpoint of a torque in
dependence on a variable representing a driver's wish and operating
variables of the internal combustion engine; an actuator controller
programmed to generate actuating signals for actuators of the
internal combustion engine in dependence on the setpoint of the
torque; an estimator programmed to determine an estimated value of
a maximum or minimum torque that can be set via the actuators of
the internal combustion engine within a predefined time period; and
a motor generator signal generator programmed to generate an
actuating signal for a motor generator on an output shaft of the
internal combustion engine in dependence on the setpoint of the
torque and the estimated value of the maximum or minimum torque.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of copending international
application PCT/DE99/02420, filed Aug. 19, 1998, which designated
the United States.
[0002] The invention relates to a method of controlling a prime
mover which includes an internal combustion engine and wherein a
setpoint of a torque depends on a variable representing a driver's
wish and operating variables of the internal combustion engine,
actuating signals for actuators of the internal combustion engine
depend on the setpoint of the torque, and an actuating signal for a
motor generator which is arranged on the output shaft of the
internal combustion engine depends on the setpoint of the torque.
The invention also pertains to a device for controlling a prime
mover which includes an internal combustion engine, in which there
is provided a device for determining a setpoint of a torque on the
basis of a variable representing the driver's wish and operating
variables of the internal combustion engine, a device for
generating actuating signals for actuators of the internal
combustion engine on the basis of the setpoint of the torque, and a
device for generating an actuating signal for a motor generator on
the output shaft of the internal combustion engine, specifically on
the basis of the setpoint of the torque.
[0003] A method of controlling an internal combustion engine is
disclosed in the commonly assigned, copending patent application
Ser. No. 09/160,878 (published as WO 97/36762 and German DE 196 12
455 A1). A setpoint of a torque is determined on the basis of the
position of a gas pedal, the rotational speed and further
operational variables such as the air mass flow, the coolant
temperature and the oil temperature. Depending on the desired
torque, a drive signal for a throttle valve actuator is determined.
The torque to be set via the air mass flow is determined by taking
into account the desired torque and the derivative-action values of
the torque, which are required by functions for controlling the
internal combustion engine, such as traction control, engine speed
limitation, vehicle speed limitation and a catalytic converter
heating function. In addition, a setpoint of the torque, which is
to be adjusted rapidly, depends on the desired torque and torque
requirements of the further functions for controlling the internal
combustion engine. An actuating signal for a spark plug depends on
the setpoint of the torque. By changing the ignition angle it is
possible for the torque actually produced in one cylinder of the
internal combustion engine to be changed within one crank shaft
segment. The time period of a crank shaft segment is defined, for
example, by the time interval between the ignition cycles of two
cylinders which are adjacent in the ignition sequence.
[0004] Because of the inertia of the intake tract, the setpoint of
the torque to be set via the air mass flow can be set only slowly.
If the torque which is actually to be generated by the internal
combustion engine has excessively high dynamics, then the
derivative-action values must be chosen to be high in order to be
able to set the torque with a high quality. However, this results
in high exhaust gas emissions from the internal combustion engine
and high fuel consumption.
SUMMARY OF THE INVENTION
[0005] The object of the invention is to provide a device and a
method for controlling a prime mover which overcome the above-noted
deficiencies and disadvantages of the prior art devices and methods
of this kind, and which ensure convenient and simultaneously
low-emission operation of the internal combustion engine with a
high efficiency of the prime mover.
[0006] With the above and other objects in view there is provided,
in accordance with the invention, a method of controlling a prime
mover having an internal combustion engine, which comprises:
[0007] determining a setpoint of a torque in dependence on a
variable representing a driver's wish and operating variables of an
internal combustion engine;
[0008] defining actuating signals for actuators of the internal
combustion engine in dependence on the setpoint of the torque;
[0009] determining an estimated value of a maximum or minimum
torque that can be set via the actuators of the internal combustion
engine within a predefined time period; and
[0010] defining an actuating signal for a motor generator connected
to an output shaft of the internal combustion engine in dependence
on the setpoint of the torque and the estimated value of the
maximum or minimum torque.
[0011] In accordance with an added feature of the invention, the
actuator is a spark plug or an injection valve, and the method
further comprises determining an estimated value of the actual
motor generator torque, and setting an actuating signal for the
actuator in dependence on the setpoint of the torque and the
estimated value of the actual motor generator torque.
[0012] In accordance with an additional feature of the invention,
the actuating signal for the motor generator depends on the
difference between the setpoint of the torque and the estimated
value of the maximum or minimum torque.
[0013] In accordance with another feature of the invention, the
motor generator as operated as a motor if the estimated value of
the maximum torque is less than the setpoint of the torque. The
motor generator is operated as a generator if the estimated value
of the minimum torque is greater than the setpoint of the torque.
Furthermore, the motor generator is operated as a motor if the
difference between the setpoint of the torque and the estimated
value of the maximum torque is greater than a predefined threshold
value.
[0014] In accordance with a concomitant feature of the invention,
the predefined time period is defined as the time period of one
crank shaft segment.
[0015] With the above and other objects in view there is also
provided, in accordance with the invention, a device for
controlling a prime mover having an internal combustion engine,
comprising:
[0016] a device for determining a setpoint of a torque in
dependence on a variable representing a wish of a driver and
operating variables of the internal combustion engine;
[0017] a device for generating actuating signals for actuators of
the internal combustion engine in dependence on the setpoint of the
torque;
[0018] a device for determining an estimated value of a maximum or
minimum torque that can be set via the actuators of the internal
combustion engine within a predefined time period; and
[0019] a device for generating an actuating signal for a motor
generator, arranged on an output shaft of the internal combustion
engine, in dependence on the setpoint of the torque and the
estimated value of the maximum or minimum torque.
[0020] In summary, the objects of the invention are satisfied with
the novel method and device which is distinguished by the fact that
an actuating signal for a motor generator which is arranged on the
output shaft of the internal combustion engine is determined as a
function of the setpoint of the torque. The motor generator has a
response time which is considerably lower than the time period
until a step in the setpoint of the torque is adjusted via the air
mass flow. It is therefore possible for the derivative-action value
in the torque to be adjusted via the air mass flow to be chosen to
be lower without, in the process, having to accept penalties in
terms of convenience.
[0021] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0022] Although the invention is illustrated and described herein
as embodied in a method and device for controlling a prime mover,
it is nevertheless not intended to be limited to the details shown,
since various modifications and structural changes may be made
therein without departing from the spirit of the invention and
within the scope and range of equivalents of the claims.
[0023] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic diagram of a prime mover with an
internal combustion engine and a motor generator;
[0025] FIGS. 2A, 2B, and 2C are schematic block diagrams of the
control system according to the invention;
[0026] FIG. 3 is a graph plotting signal waveforms over time t;
and
[0027] FIG. 4 is a similar graph plotting signal waveforms over
time.
[0028] Identical and functionally equivalent elements are
identified with the same reference symbols throughout the
figures.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Referring now to the figures of the drawing in detail and
first, particularly, to FIG. 1 thereof, there is seen a prime mover
with an internal combustion engine. The internal combustion engine
has an intake tract 1 with a throttle valve 10 and an engine block
2, which has a cylinder 20 and a crank shaft 23. A piston 21 and a
connecting rod 22 are associated with the cylinder 20. The
connecting rod 22 is connected between the piston 21 and the crank
shaft 23.
[0030] A cylinder head 3 is provided, in which a valve train is
arranged, having at least one inlet valve 30, an outlet valve 31,
and in each case a valve drive 32a associated with the inlet valve
30 and a valve drive 32b associated with the outlet valve 31.
[0031] Introduced into the intake tract 1 is an injection valve 11,
which is arranged in such a way that fuel is metered into the
intake tract 1. Alternatively, the injection valve 11 can also be
introduced into the cylinder head 3 and be arranged there in such a
way that the fuel is metered directly into the interior of the
cylinder 20. A spark plug 34 is introduced into a recess in the
cylinder head 3. The internal combustion engine is illustrated in
FIG. 1 with one cylinder. It will be understood, however, that the
engine may comprise a plurality of cylinders.
[0032] An exhaust gas tract 4 is associated with the internal
combustion engine. A motor generator 5 is provided, whose rotor is
connected to the crank shaft 23 by a force fit or power linkage.
The motor generator is preferably designed as an asynchronous
machine. However, it can also be designed as a synchronous machine
or as a DC motor. In motor operation, the crank shaft 23 is the
output shaft of the motor generator, and in generator operation it
is the drive shaft of the motor generator. The motor generator 5
replaces the starter and the otherwise conventional generator of an
internal combustion engine. The prime mover is therefore
significantly more compact.
[0033] The crank shaft 23 can be coupled via a clutch 6 to a
non-illustrated transmission. If the transmission is an automatic
transmission, then the clutch 6 is designed, for example, as a
torque converter clutch, preferably with a hydrodynamic
converter.
[0034] A control device 7 controls the prime mover. The control
device 7 is assigned sensors which register various measured
variables and in each case determine the measured value of the
measured variable. Depending on at least one operating variable,
the control device 7 determines one or more actuating signals that
control an actuator.
[0035] The sensors include the following: a pedal position
transmitter 81, which registers a pedal position PV of the
accelerator pedal 8; a throttle valve position transmitter 12,
which registers the degree of opening of the throttle valve; an air
mass meter 13, which registers an air mass flow, and/or an intake
pipe pressure sensor 14, which registers an intake pipe pressure in
the intake tract 1; a first temperature sensor 15, which registers
an intake air temperature; a revolution counter 24, which registers
the rotational speed N of the crank shaft 23, i.e., the speed of
the engine; and a second and third temperature sensor 26, 27, which
register an oil temperature TOIL and, respectively, a coolant
temperature TCO. Also provided is a measuring unit 51, which
registers a characteristic operating variable of the motor
generator 5. The characteristic operating variable of the motor
generator 5 can be, for example, a current or a voltage or an
output. The control device 7 can be assigned any desired subset of
the afore-mentioned sensors, but additional sensors can also be
assigned here.
[0036] Operating variables include measured variables and variables
which are derived from the latter, are determined via a
characteristic map relationship or by an observer which calculates
estimated values of the operating variables.
[0037] The actuators each comprise an actuating drive and an
actuating element. The actuating drive is an electric motor drive,
an electromagnetic drive, a mechanical drive, or any other
controlled drive. Such drives are known to those skilled in the
art. The actuating elements are designed as a throttle valve 10, as
an injection valve 11, as a spark plug 34 or as other actuating
elements. These are also known to those skilled in the art of
internal combustion engines. When referring to the actuators in the
following text, reference will also be had to the respectively
associated actuating element.
[0038] The control device, in the preferred embodiment, is an
electronic engine controller. However, it can also comprise a
plurality of control devices which are electrically conductively
connected to one another, for example in a bus system.
[0039] In the following text, the function of the part of the
control device 7 that is relevant to the invention will be
described with reference to the block diagrams of FIGS. 2A, 2B, 2C.
An estimated value MAF_CYL (see FIG. 2A) of the air mass flow into
the cylinder 20 is calculated, using a filling model of the intake
tract 1, on the basis of the measured value MAF_MES of the air mass
flow and further operating variables. A model of that type is
disclosed in WO 96/32579, the disclosure of which is hereby
incorporated by reference.
[0040] A characteristic map KF1 is provided, from which a first
contribution TQFR to a torque loss TQ_LOSS is determined on the
basis of the rotational speed N and the estimated value MAF_CYL of
the air mass flow in the cylinder 20. The first contribution TQFR
to the torque loss TQ_LOSS takes account of pump losses in the
internal combustion engine and losses which occur as a result of
friction given predefined reference values of the coolant
temperature TCO and of the oil temperature TOIL.
[0041] A second contribution TQFR_ADD to the torque loss TQ_LOSS is
determined from a characteristic map KF2 on the basis of the oil
temperature TOIL and/or the coolant temperature TCO. In addition, a
third contribution TQ_LOSS_MG to the torque loss is determined on
the basis of the measured signal M_MG which is generated by the
measuring unit 51. The third contribution TQ_LOSS_MG to the torque
loss TQ_LOSS is determined in a block B1 via a dynamic model of the
losses in the motor generator.
[0042] The dynamic model of the losses in the motor generator 5
preferably includes a characteristic curve, in which characteristic
values of the third contribution TQ_LOSS_MG are stored as a
function of a current registered through the motor generator 5. The
characteristic values are corrected with a correction factor which
depends on the temperature of the motor generator, this correction
factor preferably being subjected to PD.sub.1 filtering. The
temperature of the motor generator is either determined directly or
determined from a characteristic map on the basis of the power fed
to or taken from the motor generator. It is preferable if, during
the correction of the third contribution TQ_LOSS_MG to the torque
loss TQ_LOSS, the intake temperature is also taken into account.
The contributions TQFR, TQFR_ADD, TQ_LOSS_MG are added at a linking
point V1. Their sum then forms the torque loss TQ_LOSS.
[0043] In a block B2, a torque range which can be made available is
determined on the basis of the torque loss TQ_LOSS and the
rotational speed N. The gas pedal position PV and the rotational
speed N are used to determine what proportion of the torque range
that can be made available is requested by the driver.
[0044] The requested proportion of the torque and the torque which
can be made available are then used to determine a value TQI_REQ of
the torque which corresponds to the wish of the driver. In this
case, filtering of the value TQI_REQ of the torque corresponding to
the wish of the driver is preferably also provided, in order to
ensure that no load step changes occur which lead to unpleasant
jolting of the vehicle in which the prime mover is arranged.
[0045] In a block B3, a setpoint TQI_SP_MAF of the torque to be set
via the air mass flow is determined. In this case, in addition to
the value TQI_REQ of the torque, derivative-action values are taken
into account. For example, a derivative-action value TQI_IS is
predefined by an idling controller, a derivative-action value
TQI_CH is predefined by a function for heating up a catalytic
converter, a derivative-action value TQI_ASC is defined by a
traction control system, a derivative-action value TQI_N_MAX is
predefined by a function for limiting the rotational speed, or a
derivative-action value TQI_MSR is provided by an engine drag
torque control system. The setpoint TQI_SP_MAF of the torque to be
set via the air mass flow can therefore be higher or lower than the
value TQI_REQ of the torque which corresponds to the wish of the
driver.
[0046] By means of a characteristic map KF3, the setpoint
TQI_SP_MAF of the torque to be set via the air mass flow is
assigned a setpoint MAF__SP of the air mass flow on the basis of
the rotational speed N. The values of the characteristic map KF3
are derived from measurements on an engine test bench at a
reference air number LAM_REF and at a reference ignition angle
IGA_REF, or by means of a simulation calculation.
[0047] In a block B4, a setpoint THR_SP of the degree of opening of
the throttle valve 10 is determined on the basis of the setpoint
MAF_SP of the air mass flow. In a block B5, an actuating signal for
driving the throttle valve 10 is determined, preferably of a
position controller for the throttle valve 10.
[0048] The setpoint TQI_SP_MAF of the torque to be set via the air
mass flow takes predictive account of the torque to be set while
taking into account the dynamics of the intake tract.
[0049] In a block B6, a setpoint TQI_SP is determined of the torque
which is to be set within a predefined time period. The predefined
time period preferably corresponds to the time period which is
determined by a crank shaft segment. A crank shaft segment is
determined by the angle between two top-dead-center points of two
adjacent cylinders in the ignition sequence or else by the ignition
interval between two adjacent cylinders in the ignition sequence.
The setpoint TQI_SP of the torque must accordingly be set very
quickly, that is to say for example within one operating cycle of
the internal combustion engine.
[0050] In a block B6, the setpoint TQI_SP of the torque is
calculated on the basis of the value TQI_REQ of the torque
corresponding to the wish of the driver and the torque requirements
TQI_ASC_FAST, TQI_GS_FAST, TQI_N_MAX_FAST of a traction control
system, a transmission control system and a function for limiting
the rotational speed N. In addition, further torque requirements
can also be taken into account.
[0051] The determination of an estimated value TQI_BAS of the
maximum torque which can be set within the defined time period will
be explained below using FIG. 2B. A characteristic map KF4 is
provided, from which a reference value TQI_REF of the torque is
determined on the basis of the estimated value MAF_CYL and the
rotational speed N. The values of the characteristic map KF4 are
derived from measurements on an engine test bench at a reference
air number LAM_REF and at a reference ignition angle IGA_REF, or
are determined by means of a simulation calculation. The reference
value TQI_REF of the torque is accordingly in each case the torque
which, at the corresponding rotational speed and the corresponding
air mass flow into the cylinder, is the maximum which can
theoretically be realized if, at the same time, the efficiency
EFF_IGA referred to the ignition angle, and the efficiency EFF_LAM
referred to the air number are at a maximum.
[0052] In a characteristic map KF5, the reference ignition angle
IGA_REF is determined on the basis of the rotational speed, the
estimated value MAF_CYL of the air mass flow in the cylinder 20 and
the coolant temperature TCO.
[0053] In a characteristic map KF6, a pareto-optimum basic ignition
angle IGA_BAS is determined on the basis of the rotational speed N,
the estimated value MAF_CYL of the air mass flow into the cylinder
20 and the coolant temperature TCO.
[0054] At a linking point V2, the difference between the basic
ignition angle IGA_BAS and the reference ignition angle IGA_REF is
formed. In a block B8, the efficiency EFF_IGA of the ignition angle
is then determined on the basis of this difference. The efficiency
EFF_IGA of the ignition angle is normalized to the efficiency of
the ignition angle at the reference ignition angle IGA_REF.
[0055] The reference air number LAM_REF is determined from a
characteristic map KF7 on the basis of the rotational speed N and
the estimated value MAF_CYL of the air mass flow into the cylinder
20. A pareto-optimum basic air number LAM_BAS is determined from a
characteristic map KF8 on the basis of the rotational speed N and
an estimated value MAF_CYL of the air mass flow into the cylinder
20. At a linking point V3, the difference between the basic air
number LAM_BAS and the reference air number LAM.sub.-REF is formed
and then, in block B9, the efficiency EFF_LAM of the air number is
determined, normalized to the efficiency at the reference air
number LAM_REF.
[0056] In a block B10, the estimated value TQI_BAS of the maximum
torque is determined from the product of the reference value
TQI_REF of the torque, the efficiency EFF_IGA of the ignition angle
and the efficiency EFF_LAM of the air number. The estimated value
TQI_BAS of the maximum torque is accordingly the highest value of
the torque which can actually be applied by the internal combustion
engine at a given estimated value MAF_CYL of the air mass flow into
the cylinder 20, the rotational speed N and the coolant
temperature. The basic value TQI_BAS of the torque is therefore
always less than or equal to the reference value TQI_REF of the
torque.
[0057] In order to determine an estimated value TQI_MIN (FIG. 2C)
of the minimum torque, as distinct from determining the estimated
value TQI_BAS of the maximum torque, a minimum ignition angle
IGA_MIN is determined from a characteristic map KF10 on the basis
of the rotational speed N, the estimated value MAF_CYL and the
coolant temperature TCO, and then the difference between the
minimum ignition angle IGA_MIN and the reference ignition angle
IGA_REF is formed at the linking point V2.
[0058] In addition, in a characteristic map KF11, a minimum air
number LAM_MIN is determined on the basis of the rotational speed
and the estimated value MAF_CYL of the air mass flow into the
cylinder 20. The difference between the minimum air number LAM_MIN
and the reference air number LAM_REF is then formed at the linking
point V3. In addition, in a block B12, a cylinder shutdown
efficiency EFF_SCC is determined on the basis of the number of
cylinders shut down in overrun operation of the internal combustion
engine.
[0059] The estimated value TQI_MIN of the minimum torque is then
determined in block B13 by forming the product of the reference
value of the torque TQI_REF, the efficiency EFF_IGA of the ignition
angle, the efficiency EFF_LAM of the air number and the efficiency
EFF_SCC of the cylinder shutdown. The estimated value TQI_MIN of
the minimum torque is accordingly the lowest value of the torque
which can actually be applied by the internal combustion engine at
a given estimated value MAF_CYL of the air mass flow into the
cylinder 20, the rotational speed N and the coolant
temperature.
[0060] At a linking point V6 (FIG. 2A), the difference between the
setpoint TQI_SP of the torque and the estimated value TQI_BAS of
the maximum torque is determined. In a block B15, this difference
is limited to a predefined lower threshold value. The lower
threshold value can be chosen particularly simply to be equal to
zero. It can likewise be chosen to be less than zero or else
determined on the basis of the temperature of the motor generator
or of the charging level of a voltage supply (battery) of the
vehicle in which the prime mover is arranged. It is therefore
possible for the availability of the motor generator, that is to
say the time between two phases of the motor generator, to be
increased in a simple way. Likewise, the charging state of the
battery can in this way be kept to a predefined advantageous
value.
[0061] At a linking point V7, the difference between the setpoint
TQI_SP of the torque and the estimated value TQI_MIN of the minimum
torque is formed. In a block B16, this difference is then limited
to an upper threshold value, which either has the permanently
defined value zero or a permanently defined value greater than zero
or a value which depends on the temperature of the motor generator
5 or the charging level of the battery.
[0062] The sum of the output variables from the blocks B15 and B16
is then formed at a linking point V8 and assigned to a setpoint
TQ_MG_SP of the torque to be applied by the motor generator 5. In a
block B18, an actuating signal S_MG for the motor generator 5 is
then generated via a physical model of the motor generator, on the
basis of the setpoint TQ_MG_SP of the torque to be applied by the
motor generator, the temperature of the motor generator 5 and the
rotational speed N.
[0063] The physical model includes, for example, a characteristic
curve from which, depending on the setpoint TQ_MG_SP of the torque
to be applied by the motor generator 5, the actuating signal S_MG
of the motor generator is determined. The actuating signal S_MG of
the motor generator 5 is then further corrected by multiplication,
depending on a correction value. The correction value is determined
from a characteristic map on the basis of the temperature of the
motor generator 5 and the rotational speed N and then subjected to
PD.sub.1 filtering. A model of this type describes the dynamic
behavior of the motor generator sufficiently accurately.
[0064] The actuating signal S_MG is used to drive the motor
generator 5. The actuating signal S_MG can either be a current
through the windings of the motor generator 5 or a voltage. The
decisive signal parameter is either the amplitude or the frequency
of the voltage or of the current.
[0065] In the block B19, an estimated value TQ_MG_AV of the torque
applied by the motor generator 5 is determined via the physical
model of the motor generator, which is the inverse of that
described in block B18. In this case, the estimated value TQ_MG_AV
of the torque applied by the motor generator is determined on the
basis of the measured signal M_MG of the motor generator, which is,
for example, the voltage or the current through the motor generator
5.
[0066] At a linking point V8, the difference between the setpoint
TQI_SP of the torque and the estimated value TQ_MG_AV of the torque
actually applied by the motor generator is determined. The
difference determined at the linking point V8 accordingly
constitutes the proportion of the setpoint TQI_SP of the torque
which is not applied by the motor generator 5.
[0067] In a block B20, the ratio is determined between the
difference determined at the linking point V8 and the reference
value TQI_REF of the torque. The ratio is then the input variable
to a characteristic curve in a block B21, from which a setpoint
IGA_SP of the ignition angle is determined. The spark plug 34 is
then driven in accordance with the setpoint IGA_SP of the ignition
angle.
[0068] The control device 7 is distinguished by the fact that the
derivative-action values TQI_IS, TQI_CH, TQI_ASC and TQI.sub.-N_MAX
can be chosen to be low, since in the event of an actual request
for this torque, that is to say with high dynamics of the setpoint
TQI_SP, rapid setting can additionally be carried out via the motor
generator 5, whose response time is significantly lower than the
response time of the intake tract to changes in the throttle valve
position.
[0069] By means of a suitable choice of the upper and lower
threshold values in the blocks B16 and B17, it can additionally be
ensured that, even during non steady-state operation of the prime
mover, a torque derivative term TQI_CH remains, in order to ensure
high exhaust gas temperatures for heating the catalytic converter.
Via the motor generator, in each case the change in the torque
which cannot be achieved by adjusting the ignition angle can be
achieved. Furthermore, precise setting of the setpoint TQI_SP of
the torque is carried out via the actuator represented by the spark
plug 34. In addition, in the event of negative step changes in the
setpoint TQ_SP, the battery of the vehicle can be charged up,
instead of a conversion being made into lost heat.
[0070] FIGS. 3 and 4 are used to illustrate time profiles of the
setpoint TQI_SP of the torque in the event of a positive step
change in the setpoint TQI_SP, the estimated value TQI_BAS of the
maximum torque and an estimated value of a torque actually realized
in the internal combustion engine, the difference between the
reference ignition angle IGA_REF and the setpoint IGA_SP of the
ignition angle and the estimated value TQI_MG_AV of the actual
torque applied by the motor generator 5, plotted against the time
t. The same variables as in FIG. 3 are also plotted in FIG. 4
against the time t, although here the setpoint TQI_SP of the torque
changes, beginning at the time T=1 s, from a steady-state value (50
Nm) to the value 0 Nm. The estimated value TQI_MIN has the value 20
Nm in FIG. 3.
* * * * *