U.S. patent application number 09/836274 was filed with the patent office on 2001-11-08 for catalyst deterioration detecting apparatus and method for use with vehicles.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Uchida, Takahiro.
Application Number | 20010037642 09/836274 |
Document ID | / |
Family ID | 18637483 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010037642 |
Kind Code |
A1 |
Uchida, Takahiro |
November 8, 2001 |
Catalyst deterioration detecting apparatus and method for use with
vehicles
Abstract
A catalyst deterioration detecting apparatus and method detects
a deteriorated functional state of an catalyst provided in an
exhaust passage of an internal combustion engine of a vehicle. A
controller of the vehicle calculates a required total output that
is required for driving the vehicle, and an output adjusting
device, such as, for example, an electric motor, cooperates with
the engine to provide the required total output. The catalyst is
diagnosed so as to determine whether the catalyst is in a
deteriorated functional state. During the diagnosis of the
catalyst, the controller restricts the output of the engine to be
held within a predetermined range, and changes the output of the
output adjusting device as needed so as to provide the required
total output.
Inventors: |
Uchida, Takahiro;
(Susono-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
277 S. WASHINGTON STREET, SUITE 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
|
Family ID: |
18637483 |
Appl. No.: |
09/836274 |
Filed: |
April 18, 2001 |
Current U.S.
Class: |
60/277 ; 60/274;
903/903 |
Current CPC
Class: |
B60W 10/06 20130101;
Y02T 10/6286 20130101; B60W 2710/0622 20130101; B60W 10/26
20130101; Y02T 10/47 20130101; Y02T 10/54 20130101; B60W 10/08
20130101; Y02T 10/40 20130101; Y02T 10/62 20130101; F01N 2550/02
20130101; B60W 20/00 20130101; B60K 6/445 20130101; B60W 2050/021
20130101; Y02T 10/6239 20130101; F01N 11/007 20130101 |
Class at
Publication: |
60/277 ;
60/274 |
International
Class: |
F01N 003/00; F01N
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2000 |
JP |
2000-127970 |
Claims
What is claimed is:
1. A catalyst deterioration detecting apparatus for detecting a
deteriorated functional state of a catalyst provided in an exhaust
passage of an internal combustion engine of a vehicle, the vehicle
further including an output adjusting device that cooperates with
the internal combustion engine to provide a predetermined total
output that is required for driving the vehicle, the apparatus
comprising: a controller that: performs a diagnostic operation to
diagnose the catalyst so as to determine whether the catalyst is in
a deteriorated functional state; and during the performance of the
diagnostic operation, restricts the output of the internal
combustion engine to be held within a predetermined range, and
changes the output of the output adjusting device to provide the
predetermined total output.
2. The apparatus according to claim 1, wherein the controller:
detects a plurality of operating conditions of the vehicle; and
initiates the performance of the diagnostic operation when the
detected operating conditions of the vehicle are suitable for
diagnosing the catalyst.
3. The apparatus according to claim 1, wherein the controller:
detects a plurality of operating conditions of the vehicle; and
initiates performance of a compulsory diagnostic operation when the
detected operating conditions of the vehicle are not suitable for
diagnosing the catalyst; wherein the controller restricts the
output of the internal combustion engine upon initiation of the
compulsory diagnostic operation so that the output of the internal
combustion engine is held within the predetermined range.
4. The apparatus according to claim 3, wherein the controller
initiates the compulsory diagnostic operation under a predetermined
condition.
5. The apparatus according to claim 1, wherein the controller
controls the output of the internal combustion engine such that an
amount of change of the output of the internal combustion engine is
smaller than a predetermined maximum value.
6. The apparatus according to claim 1, wherein the controller
controls the output of the internal combustion engine such that the
output of the internal combustion engine is kept larger than zero,
throughout the performance of the diagnostic operation.
7. The apparatus according to claim 1, wherein: the vehicle has a
hybrid drive including the internal combustion engine and an
electric motor, and the output adjusting device comprises the
electric motor; the controller calculates an output of the internal
combustion engine and an output of the electric motor depending
upon an operating state of the vehicle; and during the performance
of the diagnostic operation, the controller controls the outputs of
the internal combustion engine and of the electric motor,
irrespective of the calculated outputs, so as to restrict the
output of the internal combustion engine and change the output of
the electric motor such that a sum of the restricted output of the
internal combustion engine and the changed output of the electric
motor is equal to the predetermined total output.
8. The apparatus according to claim 7, wherein the controller:
detects a plurality of operating conditions of the vehicle; and
initiates the performance of the diagnostic operation when the
detected operating conditions of the vehicle are suitable for
diagnosing the catalyst.
9. The apparatus according to claim 7, wherein the controller:
detects a plurality of operating conditions of the vehicle; and
initiates performance of a compulsory diagnostic operation when the
detected operating conditions of the vehicle are not suitable for
diagnosing the catalyst; wherein the controller restricts the
output of the internal combustion engine upon initiation of the
compulsory diagnostic operation so that the output of the internal
combustion engine is held within the predetermined range.
10. The apparatus according to claim 9, wherein the controller
initiates the compulsory diagnostic operation under a predetermined
condition.
11. The apparatus according to claim 7, wherein the controller
controls the output of the internal combustion engine such that an
amount of change of the output of the internal combustion engine is
smaller than a predetermined maximum value.
12. The apparatus according to claim 7, wherein the controller
controls the output of the internal combustion engine such that the
output of the internal combustion engine is kept larger than zero,
throughout the performance of the diagnostic operation.
13. A hybrid vehicle comprising: an internal combustion engine
including an exhaust passage having a catalyst therein; an electric
motor, the internal combustion engine and the electric motor
coupled to drive wheels of the vehicle by a transmission, the
electric motor cooperating with the internal combustion engine to
provide a predetermined total output to the drive wheels; and a
controller that: performs a diagnostic operation to diagnose the
catalyst so as to determine whether the catalyst is in a
deteriorated functional state; and during the performance of the
diagnostic operation, restricts the output of the internal
combustion engine to be held within a predetermined range, and
changes the output of the electric motor to provide the
predetermined total output.
14. The hybrid vehicle according to claim 13, wherein the
controller: detects a plurality of operating conditions of the
vehicle; and initiates the performance of the diagnostic operation
when the detected operating conditions of the vehicle are suitable
for diagnosing the catalyst.
15. The hybrid vehicle according to claim 13, wherein the
controller controls the output of the internal combustion engine
such that an amount of change of the output of the internal
combustion engine is smaller than a predetermined maximum
value.
16. The hybrid vehicle according to claim 13, wherein the
controller controls the output of the internal combustion engine
such that the output of the internal combustion engine is kept
larger than zero, throughout the performance of the diagnostic
operation.
17. A catalyst deterioration detecting method for detecting a
deteriorated functional state of a catalyst provided in an exhaust
passage of an internal combustion engine of a vehicle, the vehicle
including an output adjusting device that cooperates with the
internal combustion engine to provide a predetermined total output
that is required for driving the vehicle, the method comprising:
performing a diagnostic operation to diagnose the catalyst so as to
determine whether the catalyst is in a deteriorated functional
state; and during the performance of the diagnostic operation,
restricting the output of the internal combustion engine to be held
within a predetermined range, and changing the output of the output
adjusting device to provide the predetermined total output.
18. The method according to claim 17, further comprising: detecting
a plurality of operating conditions of the vehicle; and initiating
the performance of the diagnostic operation when the detected
operating conditions of the vehicle are suitable for diagnosing the
catalyst.
19. The method according to claim 17, further comprising: detecting
a plurality of operating conditions of the vehicle; and initiating
performance of a compulsory diagnostic operation when the detected
operating conditions of the vehicle are not suitable for diagnosing
the catalyst; wherein, upon initiation of the compulsory diagnostic
operation, the output of the internal combustion engine is
restricted so that the output of the internal combustion engine is
held within the predetermined range.
20. The method according to claim 19, wherein the compulsory
diagnostic operation is initiated under a predetermined
condition.
21. The method according to claim 17, wherein the output of the
internal combustion engine is controlled such that an amount of
change of the output of the internal combustion engine is smaller
than a predetermined maximum value.
22. The method according to claim 17, wherein the output of the
internal combustion engine is controlled such that the output of
the internal combustion engine is kept larger than zero throughout
the performance of the diagnostic operation.
23. The method according to claim 17, wherein the vehicle has a
hybrid drive including the internal combustion engine and an
electric motor, and the output adjusting device comprises the
electric motor; and the method further comprises: calculating an
output of the internal combustion engine and an output of the
electric motor depending upon an operating state of the vehicle;
and during the performance of the diagnostic operation, controlling
the outputs of the internal combustion engine and of the electric
motor, irrespective of the calculated outputs, so as to restrict
the output of the internal combustion engine and changes the output
of the electric motor such that a sum of the restricted output of
the internal combustion engine and the changed output of the
electric motor is equal to the predetermined total output.
24. The method according to claim 23, further comprising: detecting
a plurality of operating conditions of the vehicle; and initiating
the performance of the diagnostic operation when the detected
operating conditions of the vehicle are suitable for diagnosing the
catalyst.
25. The method according to claim 23, further comprising: detecting
a plurality of operating conditions of the vehicle; and initiating
performance of a compulsory diagnostic operation when the detected
operating conditions of the vehicle are not suitable for diagnosing
the catalyst; wherein, upon initiation of the compulsory diagnostic
operation, the output of the internal combustion engine is
restricted so that the output of the internal combustion engine is
held within the predetermined range.
26. The method according to claim 25, wherein the compulsory
diagnostic operation is initiated under a predetermined
condition.
27. The method according to claim 23, wherein the output of the
internal combustion engine is controlled such that an amount of
change of the output of the internal combustion engine is smaller
than a predetermined maximum value.
28. The method according to claim 23, wherein the output of the
internal combustion engine is controlled such that the output of
the internal combustion engine is kept larger than zero, throughout
the performance of the diagnostic operation.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2000-127970 filed on Apr. 27, 2000, including the specification,
drawings and abstract, is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The invention relates to a catalyst deterioration detecting
apparatus and method adapted to detect deterioration of an emission
purifying catalyst used on a vehicle, for example, a hybrid
automotive vehicle.
[0004] 2. Description of Related Art
[0005] An emission purifying catalyst is generally provided in an
exhaust passage of an internal combustion engine of an automotive
vehicle, for purifying exhaust gas emitted from the engine by
removing or reducing unburned fuel, carbon monoxide, nitrogen
oxides, and other components contained in the exhaust gas. In order
to suppress or reduce an amount of increase of the remaining
undesirable components discharged into the atmosphere due to
deterioration of the catalyst, it has been proposed to provide the
internal combustion engine with a catalyst deterioration detecting
apparatus adapted to detect a deteriorated functional state of the
catalyst. For assuring high accuracy of diagnosis as to whether the
catalyst has been deteriorated, it is preferable to perform the
diagnosis while the amount or degree of variation in the output of
the engine is relatively small. On the other hand, the output of
the engine is required to vary according to an operating or running
condition of the vehicle desired by an operator or driver of the
vehicle. Accordingly, it is usually difficult for the catalyst
deterioration detecting apparatus to perform the diagnosis in an
appropriate condition of the vehicle. In view of this situation,
various attempts have been made to assure an appropriate
opportunity that permits the catalyst deterioration detecting
apparatus to achieve accurate diagnosis as to whether the catalyst
has been deteriorated. An example of a catalyst deterioration
detecting apparatus resulting from such attempts is disclosed in
JP-A-9-144532.
[0006] The catalyst deterioration detecting apparatus disclosed in
JP-A-9-144532 reduces the amount of variation of the output of the
internal combustion engine by reducing or restricting the amount of
change of a throttle valve (e.g., throttle opening) of the engine
with a change in the amount of operation of an accelerator pedal
provided on the vehicle, during an operation of the catalyst
deterioration detecting apparatus to determine whether the catalyst
is in a deteriorated functional state. For instance, the rate of
increase of the opening of the throttle valve is lowered, or an
opening action of the throttle valve is temporarily inhibited,
during the diagnosis as to whether the catalyst is in the
deteriorated functional state. This arrangement of the catalyst
deterioration detecting apparatus, however, may prevent the engine
from providing the output desired by the vehicle operator.
SUMMARY OF THE INVENTION
[0007] It is therefore an object of the invention to provide a
catalyst deterioration detecting apparatus and method of a vehicle,
which is able to accurately detect a deteriorated functional state
of a catalyst provided in an exhaust passage of an internal
combustion engine at an early opportunity.
[0008] To accomplish the above and/or other objects, one aspect of
the invention provides a catalyst deterioration detecting apparatus
and method for detecting a deteriorated functional state of a
catalyst provided in an exhaust passage of an internal combustion
engine of a vehicle. A controller of the vehicle calculates a
required total output that is required for driving the vehicle, and
an output adjusting device, for example, an electric motor
cooperates with the internal combustion engine to provide the
required total output. The catalyst deterioration detecting
apparatus performs a diagnostic operation to diagnose the catalyst
so as to determine whether the catalyst is in a deteriorated
functional state. During the diagnostic operation of the catalyst,
the output of the internal combustion engine is restricted to be
held within a predetermined range, while the output of the output
adjusting device is changed as needed so as to provide the required
total output calculated as described above.
[0009] In a preferred embodiment of the invention, the vehicle has
a hybrid drive device including the engine and an electric motor,
and the electric motor functions as the output adjusting device.
The controller of the vehicle calculates an output of the internal
combustion engine and an output of the electric motor depending
upon an operating state of the vehicle. In this case, during the
diagnostic operation, the outputs of the engine and the electric
motor are controlled, irrespective of the outputs calculated based
on the operating state of the vehicle, so as to restrict the output
of the engine while changing the output of the electric motor as
needed such that a sum of the restricted output of the engine and
the changed output of the electric motor is equal to the required
total output.
[0010] In the catalyst deterioration detecting apparatus and method
described above, the outputs of the internal combustion engine and
the electric motor are controlled during diagnostic operation to
diagnose the catalyst, so that the output of the engine is
restricted to remain within the predetermined range while the
output of the electric motor is changed so that a sum of the
restricted output of the engine and the changed output of the
electric motor is equal to the required total output. Since the
engine is operated with a reduced amount of change of its output,
the catalyst can be diagnosed with a higher degree of accuracy,
without a significant adverse influence of the engine output change
on the determination as to whether the catalyst is in a
deteriorated functional state. Further, the catalyst deterioration
detecting apparatus and method of the invention permits the
above-indicated determination to be completed in a relatively short
time. Moreover, the restriction of the output of the engine does
not sacrifice the driving performance or driveability of the
vehicle, because the output of the electric motor is changed so
that the sum of the restricted output of the engine and the changed
output of the electric motor is equal to the required total output
of the hybrid vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention will be described in conjunction with the
following drawings in which like reference numerals designate like
elements and wherein:
[0012] FIG. 1 is a block diagram illustrating a hybrid automotive
vehicle provided with a catalyst deterioration detecting apparatus
according to one embodiment of this invention;
[0013] FIG. 2 is a perspective view of a power distributing
mechanism of a hybrid drive device of the vehicle, and other
components of the vehicle of FIG. 1, which includes an emission
purifying catalyst;
[0014] FIG. 3 is a flowchart illustrating a routine executed to
turn on or off a DETECTING CONDITION flag used by the catalyst
deterioration detecting apparatus to initiate its normal detecting
operation;
[0015] FIG. 4 is a flowchart illustrating a catalyst deterioration
detecting routine executed to perform a diagnostic operation that
diagnoses whether the catalyst is in a deteriorated functional
state;
[0016] FIG. 5A is a graph indicating a relationship among an
operator's desired vehicle output, an output of the engine and an
output of the electric motor, when the catalyst deterioration
detecting apparatus is not in operation;
[0017] FIG. 5B is a graph indicating a relationship among the
operator's desired vehicle output and the outputs of the engine and
electric motor while the catalyst deterioration detecting apparatus
is in operation;
[0018] FIG. 6 is a flowchart illustrating a routine executed to
turn on or off a COMPULSORY DIAGNOSIS flag used by the
catalyst-detection detecting apparatus to initiate its compulsory
diagnosis; and
[0019] FIG. 7 is a flowchart illustrating a routine executed by the
main control unit to effect the compulsory diagnosis.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] Referring first to FIG. 1, there is illustrated a hybrid
automotive vehicle having a hybrid drive device and a catalyst
deterioration detecting apparatus according to one embodiment of
the invention. The hybrid drive device includes an internal
combustion engine 1 and an electric motor 2. The catalyst
deterioration detecting apparatus is adapted to diagnose an
emission purifying catalyst 29 provided in an exhaust passage 28
connected to the engine 1 (see FIG. 2).
[0021] The hybrid drive device of the hybrid vehicle further
includes an electric generator 3 operable with an output of the
engine 1 (i.e., powered by the engine 1) to generate electric
energy, and a power distributing mechanism 4 operatively connected
to the engine 1, the electric motor 2 and the electric generator 3.
The power distributing mechanism 4 is arranged to distribute the
output of the engine 1 to the electric generator 3 and to the drive
wheels 7 of the vehicle, as needed, and to transmit an output of
the electric motor 2 to the drive wheels 7. The power distributing
mechanism 4 also functions as a power transmission capable of
transmitting a rotary motion of the engine 1 and/or electric motor
2 to the drive wheels 7 through a differential gear 5 and drive
axles 6, at a controlled speed ratio. The construction of the power
distributing mechanism 4 will be described in detail with reference
to FIG. 2.
[0022] The electric motor 2 is a synchronous alternating-current
(AC) motor operable with alternating current applied thereto. An
inverter 9 is connected to the electric motor 2, a battery 8 and
the electric generator 3. The inverter 9 functions to convert
direct-current (DC) power received from the battery 8 into
alternating-current (AC) power to be applied to the electric motor
2, and to convert AC power generated by the electric generator 3
into DC power to be stored in the battery 8. The electric generator
3 takes the form of a synchronous AC motor, which is basically
identical in construction with the motor 2. The electric motor 2 is
operated primarily for generating driving force for driving the
vehicle, while the electric generator 3 is operated principally
with an output of the engine 1, for generating an electric energy
to be used by the motor 2.
[0023] Although the electric motor 2 mainly functions to generate
driving force, the motor 2 also is able to generate electric energy
by utilizing rotation of the drive wheels 7 (i.e., by means of
regenerative braking). Namely, the motor 2 may convert kinetic
energy of the drive wheels 7 into electric energy while applying a
regenerative brake force to the drive wheels 7. The vehicle can be
suitably braked, by utilizing this regenerative brake force in
combination with a hydraulically operated brake provided for each
wheel, and an "engine brake" well known in the art. On the other
hand, the electric generator 3, which is usually operated with the
output of the engine 1 to generate an electric energy, may function
as an electric motor, with an electric energy received from the
battery 8 through the inverter 9.
[0024] Referring next to FIG. 2, there is shown the hybrid drive
device including the power distributing mechanism 4, engine 1,
electric motor 2 and electric generator 3. In the present
embodiment, the power distributing mechanism 4 takes the form of a
planetary gear device, and will be referred to hereinafter as
"planetary gear device 4". The planetary gear device 4 includes a
sun gear 4a, planetary gears 4b disposed around the sun gear 4a, a
ring gear 4c disposed radially outwardly of the planetary gears 4b,
and a carrier 4d which supports the planetary gears 4b.
[0025] The engine 1 has a crankshaft 15 which is connected through
a damper 16 to a center shaft 17 connected to the carrier 4d of the
planetary gear device 4, so that the output of the engine 1 is
transmitted to the carrier 4d through the crankshaft 15, damper 16
and center shaft 17. The electric motor 2 incorporates a stator 2a,
and a rotor 2b which is connected to the ring gear 4c. The rotor 2b
and the ring gear 4c are connected to a first gear 18. The output
of the electric motor 2 transmitted to the ring gear 4c is
transmitted to the drive axles 6 through the first gear 18, a
transmission chain 19, a second gear 20, a third gear 21, a final
gear 22 and the differential gear 5 indicated above.
[0026] Like the electric motor 2, the electric generator 3
incorporates a stator 3a, and a rotor 3b which is connected to the
sun gear 4a of the planetary gear device 4. Thus, the output of the
engine 1 is distributed by the planetary gear device 4, and is
transmitted through the sun gear 4a to the rotor 3b of the electric
generator 3. The output of the engine 1 is also distributed by the
planetary gear device 4, to be transmitted to the drive axles 6
through the ring gear 4c and the other rotary elements indicated
above. By controlling the amount of electric energy to be generated
by the electric generator 3, thereby controlling the rotating speed
of the sun gear 4a, the planetary gear device 4 can be used as a
continuously variable transmission capable of controlling the ratio
of the speed of the engine 1 and/or motor 2 to the speed of the
drive axles 6. Further, the speed of the engine 1 can be controlled
by controlling the amount of electric energy to be generated by the
electric generator 3 (by controlling the amount of electric energy
consumption of the electric generator 3 when the electric generator
3 is operated as an electric motor).
[0027] The hybrid drive device provided on the hybrid automotive
vehicle described above has the following modes of operation: a
MOTOR DRIVE mode, a HIGH-LOAD ENGINE-AND-MOTOR DRIVE mode, a
FULL-POWER ENGINE-AND-MOTOR DRIVE mode; a REGENERATIVE BRAKING
mode; and an ENGINE DRIVE & CHARGING mode. The MOTOR DRIVE mode
is selected for starting the vehicle or driving the vehicle under a
relatively low load. In the MOTOR DRIVE mode, the vehicle is driven
with driving force generated by only the electric motor 2 operated
with electric energy supplied from the battery 8. The electric
motor 2 is capable of producing relatively large torque at a
relatively low operating speed, and can be effectively utilized as
a drive source for driving the vehicle in a low load condition. The
HIGH-LOAD ENGINE-AND-MOTOR DRIVE mode is selected when the vehicle
is driven at a relatively high speed under a relatively high load.
In the HIGH-LOAD ENGINE-AND-MOTOR DRIVE mode, the engine 1 is
operated to provide vehicle driving force, and the electric motor 2
is driven with electric power generated by the electric generator 3
that receives the output of the engine 1. Thus, the driving force
produced by the engine 1 and the driving force produced by the
electric motor 2 are used to operate or run the vehicle.
[0028] The FULL-POWER ENGINE-AND-MOTOR DRIVE mode is selected for
driving the vehicle with further increased driving force, for
example, upon full depression of the accelerator pedal. In the
FULL-POWER ENGINE-AND-MOTOR DRIVE mode, the electric motor 2 is
operated with electric energy generated by the electric generator 3
and electric energy supplied from the battery 8, and at the same
time the engine 1 is operated so as to provide increased driving
force, so that the vehicle is driven with both the driving force
generated by the electric motor 2 and the drive force produced by
the engine 1. The REGENERATIVE BRAKING mode is selected during
deceleration, coasting or braking of the vehicle. In the
REGENERATIVE BRAKING mode, the electric motor 2 is caused to
generate electric energy by utilizing rotary motion of the drive
wheels 7 (i.e., by converting kinetic energy of the drive wheels 7
into electric energy through regenerative braking), so that the
vehicle is braked with a regenerative braking force produced by the
motor 2. The ENGINE DRIVE & CHARGING mode is selected for
running the vehicle with the engine 1 while the amount of electric
energy stored in the battery 8 is smaller than a lower limit. In
this ENGINE DRIVE & CHARGING mode, the engine 1 is operated
even during running of the vehicle under a relatively low load, to
operate the electric generator 3 for charging the battery 8 through
the inverter 9.
[0029] The hybrid drive device is controlled in a selected one of
the operating modes indicated above, by an electronic main control
unit (main ECU) 10, an electronic engine control unit (engine ECU)
11, an electronic motor control unit (motor ECU) 12, an electronic
battery control unit (battery ECU 13) and an electronic brake
control unit (brake ECU) 14. Described more specifically, the
engine 1, the electric motor 2 and the electric generator 3 are
systematically controlled by the main ECU 10, which is arranged to
calculate a required total output of the hybrid drive device on the
basis of various physical quantities or parameters indicative of
the operating conditions of the vehicle, and determine a required
output of the engine 1 and a required output of the electric motor
2 and generator 3, namely, a distribution ratio of these required
outputs with respect to each other, so as to meet the calculated
required total output of the hybrid drive device for driving the
vehicle. On the basis of the determined distribution ratio of the
required outputs of the engine 1 and the electric motor 2 and
generator 3, the main ECU 10 commands the engine ECU 11 and motor
ECU 12 to suitably control the engine 1, electric motor 2 and
electric generator 3.
[0030] The engine ECU 11 and the motor ECU 12 provide the main ECU
10 with information or signals indicative of the operating states
of the engine 1, electric motor 2 and electric generator 3. To the
main ECU 10, there are also connected the battery ECU 13 for
controlling the battery 8, and the brake ECU 14 for controlling the
vehicle braking system. The battery ECU 13 is arranged to monitor
the battery 8 for its charging state, and if the amount of electric
energy stored in the battery 8 is smaller than the lower limit,
supplies the main ECU 10 with a battery charging command. When the
main ECU 10 receives this battery charging command, the main ECU 10
commands the electric generator 3 to be operated to charge the
battery 8. The brake ECU 14 is arranged to control the vehicle
braking system, and cooperates with the main ECU 10 to control the
electric motor 2 when serving as a regenerative brake.
[0031] In the hybrid vehicle provided with the hybrid drive device
including the engine 1 and the electric motor 2 as drive power
sources, the distribution ratio of the actual outputs of the engine
1 and the electric motor 2 can be changed as needed, without
changing the actual total output of the hybrid drive device (actual
total output of the vehicle). Namely, the output of the engine 1
can be reduced while increasing the output of the electric motor 2,
and can be increased while reducing the output of the electric
motor 2. The catalyst deterioration detecting apparatus according
to this embodiment of the invention utilizes the ability to control
the distribution ratio of the outputs of the engine 1 and the
electric motor 2, as described below.
[0032] The catalyst deterioration detecting apparatus detects
deterioration of a catalyst by various methods selected from
various known methods. An example of such methods will now be
described. The catalyst deterioration detecting apparatus adapted
to diagnose the emission purifying catalyst 29 of the engine 1
includes the engine ECU 11, an upstream air/fuel ratio sensor 23
and a downstream air/fuel ratio sensor 30, which are disposed on
respective upstream and downstream sides of the catalyst 29, as
shown in FIG. 2. The catalyst deterioration detecting apparatus may
be arranged as disclosed in JP-A-9-144532 identified above.
Briefly, the apparatus is arranged to diagnose the catalyst 29 on
the basis of lengths of voltage waveforms or curves representing
periodic changes in the output voltage of the upstream and
downstream air/fuel ratio sensors 23, 30, within a predetermined
length of time, and on the basis of surface areas enclosed by the
above-indicated voltage waveforms and respective straight reference
lines representing respective predetermined reference values of the
output voltages of the sensors 23, 30, within the predetermined
length of time. Each of these two voltage waveforms is expressed in
a rectangular coordinate system in which the output voltage is
taken along an ordinate while the time is taken along an abscissa.
The length of each voltage waveform may be replaced by a sum of
successive amounts of change of the output voltage of the
corresponding air/fuel ratio sensor 23, 30 in respective successive
unit times a sum of which is equal to the predetermined time
indicated above. The straight reference line representing the
predetermined reference value of the output voltage of each sensor
23, 30 is parallel to the abscissa, and the reference value is
selected such that the output curve has portions which are
alternately located above and below the straight reference line in
question. The above-indicated surface area of each sensor 23, 30
output may be replaced by a sum of successive amounts of difference
of the output voltage from the reference value at respective points
of time having a predetermined time interval corresponding to each
unit time indicated above. Described more precisely, a diagnosis as
to whether the catalyst 29 is in a deteriorated functional state is
based on a ratio of the length of the voltage waveform of the
downstream air/fuel ratio sensor 30 to that of the voltage waveform
of the upstream air/fuel ratio sensor 23, and on a ratio of the
surface area of the output waveforms of the downstream sensor 30 to
that of the upstream sensor 23, while the air/fuel ratio of the
air-fuel mixture introduced into the engine 1 is controlled in a
feedback fashion. These ratios of the lengths and surface areas are
used as diagnostic parameters for diagnosing the catalyst 29. The
disclosure of JP-A-9-144532 is incorporated herein by reference in
its entirety.
[0033] The air/fuel ratio of the air-fuel mixture is controlled
according to a control program stored in a read-only memory of the
engine ECU 11, based on output signals of the upstream and
downstream air/fuel ratio sensors 23, 30 described above, and based
on output signals of an air flow meter 24, a crank position sensor
25, a throttle opening sensor 26 and so on. The output signals of
the air/fuel ratio sensors 23, 30 change with the oxygen
concentration of exhaust gas emitted from the engine 1. On the
basis of the output signals of the sensors 23, 30, the engine ECU
11 determines that the air-fuel mixture burned in the engine 1 is
fuel-rich, fuel-lean or stoichiometric, that is, determines that
the air/fuel ratio of the mixture is lower or higher than the
stoichiometric value or equal to the stoichiometric value.
[0034] As shown in FIG. 2, the air flow meter 24 is provided at a
suitable position along an intake passage 27 of the engine 1, to
detect the flow rate of intake air introduced into the engine 1. In
the present embodiment, the air flow meter 24 is of the hot-wire
type. The crank position sensor 25 is provided to detect a rotary
position of the crankshaft 15 of the engine 1. The revolving speed
of the engine 1 can be calculated on the basis of the output signal
of the crank position sensor 25. The throttle opening sensor 26 is
provided to detect the opening of a throttle valve of the engine
provided in the intake passage 27. On the basis of the output
signals of the sensors 23-26 and 30 described above, the engine ECU
11 controls the air-fuel ratio of the air-fuel mixture of the
engine 1 in a feedback fashion, and at the same time diagnoses the
catalyst 29 to determine whether the catalyst 29 is in a
deteriorated functional state.
[0035] Referring to the flowcharts of FIGS. 3 and 4 and the graphs
of FIGS. 5A and 5B, there will be described the diagnosis of the
catalyst 29. The catalyst deterioration detecting apparatus
according to this embodiment is arranged to initiate normal
diagnosis of the catalyst 29 when the engine 1 (vehicle) is in
operating states suitable for diagnosing the catalyst 29. The
normal diagnosis is effected while the engine 1 is held in this
operating state. The apparatus is further arranged to effect
compulsory diagnosis when predetermined conditions for initiating
the compulsory diagnosis are satisfied.
[0036] When the compulsory diagnosis of the catalyst 29 is
effected, the operating state of the engine 1 is made suitable for
detection of deterioration of the catalyst 29 if the engine
operation state upon the start of the diagnosis is not suitable for
detection of catalyst deterioration. For example, if the operating
state of the engine 1 is not suitable for diagnosing the catalyst
29, the distribution ratio of the output of the electric motor 2
with respect to the required total output is controlled so as to
bring the operating state of the engine 1 into the operating state
that is suitable for diagnosing the catalyst 29, or if the engine 1
is stopped, the engine 1 is started and then its operating state is
brought into the operating state that is suitable for diagnosing
the catalyst 29.
[0037] The normal diagnosis of the catalyst 29 when the engine 1 is
in the operating state suitable for diagnosing the catalyst 29 will
be described first.
[0038] The flowchart of FIG. 3 shows the routine executed to
determine whether the engine 1 is in the operating state suitable
for diagnosing the catalyst 29, and turn on or off a DETECTING
CONDITION flag depending upon whether the engine 1 is in the
suitable operating state or not. The routine is initiated with step
S100 in which the engine ECU 11 reads various operating states or
conditions of the vehicle (engine 1), such as the temperatures of
the intake air and coolant of the engine 1, the voltage of the
battery 8, the voltage of a battery for accessories, the revolving
speed and intake flow rate of the engine 1, the state of the
feedback control of the air/fuel ratio of the air-fuel mixture of
the engine 1, the state of change of the air/fuel ratio, and the
temperature of the catalyst 29. The battery for accessories is
provided in addition to the battery 8 for operating the electric
motor 2, to operate other electrically operated devices, or
accessories, provided on the vehicle. The voltage of the battery 8
is detected by the battery ECU 13, and the speed of the engine 1 is
obtained from the output signal of the crank position sensor 25.
The intake flow rate of the engine 1 is detected by the air flow
meter 24, and the state of the feedback control of the air/fuel
ratio and the state of change of the air/fuel ratio are detected on
the basis of the output signals of the air/fuel ratio sensors 23,
30.
[0039] Then, the control process proceeds to step S110 to determine
whether the vehicle operating states detected in step S100 are
suitable for diagnosing the catalyst 29. In this embodiment in
which the diagnosis of the catalyst 29 is effected on the basis of
the output voltages of the air/fuel ratio sensors 23, 30, the
catalyst 29 cannot be diagnosed with high accuracy while the output
of the engine 1 is considerably changing, since the air/fuel ratio
of the air-fuel mixture is also considerably changing in this state
of the engine 1. Further, the diagnosis of the catalyst 29 is not
initiated while the air/fuel ratio of the air-fuel mixture is not
controlled in the feedback fashion, since the present catalyst
deterioration detecting apparatus is arranged to diagnose the
catalyst 29 during the feedback control of the air/fuel ratio.
[0040] If the vehicle operating states are suitable for effecting
the diagnosis of the catalyst 29, an affirmative decision (YES) is
obtained in step S110, and the control process proceeds to step
S120 to turn ON the DETECTING CONDITION flag. If the vehicle
operating states are not suitable for effecting the diagnosis of
the catalyst 29, a negative decision (NO) is obtained in step S110,
and the control process proceeds to step S130 to turn OFF the
DETECTING CONDITION flag. The routine of FIG. 3 is executed
cyclically (e.g., every several to several hundred milliseconds) by
the main ECU 10 according to a control program stored in its ROM,
so that the DETECTING CONDITION flag is turned ON or OFF in each
cycle of execution of the routine.
[0041] Concurrently with the routine of FIG. 3, a routine
illustrated in the flowchart of FIG. 4 is executed to determine
whether the catalyst 29 is in a deteriorated functional state. This
routine is also executed cyclically by the main ECU 10, according
to a control program also stored in the ROM. The routine of FIG. 4
is initiated with step S200 to determine whether the DETECTING
CONDITION flag is placed in the ON state. If this flag is not
placed in the ON state, it means that the vehicle (engine 1) is not
placed in the operating states suitable for diagnosing the catalyst
29. In this case, one cycle of execution of the routine of FIG. 4
is terminated. If the DETECTING CONDITION flag is placed in the ON
state, it means that the vehicle (engine 1) is placed in the
operating states suitable for diagnosing the catalyst 29. In this
case, the control process goes to step S210 to determine whether it
is permissible to restrict the output of the engine 1, more
precisely, to restrict the amount of change of the output of the
engine 1 or hold the output of the engine 1 within a predetermined
relatively narrow range.
[0042] Under some vehicle operating conditions in which the engine
1 is controlled for a purpose other than the diagnosis of the
catalyst 29 or any device other than the engine 1 is controlled, it
is not desirable to restrict the output of the engine 1 to within
the predetermined narrow range or to limit the maximum amount of
change of the output of the engine 1. In view of these vehicle
operating conditions, step S210 is provided to determine whether
the restriction of the output of the engine 1 is permissible. If
the present vehicle operating condition permits the restriction of
the engine output, the control process proceeds to step S220 to
restrict the output of the engine 1 to within the predetermined
narrow range suitable for diagnosing the catalyst 29 with high
accuracy.
[0043] Normally, the output of the engine 1 is determined on the
basis of various detected vehicle operating states and according to
a normal control data map stored in the ROM of the main ECU 10 or
engine ECU 11. In the hybrid vehicle, the distribution ratio of the
output of the engine 1 with respect to the output of the electric
motor 2 is determined according to this normal control data map,
which is used while the catalyst deterioration detecting apparatus
is not in operation to diagnose the catalyst 29. According to the
normal control data map, the output of the engine 1 is determined
on the basis of various factors such as the fuel economy of the
vehicle and the amount of electric energy stored in the battery 8.
Accordingly, the output of the engine 1 as determined according to
the normal control data map is not necessarily held within a
relatively narrow range, and tends to vary by a relatively large
amount, as indicated in the graph of FIG. 5A by way of example. The
catalyst 29 cannot be diagnosed with high accuracy if the diagnosis
is effected while the output of the engine 1 is varying
considerably as indicated in FIG. 5A. When the catalyst 29 is
diagnosed, therefore, the output of the engine 1 is restricted so
as to be held within the predetermined relatively narrow range, as
indicated in the graph of FIG. 5B.
[0044] The required total output of the hybrid drive device (engine
1 and electric motor 2) is provided by a sum of the output of the
engine 1 and the output of the electric motor 2. In the example of
FIG. 5A according to the normal control data map, the output of the
electric motor 2 constitutes a major portion of the required total
output, and a difference of the output of the electric motor 2 from
the required total output is provided by the output of the engine
1. During running of the vehicle at a relatively low speed, for
instance, the predominant use of the electric motor 2 and the
supplemental use of the engine 1 permit a higher degree of vehicle
running efficiency (e.g., better fuel economy). Accordingly, the
normal control data map is formulated to determine the distribution
ratio of the outputs of the engine 1 and electric motor 2, as
indicated in FIG. 5A. In this example, the engine 1 is
intermittently operated, and the output of the engine 1 varies to a
large extent. In this operating condition of the engine 1, the
catalyst deterioration detecting apparatus is not able to diagnose
the catalyst 29 with high accuracy.
[0045] Based on the finding indicated above, the distribution ratio
of the outputs of the engine 1 and electric motor 2 during the
diagnosis of the catalyst 29 is determined according to a
diagnostic control data map such that the output of the engine 1 is
held within the predetermined relatively narrow range, as indicated
in the graph of FIG. 5B, which shows an example in which the
required total output of the hybrid drive device is the same as in
the example of FIG. 5A according to the normal control data map.
According to the diagnostic control data map, the amount of change
of the output of the engine 1 is held within the predetermined
narrow range, and the change of the required total output is
attained primarily by changing the output of the electric motor 2.
To hold the output of the engine 1 within the predetermined narrow
range, the engine 1, which is held at rest for some periods of time
according to the normal control data map as indicated in FIG. 5A,
is positively operated according to the diagnostic control data map
as indicated in FIG. 5B. Thus, the engine 1 controlled according to
the diagnostic data map of FIG. 5B facilitates the diagnosis of the
catalyst 29.
[0046] In step S220 indicated above, the normal control data map is
replaced by the diagnostic control data map, to determine the
outputs of the engine 1 and electric motor 2, so that the engine 1
is operated as indicated in the graph of FIG. 5B and the diagnosis
of the catalyst 29 is initiated. Step S220 is followed by step S230
in which the air/fuel ratio of the air-fuel mixture of the engine 1
is controlled in the feedback fashion for the purpose of diagnosing
the catalyst 29 or detecting catalyst deterioration, as described
above, and the diagnostic parameters (the ratio of the length
values of the output voltage waveforms of the air/fuel ratio
sensors 23, 30, and the ratio of the surface areas enclosed by the
waveforms and the reference straight lines) are calculated. The
control of the air/fuel ratio of the air-fuel mixture is performed
by positively changing the period (or magnitude in some cases) of
variations or changes in the air/fuel ratio of the exhaust gas
introduced into the catalyst 29, in order to facilitate the
diagnosis of the catalyst 29 for determining whether the catalyst
29 is in a deteriorated functional state. The diagnostic parameters
may be any parameters in addition to (or instead of) the
above-indicated ratios of the length values and surface areas
associated with the output signals of the air/fuel ratio sensors
23, 30.
[0047] If a negative decision (NO) is obtained in step S210, that
is, if the restriction of the output of the engine 1 is not
permissible, the control process proceeds to step S240 which is the
same as the step S230. Thus, the diagnosis of the catalyst 29 is
initiated without executing step S220, that is, without restricting
the output of the engine 1. When step S210 is executed according to
the DETECTING CONDITION flag placed in the ON state, the engine 1
is placed in a condition suitable for diagnosing the catalyst 29,
so that the diagnosis of the catalyst 29 is possible on the basis
of the diagnostic parameters calculated in step S240 during the
feedback control of the air/fuel ratio of the air-fuel mixture,
without positively restricting the output of the engine 1 within
the predetermined range.
[0048] Steps S230 and S240 are followed by step S250 to determine
whether the calculated diagnostic parameters are larger than
respective threshold values. In this embodiment, in which the
above-indicated ratios of the length values and surface areas are
used, the control process proceeds to step S260 to determine that
the catalyst 29 is in a deteriorated functional state if the ratios
are higher than the threshold values. If the ratios are not higher
than the threshold values, the control process proceeds to step
S270 to determine that the catalyst 29 is in a normal operating
state. While steps S250, S260, S270 are formulated to diagnose the
catalyst 29 by simply comparing the calculated diagnostic
parameters with the threshold values, it is possible to diagnose
the catalyst 29 according to a predetermined two-dimensional or
three-dimensional data map stored in the main ECU 10 (or engine ECU
11) and on the basis of the above-indicated two ratio values and/or
any other parameter selected as desired.
[0049] The normal diagnosis of the catalyst 29 which has been
described above is implemented when the DETECTING CONDITION flag is
in the ON state, that is, when the vehicle (engine 1) is in a
condition suitable for diagnosing the catalyst 29. The compulsory
diagnosis of the catalyst 29 indicated above will now be described.
The compulsory diagnosis is implemented when the DETECTING
CONDITION flag is in the OFF state. In the compulsory diagnosis,
the engine 1 is controlled in a predetermined fashion, for the
purpose of facilitating the diagnosis of the catalyst 29.
[0050] The normal diagnosis is not initiated unless the vehicle
(engine 1) is brought into a condition suitable for the diagnosis.
Although deterioration of the catalyst 29 is normally detected by
effecting the normal diagnosis as described above, the compulsory
diagnosis permits the catalyst 29 to be diagnosed at least once
even while the vehicle is not brought into the condition suitable
for the normal diagnosis. The compulsory diagnosis is to be
initiated at a point of time as early as possible after the engine
1 is started. The normal diagnosis may follow the compulsory
diagnosis. In this case, the result of the normal diagnosis may
replace that of the compulsory diagnosis. The compulsory diagnosis
may also be effected at predetermined time intervals, or each time
the number of operating cycles or ignition cycles of the engine 1
has reached a predetermined value, for example. The compulsory
diagnosis of the catalyst 29 will be described by reference to the
flowcharts of FIGS. 6 and 7.
[0051] The routine illustrated in the flowchart of FIG. 6 is
executed cyclically (e.g., every several to several hundred
milliseconds) by the main ECU 10 according to a control program
stored in the ROM, to turn on or off a COMPULSORY DIAGNOSIS flag
depending upon whether the compulsory diagnosis should be
performed. The routine of FIG. 6 is initiated with step S300 to
determine whether predetermined basic diagnostic conditions of the
vehicle (engine 1) are satisfied. The basic diagnostic conditions
are satisfied when the temperatures of the coolant and intake air
of the engine 1 are higher than thresholds, when the battery for
accessories and the battery 8 for the electric motor 2 are placed
in a state suitable for the diagnosis, and when the catalyst 29 has
not yet been diagnosed.
[0052] If the basic diagnostic conditions are not satisfied in step
S300, or if the catalyst 29 has already been diagnosed, a negative
decision (NO) is obtained in step S300, and the control process
proceeds to step S310 to turn off the COMPULSORY DIAGNOSIS flag. If
the basic diagnostic conditions are satisfied, the control process
proceeds to step S320 to determine whether predetermined compulsory
diagnosis conditions are satisfied. These compulsory diagnosis
conditions are satisfied when the DETECTING CONDITION flag is
placed in the OFF state (see step S130 of FIG. 3), after a
predetermined time has passed after the DETECTING CONDITION flag
was turned off, and after a predetermined time has passed after the
last compulsory diagnosis was initiated and cancelled. The
determination as to whether a predetermined time has passed after
the DETECTING CONDITION flag was turned off may be made by
determining whether a predetermined time has passed after the
DETECTING CONDITION flag was turned on during the last or preceding
operation (or last trip) of the engine (or vehicle) and then turned
off, or after the ignition switch was turned on.
[0053] The DETECTING CONDITION flag placed in the OFF state means
that the normal diagnosis is not being performed. If the normal
diagnosis is being performed, the compulsory diagnosis is not
performed. After the predetermined time has passed after the
DETECTING CONDITION flag was turned off, this flag is relatively
unlikely to be turned on. In other words, immediately after the
flag is turned off, the flag is relatively likely to be turned on,
so that the normal diagnosis is relatively likely to be initiated.
In this case, the compulsory diagnosis is not performed, to wait
for the initiation of the normal diagnosis. If the predetermined
time has passed after the flag was turned off, it means that the
normal diagnosis is relatively unlikely to be initiated.
[0054] The compulsory diagnosis may be initiated and cancelled, or
interrupted, for some reason or other, as described later referring
to steps S410 and S470 in FIG. 7. After the predetermined time has
passed after the last compulsory diagnosis was initiated and
cancelled, the compulsory diagnosis if initiated is relatively
unlikely to be cancelled. In other words, immediately after the
last compulsory diagnosis was initiated and cancelled, the
compulsory diagnosis if initiated is relatively likely to be
cancelled again. In this case, the compulsory diagnosis is not
initiated.
[0055] If the compulsory diagnosis conditions are not satisfied, a
negative decision (NO) is obtained in step S320, and the control
process proceeds to step S330 to turn off the COMPULSORY DIAGNOSIS
flag. If the compulsory diagnosis conditions are satisfied, an
affirmative decision (YES) is obtained in step S320, and the
control process proceeds to step S340 to turn on the COMPULSORY
DIAGNOSIS flag. This flag is turned on or off in each cycle of
execution of the routine of FIG. 6, depending upon the operating
states of the vehicle (engine 1).
[0056] The compulsory diagnosis is carried out according to the
routine illustrated in the flowchart of FIG. 7, which is executed
along with the routine of FIG. 6 cyclically (e.g., every several to
several hundred milliseconds) according to a control program stored
in the ROM of the main ECU 10. The routine of FIG. 7 is initiated
with step S400 to determine whether the COMPULSORY DIAGNOSIS flag
is in the ON state. If a negative decision (NO) is obtained in step
S400, it means that the compulsory diagnosis of the catalyst 29
should not be performed. In this case, one cycle of execution of
the routine of FIG. 7 is terminated. If the COMPULSORY DIAGNOSIS
flag is in the ON state, an affirmative decision (YES) is obtained
in step S400, and the control process proceeds to step S410 to
determine whether it is permissible to effect the compulsory
diagnosis.
[0057] The step S410 is similar to the step S210 of FIG. 4. Under
some vehicle operating conditions in which the engine 1 is
controlled for a purpose other than the diagnosis of the catalyst
29 or any device other than the engine 1 is controlled, it is not
desirable to effect the compulsory diagnosis. In view of this, step
S410 is provided to determine whether the compulsory diagnosis is
permissible under the present condition of the vehicle (engine 1).
If an affirmative decision (YES) is obtained in step S410, the
control process proceeds to step S420 to operate the engine 1 in a
state suitable for diagnosing the catalyst 29.
[0058] In step S420, the normal control data map is replaced by a
compulsory diagnosis data map, so that the output of the engine 1
is controlled to be held within a predetermined relatively narrow
range, as described above with respect to the normal diagnosis by
reference to FIGS. 5A and 5B. If the engine 1 is at rest upon
execution of step S420, the engine 1 is started and the output of
the engine 1 is controlled to be held within the predetermined
range, depending upon the vehicle condition. If the output of the
engine 1 is outside the predetermined range upon execution of step
S420, the output of the engine 1 is controlled to become within the
predetermined range. Then, the control process proceeds to step
S430 to control the air/fuel ratio of the air-fuel mixture for the
purpose of diagnosing the catalyst 29, and calculate the diagnostic
parameters, as described above with respect to step S250.
[0059] Subsequently, the control process proceeds to step S440 to
determine whether the calculated diagnostic parameters are larger
than respective thresholds. If the diagnostic parameters are larger
than the thresholds, it means that the catalyst 29 has been
deteriorated or degraded. In this case, the control process
proceeds to step S450 to determine that the catalyst 29 is in a
deteriorated functional state. If the diagnostic parameters are not
larger than the thresholds, it means that the catalyst 29 is in a
normal state. In this case, the control process proceeds to step
S460 to determine that the catalyst 29 is normal. As described
above with respect to the normal diagnosis, it is possible to
diagnose the catalyst 29 according to a predetermined
two-dimensional or three-dimensional data map stored in the main
ECU 10 (or engine ECU 11) and on the basis of the calculated
diagnostic parameters, and any other parameter selected as
desired.
[0060] If the compulsory diagnosis is not permissible, that is, if
a negative decision (NO) is obtained in step S410, the control
process proceeds to step S470 to turn off the COMPULSORY DIAGNOSIS
flag, and terminate one cycle of execution of the routine.
[0061] While the catalyst deterioration detecting apparatus
according to the above embodiment of the invention has been
described above with reference to the accompanying drawings, it is
to be understood that the invention may be otherwise embodied. For
instance, only the normal diagnosis may be performed while the
engine 1 or vehicle is in a condition suitable for diagnosing the
catalyst 29. Namely, it is not essential to effect the compulsory
diagnosis in which the engine 1 is brought into an operating state
suitable for the diagnosis, when the engine 1 is not in a state
suitable for the normal diagnosis. However, the arrangement to
perform the compulsory diagnosis when the normal diagnosis is not
implemented is preferable in that the deterioration of the catalyst
29 can be detected with higher accuracy and at an early point of
time.
[0062] In the illustrated embodiment, when the output of the
internal combustion engine is restricted to within the
predetermined range during the diagnosis of the catalyst 29 for
detecting catalyst deterioration, the electric motor serves to
compensate for a deficiency in the total output required for
driving the vehicle, so that a sum of the outputs of the engine and
the motor becomes equal to the total required output. However, the
invention is not limited to the use of the electric motor for
reducing an amount of change of the output of the engine while
providing the required total output. For example, the amount of
change (or variation) in the output of the engine may be reduced to
some extent, by adjusting the amount of the output of the engine
consumed by an external load, such as an alternator (generator)
provided in the engine, a power steering pump, or a compressor of
an air condition of the vehicle. In this case, the external load,
such as an alternator, serves as the output adjusting device that
cooperates with the engine to provide the required total output
that is required for driving the vehicle.
[0063] In the illustrated embodiment, the apparatus is controlled
by one or more controllers (e.g., the ECUs 10 and 11), which are
implemented as a programmed general purpose computer. It will be
appreciated by those skilled in the art that the controllers can be
implemented using a single special purpose integrated circuit
(e.g., ASIC) having a main or central processor section for
overall, system-level control, and separate sections dedicated to
performing various different specific computations, functions and
other processes under control of the central processor section. The
controllers can be a plurality of separate dedicated or
programmable integrated or other electronic circuits or devices
(e.g., hardwired electronic or logic circuits such as discrete
element circuits, or programmable logic devices such as PLDs, PLAs,
PALs or the like). The controllers can be implemented using a
suitably programmed general purpose computer, e.g., a
microprocessor, microcontroller or other processor device (CPU or
MPU), either alone or in conjunction with one or more peripheral
(e.g., integrated circuit) data and signal processing devices. In
general, any device or assembly of devices on which a finite state
machine capable of implementing the procedures described herein can
be used as the controller. A distributed processing architecture
can be used for maximum data/signal processing capability and
speed.
[0064] While the invention has been described with reference to
preferred embodiments thereof, it is to be understood that the
invention is not limited to the preferred embodiments or
constructions. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements. In addition,
while the various elements of the preferred embodiments are shown
in various combinations and configurations, which are exemplary,
other combinations and configurations, including more, less or only
a single element, are also within the spirit and scope of the
invention.
* * * * *