U.S. patent application number 09/789497 was filed with the patent office on 2001-07-26 for control system for hybrid vehicle.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Kimura, Shigehito, Takashima, Hiroyuki.
Application Number | 20010009147 09/789497 |
Document ID | / |
Family ID | 26430251 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009147 |
Kind Code |
A1 |
Takashima, Hiroyuki ; et
al. |
July 26, 2001 |
Control system for hybrid vehicle
Abstract
In an electronic control for a hybrid vehicle which is driven
either by an engine or an electric motor, or both, possible
failures in an ignition system and a rotation sensor system are
detected during a period in which the engine is rotated by the
motor with no fuel supply. Only after no failure is found, the
engine is started by supplying fuel and performing ignition. Thus,
the fuel supplied to the engine is ignited without fail, and
unburned gas release to the atmosphere is surely prevented. Also,
good drivability is maintained. In case the invention is applied to
a series hybrid vehicle which is driven solely by an electric motor
powered by a battery which is charged by an electric generator
driven by an engine, the ignition system is diagnosed when the
engine is not rotating. After it is determined that there is no
failure in the ignition system, the engine is started.
Inventors: |
Takashima, Hiroyuki;
(Aichi-gun, JP) ; Kimura, Shigehito;
(Okazaki-city, JP) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
1100 N. Glebe Rd., 8th Floor
Arlington
VA
22201
US
|
Assignee: |
DENSO CORPORATION
|
Family ID: |
26430251 |
Appl. No.: |
09/789497 |
Filed: |
February 22, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09789497 |
Feb 22, 2001 |
|
|
|
09259264 |
Mar 1, 1999 |
|
|
|
Current U.S.
Class: |
123/406.14 ;
123/479; 180/65.235 |
Current CPC
Class: |
B60K 1/02 20130101; Y02T
10/7077 20130101; B60W 2710/0605 20130101; F02D 41/22 20130101;
B60W 2710/0666 20130101; Y02T 10/54 20130101; Y02T 10/62 20130101;
Y02T 10/64 20130101; B60L 2270/12 20130101; B60W 50/0205 20130101;
B60W 20/00 20130101; Y02T 10/70 20130101; B60W 20/50 20130101; B60W
10/26 20130101; B60W 2710/0616 20130101; F02P 17/00 20130101; B60L
50/16 20190201; B60L 3/0023 20130101; Y02T 10/7005 20130101; Y10S
903/903 20130101; B60L 2240/441 20130101; B60K 6/445 20130101; B60L
2240/44 20130101; B60L 2260/26 20130101; Y02T 10/7072 20130101;
B60W 10/08 20130101; Y02T 10/6286 20130101; B60K 6/28 20130101;
B60W 2050/021 20130101; Y02T 10/642 20130101; B60L 2270/142
20130101; B60L 2240/42 20130101; B60W 10/06 20130101; Y02T 10/6239
20130101; B60W 2510/0638 20130101; B60W 2710/0644 20130101; B60L
50/61 20190201; B60K 6/46 20130101; Y02T 10/40 20130101; Y02T
10/6217 20130101 |
Class at
Publication: |
123/406.14 ;
123/479 |
International
Class: |
F02P 005/15; F02D
041/22; F02M 051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 1998 |
JP |
10-88912 |
Apr 14, 1998 |
JP |
10-102824 |
Claims
What is claimed is:
1. A control system for a hybrid vehicle, the hybrid vehicle being
driven by either an electric motor or an internal combustion
engine, or by combined power of the electric motor and the internal
combustion engine according to driving conditions of the hybrid
vehicle, the internal combustion engine being initially rotated by
the electric motor in a motoring state where no fuel is supplied
and no ignition is performed, and then the internal combustion
engine being operated by supplying fuel and performing ignition
during the motoring state, the control system comprising: a
rotation sensor system for generating pulse signals in synchronism
with rotation of the engine; an ignition system for igniting fuel
supplied to the engine according to the pulse signals of the
rotation sensor system; a fuel injection system for supplying fuel
to the engine according to the pulse signals of the rotation sensor
system; means for detecting the motoring state of the engine; means
for detecting a failure in either the ingnition system or the
rotation sensor system, or both, during the motoring state; and
means for inhibiting fuel supply and ignition when the failure is
detected by the failure detecting means.
2. The control system for a hybrid vehicle as in claim 1, wherein:
the ignition system receives an ignition instruction signal during
the motoring state and generates a signal indicating an abnormal
operation of the ignition system when the ignition system does not
function normally; and thereby the failure detecting means detects
the failure in the ignition system.
3. The control system for a hybrid vehicle as in claim 1, wherein:
the failure detecting means determines whether the rotation sensor
system generates predetermined pulse signals during the motoring
state of the engine in sychronism with rotation of the engine; and
thereby the failure detecting means detects the failure in the
rotation sensor system.
4. The control system for a hybrid vehicle as in claim 1, wherein:
the motoring state detecting means determines that the engine is in
the motoring state, if the ignition system and fuel injection
system are not in operation and the engine is rotated by the
electric motor.
5. The control system for a hybrid vehicle as in claim 1, wherein:
operation of the ignition system and the fuel injection system is
temporarily inhibited when the motoring state detecting means
determines that the engine is in the motoring state; and the
ignition system and the fuel injection system are allowed to
operate after and when the failure detecting means has detected no
failure in the ignition system and the rotation sensor system.
6. A control system for a hybrid vehicle, the hybrid vehicle being
driven by an electric motor powered by a battery which is charged
by an electric generator driven by an internal combustion engine,
the control system comprising: a rotation sensor system for
generating pulse signals in sychronism with rotation of the engine;
an ignition system for igniting fuel supplied to the engine
according to the pulse signals of the rotation sensor system; a
fuel injection system for supplying fuel to the engine according to
the pulse signals of the rotation sensor system; means for
detecting a failure in the ingnition system during a period in
which no fuel is supplied to the engine; and means for inhibiting
operation of the fuel injection system when the failure is detected
by the failure detecting means.
7. The control system for a hybrid vehicle as in claim 6, wherein:
the ignition system receives an ignition instruction signal during
the period in which no fuel is supplied to the engine and generates
a signal indicating a normal operation of the ignition system when
the ignition system normally operates; the failure detecting means
determines that the ignition system includes no failure upon
receipt of the signal indicating a normal operation; and the fuel
injection system starts its operation after the determination of no
failure in the ignition system.
8. A method of detecting a failure in an ignition system of a
control system for a hybrid vehicle which is driven by either an
electric motor or an internal combustion engine, or by combined
power of the electric motor and the internal combustion engine
according to driving conditions of the hybrid vehicle, the method
comprising steps of: rotating the internal combustion engine by the
electric motor without supplying fuel to the engine; sending a
signal to the ignition system for instructing operation thereof;
determining whether the ignition operation is normally performed
according to the signal; and inhibiting fuel supply to the engine
if the ignition operation is abnormal, or permitting fuel supply to
the engine to start the engine if the ignition operation is
normal.
9. A method of detecting a failure in an rotation sensor system of
a control system for a hybrid vehicle which is driven by either an
electric motor or an internal combustion engine, or by combined
power of the electric motor and the internal combustion engine
according to driving conditions of the hybrid vehicle, the method
comprising steps of: rotating the internal combustion engine by the
electric motor without supplying fuel to the engine; determining
whether the rotation sensor system outputs predetermined pulse
signals in synchronism with rotation of the engine; and inhibiting
fuel supply to the engine if the rotation sensor system does not
output the predetermined pulse signals, or permitting fuel supply
to the engine to start the engine if the rotation sensor system
outputs the predetermined pulse signals.
10. A method of detecting a failure in an ignition system of a
control system for a hybrid vehicle which is driven by an electric
motor powered by a battery which is charged by an electric
generator driven by an internal combustion engine, the method
comprising steps of: sending a signal to the ignition system for
instructing ignition operation, while the engine is not operating;
determining whether the ignition operation is normally performed
according to the signal; and inhibiting fuel supply to the engine
if the ignition operation is abnormal, or permitting fuel supply to
the engine to start the engine if the ignition operation is normal.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims benefit of
priority of Japanese Patent Applications No. Hei-10-88912 filed on
Apr. 1, 1998, and No. Hei-10-102824 filed on Apr. 14, 1998, the
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a hybrid vehicle having
both an internal combustion engine and an electric motor for
driving and, more particularly, to a technique for detecting both a
failure in an ignition system (ignition system failure) of an
internal combustion engine mounted on the hybrid vehicle and a
failure in a rotation sensor system of the internal combustion
engine.
[0004] 2. Description of Related Art
[0005] Hitherto, a vehicle is driven by transmitting a rotation
output generated by an internal combustion engine to wheels
(driving wheels) and exhaust gases and noises occur upon driving.
An electric vehicle driven by an electric motor has therefore been
proposed. The electric vehicle, however, has a problem that a
travel distance is short because only an electric power
preliminarily charged in a battery is used.
[0006] In recent years, a hybrid vehicle using both an internal
combustion engine and an electric motor for driving has been
practically used. In the hybrid vehicle, a generator is driven by
an output of the internal combustion engine, power generated by the
generator is charged into a battery, an electric motor is rotated
by the electric power charged in the battery or the electric power
from the generator, and the rotation output of the electric motor
is transmitted to driving wheels.
[0007] Various types of the hybrid vehicles of this kind have been
proposed such as a series type in which the internal combustion
engine drives only the generator and the wheels are driven only by
the electric motor and a parallel-series type which can apply a
driving force to the wheels by both of the internal combustion
engine and the electric motor. In the series hybrid vehicle
(hereinbelow, referred to as an "SHV"), the internal combustion
engine is mechanically separated from the driving system. When
power generation is considered to be unnecessary in the cases such
as a vehicle halt (the vehicle speed= zero) and during a driving in
a state where the battery is sufficiently charged, the operation of
the internal combustion engine is stopped. When a charge amount of
the battery becomes lower than a predetermined amount in
association with driving, the internal combustion engine is started
by a separately provided starting motor or the like and is made
operative and the battery is charged.
[0008] A parallel-series hybrid vehicle (hereinbelow, referred to
as a "PSHV") has a power transmitting mechanism such as a magnet
clutch and a planetary gear unit for transmitting both an output of
the internal combustion engine and an output of the electric motor
to the drive shaft for driving the wheels. Since the output of the
internal combustion engine can be used not only for power
generation but also for directly driving the wheels together with
the output of the electric motor, energy transmission efficiency is
high and the PSHV is especially considered to be promising.
[0009] In the PSHV, usually, the operation of both of the internal
combustion engine and the electric motor is stopped when the
vehicle comes to a halt. When the driver operates the accelerator
pedal, only the electric motor is driven first to start the
vehicle. In such a state, the internal combustion engine is in a
"motoring state" where the fuel is not injected and the engine is
rotated by the output of the electric motor. In the state where the
fuel is not injected to the internal combustion engine, ignition to
the engine is also stopped. After that, when the vehicle speed
exceeds a predetermined value (for example, 20 km/h), the fuel
injection and the ignition to the internal combustion engine are
started and the internal combustion engine starts in a manner,
so-called "pushed start." After that, both the output of the
internal combustion engine and that of the electric motor are
controlled according to the driving load of the vehicle and the
charging state of the battery. When the vehicle speed becomes below
the predetermined value, the fuel injection and the ignition to the
internal combustion engine are stopped, the internal combustion
engine enters the "motoring state" again, and the vehicle is driven
by using only the output of the electric motor.
[0010] In the internal combustion engine, an ignition system for
igniting the fuel and a rotation sensor system are mounted. When a
failure occurs in the ignition system, unburned gases are released
from an exhaust pipe to the atmosphere in association with the fuel
injection. When a failure occurs in the rotation sensor system,
injection and ignition timing is deviated, so that unburned gases
are released and the drivability of the vehicle deteriorates.
Consequently, hitherto, in a control unit for controlling the
internal combustion engine and the electric motor of the hybrid
vehicle of this kind, in a manner similar to a common vehicle
having only the internal combustion engine, whether or not the
ignition system normally operates according to an ignition
instruction signal generated from the control unit itself is
monitored in the engine operating state where the fuel injection
and the ignition to the internal combustion are performed. Whether
a pulse signal is normally generated from the rotation sensor
system or not is also checked. When a failure is detected by such
failure diagnosis, the fuel injecting operation and the igniting
operation are stopped to thereby stop the operation of the internal
combustion engine.
[0011] The conventional control unit is, however, insufficient to
achieve the inherent object of the hybrid vehicle, namely,
suppression of environmental pollution. More specifically, in the
conventional control unit, since failure diagnosis is performed to
both the ignition system and the rotation sensor system when the
internal combustion engine is in the operating state, deterioration
in the exhaust gases (release of unburned gases) cannot be avoided
for a period of time from the detection of a failure until the stop
of the fuel injection. Moreover, in the failure diagnosis of this
kind, generally, occurrence of a failure is determined for the
first time after a certain number of failures are detected in order
to avoid erroneous detection. Consequently, due to the delay in the
failure detection, unburned gases are released more.
[0012] Especially, in case of the PSHV, the output shaft of the
internal combustion engine and that of the electric motor are
mechanically connected via the power transmitting mechanism. The
internal combustion engine is started in a "pushed start" manner by
injecting fuel and igniting thereto at proper timing which matches
the motoring speed. Upon starting the internal combustion engine in
the PSHV, a larger amount of fuel is injected. Therefore, when the
ignition system or the rotation sensor system is faulty, a larger
amount of unburned gases is released, and the drivability is also
adversely affected. Moreover, the emission of the unburned gases
may cause an irreversible damage to a catalytic converter mounted
on the vehicle for purifying the exhaust gases.
SUMMARY OF THE INVENTION
[0013] The present invention is made in view of the problems
described above, and the object of the present invention is to
certainly prevent both the release of unburned gases due to a
failure in either the ignition system or the rotation sensor system
of the internal combustion engine and deterioration of the
drivability of the hybrid vehicle.
[0014] In a parallel-series hybrid vehicle (PSHV), the vehicle is
driven by either an electric motor or an internal combustion
engine, or both according to driving conditions of the vehicle.
Usually, the vehicle is driven only by the motor when the vehicle
is starting and driven at a low speed. When the vehicle is driven
at a high speed or a high power is required, the vehicle is driven
by both of the motor and the engine. An electric generator is also
included in the driving system and is driven by the engine to
charge a battery which in turn drives the motor. The driving system
is electronically controlled by a control system mounted in the
vehicle.
[0015] To initiate the engine operation in such a hybrid vehicle,
the engine is first driven by the motor without supplying fuel to
the engine and without performing ignition. In other words, the
engine is started in a so-called "motoring state." According to the
present invention, an ignition system for igniting fuel in the
engine and a rotation sensor system for generating pulse signals in
synchronism with rotation of the engine are diagnosed during the
motoring state to detect possible failures in those systems. The
ignition system is checked by sending a checking signal thereto. If
a signal indicating a normal operation of the ignition system is
generated, it is determined that there is no failure in the system,
and if not it is determined that there is failure in the system.
For the rotation sensor system, it is determined that there is no
failure if predetermined pulse signals are generated in synchronism
with the engine rotation.
[0016] If any failure is found either in the ignition system or in
the rotation sensor system, or in both, during the motoring state,
fuel supply to the engine is inhibited, thereby making the engine
inoperative. In this occasion the hybrid vehicle may be driven only
by the motor to drive back home using a limp-home function. Also,
it is inhibited to resume fuel supply and ignition during the
motoring state before the failure detection is completed. If no
failure is found, fuel supply and ignition are performed to start a
normal operation of the engine.
[0017] In the above-manner, unburned gases are surely prevented
from being emitted into the atmosphere from the engine, and
drivability of the hybrid vehicle is maintained in a good
condition.
[0018] The present invention is applicable also to a hybrid vehicle
which is driven solely by an electric motor that is powered by a
battery charged from an electric generator driven by an internal
combustion engine (a series hybrid vehicle). In this case, the
ignition system is diagnosed when the engine is not rotating
because there is no motoring state in the series hybrid vehicle.
After it is determined that there is no failure in the ignition
system under the diagnosis, the engine is put into operation by
supplying fuel thereto. Therefore, it is assured that the ignition
is normally performed, and release of unburned gases from the
engine is prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a block diagram showing a driving system of a
hybrid vehicle;
[0020] FIG. 2 is a block diagram showing an ignition system for an
engine of the hybrid vehicle;
[0021] FIG. 3 is a flowchart showing a control process of a
motor-generator used in the hybrid vehicle;
[0022] FIG. 4 is a graph showing a relation between engine speed
and torque for obtaining optimum fuel consumption and exhaust
emission;
[0023] FIG. 5 is a flowchart showing a control process for setting
an engine output at a target level;
[0024] FIG. 6A is a flowchart showing a control process of the
ignition system;
[0025] FIG. 6B is a flowchart showing a control process of a fuel
injection system;
[0026] FIG. 7 is a flowchart showing a process for detecting a
failure in the ignition system;
[0027] FIG. 8 is a flowchart showing another control process of the
motor-generator used in the hybrid vehicle; and
[0028] FIG. 9 is a flowchart showing a process for detecting a
failure in a rotation sensor system in the hybrid vehicle
system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] (First Embodiment)
[0030] A first embodiment of the present invention will be
described hereinbelow with reference to FIGS. 1 to 7. FIG. 1 is a
schematic block-diagram of a hybrid vehicle to which the invention
is applied. As shown in FIG. 1, the hybrid vehicle is a PSHV and
comprises a four-cylinder internal combustion engine 1, two
motor-generators (hereinbelow, referred to as M/Gs) 3 and 5 each
operating as electric motor or generator, and a planetary gear unit
7 as a power transmitting mechanism.
[0031] The output shaft (crank shaft) 1a of the engine 1 is
connected to a ring gear R of the planetary gear unit 7, the output
shaft 3a extending from a rotor of the M/G 3 is connected to a sun
gear SN of the planetary gear unit 7, and the output shaft 5a
extending from a rotor of the M/G 5 is connected to a carrier CR of
the planetary gear unit 7. The other end of the output shaft 5a
opposite to that connected to the carrier CR is connected to a
drive shaft 8 for driving wheels 11R and 11L in the vehicle. A
driving force is transmitted from the drive shaft 8 to the wheels
11R and 11L via a differential gear 9.
[0032] Further, the hybrid vehicle of the embodiment comprises: a
main battery 12 for charging electric power generated when each of
the M/Gs 3 and 5 operates as a generator and for supplying the
electric power when each of the M/Gs 3 and 5 operates as an
electric motor; a motor-generator electronic control unit
(hereinbelow, referred to as an M/G ECU) 17 for controlling both
the M/Gs 3 and 5 via two inverters 13 and 15; and an engine
electronic control unit (hereinbelow, referred to as an engine ECU)
19 for controlling the engine 1 while transmitting and receiving
control information to/from the M/G ECU 17.
[0033] On the basis of an instruction from the M/G ECU 17, the
inverter 13 converts a dc power of the main battery 12 to a
three-phase ac power and makes the M/G 3 operate as an electric
motor. On the basis of an instruction from the M/G ECU 17, the
inverter 13 also makes the M/G 3 operate as a generator, converts
the generated ac power to a dc power, and allows the dc power to be
charged into the main battery 12. Similarly, on the basis of an
instruction from the M/G ECU 17, the inverter 15 converts the dc
power of the main battery 12 to the three-phase ac power and makes
the M/G 5 operate as a generator. On the basis of an instruction
from the M/G ECU 17, the inverter 15 also makes the M/G 5 operate
as a generator, converts the ac power to the dc power, and allows
the dc power to be charged into the battery 12. When one of the two
M/Gs 3 and 5 operates as an electric motor and the other operates
as a generator, the M/G operating as an electric motor can be
driven by the power not only from the main battery 12 but also from
the M/G operating as a generator.
[0034] On the other hand, a throttle valve 23 for regulating an
intake air volume (further, an output of the engine 1) is provided
in an intake path 21 of the engine 1. The opening angle of the
throttle valve 23 (hereinbelow, referred to as a throttle opening
angle) is regulated by a DC motor 25 serving as an actuator.
[0035] Around the engine 1, an injector (electromagnetic fuel
injection valve) 27 for injecting fuel into each of the cylinders
in accordance with a drive signal from the engine ECU 19 and an
ignition system 29 for igniting the fuel for each cylinder in
accordance with an ignition instruction signal from the engine ECU
19 are provided. Although the injectors 27 and the ignition system
29 are correspondingly provided to the respective cylinders of the
engine 1, only one each is shown in FIG. 1.
[0036] Further, the system includes: a rotational angle sensor 31
for generating a pulse signal each time the output shaft 1a of the
engine 1 rotates by a predetermined angle as a rotation sensor
system for sensing a rotational angle of the output shaft 1a, that
is, the rotational angle .theta.C of the crank shaft of the engine
1 (hereinbelow, referred to as a crank rotational angle), piston
positions, an actual rotational speed NEn of the engine 1, and the
like; and a cylinder identifying sensor 32 for generating a pulse
signal for cylinder identification each time the output shaft 1a is
in a predetermined rotational angle position. The pulse signals
from the rotational angle sensor 31 and the cylinder identifying
sensor 32 are supplied to the engine ECU 19.
[0037] On the other hand, the M/Gs 3 and 5 have rotor position
sensors 33 and 35, respectively. Each of the sensors senses a
relative rotational angle of the rotor with respect to the stator
(hereinbelow, called a rotor rotational angle .theta.R) and the
rotational speed of the rotor. Signals from the rotor position
sensors 33 and 35 are supplied to the M/G ECU 17.
[0038] The hybrid vehicle system also includes a voltage sensor 37
for sensing an actual voltage V of the main battery 12 and a
current sensor 39 for sensing an actual current I flowing in the
main battery 12. The signals from the sensors 37 and 39 are also
supplied to the M/G ECU 17. Further, although not shown, the M/G
ECU 17 also receives signals from various sensors for sensing the
driving conditions of the vehicle such as an accelerator sensor for
sensing a stroke PA of an accelerator pedal (hereinbelow, referred
to as an accelerator stroke) operated by a driver of the vehicle, a
speed sensor for sensing a driving speed (namely, vehicle speed v)
of the vehicle, and a brake sensor for sensing that the brake pedal
of the vehicle is operated. In the embodiment, the dc voltage of
the main battery 12 is decreased to a predetermined power supply
voltage (for example, 12V) by a DC-DC converter 41 and is supplied
to a sub battery 43. When an ignition switch 45 (refer to FIG. 2)
is turned on, the M/G ECU 17 and the engine ECU 19 are operated by
the power from the sub battery 43.
[0039] As shown in FIG. 2, the ignition system 29 comprises: a
spark plug 47 for producing a spark in a cylinder of the engine 1;
an ignition coil 49 for converting the power supplied from the sub
battery 43 via the ignition switch 45 to a power for ignition of
the spark plug 47; and an igniter 51 for allowing the ignition coil
49 to generate the power for ignition in response to an ignition
instruction signal IGt from the engine ECU 19 and for sending back
an ignition normal state signal IGf to the engine ECU 19 when it is
regarded that the ignition using the spark plug 47 is normally
performed.
[0040] The igniter 51 comprises: a transistor 51a for flowing a
current (primary current) I1 to the primary coil of the ignition
coil 49; a drive circuit 51b for turning on the transistor 51a in
response to the ignition instruction signal IGt from the engine ECU
19; a resistor 51c for current detection provided in a current path
of the primary current I1 of the ignition coil 49; a constant
current control circuit 51d for detecting the primary current I1
flowing through the current detecting resistor 51c and controlling
the primary current I1 to a constant value; an ignition monitoring
circuit 51e for generating the ignition normal state signal IGf to
the engine ECU 19 when the constant current control circuit 51d
detects that the primary current I1 larger than a predetermined
value flows; and a lock preventing circuit 51f for determining that
the ignition instruction signal IGt remains to be generated for
some reason when the constant current control circuit 51d detects
that the primary current I1 keeps flowing for a specified time or
longer, and for forcedly turning off the transistor 51a.
[0041] In the ignition system 29, the transistor 51a of the igniter
51 is turned on or off in accordance with the ignition instruction
signal IGt from the engine ECU 19. When the transistor 51a is
turned on, the primary current I1 flows in the ignition coil 49.
Subsequently, when the transistor 51a is turned off, a high voltage
is generated in the secondary coil of the ignition coil 49 and the
high voltage is supplied to the spark plug 47. Then, a spark is
produced by the spark plug 47 and the ignition for the cylinder is
carried out. When the primary current I1 flows in the ignition coil
49 as mentioned above, the ignition normal state signal IGf is
outputted from the ignition monitoring circuit 51e of the igniter
51 to the engine ECU 19.
[0042] On the contrary, for example, when the ignition coil 49 or
the igniter 51 is failed or a wire is cut, the ignition normal
state signal IGf is not outputted from the igniter 51 to the engine
ECU 19. When the ignition instruction signal IGt is delivered but
the ignition normal state signal IGf is not returned from the
igniter 51, the engine ECU 19 can therefore determine that the
ignition to the cylinder cannot be performed (that is, the ignition
system 29 does not operate normally).
[0043] In such a hybrid vehicle system described above, the driving
force is transmitted from the output shaft 5a of the M/G 5 using
the main battery 12 as a power supply source to the wheels 11R and
11L via the drive shaft 8 and the differential gear 9. As mentioned
above, since the output shaft 5a of the M/G 5 is connected to the
output shafts 3a and 1a of the M/G 3 and the engine 1 via the
planetary gear unit 7, the driving force to the wheels 11R and 11L
or a deceleration force from the wheels 11R and 11L is shared among
the M/Gs 3 and 5 and the engine 1. In other words, the output of
the engine 1 and the outputs of the M/Gs 3 and 5 are added by the
planetary gear unit 7 and are transmitted via the drive shaft 8 and
the differential gear 9 to the wheels 11R and 11L.
[0044] On the basis of the charge state of the main battery 12, the
gear ratio of the planetary gear unit 7, and the operating
conditions of the vehicle (vehicle speed v, accelerator stroke PA,
and the like) sensed by the vehicle sensor, the accelerator sensor,
and the like, the M/G ECU 17 determines the rotational speed and
output torque (an output torque when the M/G operates as an
electric motor and a regenerative torque when the M/G operates as a
generator) of each of the M/Gs 3 and 5 to control the three-phase
alternate current supplied to the M/Gs 3 and 5 by the inverters 13
and 15. The M/G ECU 17 also determines the target outputs (that is,
a target output torque TRQm and a target rotational speed NEm) of
the engine 1 so that the fuel consumption and emission of the
engine 1 become optimum. Further, the M/G ECU 17 controls the
outputs of the M/Gs 3 and 5 so that the determined target torque
TRQm is supplied as a load to the output shaft 1a of the engine
1.
[0045] The engine ECU 19 controls the fuel injection to the engine
1 and the ignition timing in accordance with the target outputs
instructed by the M/G ECU 17, and controls the throttle opening
angle by driving the DC motor 25 so that the actual rotational
speed NEn of the engine 1 detected on the basis of a signal from
the rotational angle sensor 31 becomes equal to the target
rotational speed NEm instructed by the M/G ECU 17. Consequently,
the output of the engine 1 is controlled to the target output
determined by the M/G ECU 17.
[0046] Under such operations of the M/G ECU 17 and the engine ECU
19, the M/Gs 3 and 5 and the engine 1 are controlled as follows.
Specifically, when the vehicle is stopped (vehicle speed v is
zero), the M/G ECU 17 and the engine ECU 19 stop the operation of
the engine 1 and the M/Gs 3 and 5. When it is sensed that the
accelerator pedal is depressed, first, one or la: both of the M/Gs
3 and 5 is/are operated as an electric motor and the vehicle is
started by the output of the electric motor. In such a state, the
engine 1 enters the motoring state where the fuel is not injected
and the engine 1 is rotated by the outputs of the M/Gs 3 and 5.
[0047] When the vehicle speed v exceeds a predetermined value (20
km/h, for example), the fuel injection and the ignition to the
engine 1 are started and the engine 1 is started in the "pushed
start" manner. After that, the engine 1 and the M/Gs 3 and 5 are
controlled in various power balance patterns. For example, when the
main battery 12 is charged with a predetermined amount of power or
more and the driving load is small, the M/G 5 is operated as an
electric motor, and the vehicle is driven by the output of the M/G
5. The M/G 3 is operated as a generator by using the output of the
engine 1, and the main battery 12 is charged with the power of the
M/G 3. When the driving load becomes large in such a state, the
driving force which is insufficient only by the output of the M/G 5
is compensated with the output of the engine 1. On the other hand,
when the predetermined amount or a larger amount of power in the
main battery 12 is discharged and the charged power is decreased,
the vehicle is driven by the output of the engine 1 via the M/G 5,
and the main battery 12 is charged with the power of the M/G 3 by
using the remaining output of the engine 1.
[0048] When the vehicle speed v becomes below 20 km/h, the fuel
injection and the ignition to the engine 1 are stopped to bring the
engine 1 into the motoring state, and the vehicle is driven only by
the output of one or both of the M/Gs 3 and 5.
[0049] Processes executed by the M/G ECU 17 and the engine ECU 19
will now be described with reference to FIGS. 3 to 7. When the
ignition switch 45 is turned on and the operation is started, the
M/G ECU 17 repeatedly executes the processes of FIG. 3 in order to
set the target output of the engine 1 (the target torque TRQm and
the target rotational speed NEm) and to control both the M/Gs 3 and
5. FIG. 3 shows in detail the processes for controlling the M/G 3
and those for controlling the M/G 5 will be described
hereinafter.
[0050] As shown in FIG. 3, when the M/G ECU 17 starts execution of
the process, a balance Pn between charge and discharge of the main
battery 12 is calculated in step (hereinbelow, simply described as
"S") 100. The charge/discharge balance Pn is calculated by
integrating the product of the voltage V and the current I of the
main battery 12 detected on the basis of the signals from the
voltage sensor 37 and the current sensor 39 with respect to time
from the previous execution of the process to the execution of the
present time.
[0051] In S110, the driving conditions of the vehicle such as the
accelerator stroke PA and the vehicle speed v are detected on the
basis of signals from the accelerator sensor, the vehicle speed
sensor, and the like.
[0052] In S120, the target output of the engine 1 is set in
accordance with the charge/discharge balance Pn (that is, the
charging state of the main battery 12) calculated in S100 and the
driving conditions of the vehicle such as the accelerator stroke PA
and the vehicle speed v detected in S100, so that, for instance,
the larger the accelerator stroke PA is or the smaller the charge
amount of the main battery 12 is, the larger the output of the
engine 1 becomes. Further, the target torque TRQm and the target
rotational speed NEm of the engine 1 to achieve the set target
output are set on the basis of an optimum fuel consumption and
emission curve H shown in FIG. 4. The set target torque TRQm and
target rotational speed NEm are transmitted to the engine ECU 19.
The engine ECU 19 executes a process which will be described
hereinafter, thereby controlling the engine 1 on the basis of the
target torque TRQm and the target rotational speed NEm from the M/G
ECU 17.
[0053] The optimum fuel consumption and emission curve H
illustrated in FIG. 4 shows the relation between the output torque
(TRQ) and the rotational speed (NE) of the engine 1 for realizing
the optimum fuel consumption and emission of the engine 1 and is
stored as data in a ROM (not shown) in the M/G ECU 17. In S120, the
output torque and the rotational speed on the optimum fuel
consumption and emission curve H which can achieve the set target
output are set as the target torque TRQm and the target rotational
speed NEm. Curves G in FIG. 4 denote equivalent fuel consumption
curves of the engine 1. The more the curve G is positioned in the
center of FIG. 4, the fuel consumption is lower.
[0054] In S130, the M/G ECU 17 checks whether the target output set
in S120 is "0" or not. When the target output is "0", an injection
and ignition cut request XCUT for instructing that the fuel
injection and the ignition to the engine 1 are stopped is set in
the ON state (logical value 1) for instructing the stop and is
transmitted to the engine ECU 19. On the contrary, if the target
output set in S120 is not "0", the processing routine advances to
S145 where the injection and ignition cut request XCUT is set in
the OFF state (logical value 0) for not instructing the stop of the
fuel injection and ignition, and the resultant data is transmitted
to the engine ECU 19. To be specific, when the vehicle speed v is
equal to or lower than 20 km/h, the fuel injection and the ignition
to the engine 1 are not carried out as mentioned above, and the
target output of the engine 1 is set at "0" in S120. In such a
case, the injection and ignition cut request XCUT is set in the ON
state and transmitted to the engine ECU 19.
[0055] After performing the process of S140 or S145, the M/G ECU 17
executes the following processes of S150 to S195, thereby
calculating an exciting current determining the power efficiency
and a torque current determining the output torque with respect to
the M/G 3. Also, the M/G ECU 17 supplies a three-phase alternate
current according to the exciting current and the torque current to
an exciting coil of the M/G 3, thereby controlling the rotation of
the M/G 3. More specifically, in S150, the target rotational speed
NMm of the M/G 3 is calculated based on a formula "f1"
preliminarily stored in the ROM, using the charge/discharge balance
Pn calculated in S100 and the driving conditions of the vehicle
such as the accelerator stroke PA and the vehicle speed v detected
in S110. In S160, a target torque current IQm of the M/G 3 is
calculated based on a function "f2" preliminarily stored in the
ROM, using the charge/discharge balance Pn calculated in S100, the
driving conditions of the vehicle such as the accelerator stroke PA
and the vehicle speed v detected in S110 and the target rotational
speed NMm calculated in S150. The formulae f1 and f2 are made on
the basis of the gear ratio of the planetary gear unit 7, the power
capacity of the main battery 12, and other relating factors.
[0056] In the following S170, on the basis of the signal from the
rotor position sensor 33, the actual rotational speed NMn of the
M/G 3 is detected. In S180, a control exciting current IMs used for
controlling the M/G 3 is calculated based on a formula "f3"
preliminarily stored in the ROM, using the rotational speed NMn of
the M/G 3 detected in S170. In S190, on the basis of the signal
from the rotor position sensor 33, the rotor rotational angle
.theta.R of the M/G 3 is detected. In S195, on the basis of the
control exciting current IMs of the M/G 3 calculated in S180, the
target torque current IQm of the M/G 3 calculated in S160, and the
rotor rotational angle .theta.R of the M/G 3 detected in S190, the
three-phase alternate current to be supplied to the M/G 3 is
calculated. An instruction is given to the inverter 13 so that the
three-phase alternate current is supplied to the M/G 3. After that,
the processing routine returns to the process of S100.
[0057] Although not shown, in order to control the M/G 5, the M/G
ECU 17 also executes processes similar to those of S150 to S195 in
FIG. 3 with respect to the M/G 5. More specifically, the target
rotational speed NMm of the M/G 5 is calculated based on a formula
"f1'" preliminarily stored in the ROM, using the charge/discharge
balance Pn calculated in S100 and the driving conditions of the
vehicle such as the accelerator stroke PA and the vehicle speed v
detected in S110. Further, the target torque current IQm of the M/G
5 is calculated based on a formula "f2'" preliminarily stored in
the ROM, using the charge/discharge balance Pn calculated in S100,
the driving conditions of the vehicle such as the accelerator
stroke PA and the vehicle speed v detected in S110, and the
calculated target rotational speed NMm of the M/G 5. Subsequently,
the actual rotational speed NMn of the M/G 5 is detected on the
basis of the signal from the rotor position sensor 35. The exciting
current IMs for controlling the M/G 5 is calculated based on a
formula "f3'" preliminarily stored in the ROM, using the detected
rotational speed NMn of the M/G 5. On the basis of the signal from
the rotor position sensor 35, the rotor rotational angle .theta.R
of the M/G 5 is detected. On the basis of the detected rotor
rotational angle .theta.R, the calculated control exciting current
IMs of the M/G 5, and the target torque current IQm, the
three-phase alternate current to be supplied to the M/G 5 is
calculated. An instruction is given to the inverter 15 so that the
three-phase alternate current is supplied to the M/G 5.
[0058] On the other hand, after the ignition switch 45 is turned
on, the engine ECU 19 repeatedly executes the process of FIG. 5
every predetermined time so as to control the output of the engine
1 to be equal to the target output determined by the M/G ECU 17. To
be more specific, in S200, the target rotational speed NEm and the
target torque TRQm which are transmitted from the M/G ECU 17 are
received. In S210, the actual rotational speed NEn of the engine 1
is detected on the basis of the signal from the rotational angle
sensor 31. In S220, the DC motor 25 is driven to control the
throttle opening angle so that the actual rotational speed NEn of
the engine 1 detected in S210 becomes equal to the target
rotational speed NEm received in S200. Further, in S230 and S240,
on the basis of the target torque TRQm received in S200, the
present throttle opening angle controlled in S220 (that is, the
intake air volume of the engine 1), the actual rotational speed NEn
of the engine 1, the ignition timing and the fuel injection amount
of the engine 1 are calculated, respectively. After that, the
process is once finished. When new target rotational speed NEm and
target torque TRQm are not transmitted from the M/G ECU 17 at the
time of execution of S200, the routine immediately advances to
S210. Then, the processes of S220 to S240 are executed by using the
latest target rotational speed NEm and target torque TRQm which are
received at the previous time.
[0059] Each time the crank rotational angle .theta.C detected on
the basis of the signal from the rotational angle sensor 31 becomes
the predetermined angle, the engine ECU 19 executes ignition
controlling process of FIG. 6A and an injection controlling process
of FIG. 6B. The ignition and the fuel injection to the engine 1 are
carried out on the basis of the ignition timing and the fuel
injection amount calculated in S230 and S240 of FIG. 5. More
specifically, as shown in FIG. 6A, when the execution of the
ignition controlling process is started, the engine ECU 19 checks
in S300 whether the injection and ignition cut request XCUT
transmitted from the M/G ECU 17 as mentioned above is in the ON
state (logical value 1) or not. If the injection and ignition cut
request XCUT is not in the ON state, whether an operation
inhibition flag XSTOP indicating inhibition of the fuel injection
and ignition to the engine 1 is in the ON state (logical value 1
indicative of inhibition) is checked in S310. When the operation
inhibition flag XSTOP is not in the ON state, in S320, the ignition
instruction signal IGt is outputted to the igniter 51 of the
ignition system 29 at the ignition timing calculated in S230 in
FIG. 5 to perform the ignition to the engine 1. After that, the
ignition controlling process is finished.
[0060] On the contrary, when it is determined in S300 that the
injection and ignition cut request XCUT is in the ON state (YES in
S300) or when it is determined in S310 that the operation
inhibition flag XSTOP is in the ON state (YES in S310), the
ignition controlling process is immediately finished without
performing the ignition to the engine 1.
[0061] As shown in FIG. 6B, when the execution of the injection
controlling process is started, in S400, a check is made to see
whether or not the injection and ignition cut request XCUT from the
M/G ECU 17 is in the ON state (logical value 1). When the injection
and ignition cut request XCUT is not in the ON state, in S410,
whether the operation inhibition flag XSTOP is in the ON state
(logical value 1) or not is checked. If the operation inhibition
flag XSTOP is not in the ON state, in S420, a drive signal is
outputted to the injector 27 for a period of time corresponding to
the fuel injection amount calculated in S240 in FIG. 5 and the fuel
is injected to the engine 1. After that, the injection controlling
process is finished. On the contrary, when it is determined that
the injection and ignition cut request XCUT is in the ON state in
S400 (YES in S400) or when it is determined that the operation
inhibition flag XSTOP is in the ON state in S410 (YES in S410), the
injection controlling process is immediately finished without
injecting the fuel to the engine 1.
[0062] The engine ECU 19 executes an ignition system failure
detecting process shown in FIG. 7 to detect the failure and to
perform a fail-safe operation when the failure is detected. To be
more specific, as shown in FIG. 7, when the ignition switch 45 is
turned on and the operation is started, in S500, the engine ECU 19
initializes the operation inhibition flag XSTOP, which is referred
to in S310 of the ignition controlling process and in S410 of the
injection control process, to the ON state (logical value 1),
thereby inhibiting the execution of the fuel injection and ignition
to the engine 1. The engine ECU 19 also initializes a failure
diagnosis completion flag XCHK indicating whether the failure
diagnosis of the ignition system 29 has been completed or not to
the OFF state (logical value 0) indicative of incompletion.
[0063] In S510, whether or not the injection and ignition cut
request XCUT from the M/G ECU 17 is in the ON state is checked. If
the injection and ignition cut request XCUT is in the ON state, it
is determined that the engine is in the state where the fuel
injection and ignition to the engine 1 are not carried out by the
ignition controlling process of FIG. 6A and the injection
controlling process of FIG. 6B, and the processing routine advances
to S520. In S520, whether the engine 1 is rotating or not (that is,
whether the actual rotational speed NEn of the engine 1 is larger
than "0" or not) is checked.
[0064] Whether the engine 1 is rotating or not can be checked on
the basis of either a signal from the rotational angle sensor 31 or
information indicating whether the engine 1 is rotating or not
provided by the M/G ECU 17 since the M/G ECU 17 can determine
whether the engine 1 is rotating or not from the rotating state of
the M/Gs 3 and 5 which are controlled by itself.
[0065] When the rotation of the engine 1 is detected in S520, it is
determined that the engine 1 is in the motoring state where the
fuel injection and the ignition to the engine 1 are not executed
and the engine 1 is rotated by the outputs of the M/Gs 3 and 5.
Then the processing routine advances to S530 and whether the
failure diagnosis completion flag XCHK is in the ON state (logical
value 1) or not is checked. If the failure diagnosis completion
flag XCHK is not in the ON state (in the OFF state), it is
determined that the failure diagnosis of the ignition system 29 has
not been completed yet. The routine progresses to S540 where the
operation inhibition flag XSTOP is set in the ON state. After that,
in S550, the ignition instruction signal IGt is outputted once each
time to the igniter 51 in the ignition system 29 of each cylinder.
In a manner similar to S320 of the ignition controlling process, in
S550, the ignition instruction signal IGt is outputted sequentially
at timings synchronized with the crank rotational angle .theta.C of
the engine 1 in each cylinder.
[0066] Further, in S560, in response to the ignition instruction
signal IGt generated in S550, by checking whether or not the
ignition normal state signal IGf is returned from the igniter 51 of
each cylinder, whether the ignition system 29 normally operates in
response to the ignition instruction signal IGt or not is
determined. When it is determined that the ignition system 29 is
normal, the routine advances to the next S570. In S570, the
operation inhibition flag XSTOP is set into the OFF state (logical
value 0) to permit the fuel injection and the ignition to the
engine 1 by the execution of the ignition controlling process and
the injection controlling process.
[0067] On the contrary, when it is determined in S560 that the
ignition system 29 is not normal (that is, when the ignition normal
state signal IGf is not returned from the igniter 51), the routine
advances to S580 where a failure displaying process such as turn-on
of a malfunction warning lamp arranged in a meter panel in the
vehicle or display of a message notifying of a failure of the
engine 1 on a display in the vehicle is performed. In S590, a
limp-home request is transmitted to the M/G ECU 17. The limp-home
request is a request for shifting the operation mode of the M/G ECU
17 to the control mode (limp-home mode) at the time of fail-safe
operation for driving the vehicle only by the outputs of the M/Gs 3
and 5. After transmitting the limp-home request to the M/G ECU 17
in S590 or after setting the operation inhibition flag XSTOP into
the OFF state in S570, the routine advances to S600 where the
failure diagnosis completion flag XCHK is set into the ON state.
After that, the routine is returned to S510.
[0068] When it is determined in S510 that the injection and
ignition cut request XCUT from the M/G ECU 17 is not in the ON
state (NO in S510), the routine advances to S610 where the failure
diagnosis completion flag XCHK is set into the OFF state. After
that, the routine is returned again to S510. On the other hand,
when it is determined in S520 that the engine 1 is not rotating or
when it is determined in S530 that the failure diagnosis completion
flag XCHK is in the ON state, the routine is immediately returned
to S510.
[0069] By such ignition system failure detecting process of FIG. 7,
in the hybrid vehicle in this embodiment, the failure diagnosis to
the ignition system 29 of the engine 1 is carried out as follows.
When the vehicle speed v is equal to or lower than 20 km/h, the
injection and ignition cut request XCUT from the M/G ECU 17 to the
engine ECU 19 enters the ON state. Consequently, just after the
start of execution of the ignition system failure detecting process
of FIG. 7 by the turn-on of the ignition switch 45, it is
positively determined in S510 that the injection and ignition cut
request XCUT is in the ON state (that is, the engine is in the
state where the fuel injection and ignition to the engine 1 are not
performed by the ignition controlling process of FIG. 6A and the
injection controlling process of FIG. 6B) (YES in S510).
[0070] When the accelerator pedal is pressed down by a driver to
start the vehicle by at least one of the outputs of the M/Gs 3 and
5 controlled as electric motors, and the engine 1 enters the
motoring state, it is positively determined in S520 that the engine
1 is rotating (YES in S520). The determination in S530 is negative
(NO) at this point because the flag XCHK is previously set to zero
(0) in S500. In S540, the operation inhibition flag XSTOP is set in
the ON state, thereby inhibiting the execution of the fuel
injection (S420) and the ignition (S320) to the engine 1 by the
ignition controlling process of FIG. 6A and the injection
controlling process of FIG. 6B even if the injection and ignition
cut request XCUT from the M/G ECU 17 to the engine ECU 19 is
changed into the OFF state.
[0071] Subsequently, by the processes of S550 and S560, the failure
diagnosis to the ignition system 29 is made. More specifically, the
ignition instruction signal IGt is outputted once each time to the
igniter 51 of the ignition system 29 of each cylinder (S550). When
the ignition normal state signal IGf is returned from the igniter
51 of each cylinder in response to the ignition instruction signal
IGt, it is determined that the ignition system 29 is normal (YES in
S560). When the ignition system 29 is determined as normal as
mentioned above, the operation inhibition flag XSTOP is set into
the OFF state (S570), thereby permitting the fuel injection and the
ignition to the engine 1 by the ignition controlling process of
FIG. 6A and the injection controlling process of FIG. 6B when the
injection and ignition cut request XCUT from the M/G ECU 17 to the
engine ECU 19 enters the OFF state.
[0072] If the ignition normal state signal IGf is not returned from
the igniter 51 of each cylinder in response to the ignition
instruction signal IGt generated in S550, it is determined that the
ignition system 29 has a failure (NO in S560). The failure is
displayed (S580) and the limp-home request is transmitted to the
M/G ECU 17 (S590). When a failure is detected as mentioned above,
the operation inhibition flag XSTOP remains in the ON state.
Consequently, even if the injection and ignition cut request XCUT
from the M/G ECU 17 to the engine ECU 19 enters the OFF state, the
fuel injection and the ignition to the engine 1 by the ignition
controlling process of FIG. 6A and the injection controlling
process of FIG. 6B are inhibited.
[0073] When the failure diagnosis to the ignition system 29 is
completed in the above manner, the failure diagnosis completion
flag XCHK is set into the ON state in S600. Consequently, even if
both S510 and S520 are positively determined, S530 is positively
determined (that is, it is determined that the failure diagnosis
has been completed), and the failure diagnosis to the ignition
system 29 is not performed.
[0074] On the other hand, when the vehicle speed v exceeds 20 km/h
after that and the injection and ignition cut request XCUT from the
M/G ECU 17 to the engine ECU 19 is changed from the ON state to the
OFF state, S510 becomes negative (NO in S510) and the failure
diagnosis completion flag XCHK is set into the OFF state in S610.
Consequently, when the injection and ignition cut request XCUT is
changed from the ON state to the OFF state, the processes of S510
and S610 are executed again. If the ignition system 29 is
determined as normal by the previous failure diagnosis (S560: YES),
the fuel injection and the ignition to the engine 1 are performed
by the ignition controlling process of FIG. 6A and the injection
controlling process of FIG. 6B.
[0075] After that, when the vehicle speed v becomes equal to or
lower than 20 km/h and the injection and ignition cut request XCUT
from the M/G ECU 17 to the engine ECU 19 is changed from the OFF
state to the ON state, S510 and S520 are positively determined
again, and S530 is negatively determined. Consequently, the failure
diagnosis for the ignition system 29 is performed by the processes
of S540 and subsequent steps. That is, in the ignition system
failure detecting process of FIG. 7, each time the engine 1 enters
the motoring state (more specifically, when the engine 1 enters in
the motoring state for the first time by the turn-on of the
ignition switch 45 and each time the engine operating state where
the fuel injection and the ignition are performed is changed to the
motoring state), the failure diagnosis for the ignition system 29
is carried out once.
[0076] As described above in detail, in the M/G ECU 17 and the
engine ECU 19, when the engine is in the state where the fuel
injection to the engine 1 is not performed (YES in S510), the
ignition instruction signal IGt is outputted to the ignition system
29 (S550) and whether the ignition system 29 operates normally or
not is checked in response to the ignition instruction signal IGt
(S560). When it is detected that the ignition system 29 has a
failure, the execution of the fuel injection to the engine 1 is
inhibited. By the ECUs 17 and 19 of the embodiment, therefore, the
condition of the ignition system 29 can be checked before the fuel
injection is started to activate the engine 1 in the hybrid
vehicle. As a result, fuel injection to the engine 1 can be
prevented when the ignition system 29 has a failure. Unburned
gasses from the engine 1 generated due to the failure in the
ignition system 29 (ignition system failure) can be therefore
certainly prevented from being released, and the effect on
suppressing the environment pollution, produced by the hybrid
vehicle, can be improved.
[0077] Especially, in case of the PSHV as in the embodiment, the
engine 1 is started in the "pushed start" manner by execution of
the fuel injection and the ignition in the motoring state using the
outputs of the M/Gs 3 and 5. If the ignition system 29 has a
failure upon starting, much more unburned gases are released and
the drivability also deteriorates. By the ECUs 17 and 19 of the
embodiment, the release of the unburned gases and the deterioration
in drivability due to the failure in the ignition system 29 can be
certainly prevented.
[0078] According to the embodiment, the ignition instruction signal
IGt for failure diagnosis is outputted to the ignition system 29
when the engine 1 is in the motoring state (YES in S510 and S520).
Consequently, in a manner similar to S320 in FIG. 6A for outputting
the ignition instruction signal IGt in the normal operating mode,
the ignition instruction signal IGt for failure diagnosis can be
outputted at timings synchronized with the crank rotational angle
.theta.C of the engine 1, so that the embodiment is advantageous.
That is, as a process for outputting the ignition instruction
signal IGt for failure diagnosis, a process similar to that of S320
in FIG. 6A can be used and it is unnecessary to execute a special
process. Both of the processes can be combined into a single
process.
[0079] Further, according to the embodiment, in the ignition system
failure detecting process of FIG. 7, when the operation inhibition
flag XSTOP is set in the ON state in S540 just before S550 where
the ignition instruction signal IGt for failure diagnosis is
outputted and it is determined in S560 that the ignition system 29
is normal (YES in S560), the operation inhibition flag XSTOP is
again set in the OFF state (S570). If not (NO in S560), the
operation inhibition flag XSTOP is left in the ON state. That is,
the execution of the fuel injection to the engine 1 by the
injection controlling process in FIG. 6B is inhibited just before
outputting the ignition instruction signal IGt for failure
diagnosis to the ignition system 29. When it is determined that the
ignition system 29 is normal, the execution of the fuel injection
by the injection controlling process is permitted.
[0080] Even if the injection and ignition cut request XCUT from the
M/G ECU 17 to the engine ECU 19 is changed from the ON state to the
OFF state in a period since the ignition instruction signal IGt for
failure diagnosis is outputted until the failure or normal state of
the ignition system 29 is determined, the fuel is not injected to
the engine 1. As a result, even a remote possibility that the fuel
is injected to the engine 1 in spite of occurrence of a failure in
the ignition system 29 can be eliminated.
[0081] Although the first embodiment of the present invention has
been described above, it will be obviously understood that the
invention may be modified in various ways. The following (1) to (4)
are examples of possible modifications. (1) In the foregoing
embodiment, in the engine un-operated state where the fuel
injection is not executed to the engine 1 and in the motoring state
where the engine 1 is rotating, the failure diagnosis is carried
out by transmitting the ignition instruction signal IGt to the
ignition system 29 (igniter 51). It is also possible to eliminate
S520 in FIG. 7 and to perform the failure diagnosis of the ignition
system 29 in the rotating state of the engine 1. In this case, a
process for outputting the ignition instruction signal IGt
asynchronously with the rotation of the engine 1 is provided.
[0082] (2) Although the invention is applied to the PSHV in which
the output of the engine 1 is used also for driving the wheels 11R
and 11L in the foregoing embodiment, the invention can be also
applied to the SHV, in which the M/G 5 is separated from the M/G 3
and the engine 1 and the engine 1 generates the power only to drive
the M/G 3. In case of such an SHV, in which the engine 1 does not
enter the motoring state, the process corresponding to that of S520
in FIG. 7 is omitted as in the system mentioned in (1) above, and
the ignition instruction signal IGt is sent to the ignition system
29 to perform the failure diagnosis to the ignition system 29 when
the engine is not operating.
[0083] (3) On the other hand, according to the foregoing
embodiment, the ignition instruction signal IGt is outputted once
each time to the ignition system 29 of each cylinder in S550 in
FIG. 7. It is also possible to output the ignition instruction
signals IGt a plurality of times to each cylinder. For example, the
following manner can be considered. When the ignition instruction
signal IGt is outputted twice for each cylinder and a failure is
detected only at the first time, the check is made again in the
next failure diagnosis. When the failure is detected twice, it is
regarded that a failure really occurs and the fail-safe process in
S580 and S590 in FIG. 7 is executed.
[0084] (4) Although the ignition system 29 in FIG. 2 is provided
for each cylinder in the engine 1 in the foregoing embodiment, the
invention can be also similarly applied to an ignition system
having only a single igniter 51 and ignition coil 49, in which the
high voltage for ignition is distributed from the ignition coil 49
to the spark plug 47 of each cylinder via a distributer.
[0085] (Second Embodiment)
[0086] A second embodiment of the invention will be described
hereinbelow with reference to FIGS. 8 and 9. The first embodiment
is to detect a failure in the ignition system. In the second
embodiment, a failure in a rotation sensor system is detected. When
a failure occurs in the rotation sensor system, that is, the
rotational angle sensor 31 and the cylinder identifying sensor 32,
the ignition controlling process and the injection controlling
process shown in FIGS. 6A and 6B cannot be executed at proper
timing. As a result, the fuel injection timing and the ignition
timing to the engine 1 are deviated, so that unburned gases are
released from the exhaust pipe of the engine 1 and the drivability
of the vehicle deteriorates.
[0087] With reference to FIG. 8, the control of the M/Gs 3 and 5 in
the present embodiment will be described first. The process up to
and including S195 is the same as that of the first embodiment
shown in FIG. 3. In the present embodiment, S196, S197, and S198
are added to the process. The M/G ECU 17 instructs the inverters 13
and 15 to control the rotation of the M/Gs 3 and 5 through the
process of S150 to S195. After that, whether the engine 1 is
rotating or not is checked on the basis of the rotational speeds of
the M/Gs 3 and 5 which are determined in S196 by the signals from
the rotor position sensors 33 and 35. If the engine 1 is rotating,
in S197, engine rotating state data XKAI for notifying whether the
engine 1 is rotating is set in the ON state (logical value 1)
indicating that the engine 1 is rotating, and the resultant data is
transmitted to the engine ECU 19. On the contrary, when it is
determined in S196 that the engine 1 is not rotating, the
processing routine advances to S198 where the engine rotating state
data XKAI is set in the OFF state (logical value 0) indicating that
the engine 1 is not rotating, and the resultant data is transmitted
to the engine ECU 19.
[0088] To be specific, since the output shafts 1a, 3a, and 5a of
the engine 1 and the M/Gs 3 and 5 are connected to each other via
the planetary gear unit 7, the M/G ECU 17 detects the rotational
speed of the engine 1 by the rotating states of the M/Gs 3 and 5.
The M/G ECU 17 therefore notifies the engine ECU 19 of the rotation
state of the engine 1 by means of the engine rotating state data
XKAI. After performing the process of S197 or S198, the routine
goes back to the above-mentioned process of S100.
[0089] Also in the second embodiment, the ignition controlling
process shown in FIG. 6A and the injection controlling process
shown in FIG. 6B are executed in a manner similar to the first
embodiment. The rotation sensor system failure detecting process is
carried out according to the flowchart of FIG. 9. Specifically,
when the ignition switch is turned on and the operation is started,
in S600, the engine ECU 19 initializes the operation inhibition
flag XSTOP into the ON state (logical value 1), which is referred
to in S310 of the ignition controlling process and in S410 of the
injection controlling process, thereby inhibiting the execution of
the fuel injection and the ignition to the engine 1. The engine ECU
19 also initializes the failure diagnosis completion flag XCHK for
indicating whether the failure diagnosis for the rotation sensor
system has been completed or not into the OFF state (logical value
0) indicative of incompletion.
[0090] In S610, whether the injection and ignition cut request XCUT
from the M/G ECU 17 is in the ON state or not is checked. If YES,
it is determined that the engine is in the un-operated state where
the fuel injection and the ignition to the engine 1 are not
performed by the injection controlling process and the ignition
controlling process of FIGS. 6A and 6B, and the routine advances to
S620.
[0091] In S620, whether the failure diagnosis completion flag XCHK
is in the ON state (logical value 1) or not is checked. If the
failure diagnosis completion flag XCHK is not in the ON state (if
it is in the OFF state), it is determined that the failure
diagnosis to the rotation sensor system has not been completed and
the routine advances to S630 where the operation inhibition flag
XSTOP is set in the ON state. After that, in S640, whether the
engine 1 is rotating or not is checked on the basis of the engine
rotating state data XKAI from the M/G ECU 17. That is, in S640,
when the engine rotating state data XKAI is in the ON state, it is
determined that the engine 1 is rotating. When the engine rotating
state data XKAI is in the OFF state, it is determined that the
engine 1 is not rotating. In the case where it is determined in
S640 that the engine 1 is not rotating, the same determining
process is repeated. When it is determined in S640 that the engine
1 is rotating, the routine advances to S650.
[0092] In S650, within a predetermined time (for instance, one
second) since the rotating state of the engine 1 is affirmed in
S640, whether a pulse signal is generated from each of the
rotational angle sensor 31 and the cylinder identifying sensor 32
or not is checked. If the pulse signals are outputted from the
sensors 31 and 32, it is determined that the sensors 31 and 32 are
normal, and the routine advances to S660 where the operation
inhibition flag XSTOP is set in the OFF state (logical value 0) to
permit the fuel injection and the ignition to the engine 1 by the
injection controlling process and the ignition controlling process
of FIGS. 6A and 6B. On the contrary, when it is detected in S650
that the pulse signal is not outputted from one or both of the
rotational angle sensor 31 and the cylinder identifying sensor 32,
it is determined that the rotation sensor system has failures, and
the routine immediately advances to S670 without setting the
operation inhibition flag XSTOP in the OFF state. In S670, a
failure displaying process such as turn-on of a malfunction warning
lamp arranged in the meter panel of the vehicle or display of a
message for notifying of a failure in the engine 1 on the display
in the vehicle is performed. In S680, a limp-home request is
transmitted to the M/G ECU 17. The limp-home request denotes a
request for shifting the operating mode of the M/G ECU 17 to the
limp-home mode in which the vehicle is driven only by the outputs
of the M/Gs 3 and 5. After sending the limp-home request to the M/G
ECU 17 in S680 or after setting the operation inhibition flag XSTOP
in the OFF state in S660, the routine advances to S690 where the
failure diagnosis completion flag XCHK is set in the ON state.
After that, the routine is returned to S610.
[0093] On the other hand, when it is determined in S610 that the
injection and ignition cut request XCUT from the M/G ECU 17 is not
in the ON state (NO in S610), the routine advances to S700 where
the failure diagnosis completion flag XCHK is set in the OFF state.
After that, the routine is returned to S610 again. When it is
determined in S620 that the failure diagnosis completion flag XCHK
is in the ON state, the routine is immediately returned to
S610.
[0094] By such a rotation sensor system failure detecting process
of FIG. 9, the failure diagnosis to the sensors 31 and 32 in the
engine 1 is carried out as follows. When the vehicle speed v is
equal to or lower than 20 km/h, the injection and ignition cut
request XCUT from the M/G ECU 17 to the engine ECU 19 enters the ON
state. Consequently, just after start of the execution of the
rotation sensor system failure detecting process of FIG. 9 by the
turn-on of the ignition switch, S610 determines that the injection
and ignition cut request XCUT is in the ON state (that is, the
engine un-operated state where the fuel injection and the ignition
to the engine 1 are not executed by the injection controlling
process of FIG. 6A and the ignition controlling process of FIG. 6B)
(YES in S610).
[0095] At the time when S610 is determined as YES for the first
time, the failure diagnosis completion flag XCHK is already set in
the OFF state by the initialization in S600, and accordingly S620
is determined as NO (namely, it is determined that the failure
diagnosis to the rotation sensor system has not been completed). In
S630, the operation inhibition flag XSTOP is set in the ON state.
Consequently, even if the injection and ignition cut request XCUT
from the M/G ECU 17 to the engine ECU 19 is changed to the OFF
state, the execution of the fuel injection (S420) and the ignition
(S320) to the engine 1 by the ignition controlling process of FIG.
6A and the injection controlling process of FIG. 6B is inhibited.
In the present embodiment, the operation inhibition flag XSTOP is
initialized to the ON state in S600. This is to prevent the fuel
injection and the ignition to the engine 1 from being performed
even if the injection and ignition cut request XCUT from the M/G
ECU 17 is changed to the OFF state by chance during a period from
the turn-on of the ignition switch to the execution of the process
of S630.
[0096] After that, the accelerator pedal is pressed down by the
driver, and the vehicle is started by one or both of outputs of the
M/Gs 3 and 5 driven as electric motors. When the engine 1 enters
the motoring state, it is determined in S640 that the engine 1 is
rotating (YES in S640). In S650, the failure diagnosis to the
rotation sensor system is carried out. That is, whether or not the
pulse signals are generated from the sensors 31 and 32 within a
predetermined time is determined. If the pulse signals are normally
outputted from the sensors 31 and 32, it is determined that the
rotation sensor system is normal (YES in S650). When the normal
state is determined as mentioned above, the operation inhibition
flag XSTOP is set in the OFF state (S660), thereby permitting the
fuel injection and the ignition to the engine 1 by the processes of
FIGS. 6A and 6B when the injection and ignition cut request XCUT
from the M/G ECU 17 to the engine ECU 19 is set in the OFF
state.
[0097] When no pulse signals are outputted from the sensors 31 and
32, it is determined that the rotation sensor system is faulty (NO
in S650), and the failure display (S670) and the transmission of
the limp-home request to the M/G ECU 17 (S680) are carried out.
When they are determined as faulty as mentioned above, the
operation inhibition flag XSTOP remains in the ON state. After
that, even if the injection and ignition cut request XCUT from the
M/G ECU 17 to the engine ECU 19 enters the OFF state, the fuel
injection and the ignition to the engine 1 by the processes of
FIGS. 6A and 6B are not performed.
[0098] When the failure diagnosis to the rotation sensor system is
completed in this manner, the failure diagnosis completion flag
XCHK is set in the ON state in S690. Consequently, even if S610 is
determined positively (YES) next time, S620 is determined
positively (that is, it is determined that the failure diagnosis
has been completed), and the failure diagnosis to the rotation
sensor system is not executed.
[0099] On the other hand, when the vehicle speed v exceeds 20 km/h
and the injection and ignition cut request XCUT from the M/G ECU 17
to the engine ECU 19 is changed from the ON state to the OFF state,
S610 is determined negatively (NO in S610) and the failure
diagnosis completion flag XCHK is set in the OFF state in S700.
Consequently, when the injection and ignition cut request XCUT is
changed from the ON state to the OFF state, the processes of S610
and S700 are repeated. If it is determined by the previous failure
diagnosis that the rotation sensor system is normal (YES in S650),
the fuel injection and the ignition to the engine 1 are performed
by the processes of FIGS. 6A and 6B.
[0100] After that, when the vehicle speed v becomes equal to or
lower than 20 km/h and the injection and ignition cut request XCUT
from the M/G ECU 17 to the engine ECU 19 is changed from the OFF
state to the ON state, S610 is determined positively (YES) again
and S620 is determined negatively (NO). Further, after the
operation inhibition flag XSTOP is set in the ON state in S630,
S640 is determined positively (YES), and the failure diagnosis to
the sensors 31 and 32 is carried out by the process of S650.
[0101] That is, in the rotation sensor system failure detecting
process of FIG. 9, each time the engine 1 enters the motoring state
(specifically, when the ignition switch is turned on and the engine
1 enters the motoring state for the first time, and each time the
engine 1 is changed from the operating state where the fuel
injection and the ignition are performed to the motoring state),
the failure diagnosis to the rotation sensor system is carried out
once.
[0102] As described above in detail, in the M/G ECU 17 and the
engine ECU 19 of the present embodiment, when it is determined that
the engine 1 is in the motoring state (YES in S610 and S640),
whether pulse signals are normally outputted from the sensors 31
and 32 or not is checked (S650). When it is determined that the
sensors 31 and 32 are faulty, the fuel injection and the ignition
to the engine 1 are not performed. That is, by paying attention to
the point that the engine 1 always enters the motoring state before
being started, whether pulse signals are normally outputted from
the rotation sensor system or not is checked in the motoring
state.
[0103] According to the ECUs 17 and 19 in this embodiment, the
conditions of the rotation sensor system can be checked before the
fuel injection and the ignition are started to activate the engine
1. As a result, the execution of the fuel injection and the
ignition to the engine 1 can be prevented if a failure in the
rotation sensor system is found.
[0104] It can be therefore certainly prevented that unburned gases
are released from the engine 1 in association with a failure of the
rotation sensor system, and the effects on suppression of the
environmental pollution of the hybrid vehicle can be enhanced.
Since the fuel injection and the ignition to the engine 1 at
improper timing due to a failure in the rotation sensor system are
prevented, the drivability of the vehicle is not adversely affected
by the failure. This is because the vehicle can be driven only by
the outputs of the M/Gs 3 and 5 in a state where the fuel injection
and the ignition to the engine 1 are not carried out.
[0105] Moreover, according to the second embodiment, whether the
fuel injection and the ignition to the engine 1 are performed or
not is checked in S610 of FIG. 9, and whether the engine 1 is
rotating or not is checked in S640. If YES in both of the steps, it
is determined that the engine 1 is in the motoring state. When S610
is determined positively (YES in S610), the operation inhibition
flag XSTOP is set in the ON state, thereby inhibiting the execution
of the fuel injection and the ignition to the engine 1 by the
processes of FIGS. 6A and 6B (S630). When it is determined in S650
that the rotation sensor system is normal (YES in S650), the
operation inhibition flag XSTOP is set into the OFF state again,
thereby permitting the execution of the fuel injection and the
ignition by the processes of FIGS. 6A and 6B (S660). If not (NO in
S650), the operation inhibition flag XSTOP is left in the ON
state.
[0106] Consequently, even if the injection and ignition cut request
XCUT from the M/G ECU 17 to the engine ECU 19 is changed from the
ON state to the OFF state in the middle of the determination of the
normal/abnormal state of the rotation sensor system in S650 in FIG.
9, the fuel injection and the ignition to the engine 1 are not
started. As a result, even a remote possibility that the fuel
injection and the ignition to the engine 1 are carried out in spite
of occurrence of a failure in the rotation sensor system can be
eliminated.
[0107] More specifically, the process of S630 in FIG. 9 for setting
the operation inhibition flag XSTOP into the ON state may be
executed not between S620 and S640 but after it is determined that
the rotation sensor system is faulty in S650 (for instance, just
before S670). In this case, however, when the injection and
ignition cut request XCUT from the M/G ECU 17 to the engine ECU 19
is changed from the ON state to the OFF state during determination
of the normal or failure state of the rotation sensor system in
S650, there is the possibility that the fuel injection and the
ignition to the engine 1 are started by the processes of FIGS. 6A
and 6B. In this case, if the rotation sensor system is faulty,
there is a fear that, although a small amount, unburned gases are
released. On the contrary, according to the second embodiment, when
the engine 1 is in the motoring state, the start of the fuel
injection and the ignition to the engine 1 is preliminarily
inhibited, and then the normal or abnormal state of the rotation
sensor system is checked in the motoring state. Consequently, the
release of unburned gases can be surely prevented.
[0108] In FIG. 9, the process of S630 may be executed between S640
and S650, not between S620 and S640. In such a case, the operation
inhibition flag XSTOP is set in the ON state at the time when the
motoring state is determined (YES in S640), thereby inhibiting the
start of the fuel injection and the ignition to the engine 1. The
release of unburned gases can be, therefore, certainly prevented.
However, there is an advantage if the operation inhibition flag
XSTOP is set in the ON state (S630) irrespective of the rotating
state of the engine 1 at the time when S610 is determined
positively (YES in S610) as in FIG. 9. That is, when the engine 1
is started for the first time upon start of the vehicle, the engine
1 starts to be rotated by the outputs of the M/Gs 3 and 5 in a
state where the fuel injection and the ignition to the engine 1 are
not executed from the beginning. At that time, the engine 1 enters
the motoring state. Upon such a start of the vehicle, the fuel
injection and the injection to the engine 1 can be preliminarily
inhibited before the engine 1 enters the motoring state. Therefore,
the execution of the fuel injection and the ignition to the engine
1 before completion of the check of the normal/abnormal state of
the rotation sensor system can be more certainly prevented.
Further, the execution of the fuel injection and the ignition to
the engine 1 under the failure in the rotation sensor system can be
more certainly prevented.
[0109] Although the second embodiment of the present invention has
been described above, it will be obviously understood that the
invention is not limited to the embodiment but can be modified in
various manners. For example, although whether the pulse signals
are outputted or not from the sensors 31 and 32 within a
predetermined time is checked in S650 in FIG. 9 in the second
embodiment, it is also possible to make the M/G ECU 17 transmit
data indicative of the present rotational speed of the engine 1 and
check whether or not the number of pulse signals corresponding to
the present rotational speed are outputted from the sensors 31 and
32 within a predetermined specific time. In such a manner, the
failure diagnosis to the rotation sensor system can be more
accurately carried out.
[0110] The failure diagnosis to the rotation sensor system is
carried out each time the engine 1 enters the motoring state in the
foregoing embodiment. In order to reduce the processing load of a
microcomputer mounted on the engine ECU 19, for example, the
failure diagnosis may be also performed only when the ignition
switch is turned on and the engine 1 enters the motoring state for
the first time. This modification can be done by simply eliminating
the process of S700 in FIG. 9 (process for returning the failure
diagnosis completion flag XCHK to the OFF state).
[0111] Further, it is also possible to check the normal/abnormal
state of the rotation sensor system during a usual operation of the
engine 1. In this case, for example, it is determined that the
rotation sensor system is faulty if pulse signals are not outputted
from the sensors 31 and 32 within a predetermined time during the
usual operation of the engine 1.
[0112] It is also possible to purposely set the engine 1 in the
motoring state and to perform the failure diagnosis to the rotation
sensor system. More specifically, when the motoring request is
received from the engine ECU 19, the M/G ECU 17 executes a process
for immediately rotating the engine 1 by the M/Gs 3 and 5. In the
case where the fuel injection and the ignition to the engine 1 are
not carried out, the engine ECU 19 sends the motoring request to
the M/G ECU 17 to check whether or not the pulse signals are
outputted from the sensors 31 and 32 within a predetermined period
of time. If no pulse signals are outputted, a failure state is
determined, and the fuel injection and the ignition to the engine 1
are not performed after that. In this case, the following manner is
more effective. In a manner similar to S630 to S680 in FIG. 9, the
engine ECU 19 sets the operation inhibition flag XSTOP in the ON
state and transmits the motoring request to the M/G ECU 17. If the
engine ECU 19 determines that sensors 31 and 32 are normal, the
operation inhibition flag XSTOP is returned to the OFF state.
[0113] Although the invention is applied to the parallel-series
hybrid vehicle in the second embodiment, the invention can be
similarly applied to other hybrid vehicles in which the engine 1 is
started in the motoring state.
[0114] While the present invention has been shown and described
with reference to the foregoing preferred embodiments, it will be
apparent to those skilled in the art that changes in form and
detail may be made therein without departing from the scope of the
invention as defined in the appended claims.
* * * * *