U.S. patent application number 10/372817 was filed with the patent office on 2004-03-25 for control system for internal combustion engine with catalyst for purifying exhaust gas.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Iihoshi, Yoichi, Miyazaki, Taizo.
Application Number | 20040055283 10/372817 |
Document ID | / |
Family ID | 31973246 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055283 |
Kind Code |
A1 |
Iihoshi, Yoichi ; et
al. |
March 25, 2004 |
Control system for internal combustion engine with catalyst for
purifying exhaust gas
Abstract
There is provided a control system for an internal combustion
engine, which aim for early warm-up of catalyst and the engine in
order to control a cooling loss and a heat radiation for cooling in
such a way that the warm-up of the catalyst is carried out prior to
the warm-up of the engine. That is, if the temperature of the
catalyst is not greater than an activation temperature, there is
carried out at least one of (1) retardation control of the ignition
timing, (2) stopping control of a water pump for engine cooling
water, (3) lowering control of the flow rate of the cooling water,
but if the temperature of the catalyst is higher than the
activation temperature, there is carried out at least one of
control of the water pump in accordance with a temperature of the
cooling water and control of retardation of the ignition timing,
until the temperature of the cooling water reaches a warm-up
temperature which is a normal operation temperature of the
engine.
Inventors: |
Iihoshi, Yoichi;
(Tsuchiura-shi, JP) ; Miyazaki, Taizo;
(Hitachi-shi, JP) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
31973246 |
Appl. No.: |
10/372817 |
Filed: |
February 26, 2003 |
Current U.S.
Class: |
60/284 ; 60/298;
60/320 |
Current CPC
Class: |
Y02T 10/40 20130101;
F02P 5/1506 20130101; F02P 5/152 20130101; F01P 2025/46 20130101;
Y02T 10/26 20130101; F01P 2025/44 20130101; Y02T 10/46 20130101;
F01P 7/164 20130101; Y02T 10/12 20130101; F02B 1/12 20130101; F02D
41/0255 20130101 |
Class at
Publication: |
060/284 ;
060/298; 060/320 |
International
Class: |
F01N 003/00; F01N
003/02; F01N 005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2002 |
JP |
2002-277379 |
Claims
What is claimed is:
1. A control system for an internal combustion engine incorporating
catalyst for purifying exhaust gas from the engine, characterized
in that a heat transmitted from combustion gas to an engine block
(cooling loss) and a heat transmitted from the engine block to
cooling water (heat radiation for cooling), are controlled to
effect early warm-up of the catalyst during a cold start of the
engine.
2. A control system for an internal combustion engine as set forth
in claim 1, wherein the cooling loss and the heat radiation for
cooling are controlled in such a way that the warm-up of the
catalyst is carried out prior to the warm-up of the engine while
aiming for early warm of both catalyst and engine during a cold
start of the engine.
3. A control system for an internal combustion engine as set forth
in claim 1 or 2, wherein the control of the cooling loss is carried
out by controlling an ignition timing, and the control of the heat
radiation for cooling is carried out by controlling a flow rate of
engine cooling water by means of a water pump, and if a temperature
of the catalyst has not yet reach its activation temperature, the
ignition timing is retarded under control so as to decrease the
cooling loss while a flow rate of the engine cooling water is set
to be zero or smaller than a normal flow rate so as to decrease the
heat radiation for cooling.
4. A control system for an internal combustion engine as set forth
in any one of claim 1 to 3, wherein the cooling loss and the heat
radiation for cooling are controlled in accordance with at least
either a temperature of engine cooling water or a temperature of
the catalyst.
5. A control system for an internal combustion engine as set forth
in any one of claims 1 to 4, wherein the heat radiation for cooling
is controlled so as to be minimum until the temperature of the
catalyst comes up to the activation temperature.
6. A control system as set forth in any one of claims 1 to 5, the
cooling loss is controlled to be maximum until the internal
combustion engine is warmed up after the temperature of the
catalyst reaches the activation temperature.
7. A control system for an internal combustion engine comprising
cooling water for cooling the engine, a circulation passage for the
cooling water, a water pump for controlling a flow rate of the
cooling water, and catalyst for purifying exhaust gas from the
engine, characterized in that the water pump is controlled in
accordance with a temperature of the catalyst.
8. A control system for an internal combustion engine as set forth
in claim 7, wherein the water pump is stopped under control if the
temperature of the catalyst is not greater than an activation
temperature at which the catalyst can purify the exhaust gas, and
the water pump is controlled in accordance with a temperature of
the cooling water after the temperature of the catalyst reaches the
activation temperature.
9. A control system for an internal combustion engine incorporating
cooling water for cooling the engine, a circulation passage for the
cooling water, a water pump for controlling a flow rate of the
cooling water and catalyst for purifying exhaust gas from the
engine, characterized in that if a temperature of the catalyst is
not greater than an activation temperature, control is made in such
a way that at least either (1) an ignition timing is retarded from
the normal one, (2) the water pump is stopped, or (3) the flow rate
of the cooling water becomes less than the normal one, if the
temperature of the catalyst is higher than the activation
temperature, control is made in such a way that at least either (5)
the water pump is controlled in accordance with a temperature of
the cooling water, or (6) the ignition timing is advanced from the
normal one, until the temperature of the cooling water reaches a
warm-up temperature which is a normal operation temperature of the
engine.
10. A control system for an internal combustion engine as set forth
in claim 9, further comprising a knocking sensor for detecting
knocking of the internal combustion engine, wherein when knocking
is detected, the ignition timing is retarded under control, and the
water pump is controlled so as to increase the flow rate of the
cooling water.
11. A control system for an internal combustion engine
incorporating a turbocharger for supercharging intake air in the
engine, a cooling passage for cooling the turbocharger and catalyst
for purifying exhaust gas, characterized by a valve for controlling
a flow rate of cooling water flowing through the cooling passage,
wherein the valve is controlled so as to decrease the flow rate of
the cooling water flowing through the cooling passage if the
temperature of the catalyst is not greater than an activation
temperature.
12. A control system for an internal combustion engine
incorporating a transmission for transmitting a power from the
engine, an oil cooler for cooling oil which lubricates the
transmission, a cooling passage for cooling the oil cooler, and
catalyst for purifying exhaust gas, characterized by a shut-off
valve for blocking the cooling passage, wherein the shut-off valve
is controlled so as to stop the flow of the cooling water in the
cooling passage if a temperature of the catalyst is not greater
than an activation temperature.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a control system for an
internal combustion engine, which incorporates catalyst for
purifying exhaust gas, and in particular to a technology of fast
activation of catalyst for purification of exhaust gas from an
internal combustion engine, by controlling an engine cooling system
or the like.
RELATED ART
[0002] As disclosed in, for example, JP-A-2000-34584 or
JP-A-2000-45843, there have been well-known many technologies of
inhibiting radiation of heat from an engine to cooling water during
a cold start in order to shorten the time of warm-up of the
engine.
[0003] For example, the JP-A-2000-34584 discloses such a technology
that the supply of cooling water is controlled in accordance with a
temperature of a combustion chamber during operation of an engine
so as to promote warm-up of the engine while the temperature of the
wall surface of a combustion chamber, which correlates to a
quantity of emergence of unburned HC components during a cold start
is raised along an optimum temperature rising characteristic.
Specifically, the cooling water is held in a reservoir tank when
the wall temperature T of the combustion chamber during engine
operation is lower than a first reference wall temperature T1, but
the cooling water is displaced into a cooling water jacket of the
engine when it is higher than T1. After the above-mentioned
displacement of the cooling water is completed, the circulation of
the cooling water is started.
[0004] Further, the JP-A-2000-45843 discloses a technology of
retarding the ignition timing in an unwarmed-up condition so as to
abruptly increase the exhaust temperature, exceeding a temperature
of activation of catalyst for purification of exhaust gas so as to
aim at promoting warm-up of catalyst for purification of exhaust
gas in order to allow the catalyst to exhibit its purification
characteristic in a short period.
[0005] Neither such a control technology that the warm-up of an
engine and the warm-up of catalyst for purification of exhaust gas
are associated with each other so as to carry out rational control,
nor such a technology of short-time warm-up of an internal
combustion engine that the control of a cooling water system and
the control of combustion are combined with each other has not yet
been built up in success.
BRIEF SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide a control
system for an internal combustion engine, which can rationally
control the warm-up of the internal combustion engine and the
warm-up of catalyst in the order of priority during a cold
start.
[0007] To the end, according to the first aspect of the present
invention, there is provided a control system for an internal
combustion engine incorporating catalyst for purifying exhaust gas
therefrom, which controls, during a cold start, a heat (cooling
loss) transmitted from combustion gas to an engine block and a heat
(heat radiation for cooling) transmitted from the engine block to
engine cooling water, in order to aim for early warm-up of the
catalyst. Further, there is provided a system for controlling the
cooling loss and the heat radiation for cooling, so that the
warm-up of the catalyst is preferential to the warm-up of the
internal combustion engine while the engine and the catalyst are
warmed up in a short time.
[0008] The control of the cooling loss is made by controlling, for
example, the ignition timing while the control of the heat
radiation for cooling is made by controlling the flow rate of
cooling water through the intermediary of a water pump. That is, in
such a case that the temperature of the catalyst has not yet risen
up to its activation temperature, retardation control of the
ignition timing is made so as to decrease the cooling loss, and as
well, control is made such that the flow rate of cooling water is
decreased to zero or a value smaller than a normal value so as to
decrease the heat radiation for cooling.
[0009] The above-mentioned control is carried out being based at
least upon a temperature of engine cooling water or a temperature
of the catalyst. These temperatures are detected by a water
temperature sensor and a catalyst temperature sensor. Further, the
temperature of the catalyst can be estimated or computed from an
engine speed, a load, an ignition timing, an EGR quantity, an
intake air quantity and an intake air temperature, a distance from
the engine to the catalyst, the thermal capacity (a number of cells
or a volume) of the catalyst and the like.
[0010] Further, according to the first aspect of the invention,
there is proposed a control system for controlling the engine in
such a way that the heat radiation for cooling is minimized during
activation control of catalyst until the catalyst is activated
while the cooling loss is maximized during control of warm-up of
the engine until the engine is warmed up after the activation of
the catalyst.
[0011] With the above-mentioned control, the engine and the
catalyst can be warmed up in a short time, thereby it is possible
to restrain the environmental contamination caused by exhaust gas
and to enhance the fuel economy.
[0012] Further, according to the first aspect of the present
invention, the ignition timing is retarded from the normal timing
if the catalyst temperature is lower than its activation
temperature while the ignition timing is advanced from the normal
timing until the temperature of cooling water rises up to a
temperature at which the warm-up of the engine is completed, after
the catalyst temperature rises up to its activation
temperature.
[0013] With the configuration as stated above, not only the
activation of the catalyst but also the warm-up of the engine can
be promoted. Further, the provision of a knock sensor for detecting
knocking of the internal combustion engine is desirable so that the
ignition timing is retarded when the knock sensor detects a knock
during ignition timing control, and further, the flow rate of the
cooling water by the water pump is increased in order to promote
the warm-up of the internal combustion engine in a sure and safe
manner.
[0014] According to a second aspect of the present invention, there
is provided a control system for an internal combustion engine
having a turbocharger for supercharging intake air in the internal
combustion engine and a cooling passage for cooling the
turbocharger, incorporating a valve for controlling a flow rate of
cooling water flowing through the cooling passage, in order to
control the valve so as to reduce the flow rate of the cooling
water flowing through the cooling passage if the temperature of
catalyst is not greater than an activation temperature thereof,
thereby it is possible to promote the activation of the
catalyst.
[0015] Further, according to a third aspect of the present
invention, there is provided a control system for an internal
combustion engine including a transmission for transmitting a power
from the internal combustion engine, an oil cooler for cooling oil
lubricating the transmission and a cooling passage for cooling the
oil cooler, comprising a shut-off valve for shutting off the
cooling passage, wherein the shut-off valve is controlled so as to
stop the flow of the cooling water in the cooling passage if a
temperature of catalyst is not greater than its activation
temperature, thereby it is possible to promote the activation of
the catalyst.
[0016] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
[0017] The present invention will be hereinbelow detailed in the
form of preferred embodiments with reference to the accompanying
drawings in which:
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING
[0018] FIG. 1 is a block diagram of the present invention:
[0019] FIG. 2 is a conceptual diagram for explaining a cooling loss
and a heat radiation for cooling in the present invention;
[0020] FIG. 3 is a diagram showing a relationship between an EGR
quantity and a cooling loss;
[0021] FIG. 4 is a diagram showing a relationship between an
ignition timing during combustion by spark ignition, and cooling
loss;
[0022] FIG. 5 is a diagram showing a relationship between a fuel
injection timing and a cooling loss during combustion by
compression ignition;
[0023] FIG. 6 is a diagram showing a relationship between a flow
rate of cooling water in an engine, and a heat radiation for
cooling;
[0024] FIG. 7 is a diagram showing a relationship between a water
temperature of cooling water in an engine and a heat radiation for
cooling;
[0025] FIG. 8 is a control flow-chart for a temperature
controller;
[0026] FIG. 9 is a view illustrating an engine system in a first
embodiment of the present invention;
[0027] FIG. 10 is a diagram illustrating a control flow-chart in
the embodiment shown in FIG. 9;
[0028] FIG. 11 is a view illustrating an example of a time-chart in
an application of the present invention;
[0029] FIG. 12 is a diagram showing a relationship between a
desired value of the flow rate of cooling water, and a heat
radiation for cooling;
[0030] FIG. 13 is a diagram showing a relationship between a
desired value of the ignition timing, and a cooling loss;
[0031] FIG. 14 is a view illustrating an engine system in a second
embodiment of the present invention;
[0032] FIG. 15 is a control flow-chart in the embodiment shown in
FIG. 14;
[0033] FIG. 16 is a time-chart during execuation of the control
shown in FIG. 15;
[0034] FIG. 17 is a view illustrating an engine system in a third
embodiment of the present invention;
[0035] FIG. 18 is a control-flow chart in part in the embodiment
shown in FIG. 17; and
[0036] FIG. 19 is a time-chart during execution of the control
shown in FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0037] The present invention will be hereinbelow made of
embodiments of the present invention with reference to the
accompanying drawings.
[0038] Referring to FIG. 1 which is a block diagram illustrating a
control system for an intern combustion engine, in accordance with
an embodiment of the present invention, a temperature controller
101 carries out temperature control of the engine and catalyst
(which is aim at purifying exhaust gas from the engine) so as to
aim for early warm-up of both engine and catalyst during a cold
start of the engine.
[0039] Signals indicating a temperature of the catalyst, a
temperature of cooling water and knocking, which are detected by
sensors, are received by the temperature controller 101 which
therefore computes a desired heat radiation for cooling, and a
desired cooling loss in order to control an engine cooling system.
The cooling loss and the heat radiation for cooling will be
detailed after the configuration shown in FIG. 1 is briefly
explained.
[0040] The desired heat radiation for cooling is delivered to a
cooling system controller 102 while the desired cooling loss is
delivered to an engine controller 103 for controlling the
combustion of the engine.
[0041] Further, the cooling system controller 102 controls a water
pump in the engine cooling water passage, a flow passage control
valve, a radiator and the like in accordance with the desired heat
radiation for cooling so as to control the value of heat radiation
for cooling. Meanwhile, the engine controller 103 controls intake
and exhaust valves, a fuel injection valve an ignition unit, an EGR
valve and the like in accordance with the desired cooling loss so
as to control the cooling loss.
[0042] The temperature controller 101, the cooling system
controller 102 and the engine controller 103 may be constituted by,
for example, a control unit C.
[0043] The essential feature of the present invention is the
provision of the control of the cooling loss and the heat radiation
for cooling in accordance with at least either one of a temperature
of the catalyst and a temperature of cooling water, and an object
of the present invention is to materialize both early activation of
the catalyst and early warm-up of the internal combustion
engine.
[0044] Explanation will be hereinbelow made of the cooling loss and
the heat radiation for cooling in detail with reference to FIG. 2
which shows the transmission of heat which is generated from a
combustion chamber 1 in the engine and which is then transmitted to
cooling water 2.
[0045] The cooling loss in the present invention is a heat value
with which a heat generated from the combustion gas in the
combustion chamber (cylinder) 1 of the engine is transmitted to an
engine block 3. The cooling loss relates to an averaged temperature
Ta and a temperature to the engine block 2 during engine cycles
(intake cycle, compression cycle, expansion cycle and exhaust
cycle) carried by a piston 4, and in particular to those during a
period from the compression cycle to the exhaust cycle. Thus, it is
understood that the cooling loss significantly relates to the
combustion. As shown in FIG. 3 which shows, as an example, the
relationship between an EGR (exhaust gas recirculation) value and
the cooling loss, an increase in the EGR value causes the averaged
temperature Ta to lower since a possible maximum combustion
temperature is lowered. Thus, the cooling loss can be controlled by
adjusting the EGR value through the control of the EGR valve and
the intake and exhaust valves.
[0046] Further, the averaged temperature also relates to an
ignition timing, and accordingly, the cooling loss can be
controlled by the ignition timing during combustion by spark
ignition, as shown in FIG. 4, and it can be controlled by an
injection timing during combustion by compression ignition (Diesel
combustion or combustion by premix self-ignition), as shown in FIG.
5.
[0047] Meanwhile, the heat radiation for cooling, concerned in the
present invention, is a heat value transmitted from the engine
block 3 to the cooling water 2. The heat radiation for cooling
mainly relates to a flow rate and a temperature of the cooling
water 2.
[0048] Referring to FIG. 6 which shows an example of the
relationship between the flow rate of the cooling water and the
heat radiation for cooling, the relationship between the flow rate
and the heat radiation for cooling, as shown in FIG. 6, exhibits,
the higher the flow rate, the greater the heat radiation for
cooling. Further, referring to FIG. 7 which shows a relationship
between the temperature of the cooling water and the heat radiation
for cooling, if the temperature of the engine block is constant,
the lower the temperature of the cooling water, the greater the
heat radiation for cooling. Thus, the heat radiation for cooling
can be controlled by a discharge quantity of the water pump or by a
radiator for radiating a heat from the cooling water into the
atmospheric air.
[0049] Further, another feature of the present invention, is the
provision of the control for the heat radiation for cooling and the
cooling loss in accordance with a temperature of the catalyst and a
temperature of the cooling water.
[0050] FIG. 8 shows a flow-chart as to the temperature controller
101.
[0051] Referring to FIG. 8, at step 801, outputs from a catalyst
temperature sensor, a water temperature sensor and the like are
transmitted to the controller 101.
[0052] At step 802, the catalyst temperature is compared with a
catalyst activation temperature at which the catalyst can purify
exhaust gas, and if the catalyst temperature is not less than the
catalyst activation temperature, step 804 is carried out, but if it
is false, step 803 is carried out.
[0053] At step 803, a desired heat radiation for cooling is
minimized. It is noted here that the minimum desired heat radiation
for cooling corresponds to a minimum value in a controllable range.
Due to this minimum control of the heat radiation for cooling, the
heat value transmitted to the cooling water is decreased while the
temperature of exhaust gas is increased so as to enable early
warm-up of the catalyst, that is, it is possible to fast raise the
temperature of the catalyst up to the activation temperature in
comparison with the conventional one. A specific example of the
minimum control of the heat radiation for cooling will be described
later.
[0054] At step 804, whether the temperature of engine cooling water
comes up to a warm-up temperature at which the engine can be
efficiently operated as usual or not is determined, and if it is
true, step 806 is carried out, but if it is false, step 805 is
carried out.
[0055] At step 805, the desired cooling loss is set to be maximum.
As a result, the heat value transmitted to the engine block is
increased, and further, since the heat radiation for cooling is
minimized, the engine can be warmed up fast in comparison with a
conventional one. The maximum control of the heat radiation for
cooling will be described later. It is noted here that the maximum
of the cooling loss corresponds to a maximum value in a
controllable range.
[0056] At step 806, whether the water temperature is not lower than
an overheat temperature at which there would be a risk of
occurrence of seizure of the engine, or not is determined, and if
it is true, step 805 is carried out, but if it is false, step 807
is carried out. At step 807, optimum fuel consumption control is
carried out and the desired cooling loss is minimized.
[0057] It is noted that the desired cooling loss is in a
controllable range, and it indicates a position of optimum spark
advance (optimum spark ignition timing) as shown in FIG. 4 if the
cooling loss is controlled only by the spark ignition timing. This
optimum spark ignition timing enables the engine to operate with a
high degree of efficiency.
[0058] At step 808 at which control is made for an abnormal
operation, that is, the desired heat radiation for cooling is
maximized so as to carry out cooling of the engine block by the
cooling water at a maximum degree in order to prevent occurrence of
seizure of the engine.
[0059] Referring to FIGS. 9 to 12, a specific control example in
this embodiment will be explained.
[0060] FIG. 9 is a view which shows a configuration of the engine
in this embodiment.
[0061] In this example, a cooling system for an engine 5 is
composed of a cooling water circulation passage 6, a water pump 7
for controlling heat radiation for cooling in the cooling system, a
water temperature sensor 8 for measuring a temperature of cooling
water, a radiator 9 for radiating heat from the cooling water into
the atmospheric air, a radiator fan (which is not shown) for
controlling the radiation of heat from the radiator into the
atmospheric air, and a flow passage change-over valve (thermostat)
10 for introducing cooling water.
[0062] Further, catalyst 12 (3 way catalyst) for purifying exhaust
gas and a catalyst sensor 13 for detecting a temperature of the
catalyst are incorporated in an exhaust pipe 11 of the engine.
Further, there is provided a knocking sensor 14 for detecting
knocking of the engine.
[0063] Referring to a flow-chart shown in FIG. 10, explanation will
be hereinbelow made of control for early warm-up of both catalyst
12 and engine 5.
[0064] At step 1001, outputs from the catalyst temperature sensor
13, the water temperature sensor 8 and the knocking sensor 14 are
read.
[0065] At step 1002, whether a value detected by the catalyst
temperature sensor 13 is not less than the activation temperature
of the catalyst or not is determined, and if it is true, step 1004
is carried out, if it is false, step 1003 is carried out.
[0066] At step 1003, the water pump 7 is stopped while the ignition
timing is retarded in order to fast warm up the catalyst 12. As the
water pump 7 is stopped, the heat radiation for cooling to cooling
water becomes minimum so as to aim at raising the temperature of
the engine 5, and further, the temperature of exhaust gas from the
engine is raised through the control of retardation of the ignition
timing. As a result, it is possible to aim for early warm-up of the
catalyst. It is noted that the retardation of the ignition timing
may decrease the cooling loss, as shown in FIG. 4, but may not
minimize the cooling loss. Although the cooling loss is minimized
at a position where the ignition timing is optimum, but in-this
case, since efficient combustion is carried out, the temperature of
exhaust gas may not be raised as is made through the control of
retardation.
[0067] At step 1004, whether a value of engine cooling water
detected by the water sensor 8 reaches the warm-up temperature of
the engine 5 or not is determined, and if it is true, step 1006 is
carried out, but if it is false step 1005 is carried out.
[0068] At step 1005, in order to warm up the engine 5, the ignition
timing is advanced so as to raise the temperature of the engine
cylinder. At this time, through the control of the cooling system,
the stop and the operation of the water pump 7 are repeated or the
discharge rate of the pump 7 is controlled to be minimum although
it is operated.
[0069] Through the circulation of cooling water at a small rate as
mentioned above, it is possible to prevent occurrence of thermal
stress in the engine block and knocking due to a hot spot in the
engine cylinder.
[0070] At step 1006, it is determined that whether a value detected
by the water temperature sensor or an estimated value of the
temperature of the engine is not less than an overheat temperature
at which the seizure of the engine is expected, or not. If it is
true, step 1008 is carried out, but if it is false, step 1007 is
carried out. At step 1007, control for minimizing the fuel
consumption is carried out. Thus, the ignition is controlled at an
ignition timing with which the cooling loss is minimized, and the
pump is controlled so that the temperature of cooling water becomes
not less than the warm-up temperature but not greater than the
overheat temperature at which the seizure of the engine occurs.
[0071] It is noted that a temperature of the engine is estimated
from the cooling loss and the heat radiation for cooling, and if
the history of temperature of the engine exhibits an increase while
the engine load is high, foreseeing control through which the flow
rate of cooling water increases in advance may be carried out. In
this foreseeing control, if the history of temperature of the
engine exhibits a decrease while the engine load is low, the flow
rate of cooling water is decreased in advance, or the circulation
of cooling water into the radiator may be stopped.
[0072] At step 1008, control upon overheating is carried out, that
is, the flow rate of cooling water from the pump 7 and the output
of the radiator are maximized so as to increase the heat radiation
for cooling in order to prevent occurrence of seizure of the
engine. Further, if the temperature is not lowered within a
predetermined time after the above-mentioned controlled is carried
out, the ignition timing is retarded so as to also decrease the
cooling loss. Further, since the overheating is caused by any
abnormality in the cooling system including the radiator and the
pump, a warning lamp is turned on for indication of requirement for
a fault diagnosis.
[0073] As to the fault diagnosis, if, for example, a water
temperature is higher than an overheat temperature while the engine
is operated at an idle speed, the radiator fan is operated being
alternately changed over between a highest speed and a lowest speed
(including a stop), every predetermined time. At this time, a fault
diagnosis for the radiator can be made in accordance with a speed
of the radiator fan and a variation in the output of the water
temperature sensor. Specifically, a correlation between the speed
of the radiator fan and a variation in the output of the water
temperature sensor is calculated, and if the thus calculated
correlation is small, it can be determined that the radiator or the
thermostat fails.
[0074] Similarly, by changing over the output of the pump every
predetermined time between a high output power and a low output
power, it is possible to carry out a fault diagnosis of the pump in
accordance with a correlation between a variation in temperature of
cooling water and a control input to the pump. Specifically, a
correlation between a control input of the pump and a variation in
the output of the water temperature sensor is calculated, and if
this correlation is small, it can be determined that the pump
fails.
[0075] Referring to FIG. 11 which shows an example of a time-chart
in the case of execution of the warm-up control for both catalyst
and engine, according to the present invention, during warm-up of
the catalyst until the temperature of the catalyst comes up to its
activation temperature, the ignition timing is retarded, and the
pump is stopped so as to set the flow rate to zero. During warm-up
of the engine after activation of the catalyst, the ignition timing
is advanced, and if knocking is detected, the ignition timing is
retarded while the flow rate of the pump is increased in order to
prevent occurrence of abnormal combustion.
[0076] After completion of the warm-up of the engine, the pump is
operated in a steady-state, and also the ignition timing is reset
to a normal position.
[0077] Referring to FIG. 12 which shows control objectives of the
flow rate in the control according to the present invention,
cooling water is blocked until the warm-up of the catalyst is
completed so as to minimize the heat-radiation for cooling, and
after completion of the warm-up of the catalyst, the flow rate of
cooling water is controlled so as to be low as possible as it can
until the warm-up of the engine is completed. After the completion
of the warm-up of the engine, the flow rate is controlled in
accordance with a value of the heat radiation for cooling, thereby
it is possible to optimumly materialize early warm-up of the
catalyst and the engine.
[0078] Further, referring to FIG. 13 which shows control objectives
of the ignition timing in the control according to the present
invention, optimum early warm-up can be materialized by retarding
the ignition timing at one and the same engine speed during warm-up
of the catalyst but by advancing the ignition timing up to a
knocking critical value during warm-up of the engine after
completion of the warm-up of the catalyst, with respect to a normal
ignition timing after completion of the warm-up. That is, if the
ignition timing is retarded, after-burning is caused in exhaust gas
discharged from the cylinder of the engine, and accordingly, the
temperature of the exhaust gas becomes higher, thereby it is
possible to aim for early warm-up. At this time, although the
cooling loss is small, it is, more or less, greater than that with
the normal ignition timing (efficiency drive) after completion of
the warm-up.
[0079] Referring to FIGS. 14 to 16, explanation will be hereinbelow
made of a second embodiment of the present invention.
[0080] Referring to FIG. 14 which shows the configuration of an
engine in the second embodiment, this configuration is the same as
that shown in FIG. 9, except that there are provided a turbocharger
15 for supercharging the intake air in an exhaust pipe 11, a
cooling passage 6a for cooling the turbocharger 15, a bypass
passage 6b bypassing the cooling passage 6a, and a bypass valve 16
for blocking the flow in the bypass flow passage 6a.
[0081] The cooling passage 6a and the bypass passage 6b are
alternately connected to the engine cooling passage 6 through
switching control of the bypass valve 16.
[0082] Referring to FIG. 15 which is a control flow-chart of the
bypass valve 16 in this embodiment, at step 1501, a value from the
catalyst temperature sensor 13 is read, and at step 1502, whether
the temperature of the catalyst is greater than an activation
temperature thereof or not is determined. If it is true, step 1504,
the bypass valve 16 is closed (default). Meanwhile, it is false, at
step 1503, the bypass valve 16 is opened so as to bypass cooling
water flowing through the turbocharger 15 during warm-up of the
catalyst.
[0083] Referring to FIG. 16 which shows a time-chart in the case of
execution of the control according to the present invention, during
warm-up of the catalyst, by opening the bypass valve 16, the
lowering of the temperature of exhaust gas, which is caused when
the exhaust gas passes through the turbocharger, can be minimized,
thereby it is possible to fast warm-up the catalyst. It is noted
that even during warm-up of the engine, if a relief valve for
bypassing the flow of exhaust gas flowing into a turbo-turbine is
closed, no cooling is required for the turbocharger, and
accordingly, the bypass valve 16 may be opened.
[0084] Referring to FIG. 17 which shows a third embodiment of the
present invention, the configuration of this embodiment is the same
as that shown in FIG. 9, except that there are provided an oil
cooler 18 for cooling a transmission 17, a cooling passage 6c for
cooling the oil cooler 18 and a shut-of valve 19 for blocking the
cooling passage 6c.
[0085] Referring to FIG. 18 which shows an control flow-chart of
the shut-off valve 19 in this embodiment, at step 1801, a value
from the catalyst temperature sensor 13 is read, and at step 1802,
whether the catalyst temperature is not less than its activation
temperature or not is determined. If it is true, at step 1804, the
shut-off valve 19 is opened, but if it is false, at step 1803, the
shut-off valve 19 is closed.
[0086] Referring to FIG. 19 which shows a time-chart in the case of
execution of the control according to the present invention, during
warm-up of the catalyst, the shut-off valve 19 is closed so as to
shut-off the flow of cooling water flowing through the oil cooler
18 in order to decrease the heat radiation for cooling, and as a
result, the exhaust temperature rises up, thereby it is possible to
fast warm up the catalyst.
[0087] According to the present invention, by controlling the
cooling system in accordance with a catalyst temperature, the
catalyst can be fast activated. Further, in combination of the
control of the cooling system for the engine or the like with the
control of the engine, the warm-up of the catalyst can be made
prior to the warm-up of the engine while aiming at warming up both
the catalyst and the engine. Thus, with the application of the
present invention, it is possible to reduce emission of exhaust gas
due to early activation of the catalyst, and to improve the fuel
consumption due to early warm-up of the internal combustion
engine.
[0088] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
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