U.S. patent application number 14/534477 was filed with the patent office on 2015-06-04 for cooling device for internal combustion engine.
The applicant listed for this patent is Toyota Jidosha Kabushiki Kaisha. Invention is credited to Ikuo Ando, Kenji Kimura, Yoshihisa Oda, Toshitake Sasaki, Hitoki Sugimoto.
Application Number | 20150152775 14/534477 |
Document ID | / |
Family ID | 53264934 |
Filed Date | 2015-06-04 |
United States Patent
Application |
20150152775 |
Kind Code |
A1 |
Ando; Ikuo ; et al. |
June 4, 2015 |
COOLING DEVICE FOR INTERNAL COMBUSTION ENGINE
Abstract
An ECU performs a failure diagnosis for a thermostat valve after
starting of an engine based on an output of an engine-side coolant
water temperature sensor and an output of a radiator-side coolant
water temperature sensor. When an electric pump operates in
accordance with a heating request or the like of an
air-conditioning device during stopping of the engine, the
thermostat valve attains a closed state. When the electric pump
operates during stopping of the engine before the current starting
of the engine, starting of the failure diagnosis performed after
starting of the engine is delayed as compared to the case where the
electric pump does not operate during stopping of the engine.
Consequently, erroneous determination can be suppressed in the
failure diagnosis for the thermostat valve.
Inventors: |
Ando; Ikuo; (Toyota-shi
Aichi-ken, JP) ; Sugimoto; Hitoki; (Toyota-shi
Aichi-ken, JP) ; Sasaki; Toshitake; (Toyota-shi
Aichi-ken, JP) ; Oda; Yoshihisa; (Toyota-shi
Aichi-ken, JP) ; Kimura; Kenji; (Toyota-shi
Aichi-ken, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toyota Jidosha Kabushiki Kaisha |
Toyota-shi Aichi-ken |
|
JP |
|
|
Family ID: |
53264934 |
Appl. No.: |
14/534477 |
Filed: |
November 6, 2014 |
Current U.S.
Class: |
165/287 |
Current CPC
Class: |
F01P 2025/32 20130101;
F01P 2025/34 20130101; F01P 2060/08 20130101; F01P 2060/18
20130101; F01P 7/165 20130101 |
International
Class: |
F01P 7/16 20060101
F01P007/16; F01P 3/00 20060101 F01P003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2013 |
JP |
2013-250213 |
Claims
1. A cooling device for an internal combustion engine, comprising:
a coolant water passage formed in said internal combustion engine;
a radiator configured to cool coolant water; a radiator circulation
passage configured to allow coolant water discharged from said
coolant water passage to pass through said radiator and return to
said coolant water passage; a bypass passage configured to allow
coolant water discharged from said coolant water passage to return
to said coolant water passage without passing through said
radiator; a heat exchanger provided on said bypass passage and
utilizing heat of said coolant water; and a thermostat valve
connected to said radiator circulation passage and said bypass
passage, said thermostat valve being switched, in accordance with a
temperature of coolant water flowing in said thermostat valve, to
either a closed state of intercepting coolant water from said
radiator circulation passage and outputting coolant water from said
bypass passage to said coolant water passage, or an opened state of
outputting coolant water from said radiator circulation passage and
coolant water from said bypass passage to said coolant water
passage, said cooling device further comprising: an electric pump
configured to allow coolant water to circulate; a first temperature
sensor configured to detect a temperature of coolant water in said
coolant water passage; a second temperature sensor configured to
detect a temperature of coolant water in said radiator circulation
passage; and a control device configured to perform a failure
diagnosis for said thermostat valve after starting of said internal
combustion engine based on an output of said first temperature
sensor and an output of said second temperature sensor, wherein
when said electric pump operates in accordance with an operation
request of said heat exchanger during stopping of said internal
combustion engine, said thermostat valve attains the closed state,
and in a case where said electric pump operates during stopping of
said internal combustion engine, said control device delays
starting of said failure diagnosis performed after starting of said
internal combustion engine as compared to a case where said
electric pump does not operate during stopping of said internal
combustion engine.
2. The cooling device for an internal combustion engine according
to claim 1, wherein said control device starts said failure
diagnosis when a rise quantity of a coolant water temperature,
which is detected by said first temperature sensor, from starting
of said internal combustion engine exceeds a predetermined value,
and a first value indicating said predetermined value for the case
where said electric pump operates during stopping of said internal
combustion engine is larger than a second value indicating said
predetermined value for the case where said electric pump does not
operate during stopping of said internal combustion engine.
3. The cooling device for an internal combustion engine according
to claim 2, wherein said control device calculates an estimation
value of the coolant water temperature in said radiator circulation
passage based on a leakage flow rate through said radiator
circulation passage in the closed state of said thermostat valve
and on an output of said first temperature sensor, and diagnoses
that said thermostat valve is failed in a case where an output
value of said second temperature sensor is larger than the
calculated estimation value.
4. The cooling device for an internal combustion engine according
to claim 1, wherein said control device integrates an intake air
volume to said internal combustion engine from starting of said
internal combustion engine, and starts said failure diagnosis when
the integrated value of said intake air volume exceeds a
predetermined value, and a first value indicating said
predetermined value for the case where said electric pump operates
during stopping of said internal combustion engine is larger than a
second value indicating said predetermined value for the case where
said electric pump does not operate during stopping of said
internal combustion engine.
5. The cooling device for an internal combustion engine according
to claim 4, wherein said control device calculates an estimation
value of the coolant water temperature in said radiator circulation
passage based on a leakage flow rate through said radiator
circulation passage in the closed state of said thermostat valve
and on an output of said first temperature sensor, and diagnoses
that said thermostat valve is failed in a case where an output
value of said second temperature sensor is larger than the
calculated estimation value.
6. The cooling device for an internal combustion engine according
to claim 1, wherein said control device starts said failure
diagnosis when an elapsed time from starting of said internal
combustion engine exceeds a predetermined value, and a first value
indicating said predetermined value for the case where said
electric pump operates during stopping of said internal combustion
engine is larger than a second value indicating said predetermined
value for the case where said electric pump does not operate during
stopping of said internal combustion engine.
7. The cooling device for an internal combustion engine according
to claim 6, wherein said control device calculates an estimation
value of the coolant water temperature in said radiator circulation
passage based on a leakage flow rate through said radiator
circulation passage in the closed state of said thermostat valve
and on an output of said first temperature sensor, and diagnoses
that said thermostat valve is failed in a case where an output
value of said second temperature sensor is larger than the
calculated estimation value.
Description
[0001] This nonprovisional application is based on Japanese Patent
Application No. 2013-250213 filed on Dec. 3, 2013 with the Japan
Patent Office, the entire contents of which are hereby incorporated
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a cooling device for an
internal combustion engine, and particularly to a technique of
diagnosing a failure of a thermostat valve provided in a cooling
device for an internal combustion engine.
[0004] 2. Description of the Background Art
[0005] Japanese Patent Laying-Open No. 2010-196587 discloses an
abnormality detecting device for detecting an abnormality of a
thermostat valve provided in an engine cooling system of a hybrid
vehicle capable of performing EV traveling of stopping an engine
and traveling with a drive force of a motor. An increase in the EV
traveling reduces an opportunity to operate an engine and in turn
reduces an opportunity to detect an abnormality of a thermostat
valve. According to this abnormality detecting device, engine
coolant water is heated by a heater during the EV traveling, and if
a temperature of the engine coolant water rises to be higher than
or equal to a determination temperature, it is determined that a
thermostat valve operates normally (Japanese Patent Laying Open No.
2010-196587).
[0006] Heat of coolant water heated by exhausted heat of an engine
can be utilized for heating or the like performed by an
air-conditioning device, and even during stopping of the engine,
circulation of coolant water by operation of an electric pump in
accordance with a heating request or the like of the
air-conditioning device may occur. In this case, since the engine
is stopped, the thermostat valve is closed, and the coolant water
circulates without passing through a radiator. Accordingly, a
situation may occur which causes the temperature of the circulating
coolant water to be lower than a temperature of coolant water
remaining in a radiator circulation passage for allowing coolant
water to flow into the radiator.
[0007] When the engine is started in such a situation, and a
failure diagnosis for the thermostat valve is executed, erroneous
determination is possibly made in the failure diagnosis due to the
reversed relationship between the temperature of the circulating
coolant water and the temperature of the coolant water remaining in
the radiator circulation passage.
SUMMARY OF THE INVENTION
[0008] The present invention was made to solve the problem
described above, and its object is to suppress erroneous
determination in a failure diagnosis for a thermostat valve
provided in a cooling device for an internal combustion engine.
[0009] A cooling device for an internal combustion engine according
to the present invention includes a coolant water passage formed in
the internal combustion engine, a radiator cooling coolant water, a
radiator circulation passage, a bypass passage, a heat exchanger, a
thermostat valve, an electric pump, first and second temperature
sensors, and a control device. The radiator circulation passage is
configured to allow coolant water discharged from the coolant water
passage to pass through the radiator and return to the coolant
water passage. The bypass passage is configured to allow coolant
water discharged from the coolant water passage to return to the
coolant water passage without passing through the radiator. The
heat exchanger is provided on the bypass passage and utilizes heat
of the coolant water. The thermostat valve is connected to the
radiator circulation passage and the bypass passage, and switched,
in accordance with a temperature of coolant water flowing in the
thermostat valve, to either a closed state of intercepting coolant
water from the radiator circulation passage and outputting coolant
water from the bypass passage to the coolant water passage, or an
opened state of outputting coolant water from the radiator
circulation passage and coolant water from the bypass passage to
the coolant water passage. The electric pump allows coolant water
to circulate. The first temperature sensor detects a temperature of
coolant water in the coolant water passage. The second temperature
sensor detects a temperature of coolant water in the radiator
circulation passage. The control device performs a failure
diagnosis for the thermostat valve after starting of the internal
combustion engine based on an output of the first temperature
sensor and an output of the second temperature sensor. When the
electric pump operates in accordance with an operation request of
the heat exchanger during stopping of the internal combustion
engine, the thermostat valve attains the closed state. In a case
where the electric pump operates during stopping of the internal
combustion engine, the control device delays starting of the
failure diagnosis performed after starting of the internal
combustion engine as compared to a case where the electric pump
does not operate during stopping of the internal combustion
engine.
[0010] In this cooling device for an internal combustion engine, in
the case where the electric pump operates in accordance with the
operation request of the heat exchanger during stopping of the
internal combustion engine, starting of the failure diagnosis
performed after starting of the internal combustion engine is
delayed as compared to the case where the electric pump does not
operate during stopping of the internal combustion engine.
Therefore, starting of the failure diagnosis for the thermostat
valve is avoided in a state where the relationship between the
temperature of the coolant water in the coolant water passage and
the temperature of the coolant water in the radiator circulation
passage are inversed. Thus, according to the cooling device for an
internal combustion engine, erroneous determination in the failure
diagnosis for the thermostat valve can be suppressed.
[0011] Preferably, the control device starts the failure diagnosis
when a rise quantity (.DELTA.ECT) of a coolant water temperature,
which is detected by the first temperature sensor, from starting of
the internal combustion engine exceeds a predetermined value. A
first value indicating the predetermined value for the case where
the electric pump operates during stopping of the internal
combustion engine is larger than a second value indicating the
predetermined value for the case where the electric pump does not
operate during stopping of the internal combustion engine.
[0012] The failure diagnosis of the thermostat valve is performed
based on the coolant water temperature. According to the cooling
device for an internal combustion engine, starting of the failure
diagnosis is adjusted based on the coolant water temperature.
Therefore, a start timing of the failure diagnosis can be adjusted
with a high accuracy.
[0013] Moreover, preferably, the control device integrates an
intake air volume to the internal combustion engine from starting
of the internal combustion engine, and starts the failure diagnosis
when the integrated value of the intake air volume exceeds a
predetermined value. A first value indicating the predetermined
value for the case where the electric pump operates during stopping
of the internal combustion engine is larger than a second value
indicating the predetermined value for the case where the electric
pump does not operate during stopping of the internal combustion
engine.
[0014] The integrated amount of the intake air volume to the
internal combustion engine may represent a tendency of a rise in
the temperature of the internal combustion engine and of the
coolant water. Therefore, in this cooling device for an internal
combustion engine, starting of the failure diagnosis is adjusted
based on the integrated amount of the intake air volume. Thus, this
cooling device for an internal combustion engine can also suppress
erroneous determination in the failure diagnosis for the thermostat
valve.
[0015] Moreover, preferably, the control device starts the failure
diagnosis when an elapsed time from starting of the internal
combustion engine exceeds a predetermined value. A first value
indicating the predetermined value for the case where the electric
pump operates during stopping of the internal combustion engine is
larger than a second value indicating the predetermined value for
the case where the electric pump does not operate during stopping
of the internal combustion engine.
[0016] In this cooling device for an internal combustion engine,
starting of the failure diagnosis is adjusted based on the elapsed
time from starting of the internal combustion engine. Therefore, a
process for capturing a detection signal of a sensor and a
calculation process are not required. Thus, according to this
cooling device for an internal combustion engine, the process of
the control device can be simplified. Moreover, starting of the
failure diagnosis can be adjusted without being affected by an
abnormality of a sensor and a measurement accuracy
[0017] Preferably, the control device calculates an estimation
value of the coolant water temperature in the radiator circulation
passage based on a leakage flow rate through the radiator
circulation passage in the closed state of the thermostat valve and
on an output of the first temperature sensor, and diagnoses that
the thermostat valve is failed in a case where an output value of
the second temperature sensor is larger than the calculated
estimation value.
[0018] According to this cooling device for an internal combustion
engine, the failure diagnosis of the thermostat valve is performed
taking into consideration the leakage flow rate through the
radiator circulation passage in the closed state of the thermostat
valve. Therefore, the failure diagnosis can be performed with a
high accuracy.
[0019] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 represents a schematic configuration of a vehicle
including a cooling device for an internal combustion engine
according to an embodiment of the present invention.
[0021] FIG. 2 represents one example of a change in an engine
coolant water temperature before and after starting the engine.
[0022] FIG. 3 is a flowchart for describing procedures of the
thermostat valve failure diagnosis process executed by the ECU
shown in FIG. 1.
[0023] FIG. 4 is a flowchart representing process procedures for
determining the diagnosis precondition shown in FIG. 3.
[0024] FIG. 5 is a flowchart representing process procedures for
determining a diagnosis precondition in Modified Example 1.
[0025] FIG. 6 is a flowchart representing process procedures for
determining a diagnosis precondition in Modified Example 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] In the following, the embodiment of the present invention
will be described in detail with reference to the drawings. It
should be noted that the same or corresponding parts in the
drawings have the same reference numerals allotted and description
thereof will not be repeated.
[0027] FIG. 1 represents a schematic configuration of a vehicle
including a cooling device for an internal combustion engine
according to the embodiment of the present invention. Referring to
FIG. 1, a vehicle 100 includes an engine 20, an engine cooling
device 10 for cooling engine 20, and a thermal component 300.
[0028] Engine cooling device 10 includes an electric water pump
(hereinafter, referred to as "electric pump") 30, a radiator 40, a
radiator circulation passage 50, a bypass passage 60, and a
thermostat valve 70. Moreover, engine cooling device 10 further
includes an engine-side coolant water temperature sensor 80, a
radiator-side coolant water temperature sensor 90, and a control
device (hereinafter, also referred to as "ECU (Electronic Control
Unit)") 200.
[0029] Engine 20 has a water jacket 24 for cooling engine 20 by
means of coolant water. Water jacket 24 is formed around cylinders
of engine 20 and constitutes a coolant water passage 25 allowing
coolant water to pass therethrough. Coolant water passage 25 is
provided between an inlet 27 and an outlet 26, and allows coolant
water from inlet 27 to be sent out from outlet 26. The coolant
water flowing into coolant water passage 25 performs a heat
exchange with engine 20 to cool engine 20. Accordingly, engine 20
is maintained at a temperature which is suitable for
combustion.
[0030] Electric pump 30 is a pump driven by an electric motor to
circulate coolant water of engine 20. Electric pump 30 is mounted
to an attachment-side surface portion 22 of an engine main body.
Electric pump 30 allows coolant water to be sent out from inlet 27
into coolant water passage 25.
[0031] Driving and stopping of electric pump 30 is controlled by a
control signal received from ECU 200. Further, a discharge amount
of coolant water discharged from electric pump 30 is controlled by
a control signal received from ECU 200.
[0032] Outlet 26 constitutes a branch portion 120. Branch portion
120 is connected to radiator circulation passage 50 and bypass
passage 60. Branch portion 120 separates coolant water from coolant
water passage 25 into coolant water directed to radiator
circulation passage 50 and coolant water directed to bypass passage
60.
[0033] Radiator circulation passage 50 is a passage for circulating
coolant water between engine 20, electric pump 30, and radiator 40.
Radiator circulation passage 50 is constituted by pipes 50a, 50b
and radiator 40. Pipe 50a is provided between branch portion 120
and an inlet 42 of radiator 40. Pipe 50b is provided between an
outlet 44 of radiator 40 and thermostat valve 70. Coolant water
warmed up in engine 20 passes through radiator 40 and is
cooled.
[0034] Radiator 40 performs a heat exchange between coolant water
flowing in radiator 40 and outside air to thereby radiate heat of
the coolant water. Radiator 40 is provided with cooling fans 46.
Cooling fan 46 accelerates a heat exchange through ventilation to
improve a heat-radiation efficiency of the coolant water in
radiator 40. Coolant water cooled in radiator 40 is sent out from
outlet 44.
[0035] Bypass passage 60 is a passage for circulating coolant water
without passing through radiator 40. Bypass passage 60 is
constituted by pipes 60a, 60b and thermal component 300. Pipe 60a
is provided between branch portion 120 and thermal component 300.
Pipe 60b is provided between thermal component 300 and thermostat
valve 70.
[0036] Thermal component 300 includes an EGR (Exhaust Gas
Recirculation) cooler 28, a pipe 29, an exhaust heat recovery unit
32, a heater core 36, a throttle body 35, and an EGR valve 34.
[0037] EGR cooler 28 cools EGR gas by means of coolant water.
Throttle body 35 is warmed up by coolant water to prevent
occurrence of adhesion and the like. EGR valve 34 is cooled by the
coolant water. Exhaust heat recovery unit 32 warms up the coolant
water by heat of exhaust gas to thereby improve an engine mobility
during a low temperature.
[0038] Heater core 36 is used as a heater of an air-conditioning
device, and performs a heat exchange between coolant water and
blast air of the air-conditioning device to heat the blast air. It
should be note that the air-conditioning device may operate even
during stopping of engine 20. When a heating request is given by
the air-conditioning device during stopping of engine 20, electric
pump 30 operates to circulate coolant water through bypass passage
60, so that a heat exchange is performed by heater core 36 between
the coolant water and the blast air of the air-conditioning device.
This lowers the temperature of the coolant water flowing through
bypass passage 60.
[0039] Thermostat valve 70 is arranged at a merging portion 110
which merges coolant water having passed through radiator
circulation passage 50 and coolant water having passed through
bypass passage 60. Merging portion 110 is connected to radiator 40
through pipe 50b and connected also to pipe 60b. The coolant water
from merging portion 110 returns to a suction port of electric pump
30. Thermostat valve 70 is configured to be switched to either a
closed state or an opened state in accordance with a temperature of
coolant water flowing in thermostat valve 70 (in the vicinity of
the valve body).
[0040] In the case where a temperature of coolant water in the
vicinity of the valve body of thermostat valve 70 is less than a
predetermined valve-opening temperature (for example, 70.degree.
C.), thermostat valve 70 attains a closed state. In this case,
coolant water on the side of bypass passage 60 passes through
thermostat valve 70 and is outputted to water jacket 24, but
coolant water on the side of radiator circulation passage 50 is
intercepted by thermostat valve 70 and not outputted to water
jacket 24. Accordingly, coolant water having taken heat from engine
20 flows back to engine 20 (water jacket 24) without being cooled
by radiator 40, so that engine 20 is warmed up.
[0041] Meanwhile, in a case where a temperature of coolant water in
the vicinity of the valve body of thermostat valve 70 is equal to
or higher than the valve-opening temperature described above,
thermostat valve 70 is attains an opened state. In this case,
coolant water from radiator circulation passage 50 and coolant
water from bypass passage 60 pass through thermostat valve 70 and
are outputted to water jacket 24. Moreover, an opening degree of
thermostat valve 70 is adjusted in accordance with a temperature of
coolant water. Accordingly, a mixture ratio between the coolant
water from radiator circulation passage 50 and the coolant water
from bypass passage 60 is adjusted, so that the temperature of the
coolant water passing through water jacket 24 is maintained at an
appropriate temperature.
[0042] Engine-side coolant water temperature sensor 80 is provided
at branch portion 120. Engine-side coolant water temperature sensor
80 detects a temperature of coolant water sent out from outlet 26
(hereinafter, referred to as "engine outlet water temperature ECT"
or simply as "ECT") and outputs a detection result (ECT detection
value) to ECU 200. It should be noted that engine-side coolant
water temperature sensor 80 is all necessary to be provided on a
passage through which coolant water always circulates, and it may
be provided for example on coolant water passage 25.
[0043] Radiator-side coolant water temperature sensor 90 is
provided on pipe 50a. Radiator-side coolant water temperature
sensor 90 detects a temperature of coolant water flowing into pipe
50a of radiator circulation passage 50 (hereinafter, referred to as
"radiator inlet water temperature RCT" or simply as "RCT") and
outputs a detection result (RCT detection value) to ECU 200. It
should be noted that radiator-side coolant water temperature sensor
90 is all necessary to be provided on radiator circulation passage
50, and it may be provided for example on pipe 50b.
[0044] In vehicle 100 having such a configuration as described
above, when thermostat valve 70 is failed, abnormalities may occur
including a close failure in which the valve body does not open
even if a coolant water temperature in the vicinity of the valve
body rises beyond the valve-opening temperature, and an open
failure in which the valve body does not close even if a coolant
water temperature in the vicinity of the valve body is lowered to
be less than the valve-opening temperature. In the state where such
a failure occurs, coolant water at an appropriate water temperature
cannot be supplied to coolant water passage 25 of engine 20, so
that an operation efficiency of engine 20 is lowered. Therefore, it
is preferable to continuously perform a failure diagnosis on
whether or not thermostat valve 70 functions normally during
operation of engine 20 to thereby find a failure in an early
stage.
[0045] Accordingly, ECU 200 performs a failure diagnosis for
thermostat valve 70 based on an ECT detection value received from
engine-side coolant water temperature sensor 80 and an RCT
detection value received from radiator-side coolant water
temperature sensor 90. This ECU 200 is configured by a CPU (Central
Processing Unit), a storage device, an input/output buffer, and the
like (none of these are illustrated).
[0046] As one example, ECU 200 implements a failure diagnosis with
a high diagnosis accuracy as will be described in the following. In
other words, in a water temperature region where thermostat valve
70 essentially does not open (in a water temperature region lower
than the valve-opening temperature), thermostat valve 70 is in the
closed state. Therefore, theoretically, the coolant water flows
into bypass passage 60, and the coolant water does not flow into
radiator circulation passage 50. Therefore, a difference equal to
or greater than a predetermined value occurs between the ECT
detection value and the RCT detection value. Thus, in the water
temperature region where thermostat valve 70 essentially does not
open, when the difference between the ECT detection value and the
RCT detection value is less than the predetermined value, it is
determined that thermostat valve 70 is opened, in other words, an
open failure occurs in thermostat valve 70.
[0047] However, indeed, even when thermostat valve 70 is normally
closed, a rise in the water pressure in radiator circulation
passage 50 by driving of electric pump 30 causes the coolant water
in radiator circulation passage 50 to leak out from thermostat
valve 70 to coolant water passage 25. In this case, even though
thermostat valve 70 is in the closed state, coolant water of the
amount corresponding to the leakage flow rate of thermostat valve
70 flows from coolant water passage 25 into radiator circulation
passage 50 and is mixed with the coolant water present in radiator
circulation passage 50, so that radiator inlet water temperature
RCT comes close to engine outlet water temperature ECT. Since it
causes the temperature difference between the ECT detection value
and the RCT detection value to be small, it may lower an accuracy
of the failure diagnosis.
[0048] Therefore, ECU 200 performs a failure diagnosis for
thermostat valve 70 taking into consideration that the coolant
water leaks out from thermostat valve 70 even when thermostat valve
70 is in a normal state. Specifically, ECU 200 performs a process
of calculating an estimation value of radiator inlet water
temperature RCT based on the ECT detection value and the leakage
flow rate of thermostat valve 70, and diagnosing whether or not
thermostat valve 70 is failed based on a result of comparing the
calculated RCT estimation value and the RCT detection value
(hereinafter, referred to as "thermostat valve failure diagnosis
process"). This thermostat valve failure diagnosis process will be
described later in detail with reference to a flowchart.
[0049] Meanwhile, as described above, the heat of the coolant water
heated by the exhaust heat of engine 20 can be utilized for heating
and the like by the air-conditioning device. In this embodiment,
the heat is used for heating by the air-conditioning device with
use of heater core 36 provided on bypass passage 60. Here, the heat
of the heated coolant water can be used even during stopping of
engine 20, and the coolant water may be circulated by operating
electric pump 30 in accordance with a heating request or the like
during stopping of engine 20. In this case, since engine 20 is
stopped, thermostat valve 70 is closed, and the coolant water does
not flow into radiator circulation passage 50 but circulate through
coolant water passage 25 of engine 20 and bypass passage 60. In
that case, the coolant water circulating through coolant water
passage 25 and bypass passage 60 is deprived of heat by heater core
36, and on the other hand the coolant water remaining in radiator
circulation passage 50 radiates heat only in a natural manner.
Therefore, it is likely to cause a situation in which the
temperature of the coolant water circulating though coolant water
passage 25 and bypass passage 60 becomes lower than the temperature
of the coolant water in radiator circulation passage 50.
Accordingly, although engine outlet water temperature ECT is
generally higher than radiator inlet water temperature RCT, the
relationship between engine outlet water temperature ECT and
radiator inlet water temperature RCT is inversed, so that erroneous
determination may be made in the failure diagnosis.
[0050] FIG. 2 represents one example of a change in the engine
coolant water temperature before and after starting of engine 20.
Referring to FIG. 2, it is assumed that, before time t1, engine 20
is stopped, and use of a heater and the like during stopping of the
engine causes a situation of ECT detection value <RCT detection
value. It should be noted that the failure diagnosis for thermostat
valve 70 is not performed during stopping of engine 20.
[0051] It is assumed that engine 20 is started at time t1. In that
case, the engine coolant water is heated by the exhaust heat of
engine 20, and the ECT detection value indicating the temperature
of the coolant water at the engine outlet starts to rise. It should
be noted that, immediately after starting of engine 20, the
temperature of the coolant water is lower than the valve-opening
temperature of thermostat valve 70, and thermostat valve 70 is
closed, so that no rise in the RCT detection value can be seen.
Then, until time t2, the ECT detection value <RCT detection
value continues, and it attains the ECT detection value >RCT
detection value on or after time t2.
[0052] As can be seen, even when engine 20 is started at time t1,
the ECT detection value <RCT detection value continues until
time t2. Therefore, if the failure diagnosis is started before time
t2, erroneous determination is made since the relationship of ECT
detection value >RCT detection value which should be essentially
provided is inversed. Therefore, in this embodiment, taking into
consideration the erroneous determination region between times t1
and t2, in the case where electric pump operates in accordance with
a heating request or the like of the air-conditioning device during
stopping of engine 20 (thermostat valve 70 is in the closed state),
ECU 200 delays starting of the failure diagnosis process for
thermostat valve 70 performed after starting of engine 20 as
compared to the case where electric pump 30 does not operate during
stopping of engine 20. Accordingly, the failure diagnosis is
avoided in the state where the relationship between the ECT
detection value and the RCT detection value is inversed, so that
the erroneous determination in the failure diagnosis is
suppressed.
[0053] FIG. 3 is a flowchart for describing procedures of the
thermostat valve failure diagnosis process executed by ECU 200
shown in FIG. 1. The process shown in this flowchart is executed at
the time of starting engine 20, for example, at the time of
starting engine after idling stop. In the case where vehicle 100 is
a hybrid vehicle, the process is executed further at the time of
starting an engine when switched from EV traveling with use of a
drive force of a motor after stopping engine 20 to HV traveling
with operation of engine 20. This flowchart is achieved by
executing a program stored in ECU 200 at predetermined cycles, and
the process of some steps can be achieved by constructing a
dedicated hardware (electronic circuit).
[0054] Referring to FIG. 3, ECU 200 calculates an estimation value
of radiator inlet water temperature RCT (RCT estimation value)
based on the ECT detection value received from engine-side coolant
water temperature sensor 80, and a leakage flow rate into radiator
circulation passage 50 when thermostat valve 70 is in the closed
state (Step S10). Specifically, ECU 200 can calculate the RCT
estimation value with use of the following expression as one
example.
RCT estimation value=(ECT detection value.times.leakage flow
rate+RCT estimation value (previous value).times.(pipe
volume-leakage flow rate))/pipe volume (1)
[0055] In Expression (1), the RCT estimation value is calculated
based on the assumption that the coolant water with the ECT
detection value and the coolant water with the RCT estimation value
(previous value) are evenly mixed in accordance with a ratio of the
leakage flow rate with respect to the pipe volume.
[0056] Herein, the leakage flow rate may be a fixed value
determined in advance based on an experimental result or the like,
or it may be a variable value set to have a larger value as the
flow rate of electric pump 30 for example is larger. The pipe
volume is a volume of the pipe through which the coolant water
flows from engine-side coolant water temperature sensor 80 to
radiator-side coolant water temperature sensor 90. It should be
noted that the calculation accuracy can be improved by dividing the
pipe into any number of regions and applying the expression of (1)
described above to each divided region.
[0057] Next, ECU 200 executes the process of determining whether or
not a precondition for executing an open failure diagnosis process
for thermostat valve 70 (hereinafter, simply referred to as
"diagnosis precondition") is met (Step S20). The contents of this
process will be described in detail in FIG. 4 which will be
described later.
[0058] Then, ECU 200 determines whether or not the thermostat open
failure diagnosis process will be performed based on the process
result of Step S20 (Step S30). When it is determined that the
diagnosis precondition is not met (NO in Step S30), ECU 200
terminates the process without executing the thermostat open
failure diagnosis process (processes of Steps S40 to S60). In other
words, ECU 200 prohibits the thermostat open failure diagnosis
process in the case where the diagnosis precondition is not
met.
[0059] On the other hand, when it is determined in Step S30 that
the diagnosis precondition is met (YES in Step S30), ECU 200
executes the thermostat open failure diagnosis process (the
processes of Steps S40 to S60).
[0060] In other words, ECU 200 determines whether or not the RCT
detection value received from radiator-side coolant water
temperature sensor 90 is higher than the RCT estimation value
calculated in Step S10 (Step S40). Then, when the RCT detection
value is higher than the RCT estimation value (YES in Step S40),
ECU 200 determines that thermostat valve 70 is in the open failure
state (Step S50). This is because when thermostat valve 70 is in
the open failure state, the heated coolant water of the amount
larger than the expected leakage flow rate flows into radiator
circulation passage 50, and a situation in which the RCT detection
value is higher than the RCT estimated value occurs. On the other
hand, when the RCT detection value is equal to or lower than the
RCT estimation value (NO in Step S40), ECU 200 determines that
thermostat valve 70 is normal (Step S60).
[0061] FIG. 4 is a flowchart representing the process procedures
for the diagnosis precondition determination executed in Step S20
of FIG. 3. Referring to FIG. 4, ECU 200 determines whether or not
the monitoring precondition is met. The monitoring precondition is
a condition set as a precondition for monitoring a water
temperature rise quantity .DELTA.ECT indicating a rise in the
coolant water temperature from starting of the engine in Steps S130
and S160 which will be described later. As one example, ECU 200
determines that the monitoring precondition is met when all of the
following conditions (a) to (f) are met.
[0062] (a) After current starting of an engine, the thermostat
failure diagnosis is not completed.
[0063] (b) The ECT detection value is less than the valve-opening
temperature (for example, 70.degree. C.) of thermostat valve
70.
[0064] (c) The ECT detection value at the time of starting the
engine is included in the range of -10.degree. C. to +56.degree.
C.
[0065] (d) The engine is started.
[0066] (e) The time change quantity of the ECT detection value is
equal to or greater than a predetermined value (for example,
0.1.degree. C./second).
[0067] (f) Engine-side coolant water temperature sensor 80 and
radiator-side coolant water temperature sensor 90 are normal.
[0068] Condition (a) provides the premise that the thermostat
failure diagnosis is performed once between starting of engine 20
and stopping next. Condition (b) is a condition for assuring that
thermostat valve 70 is essentially (if it is normal) closed.
Conditions (c) and (d) are conditions for assuring that the ECT
detection value increases in a manner capable of performing the
thermostat failure diagnosis after starting the engine. Condition
(e) is a condition for assuring a rise in the engine water
temperature after starting the engine. Condition (f) is a condition
for assuring a reliability of the ECT detection value or the RCT
detection value. It should be noted that, as the monitoring
precondition, conditions (a) to (f) described above may be selected
as needed.
[0069] When it is determined in Step S110 that the monitoring
precondition is not met (NO in Step S110), ECU 200 shifts the
process to Step S180 and determines that the diagnosis precondition
is not met (Step S180).
[0070] When it is determined in Step S110 that the monitoring
precondition is met (YES in Step S110), ECU 200 determines whether
or not electric pump 30 operates during previous stopping of the
engine (from previous stopping of the engine to the current
starting of the engine) (Step S120).
[0071] In the case where electric pump 30 operates during stopping
of the engine (YES in Step S120), ECU 200 determines whether or not
the water temperature rise quantity .DELTA.ECT indicating a rise in
the quantity of the ECT detection value after starting of engine 20
is larger than a predetermined value A (>predetermined value B)
(Step S130). This predetermined value A is a determination value of
the diagnosis precondition for the case where electric pump 30
operates during stopping of the engine, and it is larger than a
determination value B (default value) of the diagnosis precondition
for the case where electric pump 30 does not operate during
stopping of the engine. As one example, predetermined value B is
1.degree. C., and predetermined value A is 3.degree. C.
Accordingly, starting of the failure diagnosis for the case where
electric pump 30 operates during stopping of the engine can be
delayed as compared to the case where electric pump 30 does not
operate during stopping of the engine.
[0072] Then, when it is determined in Step S130 that water
temperature rise quantity .DELTA.ECT is larger than predetermined
value A (YES in Step S130), ECU 200 determines that the diagnosis
precondition is met (Step S140). When it is determined in Step S130
that water temperature rise quantity .DELTA.ECT is less than or
equal to predetermined value A (NO in Step S130), it is determined
that the diagnosis precondition is not met (Step S150).
[0073] On the other hand, when it is determined in Step S120 that
electric pump 30 does not operate during previous stopping of the
engine (NO in Step S120), ECU 200 determines whether or not water
temperature rise quantity .DELTA.ECT is larger than predetermined
value B (Step S160). When it is determined in Step S160 that water
temperature rise quantity .DELTA.ECT is larger than predetermined
value B (YES in Step 160), ECU 200 determines that the diagnosis
precondition is met (Step S170). When it is determined in Step S160
that water temperature rise quantity .DELTA.ECT is less than or
equal to predetermined value B (NO in Step S160), ECU 200
determines that the diagnosis precondition is not met (Step
S180).
[0074] As described above, in this engine cooling device 10, in the
case where electric pump 30 operates in accordance with a heating
request or the like of the air-conditioning device during stopping
of engine 20, starting of the failure diagnosis performed after
starting of engine 20 is delayed as compared to the case where
electric pump 30 does not operate during stopping of engine 20, so
that starting of the failure diagnosis of thermostat valve 70 in
the state where the relationship between engine outlet water
temperature ECT and radiator inlet water temperature RCT is
inversed can be avoided. Thus, according to this engine cooling
device 10, erroneous determination can be suppressed in the failure
diagnosis of thermostat valve 70.
[0075] Moreover, while the failure diagnosis for thermostat valve
70 is performed based on the temperature of the coolant water,
according to this engine cooling device 10, starting of the failure
diagnosis is adjusted based on the coolant water temperature, so
that the start timing of the failure diagnosis can be adjusted with
a high accuracy.
[0076] Moreover, according to this engine cooling device 10, the
failure diagnosis of thermostat valve 70 is performed taking into
consideration the leakage flow rate through radiator circulation
passage 50 in the closed state of thermostat valve 70, so that the
failure diagnosis can be performed with a high accuracy.
Modified Example 1
[0077] In the embodiment described above, starting of the
thermostat valve failure diagnosis process after starting of the
engine (the diagnosis precondition is met) is delayed based on the
rise quantity (.DELTA.ECT) of the engine coolant water temperature
(ECT detection value) after starting of engine 20. In place of
water temperature rise quantity .DELTA.ECT, an integrated amount of
the intake air volume into engine 20 from starting of engine 20 may
be used. This is because the integrated intake air volume from
starting of engine 20 may represent a tendency of the rise in
temperatures of engine 20 and the coolant water.
[0078] The overall configuration of the vehicle in this Modified
Example 1 is the same as vehicle 100 shown in FIG. 1. Moreover, the
procedures of the overall process of the thermostat valve failure
diagnosis executed by ECU 200 of this Modified Example 1 is the
same as the process procedures shown in FIG. 3.
[0079] FIG. 5 is a flowchart representing process procedures of the
diagnosis precondition determination (the process executed in Step
S20 of FIG. 3) in this Modified Example 1. Referring to FIG. 5,
this flowchart includes, in the flowchart shown in FIG. 4, Steps
S132 and S136 in place of Steps S130 and S160.
[0080] In other words, when it is determined in Step S120 that
electric pump 30 operates during previous stopping (YES in Step
S120), ECU 200 determines whether or not an integrated intake air
volume indicating an integrated amount of the intake air volume
into engine 20 from starting of engine 20 is greater than a
predetermined value C (>predetermined value D) (Step S132). It
should be noted that predetermined value C is a determination value
of the diagnosis precondition for the case where electric pump 30
operates during stopping of the engine, and it is larger than
determination value D (default value) for the case where electric
pump 30 does not operate during stopping of the engine. As one
example, predetermined value C is 50 g, and predetermined value D
is 20 g. It should be noted that the intake air volume into engine
20 can be detected with use of an air flow meter. With
predetermined value C >predetermined value D, starting of the
failure diagnosis for the case where electric pump 30 operates
during stopping of the engine can be delayed as compared to the
case where electric pump 30 does not operate during stopping of the
engine.
[0081] Then, when it is determined in Step S132 that the integrated
intake air volume is larger than predetermined value C (YES in Step
S132), the process is shifted to Step S140, and it is determined
that the diagnosis precondition is met. When it is determined that
the integrated intake air volume is equal to or less than
predetermined value C in Step S132 (NO in Step S132), the process
is shifted to Step S150, and it is determined that the diagnosis
precondition is not met.
[0082] On the other hand, when it is determined in Step S120 that
electric pump 30 does not operate during previous stopping of the
engine (NO in Step S120), ECU 200 determines whether or not the
integrated intake air volume is larger than predetermined value D
(Step S162). Then, when it is determined that the integrated intake
air volume is larger than predetermined value D (YES in Step S162),
the process is shifted to Step S170, and it is determined that the
diagnosis precondition is met. When it is determined in Step S162
that the integrated intake air volume is less than or equal to
predetermined value D (NO in Step S162), the process is shifted to
Step S180, and it is determined that the diagnosis precondition is
not met.
[0083] Also by this Modified Example 1, in the case where electric
pump 30 operates in accordance with a heating request or the like
of the air-conditioning device during stopping of engine 20,
starting of the failure diagnosis performed after starting of
engine 20 can be delayed as compared to the case where electric
pump 30 does not operate during stopping of engine 20. Accordingly,
similarly to the embodiment described above, erroneous
determination can be suppressed in the failure diagnosis of
thermostat valve 70.
Modified Example 2
[0084] While starting of the thermostat valve failure diagnosis
from starting of engine 20 (the diagnosis precondition is met) is
delayed based on the integrated intake air volume from starting of
engine 20 in Modified Example 1 described above, time from starting
of engine 20 can be measured to use an elapsed time after starting
of the engine. Accordingly, the process of capturing a detection
signal of a sensor and the calculation process are not required, so
that the process of ECU 200 is simplified. Moreover, starting of
the failure diagnosis can be adjusted without being affected by an
abnormality of the sensor and a measurement accuracy.
[0085] The overall configuration of the vehicle in this Modified
Example 2 is the same as that of vehicle 100 shown in FIG. 1.
Moreover, the procedures of the overall process of the thermostat
valve failure diagnosis executed by ECU 200 in this Modified
Example 2 are the same as the process procedures shown in FIG.
3.
[0086] FIG. 6 is a flowchart representing the process procedures
for determining the diagnosis precondition (the process executed in
Step S20 of FIG. 3) in this Modified Example 2. Referring to FIG.
6, this flowchart includes, in the flowchart shown in FIG. 4, Steps
S134 and S164 in place of Steps S130 and S160.
[0087] In other words, when it is determined in Step S120 that
electric pump 30 operates during previous stopping of the engine
(YES in Step S120), ECU 200 determines whether or not an elapsed
time from starting of engine 20 exceeds a predetermined value T1
(>predetermined value T2) (Step S134). It should be noted that
predetermined value T1 is a determination value of the diagnosis
precondition for the case where electric pump 30 operates during
stopping of the engine, and it is larger than determination value
T2 (default value) of the diagnosis precondition for the case where
electric pump 30 does not operate during stopping of the engine. As
one example, predetermined value T1 is 5 seconds, and predetermined
value T2 is 2 seconds. It should be noted that the elapsed time
from starting of engine 20 can be measured by means of a timer or
the like not illustrated in the drawings. With predetermined value
T1>predetermined value T2, starting of the failure diagnosis for
the case where electric pump 30 operates during stopping of the
engine can be delayed as compared to the case where electric pump
30 does not operate during stopping of the engine.
[0088] Then, when it is determined in Step S134 that the elapsed
time exceeds predetermined value T1 (YES in Step S134), the process
is shifted to Step S140, and it is determined that the diagnosis
precondition is met. When it is determined in Step S134 that the
elapsed time is less than or equal to predetermined value T1 (NO in
Step S134), the process is shifted to Step S150, and it is
determined that the diagnosis precondition is not met.
[0089] On the other hand, when it is determined in Step S120 that
electric pump 30 does not operate during previous stopping of the
engine (NO in Step S120), ECU 200 determines whether or not the
elapsed time exceeds predetermined value T2 (Step S164). Then, when
it is determined that the elapsed time exceeds predetermined value
T2 (YES in Step S164), the process is shifted to Step S170, and it
is determined that the diagnosis precondition is met. When it is
determined in Step S164 that the elapsed time is less than or equal
to predetermined value T2 (NO in Step S164), the process is shifted
to Step S180, and it is determined that the diagnosis precondition
is not met.
[0090] Also by this Modified Example 2, in the case where electric
pump 30 operates in accordance with a heating request or the like
of the air-conditioning device during stopping of engine 20,
starting of the failure diagnosis performed after starting of
engine 20 can be delayed as compared to the case where electric
pump 30 does not operate during stopping of engine 20. Accordingly,
similarly to the embodiment described above, erroneous
determination can be suppressed in the failure diagnosis of
thermostat valve 70.
[0091] Moreover, in this Modified Example 2, starting of the
failure diagnosis is adjusted based on the elapsed time from
starting of engine 20. Therefore, the process of capturing a
detection signal of a sensor and the calculation process are not
required. Thus, according to this Modified Example 2, the process
of ECU 200 can be simplified. Moreover, starting of the failure
diagnosis can be adjusted without being affected by an abnormality
of the sensor and the measurement accuracy.
[0092] It should be noted that, while the failure diagnosis of
thermostat valve 70 is performed taking into consideration the
leakage flow rate through radiator circulation passage 50 in the
closed state of thermostat valve 70 in the embodiment described
above and Modified Examples 1 and 2 thereof, the method of the
failure diagnosis is not limited to such methods. For example, the
present invention is applicable for the case where the failure
diagnosis is performed based on the comparison between ECT
detection value and the RCT detection value in more simple
manner.
[0093] It should be noted that this invention is applicable also to
a hybrid vehicle provided with a traveling motor in addition to
engine 20 and a vehicle not provided with the traveling motor. In
the vehicle not provided with the traveling motor, this invention
is applicable to starting of the engine after idling stop or after
IG-on operation by a user. In the hybrid vehicle, this invention is
further applicable to starting of engine when switching from the EV
traveling to the HV traveling.
[0094] It should be noted that, in the description above, engine 20
corresponds to one example of the "internal combustion engine" of
this invention, and heater core 36 corresponds to one example of
the "heat exchanger" of this invention. Moreover, engine-side
coolant water temperature sensor 80 corresponds to one example of
the "first temperature sensor" of this invention, and radiator-side
coolant water temperature sensor 90 corresponds to one example of
the "second temperature sensor" of this invention.
[0095] Although the present invention has been described and
illustrated in detail, it should be understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation. The scope of the present invention is indicated by
the scope of claims, and includes meaning equivalent to that of the
scope of claims and all the modification within the scope.
* * * * *