U.S. patent application number 14/114355 was filed with the patent office on 2014-05-15 for cooling water temperature control apparatus for an internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Takashi Koyama, Koichiro Nakatani, Akira Yamashita. Invention is credited to Takashi Koyama, Koichiro Nakatani, Akira Yamashita.
Application Number | 20140130753 14/114355 |
Document ID | / |
Family ID | 47071742 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140130753 |
Kind Code |
A1 |
Koyama; Takashi ; et
al. |
May 15, 2014 |
COOLING WATER TEMPERATURE CONTROL APPARATUS FOR AN INTERNAL
COMBUSTION ENGINE
Abstract
The present invention is intended to provide a technique which
makes effective use of a phase transition temperature zone of
cooling water by controlling a control valve for changing the
temperature of the cooling water in an appropriate manner. The
present invention resides in a cooling water temperature control
apparatus for an internal combustion engine in which cooling water
is caused to circulate, said cooling water having variable specific
heat, said apparatus comprising: a received heat amount calculation
unit configured to calculate an amount of received heat which is
received by said cooling water, a control valve that is controlled
to open and close according to a command so as to change a
circulation route or an amount of circulation of said cooling water
and to change the temperature of said cooling water, and a control
unit configured to control said control valve based on the amount
of received heat which is calculated by said received heat amount
calculation unit.
Inventors: |
Koyama; Takashi;
(Mishima-shi, JP) ; Nakatani; Koichiro;
(Mishima-shi, JP) ; Yamashita; Akira; (Sunto-gun,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Koyama; Takashi
Nakatani; Koichiro
Yamashita; Akira |
Mishima-shi
Mishima-shi
Sunto-gun |
|
JP
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
47071742 |
Appl. No.: |
14/114355 |
Filed: |
April 28, 2011 |
PCT Filed: |
April 28, 2011 |
PCT NO: |
PCT/JP2011/060443 |
371 Date: |
January 30, 2014 |
Current U.S.
Class: |
123/41.05 |
Current CPC
Class: |
F01P 7/167 20130101;
F01P 2003/001 20130101; F01P 3/00 20130101; F01P 2037/00 20130101;
F01P 7/16 20130101 |
Class at
Publication: |
123/41.05 |
International
Class: |
F01P 7/16 20060101
F01P007/16 |
Claims
1.-4. (canceled)
5. A cooling water temperature control apparatus for an internal
combustion engine in which cooling water is caused to circulate,
said cooling water having variable specific heat, said apparatus
comprising: a received heat amount calculation unit configured to
calculate an inlet received heat amount which is received by said
cooling water at an inlet port from which said cooling water flows
into the internal combustion engine; a control valve that is
controlled to open and close according to a command so as to change
a circulation route or an amount of circulation of said cooling
water and to change the temperature of said cooling water; and a
control unit configured to control said control valve in such a
manner that said inlet received heat amount calculated by said
received heat amount calculation unit comes near to a lower side
starting value of received heat amount of a phase transition
temperature zone in which said cooling water is in a state in which
the specific heat thereof changes due to a phase transition of
particles.
6. The cooling water temperature control apparatus for an internal
combustion engine as set forth in claim 5, wherein said received
heat amount calculation unit calculates an outlet received heat
amount which is received by said cooling water at an outlet port
from which said cooling water flows out of the internal combustion
engine; and in cases where said outlet received heat amount
calculated by said received heat amount calculation unit becomes a
high amount of received heat in excess of an amount of received
heat of said phase transition temperature zone, said control unit
controls said control valve so that said outlet received heat
amount is included in the range of the amount of received heat of
said phase transition temperature zone.
7. The cooling water temperature control apparatus for an internal
combustion engine as set forth in claim 5, wherein in cases where
said received heat amount calculation unit can not calculate the
amount of received heat, said control valve is controlled in such a
manner as to lower the temperature of said cooling water.
8. The cooling water temperature control apparatus for an internal
combustion engine as set forth in claim 6, wherein in cases where
said received heat amount calculation unit can not calculate the
amount of received heat, said control valve is controlled in such a
manner as to lower the temperature of said cooling water.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cooling water temperature
control apparatus for an internal combustion engine.
BACKGROUND ART
[0002] There has been known a technique which controls the
temperature of cooling water in an internal combustion engine by
using a valve opening adjustment unit which is able to adjust
electronically the degree of opening of a valve in an electronic
manner, wherein an optimum value of the temperature of the cooling
water is estimated based on an operating condition up to the
present of the internal combustion engine, so that the degree of
valve opening of the valve opening adjustment unit is adjusted
based on an estimated value of a future temperature of the cooling
water at an inlet port of the internal combustion engine, and said
estimated optimum value (for example, refer to a first patent
document). According to the technique of this first patent
document, the temperature of the cooling water in the internal
combustion engine can be controlled to a more suitable
temperature.
[0003] On the other hand, there has been disclosed a technique
which uses, as cooling water for cooling an internal combustion
engine, a kind of cooling water of which the specific heat is
variable due to inclusion of particles therein which change in
phase from one of a solid phase state and a liquid phase state to
the other thereby to change a specific heat of a medium (for
example, refer to a second patent document).
CITATION LIST
Patent Literature
[0004] PTL 1: Japanese patent application laid-open No. 2007-100638
[0005] PTL 2: Japanese patent application laid-open No. 2009-044896
[0006] PTL 3: Japanese patent application laid-open No.
2005-325790
SUMMARY OF INVENTION
Technical Problem
[0007] In cases where the cooling water with a variable specific
heat disclosed in the second patent document is used, when control
is intended to be carried out on the basis of the temperature of
the cooling water using the technique disclosed in the first patent
document, the control can not be performed adequately because a
temperature range of the cooling water, which corresponds to a
state of the cooling water in which the specific heat of the
cooling water is variable (phase transition temperature zone), is
narrow. Specifically, even if the temperature of the cooling water
exists in the phase transition temperature zone by setting a target
temperature of the cooling water to be in the phase transition
temperature zone, there will be a possibility that if an amount of
received heat is high or large though it is within an allowable
range of the transition temperature zone, the specific heat of the
cooling water may immediately become low upon receiving a further
amount of heat, so that the temperature of the cooling water may
rapidly go up, thus resulting in an overheat. On the other hand, if
the target temperature of the cooling water is set, in order to
avoid this situation, to be lower than the phase transition
temperature zone, there will be a possibility that the oil in the
internal combustion engine may get cold and the friction of the
internal combustion engine may increase.
[0008] The present invention has been made in view of the
above-mentioned circumstances, and has for its object to provide a
technique in which in cases where cooling water with a variable
specific heat is used, a control valve for changing the temperature
of the cooling water is controlled adequately, so that effective
use of a phase transition temperature zone of the cooling water can
be made.
Solutions to Problem
[0009] In the present invention, the following construction is
adopted. That is, the present invention resides in a cooling water
temperature control apparatus for an internal combustion engine in
which cooling water is caused to circulate, said cooling water
having variable specific heat, said apparatus comprising:
[0010] a received heat amount calculation unit configured to
calculate an amount of received heat which is received by said
cooling water;
[0011] a control valve that is controlled to open and close
according to a command so as to change a circulation route or an
amount of circulation of said cooling water and to change the
temperature of said cooling water; and
[0012] a control unit configured to control said control valve
based on the amount of received heat which is calculated by said
received heat amount calculation unit.
[0013] In the case of the cooling water with a variable specific
heat, the temperature of the cooling water does not change in a
phase transition temperature zone of the cooling water even if the
amount of heat received by the cooling water changes to some
extent. The phase transition temperature zone of the cooling water
is a temperature zone corresponding to a state of the cooling water
in which the specific heat of the cooling water changes due to a
phase transition of particles in the cooling water, or the like. In
this phase transition temperature zone, even if a change occurs in
the amount of heat given to the cooling water (i.e., the amount of
received heat), a phase transition of the particles will occur, so
that the specific heat thereof will change, thus changing of the
temperature of the cooling water is suppressed. In other words, in
the phase transition temperature zone, an allowable range of the
amount of received heat is wide in which the cooling water remains
unchanged in its temperature. For this reason, when it is intended
to control the control valve on the basis of the temperature of the
cooling water, the control of the control valve may sometimes
become excessive and can not be carried out adequately because the
temperature range of the phase transition temperature zone is
narrow. This is because the amount of heat received by the cooling
water can not be determined on the basis of the target temperature
within the phase transition temperature zone. Even if the cooling
water is of the target temperature, there will be a case where the
amount of received heat thereof within the phase transition
temperature zone may be high or low. Accordingly, even if the
cooling water is of the target temperature, there will be a
possibility that the state of the cooling water may immediately
become out of the phase transition temperature zone when the amount
of received heat thereof changes. However, if the control valve is
controlled on the basis of the amount of received heat of the
cooling water, the range of the amount of received heat
corresponding to the phase transition temperature zone of the
cooling water is wide, and hence, by setting a target amount of
received heat, the control of the control valve can be finely
carried out in an appropriate manner within the phase transition
temperature zone.
[0014] According to this, for example, when the target amount of
received heat of the cooling water is set to be a value of the
receiving heat amount on a lower side of the phase transition
temperature zone, even if a further amount of heat is received, the
temperature of the cooling water will be maintained within the
phase transition temperature zone, and hence, it is possible to
avoid such a situation that the specific heat of the cooling water
may immediately become low thereby to cause the temperature of the
cooling water to go up rapidly, thus resulting in an overheat. In
addition, it is not necessary to set the target amount of received
heat of the cooling water to be an excessively low value, so it is
possible to avoid such a situation that the temperature of the
cooling water becomes too low, then the oil in the internal
combustion engine gets cold, resulting in increasing the friction
of the internal combustion engine.
[0015] According to the present invention, in cases where the
cooling water with its specific heat being variable is used, it is
possible to make effective use of the phase transition temperature
zone of the cooling water by controlling the control valve for
changing the temperature of the cooling water adequately.
[0016] Said received heat amount calculation unit preferably
calculates an inlet received heat amount which is received by said
cooling water at an inlet port from which said cooling water flows
into the internal combustion engine, and
[0017] said control unit preferably controls said control valve in
such a manner that said inlet received heat amount calculated by
said received heat amount calculation unit comes near to a lower
side starting value of received heat amount of the phase transition
temperature zone in which said cooling water is in a state in which
the specific heat thereof changes due to a phase transition of
particles.
[0018] According to this, it is possible to set a target inlet
received heat amount of the cooling water as a value of the
receiving heat amount near to the lower side starting value of the
phase transition temperature zone, and hence, even if an additional
amount of heat is further received by the cooling water in the
internal combustion engine, the temperature of the cooling water is
maintained within the phase transition temperature zone, thus
making it possible to avoid such a situation that the specific heat
of the cooling water may immediately become low thereby to cause
the temperature of the cooling water to go up rapidly, resulting in
an overheat.
[0019] Said received heat amount calculation unit preferably
calculates an outlet received heat amount which is received by said
cooling water at an outlet port from which said cooling water flows
out of the internal combustion engine, and
[0020] in cases where said outlet received heat amount calculated
by said received heat amount calculation unit becomes a high amount
of received heat in excess of an amount of received heat of said
phase transition temperature zone, said control unit preferably
controls said control valve so that said outlet received heat
amount is included in the range of the amount of received heat of
said phase transition temperature zone.
[0021] According to this, it is possible to set a target outlet
received heat amount of the cooling water as a value included in
the range of the amount of received heat of the phase transition
temperature zone, as a result the temperature of the cooling water
flowing out of the internal combustion engine is maintained within
the range of the temperature of the phase transition temperature
zone, thus making it possible to avoid such a situation that the
specific heat of the cooling water may immediately become low
thereby to cause the temperature of the cooling water to go up
rapidly, resulting in an overheat.
[0022] In cases where said received heat amount calculation unit
can not calculate the amount of received heat, it is preferable to
control said control valve in such a manner as to lower the
temperature of said cooling water.
[0023] According to this, in cases where the amount of received
heat can not be calculated, it is possible to lower the temperature
of the cooling water, thus making it possible to avoid the
temperature of the cooling water from going up to cause an
overheat.
Advantageous Effects of Invention
[0024] According to the present invention, in cases where cooling
water with its specific heat being variable is used, by controlling
the control valve for changing the temperature of the cooling water
adequately, it is possible to make effective use of the phase
transition temperature zone of the cooling water.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 is a view showing the schematic configuration of an
internal combustion engine in a first embodiment of the present
invention.
[0026] FIG. 2 is a view showing a model of cooling water in the
first embodiment.
[0027] FIG. 3 is a view showing the relation between a temperature
and a specific heat of the cooling water in the first
embodiment.
[0028] FIG. 4 is a view showing a characteristic curve of the
relation between an amount of received heat per unit amount of
cooling water at a reference temperature of 25 degrees C., and a
temperature of the cooling water in which a specific heat thereof
changes, in the first embodiment.
[0029] FIG. 5 is a view showing a model for amounts of received
heat in the internal combustion engine and various kinds of
equipment in the first embodiment.
[0030] FIG. 6 is a view showing a map for calculating a flow rate
of cooling water flowing through a radiator or a flow rate of
cooling water flowing through a bypass passage, in the first
embodiment.
[0031] FIG. 7 is a view showing a map for calculating a flow rate
of cooling water flowing through a heater core, a flow rate of
cooling water flowing through a reservoir tank, a flow rate of
cooling water flowing through an oil cooler, a flow rate of cooling
water flowing through a throttle valve and an EGR valve, or a flow
rate of cooling water flowing through an EGR cooler, in the first
embodiment.
[0032] FIG. 8 is a view showing a map for calculating an amount of
heat dissipation in the radiator or an amount of heat dissipation
in the reservoir tank, in the first embodiment.
[0033] FIG. 9 is a view showing a map for calculating an amount of
heat dissipation in the heater core in the first embodiment.
[0034] FIG. 10 is a view showing a map for calculating an amount of
heat dissipation in the oil cooler, an amount of heat dissipation
in the throttle valve and the EGR valve, or an amount of heat
dissipation in the EGR cooler, in the first embodiment.
[0035] FIG. 11 is a view showing the control of an electronic
thermostat based on an inlet received heat amount in the first
embodiment.
[0036] FIG. 12 is a view showing a problem in the control of the
electronic thermostat based on the inlet received heat amount in
the first embodiment.
[0037] FIG. 13 is a view showing the control of the electronic
thermostat based on an outlet received heat amount in the first
embodiment.
[0038] FIG. 14 is a view showing the control of the electronic
thermostat in cases where the inlet received heat amount or the
outlet received heat amount can not be calculated, in the first
embodiment.
[0039] FIG. 15 is a flow chart showing a cooling water temperature
control routine in the first embodiment.
DESCRIPTION OF EMBODIMENTS
[0040] In the following, a specific embodiment of the present
invention will be described.
First Embodiment
[0041] FIG. 1 is a view showing the schematic configuration of an
internal combustion engine to which a cooling water temperature
control apparatus for an internal combustion engine in a first
embodiment of the present invention is applied. In the internal
combustion engine 1 shown in FIG. 1, cooling water is caused to
circulate through a cooling water passage 2 so as to cool a
cylinder block and a cylinder head. As the cooling water passage 2,
there are provided a passage 2a by way of which the cooling water
flows through the radiator 3, a passage 2b by way of which the
cooling water flows through an oil cooler 4, a passage 2c by way of
which the cooling water flows through a throttle valve 5a and an
EGR valve 5b, a passage 2d by way of which the cooling water flows
through a reservoir tank 6, a passage 2e by way of which the
cooling water flows through a heater core 7, a passage 2f by way of
which the cooling water flows through an EGR cooler 8, and a bypass
passage 2g through which the cooling water flows as it is.
[0042] The radiator 3 serves to cool the cooling water by carrying
out heat exchange between the cooling water and outside air. The
oil cooler 4 is a water cooled oil cooler, and carries out heat
exchange between oil supplied to the internal combustion engine 1
and the cooling water thereby to cool the oil. The throttle valve
5a is a valve which serves to control an amount of intake air of
the internal combustion engine 1, and it is cooled by the cooling
water. The EGR valve 5b is a valve which serves to control an
amount of EGR gas which is a part of an exhaust gas which is caused
to flow back or return to the internal combustion engine 1, and it
is cooled by the cooling water. The reservoir tank 6 temporarily
stores the cooling water. The heater core 7 serves to warm the
cooling water. The EGR cooler 8 is a water cooling type EGR cooler,
and carries out heat exchange between the EGR gas returned to the
internal combustion engine 1 and the cooling water thereby to cool
the EGR gas.
[0043] The passage 2b, through which the cooling water coming from
a cylinder block flows through the oil cooler 4, is connected to
the passage 2a, through which the cooling water flows through the
radiator 3. In addition, the passage 2a, through which the cooling
water flows through the radiator 3, branches into the passage 2c,
through which the cooling water flows through the throttle valve 5a
and the EGR valve 5b, and the passage 2d, through which the cooling
water flows through the reservoir tank 6. The passage 2f, through
which the cooling water coming from the cylinder block flows
through the EGR cooler 8, is connected to the passage 2e, through
which the cooling water flows through the heater core 7.
[0044] An electronic thermostat 9 is arranged at a location at
which the passage 2a, through which the cooling water flows through
the radiator 3, and the bypass passage 2g are connected to each
other. The electronic thermostat 9 is a control valve which is
controlled to open and close in accordance with a command, and when
opened, it can change the flow path and the flow amount of the
cooling water so that the cooling water flows through the radiator
3, thereby making it possible to lower the temperature of the
cooling water. At this time, the amount of flow of the cooling
water in the bypass passage 2g is throttled or reduced. On the
contrary, by closing the electronic thermostat 9, the circulation
route (flow path) and the flow amount of the cooling water can be
changed, so that it becomes difficult for the cooling water to flow
through the radiator 3, thereby making it difficult for the
temperature of the cooling water to fall. At this time, the amount
of flow of the cooling water in the bypass passage 2g is increased.
The cooling water is sent into a water pump 10 at the downstream
side of the electronic thermostat 9. The water pump 10 pumps up the
cooling water, and supplies it into the cylinder block of the
internal combustion engine 1. In addition, a water temperature
sensor 11 is arranged at a location at which the cooling water
passage 2 is connected to an outlet port of the internal combustion
engine 1, so that the temperature of the cooling water flowing out
of the internal combustion engine 1 is detected by means of the
water temperature sensor 11.
[0045] Here, the cooling water flowing through the cooling water
passage 2 is cooling water of which the specific heat is variable.
That is, the cooling water is kind of cooling water of which the
specific heat is variable due to containing particles that make a
phase transition from one of a solid phase state and a liquid phase
state to the other thereby change the specific heat of a medium.
Here, note that as such particles, there can also be used those
which make a phase transition from one of a liquid phase state and
a gas phase state to the other, in addition to the particles which
make a phase transition from one of the solid phase state and the
liquid phase state to the other. The cooling water is one in which
particles formed by wrapping some substances in capsules are mixed
into a solvent of the cooling water, so that the internal
substances of the particles make a phase transition from a solid
state to a liquid state when the temperature thereof becomes equal
to or higher than a fixed level, as shown in FIG. 2. FIG. 2 is a
view showing a model of the cooling water in this embodiment. FIG.
3 is a view showing the relation between the temperature and the
specific heat of the cooling water in this embodiment. As shown in
FIG. 2, a plurality of particles in the cooling water make a phase
transition from one of a solid phase state and a liquid phase state
to the other, resulting in a variable specific heat region in which
the specific heat of the cooling water is changed due to the phase
transition of the plurality of particles, as shown in FIG. 3. This
variable specific heat region corresponds to a state of a phase
transition temperature zone in which even if an amount of heat is
applied to the cooling water, particles make a phase transition
thereby to change the specific heat of the cooling water (refer to
FIG. 4). FIG. 4 is a view showing a characteristic curve of the
relation between an amount of received heat per unit amount of
cooling water at a reference temperature of 25 degrees C., and the
temperature of the cooling water in which the specific heat thereof
changes, according to this embodiment. The phase transition
temperature zone shown in FIG. 4 is a temperature zone
corresponding to a state of the cooling water in which the specific
heat of the cooling water changes due to a phase transition of
particles in the cooling water from one of the solid phase state
and the liquid phase state to the other, and in this phase
transition temperature zone, even if a change occurs in the amount
of received heat applied to the cooling water, a phase transition
of particles will occur, so that the specific heat of the cooling
water will change, thus making it difficult for the temperature of
the cooling water to change. With the use of such cooling water, in
the warming up process of the internal combustion engine 1, by
making the specific heat of the cooling water lower than that in
the conventional art, the warming up characteristics of the
internal combustion engine 1 can be enhanced thereby to improve
fuel consumption or mileage, whereas after the warming up of the
engine, the specific heat of the cooling water becomes high in a
certain specific temperature range (i.e., the phase transition
temperature zone), so an allowable range of the amount of received
heat becomes larger, thus making it possible to avoid an overheat,
etc.
[0046] An ECU (electronic control unit) 12 is provided in
combination with this internal combustion engine 1. A variety of
kinds of sensors such as the water temperature sensor 11 and so on
are connected to the ECU 12 through electrical wiring, so that
output signals of these various sensors are inputted to the ECU 12.
On the other hand, the throttle valve 5a, the EGR valve 5b, the
heater core 7, the electronic thermostat 9, the water pump 10, and
so on are connected to the ECU 12 through electrical wiring, so
that these component parts are controlled by means of the ECU
12.
[0047] (Cooling Water Temperature Control)
[0048] In the past, an electronic thermostat has been controlled on
the basis of the temperature of cooling water has been carried out.
For example, a future optimal temperature of the cooling water is
estimated, and the electronic thermostat is controlled in such a
manner that the temperature of the cooling water is adjusted to
become the optimal temperature thus estimated. However, in cases
where a cooling water with its specific heat being variable as in
this embodiment is used as cooling water, there has been a problem
that the advantage of such a cooling water could not be exploited
effectively.
[0049] That is, in the case of the cooling water with a variable
specific heat, the temperature of the cooling water does not change
in the phase transition temperature zone of the cooling water even
if the amount of heat received by the cooling water changes to some
extent. In other words, in the phase transition temperature zone of
the cooling water, the allowable range of the amount of received
heat is wide in which the cooling water remains unchanged in its
temperature. For this reason, when it is intended to control the
electronic thermostat on the basis of the temperature of the
cooling water as in the past, the control of the electronic
thermostat may sometimes become excessive and can not be carried
out in an appropriate manner because the temperature range of the
phase transition temperature zone of the cooling water is narrow.
This is because with a target temperature in the phase transition
temperature zone of the cooling water, the amount of heat received
by the cooling water can not be determined, so there will be a case
where even if the cooling water is at the target temperature, the
amount of received heat thereof lying within the phase transition
temperature zone may be high (at point A in FIG. 4) or low. The
point A shown in FIG. 4 corresponds to a state of the cooling water
in which the cooling water at the outlet port of the internal
combustion engine is of a target temperature within the phase
transition temperature zone, and the amount of received heat of the
cooling water is high within the phase transition temperature zone.
Accordingly, there will be a possibility that even if the cooling
water is of the target temperature within the phase transition
temperature zone, when the amount of received heat thereof changes,
the state of the cooling water may immediately become out of the
phase transition temperature zone. For example, in the case of the
point A in FIG. 4, when the amount of received heat increases, such
as when a high load is rapidly applied, the temperature of the
cooling water will exceed the phase transition temperature zone,
and the specific heat of the cooling water will immediately become
low, so that the temperature of the cooling water will go up
rapidly, thus resulting in an overheat.
[0050] In order to avoid such an overheat, it is considered that
the target temperature of the cooling water may be set lower than
the phase transition temperature zone. A point B shown in FIG. 4
represents a state of the cooling water in the case where the
cooling water at the outlet port of the internal combustion engine
is of a target temperature lower than the phase transition
temperature zone. However, in the case of the point B in FIG. 4,
the temperature of the cooling water at the inlet port of the
internal combustion engine, which has become low after having
circulated through the cooling water passage, becomes excessively
lower than the phase transition temperature zone, so that the oil
in the internal combustion engine gets cold, thereby increasing the
friction of the internal combustion engine.
[0051] As described above, in the case of using the cooling water
of which the specific heat is variable, when the electronic
thermostat was controlled based on the temperature of the cooling
water, the advantage of the cooling water of which the specific
heat is variable could not be utilized efficiently, so that the
electronic thermostat was not able to be controlled in an
appropriate manner. For this reason, it is possible to make
effective use of the phase transition temperature zone of the
cooling water.
[0052] Accordingly in this embodiment, the amount of heat received
by the cooling water is calculated, and the electronic thermostat 9
is controlled based on the amount of received heat thus calculated.
In this case, the range of the amount of received heat of the phase
transition temperature zone of the cooling water is wide, and
hence, by setting a target amount of received heat, the control of
the control valve can be finely carried out in an appropriate
manner in a range including the phase transition temperature
zone.
[0053] As specific control in this embodiment, an inlet received
heat amount, which is received by the cooling water at the inlet
port from which said cooling water flows into the internal
combustion engine, is calculated. Then, the electronic thermostat 9
is controlled in such a manner that the inlet received heat amount
thus calculated comes near to a lower side starting value of the
received heat amount of the phase transition temperature zone in
which the cooling water is in a state in which the particles make a
phase transition thereby the specific heat of the cooling water
changes.
[0054] FIG. 5 is a view showing a model for amounts of received
heat in the internal combustion engine and various kinds of
equipment according to this embodiment. As shown in FIG. 5, the
inlet received heat amount of the internal combustion engine 1 is
calculated from an outlet received heat amount which is received at
an output port from which the cooling water flows out of the
internal combustion engine, amounts of transfer heat of various
kinds of equipment, and flow rates of the cooling water in the
various kinds of equipment. The ECU 12, which calculates the inlet
received heat amount, corresponds to a received heat amount
calculation unit in the present invention. The amounts of transfer
heat of the various kinds of equipment are transfer amounts of heat
of the cooling water flowing through the radiator 3, the bypass
passage 2g, the heater core 7, the reservoir tank 6, the oil cooler
4, the throttle valve 5a, the EGR valve 5b, and the EGR cooler 8,
respectively. The flow rates in the various kinds of equipment are
flow rates of the cooling water flowing through the radiator 3, the
bypass passage 2g, the heater core 7, the reservoir tank 6, the oil
cooler 4, the throttle valve 5a, the EGR valve 5b, and the EGR
cooler 8, respectively.
[0055] The calculation method of the inlet received heat amount of
the internal combustion engine 1 is explained hereinafter. First,
an outlet received heat amount is calculated which is received by
the cooling water at the outlet port from which the cooling water
flows out of the internal combustion engine 1. As shown in FIG. 4,
an outlet received heat amount Qengout can be derived by looking up
in the characteristic curve of the cooling water a temperature
Tengout of the cooling water detected by the water temperature
sensor 11 at the outlet port of the internal combustion engine 1.
The ECU 12, which calculates the outlet received heat amount,
corresponds to a received heat amount calculation unit in the
present invention.
[0056] Next, the flow rates in the various kinds of equipment will
be calculated. FIG. 6 is a view showing a map for calculating a
flow rate Grad of cooling water flowing through the radiator 3 or a
flow rate Gby of cooling water flowing through the bypass passage
2g according to this embodiment. Grad or Gby depends on the degree
of valve opening of the electronic thermostat 9 and the number of
revolutions per unit time of the water pump 10, and hence, can be
calculated by looking up these values in the map shown in FIG. 6.
Here, as the degree of valve opening of the electronic thermostat
9, there can be appropriated or used the degree of opening thereof
for control. As the number of revolutions per unit time of the
water pump 10, there can be used a value proportional to engine rpm
in the case of a mechanically operated water pump, whereas in the
case of an electrically operated (motorized) water pump, there can
be used the number of revolutions per unit time of a drive motor.
FIG. 7 is a view showing a map for calculating a flow rate Cheat of
cooling water flowing through the heater core 7, a flow rate Gres
of cooling water flowing through the reservoir tank 6, a flow rate
Goil of cooling water flowing through the oil cooler 4, a flow rate
Gthr of cooling water flowing through the throttle valve 5a and the
EGR valve 5b, or a flow rate Gegr of cooling water flowing through
the EGR cooler 8, according to this embodiment. Cheat, Gres, Goil,
Gthr, or Gegr depends on the number of revolutions per unit time of
the water pump 10, and hence, can be calculated by looking up these
values in the map shown in FIG. 7.
[0057] Then, the amounts of transfer heat in the various kinds of
equipment will be calculated. FIG. 8 is a view showing a map for
calculating an amount of heat dissipation .DELTA.Qrad in the
radiator 3 or an amount of heat dissipation 66 Qres in the
reservoir tank 6 according to this embodiment. .DELTA.Qrad or
.DELTA.Qres depends on the speed of wind or air which is received
by each equipment, and the flow rate of cooling water flowing
through each of the various kinds of equipment, and hence, can be
calculated by looking up these values in the map shown in FIG. 8.
Here, as the wind speed, there can be used a value which is
obtained by adding the speed of a vehicle and the wind speed of a
cooling fan of the vehicle, or the like. FIG. 9 is a view showing a
map for calculating an amount of heat dissipation .DELTA.Qheat in
the heater core 7 according to this embodiment. .DELTA.Qheat
depends on an air volume of a heater and the flow rate of cooling
water flowing through the heater core 7, and hence, can be
calculated by looking up these values in the map shown in FIG. 9.
FIG. 10 is a view showing a map for calculating an amount of heat
dissipation .DELTA.Qoil in the oil cooler 4, an amount of heat
dissipation .DELTA.Qthr in the throttle valve 5a and the EGR valve
5b, or an amount of heat dissipation .DELTA.Qegr in the EGR cooler
8 according to this embodiment. .DELTA.Qoil, .DELTA.Qthr, or
.DELTA.Qegr depends on the temperature of cooling water at the
outlet port of the internal combustion engine 1 detected by the
water temperature sensor 11 and the flow rate of cooling water
flowing through each of the various kinds of equipment, and hence,
can be calculated by looking up these values in the map shown in
FIG. 10. Then, the amounts of received heat of the various kinds of
equipment are calculated by deducting the respective amounts of
heat dissipation of the various kinds of equipment from the outlet
received heat amount. That is, the amount of received heat Qrad in
the radiator 3 is equal to Qengout-.DELTA.Qrad. The amount of
received heat Qres in the reservoir tank 6 is equal to
Qengout-.DELTA.Qres. Here, note that there is almost no transfer of
heat in the bypass passage 2g, and hence, the amount of received
heat Qby in the bypass passage 2g is equal to Qengout. The amount
of received heat Qheat in the heater core 7 is equal to
Qengout-.DELTA.Qheat. The amount of received heat Qoil in the oil
cooler 4 is equal to Qengout-.DELTA.Qoil. The amount of received
heat Qthr in the throttle valve 5a and the EGR valve 5b is equal to
Qengout-.DELTA.Qthr. The amount of received heat Qegr in the EGR
cooler 8 is equal to Qengout-.DELTA.Qegr.
[0058] Thereafter, an inlet received heat amount is calculated
which is received by the cooling water at the inlet port from which
the cooling water flows into the internal combustion engine 1. An
inlet received heat amount Qengin is obtained by dividing a total
sum of products of the amounts of received heat of the various
kinds of equipment and the respective flow rates in the various
kinds of equipment by the amounts of received heat of the various
kinds of equipment. That is, the inlet received heat amount Qengin
is equal to
(Qrad.times.Grad+Qres.times.Gres+Qby.times.Gby+Qheat.times.Gheat+Qoil.tim-
es.Goil+Qthr.times.Gthr+Qegr.times.Gegr)/(Qrad+Qres+Qby+Qheat+Qoil+Qthr+Qe-
gr).
[0059] FIG. 11 is a view showing the control of the electronic
thermostat 9 based on the inlet received heat amount according to
this embodiment. As shown in FIG. 11, the electronic thermostat 9
is controlled in such a manner that the inlet received heat amount
calculated in the above-mentioned manner comes near to a lower side
starting value of received heat amount of the phase transition
temperature zone. Stated in another way, the electronic thermostat
9 is controlled in such a manner that the inlet received heat
amount thus calculated comes near to a target received heat amount
which is the lower side starting value of received heat amount of
the phase transition temperature zone. The lower side starting
value of received heat amount of the phase transition temperature
zone has been able to be set in advance by experiments,
verifications, etc. The ECU 12, which controls the electronic
thermostat 9, corresponds to a control unit of the present
invention. As a result of this, when the inlet received heat amount
is lower than the lower side starting value of received heat amount
of the phase transition temperature zone, the electronic thermostat
9 is controlled to a closed side so as to reduce the amount of the
cooling water flowing into the radiator 3. On the other hand, when
the inlet received heat amount is higher than the lower side
starting value of received heat amount of the phase transition
temperature zone, the electronic thermostat 9 is controlled to an
opening side so as to increase the amount of the cooling water
flowing into the radiator 3.
[0060] According to this, it is possible to set the target received
heat amount of the cooling water to the lower side starting value
of received heat amount of the phase transition temperature zone,
and hence, even if an additional amount of heat is further received
by the cooling water, the temperature of the cooling water is
maintained within the phase transition temperature zone, thus
making it possible to avoid such a situation that the specific heat
of the cooling water may immediately become low thereby to cause
the temperature of the cooling water to go up rapidly, resulting in
an overheat. In addition, it is not necessary to set the target
amount of received heat of the cooling water to be an excessively
low value, so it is possible to avoid such a situation that the
temperature of the cooling water becomes too low, then the oil in
the internal combustion engine from gets cold, resulting in
increasing the friction of the internal combustion engine.
[0061] According to this embodiment, in cases where the cooling
water with its specific heat being variable is used, it is possible
to make effective use of the phase transition temperature zone of
the cooling water by controlling the control valve for changing the
temperature of the cooling water in an appropriate manner.
[0062] FIG. 12 is a view showing a problem with the control of the
electronic thermostat 9 based on the inlet received heat amount
according to this embodiment. When the electronic thermostat 9 is
controlled based on the inlet received heat amount, as shown in
FIG. 12, the outlet received heat amount may become a high or large
amount of received heat in excess of the phase transition
temperature zone. Such a case may occur at the time of a high load,
etc., thus easily causing an overheat.
[0063] Accordingly, in cases where the outlet received heat amount
becomes a high or large amount of received heat in excess of an
amount of received heat of the phase transition temperature zone,
the electronic thermostat 9 is controlled in such a manner that the
outlet received heat amount is brought near to a higher amount of
received heat within the phase transition temperature zone. Here,
note that the electronic thermostat 9 may be controlled in such a
manner that the outlet received heat amount is included in a range
of amount of received heat corresponding to the phase transition
temperature zone.
[0064] As specific control in this embodiment, when the electronic
thermostat 9 is controlled in such a manner that the inlet received
heat amount comes near to the lower side starting value of received
heat amount of the phase transition temperature zone, the outlet
received heat amount may become a high amount of received heat in
excess of an amount of received heat of the phase transition
temperature zone, as shown in FIG. 12. In that case, the control
based on the inlet received heat amount is stopped, and the
electronic thermostat 9 is controlled in such a manner that the
outlet received heat amount comes near to a higher received heat
amount within the phase transition temperature zone, as shown in
FIG. 13. FIG. 13 is a view showing the control of the electronic
thermostat 9 based on the outlet received heat amount according to
this embodiment. Here, the reason for bringing the outlet received
heat amount near to a higher amount of received heat within the
phase transition temperature zone is because the outlet received
heat amount can be maintained to be an amount of received heat
higher or larger than the inlet received heat amount, so that
effective use of the phase transition temperature zone of the
cooling water can be made.
[0065] According to this, it is possible to set the target outlet
received heat amount of the cooling water to a higher or larger
amount of received heat within the phase transition temperature
zone, as a result of which the temperature of the cooling water
flowing out of the internal combustion engine is maintained within
the phase transition temperature zone, thus making it possible to
avoid such a situation that the specific heat of the cooling water
may immediately become low thereby to cause the temperature of the
cooling water to go up rapidly, resulting in an overheat.
[0066] As mentioned above, when the electronic thermostat 9 is
controlled based on the inlet received heat amount or the outlet
received heat amount, there may be a case where it becomes
impossible to calculate the inlet received heat amount or the
outlet received heat amount due to some cause such as sensor
abnormality, engine abnormality, and abnormality of the various
kinds of equipment, etc. In this case, it becomes impossible to
control the electronic thermostat 9 based on the inlet received
heat amount or the outlet received heat amount.
[0067] Accordingly, in cases where the inlet received heat amount
or the outlet received heat amount can not be calculated, the
electronic thermostat 9 is controlled in such a manner as to lower
the temperature of said cooling water.
[0068] FIG. 14 is a view showing the control of the electronic
thermostat 9 in cases where the inlet received heat amount or the
outlet received heat amount can not be calculated, according to
this embodiment. As specific control in this embodiment, the
electronic thermostat 9 is controlled to an opening side at a
degree of opening equal to or more than a fixed or prescribed
degree of opening so that an amount of cooling water equal to or
more than a fixed or prescribed amount is caused to circulate
through the radiator 3 so as to make the outlet received heat
amount lower or smaller value than the range corresponding to the
phase transition temperature zone. Here, note that this is an
abnormal situation, and the outlet received heat amount may be made
lower than that in the case shown in FIG. 14, and hence, the
electronic thermostat 9 may be controlled to a fully opened state
so that the whole amount of cooling water to be able to circulate
is caused to flow through the radiator 3.
[0069] According to this, in cases where the amount of received
heat can not be calculated, the temperature of the cooling water is
made to fall, thus making it possible to avoid the temperature of
the cooling water from going up to cause an overheat.
[0070] (Cooling Water Temperature Control Routine)
[0071] Reference will be made to a cooling water temperature
control routine in the ECU 12 based on a flow chart shown in FIG.
15. FIG. 15 is a flow chart showing the cooling water temperature
control routine according to this embodiment. This routine is
carried out by means of the ECU 12. The ECU 12 executing this
routine corresponds to a control unit of the present invention.
[0072] When the routine shown in FIG. 15 is started, in step S101,
an inlet received heat amount is calculated. In this case, an
outlet received heat amount is also calculated. In S102, it is
determined whether an error (NG) has occurred in the calculation of
the inlet received heat amount and the outlet received heat amount
in step S101. In cases where an affirmative determination is made
in step S102, the routine advances to step S106. On the other hand,
in cases where a negative determination is made in step S102, the
routine shifts to step S103. In step S103, it is determined whether
the outlet received heat amount becomes a high amount of received
heat in excess of the phase transition temperature zone. In cases
where an affirmative determination is made in step S103, the
routine advances to step S105. On the other hand, in cases where a
negative determination is made in step S103, the routine advances
to step S104. In step S104, the electronic thermostat 9 is
controlled in such a manner that the inlet received heat amount
comes near to the lower side starting value of received heat amount
of the phase transition temperature zone. In step S105, the
electronic thermostat 9 is controlled in such a manner that the
outlet received heat amount comes near to a higher received heat
amount within the phase transition temperature zone. In S106, the
electronic thermostat 9 is controlled so as to lower the
temperature of the cooling water. After the processing of steps
S104 through S106, this routine is once ended.
[0073] With this routine as described above, by controlling the
control valve for changing the temperature of the cooling water in
an appropriate manner, it is possible to make effective use of the
phase transition temperature zone of the cooling water as much as
possible.
[0074] <Others>
[0075] The cooling water temperature control apparatus for an
internal combustion engine according to the present invention is
not limited to the embodiment as mentioned above, but can be
subjected to various changes and modifications within the scope not
departing from the gist of the present invention.
REFERENCE SIGNS LIST
[0076] 1 internal combustion engine [0077] 2 cooling water passage
[0078] 3 radiator [0079] 4 oil cooler [0080] 5a throttle valve
[0081] 5b EGR valve [0082] 6 reservoir tank [0083] 7 heater core
[0084] 8 EGR cooler [0085] 9 electronic thermostat [0086] 10 water
pump [0087] 11 water temperature sensor [0088] 12 ECU
* * * * *