U.S. patent application number 13/882357 was filed with the patent office on 2013-08-29 for cooling system for an internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Koichiro Nakatani, Takenori Saoda, Akira Yamashita. Invention is credited to Koichiro Nakatani, Takenori Saoda, Akira Yamashita.
Application Number | 20130220242 13/882357 |
Document ID | / |
Family ID | 46024102 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130220242 |
Kind Code |
A1 |
Nakatani; Koichiro ; et
al. |
August 29, 2013 |
COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE
Abstract
An opening and closing condition of a thermostat is optimized.
In a cooling system for an internal combustion engine in which a
cooling water, in which its specific heat becomes larger at a
predetermined temperature than at other temperatures, is caused to
circulates through a cooling water passage, there are provided a
radiator, a bypass passage that bypasses the radiator, and a
thermostat that interrupts the circulation of the cooling water to
the radiator and circulates the cooling water to the bypass passage
when it closes, and circulates the cooling water to at least the
radiator when it opens, wherein the thermostat is set to open at
the time when the temperature of the cooling water is higher than a
predetermined temperature.
Inventors: |
Nakatani; Koichiro;
(Mishima-shi, JP) ; Yamashita; Akira;
(Mishima-shi, JP) ; Saoda; Takenori; (Numazu-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nakatani; Koichiro
Yamashita; Akira
Saoda; Takenori |
Mishima-shi
Mishima-shi
Numazu-shi |
|
JP
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
46024102 |
Appl. No.: |
13/882357 |
Filed: |
November 1, 2010 |
PCT Filed: |
November 1, 2010 |
PCT NO: |
PCT/JP2010/069434 |
371 Date: |
April 29, 2013 |
Current U.S.
Class: |
123/41.1 |
Current CPC
Class: |
F01P 3/00 20130101; F01P
7/167 20130101 |
Class at
Publication: |
123/41.1 |
International
Class: |
F01P 3/00 20060101
F01P003/00 |
Claims
1. A cooling system for an internal combustion engine in which a
cooling water, in which its specific heat becomes larger at a
predetermined temperature than at other temperatures, is caused to
circulates through a cooling water passage, said cooling system
comprising: a radiator that is arranged in said cooling water
passage and takes heat from said cooling water; a bypass passage
that bypasses said radiator; and a thermostat that interrupts the
circulation of the cooling water to said radiator and circulates
the cooling water to said bypass passage when it closes, and
circulates the cooling water to at least said radiator when it
opens; wherein said cooling system is provided with: an operation
region in which said thermostat opens when the temperature of the
cooling water flowing out of said internal combustion engine into
said cooling water passage is equal to or more than a prescribed
temperature which is higher than said predetermined temperature,
and when the temperature of the cooling water flowing out of said
cooling water passage into said internal combustion engine is
higher than said predetermined temperature, said operation region
being decided by the number of engine revolutions per unit time and
the engine load; and an operation region in which at least one of
the number of engine revolutions per minute and the engine load is
higher than that in said first-mentioned operation region, and in
which said thermostat opens when the temperature of the cooling
water flowing out of said internal combustion engine into said
cooling water passage is equal to or more than a prescribed
temperature which is higher than said predetermined temperature,
and when the temperature of the cooling water flowing out of said
cooling water passage into said internal combustion engine is lower
than said predetermined temperature.
2-4. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a cooling system for an
internal combustion engine.
BACKGROUND ART
[0002] There has been known a technique in which the temperature of
cooling water is set in such a manner that an internal combustion
engine is not overheated, and an electronic thermostat is
controlled so that the cooling water becomes a cooling water
temperature thus set (for example, refer to a first patent
document). In addition, there has also been known a cooling water
in which its specific heat changes at a predetermined temperature
(for example, refer to a second patent document). This cooling
water is prepared by dispersing in a liquid capsules in each of
which a substance adapted to cause a phase transition is
filled.
[0003] Here, in cases where the cooling water, in which its
specific heat changes at the predetermined temperature, is used in
a system in which the electronic thermostat is controlled so that
the cooling water becomes the thus set cooling water temperature,
if the electronic thermostat is controlled in the manner as
conventional, it can not be said that the characteristic of the
cooling water that its specific heat changes is utilized to a
sufficient extent.
PRIOR ART REFERENCES
Patent Documents
[0004] [First Patent Document] Japanese patent application
laid-open No. 2004-353602 [Second Patent Document] Japanese patent
application laid-open No. 2010-168538
SUMMARY OF THE INVENTION
To be Solved by the Invention
[0005] The present invention has been made in view of the problems
as mentioned above, and has for its object to provide a technique
to optimize the opening and closing (on and off) condition of a
thermostat.
Means for Solving the Problems
[0006] In order to achieve the above-mentioned object, a cooling
system for an internal combustion engine according to the present
invention, in which a cooling water, in which its specific heat
becomes larger at a predetermined temperature than at other
temperatures, is caused to circulate through a cooling water
passage, is provided with:
[0007] a radiator that is arranged in said cooling water passage
and takes heat from said cooling water;
[0008] a bypass passage that bypasses said radiator; and
[0009] a thermostat that interrupts the circulation of the cooling
water to said radiator and circulates the cooling water to said
bypass passage when it closes, and circulates the cooling water to
at least said radiator when it opens;
[0010] wherein said thermostat opens when the temperature of said
cooling water is higher than said predetermined temperature.
[0011] The predetermined temperature can be a temperature at which
a structural phase transition occurs in a substance included in the
cooling water, for example. That is, heat is released or heat is
absorbed due to the structural phase transition, so the specific
heat of the cooling water becomes higher at the temperature at
which the structural phase transition occurs. For this reason, at
the predetermined temperature, the temperature of the cooling water
becomes substantially constant, even if there is some incoming and
outgoing of heat.
[0012] Here, when the thermostat opens, the cooling water will flow
to the radiator, so the temperature rise of the cooling water is
suppressed. If the thermostat opens at the time when the
temperature of the cooling water is lower than the predetermined
temperature, the temperature of the cooling water will be
suppressed from going up to the predetermined temperature, and
hence, the characteristic of the specific heat becoming larger is
not utilized. On the other hand, if the thermostat is set to open
when the temperature of the cooling water is higher than the
predetermined temperature, the specific heat of the cooling water
can become larger when the thermostat is in a closed state, so that
the characteristic of the specific heat becoming larger can be
utilized. That is, the temperature of the cooling water can be
maintained constant when the thermostat is in the closed state, and
hence, it becomes unnecessary to perform control corresponding to
the variation in the temperature of the cooling water. For this
reason, the operating state of the internal combustion engine can
be stabilized. In this manner, the opening and closing condition of
the thermostat can be optimized.
[0013] In addition, in the present invention, there can be
provided
[0014] an operation region in which said thermostat opens when the
temperature of said cooling water is higher than said predetermined
temperature, and
[0015] an operation region in which said thermostat opens when the
temperature of said cooling water is lower than said predetermined
temperature.
[0016] That is, the cooling capacity required for the cooling
system varies in accordance with the operating state of the
internal combustion engine, so it is possible to set the
temperature at which the thermostat opens according to the required
cooling capacity. As a result of this, it becomes possible to carry
out the temperature control of the cooling water according to the
operating regions.
[0017] Moreover, in the present invention, said thermostat may open
when the temperature of the cooling water flowing out of said
internal combustion engine into said cooling water passage is
higher than said predetermined temperature.
[0018] Because the cooling water flowing out of the internal
combustion engine into the cooling water passage is the cooling
water immediately after receiving heat from the internal combustion
engine, the temperature thereof is difficult to go up until the
cooling water flows into the internal combustion engine again. That
is, the temperature of the cooling water flowing out of the
internal combustion engine into the cooling water passage is higher
than that of cooling water in other parts. For this reason, if the
thermostat opens according to the temperature of the cooling water
flowing out of the internal combustion engine into the cooling
water passage, it will be possible to suppress overheating of the
internal combustion engine, and at the same time to utilize the
characteristic that the specific heat of the cooling water becomes
larger.
[0019] Further, in the present invention, there can be provided
[0020] an operation region in which said thermostat opens when the
temperature of the cooling water flowing out of said internal
combustion engine into said cooling water passage is higher than
said predetermined temperature, and when the temperature of the
cooling water flowing out of said cooling water passage into said
internal combustion engine is higher than said predetermined
temperature, and
[0021] an operation region in which said thermostat opens when the
temperature of the cooling water flowing out of said internal
combustion engine into said cooling water passage is higher than
said predetermined temperature, and when the temperature of the
cooling water flowing out of said cooling water passage into said
internal combustion engine is lower than said predetermined
temperature.
[0022] Here, because the cooling water flowing out of the cooling
water passage into the internal combustion engine is the cooling
water immediately before receiving heat from the internal
combustion engine, the temperature thereof is low. On the other
hand, because the cooling water flowing out of the internal
combustion engine into the cooling water passage is the cooling
water immediately after receiving heat from the internal combustion
engine, the temperature thereof is high. In this manner, even among
the cooling water, there exist a part in which the temperature
thereof is high, and a part in which the temperature thereof is
low.
[0023] Then, when the temperature of the cooling water flowing out
of the cooling water passage into the internal combustion engine is
higher than the predetermined temperature, it can be said that the
temperature of the cooling water as a whole is higher than the
predetermined temperature. For this reason, if the thermostat is
set to open when the temperature of the cooling water flowing out
of the cooling water passage into the internal combustion engine is
higher than the predetermined temperature, the temperature of the
cooling water as a whole will be maintained in a state higher than
the predetermined temperature. For example, in an operation region
where the cooling capacity to be required is low, it becomes
possible to make the temperature of the cooling water as a whole
higher than the predetermined temperature, as a result of which
fuel economy can be improved. Here, note that the operation region
where the cooling capacity to be required is low may also be a
region where the internal combustion engine is operated at low
rotation speed and under low load.
[0024] On the other hand, if said thermostat opens when the
temperature of the cooling water flowing out of said internal
combustion engine into said cooling water passage is higher than
said predetermined temperature, and when the temperature of the
cooling water flowing out of said cooling water passage into said
internal combustion engine is lower than said predetermined
temperature, the temperature of the cooling water within the
internal combustion engine will become the predetermined
temperature. For this reason, the specific heat of the cooling
water within the internal combustion engine becomes high, so the
temperature rise of the cooling water can be suppressed. For
example, in an operation region where the cooling capacity to be
required is high, the specific heat of the cooling water within the
internal combustion engine becomes high, whereby the temperature of
the cooling water within the internal combustion engine can be made
constant. As a result of this, the operating state of the internal
combustion engine can be stabilized. Here, note that the operation
region where the cooling capacity to be required is high may also
be a region where the internal combustion engine is operated at
high rotation speed and under high load.
Effect of the Invention
[0025] According to the present invention, it is possible to
optimize the opening and closing condition of the thermostat.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] [FIG. 1] is a view showing the schematic construction of a
cooling system for an internal combustion engine according to an
embodiment of the present invention.
[0027] [FIG. 2] is a time chart showing the change over time of an
outlet side temperature at the time of warming up of the internal
combustion engine.
[0028] [FIG. 3] is a view showing the relation between the
temperature of cooling water and the specific heat of the cooling
water.
[0029] [FIG. 4] is a view showing the relation among the number of
engine revolutions per minute, the engine load, and the temperature
at which a thermostat opens.
MODE FOR CARRYING OUT THE INVENTION
[0030] Hereinafter, reference will be made to a specific embodiment
of a cooling system for an internal combustion engine according to
the present invention based on the attached drawings.
First Embodiment
[0031] FIG. 1 is a view showing the schematic construction of a
cooling system for an internal combustion engine according to this
embodiment of the present invention. An internal combustion engine
1 shown in FIG. 1 is a water cooled type internal combustion
engine.
[0032] A water jacket 2 for circulating cooling water is formed in
the interior of the internal combustion engine 1. In addition, a
first cooling water passage 11 and a second cooling water passage
12 are connected to the internal combustion engine 1. A radiator 13
and a bypass passage 14 are connected to these first cooling water
passage 11 and second cooling water passage 12.
[0033] The first cooling water passage 11 provides a connection
between an outlet side of the water jacket 2 and an inlet side of
the radiator 13. That is, the first cooling water passage 11 is a
passage for discharging the cooling water from the water jacket 2.
Also, the second cooling water passage 12 provides a connection
between an outlet side of the radiator 13 and an inlet side of the
water jacket 2. That is, the second cooling water passage 12 is a
passage for supplying the cooling water to the water jacket 2.
[0034] In addition, a water pump 3, which serves to deliver the
cooling water from the side of the second cooling water passage 12
to the side of the water jacket 2, is formed at a connection part
between the second cooling water passage 12 and the water jacket
2.
[0035] The bypass passage 14 serves to place the first cooling
water passage 11 and the second cooling water passage 12 in
communication with each other, thereby bypassing the radiator
13.
[0036] Moreover, a thermostat 15 of an electronic controlled type
is arranged in the second cooling water passage 12 at a location
near the radiator 13 from the connection part between the second
cooling water passage 12 and the bypass passage 14. The degree of
opening of this thermostat 15 is adjusted according to a signal
from an ECU 30 which will be described later. Then, the amount of
the cooling water supplied to the radiator 13 is adjusted by
controlling the degree of opening of the thermostat 15.
[0037] When the thermostat 15 is in a closed state, the cooling
water having flowed out of the water jacket 2 into the first
cooling water passage 11 is again sent to the water jacket 2 by way
of the bypass passage 14. By such a circulation of the cooling
water, the cooling water is warmed in a gradual manner, so that the
warming up of the internal combustion engine 1 is facilitated.
[0038] In addition, when the thermostat 15 is open, the cooling
water circulates by way of the radiator 13 and the bypass passage
14. Here, note that without regard to the state of the thermostat
15, the cooling water also circulates to those parts other than the
radiator 13 and the bypass passage 14, which are omitted in FIG.
1.
[0039] Further, an outlet side temperature sensor 31, which serves
to measure the temperature of the cooling water flowing out of the
water jacket 2 (hereinafter, referred to as an outlet side
temperature), is mounted on the first cooling water passage 11 at a
location between its connection part with the water jacket 2 and
its connection part with the bypass passage 14. Also, an inlet side
temperature sensor 32, which serves to measure the temperature of
the cooling water flowing into the water jacket 2 (hereinafter,
referred to as an inlet side temperature), is mounted on the second
cooling water passage 12 at a location between its connection part
with the water jacket 2 and its connection part with the bypass
passage 14.
[0040] In the internal combustion engine 1 constructed as stated
above, there is arranged in combination therewith the ECU 30 which
is an electronic control unit for controlling the internal
combustion engine 1. This ECU 30 controls the internal combustion
engine 1 in accordance with the operating conditions of the
internal combustion engine 1 and/or driver's requirements.
[0041] In addition, besides the above-mentioned sensors, an
accelerator opening sensor 33, which serves to detect an engine
load by outputting an electrical signal corresponding to a degree
of opening (i.e., an amount of depression) of an accelerator pedal,
and a crank position sensor 34, which serves to detect the number
of revolutions per minute of the engine, are connected to the ECU
30 through electrical wiring, and, output signals of these sensors
are inputted to the ECU 30. On the other hand, the thermostat 15 is
connected to the ECU 30 through electrical wiring, so that this
thermostat 15 is controlled by the ECU 30.
[0042] Here, the cooling water in this embodiment has a specific
heat which changes at a predetermined temperature. For example, the
cooling water is composed of including a substance which performs a
phase transition from a solid to a liquid or from a liquid to a
solid, at the predetermined temperature. That is, when the
temperature of the cooling water becomes the predetermined
temperature in the process of becoming higher, the substance
included in the cooling water will change from a solid to a liquid,
and at this time, will absorb heat from the surroundings. On the
other hand, when the temperature of the cooling water becomes the
predetermined temperature in the process of becoming lower, the
substance included in the cooling water will change from a liquid
to a solid, and at this time, will release heat to the
surroundings. In this manner, at the time when a phase transition
is carried out between a liquid and a solid, the specific heat of
the cooling water changes.
[0043] FIG. 2 is a time chart showing the change over time of the
outlet side temperature at the time of warming up of the internal
combustion engine 1. In a period of time from A to B in FIG. 2, the
outlet side temperature of the cooling water becomes constant at a
predetermined temperature D. In addition, at a time point indicated
by C, the outlet side temperature of the cooling water becomes an
opening temperature E of the thermostat 15, and so the thermostat
15 is open. As a result of this, the cooling water flows through
the radiator 13, so that the outlet side temperature of the cooling
water becomes substantially constant.
[0044] Further, FIG. 3 is a view showing the relation between the
cooling water temperature and the specific heat of the cooling
water. As shown in FIG. 3, at the predetermined temperature D, the
specific heat of the cooling water becomes higher than that at
other temperatures. For this reason, as shown in FIG. 2, in the
period of time from A to B, the outlet side temperature of the
cooling water becomes constant at the predetermined temperature D.
In addition, FIG. 2 shows the case where the temperature E at which
the thermostat 15 opens is higher than the predetermined
temperature D.
[0045] In this manner, if the thermostat 15 is set to open at the
time when the outlet side temperature of the cooling water is
higher than the predetermined temperature D, it will be possible to
utilize the characteristic that the specific heat of the cooling
water becomes higher, i.e., the characteristic of the cooling water
temperature becoming constant. That is, when the cooling water
temperature goes up, the rise of the temperature can be suppressed
by taking heat, whereas when the cooling water temperature goes
down, the fall of the temperature can be suppressed by giving heat.
For this reason, the variation of the cooling water temperature can
be suppressed, thus making it possible to stabilize the operating
state of the internal combustion engine 1.
[0046] Here, note that the temperature E at which the thermostat 15
is opened may also be set, for example, as a temperature at which
the warming up of the internal combustion engine 1 is completed,
but is not limited to this. In addition, the components included in
the cooling water may be decided in such a manner that the
predetermined temperature D becomes lower than the temperature at
which the warming up of the internal combustion engine 1 is
completed. An optimum value of the temperature E at which the
thermostat 15 is opened and an optimum value of the predetermined
temperature D can be obtained through experiments, etc.
[0047] In addition, in the above-mentioned explanation, the
thermostat 15 is controlled by the ECU 30, but a thermostat which
is automatically opened and closed at a prescribed temperature can
also be used.
[0048] Moreover, the time at which the thermostat 15 is opened can
also be set, in further consideration of the inlet side
temperature, i.e., the temperature of the cooling water which flows
through the second cooling water passage 12. That is, in an
operating state in which a high cooling capacity is required, the
thermostat 15 is set to open at the time when the inlet side
temperature of the cooling water is lower than the predetermined
temperature D. On the other hand, in an operating state in which
the cooling capacity may be low, the thermostat 15 is set to open
at the time when the inlet side temperature of the cooling water is
higher than the predetermined temperature D.
[0049] Here, note that the operating state in which a high cooling
capacity is required is, for example, in a state where at least one
of the number of engine revolutions per minute and the engine load
is relatively high. This may also be a time in which the internal
combustion engine is at high rotation speed and under high load or
in an accelerating operation. On the other hand, the operating
state in which the cooling capacity may be low is, for example, in
a state where the number of engine revolutions per minute and the
engine load are relatively low. This may also be a time in which
the internal combustion engine is at low rotation speed and under
low load or in a steady state operation.
[0050] FIG. 4 is a view showing the relation among the number of
engine revolutions per minute, the engine load, and the temperature
at which the thermostat 15 opens. In FIG. 4, F indicates an
operation region in which a high cooling capacity is required (a
region in which at least one of the number of engine revolutions
per minute and the engine load is relatively high), and G indicates
an operation region in which the cooling capacity may be low (a
region in which the number of engine revolutions per unit time and
the engine load are relatively low).
[0051] In the operation region F in which a high cooling capacity
is required, the thermostat 15 is opened so that the following
relation is satisfied.
[0052] The inlet side temperature<the predetermined temperature
D<the outlet side temperature
[0053] That is, the predetermined temperature D becomes higher than
the inlet side temperature, and the outlet side temperature becomes
higher than the predetermined temperature D. For this reason, the
cooling water becomes the predetermined temperature D when it flows
through the water jacket 2. Accordingly, the specific heat of the
cooling water becomes high in the interior of the internal
combustion engine 1, so the temperature rise of the cooling water
in the interior of the internal combustion engine 1 can be
suppressed. As a result of this, the operating state of the
internal combustion engine 1 can be stabilized.
[0054] On the other hand, in the operation region G in which the
cooling capacity may be low, the thermostat 15 is opened so that
the following relation is satisfied.
[0055] The predetermined temperature D<the inlet side
temperature<the outlet side temperature
[0056] That is, the inlet side temperature becomes higher than the
predetermined temperature D. As a result of this, the cooling water
temperature is maintained in a high state, thus making it possible
to improve fuel economy.
[0057] Here, note that a boundary between the region indicated by F
in FIG. 4 and the region indicated by G changes, for example,
according to whether priority is given to the stability of the
operating state of the internal combustion engine 1, or the
improvement in fuel economy, and hence, an optimum value is
obtained through experiments, etc.
EXPLANATION OF REFERENCE NUMERALS AND CHARACTERS
[0058] 1 internal combustion engine [0059] 2 water jacket [0060] 3
water pump [0061] 11 first cooling water passage [0062] 12 second
cooling water passage [0063] 13 radiator [0064] 14 bypass passage
[0065] 15 thermostat [0066] 30 ECU [0067] 31 outlet side
temperature sensor [0068] 32 inlet side temperature sensor [0069]
33 accelerator opening sensor [0070] 34 crank position sensor
* * * * *