Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
1998-06-24
2001-05-01
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
C123S041020
Reexamination Certificate
active
06223700
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cooling control system and a cooling control method for cooling an engine of, for example, a vehicle, more particularly, to a cooling control system and method capable of enhancing the responsibility of a temperature control with respect to cooling medium circulated in the engine and improving the control precision.
2. Description of the Related Art
In an engine used in a vehicle or the like, a water cooling type cooling device using a radiator is generally used for cooling the engine.
In this type of the cooling device, a thermostat is used in order to control temperature of the cooling water. When the temperature of the cooling water is lower than a predetermined temperature, the cooling water is circulated in a bypass passage so as not to flow into the radiator with the action of the thermostat.
FIG. 29
shows the above structure, in which numeral
1
is an engine composed of a cylinder block
1
a
and a cylinder head
1
b
, and a fluid conduit illustrated with arrow c is formed in the cylinder block
1
a
and the cylinder head
1
b
of the engine
1
.
Numeral
2
is a heat exchanger, namely a radiator. A fluid conduit
2
c
is formed in the radiator
2
as well-known, and a cooling-water inlet portion
2
a
and a cooling-water outlet portion
2
b
of the radiator
2
are connected to a cooling-water conduit
3
circulating the cooling water between the engine
1
and the radiator
2
.
The cooling-water conduit
3
is composed of an outflow-side cooling-water conduit
3
a
linking from an outflow portion id of the cooling water, placed in the upper portion of the engine, to the inflow portion
2
a
of the cooling water placed in the upper portion of the radiator
2
; an inflow-side cooling-water conduit
3
b
linking from the outflow portion
2
b
of the cooling water, placed in the lower portion of the radiator
2
, to an inflow portion
1
e
of the cooling water placed in the lower portion of the engine
1
; and a bypass conduit
3
c
connecting the conduits
3
a
and
3
b
to each other.
In a branch portion between the outflow-side cooling-water conduit
3
a
and the bypass conduit
3
c
in the cooling-water conduit
3
, a thermostat
4
is disposed. The thermostat
4
is provided therein with a thermal expansive body (e.g. wax) expanding and shrinking with changing of temperature of the cooling water. When the cooling-water temperature is high (e.g. over 80° C.), the valve is opened by the expansion of the thermal expansive body so that the cooling water flowing from the outflow portion
1
d
of the engine
1
flows through the outflow-side cooling-water conduit
3
a
into the radiator
2
. The cooling water cooled in the radiator
2
and dissipating heat is operated to flow from the outflow portion
2
b
through the inflow-side cooling-water conduit
3
b
, and through the inflow portion
1
e
of the engine
1
into the engine
1
.
When the temperature of the cooling water is low, the valve of the thermostat
4
is closed by the shrinkage of the thermal expansive body, so that the cooling water flowing from the outflow portion
1
d
of the engine
1
flows through the bypass conduit
3
c
, and through the inflow portion
1
e
of the engine into cooling pipes c of the engine
1
.
In
FIG. 29
, numeral
5
is a water pump disposed in the inflow portion
1
e
of the engine
1
, of which the rotating shaft is rotated by the rotation of a crank-shaft (not shown) of the engine
1
, so that the cooling water is forcibly circulated. Numeral
6
is a fan unit for forcibly blowing cooled air into the radiator
2
, and composed of a cooling fan
6
a
and a fan motor
6
b
rotationally driving the cooling fan
6
a.
The valve opening and the valve closing actions by the thermostat are determined by the temperature of the cooling water, and also by the expansion and shrinkage of the thermal expansive body such as wax, therefore the temperature in the valve opening and the temperature in the valve closing are not constant. The thermal expansive body such as wax takes some time to operate the valve after receiving the changing of the temperature of the cooling water until. Especially, the responsibility during the decrease of the temperature is inferior as compared with that during the increase of the temperature, that is to say it has hysteresis properties. As a result, there is a technical disadvantage in which the cooling water is not easily adjusted to be in a constant temperature required.
It is proposed that the flow of the cooling water is electrically controlled not to harness the actions of opening and closing valve by the thermal expansive body such as wax.
This is, for example, the control of a rotational angle of a butterfly valve using a stepping motor. Omitting the thermostat
4
shown in
FIG. 29
, a valve unit
7
provided with the butterfly valve instead of the thermostat
4
is disposed in the outflow-side cooling-water conduit
3
a
as illustrated with a long dashed line in FIG.
29
.
FIG. 30
shows an example of the above valve unit
7
, in which a circular plane shaped butterfly valve
7
a
is supported in the cooling-water conduit
3
a
to be rotated by a shaft
7
b
. A worm wheel
7
c
is attached on an end of the shaft
7
b
, and a worm
7
e
inserted in a rotational drive shaft of a motor
7
d
is engaged with the worm wheel
7
c.
The motor
7
is supplied with the operation current for rotating the drive shaft thereof in the forward and reverse directions by a control unit (ECU) controlling the operation condition of the overall engine. Therefore, when the current for rotating the drive shaft in the forward direction is passed into the motor
7
d
by the action of the ECU, the shaft
7
b
of the butterfly valve
7
a
is rotated in one direction by a well-known decelerating action produced by the worm
7
e
and the worm wheel
7
c
, whereby the plane direction of the butterfly valve
7
a
is rotated in the same direction as the flowing direction of the cooling-water conduit
3
a
, resulting in the valve opening state.
On the other hand, when the current for rotating the drive shaft in the reverse direction is passed into the motor
7
d
by the action of ECU, the shaft
7
b
of the butterfly valve
7
a
is rotated in the other direction, whereby the plane direction of the butterfly valve
7
a
is rotated in a direction perpendicular to the flowing direction of the cooling-water conduit
3
a
, resulting in the valve closing state.
The ECU receives information such as the temperature of the cooling water in the engine, and controls the temperature of the cooling water by controlling the aforementioned motor with the use of the above information.
In addition, in response to a control signal from the control unit (ECU) fetching various operational parameters which are detected from the engine, a stepping motor (not shown) rotating the butterfly valve is driven so as to control the flow of the cooling water flowing toward the radiator.
In the cooling control system using the butterfly valve as described thus far, a temperature detecting element such as a thermistor (not shown) is disposed in a part of the pipes for the cooling water in the engine
1
, and the motor
7
d
is driven responsive to the temperature of the cooling water detected by the temperature detecting element.
According to the structure as described above, the effects of the hysteresis properties seen in the former example using the thermostat including the thermal expansive body is decreased somewhat.
After the temperature detecting element senses the changing of the temperature of the cooling water, however, the ECU controls an angle of the valve on the basis of the sensed changing, that is to say it is a follow-up control. In consequence, in this point both examples are the same.
Even the cooling control system using the butterfly valve in the latter example cannot escape having a hunting phenomenon which is the temperature of the cooling water is changed around a specific temperature Tc at all times, resulting in
Morozumi Hiroshi
Sano Mitsuhiro
Benton Jason
Kamen Noah P.
Nippon Thermostat Co., Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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