Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
1998-11-18
2001-04-10
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
C123S041120
Reexamination Certificate
active
06213060
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic control cooling system for controlling temperature of a coolant of an automotive engine for prevention of the global warming.
2. Description of the Related Art
Referring to
FIG. 6
showing a conventional cooling system for an automotive engine, the system has a thermostat
1
which is disposed in an inlet side passage of water jackets
20
.
The cooling system comprises a first coolant passage
24
disposed between an upper outlet
21
of the water jackets
20
and an upper inlet
23
of a radiator
22
, and a second coolant passage
30
provided between a lower outlet
25
of the radiator
22
and a lower inlet
29
of the water jackets
20
, including a thermostat cap
26
, a thermostat housing
27
and a water pump
28
. A bypass passage
31
is provided between a junction J of the first passage
24
and the thermostat housing
27
so as to communicate the first passage
24
with the second passage
30
without passing the radiator
22
. The thermostat
1
is hermetically secured to the housing
27
by the thermostat cap
26
. The thermostat
1
has a main valve
12
for closing the second passage
30
and a bypass valve
15
for closing a bypass port
32
of the bypass passage
31
.
In
FIG. 6
, the reference A′ designates a measuring point for measuring the temperature of the coolant in the housing
27
, and the reference B′ designates a measuring point provided in the second passage
30
adjacent to the thermostat cap
26
. The reference C designates a measuring point for measuring the flow rate of the coolant in the second passage
30
. The reference numeral
33
designates a cooling fan.
The thermostat
1
is operated by a thermo-actuator. The thermo-actuator comprises an actuating steel rod and a resilient seal spool which is slidably engaged with the rod. The seal spool is inserted in a heat sensitive cylinder filled with wax pellets.
As shown in
FIG. 7
, a perforation
19
is formed in a flange
16
of the thermostat
1
, and a jiggle valve mechanism
17
having a jiggle valve
18
is movably engaged in the perforation
19
.
During the operation of the engine, the jiggle valve
18
is closed by the pressure of the coolant in the second coolant passage
30
as shown in FIG.
7
. When the engine stops, the jiggle valve opens. Thus, the coolant can be supplemented in the direction of the arrow.
During the cold engine state, the main valve
12
of the thermostat
1
is closed as shown in
FIG. 6
, and the jiggle valve
18
is also closed by the coolant pressure, while the bypass valve
15
integrated with the main valve
12
is fully opened. Thus, the coolant drawn from the outlet
21
of the water jackets
20
does not pass through the radiator
22
. The coolant is circulated by the water pump
28
through the junction J of the first passage
24
, bypass passage
31
, housing
27
, and inlet
29
of the water jackets
20
as indicated by arrows. Thus, the temperature of the coolant in the housing
27
quickly rises.
However, since the coolant in the radiator
22
and the thermostat cap
26
is not circulated, the temperature rising rate of the coolant temperature B therein is slow. Therefore, as shown in a record of
FIG. 8
, after even if the temperature A at the point A′ becomes 87° C. which is an opening temperature of the main valve
12
, the temperature B at the point B′ is merely 45° C. There is a difference of 42° C. between the temperatures A and B.
When the main valve
12
of the thermostat
1
opens, the coolant of a low temperature is drawn from the lower outlet
25
of the radiator
22
and fed to the thermostat housing
27
through the second passage
30
. Consequently, the temperature B of the coolant at the point B′ is further lowered by 13° C. As a result, the difference between the temperature B of the coolant in the passage
30
and the temperature A of the coolant in the housing
27
increases to 55° C. The area of the part shown by the hatching indicates energy loss in the period. It will be understood that the time of the abscissa indicates the elapse from the time at 60° C. of the temperature A.
Since the heat sensitivity of the thermostat
1
is low, the response of the thermostat delays with respect to the change of the coolant temperature. Therefore, the main valve
12
opens after the temperature has become considerably higher than the predetermined opening temperature 87° C. The main valve
12
closes after the coolant temperature has considerably decreased lower than a predetermined closing temperature. So that the main valve
12
is repeatedly opened and closed. When the main valve
12
closes, a surge pressure occurs at the upstream of the main valve
12
.
The heat overshoot causes cracks of the cylinder block and cylinder head of the engine, and the surge pressure causes breakdown of the thermostat
1
and the radiator
22
.
Since, mentioned in above, the jiggle valve mechanism is sources of energy loss and engine troubles, the jiggle valve mechanism is removed from the present thermostat. Further, a small hole
19
a
is formed in the flange
16
of the thermostat (FIG.
4
). The pressures applied to the outer side and inner side of the main valve
12
become equal to each other. The spring constant of the return spring is reduced in half. Furthermore, the thickness of the seal spool is extremely thin (thickness of between 25% and 5% of the diameter of the actuating rod), the pressure of the wax for the lift up of the valve is reduced.
FIG. 1
is a diagram showing the lift with respect to the coolant temperature. A line X is the lift of the valve of the present invention and the line Y is the lift of the conventional valve. The range of the steep curve line is the solid wax state.
The main valve of the conventional valve Y opens at 72° C., the lift at the end temperature 87° C. of the solid wax state is merely 9.6 mm. Thereafter, the lift up rate reduces because of the liquid wax state, and when the lift becomes 12 mm, the coolant temperature reaches such a high temperature as 123° C.
The main valve
12
of the present invention also opens at 72° C., when the lift reaches 12 mm, the coolant temperature is 85° C. as shown by the line X, which is within the range of the solid wax state.
The line Z—Z′ of
FIG. 1
shows the upper limit of 81° C. The hatched area shows the difference between the flow rate of the present invention and the flow rate in the conventional valve. The lift of the line X at 81° C. is 6 mm and the lift of the line Y is 3 mm. Therefore, the flow rate of X is two times as much as the flow rate of Y.
The coolant flowing through a small hole
19
a
(
FIG. 4
) on the flange
16
needs not worry about taking a longer warm up period for a idling. Because the cold start fuel injector is provided in the throttle body controlled by a computer.
In the cooling system, the fan switch of the present invention is linked to the thermostat, when the coolant temperature reaches 81° C., the cooling fan operates. Since the flow rate of the coolant at 81° C. is the double of that of the conventional thermostat, the coolant temperature quickly decrease. Therefore, the coolant temperature is kept 81° C.
However, the upper limit for the cooling fan is not limited to 81° C. It is desirable to set the temperature to an effective value as low as possible dependent on tests.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a cooling system having a wax type thermostat a main valve of which has double flow rate of the conventional thermostat.
In addition, a cooling fan switch linked to the thermostat through an electronic control system, resulting the prevention of global warming.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.
REFERENCES:
patent: 4313402 (1982-02-01), Lehnhoff et al.
patent: 4679530 (1987-07-01), Kuze
patent: 4955431 (1990-09-01), Saur et al.
p
Benton Jason
Koda & Androlia
McMahon Marguerite
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