Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
2000-08-22
2002-02-05
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
C123S041080
Reexamination Certificate
active
06343573
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermostat that controls coolant flow of an internal combustion engine, and more particularly to a thermostat and water pump in an integrated housing.
2. Description of the Prior Art
Although traditionally thermostats were mounted at the outlet of engines, recently they are being mounted on a coolant inlet side of the engine. The coolant flows through a water jacket (not shown) of the engine block
3
. For medium to large size engines, as shown in
FIGS. 1A and 1B
, a thermostat
7
is placed upstream and adjacent the inlet of a water pump ensuring a relatively larger flow of coolant into the bypass passage
6
when the thermostat
7
is closed. A cooling system
1
causes the flow to be directed through a radiator
2
when the engine
3
is warmed up.
U.S. Pat. No. 4,938,185 granted to Doke, incorporated herein by reference, discloses a one-piece structure that includes a coolant pump and a thermostat. As shown in
FIG. 2
, this conventional engine cooling arrangement
10
includes a water pump
12
whose impeller
12
a
is rotatably housed in an impeller chamber
14
. The impeller chamber
14
is formed in an impeller chamber section
16
A integral with and forming part of a timing (front) cover
16
. The water pump impeller
12
a
is driven through a pulley and belt drive. The timing cover
16
is mounted to the front face F of the cylinder block B, and covers a rotation transmission mechanism (not shown). In an inlet passageway section
16
B of the timing cover
16
, a coolant inlet passageway
18
leads to the inlet
14
a
of the impeller chamber. A thermostat
20
thermally controls the flow of the cooling water from the radiator to the water jacket of the cylinder block. The thermostat
20
has a heat sensor section
20
a
disposed in the inlet passageway
18
. A coolant passageway
22
allows coolant from the radiator to flow to the inlet passageway
18
when a valve section
20
b
of the thermostat
20
opens. Another coolant passageway
24
from a heater and a bypass passageway
26
from the water jacket of the cylinder block are each directly connected to the inlet passageway
18
. A coolant outlet passageway
28
connects an outlet
14
b
of the pump impeller to the cylinder block B, passageway
28
being part of outlet section
16
C of the timing cover
16
.
The operation of the conventional cooling arrangement will now be described. Coolant from the radiator is suppliable through the thermostat valve section
20
b
into the inlet passageway
18
and thereafter sucked into the pump impeller chamber
14
. The coolant discharged from the water pump
12
is recirculated through the outlet passageway
28
to the water jacket of the cylinder block B. Coolant discharged from the water jacket is fed to the radiator and the heater. When the engine is cold, coolant discharged from the water jacket is recirculated to the inlet passageway
18
bypassing the radiator in order to assist warm-up of the engine. The inlet passageway
18
is formed straight to enable the engine cooling arrangement to be easily produced by die-casting.
FIG. 3
illustrates a conventional thermostat, where a frame
37
having a flange
32
secures the components of a thermostat
30
, so that a main valve
33
is held by a spring
35
and a bypass valve
39
is held by a spring
38
. A wax element
36
is secured to the frame
37
by a stop ring
34
. The wax element
36
drives a piston
31
with a lift amount of the piston
31
being proportional to the temperature sensed by the wax element
36
.
The conventional cooling arrangement does not respond quickly to the change in temperature of the coolant as the engine warms up and does not mix bypass flow (hot coolant) with cold coolant from the radiator. Hysteresis and overshoot result from the coolant temperature changing when flowing through the cylinder block after the valve action of the thermostat, and a lack of stability results.
U.S. Pat. No. 5,503,118 granted to Hollis discloses a temperature control system having a water pump in a housing with flow restrictor valves. The electronically controlled restrictor valves are kept closed to retain the coolant in the cylinder head, and are then activated when the engine has sufficiently warmed-up in order to permit coolant flow into the engine block. The valves are controlled by a computer so as to maintain the sensed oil temperature at an optimum value.
U.S. Pat. No. 5,715,776 granted to Seidl discloses a cooling system having a water pump, and a thermostat for selecting the coolant flow to either a radiator or the water pump. The flow path of the circulating coolant forms a particular pattern through the cylinder block that depends upon the temperature being either below or above the thermostat's predetermined opening point.
U.S. Pat. No. 5,113,807 granted to Kobayashi discloses a thermostat and cooling pump assembly arranged at a side position of an engine for communicating a heat exchanger with the engine cooling jacket. The thermostat is positioned between ends of the engine and adjacent the heat exchanger.
U.S. Pat. No. 5,216,984 granted to Shimano et al. discloses a thermostat housing provided integrally in an end portion of one of the cylinder heads that is bounded by the water pump. The water pump has a sprocket that is driven by the timing chain.
U.S. Pat. No. 4,662,320 granted to Moriya discloses a water pump directly coupled to the engine's cam shaft.
U.S. Pat. No. 5,992,755 granted to Kuse discloses a thermostat that has a pressure equalizing hole in its flange, and increases the lift-up rate at low temperature by reducing a return spring constant and reducing a seal spool thickness. Also, a higher lift increasing rate results in an increase in coolant flow rate and a lowering of upper limit coolant temperature. The thermostat seeks to decrease the upper limit temperature of the coolant.
U.S. Pat. No. 5,970,927 granted to Suzuki discloses an apparatus for circulating cooling water to an engine body, a radiator, a heater core, and an oil cooler. A connecting point, between the oil cooler cooling water communicating passageway and the heater core cooling water passageway, is located upstream of a thermostat-type flow control valve. A second thermostat-type flow control valve is located adjacent a radiator and operates at a significantly lower temperature. The configuration and action of the various flow control valves allows the heater core to remain unaffected by the flow of cooling water through the oil cooler.
The conventional cooling arrangements do not respond quickly to the change in temperature of the coolant as the engine warms up and do not mix bypass flow (hot coolant) with cold coolant from the radiator. The conventional activation of thermostats only indirectly controls coolant valves after the coolant has passed through separate passageways and through an engine. A disparity between the hot and cold coolant temperatures causes abrupt reaction to sudden temperature differentials that can result. Hysteresis and overshoot result from the coolant temperature changing when flowing through the cylinder block after the valve action of the thermostat, and a lack of stability results.
SUMMARY OF THE INVENTION
The present invention provides a thermostat, system, and method for achieving an improved control of cooling in an internal combustion engine. Mounting the thermostat at the inlet side of an internal combustion engine ensures a relatively larger flow of coolant into the bypass and enables reduction of the range of coolant temperature distributions in the water jacket when the thermostat valve is closed.
A significant advantage is obtained by stabilizing coolant temperatures. It is an object of the present invention to provide a minimum of overshoot and hunting by a thermostat that acts to stabilize the coolant temperature by opening and closing. Another object of the invention is an improved temperature control of an air conditioning system. A further object of the invention is a redu
Huynh Hai
Nippon Thermostat Co., Ltd.
Yuen Henry C.
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