Patent Application
20080223316
This invention relates to internal combustion engines, including but not limited to control of an engine cooling system flow with a thermostat device.
Internal combustion engines have cooling systems associated therewith that transfer heat away from the engine structure. These cooling systems typically include thermally actuated devices, or thermostats, that can route a cooling fluid flow either into the engine or into a radiator depending on a temperature of the cooling flow.
Typical engine thermostats are 3-way valves having one inlet and two outlets. A first port thereof acts as an inlet for the cooling fluid flow. A second port thereof acting as a first outlet, when open, directs the cooling fluid flow directly into the engine when the cooling flow is at a low temperature. A third port thereof acting as a second outlet, when open, allows the cooling fluid flow to bypass the engine and pass through a radiator, where it is cooled, before returning to the engine. A thermal actuator controls the opening of valves that control the cooling fluid flow into the first and/or second outlet. The thermal actuator, typically a material pushing onto a rod when heated and expanding, is immersed in the incoming cooling fluid flow at the inlet of the thermostat.
When an engine operates at high engine speed conditions, a cooling fluid flow rate is increased. This increased flow rate often creates instabilities during transitions periods in a thermostat position. These instabilities are often the result of hydrofoil effects onto plates of the thermostat that are used to fluidly block the second and third ports. These instabilities often cause the plates to vibrate or “slam” against their valve seats, thus causing damage thereto.
A thermostat assembly includes an actuator portion having a sealed container with an arm protruding therefrom. A retainer plate connects the thermostat assembly to an engine component. A bypass valve plate is arranged to sealably engage a bypass valve seat that is formed in the first engine component. The bypass valve plate includes a body portion having a central opening and an outer periphery, an inner rim surrounding the central opening, an outer rim surrounding the outer periphery, and a plurality of openings formed in the body portion. The plurality of openings are disposed adjacent to an interface between the body portion and the outer rim, such that a bypass pressure-dampening fluid passage is defined through the plurality of openings in the bypass valve plate.
The following describes an apparatus for and method of reducing an effect of instability in cooling fluid flow through a thermostat, especially during a transitional phase of operation, by providing an improved bypass fluid flow passage that has pressure dampening characteristics.
A section view of a known thermostat 100 as installed in an internal combustion engine between a first component 102 and a second component 104 thereof is shown in
A first spring 122 is disposed between the thermostat plate 115 and the retainer 118. The first spring 122 pushes the thermostat plate 144 away from the retainer 118. In a cold condition, the force of the first spring 122 acts to maintain a seated position of the retainer 118 in the groove 120, and to also push the thermostat plate 115 against an outlet seat 124 that is formed in the second component 104.
A bypass valve retainer 126 is connected to the actuator assembly 106 on a side thereof that is opposite the arm 108. The bypass valve retainer 126 has a bypass valve plate 128 connected to a distal end thereof. A second spring 130 is disposed between the bypass valve retainer 126 and the bypass valve plate 128, acting to push the bypass valve plate 128 away from the actuator assembly 106. In the embodiment shown, a groove 132 is formed in the first engine component 102 opposite the bypass valve plate 128. The groove 132 forms a bypass valve seat 134 that contacts the bypass valve plate 128 under certain conditions, generally, warm conditions.
During operation, a flow of coolant enters the thermostat 100. The flow of coolant, or more specifically a coolant supply from the engine, enters the thermostat 100 through an inlet opening 136. At times when the coolant flow has a lower temperature, or below about 190 degrees F. (88 degrees C.), the wax pill 114 in the actuator assembly is mostly solid, the arm 108 rests against a support 138 that is formed in the second component 104, and the bypass valve plate 128 is suspended away from the bypass valve seat 134. Thus, the coolant flow entering through the inlet opening 136 passes over the bypass valve plate 128 and exits the thermostat 100 through a bypass passage, or, a coolant return passage 140 that is formed in the first component 102 and that routs the coolant flow directly back into the engine.
When the coolant flow entering through the inlet opening 136 is warm, or has a temperature above about 190 degrees F. (88 degrees C.), the wax pill 114 melts and thermally expands within the container 112. The expansion of the wax pill 114 causes the arm 108 to extend away from the container 112, pushing against the support 138. The extension of the arm 108 causes the thermostat plate 115 to move away from the outlet seat 124, the first spring 122 to compress, and the bypass valve plate 128 to move toward the bypass valve seat 134. Continuous operation under warm conditions will eventually seat the bypass valve plate 128 onto the bypass valve seat 134. In this condition, the flow of coolant entering the inlet opening 136 will pass into an actuator chamber 142 of the thermostat 100, and exit the thermostat through a radiator outlet opening 144. The flow of coolant passing into the radiator outlet opening 144 will return to the engine after passing through a radiator (not shown).
One embodiment for an improved thermostat 200 is shown in partial cross section in
During operation of the thermostat 200, and especially during a transition period of warming coolant flow, the bypass valve plate 228 is pushed toward the bypass valve seat 134, as described. In the thermostat 100 of
An outline view from two different perspectives of the improved bypass valve plate 228 is shown in
During operation of the thermostat 200, a pressure dampening passage is created between the inlet opening 136, through the plurality of openings 230, through an area between the bypass valve plate 228 and the bypass valve seat 134, and out the coolant return passage 140. This pressure dampening passage is advantageously most effective at dampening pressure pulsations that would otherwise cause vibrations to the bypass valve plate at times when the bypass valve plate 228 is transitioning to a closed position and is close to and nearly seated on the bypass valve seat 134.
An alternate embodiment for a thermostat 600 having a bypass pressure-dampening fluid passage is shown in cross section in
During operation of the thermostat 600, and especially during a transition period of warming coolant flow, the bypass valve plate 628 is pushed toward the bypass valve seat 634, as described. The vibration described above for the thermostat 100 in
In this embodiment, a pressure dampening passage is created between the inlet opening 136, through a passageway 636 that exists between the bypass valve plate 628 and the bypass valve seat 634, and out the coolant return passage 140. At times when the bypass valve plate 628 is near and approaching the bypass valve seat 634, a uniform flow area exists around the entire periphery of the bypass valve plate 628 in the passageway 636. The uniform flow area in the passageway 636 acts to promote efficient flow of coolant there through, and is advantageously most effective at dampening pressure pulsations that would otherwise cause vibrations to the bypass valve plate at times when the bypass valve plate 628 is transitioning to a closed position and is close to and nearly seated on the bypass valve seat 634.
An alternate embodiment for a thermostat 800 having a bypass pressure-dampening fluid passage is shown in cross section in
The bypass valve plate 828 has an improved lateral surface 830. The lateral surface 830 has a mostly convex conical profile, and is arranged to linearly contact the improved bypass valve seat 834 that is formed in a first engine component 832 around an opening of the coolant return passage 140. The bypass valve seat 834 is formed as a sharp transition, at about 90 degrees, and has little to no lateral surfacing that contacts the lateral surface 830 in a flat manner. The bypass valve seat 834 can be described as a “sharp” edge surrounding the opening for the passage 140 that contacts the lateral surface 830 along a line.
During operation of the thermostat 800, and especially during a transition period of warming coolant flow, the bypass valve plate 828 is pushed toward the bypass valve seat 834, as described. The vibration described above for the thermostat 100 in
In this embodiment, a pressure dampening passage is created between the inlet opening 136, through a passageway 836 that exists between the bypass valve plate 828 and the bypass valve seat 834, and out the coolant return passage 140. At times when the bypass valve plate 828 is near and approaching the bypass valve seat 834, a high-turbulence flow area exists around the entire periphery of the bypass valve plate 828 in the passageway 836. The flow area for fluid passing through the passageway 836 acts to destroy any pressure differentials that exist across the bypass valve plate 828 by disrupting any pressure waves with turbulence created by an edge-flow condition near the sharp transition of the seat or edge 834. This configuration is advantageously most effective at dampening pressure pulsations that would otherwise cause vibrations to the bypass valve plate at times when the bypass valve plate 828 is transitioning to a closed position and is close to and nearly seated on the bypass valve seat 834.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
