WO1997011262A1

WO1997011262A1 - Thermostat having a movable weir valve

Info

Publication number: WO1997011262A1
Application number: PCT/US1996/014802
Authority: WO
Inventors: Edward R. Beaudry; Eric B. Thorstensen
Original assignee: Standard-Thomson Corporation
Priority date: 1995-09-19
Filing date: 1996-09-16
Publication date: 1997-03-27

Abstract

A thermostat apparatus (10) includes a stationary valve member (20) configured to be positioned in a conduit (16) of an engine cooling system. The stationary valve member (20) includes a valve seat (50) extending in a direction generally parallel to a longitudinal axis (60) of the thermostat (10). The apparatus (10) also includes a movable valve member (34) for engaging the valve seat (50) to block the flow of fluid past the stationary valve member (20). The movable valve member (34) includes an annular, cylindrically shaped body portion (44) having an outer side wall (58), a top surface (62), and an inner side wall (68). The outer side wall (58) of the body portion (44) extends in a direction generally parallel to the longitudinal axis (60) and is configured to engage the valve seat (50) of the stationary valve member (20) to block fluid flow past the stationary valve member (20). The movable valve member (34) is formed to include at least one three-dimensional weir (52, 70, 76, 78, 82, or 86) configured to permit fluid flow through the at least one weir (52, 70, 76, 78, 82, or 86) as the movable valve member (34) moves away from the valve seat (50).

Description

THERMOSTAT HAVING A MOVABLE WEIR VΑLVE

Background and Summary of the Invention

The present invention relates to a thermostatic control valve for controlling fluid flow through a cooling system of an engine. More particularly, the present invention relates to a thermostat which provides improved fluid flow patterns through the engine cooling system to optimize performance of the cooling system. Several problems faced by a modern automotive manufacturers stem from the need for more efficient cooling systems which have lower amounts of coolant fluid in the system at any given time. The engine cooling systems must also provide quicker engine warm-up for emissions concerns and provide better thermal stability.

A result of these cooling system demands on the modern automotive manufacturer has increased a thermal "cycling" problem of the engines which adversely affects the performance of the engine. Thermal cycling in an automotive coolant system is caused by the thermostat failing to control the flow of coolant fluid out of the engine and into the radiator in a sufficient manner.

The thermostats permit a sudden entry of coolant fluid when the fluid reaches a predetermined temperature. This sudden entry of coolant fluid causes excessive fluctuation in the coolant fluid temperature. This temperature fluctuation, known as cycling, is an unstable condition which contributes to engine inefficiencies and which can have an impact on driveability, engine durability, fuel economy, and emissions.

Thermal cycling allows excess cold or cool coolant fluid into the engine which then closes the thermostat. The engine then starts to warm again, and the radiator cools off. This starts the cycle all over again. These cycles can be repeated without abatement under certain conditions. Thermal cycling may cause thermal shock, rich running, increased emissions, and reduced fuel economy. In addition, the thermal cycling can affect customer satisfaction with heater performance. The phenomenon of thermal cycling is most prevalent in an engine system which is "outlet" controlled. An outlet controlled coolant system is one in which a thermostat is located at an outlet of the engine toward the radiator. This position of the thermostat tends to aggravate the cycling condition due to the presence of higher pressures within the engine block due to the thermostat blocking the discharge of the water pump. This increased pressure affects the thermal cycling condition as it permits additional flow when the thermostat does open. Some manufacturers have adopted an "inlet" thermostat where the thermostat is placed in the flow of coolant fluid into the engine. This results in a thermostat valve closing faster and, therefore, provides more stability to the overall engine temperature. The inlet thermostat position cannot be used in every case due to space and cost constraints.

The current trend for engine cooling systems is to provide faster warm-up times. This allows improved emissions and heater performance. The desire for fast warm-up times has caused valves and thermostats to minimize leakage past the thermostats. This also aggravates the thermal cycling condition as the radiator coolant stays at a very low temperature prior to the thermostat opening up. Modern cooling systems also have smaller fluid volume and higher fluid velocity. This allows more efficient coolant flow within the engine and less weight in the vehicle. However, this also aggravates the thermal cycling condition as less coolant must be released into the radiator to overcool. The thermostat of the present invention is designed to limit the amount of coolant fluid which flows through the cooling system of the engine during early warm- up stages. The present invention includes a stationary valve member and a movable valve member. The movable valve member is formed to include a plurality of weirs or cut¬ outs. These weirs have a three dimensional shape. The shape and size of the weirs can be adjusted to control fluid flow through the thermostat. As the movable valve is moved away from the valve seat of the stationary valve member due to expansion of wax in a power element of a thermally responsive actuator, the coolant fluid flows initially through the plurality of weirs formed in the movable valve member. By adjusting the shape and dimensions of the weirs formed in the movable valve member, the present invention permits significant changes to the early fluid flow characteristics of the thermostat to prevent overcooling. The configuration of the plurality of weirs in the movable valve provides flow characteristics which are approximately one-tenth that of traditional thermostats over the same operating range. The variety of weir geometries of the present invention permits the thermostat to be tailored or customized to fit the needs of the cooling system of a particular engine as discussed below. The movable valve, when closed, is sealed against a side wall adjacent the flange at the base of the stationary valve member. This eliminates or minimizes leakage when the movable valve member is closed. It is known to use weirs in thermostats to control early fluid flow. See, for example, U.S. Patent Nos. 4,053,105; 4,164,332; 4,286,750; and 5,410,991. These known weir designs do not provide the three-dimensional weirs having various geometrical configurations like the present invention. In addition, these known designs do not utilize the flange wall as a sealing surface for the movable valve member. In addition, these known weir designs do not provide the variability and shape, size, and location of the weirs within the thermostat valve. The present invention permits use of incremental and staggered shaped weirs as discussed below. This permits greater control of fluid flow to reduce the problem of cycling and to enhance a standard high volume thermostat. The novel weir design of the present invention permits the thermostat to be tailored or customized for a particular engine. The ability to provide a custom thermostat, as discussed below, is helpful due to different performance characteristics of engines and engine cooling systems. The shape and configuration of the weirs in the present invention permit the thermostat to be tailored for the demands of each engine, coolant, radiator, platform, and heater performance. Each engine has unique needs in order to avoid thermal cycling caused by overcooling. In order to provide a custom thermostat, empirical data is taken from a final assembly vehicle which is tested in a wind tunnel to simulate worst case, but controlled conditions. Data is collected related to the thermal cycling for a particular engine, thermostat, radiator, vehicle, etc. The data is analyzed for a number of significant factors. Some of these factors include coolant heat carrying capacity, coolant velocity, water pump fan speed, air temperature, fan speed, heat transfer coefficients, frictional losses, flow, time, radiator surface area, thermal shock surface areas, road speed, pressure constants, heater core output, fuel consumption, horse power generation, oil pressure, time at temperature, and engine speed.

These factors are evaluated using a least squares regression analysis over the various points of the test run to establish a series of equations related to the specific coolant system time, flow, temperature, and pressure relationships. A target thermostat performance is then developed. The design of the variable-shaped weirs is then considered along with varying thermal responses of the wax which drives the thermally responsive actuator. The potential design is then evaluated mathematically against the target design. By changing the geometry of the weir design and the wax curves, the thermostat of the present invention can be tailored for a specific engine need. The improved three-dimensional weir geometry permits increased control over initial flow of fluid to the radiator. According to one aspect of the present invention, a thermostat apparatus is provided for controlling fluid flow through an engine cooling system. The apparatus includes a stationary valve member configured to be positioned in a conduit of the cooling system. The stationary valve member includes a valve seat. The apparatus also includes a movable valve member for engaging the valve seat to block the flow of fluid past the stationary valve member. The movable valve member is formed to include at least one three dimensional weir configured to permit fluid flow through the at least one weir as the movable valve member moves away from the valve seat. The apparatus further includes a frame coupled to the stationary valve member, a spring extending between the frame and the movable valve member for biasing the movable valve member to a normally closed position against the valve seat, and a thermally responsive actuator coupled to the movable valve member for moving the movable valve member from the normally closed position to an open position spaced apart from the valve seat when the te perature of the fluid exceeds a predetermined temperature.

In the illustrated embodiment, the thermally responsive actuator of the thermostat includes a power element and a stem portion which is movable relative to the power element from a retracted position to an extended position when the temperature of the fluid exceeds the predetermined temperature. The stem portion is configured to engage the stationary valve member and the movable valve member being coupled to the power element.

In one illustrated embodiment, the movable valve member is formed to include a plurality of three- dimensional weirs. The plurality of three-dimensional weirs have at least two different geometric shapes. In the illustrated embodiment, the movable valve member includes an annular, cylindrically shaped body portion having an outer side wall, a top surface, and an inner side wall. The outer side wall of the body portion is configured to engage an annular inner side wall of the stationary valve member which defines the valve seat to block fluid flow past the stationary valve member.

In one weir configuration, the at least one three-dimensional weir is formed only in the outer side wall and the top surface of the body portion of the movable valve member. The at least one weir is aligned at an acute angle relative to the top surface of the body portion so that the weir slopes downwardly toward the outer side wall.

In another weir configuration, the at least one weir is an incremental weir including first and second weir sections formed at different angles. The incremental weir may be cut through the entire body portion of the movable valve member, if desired.

According to another aspect of the present invention, a method is provided for manufacturing a custom thermostat designed for a particular engine cooling system. The method includes the steps of evaluating factors related to performance of the engine cooling system, and providing a thermostat having a stationary valve member configured to be positioned in a conduit of the cooling system. The stationary valve member has a valve seat defining an opening to a radiator. The method also includes the step of providing a movable valve member for engaging the valve seat to block the flow of fluid through the stationary valve member to the radiator. The movable valve member is formed to include a plurality of three-dimensional weirs configured to permit fluid flow through the plurality of weirs as the movable valve member moves away from the valve seat to control initial fluid flow to the radiator. The method further includes the step of providing a thermally responsive actuator for opening and closing the movable valve member. The thermally responsive actuator includes a power element having a wax material located therein for moving a stem from a retracted position to an extended position to open the movable valve when the temperature of the fluid exceeds a predetermined level. The method still further includes the step of adjusting the geometrical configuration of the plurality of weirs formed in the movable valve member to optimize a fluid flow parameter based on the factors related to the engine cooling system determined during the evaluating step.

The illustrated method further includes the step of adjusting a thermal expansion property of the wax material in the power element based on the factors related to the engine cooling system determined during the evaluating step. Therefore, this method provides a custom thermostat for the particular engine cooling system.

Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.

Brief Description of the Drawings The detailed description particularly refers to the accompanying figures in which:

Fig. 1 is a sectional view illustrating a thermostatic control valve of the present invention mounted in an engine cooling system for controlling fluid flow to a radiator with a movable valve member in a closed position engaging a stationary valve member;

Fig. 2 is a sectional view similar to Fig. 1 illustrating partial fluid flow through a plurality of weirs formed in the movable valve member as the movable valve member begins to move away from the stationary valve member;

Fig. 3 is a sectional view similar to Figs. 1 and 2 illustrating the movable valve member in a fully open position; Fig. 4 is an elevational view illustrating additional details of the movable valve member including a plurality of three dimensional weirs;

Fig. 5 is a top plan view of the movable valve of Fig. 4; Fig. 6 is a partial perspective view of a typical weir design as illustrated in Figs. 1-5;

Fig. 7 is a partial perspective view illustrating another weir design of the present invention which is cut completely through a cylindrical body portion of the movable valve member;

Fig. 8 is a partial perspective view of a staggered weir design in which adjacent weirs formed in the body portion of the movable valve member have different three-dimensional geometric shapes; Fig. 9 is a partial perspective view illustrating a cut-through staggered weir design in which adjacent cut- through weirs similar to Fig. 7 have different geometric shapes; Fig. 10 is a partial perspective view illustrating an incremental weir configuration; and

Fig. 11 is a partial perspective view illustrating an incremental cut-through weir configuration.

Detailed Description of the Drawings

Referring now to the drawings, Fig. 1 illustrates a thermostat 10 of the present invention for controlling fluid flow through a coolant system of an engine. Fig. 1 diagrammatically illustrates an engine block 12 formed to include a first conduit 14 for receiving fluid flow from the engine and a second conduit 16 for conducting coolant fluid flow to a radiator in the direction of arrow 18 when the thermostat 10 opens as illustrated in Figs. 2 and 3. Thermostat 10 includes a stationary valve member 20 having an annular flange 22 and a bridge 24. Flange 22 is trapped between an engine block 26 and a cover 28 and sealed with a gasket 30. Bridge 24 is formed to include apertures 32 to permit coolant flow through the bridge 24.

Thermostat 10 also includes a movable valve member 34 coupled to a thermally responsive actuator 36. Actuator 36 includes a power element 38 having expandable wax therein and a stem 40 movable from a retracted position illustrated in Fig. 1 to an extended position illustrated in Fig. 3 as the wax inside the power element 38 expands due to temperature increases of the cooling fluid. Movable valve 34 includes annular support member 42 coupled to power element 38 and an annular, cylindrically shaped body portion 44 extending upwardly from support member 42.

A frame 46 is coupled to stationary valve member 20. Frame 46 holds an operating spring between frame 46 and movable valve member 34. Operating spring 48 biases the movable valve member in the direction of arrow 18 to a normally closed position illustrated in Fig. 1. In this normally closed position, the body portion 44 of movable valve member 34 engages an annular side wall 50 of the stationary valve member as best illustrated in Fig. 3 to block fluid flow to the radiator in the direction of arrow 18. Therefore, side wall 50 of stationary valve member 20 provides a valve seat which is engaged by body portion 44 of movable valve 34 to close the thermostat 10. The valve members 20 and 34 may be made of metal, plastic, or rubber coated metal.

Body portion 44 of movable valve member 34 is formed to include a plurality of three-dimensional weirs 52. Weirs 52 are cutout sections formed in body portion 44 which permit partial fluid flow through the movable valve member 34 as movable valve member 34 begins to open or move away from stationary valve member 20 as illustrated in Fig. 2. Fig. 2 illustrates partial fluid flow through the weirs 52 as illustrated by arrows 54. In the position of Fig. 2, fluid flow passes only through the weirs 52 formed in the movable valve 34. Sections of the body portion 44 which do not include weirs 52 still engage side wall 50 to block full fluid flow through the movable valve 34. Therefore, primary fluid flow is through weirs 52 until a top surface 62 of body portion 44 move past the valve seat defined by inner side wall 50. As discussed above, the weir configurations permit control of the initial fluid flow to the radiator to prevent overcooling. Fig. 3 illustrates the thermostat 10 after the stem 40 is fully extended from power element 38 to move the movable valve 34 to its fully open position. Therefore, the body portion 44 of movable valve member 34 does not contact the inner diameter of side wall 50 of the stationary valve member 20 in the Fig. 3 open position. This permits full fluid flow around an outer periphery of movable valve member 34 in the direction of arrows 56.

Further details of movable valve member 34 are illustrated in Figs. 4 and 5. Body portion 44 is a generally cylindrically shaped portion including an outer side wall 58 configured to engage the inner side wall 50 of stationary valve member 20. Both side wall 50 of the stationary valve member 20 and side wall 58 of movable valve member 34 extend in a direction which is generally parallel to a longitudinal axis 60 of the thermostat 10. Body portion 44 also includes a top surface 62.

Weirs 52 are sections which are cut from body portion 44. The weirs 52 are three-dimensional weirs as illustrated in Figs. 4 and 5. Weirs 52 have a first dimension illustrated by dimension X in Fig. 4 which is a width of the cutout. Weirs 52 also include a length dimension illustrated by dimension Y in Fig. 4. The length dimension Y is a distance of the cut out section extending downwardly from top surface 62 of body portion 44 of movable valve 34. The weirs 52 also include a depth dimension Z illustrated in Fig. 5. This dimension Z is a distance of the cutout into top εurface 62 extending from side wall 58.

In Figs. 4 and 5, six weirs 52 are formed in movable valve member 34. According to an aspect of this invention, the configuration including the size and shape of the weir design can be altered to customize fluid flow patterns through a particular thermostat 10. By changing the weir design and by altering the wax characteristics of the thermostat it is possible to create a custom thermostat for a particular engine and cooling system for a particular vehicle as discussed above.

Fig. 6 illustrates a standard weir design as illustrated in Fig. 1-5. In this embodiment, the weirs 52 include first and second cut sections 64 and 66 formed in body portion 44 of movable valve 34. In this embodiment, the weirs 52 do not extend to a rear wall 68 of body portion 44. Weirs 52 are formed at an acute angle relative to the top surface 62 of body portion 44 so that the weirs 52 slope downwardly toward outer side wall 58. Fig. 7 illustrates an alternate weir configuration in which a weir 70 is cut through the entire body portion 44. In other words, weir 70 extends from outer side wall 58 to inner side wall 68 of body portion 44 of movable valve 34. Weir 70 includes first and second angled cut sections 72 and 74.

Fig. 8 illustrates another weir configuration. This weir configuration is a staggered weir design. Weir 52 is the same as illustrated in Figs. 1-6. However, another weir geometric configuration is illustrated by 76. Weir 76 has increased dimensions to permit a larger amount of fluid flow as the movable valve 34 moves to its position illustrated in Fig. 2.

Fig. 9 illustrates a staggered cut through weir design. Fig. 9 includes a first cut through weir 70 such as illustrated in Fig. 7. In addition, the Fig. 9 embodiment includes a second, differently shaped cut through weir 78 located adjacent weir 70. Weir 78 has an increased depth to provide increased fluid flow through weir 78 as compared to weir 70.

Another weir design is illustrated in Fig. 10. Fig. 10 illustrates an incremental weir 80 having first and second weir sections 82 and 84 which are aligned at different angles to provide incremental flow through weir 80.

Fig. 11 illustrates an incremental cut-through weir 86 which is cut completely through body portion 44 from front outer side wall 58 to inner side wall 68. Again, incremental weir 86 includes first and second weir sections 88 and 90 which are aligned at different angles to , „_M

WO 97/11262

- 13 - provide incremental fluid flow through the weir 86 as the movable valve 34 moves away from stationary valve member 20.

It is understood that any combination of the three dimensional weirs illustrated in Figs. 6-11 may be used on the body portion 44 of movable valve member 34 to control initial fluid flow through the thermostat 10. It is also understood that the weirs may have other geometric shapes. For instance, the weirs may have a rectangular shape, an oval shape, or any other desired configuration. The specific geometry of the three dimensional weirs can be adjusted to customize the thermostat 10 for a particular engine, and vehicle cooling system based on desired fluid flow parameters. It is understood that the standard weirs can be used with the cut-through and incremental weirs on the same movable valve.

Although the invention has been described in detail with reference to a certain preferred embodiment, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.

Claims

CLAIMS :

1. A thermostat apparatus for controlling fluid flow through an engine cooling system, the apparatus comprising: a stationary valve member configured to be positioned in a conduit of the cooling system, the stationary valve member including a valve seat; a movable valve member for engaging the valve seat to block the flow of fluid past the stationary valve member, the movable valve member being formed to include at least one three dimensional weir configured to permit fluid flow through the at least one weir as the movable valve member moves away from the valve seat; a frame coupled to the stationary valve member; a spring extending between the frame and the movable valve member for biasing the movable valve member to a normally closed position against the valve seat; and a thermally responsive actuator coupled to the movable valve member for moving the movable valve member from the normally closed position to an open position spaced apart from the valve seat when the temperature of the fluid exceeds a predetermined temperature.

2. The apparatus of claim 1, wherein the thermally responsive actuator of the thermostat includes a power element and a stem portion which is movable relative to the power element from a retracted position to an extended position when the temperature of the fluid exceeds the predetermined temperature, the stem portion being configured to engage the stationary valve member and the movable valve member being coupled to the power element.

3. The apparatus of claim 1, wherein the movable valve member is formed to include a plurality of three-dimensional weirs, and wherein the plurality of three-dimensional weirs have at least two different geometric shapes.

4. The apparatus of claim 1, wherein the movable valve member includes a annular, cylindrically shaped body portion having an outer side wall, a top surface, and an inner side wall, the outer side wall of the body portion being configured to engage an annular inner side wall of the stationary valve member which defines the valve seat to block fluid flow past the stationary valve member.

5. The apparatus of claim 4, wherein the at least one three-dimensional weir is formed only in the outer side wall and the top surface of the body portion of the movable valve member.

6. The apparatus of claim 4, wherein the at least one weir is aligned at an acute angle relative to the top surface of the body portion, the weir sloping downwardly toward the outer side wall.

7. The apparatus of claim 1, wherein the at least one weir is an incremental weir including first and second weir sections formed at different angles.

8. The apparatus of claim 7, wherein the incremental weir is cut through the entire body portion of the movable valve member.

9. A thermostat apparatus for controlling fluid flow through an engine cooling system, the apparatus comprising: a stationary valve member configured to be positioned in a conduit of the cooling system, the stationary valve member having a flange and an annular inner side wall configured to define a valve seat, the annular inner side wall extending generally parallel to a longitudinal axis of the thermostat; a movable valve member including a cylindrical body portion having an outer side wall extending generally parallel to the longitudinal axis, the outer side wall of the movable valve member being configured to engage the inner side wall of the stationary valve member to block the flow of fluid past the stationary valve member, the body portion of the movable valve member being formed to include at least one weir configured to permit fluid flow through the at least one weir as the movable valve member moves away from the valve seat; a frame coupled to the stationary valve member; a spring extending between the frame and the movable valve member for biasing the movable valve member to a normally closed position against the valve seat; and a thermally responsive actuator coupled to the movable valve member for moving the movable valve member from the normally closed position to an open position spaced apart from the valve seat when the temperature of the fluid exceeds a predetermined temperature.

10. The apparatus of claim 9, wherein the thermally responsive actuator of the thermostat includes a power element and a stem portion which is movable relative to the power element from a retracted position to an extended position when the temperature of the fluid exceeds the predetermined temperature, the ste portion being configured to engage the stationary valve member and the movable valve member being coupled to the power element.

11. The apparatus of claim 9, wherein the at least one weir formed in the movable valve member is a three dimensional weir channel.

12. The apparatus of claim 11, wherein the movable valve member is formed to include a plurality of three-dimensional weirs, and wherein the plurality of three-dimensional weirs have at least two different geometric shapes.

13. The apparatus of claim 9, wherein the movable valve member includes a annular, cylindrically shaped body portion having the outer side wall, a top surface, and an inner side wall.

14. The apparatus of claim 13, wherein the at least one weir is formed only in the outer side wall and the top surface of the body portion of the movable valve member.

15. The apparatus of claim 13, wherein the at least one weir is aligned at an acute angle relative to the top surface of the body portion, the weir sloping downwardly toward the outer side wall.

16. The apparatus of claim 9, wherein the at least one weir is an incremental weir including first and second weir sections formed at different angles.

17. The apparatus of claim 16, wherein the incremental weir is cut through the entire body portion of the movable valve member.

18. A method for manufacturing a custom thermostat designed for a particular engine cooling system, the method comprising the steps of: evaluating factors related to performance of the engine cooling system; providing a stationary valve member configured to be positioned in a conduit of the cooling system, the stationary valve member having a valve seat defining an opening to a radiator; providing a movable valve member for engaging the valve seat to block the flow of fluid through the stationary valve member to the radiator, the movable valve member being formed to include a plurality of three- dimensional weirs configured to permit fluid flow through the plurality of weirs as the movable valve member moves away from the valve seat to control initial fluid flow to the radiator; providing a thermally responsive actuator for opening and closing the movable valve member, the thermally responsive actuator including a power element having a wax material located therein for moving a stem from a retracted position to an extended position to open the movable valve when the temperature of the fluid exceeds a predetermined level; and adjusting the geometrical configuration of the plurality of weirs formed in the movable valve member to optimize a fluid flow parameter based on the factors related to the engine cooling system determined during the evaluating step.

19. The method of claim 18, further comprising the step of adjusting a thermal expansion property of the wax material in the power element based on the factors related to the engine cooling system determined during the evaluating step.