Abstract:
An improved cooling system for an internal combustion engine is disclosed. The system utilizes an electronically controlled butterfly valve to control coolant flow between the engine and a radiator, thereby maintaining the engine temperature at a substantially optimum temperature. The valve includes a valve housing having an inlet port in fluid communication with an outlet port. A valve core is seated in the housing for selectively opening and closing the outlet port. A driving mechanism is operatively coupled to the valve core for positioning the valve core between open and closed positions relative to the outlet port. A damping mechanism is coupled between the driving mechanism and the valve core for preventing the driving mechanism from locking in the open or closed position during loading of the valve core with the housing and inlet or outlet ports.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims all the benefit and priority under 35 USC 119(e) to U.S. Provisional Patent Application No. 60/268,492 filed on Apr. 26, 2001 and No. 60/309,527 filed on Aug. 1, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The subject invention relates generally to cooling systems for internal combustion engines of automotive vehicles and, more particularly, to an electromagnetically controlled thermostat valve for controlling the flow of liquid coolant to a radiator.  
           [0004]    2. Description of the Related Art  
           [0005]    An internal combustion engine that powers an automobile normally has a liquid cooling system for removing waste heat generated by the combustion process in the engine. Such a cooling system may comprise a pump operated by the engine, a radiator, and a thermostat valve. As the pump circulates liquid coolant through the system, engine heat is transferred to the coolant passing through engine coolant passages. When the engine has reached a predetermined operating temperature, the thermostat valve opens to allow coolant to flow through the radiator where heat is transferred from the coolant to ambient air passing across exterior surfaces of the radiator. Hence, the thermostat valve restricts coolant flow to the radiator until the engine heats the coolant to a temperature corresponding to the operating temperature of the engine. This allows a cold engine to reach the desired operating temperature more quickly. Once the thermostat valve has fully opened, the temperature of the coolant, and hence that of the engine, can fluctuate over a range of operating temperatures determined by various factors such as the size of the radiator, the rate at which the pump pumps liquid coolant through the radiator, how the engine is being operated, and the ambient air temperature. Should the operating temperature fall below this range, the thermostat valve will once again restrict flow to the radiator in an effort to restore the operating temperature of the engine.  
           [0006]    Most thermostat valves have bimetallic coil or wax pellet type actuators. These valves are self-contained devices that open and close according to predetermined temperature limits. They have certain disadvantageous operating characteristics, including relatively slow response times and relatively wide switching hysteresis. Such characteristics result in a wide range of temperatures over which the valve operates between closed and open positions. Hence, such thermostats exhibit relatively loose temperature regulation. Furthermore, conventional thermostats do not allow optimal control over the cooling system because they passively respond to changes in coolant temperature only. Other factors, such as actual engine temperature, engine speed, coolant flow rate, and ambient air temperature cannot be utilized when setting the operating state of such thermostats.  
           [0007]    Active thermal management control systems increase the fuel economy of automobiles, and use an electrically-controlled flow divider, or so-called proportional thermostat valve. Existing electromagnetic thermostat valves use linear actuators to replace wax pellets found in conventional thermostats. Although this design allows control by a central computer, the valve movement is against the fluid flow direction, just like in a conventional thermostat. Therefore, the linear actuator requires a constant power supply. Furthermore, the valve only has very a limited number of configurations, which are insufficient to achieve optimal and efficient operating conditions.  
           [0008]    An example of a proportional coolant valve that is driven by a rotary actuator is disclosed by Busato et al in U.S. Pat. No. 5,950,576. The rotary actuator of this valve has to overcome a friction torque created by a coil spring against a moving element, and hence, also requires a constant power supply.  
           [0009]    Another disadvantage arises with both types of valve systems when debris and impurities such as iron oxide, sand or scale is present in the coolant. The debris can cause clogging or potential seizure of two surfaces that move relative to one another.  
         SUMMARY OF THE INVENTION  
         [0010]    The apparatus of the present invention addresses the need for a more rapid and effective control of coolant temperature than conventional systems. To obtain high cooling efficiencies, the thermostat valve according to one aspect of the invention is controlled via a central computer by monitoring other variables in addition to coolant temperature, such as engine block temperature, engine speed, coolant flow rate, and ambient air temperature. This control is achieved with a relatively simple mechanical device that affords complete control over the amount of coolant flow that reaches the radiator. Additional benefits include minimal power consumption to operate the valve, and the ability to independently control fluid flow to the radiator or bypass valves.  
           [0011]    The apparatus of the present invention also addresses the need for a valve that is unaffected by the level of impurities in the coolant. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0013]    [0013]FIG. 1 is an exploded orthogonal view of the thermostat valve and actuator according to the present invention;  
         [0014]    [0014]FIG. 2 is an exploded orthogonal view similar to that shown in FIG. 1, wherein the actuator includes a DC motor with a worm gear set;  
         [0015]    [0015]FIG. 3 is a top view of the valve and actuation components;  
         [0016]    [0016]FIG. 4 is a cross-sectional view taken along line  4 - 4  of FIG. 3;  
         [0017]    [0017]FIG. 5 is a detailed perspective view of the valve housing with a specially contoured inside wall;  
         [0018]    [0018]FIG. 6 is a detailed perspective view of the sealing plate;  
         [0019]    [0019]FIG. 7 is a detailed perspective view of the valve core;  
         [0020]    [0020]FIG. 8 is a cross-sectional side view of the valve body and butterfly valve core whereby coolant flows to both the main passage and the bypass passage;  
         [0021]    [0021]FIG. 9 is a cross-sectional top view of the valve body and butterfly valve core whereby coolant flows to both the main passage and the bypass passage;  
         [0022]    [0022]FIG. 10 is a schematic graph illustrating the relationship between the throttling areas of the main port and bypass port as a function of the valve rotary angle;  
         [0023]    [0023]FIG. 11 is a schematic graph illustrating the flow distribution between the main outlet port and the bypass port as a function of the valve rotary angle;  
         [0024]    [0024]FIG. 12 is a cross-sectional top view of the valve body and butterfly valve core whereby coolant flows to only the bypass passage;  
         [0025]    [0025]FIG. 13 is a cross-sectional top view of the valve body and butterfly valve core whereby coolant flows to only the main outlet passage;  
         [0026]    [0026]FIG. 14 is a cross-sectional view of an alternative embodiment whereby the throttling openings are C-shaped;  
         [0027]    [0027]FIG. 15 is a cross-sectional view of an alternative embodiment whereby the butterfly valve core has two circular wings;  
         [0028]    [0028]FIG. 16 is a cross-sectional view of the proportional valve having an alternative worm gear subassembly driving mechanism;  
         [0029]    [0029]FIG. 17 is a cross-sectional view of the worm gear subassembly of FIG. 16;  
         [0030]    [0030]FIG. 18 is an exploded view of the worm gear subassembly of FIG. 17;  
         [0031]    [0031]FIG. 19 is a perspective view of an alternative embodiment of the butterfly valve with cone-shaped vane flow restrictors;  
         [0032]    [0032]FIG. 20 is a top perspective view of the alternative butterfly valve and cone-shaped vane flow restrictor seated adjacent the bypass port;  
         [0033]    [0033]FIG. 21 is a cross-sectional view of the alternative butterfly valve and cone-shaped van flow restrictor seated in the bypass port;  
         [0034]    [0034]FIG. 22 is an exploded perspective view of yet another alternative embodiment of a thermostat valve assembly having a failsafe mechanism;  
         [0035]    [0035]FIG. 23 is a side view of the valve assembly of FIG. 22 in normal operating and locked position;  
         [0036]    [0036]FIG. 24 is a perspective view of the valve assembly of FIG. 22 with the failsafe mechanism in the unlocked position;  
         [0037]    [0037]FIG. 25 is a perspective view of the valve assembly of FIG. 22 with the butterfly valve rotated to the failsafe open position;  
         [0038]    [0038]FIG. 26 is a cross-sectional view of the valve assembly and failsafe mechanism in the locked position; and  
         [0039]    [0039]FIG. 27 is a cross-sectional view of the valve assembly and failsafe mechanism in the unlocked position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]    Referring to FIGS. 1 through 4, wherein like numerals indicate like or corresponding parts throughout the several views, FIG. 1 shows an electromagnetically controlled thermostat valve assembly  10  comprising a valve housing  1 , a valve core  2 , a sealing plate  3 , a cover  4 , an electric driving mechanism or actuator  5 , a valve position sensor  6 , seals  7  and  8 , and bolts  9 . Bushings or bearings may be necessary to support the valve rotary shaft, although such bushings or bearings are not illustrated. The valve position sensor  6  may not be necessary, depending on the actuation system used.  
         [0041]    The actuator  5  can be any actuator that can overcome the load torque of valve core  2  and output valve rotary position, including, but not restricted to, DC motors, stepper motors, servomotors, gear motors, controllable rotary solenoid actuators, and linear actuators with moment arms. A cost effective actuator may be a DC motor with a worm gear set, as shown in FIG. 2. The driving mechanism or actuator  5  shown in FIG. 2 includes a DC motor SA, worm gear SB, worm  5 C and two bushings which are not labeled. A “Hall effect” rotary position sensor  6  is mounted on the shaft of valve core  2  through a connector (not labeled). This type of actuator can maintain a required valve position without continuous power consumption because of the operating characteristics of a worm gear set. The sensor  6  measures valve position and provides feed back of the measured signals to a central controller or CPU, which provides the control strategy for controlling the rotary movement of the DC motor. Such a control system is well known and is outside the scope of the present invention.  
         [0042]    As illustrated in FIG. 5, valve housing  1  has an inlet port  1 A, a main outlet port  1 B, a bypass outlet port  1 C and a cavity hole  1 J and a specially designed inside wall. A round counter-bore hole  1 G is used to seat the sealing plate  3 , which is detailed in FIG. 6. A hole  1 H is counter-bored down into the bottom surface  1 F for bushing the bottom part of shaft  2 G of valve core  2 , which is detailed in FIG. 7. The inside wall of valve housing  1  has two working portions which are labeled ID and  1 E. The sealing plate  3 , as shown in FIG. 6, has two grooves  3 C,  3 E on surfaces  3 B and  3 D for seating seals  7  and  8  respectively. The hole surface  3 D supports the valve rotation shaft  2 G. Sealing plate  3  with seals  7  and  8  prevents coolant from entering the driving system. The valve core  2  has two throttling edges  2 A and  2 B, a top surface  2 C and bottom surface  2 D. The shaft  2 G is supported on surfaces  2 E and  2 F by bearings or bushings and transmits rotary movement and torque from driving actuator  5  to valve core  2 . The cross-sectional view shown in FIGS. 8 and 9 illustrate the assembly of the main components of the present invention.  
         [0043]    As described earlier, the valve housing  1  has two working portions labeled  1 D and  1 E which are essential features of the present invention. The two inside wall surfaces  1 D and  1 E, and the bottom surface  1 F of valve housing  1 , together with the bottom surface  3 A of sealing plate  3 , and cylindrical end surfaces  2 A and  2 B of valve core  2  collectively form two rectangular throttling openings through which coolant can flow, as indicated by arrows shown in FIG. 9.  
         [0044]    At any valve position, the respective areas of two openings determine the flow distribution between the main passage outlet port  1 B and bypass outlet port IC. The opening area for main passage flow at a given valve angular position is defined by the height of butterfly valve core  2  and the shortest distance between end surface  2 A of valve core  2  and inside wall surface  1 D of valve housing  1 . Similarly, the opening area for bypass flow depends on the height of butterfly valve core  2  and the shortest distance between end surface  2 B of valve core  2  and inside wall surface  1 E of valve housing  1 . The working portions  1 D and  1 E of inside wall of valve housing  1  are designed such that the area of two openings varies from 0 to a saturated value, corresponding to a fully opened valve. The relationships between the throttling areas of the main port and bypass, relative to the valve rotary angle, are shown in FIG. 10.  
         [0045]    Sealing surfaces  1 K and  1 L allow the vanes  2 H and  2 J to seal against the housing when closing either port  1 B or  1 C. For the contour design shown in FIG. 9, the flow distribution between main port  1 B and bypass port  1 C, relative to the valve rotary angle, is shown in FIG. 11.  
         [0046]    [0046]FIG. 12 shows a butterfly valve position whereby the main port  1 B is fully closed and the bypass port  1 C is fully open, while FIG. 13 shows the opposite valve position, whereby the main port  1 B is fully open and the bypass port  1 C is fully closed.  
         [0047]    In another embodiment, the concept of a specially contoured inside valve housing wall is applied to the bottom surface IF of valve housing  1  and the bottom surface  3 A of sealing plate  3  to form “C” shaped or “L” shaped throttling openings for the main port and bypass port. FIG. 14 illustrates a possible configuration with “C” shaped throttling openings and a butterfly valve core with two circular wings. Of course, different opening configurations can be achieved by designing different shapes for surfaces  1 F,  3 A,  1 D and  1 E. These specially designed surfaces form two wedging flow passages for the main output port and bypass, so that any debris present in the coolant can easily pass through them without clogging the valve.  
         [0048]    In the case where only the inside wall of valve housing  1  has specially-designed surfaces  1 D and  1 E, wipers made of suitable soft material may be embedded in top surface  2 C and bottom surface  2 D of the valve core  2  to wipe away debris on surfaces IF and  3 A. Yet another solution involves designing the valve core  2  with wedge shaped top and bottom surfaces, assuming a slight leakage between those surfaces is allowable.  
         [0049]    The degree of control over the coolant flow is much larger than in conventional systems, such that the electromagnetic thermostat is capable of more precise temperature regulation in the engine, leading to improved operating efficiencies and potentially reduced tailpipe emissions.  
         [0050]    As stated before, sealing surfaces  1 K and  1 L allow valve vanes  2 H and  2 J to seal against the valve housing, closing either port  1 B or  1 C. However, if a driving mechanism is a worm gear set driven by a DC motor then when a control system attempts to drive the valve vanes  2 H or  2 J past their limit positions  1 K or  1 L at a sufficiently high speed, the abrupt stop of valve vane  2 H or  2 J by the sealing surface  1 K or  1 L may generate a sufficiently large impact load acting on the valve vane  2 H or  2 J, resulting in self locking of the worm gear set, which makes rotation of the valve  2  in the opposite direction difficult. In order to overcome the above-mentioned problems which may be caused by the control system or driving mechanism  5 , a damping mechanism maybe introduced into this invention.  
         [0051]    [0051]FIG. 16 shows the cross section of the assembly of another embodiment of the proportional valve with a worm gear subassembly. FIG. 17 shows the cross-section of the worm gear subassembly with a clutch damping mechanism while FIG. 18 shows an exploded view of the worm gear sub-assembly. The worm gear subassembly is used to replace worm gear  5 B shown in FIG. 2. As shown in FIG. 17, the worm gear subassembly with a clutch damping mechanism includes a clutch base  12 , a wave spring washer or a disc spring washer  14 , a retaining ring  16 , and a worm gear  5 B. The clutch base  12  is keyed to valve core  2  through the bore hole  18  with key ways and has a shaft surface  20  which provides an assembly base for the worm gear  5 B. There is a clearance between the worm gear bore hole  5 B- 1  and the shaft surface  20  of clutch base  12 . This allows a rotational degree of freedom between worm gear SB and clutch base  12 . One or more compressed wave spring washers or disc spring washers  14  are placed between worm gear  5 B and clutch base  12 . The recess on clutch base  12  provides space for spring  14 . Retaining ring  16  holds the worm gear  5 B in place and bears the reacting force that the compressed spring  14  exerts on worm gear  5 B.  
         [0052]    Referring to FIG. 16, when the worm  5 C driven by a rotary actuator (DC motor) drives worm gear  5 B, the compressed spring  14  generates a drag torque acting on clutch base  12 , which drives valve core  2 . The selection of spring  14  and its pre-load ensures that the drag torque is sufficiently large to overcome the maximum load torque acting on the valve core shaft. However, the worm drive  5 B and  5 C must be able to overcome this drag torque and rotate relative to clutch base  12  when a sudden stop of valve vanes  2 H or  2 J by sealing surfaces  1 K or  1 L occurs. Such a selection and setting of spring  202  effectively prevents worm gear set  5 B and  5 C from being jammed or self locked.  
         [0053]    In order to eliminate possible jamming of worm gear set, a spring loaded clutch is used as a damping mechanism for this embodiment of present invention. Such a damping mechanism may not be necessary if a suitable control strategy is used in the control system of the proportional valve to prevent impact from taking place. Obviously, other damping means can be used. For example, elastic materials may be attached on sealing surfaces  1 K and  1 L to reduce possible impact. Using elastic materials and corresponding structure design to replace the spring loaded clutch may be another possible option. Furthermore, hydraulic damping principle may be considered as a choice.  
         [0054]    Referring to FIGS.  19 - 21 , an alternative embodiment of a butterfly valve is shown at  30 . The valve  30  includes a pair of spaced apart vanes  32 ,  34  extending outwardly from a valve rotation shaft  36  which is rotatably seated in the valve housing  1  as previously described. Each of the vanes  32 ,  34  is a generally rectangular planar plate and each includes a cone-shaped flow restrictor  38  protruding from the center thereof. The flow restrictors  38  are position to align with and be seating in the opening formed in the main outlet port  1 B and bypass outlet port  1 C to improve the flow characteristics of the fluid through the valve assembly  10  between the open and closed positions. More specifically, a flat vane allows for a rapid increase in coolant flow within the first few degrees of valve rotation creating a nonlinear relationship between fluid flow and vane angle diminishing the valve&#39;s ability to regulate or modulate small amounts of coolant flow as the vane or valve begins to open. The addition of the cone shaped flow restrictor protrusions  38  on the back side of the vanes  32 ,  34  gradually restricts the coolant flow at the extreme vane position, or in the first few degrees of vane rotation between open and closed, and therefore creates a more linear flow characteristic and better flow control in the extreme initial range of 10 degrees of vane or valve rotation. As shown in FIGS. 20 and 21, the restrictor  38  on the vane  34  gradually rotates and closes into the opening of the bypass port  1 C to gradually and uniformly open or close the port  1 C and linearly control the flow of coolant flow therethrough.  
         [0055]    Finally, referring to FIGS.  22 - 27 , yet another alternative embodiment of the valve assembly is shown at  50 . The valve assembly  50  includes the butterfly valve core  30  of FIG. 19 includes the pair of vanes  32 ,  34  with cone-shaped flow restrictors  38 . The vanes  30  project outwardly from a hollow, cylindrical valve rotation shaft  52 . A clutch housing  54  is seated on the top portion of the valve shaft  52  for cooperative engagement with the worm gear drive assembly  5 . The clutch housing  54  has a hollow, cylindrical center  56  in mating engagement with the hollow shaft  52 . The valve assembly  50  further includes a failsafe mechanism  58  to prevent the drive assembly  5  from self-locking when the vanes are in the locked or closed position against the valve openings. More specifically, the failsafe mechanism  58  includes a cone-shaped locking key  60  slidably received in the hollow shaft  52  and capable of slidably projecting into the hollow center  56  of the clutch housing  54 . Further, the locking key  60  is rotationally keyed to the clutch housing  54  to prevent relative rotation therebetween, but freely rotatable within the hollow shaft  52  of the butterfly valve  30 . The locking key  60  includes a cylindrical hollow center bore  62  and a pair of locking tabs  64  projecting outwardly from the lower portion of the outer cylindrical wall for cooperation with the valve shaft  52 . Specifically, the valve shaft  52  includes tapered cut-out windows  66  for receiving the locking tabs  64  wherein the windows  66  retain the locking tabs  64  and prevent rotation of the locking key  60  within the valve  30  in the locked position seated in the bottom of the shaft  52  and spaced from the clutch housing  54 , as shown in FIG. 26, and allow rotation of the valve  30  around the locking key  60  in the unlocked position, as shown in FIG. 27. A coil spring  68  is seated around the locking key  60  within the hollow valve shaft  52  and compressed to bias the locking key  60  to the locked position.  
         [0056]    The failsafe mechanism  58  further includes an actuator element  70 , which in the preferred embodiment is a was element, seated in the hollow center bore  62  of the locking key  60  for actuating the locking key  60  between the locked and unlocked positions. The actuator  70  includes a heat activated stem  72  which stocks similar to a piston in response to a predetermined temperature. As shown in FIG. 27, when the actuator  70  is subjected to a predetermined temperature, the stem  72  extends longitudinally to engage with the locking key  60  and slide the key  60  longitudinally within the valve shaft  52  releasing the locking tabs  64  from the windows  66  and disengaging the locking key  60  from the valve  30  in the unlocked position to allow rotation of the valve  30 . The actuator  70  is enclosed within the bore  62  by a cap  74  which covers and closes the end of the locking key  60  and valve shaft  52 . The failsafe mechanism is calibrated to a temperature slightly above the normal extremes of the coolant temperature such that ifthe valve  30  locks in the closed position, the coolant temperature will quickly increase, causing the stem  72  to stroke and disengage the valve  30  from the locking key  60 . The coolant pressure through the inlet port lA will then rotate the valve  30  partially open and prevent the engine from overheating.  
         [0057]    Having now fully described the invention, any changes can be made by one of ordinary skill in the art without departing from the scope of the invention as set forth herein.