Abstract:
A rotary valve provides single point flow control of coolant within the cooling system of an internal combustion engine. The valve distributes coolant flow from the engine in predetermined flow modes to either 1) the radiator and heater simultaneously, 2) a bypass circuit only, 3) the heater only, or 4) the radiator and bypass simultaneously. The single-point coolant control results in advantages of shorter warm-up times, a lower pressure drop (reducing power consumption by the pump), reduced engine emissions and fuel consumption, improved cabin heater performance, and improved engine durability due to reduced thermal shocks to the engine components by virtue of more precise control of engine operating temperature.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to automotive cooling systems, and, more specifically, to a multi-port valve for controlling coolant flow to all cooling system components. 
     2. Description of the Related Art 
     Conventional cooling systems for internal combustion engines include a water jacket (i.e., passages within the engine block for circulating coolant), a radiator, a fan, a heater core, a water pump, and various hoses and clamps. They also include a thermostat and/or various valves to control the flow of coolant in response to the temperature of the coolant, demand for heating of the passenger compartment, and other factors. 
     When an engine is first warming up after being started, it is known to have the coolant flow bypass the radiator so that the coolant and engine warm up more quickly. Quicker warming leads to reduced engine emissions, improved fuel economy, and improved engine performance since reaching an optimal engine operating temperature in faster time means less time spent in cold start emissions mitigation strategies. The switching of coolant flow between a bypass circuit and the radiator circuit is conventionally performed by the thermostat. A typical thermostat uses a wax motor to drive a valve between one position in which all coolant is directed through the bypass and none to the radiator and another position in which all coolant is directed through the radiator and none through the bypass. Some thermostats may gradually cutoff bypass flow while radiator flow gradually increases. 
     Internal combustion engine technology is producing engines of higher efficiency and increasingly sophisticated control methods. This has increased the need for fast warm up times and precise control of engine operating temperatures, which have not been adequately attained with conventional cooling systems. Furthermore, delays in warming up of the engine also delay the availability of heat in the passenger compartment. 
     Separate from the thermostat, a passive 2-way valve may direct coolant to a heater core when warm air is being demanded in the passenger compartment. Other valves may also be included for either cooling or heating other vehicle components, such as cooling of electronic modules or heating of seats. Achieving these additional functions becomes expensive not only because of the proliferation of valves, but also because of the proliferation of separate actuators and the wiring, cables, or hydraulic or pneumatic (e.g. vacuum) lines required to control them. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rotary valve for single point flow control of coolant resulting in advantages of shorter warm-up times, a lower pressure drop (reducing power consumption by the pump), reduced engine emissions and fuel consumption, improved cabin heater performance, and improved engine durability due to reduced thermal shocks to the engine components by virtue of more precise control of engine operating temperature. 
     In one aspect of the invention, a rotary valve for single-point coolant switching of coolant flowing in an engine cooling system comprises a valve body having an inlet port and a plurality of outlet ports. The outlet ports include a radiator port for allowing coolant flow in a radiator circuit, a bypass port for allowing coolant flow in a bypass circuit, and a heater port for allowing coolant flow in a heater circuit. A flow diverter is rotationally received in the valve body and includes a plurality of fluid passages providing predetermined flow paths between the inlet port and the outlet ports in response to a rotational position of the flow diverter. An actuator responds to a control signal for setting the rotational position. The predetermined flow paths include a first mode for distributing the coolant to the radiator port and the heater port while blocking coolant from the bypass port, a second mode for distributing the coolant to the bypass port while blocking coolant from the radiator port and the heater port, a third mode for distributing the coolant to the heater port while blocking coolant from the radiator port and the bypass port, and a fourth mode for distributing the coolant to the radiator port and the bypass port while blocking coolant from the heater port. In particular, the second mode may include a plurality of selectable flow rates to the bypass port including at least a first flow rate and a second flow rate higher than the first flow rate, wherein the first flow rate provides increased heat flow into the coolant. Thus, contrary to prior art thermostats, the slowest flow rate through the bypass may be achieved at the lowest coolant temperatures during engine startup. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing coolant flow of the present invention through a single point precision cooling valve. 
     FIG. 2 is a side view of a valve of the present invention. 
     FIGS. 3-6 are top cross-sectional views of the valve of FIG. 2 in various flow modes. 
     FIG. 7 is a plot showing port open area (i.e., flow restriction) in a further embodiment of precision cooling according to the present invention. 
     FIG. 8 is a perspective view of a valve body of the further embodiment. 
     FIG. 9 is a side view of a flow diverter to be received in the valve body of FIG.  8 . 
     FIG. 10 is a side view of the flow diverter of FIG. 9 viewed at a different rotational position. 
     FIG. 11 is a bottom, perspective view of the flow diverter of FIG.  9 . 
     FIG. 12 is a side view of the valve body and flow diverter in a rotational position to provide flow to the radiator and heater. 
     FIG. 13 is a cross-sectional view as indicated by lines A—A in FIG.  12 . 
     FIG. 14 is a cross-sectional view as indicated by lines B—B in FIG.  12 . 
     FIG. 15 is a side view of the valve body and flow diverter in a rotational position to provide flow only to the radiator. 
     FIG. 16 is a cross-sectional view as indicated by lines A—A in FIG.  12 . 
     FIG. 17 is a cross-sectional view as indicated by lines B—B in FIG.  12 . 
     FIG. 18 is a block diagram showing an overall cooling system controller. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a preferred embodiment of an internal combustion engine cooling system is shown with single-point coolant distribution using a multi-port precision cooling valve  10 . The cooling system further includes a water pump  11 , an engine  12  with a water jacket for receiving coolant flow, a radiator  13 , and a heater core  14 . Water pump  11  forces coolant to flow to engine  12  through an engine circuit  15  to valve  10 . Valve  10  distributes the coolant received from engine  12  in selectable proportions or flow rates to 1) a bypass circuit  16  which returns the coolant directly to pump  11  (i.e., bypassing radiator  13 ), 2) a radiator circuit  17  which passes coolant through radiator  13  to cool the coolant, and 3) a heater circuit  18  which passes coolant through heater core  14  to heat the passenger cabin of a vehicle. Locating valve  10  to receive at its inlet all the coolant from engine  12  facilitates single-point switching of coolant to obtain precise control of engine operating temperature, improved cabin heater performance, and other benefits. However, other overall system configurations are also possible. Furthermore, additional cooling system components such as a de-gas circuit to coolant reservoir or circuits to other auxiliary heat exchangers can be accommodated by additional ports on valve  10 . 
     FIG. 2 shows a first embodiment of multi-port valve  10  comprising a generally cup-shaped valve body  20 , a flow diverter  21  received in valve body  20 , and an actuator  22  mounted atop valve body  20 . Valve body  20  includes an inlet port or fitting  23 , a radiator outlet port  24 , a bypass outlet port  25 , and a heater outlet port  26 . Flow diverter  21  is generally cylindrically shaped or barrel shaped and has a plurality of fluid flow passages to provide predetermined flow paths therethrough as described below. A valve stem  27  extends upward from flow diverter  21  by which it is rotated within valve body  20  by actuator  22  to present different flow paths between ports. 
     Actuator  22  includes a cover  28  for containing a drive unit  30  coupled to valve stem  27  by a drive train or gear box  31 . Drive unit  30  receives a control signal for commanding a particular rotational position of flow diverter  21 . For example, drive unit  30  may be comprised of an electric motor and control signal an analog or digital command signal representative of the desired angular position of diverter  21 . Drive unit  30  could also be hydraulically or pneumatically driven with corresponding hydraulic or pneumatic inputs. The control signal may be derived from a controller (discussed below) based on several input parameters such as coolant temperature, as is known in the art. Thus, valve  10  may further include an electronic temperature sensor  32  within valve body  20  for contacting coolant flowing through the valve. 
     In the event of failure of drive unit  30  or loss of a control signal, the present invention provides a failsafe mechanism to bias flow diverter  21  into a rotational position where coolant flow is directed to the radiator circuit and to the heater circuit. Thus, a return spring  33  is coupled between cover  28  and valve stem  27  to urge flow diverter  21  into the failsafe position when required. Spring  33  could alternatively be connected between cover  28  and gear box  31 . 
     Matching flanges  29  are provided for joining valve body  20  and cover  28 . Sealing gaskets provided at many points throughout the valve and alignment features for maintaining diverter  21  in position are not shown but are within the normal skill in the art. 
     In one preferred embodiment, flow diverter  21  contains fluid passages adapted to provide flow paths through valve  10  in four basic modes achieved at four respective rotational positions. A first mode is a radiator/heater mode as shown in FIG.  3 . As seen in the cross section, the flow paths result from fluid passages or channels formed within flow diverter  21  within the plane of the inlet and outlet ports. In FIG. 3, there are open paths for distributing coolant from inlet  23  to radiator port  24  and heater port  26  while coolant flow to bypass port  25  is blocked. The radiator/heater mode shown in FIG. 3 also corresponds to the failsafe position of diverter  21 . In this mode, engine warm-up is not optimized but flow to the radiator ensures that the engine is protected from overheating and flow to the heater core ensures that cabin heating is available for defrosting windows or warming the passengers. 
     FIG. 4 shows a second mode which is a bypass only mode which is selected when cold coolant temperature below a set point is detected. The only open flow path is between inlet  23  and bypass port  25 , and since coolant flow is then restricted to only the engine circuit the engine is warmed in the shortest possible time. 
     FIG. 5 shows a third mode which is a heater only mode wherein the only open flow path is between inlet port  23  and heater port  26 . This mode may be selected, for example, when there is a demand for cabin heat and the current engine operating temperature is above a predetermined minimum threshold but is still below its set operating point temperature. 
     FIG. 6 shows a fourth mode which is a radiator and bypass mode wherein there are open flow paths between the inlet port  23  and both radiator port  24  and bypass port  25 . This mode may be used when coolant temperature is near the set point to obtain lower amounts of radiator cooling. 
     One important advantage of the multi-port valve shown in FIGS. 2-6 is its low pressure drop compared to other valves used in conventional cooling systems. This results in a reduced accessory load placed upon the engine which increases fuel economy. 
     Using the four modes of FIGS. 3-6, coolant flow can be controlled to meet vehicle cooling requirements as necessary. Flow diverter  21  can also be located in rotational positions between those shown in FIGS. 3-6 to obtain variable flow rates within the several modes. 
     In a further embodiment of the present invention, various flow rate profiles at respective rotational positions of the flow diverter can be specified as shown in FIG.  7 . The flow from the inlet port to any particular outlet port is dependent upon the open area of the overlap of a particular fluid passage with the port itself. Thus, by selecting an appropriate geometry for the fluid passages within the flow diverter, any arbitrary flow rate profiles can be obtained (within practical limits). 
     FIG. 7 illustrates port open area for each port at each respective rotational position of the flow diverter. In this example, the flow diverter can be rotated to angular positions at angles between 6° and 206° from a reference position. Port open area is shown in square inches. A line  35  shows a port open area curve for the radiator port such that radiator flow is at a maximum (about 0.95 in 2 ) at 6° and drops to zero at an angular position of about 83°. Rather than dropping at a constant slope, it can drop at several rates depending upon the fluid passage geometries as shown below. A line  36  shows the open area curve for the radiator port at angular positions from zero open area at about 126° to an open area of about 0.75 in 2  at 206°. 
     A line  37  shows the curve of open port area for the bypass port. The bypass open area gradually increases from zero at 20° to a maximum of about 0.14 in 2  at about 59°. Then line  37  drops from 74° to 88° to a value of about 0.04 in 2 . It maintains this second level of restriction until about 95° and then drops to zero at about 100° angular position. 
     A line  38  shown the curve of open port area for the heater port. It rises from zero at 95° to a maximum value of 0.14 in 2  at about 117° which it maintains through 206°. Also shown are values for a de-gas port line  40  which start at 0.03 in 2  at 6° and stays constant until dropping to zero at about 83°. The de-gas port remains cutoff until about 122° and is restored to 0.03 in 2  between 132° and 206° as shown by line  41 . 
     A radiator/heater mode of coolant flow can be obtained with rotational positions in the range of about 126° to 206°. The failsafe position preferably corresponds to the angular position of 206° in this embodiment. 
     The bypass only mode can be obtained in the range of about 88° to 95°. The line  37  provides a plateau in the bypass port open area profile to allow a tolerance band with respect to positioning the diverter to achieve the desired coolant flow. The plateau corresponds to a fluid passage geometry that provides a constant overlapping area with the port over the range of diverter rotation. 
     The heater only mode can be obtained at rotational positions in the range of about 117° to 127°. The de-gas port in this embodiment may be used to pass the coolant through a de-gas bottle to remove air from the coolant. The radiator and bypass mode can be obtained at rotational positions in the range of about 6° to 74°. In particular, bypass curve  37  has a second plateau between 59° and 74° which provides a greater flow (i.e., lower restriction) than the first plateau in the bypass only mode. The slower (more restricted) flow during the bypass only mode causes a greater amount of heat flow from the engine into the coolant thereby raising the coolant temperature and bringing the engine to equilibrium more quickly. More specifically, the coolant stays in direct contact with the engine longer but still is moving enough to prevent the creation of excessive hot spots. The less restricted (i.e., faster) flow of the second plateau in the radiator/bypass mode is better suited to the desired heat flow when higher operating temperature has been obtained and allows better control of the temperature around the desired set point. Thus, the relative flow achieved in the flow modes of the present invention provides significant improvement over the prior art. 
     FIG. 8 shows an valve body  50  without hose fittings in an embodiment for achieving the flow profiles of FIG.  7 . Body  50  has an inlet port  51 , a radiator port  52 , a bypass port  53 , a heater port  54 , and a de-gas or auxiliary port  55 . In this embodiment, not all ports are located in the same plane as inlet port  51 . 
     A flow diverter  56  for providing the desired profiles of the open port areas versus angular diverter position is shown in FIGS. 9-11. Fluid passages for overlapping with inlet port  51  lead to interior chambers in diverter  56 . Other passages lead to the outlet ports at various rotational positions of the diverter. The outlets of the passages have selected geometries as shown to provide the desired overlapping port areas. Thus, passage openings include a wedge shape as shown at opening  57 , and arc shape as shown at opening  58 , a slot shape as shown at opening  59 , and circle shapes as shown at opening  60 . 
     FIG. 12 shows diverter  56  placed in valve body  50  in the angular position at 206° which is a failsafe position with flow paths to radiator port  52  and heater port  54  as shown in FIGS. 13 and 14. 
     FIG. 15 shows diverter  56  placed in valve body  50  in the angular position at 6°. A flow path is provided to radiator port  52  as shown in FIGS.  16  and flow is cutoff to bypass port  53  and heater port  54  as shown in FIG.  17 . It can be seen that with clockwise rotation from 6° that flow will begin into bypass port  53  according to the profiles shown in FIG.  7 . 
     FIG. 18 shows control of the precision cooling system wherein a microcontroller  65  controls multi-port valve  10 , pump  11 , and a fan drive  66  according to a cooling strategy customized for a particular vehicle. The angular position of the diverter in valve  10  is set according to the control signal provided from microcontroller  65  to valve  10 . The desired angular position is determined in response to a temperature signal received from valve  10  and other vehicle parameters, such as engine speed obtained from a communication link with an engine controller. Microcontroller  65  can be contained in a stand-alone module or could alternatively be placed in the same module as the engine controller or even be implemented in the same microcontroller as the one performing engine control functions.