Patent Publication Number: US-2011067853-A1

Title: Fluid cooling device for a motor vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 11/214,473 filed 29 Aug. 2005 which claims the benefit of U.S. Provisional Patent Application No. 60/604,683 filed 27 Aug. 2004, both of which are expressly incorporated by reference as set forth fully herein. 
    
    
     TECHNICAL FIELD 
     The present teachings relate generally to the area of cooling of the fluids that are used in machinery such as engines, transmissions and other power equipment to lubricate components and/or transfer power. In one application, the present invention more particularly relates, but is not limited to, the area of cooling of transmission oil, engine oil, hydraulic oil or the like in automotive applications. Numerous other applications exist in diverse areas such as railways, ships, aircraft, machine tool, power generation equipment and others. 
     INTRODUCTION 
     A motor vehicle must be able to operate throughout a wide range of ambient temperatures. Fluids conventionally used in the automotive industry to lubricate components and transfer power are generally under significantly increased pressures during start up conditions, particularly at low ambient temperatures. Vehicle systems are required to cool these fluids. Such systems must also accommodate the upper limits of fluid pressures that may be experienced. The automotive engine oil reaches high temperatures during the operation of the engine. These high temperatures need to be reduced to avoid breakdown of the fluid. A device called an engine oil cooler is conventionally used to cool engine oil. 
     It is necessary to introduce considerable turbulence to the oil passing through these coolers to achieve the amount of cooling required in the limited space available. This turbulence is achieved by creating obstacles such as turbulators, convolutions or other hurdles to the flow of oil inside the oil cooler, which force the oil to repeatedly change direction. The turbulence increases the heat transfer, but it also causes a considerable pressure drop between the inlet oil and the outlet oil. This is particularly true when the oil is cold and becomes a serious problem at low temperatures (like most automotive components, the oil cooler must be able to operate reliably even at a temperatures of −40 degrees Fahrenheit). At such low temperatures the increased viscosity of the oil causes high pressures in the oil cooler, which can lead to burst, leaks and failure of the oil cooler and/or the lines that connect the oil cooler with the transmission. 
     Thus a need exists in the pertinent art for fluid cooling device with a pressure limiting mechanism that protects the integrity of the fluid cooling device, the lines and the transmission. 
     SUMMARY 
     The teachings for the present invention provide a fluid cooling device for a motor vehicle. The fluid cooling device may include a fluid inlet tank and a fluid outlet tank. A plurality of heat transfer tubes provide constant fluid communication between the inlet tank and the outlet tank. A bypass arrangement selectively provides additional fluid communication between the fluid inlet tank and the fluid outlet. In this regard, the bypass arrangement provides additional fluid communication between the fluid inlet tank and the fluid outlet tank under a first operating condition and the bypass arrangement precludes additional fluid communication between the inlet tank and the outlet tank under a second operating condition. The bypass arrangement may include a bypass tube and means for selectively blocking the bypass tube. The means for selectively blocking the bypass tube may be automatically responsive to a change in oil temperature or a change in oil pressure. 
     The teachings of the present invention also provide a method of fluid of a motor vehicle. The method utilizes a fluid cooling device having a fluid inlet tank, a fluid outlet tank, and a plurality of heat transfer tubes providing constant fluid communication between the inlet tank and the outlet tank. The method includes providing a bypass arrangement for selectively providing additional fluid communication between the fluid inlet tank and the fluid outlet tank. The method additionally includes operating the fluid cooling device under a first operating condition such that the bypass arrangement provides additional fluid communication between the fluid inlet tank and the fluid outlet tank. The method further includes operating the fluid cooling device under a second operating condition such that the bypass arrangement precludes additional fluid communication between the inlet tank and the outlet tank under a second operating condition. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a top view of a fluid cooling device according to the teachings of the present teachings, the fluid cooling device particularly in the form of an oil cooler. 
         FIG. 2  is a cross-section view taken along the line  2 - 2  of  FIG. 1 . 
         FIG. 2A  is an enlarged view of a portion of  FIG. 2 . 
         FIG. 3  is a top view of another fluid cooling device according to the teachings of the present invention. 
         FIG. 4  is a cross-section view taken along the line  4 - 4  of  FIG. 3 . 
         FIG. 4A  is an enlarged view of a portion of  FIG. 4 . 
         FIG. 5  is a top view of another fluid cooling device according to the teachings of the present invention. 
         FIG. 6  is a cross-section view taken along the line  6 - 6  of  FIG. 5 . 
         FIG. 6A  is an enlarged view of a portion of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS ASPECTS 
     The following description of various aspects of the invention is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. The present teachings are applicable, but are not limited to, the area of cooling of transmission oil and/or engine oil in automotive applications. The present teachings are, for example, also applicable to diverse areas such as railways, ships, aircraft, machine tool, power generation equipment and others. 
     With initial reference to  FIGS. 1 ,  2  and  2 A, a fluid cooling device in accordance with the teachings of the present invention is illustrated and generally identified at reference character  10 . The fluid cooling device is particularly illustrated as an oil cooler  10 . The oil cooler  10  may be a transmission oil cooler, an engine oil cooler or a hydraulic fluid oil cooler, for example. The oil cooler  10  is shown to generally include a first tank or inlet fluid tank  12  and a second tank or outlet fluid tank  14 . The inlet and outlet fluid tanks and  14  may be round, circular or of any suitable shape. The inlet fluid tank  12  is associated with an inlet port  16 . The outlet tank  14  is associated with an outlet port  17 . Typically, the inlet and outlet ports  16  and  17  may be threaded or equipped with some type of connector that allows the connection to the hydraulic lines leading the oil. 
     The inlet and outlet fluid tanks  12  and  14  may be connected by a plurality of heat transfer tubes  18 . The heat transfer tubes  18  provide constant fluid communication between the inlet tank  12  and the outlet tank  14 . In the exemplary illustration of  FIG. 2 , the plurality of heat transfer tubes  18  is shown to include five such tubes  18 , although any number of tubes  18  can be used. The tubes  18  may be brazed or otherwise suitably attached to the inlet and outlet tanks  12  and  14 . 
     The heat transfer tubes or cooling tubes may be configured in such a way as to provide a high degree of turbulence to the oil passing therethrough. As will be appreciated by those skilled in the art, such turbulence advantageously provides increased heat transfer within a limited space. When the oil is conventionally routed through the heat transfer tubes  18 , there is a considerable drop in pressure between inlet and outlet oil. This drop in pressure becomes substantial when the oil is cold and more viscous. 
     The complete oil cooler  10  can be immersed in a cooling medium, such as radiator coolant, typically a mixture of 50% water and 50% glycol. The heat of the oil is transferred through the tube walls to the cooling medium, so that the temperature of the oil leaving the heat exchanger  10  is significantly lower than the temperature of the oil flowing into the heat exchanger  10 . Insofar as the present invention is concerned, the inlet and outlet tanks  12  and  14  and the plurality of heat transfer tubes therebetween will be understood to be conventional in construction and operation. 
     With continued reference to the cross-sectional view of  FIG. 2 , the oil cooler  10  is further illustrated to include a bypass arrangement  20  for selectively providing additional fluid communication between the fluid inlet tank  12  and the fluid outlet tank  14 . This fluid communication is in addition to the fluid communication constantly provided by the plurality of heat transfer tubes  18 . The bypass arrangement  20  provides for the additional fluid communication between the inlet and outlet tanks  12  and  14  under a first operating condition and precludes or blocks the additional fluid communication between the inlet and outlet tanks  12  and  14  under a second operating condition. The first and second operating conditions may be dependent on the temperature of the oil in the inlet fluid tank  12 . 
     The bypass arrangement  20  may include a bypass tube in fluid communication with the inlet and outlet tanks  12  and  14  and means for selectively blocking the bypass tube  20 . As illustrated, the oil cooler  10  includes a single bypass tube  22 . In other applications, the oil cooler  10  may include  2  or more bypass tubes  22  within the scope of the present invention. The bypass tube  22  may be brazed or otherwise suitably attached to the inlet and outlet tanks  12  and  14 . In one application, the cross section of the bypass tube  22  may be elliptical in shape. Alternatively, the cross section of the bypass tube  22  may be oval, rectangular, round or any other desired shape. As will be appreciated below, the inside area of the bypass tube  22  may have substantially the same inside area as compared to the fittings and hose (not shown) attached to the inlet port  16 . 
     The means for selectively blocking the bypass tube  20  may be automatically responsive for blocking the bypass tube in response to a predetermined condition. This predetermined condition may be reached upon a predetermined temperature of the oil in the inlet tank  12 . For example, the means for automatically blocking the bypass tube may be responsive to block the bypass tube upon a predetermined oil temperature within the inlet tank  12 . This predetermined temperature may be approximately 160 degrees Fahrenheit or any other identified temperature. 
     The means for selectively blocking the bypass tube  20  may include a temperature responsive valve  24 . The temperature responsive valve  24  may include an element  26  movable between a first position and a second position in response to a change in temperature. The first position of the element  26  is shown in  FIG. 2  in solid lines. In this first position, the element  26  is spaced from the bypass valve  24  and allows for the flow of oil between the inlet tank  12  and the outlet tank  14 . The second position is shown in  FIG. 3  in phantom lines and operates to prevent oil from passing through the bypass tube  22 . 
     The element  26  of the temperature responsive valve  24  may be a bi-metal element  26 . The bi-metal element  26  may be a U-shaped strip. The bi-metal element  26  may be disposed in the inlet tank  12  and secured to the inlet tank  12  with a bracket  28 . Attachment of the element  26  to the bracket  28  may be accomplished with rivets  30  or other suitable means, including but not limited to brazing. When the inlet oil temperature is below the predetermined temperature, the bi-metal element  26  is in the first position. In this position, a very small increase in inlet pressure is required to facilitate flow from the inlet tank  12  to the outlet tank  14  through the bypass valve  24  given the similarity in inside area between the bypass tube  22  and the fittings and hose of the inlet tank  12 . Because the bypass arrangement  20  controls the maximum oil pressure of the oil cooler  10 , conventional hoses and fittings do not need to be as heavy. When most of the oil flow is through the bypass tube  22  rather than the heat exchange tubes  18 , the oil temperature rises to an optimum operating temperature more quickly. In this manner, the disadvantages of cold starts are overcome. 
     When the oil temperature in the inlet tank  12  reaches the predetermined temperature, the bi-metal element  26  moves to the second position. In this second position, an end  32  of the bi-metal element  26  covers an end of the bypass tube  22  thereby blocking the flow of oil through the bypass tube  22 . The oil is resultantly routed through the heat exchange tubes  18  for cooling. It will be appreciated by those skilled in the art that the properties of the bi-metal element  26  may be selected in a conventional manner to attain closure of the bypass tube  22  at a particular temperature. 
     Turning to  FIGS. 3 ,  4  and  4 A, another embodiment of a fluid cooling device particularly in the form of an oil cooler according to the teachings of the present invention is illustrated. This embodiment is generally identified at reference character  100 . Given the similarities between the oil cooler  100  and the previously described oil cooler  10 , like reference numbers will be used to denote similar elements. The oil cooler  100  differs from the oil cooler  10  by incorporating an alternate means for selectively blocking the bypass tube  20 . 
     As illustrated in the cross-sectional view of  FIG. 4 , the inlet tank  12  may include a primary chamber  12 A and a secondary chamber  12 B. The primary chamber  12 A is in constant fluid communication with the inlet port  16 . The plurality of heat transfer tubes are in constant fluid communication with the primary chamber  12 A. The bypass tube  22  is in constant communication with the secondary chamber  12 B. The means for selectively blocking the bypass tube  20  may include a wall or baffle  102  partitioning the primary chamber  12 A from the secondary chamber  12 B. The wall may include an orifice  104  from providing communication between the primary and secondary chambers  12 A and  12 B. The means for selectively blocking the bypass tube  20  may include a movable element  106  for opening and closing the orifice  104 . The element  106  may be movable between a first position and a second position in response to a change in temperature. The first position of the element  106  is shown in  FIG. 5  in solid lines. In this first position, the element  106  is spaced from the orifice  104  and allows for the flow of oil from the primary chamber  12 A to the secondary chamber  12 B. The second position is shown in  FIG. 5  in phantom lines and operates to prevent oil from the primary chamber  12 A to the secondary chamber  12 B. 
     The element  106  may be a bi-metal element in the shape of a helix. Alternatively, the bi-metal element  106  may be in the shape of a cantilevered straight beam, a U-beam, a spiral coil or any other suitable shape. At a first predetermined inlet oil temperature, the element  106  starts to close the orifice  104 . The orifice  104  becomes fully closed at a second predetermined inlet oil temperature. 
     Turning to  FIGS. 5 ,  6  and  6 A, another embodiment of a fluid cooling device in the form of an oil cooler according to the teachings of the present invention is illustrated. This embodiment is generally identified at reference character  200 . Again given the similarities between the oil cooler  200  and the previously described embodiments, like reference numbers will be used to denote similar elements. The oil cooler  200  differs from the oil cooler  10  by incorporating an alternate means for selectively blocking the bypass tube  20 . 
     As illustrated in the cross-sectional view of  FIG. 6 , the inlet tank  12  may include a primary chamber  12 A and a secondary chamber  12 B. The primary chamber  12 A is in constant fluid communication with the inlet port  16 . The plurality of heat transfer tubes are in constant fluid communication with the primary chamber  12 A. The bypass tube  22  is in constant communication with the secondary chamber  12 B. The means for selectively blocking the bypass tube  20  may include a wall or baffle  102  partitioning the primary chamber  12 A from the secondary chamber  12 B. The wall  102  may include an orifice  104  from providing communication between the primary and secondary chambers  12 A and  12 B. The means for selectively blocking the bypass tube  20  may include a valve  202  for opening and closing the orifice  104 . The element  106  may be movable between a first position and a second position in response to a change in pressure. The first position of the valve  202  is shown in  FIG. 6  in solid lines. In this first position, the valve  202  is adjacent the orifice  104  and prevents the flow of oil from the primary chamber  12 A to the secondary chamber  12 B. The second position is shown in  FIG. 7  in phantom lines. In this position, the valve  202  permits oil to flow from the primary chamber  12 A to the secondary chamber  12 B. 
     The valve  202  may be controlled by a spring  204 . The spring  204  may circumferentially surround a post extending into the secondary chamber  12 B of the inlet fluid tank  12 . The spring  204  normally urges the valve  202  to the first or closed position. When the inlet oil pressure is greater than the force of the spring  204 , the valve  202  is displaced downwardly and no longer closes the orifice  104 . In this manner, the system pressure of the oil cooler  200  is limited. 
     It will now be appreciated that the teachings of the present invention provide a fluid cooling device for a motor vehicle that limits the pressure of the fluid flowing through its cooling tubes. The present teachings additionally provide a pressure-limiting system based on a simple, inexpensive and durable bypass mechanism. Further, the present teachings provide a bypass system that automatically responds to the lower temperatures, as well as an alternate system that bypasses the fluid based upon the pressure of the inlet fluid. Still yet further, the present teachings provide a fluid cooling device that will allow the vehicle&#39;s transmission to reach optimum operating temperature more quickly than with conventional oil coolers. 
     While the above description is directed to a particular embodiment, it will be understood that the present teachings have application to various other arrangements. For example, the present teachings may be adapted for an arrangement in which the oil cooler is not housed within one of the radiator tanks, but rather within a separate container filled with coolant. Such an arrangement may incorporate a fluid pump to circulate the coolant in the container. Such an arrangement may be particularly beneficial for heavy truck applications. 
     It will be understood that the present teachings may be adapted for engine oil cooling applications, as opposed to the transmission oil cooling applications described above. In such an arrangement, the application may be an oil-to-fluid application (i.e., inside a radiator tank or in a separate dedicated fluid container) or an oil-to-air application (e.g., placed in the front of the vehicle to benefit from air flow resulting from wind and a cooling fan). The same transmission oil cooler may be adapted for use in an oil-to-air application, which can be done: a) by increasing the size of the cooling surfaces to account for smaller heat exchange as compared to air-to-liquid; b) by adding cooling fins in contact with the cooling tubes of the oil cooler to increase total cooling area; c) by providing a cooling fan that increases airflow through the oil cooler; or by using combination of these or other measures. 
     The foregoing discussion discloses and describes merely exemplary arrangements of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.