Abstract:
An oil pan includes a chamber for containing a liquid, a first passage for containing a coolant and forming a first flow path along a length of the chamber, including a first surface located between the chamber and the first passage, and a second passage for containing the liquid coolant, communicating with the first passage and forming a second flow path along a length of the chamber, including a second surface located between the chamber and the second first passage.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to cooling transmission fluid, and, more particularly, to an automatic transmission oil pan having an oil-to-coolant heat exchanger. 
         [0003]    2. Description of the Prior Art 
         [0004]    Automatic transmission fluid (ATF) circulates continually through the transmission lubricating and cooling components that rotate at relatively high speed within a transmission case. The ATF, which is drawn by a pump from a transmission sump or oil pan located below, and secured to the transmission case, returns to the oil pan by gravity feed after circulating through the transmission. Its temperature increases in this flow path and must be lowered by passing through an oil cooler, which is usually located behind a radiator, in which heat from the engine coolant is transferred to an air stream flowing through the radiator. The system that supports this heat exchange consumes packaging space, is inefficient, costly, and cumbersome to assemble and service. 
         [0005]    There is a need in the industry for a system and method for integrating an oil-to-coolant heat exchanger/cooler in a transmission oil pan. Heat transferred from the ATF to the coolant could be transported from the transmission to the radiator, where heat from the engine coolant is transferred to the airstream that flow through the radiator. 
       SUMMARY OF THE INVENTION 
       [0006]    An oil pan includes a chamber for containing a liquid, a first passage for containing a coolant and forming a first flow path along a length of the chamber, including a first surface located between the chamber and the first passage, and a second passage for containing the liquid coolant, communicating with the first passage and forming a second flow path along a length of the chamber, including a second surface located between the chamber and the second first passage. 
         [0007]    Coolant is supplied to the transmission oil pan instead of sending ATF to a cooler at the front of the vehicle, thereby producing important advantages. ATF never leaves the transmission; therefore, oil leaks related to the cooling system and loss of transmission function due to inadequate ATF level are unlikely. In addition, the transmission operates more efficiently because its pump is not burdened with flow restrictions in cooler lines and the cooler. 
         [0008]    Eliminating the oil-to-air cooler reduces system cost, results in the deletion of the cooler by-pass valve, which also reduces cost and system complexity, and improves air flow through the engine cooler &amp; radiator at front of vehicle. 
         [0009]    Tubes needed to run coolant to the transmission cost less that tubes required to run ATF to the front of vehicle. 
         [0010]    Fewer hydraulic connections are required between the engine &amp; transmission cooling systems, thereby reducing cost and improving ease of assembly. Overall vehicle packaging space is improved, except for a deeper transmission oil pan. 
         [0011]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0013]      FIG. 1  is a schematic diagram of a powertrain cooling system; 
           [0014]      FIG. 2  is a schematic diagram of showing a transmission oil pan secured to a transmission case; 
           [0015]      FIG. 3  is an isometric view of a transmission oil pan in which heat transfer passages are located at the bottom of the pan of shown in  FIG. 2 ; 
           [0016]      FIG. 4  is schematic diagram of the oil pan shown in  FIG. 3 ; and 
           [0017]      FIG. 5  is a schematic diagram of an oil pan in which heat transfer passages are located at opposite the sides of the pan. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Referring first to  FIG. 1 , a cooling system for a vehicle powertrain  10  includes a coolant reservoir  12 , a hydraulic pump, thermostat  16 , cooler  18 , and transmission oil pan  20  with integrated cooling. Engine coolant is drawn by pump  14  from reservoir  12 , such as the water jacket of an engine block, and is supplied through thermostat  16  to cooler  18 , where heat is exchanged from the coolant to an air stream flowing through cooler  18 . Low temperature coolant exiting cooler  18  flows through oil pan  20 , where heat is exchanged from transmission oil located in the oil pan  20  to the coolant. Upon exiting the oil pan  10 , the coolant returns to pump  14 , and is recirculated through the system  10 . 
         [0019]      FIG. 2  shows the engine block  12 , the oil pan  20  secured to the bottom of a transmission case  22 , an inlet line  24  that carries coolant from cooler  18  to the oil pan, and an outlet line  26  that returns coolant from the oil pan to the cooling system  10 . 
         [0020]    Referring to  FIGS. 3 and 4 , oil pan  20  is a container having an upper flange  42  extending around its periphery and formed with a series of holes  44  for bolts, which secured the pan to a transmission case, side walls  46 ,  48  extending along the length of the pan, end walls  50 ,  52  extending along the width of the pan, a lower surface  54 , and a bottom surface  56 , spaced from the lower surface. 
         [0021]    One of the end walls  50  is formed with an inlet  60  connected to inlet line  24 , and an outlet  62  connected to outlet line  26 . The space below lower surface  54  and above bottom surface  56  is divided by a bulkhead  64  into a first passage  66  and a second passage  68 . 
         [0022]    The lower surface  54  is formed with fins  70 , which extend above surface  54  into the chamber  72  that contain transmission oil, and below surface  54  into passages  66  and  68 . Similarly, the bottom surface  56  is formed with fins  74 , which extend above surface  56  into passages  66  and  68 . Fins  70 ,  72  are secured to surfaces  54  and  56  preferably by soldering or welding, and the fins are of aluminum or copper, or another material having a relatively high coefficient of thermal conduction. 
         [0023]    In operation, coolant entering inlet  60  flows downward into passage  66 , along the length of oil pan  20 , around a space between bulkhead  64  and end wall  52 , into passage  68 , and along the length of the oil pan to outlet  62 , from which it exits the oil pan. While traversing this flow path, heat from the oil in chamber  72  is transmitted through the fins  70 ,  74  to the coolant, which is returned to the system  10  wherein heat in the coolant is transferred to the air stream that flows through the cooler  18 . 
         [0024]    When atmospheric air temperature is low, such as during winter operation, hot coolant can be sent to the heat exchanger in the oil pan  20  to heat transmission oil in the pan  20  to an optimal operating temperature, thereby improving the quality of gear shifts produced by the transmission and fuel economy. 
         [0025]      FIG. 5  illustrates a second embodiment of an oil pan  80 , which includes the upper flange  42 , bolt holes  44 , side walls  86 ,  88  extending along the length of the pan, end walls  90 ,  92  extending along the width of the pan, and a bottom surface  56 . A first bulkhead  94 , spaced laterally from side wall  86 , forms a first passage  96  in a space bounded by bottom surface  56 , bulkhead  94 , and side wall  86 . A second bulkhead  98 , spaced laterally from side wall  88 , forms a second passage  100  in a space bounded by bottom surface  56 , bulkhead  98 , and side wall  88 . 
         [0026]    One of the end walls  90  is formed with an inlet  102  connected to inlet line  24 , and an outlet  104  connected to outlet line  26 . Passages  96  and  100  are hydraulically connected by a coolant line  106 , located outside end wall  92  and extending along the length of wall  92 , i.e., across width of the pan  80 . Line  106  communicates with passage  96  through a port  108  and with passage  100  through a port  110 . Ports  108  and  110  are formed through the end wall  92 . 
         [0027]    Bulkhead  94  is formed with fins  112 , which extend into the chamber  72  that contain transmission oil, and into passage  96 . Similarly, bulkhead  98  is formed with fins  114 , which extend into the chamber  72  that contain transmission oil, and into passage  100 . End wall  86  is formed with fins  116 , which extend into passage  96 . Similarly, end wall  88  is formed with fins  118 , which extend into passage  100 . 
         [0028]    In operation, coolant entering inlet  102  flows in passage  96  along the length of oil pan  80 , exits passage  96  through port  108 , flows through line  106 , enters passage  100  through port  110 , flows in passage  100  along the along the length of the oil pan  80  to outlet  104 , from which it exits the oil pan. While traversing this flow path, heat from the oil in chamber  72  is transmitted through the fins to the coolant, which is returned to the system  10  wherein heat in the coolant is transferred to the air stream that flows through the cooler  18 . 
         [0029]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.