Abstract:
An automatic transmission is provided. One embodiment of the automatic transmission may include a valve body including control valves for hydraulically controlling a friction engaging element provided within said transmission. The automatic transmission may further include an electric control unit located on said valve body for controlling gear shifting of said automatic transmission. The automatic transmission may further include a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism and an outer wall provided adjacent to said peripheral wall, wherein said electric control unit is located within a containing space surrounded by said peripheral wall, said outer wall and said valve body.

Description:
TECHNICAL FIELD 
       [0001]    The present description relates to automatic transmissions. More particularly, the description pertains to automatic transmissions having a transmission case in which an electric control unit is located while avoiding thermal damage to the electric control unit from high temperature hydraulic oil. 
       BACKGROUND AND SUMMARY 
       [0002]    Some automatic transmissions installed in automobiles are configured to change a power-flow path by changing an engagement state of plural friction elements to select a certain gear from among plural gears having different gear ratios. 
         [0003]    In some automatic transmissions, a control valve unit incorporating plural electromagnetic control units for changing an oil passage in a hydraulic system for engaging or disengaging the friction elements is integrally located on a lower side of a gear shift mechanism. 
         [0004]    In recent years, the number of selectable gears in automatic transmissions has been increased to improve travelling performance and/or fuel-efficiency of an automobile. 
         [0005]    In some conventional automatic transmissions, an electric control unit for controlling the control valve unit is located outside of a transmission case. 
         [0006]    But this design has a disadvantage of high manufacturing cost in the case where the automatic transmission has a relatively high number of selectable gears, since it requires many lengthy harnesses for connecting the electric control unit to the large number of control valves corresponding to the high number of selectable gears. 
         [0007]    One technology for addressing this disadvantage has been developed, in the form of an automatic transmission for an automobile including a harness integrated insulating sheet and an electric control unit located on the upper side of a valve body of a control valve unit immediately beneath a gear shift mechanism. The reference further discloses a plastic protective cover that covers above the electric control unit, and a rotation sensor, oil temperature sensor and oil pressure sensor that are provided in the harness integrated insulating sheet at an outside of the plastic protective cover. One example of such an automatic transmission is described by U.S. Pat. No. 6,530,856. 
         [0008]    However, the inventor herein has recognized a disadvantage with such approaches. Specifically, although the automatic transmission described in above reference can shorten the length of harnesses for connecting an electric control unit with electromagnetic control valves, by locating the electric control unit on the upper side of a valve body of a control valve unit immediately beneath a gear shift mechanism via a harness integrated insulating sheet, the electric control unit can experience thermal damage from high temperature oil for cooling the gear shift mechanism dispersed from the gear shift mechanism, which usually contacts the upper surface of the plastic protective cover, thereby decreasing the durability of the electric control unit. 
         [0009]    A first aspect of the present invention includes an automatic transmission including a valve body including control valves for hydraulically controlling a friction engaging element provided within said transmission. The automatic transmission may further include an electric control unit located on said valve body for controlling gear shifting of said automatic transmission. The automatic transmission may further include a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism and an outer wall provided adjacent to said peripheral wall, wherein said electric control unit is located within a containing space surrounded by said peripheral wall, said outer wall and said valve body. 
         [0010]    This automatic transmission overcomes at least some of the disadvantages of above reference. 
         [0011]    Since an electric control unit is located within a containing space formed by a peripheral wall, an outer wall provided adjacent to the peripheral wall and a valve body, the electric control unit can be located offset forwardly from immediately beneath the gear shift mechanism by utilizing a dead space formed inside of the outer wall of the transmission case. Accordingly, the electric unit can be located in a position where it does not experience heat damage from high temperature oil dispersed from the gear shift mechanism while the electric unit is located inside of the transmission case, thereby, preventing durability decreasing of the electric control unit. 
         [0012]    A second aspect of the present invention includes an automatic transmission including a valve body including control valves for hydraulically controlling a friction engaging element provided within said transmission, and an electric control unit located on said valve body for controlling gear shifting of said automatic transmission. The automatic transmission may further include a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism, an outer wall provided adjacent to said peripheral wall, and a containing space surrounded by said peripheral wall, said outer wall and said valve body such that a shape of said containing space is convex upward, wherein said electric control unit is located within said containing space. 
         [0013]    This automatic transmission also overcomes at least some of the disadvantages of above reference. 
         [0014]    In an example embodiment, the automatic transmission may further comprise a primary shaft coaxially positioned relative to an engine output shaft and provided in said gear shift mechanism, a secondary shaft extending parallel to and located above and behind said primary shaft, and a differential axis extending parallel to and located below and behind said primary shaft, wherein said valve body is located under said gear shift mechanism, and said containing space is positioned on a forward side of said gear shift mechanism. 
         [0015]    In another example embodiment, the automatic transmission further comprises a rotation sensor for detecting a rotation speed of a designated rotating element of said gear shift mechanism, wherein said rotation sensor is integrated with and extending diagonally from said electric control unit. 
         [0016]    In another example embodiment, the automatic transmission further comprises a torque convertor, wherein said rotation sensor is spatially positioned intermediate said electric control unit and said torque convertor. 
         [0017]    In another example embodiment, the automatic transmission further comprises a manual valve provided in said valve body and moving in conjunction with a shift range changing operation via a shift lever, and a position detecting sensor for detecting a position of said manual valve, wherein said position detecting sensor is integrated with said electric control unit. 
         [0018]    As a non limiting example, the manual valve is located parallel with said primary shaft and is configured to move in an axial direction of the primary shaft. 
         [0019]    In one example embodiment, the valve body is one of a plurality of valve bodies, and the automatic transmission further comprises a control valve unit including the plurality of valve bodies stacked in an up and down direction. Further, said manual valve is provided in a one of the valve bodies located on a top portion of said control valve unit, and said electric control unit is located on an upper side of said valve body located on the top portion of said control valve unit. 
         [0020]    A third aspect of the present invention includes an automatic transmission including a transmission case having a peripheral wall for at least partially enclosing a gear shift mechanism and an outer wall provided adjacent to said peripheral wall. The peripheral wall and outer wall of the transmission case are formed to at least partially define, with a valve body associated with the transmission case, a containing space sized to contain an electric control unit located on the valve body. 
         [0021]    In this way, at least some of the disadvantages of the related reference described above are overcome. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a schematic diagram showing an automatic transmission according to an embodiment of the present invention. 
           [0023]      FIG. 2  is a table showing a relationship between coupling combinations of friction-engaging elements and gear positions. 
           [0024]      FIG. 3  is a front view of the automatic transmission. 
           [0025]      FIG. 4  is a left side view of the automatic transmission. 
           [0026]      FIG. 5  is a perspective view of an electronic control unit, rotation sensors, and a manual valve, etc. 
           [0027]      FIG. 6  is a perspective view of the electronic control unit and the rotation sensors. 
           [0028]      FIG. 7  is a partial cross-sectional view of a containing space in which the electronic control unit is accommodated and its vicinity portion. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Hereafter, the best mode to implement the present invention will be explained based on the accompanying drawings. 
         [0030]      FIG. 1  is a schematic diagram showing a configuration of an automatic transmission  1  according to an embodiment of the present invention. In this embodiment, the automatic transmission  1  is applied to an automobile in which an engine is side-mounted, such as a front-engine front-wheel drive (FF) vehicle. The automatic transmission  1  primarily includes a torque converter  3  attached to an engine output shaft  2 , and a gear-shift mechanism  5  into which an output rotation of the torque converter  3  is inputted via an input shaft  4 . The gear-shift mechanism  5  is accommodated inside a transmission case  6  in a state where it is arranged on the axial center of the input shaft  4 . 
         [0031]    The output rotation of the gear-shift mechanism  5  is transmitted to a differential device  9  via a counter-drive mechanism  8  from an output gear  7  that is similarly arranged on the axial center of the input shaft  4  at an intermediate position of the input shaft  4 , and thereby axles  9   a  and  9   b  on the left and right sides are driven. 
         [0032]    The torque converter  3  includes a case  3   a  coupled with the engine output shaft  2 , a pump  3   b  fixed inside the case  3   a,  and a turbine  3   c  oppositely arranged to the pump  3   b  and driven by the pump  3   b  through operating oil. The torque converter  3  also includes a stator  3   e  that is arranged between the pump  3   b  and the turbine  3   c,  and is supported by the transmission case  6  via a one-way clutch  3   d  to increase engine torque, and a lock-up clutch  3   f  that is provided between the case  3   a  and the turbine  3   c,  and directly connects the engine output shaft  2  and the turbine  3   c  via the case  3   a.  The rotation of the turbine  3   c  is transmitted to the gear-shift mechanism  5  via the input shaft  4 . 
         [0033]    The gear-shift mechanism  5  includes first, second, and third planetary-gear sets  10 ,  20 , and  30 , respectively (hereinafter, simply referred to as “first, second, and third gear sets”). These are arranged inside the transmission case  6  on the opposite side of the torque converter  3  from the output gear  7 , in this order from the torque converter  3 . 
         [0034]    As friction-engaging elements constituting the gear-shift mechanism  5 , a first clutch  40  and a second clutch  50  are arranged on the torque converter side from the output gear  7 . On the opposite side of the torque converter  3  from the output gear  7 , a first brake  60 , a second brake  70 , and a third brake  80  are arranged in this order from the torque converter  3 . A one-way clutch  90  is arranged in parallel with the first brake  60 . 
         [0035]    In this embodiment, each of the first, second, and third gear sets  10 ,  20 , and  30  is a single pinion-type planetary-gear set. The gear set includes sun gears  11 ,  21 , and  31 , a plurality of pinions  12 ,  22 , and  32  mating with the sun gears  11 ,  21 , and  31 , respectively, careers  13 ,  23 , and  33  supporting the pinions  12 ,  22 , and  32 , respectively, and ring gears  14 ,  24 , and  34  mating with the pinions  12 ,  22 , and  32 , respectively. 
         [0036]    The input shaft  4  is coupled with the sun gear  31  of the third gear set  30 . The sun gear  11  of the first gear set  10  and the sun gear  21  of the second gear set  20 , the ring gear  14  of the first gear set  10  and the career  23  of the second gear set  20 , and the ring gear  24  of the second gear set  20  and the career  33  of the third gear set  30  are mutually coupled. The output gear  7  is coupled with the career  13  of the first gear set  10 . 
         [0037]    The sun gear  11  of the second gear set  10  and the sun gear  21  of the second gear set  20  are disconnectably coupled with the input shaft  4  via the first clutch  40 . The career  23  of the second gear set  20  is disconnectably coupled with the input shaft  4  via the second clutch  50 . 
         [0038]    The ring gear  14  of the first gear set  10  and the career  23  of the second gear set  20  are disconnectably coupled with the transmission case  6  via the first brake  60  and the one-way clutch  90  that are arranged in parallel to each other. The ring gear  24  of the second gear set  20  and the career  33  of the third gear set  30  are disconnectably coupled with the transmission case  6  via the second brake  70 . The ring gear  34  of the third gear set  30  is disconnectably coupled with the transmission case  6  via the third brake  80 . 
         [0039]    As described above, according to the gear-shift mechanism  5  of this embodiment, six forward gears and a reverse gear can be achieved by the coupling combination of the first and second clutches  40  and  50  and the first, second, and third brakes  60 ,  70 , and  80 . The relationship between the combinations and the gear positions is shown in the table of  FIG. 2 . 
         [0040]    Here, the first brake  60  is coupled only in the first gear where engine braking is achieved. In the first gear when the engine braking is not generated, the first gear is formed by locking the one-way clutch  90 . 
         [0041]    Next, a control device of the automatic transmission  1  will be explained based on  FIGS. 3-7 . The control device includes an electronic control unit  25  for controlling the gear shift with a control valve mechanism  250 , such as a duty solenoid valve or an ON/OFF valve for hydraulically controlling the friction-engaging elements of the gear-shift mechanism  5 . Hereinafter, terms “front” and “rear,” and “left” and “right” represent front and rear, and left and right of the automobile, respectively, where  FIG. 3  is a front view of the automatic transmission  1 , and  FIG. 4  shows a left side view of the automatic transmission  1 . 
         [0042]    The automatic transmission  1  includes a primary shaft  26  coaxially provided with the engine, and onto which the gear-shift mechanism  5  is provided. The automatic transmission  1  also includes a secondary shaft  27  that is provided rearward and above the primary shaft  26  and is in parallel with the primary shaft  26 . The automatic transmission  1  also includes a differential shaft  28  that is provided rearward and below the primary shaft  26  and is in parallel with the primary shaft  26 . 
         [0043]    A control-valve unit  41  is disposed in a lower portion of the automatic transmission  1  so as to be located below the gear-shift mechanism  5  ( FIG. 1 ). The control-valve unit  41  includes three valve bodies  42 ,  43 , and  44  that are piled in three layers in the vertical direction, and an oil pan  45 . Inside the valve bodies  42 ,  43 , and  44 , a manual valve  35  that moves so as to be interlocked with a range-switching operation of a shift lever of the automobile, control valves for hydraulically controlling the friction-engaging elements, a plurality of accumulators, many oil channels, etc. are incorporated. 
         [0044]    As shown in  FIGS. 3 and 5 , the manual valve  35  is disposed in a front-end portion of the highest valve body  44 , in parallel with the primary shaft  26  so that it moves in the axial direction. A mechanical operation system including rotational shaft  36 , rotary plate  37 , and engaging member  38  for interlocking the shift lever with the manual valve  35  is provided to the manual valve  35 . The engaging member  38  extends downwardly from the rotary plate  37  at a lower end of the rotational shaft  36  of the operation system. The engaging member  38  engages with a disk member  35   a  at a tip end of the valve shaft of the manual valve  35 . Thus, according to a shift position (P, R, N, or D) selected by a driver who operates the shift lever  360 , the manual valve  35  moves in the axial direction via the mechanical operation system. 
         [0045]    As shown in  FIGS. 5-7 , the transmission case  6  surrounding the gear-shift mechanism  5  includes a peripheral wall  51  along an outer perimeter of the rotating members, such as gears and drums. The peripheral wall  51  is opened downwardly at a lower end, and the transmission case  6  also includes an outer wall  52  integrally extending forward from the peripheral wall  51  to be located adjacent to the peripheral wall  51 . A containing space  53  of an upwardly convex shape is formed above the valve body  44 , and it contains the peripheral wall  51  of the transmission case  6 , the outer wall  52 , and the highest valve body  44 . The containing space  53  is disposed forward side of the gear-shift mechanism  5 , and the electronic control unit  25  is disposed inside the containing space  53 . 
         [0046]    The electronic control unit  25  has a control unit case made of a synthetic resin, a printed circuit board (not illustrated) accommodated inside the control unit case, and a computer (not illustrated) mounted on the printed circuit board. An integrated connector  25   a  to which a plurality of signal lines or power lines are connected is integrally provided above and to a left end portion of the electronic control unit  25 . 
         [0047]    The electronic control unit  25  includes a sensor mounting portion  25 A integrally formed therewith so that it continues to the right from the rear and right end portion of the electronic control unit  25 . The sensor mounting portion  25 A is also integrally formed with a position detecting sensor  61  for detecting a moved position of the manual valve  35 , and rotation sensors  62 ,  63 , and  64  for detecting rotation speeds of the rotating members of the gear-shift mechanism  5 . The rotation sensors  62 ,  63 , and  64  are integrally formed with the electronic control unit  25 . The rotation sensors  62 ,  63 , and  64  are formed so as to be inclined rearward from the electronic control unit  25 . The position detecting sensor  61  and the rotation sensors  62 ,  63 , and  64  are connected to the electronic control unit  25  via harnesses. 
         [0048]    The position detecting sensor  61  is a potentiometer-type sensor. The position detecting sensor  61  includes a guide portion  61   a  that is a level, rectangular groove in the left-and-right direction, and a resistance body  61   b  provided in an intermediate portion of the guide portion  61   a.  The position detecting sensor  61  also includes a movable member  61   c  that is movable to the left and right along the guide portion  61   a,  and an engaging member  61   d  attached to the movable member  61   c  for engaging with the disk member  35   a  of the manual valve  35 . 
         [0049]    When the manual valve  35  is switched by the operation of the shift lever  360 , because the movable member  61   c  also integrally moves to a position corresponding to the shift position via the engaging member  61   d,  the moved position may be detected based on the change in a value of electrical resistance. 
         [0050]    As shown in  FIGS. 1 ,  5 , and  6 , the rotation sensor  62  of this embodiment is an electromagnetic pickup sensor that detects a rotation of the input shaft  4  (i.e., turbine shaft). The rotation sensor  63  is an electromagnetic pickup sensor that detects a rotation of the valve member of the first clutch  40  (i.e., rotation of the first and second sun gears  11  and  21 ). The rotation sensor  64  is an electromagnetic pickup sensor that detects a rotation of the output gear  7 . As shown in  FIG. 1 , the rotation sensors  62 ,  63 , and  64  and the electronic control unit  25  are disposed in this order from the torque converter  3 . 
         [0051]    Next, operations and effects of the control device of the automatic transmission  1  will be explained. 
         [0052]    As described above, the electronic control unit  25  for controlling the gear shift  360  is provided inside the containing space  53  that is formed with the peripheral wall  51  of the transmission case  6 , the outer wall  52  of the transmission case  6  is provided adjacent to the peripheral wall  51  and the valve body  44 . Further, forward and immediately below the gear-shift mechanism  5 , there may be a dead space inside the outer wall  52  of the transmission case  6 . The dead space may be effectively used by arranging the electronic control unit  25  at the dead space, which is departed from the gear-shift mechanism  5 . Thus, the electronic control unit  25  may be arranged within an internal space of the transmission case  6  and at a position where the electronic control unit  25  will not be damaged by hot oil dispersed from the gear-shift mechanism  5 , thereby maintaining the durability of the electronic control unit  25 . 
         [0053]    The present invention may be applied to a FF-three-shaft-type automatic transmission that includes the primary shaft  26 , the secondary shaft  27 , and the differential shaft  28  to form the containing space  53  at a position forward side of the gear-shift mechanism  5 . Thus, the electronic control unit  25  may be certainly arranged within the containing space  53 . 
         [0054]    In the above embodiment, because the electronic control unit  25  is arranged on the top portion of the valve body  44 , lengths of the plurality of harnesses that connects the electronic control unit  25  with the solenoid  250  of the control valves may be shortened, thereby reducing the manufacturing cost. Further, in the above embodiment, because the rotation sensors  62 ,  63 , and  64  are integrated with the electronic control unit  25 , harnesses or couplers for connecting the rotation sensors  62 ,  63 , and  64  with the electronic control unit  25  may also be reduced in number. Further, in the above embodiment, because the rotation sensors  62 ,  63 , and  64  are inclined rearwardly from the electronic control unit  25 , the electronic control unit  25  integrated with the rotation sensor may be arranged at a higher position, thereby reducing the damages caused due to the scattered hot oil. 
         [0055]    Further, in the above embodiment, because the automatic transmission  1  includes the torque converter  3 , and because the rotation sensors  62 ,  63 , and  64  and the electronic control unit  25  are arranged in this order from the torque converter  3 , the electronic control unit  25  may be arranged at a position distant from the torque converter  3  that is easy to increase in temperature. 
         [0056]    Further, in the above embodiment, the position detecting sensor  61  for detecting the moved position of the manual valve  35  is provided, and the position detecting sensor  61  is integrated with the electronic control unit  25 . Thus, the harnesses and couplers connecting the position detecting sensor  61  with the electronic control unit  25  may be reduced in number, thereby arranging the position detecting sensor  61  compactly. 
         [0057]    Further, in the above embodiment, the manual valve  35  is disposed in parallel with the primary shaft  26  to move in the axial direction. Thus, it may be possible to compactly arrange the manual valve  35 . 
         [0058]    Further, in the above embodiment, the manual valve  35  is provided to the highest valve body  44  among the plurality of valve bodies  42 ,  43 , and  44 . The electronic control unit  25  is arranged on the top portion of the highest valve body  44 . Thus, the electronic control unit  25  may be arranged at a higher position to reduce the thermal damage. 
         [0059]    Next, an example in which the above embodiment is partially changed will be explained. 
         [0060]    In the above embodiment, the present invention is applied to the automatic transmission of the automobile with a side-mounted engine. It should be appreciated by those skilled in the art that the present invention may also be applied to automatic transmissions other than those of the automobile with the side-mounted engine. 
         [0061]    In the above embodiment, the control-valve unit of the automatic transmission is provided with three valve bodies piled in three layers. It should be appreciated by those skilled in the art that the valve bodies may be two instead of three, and may also be one. 
         [0062]    In addition, a person skilled in the art may suitably modify the embodiment, and the modified embodiment may also be included in the scope of the present invention. 
         [0063]    It should be understood that the embodiments herein are illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.