Patent Publication Number: US-2007117665-A1

Title: Automatic transmission

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to an automatic transmission, and more particularly to an arrangement of an oil pump and a hydraulic control valve in an automatic transmission.  
      Japanese Patent Application First Publication No. 2004-197884 indicates an arrangement of an oil pump and a hydraulic control valve in a belt-drive automatic transmission of a vehicle.  FIGS. 4 and 5  show the arrangement as indicated in this related art. As illustrated in  FIGS. 4 and 5 , belt-drive automatic transmission  50  in which a rotation from a power source is inputted to input shaft  52  via torque converter  51  and then transmitted to primary pulley  53  connected to input shaft  52 . The rotation is transmitted from primary pulley  53  to secondary pulley  55  through V-belt  54  at a variably controlled gear ratio and outputted to output shaft  56 . The rotation outputted is transmitted to driving wheels through drive gear  57  connected to output shaft  56 , driven gear  58  connected to drive gear  57 , counter shaft  59  connected to driven gear  58 , final drive gear set  60 , differential gear  61  and differential shaft  62 . As illustrated in  FIG. 4 , input shaft  52 , output shaft  56 , counter shaft  59  and differential shaft  62  are arranged such that axes thereof are parallel to width direction Z of the vehicle, and input shaft  52 , namely, torque converter  51  and primary pulley  53 , are located forward of output shaft  56 , counter shaft  59  and differential shaft  62 .  
      Belt-drive automatic transmission  50  further includes oil pump  63  for supplying a hydraulic pressure of a working oil which is required to vary a V-shaped groove between pulley halves of respective primary and secondary pulleys  53  and  55  in order to realize a desired gear ratio. Belt-drive automatic transmission  50  further includes hydraulic control valve  64  for producing a hydraulic pressure corresponding to the desired gear ratio which is to be applied to primary and secondary pulleys  53  and  55 . As shown in  FIG. 4 , oil pump  63  is located below input shaft  52  and forward of the axes of output shaft  56  and differential shaft  62 , namely, on the right side of a line extending through the axes of output shaft  56  and differential shaft  62 . Hydraulic control valve  64  is disposed at a front end of transmission case  65  in fore-and-aft direction X of the vehicle and forwardly projects from the front end of transmission case  65 . Meanwhile, reference symbol Y in  FIG. 4  denotes a height direction of the vehicle.  
     SUMMARY OF THE INVENTION  
      However, belt-drive automatic transmission  50  is increased in size in fore-and-aft direction X of the vehicle due to the arrangement of hydraulic control valve  64  at a front end of transmission case  65 . Further, oil pump  63  and hydraulic control valve  64  are disposed relatively distant from each other. The arrangement of oil pump  63  and hydraulic control valve  64  causes increase in length of an oil passage which extends from oil pump  63  to hydraulic control valve  64 . This leads to increase in flow resistance of the oil passage and also causes difficulty in layout of the oil passage.  
      An object of the present invention is to provide an automatic transmission which is downsized and simplified in layout of an oil passage extending from an oil pump to a hydraulic control valve and allows reduction in flow resistance of the oil passage.  
      In one aspect of the present invention, there is provided an automatic transmission coupled with a power source in a vehicle, the automatic transmission comprising:  
      a transmission case;  
      a torque converter disposed within the transmission case, the torque converter being adapted to be connected with the power source,  
      a power transmission mechanism disposed within the transmission case, the power transmission mechanism including an input shaft connected with the torque converter, an output shaft connected with the input shaft, a counter shaft connected with the output shaft and a differential shaft connected with the counter shaft,  
      an oil pump disposed within the transmission case, the oil pump being adapted to be driven by the power source and supply a working oil to the power transmission mechanism;  
      a hydraulic control valve which controls a hydraulic pressure corresponding to a gear ratio at which the power transmission mechanism is operated; and  
      an oil pan which accommodates the hydraulic control valve and stores the working oil,  
      wherein the input shaft, the output shaft, the countershaft and the differential shaft of the power transmission mechanism are disposed parallel to a width direction of the vehicle and perpendicular to in a fore-and-aft direction of the vehicle, and the input shaft is disposed forward of the output shaft, the countershaft and the differential shaft in the fore-and-aft direction of the vehicle;  
      the oil pan and the hydraulic control valve accommodated in the oil pan are disposed below the input shaft in a height direction of the vehicle; and  
      the oil pump is disposed immediately above the hydraulic control valve and lower than an axis of the input shaft in the height direction of the vehicle and arranged in a space between the torque converter and the power transmission mechanism within the transmission case. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a continuously variable belt drive transmission of an embodiment of the present invention, when viewed in a width direction of a vehicle.  
       FIG. 2  is a sectional view of the continuously variable belt drive transmission shown in  FIG. 1 , taken along line  2 - 2  of  FIG. 1 .  
       FIG. 3  is an enlarged view of the continuously variable belt drive transmission shown in  FIG. 1 , showing an oil pump and the vicinity of the oil pump.  
       FIG. 4  is a side view of a continuously variable belt drive transmission of a related art.  
       FIG. 5  is a sectional view of the continuously variable belt drive transmission shown in  FIG. 4 , taken along line  5 - 5  of  FIG. 4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In the followings, an embodiment of the present invention will be described with reference to the accompanying drawings.  FIGS. 1-3  illustrate a continuously variable belt drive transmission (hereinafter referred to as a belt drive CVT) for a vehicle, according to the embodiment of the present invention. As illustrated in  FIG. 2 , belt drive CVT  10  includes transmission case  11 , torque converter  15  and power transmission mechanism  32  which are disposed within transmission case  11 . Power transmission mechanism  32  includes primary pulley  12 , secondary pulley  13  which are connected with each other through V-belt  14 , and forward and reverse changeover mechanism  17 . Primary pulley  12  and torque converter  15  have a common axis which extends through input shaft  16 . Secondary pulley  13  is directly disposed on output shaft  18  parallel to input shaft  16 . V-belt  14  is engaged in V-shaped grooves of primary and secondary pulleys  12  and  13  which are aligned with each other in the axial direction of primary and secondary pulleys  12  and  13 . Rotation from an engine, not shown, as a power source is inputted to input shaft  16  via torque converter  15 . The rotation is transmitted to primary pulley  12  through forward-rearward changeover mechanism  17 . The rotation is transmitted from primary pulley  12  to secondary pulley  13  through V-belt  14 . The rotation of secondary pulley  13  is transmitted to output shaft  18  connected to secondary pulley  13 , drive gear  19  connected to output shaft  18 , driven gear  20  connected to drive gear  19 , and counter shaft  21  connected to driven gear  20 . The rotation of counter shaft  21  is transmitted to driving wheels, not shown, through final drive gear set  22 , differential gear unit  23  and differential shaft  24  of differential gear unit  23 .  
      Referring to  FIG. 1 , there is shown an arrangement of input shaft  16 , output shaft  18 , counter shaft  21  and differential shaft  24 . Input shaft  16 , output shaft  18 , counter shaft  21  and differential shaft  24  are arranged such that axes thereof are parallel to width direction Z of the vehicle and perpendicular to fore-and-aft direction X of the vehicle. Further, as illustrated in  FIG. 2 , input shaft  16  is arranged forward of output shaft  18 , counter shaft  21  and differential shaft  24 . That is, torque converter  15  and primary pulley  12  are located forward of output shaft  18 , counter shaft  21  and differential shaft  24 . The axes of output shaft  18 , counter shaft  21  and differential shaft  24  are located on substantially the same line which extends in height direction Y of the vehicle as indicated by a broken line in  FIG. 1 . With this arrangement of output shaft  18 , counter shaft  21  and differential shaft  24 , belt drive CVT  10  can be reduced in size in fore-and-aft direction X of the vehicle. This serves for reducing a space occupied by belt drive CVT  10  within an engine room of the vehicle.  
      As illustrated in  FIG. 2 , primary pulley  12  of power transmission mechanism  32  includes stationary disk  12   a  which rotates integrally with input shaft  16  and moveable disk  12   b  which is opposed to stationary disk  12   a  in an axial direction of input shaft  16 . Stationary disk  12   a  and moveable disk  12   b  cooperate with each other to define the V-shaped groove therebetween. Movable disk  12   b  is displaceable in the axial direction of input shaft  16  by thrust which is produced by applying a primary pulley oil pressure to primary pulley chamber  12   c  of primary pulley  12 . Similarly, secondary pulley  13  of power transmission mechanism  32  includes stationary disk  13   a  which rotates integrally with output shaft  18  and moveable disk  13   b  which is opposed to stationary disk  13   a  in an axial direction of output shaft  18 . Stationary disk  13   a  and moveable disk  13   b  cooperate with each other to define the V-shaped groove therebetween. Movable disk  13   b  is displaceable in the axial direction of output shaft  18  by thrust which is produced by applying a secondary pulley oil pressure to secondary pulley chamber  13   c  of secondary pulley  13 . V-belt  14  engaged with the V-shaped grooves of respective primary and secondary pulleys  12  and  13  transmits the rotation of input shaft  16  to output shaft  18 .  
      Gear ratio control of power transmission mechanism  32  is conducted by continuously varying the effective contact radius of V-belt  14  at the contact position of each of primary and secondary pulleys  12  and  13  by changing a width of the V-shaped grooves of respective primary and secondary pulleys  12  and  13 . A target gear ratio is achieved by the gear ratio control.  
      As illustrated in  FIG. 1 , hydraulic control valve  25  which controls a hydraulic pressure corresponding to a gear ratio at which power transmission mechanism  32  is operated. Namely, hydraulic control valve  25  for controlling the primary pulley oil pressure and the secondary pulley oil pressure is disposed within oil pan  26  as indicated by a broken line. Hydraulic-control valve  25  produces the primary pulley oil pressure and the secondary pulley oil pressure on the basis of a command signal from a control unit, not shown. Oil pan  26  is mounted to a lower portion of transmission case  11  and stores the working oil.  
      Referring to  FIG. 3 , there is shown oil pump  27  supplying the working oil which acts as a transmission medium of the primary pulley oil pressure and the secondary pulley oil pressure and lubricates components of belt drive CVT  10 . Oil pump  27  is accommodated in an oil pump receptacle portion of transmission case  11  which is forwardly projected in fore-and-aft direction X of the vehicle. Oil pump  27  is driven by the engine via drive sprocket  28 , driven sprocket  29  and chain  30  which is would on drive and driven sprockets  28  and  29 . Drive sprocket  28  is mounted to torque converter  15 . Driven sprocket  29  is directly coupled to oil pump  27 . Driven sprocket  29  has a diameter smaller than that of drive sprocket  28 . The rotation outputted from the engine is transmitted to oil pump  27  through drive sprocket  28 , driven sprocket  29  and chain  30 . Oil pump  27  sucks and pressurizes the working oil within oil pan  26  and supplies the pressurized working oil to hydraulic control valve  25 . Owing to the smaller size of driven sprocket  29 , oil pump  27  is allowed to produce a high oil pressure with the engine rotation. The pressure of the working oil supplied to hydraulic control valve  25  is regulated on the basis of a command signal from the control unit. The working oil regulated is transmitted from hydraulic control valve  25  to primary and secondary pulleys  12  and  13  and clutches and brakes of forward-rearward changeover mechanism  17  for actuation thereof. The working oil regulated is also transmitted to the components of belt drive CVT  10  for lubrication thereof.  
      Referring back to  FIG. 1 , hydraulic control valve  25 , oil pan  26  which accommodates hydraulic control valve  25 , and oil pump  27  are located in a position lower than the axis of input shaft  16  in height direction Y of the vehicle and are arranged close to each other. Oil pan  26  and hydraulic control valve  25  accommodated in oil pan  26  are disposed below input shaft  16  in height direction Y of the vehicle. Oil pump  27  is disposed immediately above oil pan  26  and hydraulic control valve  25  accommodated in oil pan  26 .  
      With this arrangement of hydraulic control valve  25 , oil pan  26  and oil pump  27 , it is possible to shorten an oil passage via which the working oil is sucked from oil pan  26  by oil pump  27  and an oil passage via which the working oil is supplied from oil pump  27  to hydraulic control valve  25 . A flow resistance of pipes which define the oil passages can be reduced, whereby the layout of the oil passages and the construction thereof can be simplified.  
      Further, with this arrangement of hydraulic control valve  25 , oil pan  26  and oil pump  27 , hydraulic control valve  25  can be always supplied with a certain amount of the working oil. Even when the engine is temporarily stopped, the working oil hardly flows out from hydraulic control valve  25 . When the engine is restarted, a suitable oil pressure for conducting the gear ratio control can be produced and the lubrication of belt drive CVT  10  can be quickly established.  
      Oil pump  27  is arranged forward of input shaft  16  in fore-and-aft direction X of the vehicle. With this arrangement of oil pump  27 , oil pump  27  can be prevented from interfering with other parts upon assembling belt drive CVT  10 , specifically, upon mounting oil pump  27  into transmission case  11 . The mounting work can be facilitated. Further, as illustrated on the right side of  FIG. 1 , transmission case  11  includes oil pump enclosing portion  11   a  which accommodates oil pump  27 . Oil pump enclosing portion  11   a  is located on the front side of transmission case  11  in fore-and-aft direction X of the vehicle and projected forward to form a curve as shown in  FIG. 1 . An outer-most periphery of oil pump enclosing portion  11   a  and front end portion  26   a  of oil pan  26  are located in substantially alignment with in fore-and-aft direction X of the vehicle. That is, oil pump  27 , oil pan  26  and hydraulic control valve  25  within oil pan  26  are arranged so as to project forward in fore-and-aft direction X of the vehicle to a lesser extent. With this arrangement of oil pump  27 , oil pan  26  and hydraulic control valve  25 , the length of belt drive CVT in fore-and-aft direction X of the vehicle can be reduced to thereby realize a downsized belt drive CVT  10 , as compared with the belt drive CVT of the related art as shown in  FIG. 4 .  
      Oil pump  27  is disposed between torque converter and power transmission mechanism  32  as shown in  FIG. 2 . Further, oil pump  27  is located in a position adjacent to forward-rearward changeover mechanism  17  which has a circular shape in section and oil pan  26  and hydraulic control valve  25  which have a rectangular shape in section. That is, oil pump  27  is arranged in a dead space between torque converter  15  and power transmission mechanism  32  within transmission case  11 . Thus, the dead space in transmission case  11  can be effectively utilized. It is not necessary to provide an additional installation space for accommodating oil pump  27 . Oil pump  27  can be arranged in the dead space so as to reduce an amount of the projection in the forward direction of the vehicle to a minimum. This serves for downsizing belt drive CVT  10 .  
      Oil pan  26  is arranged such that bottom  26   b  thereof is located in either of a position substantially aligned with a lower-most end portion of transmission case  11  in height direction Y of the vehicle and a position higher than the lower-most end portion of transmission case  11  in height direction Y thereof. Namely, bottom  26   b  of oil pan  26  is located at a height or level with respect to a road surface which is substantially the same as the lower-most end portion of transmission case  11  or higher than the lower-most end portion of transmission case  11 . Specifically, the lower-most end portion of transmission case  11  is set at the height with respect to a road surface at which the lower-most end portion can be prevented from contacting with projections on the road surface, for instance, a curb of the road, a car stop, a rockfall and the like. Accordingly, in belt drive CVT  10  of this embodiment, a mount height of oil pan  26 , that is, the height of oil pan  26  with respect to the road surface is adjusted to substantially the same as the height of the lower-most end portion of transmission case  11  or to a height higher than the lower-most end portion of transmission case  11 . With this construction, the bottom of oil pan  26  can be prevented from being contacted with the projections on the road surface during traveling of the vehicle. This serves for reducing a possibility that oil pan  26  and hydraulic control valve  25  within oil pan  26  suffer from damage which would be caused due to the contact between the bottom thereof and the projections during traveling of the vehicle.  
      As is understood from the above explanation, the automatic transmission of the present invention can be downsized, especially, in the fore-and-aft direction of the vehicle. This allows to reduce an installation space of the automatic transmission in an engine room of the vehicle. Accordingly, the automatic transmission of the present invention can be applied to a small-sized vehicle, such as a light car, having a narrow engine room which is relatively small in the fore-and-aft direction of the vehicle. Further, owing to the compact layout of the oil pump, the hydraulic control valve and the oil pan, it is possible to reduce flow resistance of the oil passages extending between the oil pump and the oil pan and between the oil pump and the hydraulic control valve and simplify the layout and construction of the oil passages. Further, even when the power source is restarted, an oil pressure for the gear ratio control and the lubrication can be quickly and suitably attained.  
      Furthermore, the automatic transmission of the present invention is not limited to the belt drive CVT of the above embodiment and can be applied to other types of the automatic transmission such as a gear type (step type) automatic transmission and a toroidal automatic transmission.  
      This application is based on a prior Japanese Patent Application No. 2005-336661 filed on Nov. 22, 2005. The entire contents of the Japanese Patent Application No. 2005-336661 is hereby incorporated by reference.  
      Although the invention has been described above by reference to the embodiment of the invention, the invention is not limited to the embodiment described above. Modifications and variations of the embodiment described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims.