Abstract:
A transmission for a vehicle has an output shaft, a main shaft and a countershaft. The main shaft is arranged to receive rotary power and the countershaft is arranged in parallel to the main shaft. A plurality of meshed gear pairs are formed main gears and counter gears on the two shafts. A plurality of clutch devices are arranged to select a gear pair that will transmit torque to the output shaft. A reverse drive is created by a main reverse gear on the main shaft, a counter reverse gear on the counter shaft and a chain wrapping the main reverse gear and the counter reverse gear. A reverse clutch device is arranged to selectively fix one of the main and counter reverse gears to its respective main or counter shaft for rotation.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates in general to transmissions and in particular to transmissions for small vehicles. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates particularly to transmissions for smaller, fuel efficient vehicles, such as utility terrain vehicles (UTV), on highway micro-cars, and mini-cars and trucks. It is important in these vehicles that smaller vehicles minimize weight and bulk for operating components such as transmissions. 
         [0003]    U.S. Pat. No. 6,725,962 discloses a transmission for an all terrain vehicle (ATV). This transmission utilizes three shafts to transmit power from a continuously variable transmission (CVT) to vehicle wheels. 
         [0004]    The inventors have recognized that it would be advantageous to provide a transmission for a vehicle having a compact design and that can accomplish gear selection with two shafts, including a reverse gear. The inventors have recognized that it would be advantageous to provide an automatic transmission for a small vehicle that is compact, weight efficient and reliable. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides a transmission for a vehicle that includes a geartrain that includes a main shaft for receiving rotary power from an engine output and a countershaft arranged in parallel to the main shaft. The main shaft carries a plurality of main forward gears. The countershaft carries a plurality of counter forward gears. A plurality of forward gear pairs are formed by each of the main forward gears being arranged to form one gear pair with one of the counter forward gears, the gear pairs being in constant mesh. A reverse main gear drives a reverse counter gear via a chain or belt forming a reverse gear pair. An output pulley is rotatably mounted on the main shaft. A plurality of clutch devices are arranged to select a gear pair from the plurality of gear pairs that will transmit torque to the output pulley. 
         [0006]    The invention provides an automatic transmission for a vehicle that includes a torque converter. The torque converter includes a torque converter housing, a torque converter input pulley arranged to receive rotary power from the engine output and a torque converter output shaft for transmitting rotary power to the geartrain. The torque converter includes fluid coupling elements arranged within the housing to transmit torque between the torque converter input pulley and the torque converter output shaft. 
         [0007]    According to one preferred embodiment, at least one clutch device comprises a clutch plate or drum fixed on the main shaft, and at least one clutch friction disk arranged between the clutch plate and one gear of the select gear pairs. The friction disk is selectively engageable to the clutch plate and to the one gear to transmit torque between the clutch plate and the one gear. 
         [0008]    According to another preferred embodiment, at least one clutch device comprises a clutch plate fixed on the countershaft, and at least one clutch friction disk arranged between the clutch plate and one gear of the select gear pair. The friction disk is selectively engageable to the clutch plate and to the one gear to transmit torque between the clutch plate and the one gear. 
         [0009]    The geartrain can be a four speed geartrain, wherein fourth gear can be a direct drive located furthest from the torque converter. A first gear pair can be located next to the fourth gear between the fourth gear and the torque converter. A second gear pair can be located next to the first gear pair and between the first gear pair and the torque converter. A third gear pair can be located next to the second gear pair and between the second gear pair and the torque converter. A reverse gear pair can be located next to the third gear pair and between the third gear pair and the torque converter. 
         [0010]    According to the preferred embodiment, the torque converter input pulley is located between the torque converter housing and the reverse gear pair. 
         [0011]    According to a preferred embodiment at least some of the clutch devices each comprise one clutch plate fixed to the main shaft or the counter shaft with engageable opposite sides. The clutch plate can be arranged between alternately selectable gear pairs, and at least one friction disk is arranged between each of the selectable gear pairs and one engageable opposite side of the clutch plate. Each friction disk is selectively actuatable to engage one gear of the selectable gear pair to the clutch plate to transmit torque between the clutch plate and the selectable gear pair to transmit torque to the output pulley. 
         [0012]    The transmission assembly of the present invention provides a compact, relatively simple automatic transmission that is particularly adapted for use on small vehicles. 
         [0013]    The transmission assembly of the present invention provides a two shaft transmission that provides a reverse gear and multiple forward gears. 
         [0014]    Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic plan view of a drivetrain of vehicle incorporating the transmission of the present invention; 
           [0016]      FIG. 2  is a schematic legend diagram for understanding the following schematic diagrams; 
           [0017]      FIG. 3  is a schematic plan view of the transmission shown in  FIG. 1  with the transmission shown in a first gear mode of operation; 
           [0018]      FIG. 4  is a schematic plan view of the transmission of  FIG. 3  with the transmission shown in a second gear mode of operation; 
           [0019]      FIG. 5  is a schematic plan view of the transmission of  FIG. 3  with the transmission shown in a third gear mode of operation; 
           [0020]      FIG. 6  is a schematic plan view of the transmission of  FIG. 3  with the transmission shown in a fourth gear mode of operation; 
           [0021]      FIG. 7  is a schematic plan view of the transmission of  FIG. 3  with the transmission shown in a reverse gear mode of operation; and 
           [0022]      FIG. 8  is a schematic plan view of the transmission of  FIG. 3  showing a control scheme. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0024]      FIG. 1  illustrates a vehicle  20  having a drivetrain  26 . The drive train  26  includes an engine  34 , a transmission assembly  38  and a rear wheel  30 . The engine  34  transmits rotary power via its crankshaft to an engine output shaft  46 . The engine output shaft  46  is connected to an engine drive sprocket  48 . 
         [0025]    The transmission assembly  38  includes a torque converter  52  that has a torque converter drive sprocket  54 . 
         [0026]    A primary drive chain  56  is wrapped around the engine drive sprocket  48  and the torque converter drive sprocket  54 . The transmission assembly  38  includes a transmission output pulley  62 . A rear drive pulley  66  is operatively connected to the rear wheel  30  to rotate the rear wheel  30 . A secondary drive chain  68  is wrapped around the output pulley  62  and the rear drive pulley  66 . 
         [0027]    The terms “sprocket” and “pulley” denote elements having outside features that are engageable by either a chain or a belt, to be rotated thereby. A sprocket and a pulley can function in like fashion, and accordingly the terms are used interchangeably herein. 
         [0028]      FIG. 2  illustrates a legend for the symbols used in  FIGS. 3-8 . The symbols are defined below. 
         [0029]    GF=gear fixed to a shaft to rotate therewith 
         [0030]    S=shaft 
         [0031]    CDN=disengaged clutch friction disc 
         [0032]    CP=clutch plate fixed to a shaft 
         [0033]    CDE=clutch friction disc engaged to a clutch plate and a gear 
         [0034]    GR=gear rotatable on a shaft 
         [0035]    CH=chain or belt 
         [0036]    B=bearing 
         [0037]    C=casing or housing 
         [0038]      FIG. 3  illustrates the transmission assembly  38  in first gear. The torque converter  52  includes a torque converter housing  72 . Within the housing  72  are a driving rotary element  74  and a driven rotary element  76 . The torque converter is shown in a simplistic way. For example, a stator can also be included within the housing between the driving rotary element  74  and the driven rotary element  76 . Torque converters are well known and are described for example in U.S. Pat. Nos.: 4,070,925; 5,862,717; 2,897,690; 2,449, 608; 6,655,226; 6,390,262; and 6,805,026, all herein incorporated by reference. The torque converter housing  72 , the driving rotary element  74 , and the input pulley  54  are all fixed to rotate together. The driven rotary element  76  is fixed to a main shaft  86  of the transmission assembly  38 . The torque converter housing  72  is journaled on the main shaft  86  or on a suitable extension thereof, by bearings and oil seals (not shown). 
         [0039]    The main shaft  86  penetrates into a transmission casing  87  of the transmission assembly  38 . The main shaft  86  receives rotary power from the torque converter  52  via a fluid coupling between the driving rotary element  74  and the driven rotary element  76 , by rotation of the torque converter components  54 ,  72 ,  74 . The main shaft  86  transmits rotary power to clutch plates  92 ,  96  that are fixed on the main shaft  86  to rotate therewith. The clutch plates  92 ,  96  can be keyed or splined to the shaft  86  or otherwise fixedly fastened to the shaft  86 . The clutch plates include clutch engaging faces  92   a,    96   a,  and  96   b.    
         [0040]    Preferably, the clutch assemblies are multiple disk wet clutches. The clutch plates are shown schematically as flat plates but are preferably of a drum configuration having a plurality of friction plates that are interleaved with friction disks of the clutch friction disk assembly such as shown and described in U.S. Pat. Nos. 4,623,055; 5,103,953; 4,131,185 or 3,266,608, all incorporated by reference. 
         [0041]    A first main drive gear  102 , a fourth main drive gear  104  and a reverse main drive gear  106  are mounted axially on the main shaft  86  but are free to rotate on the main shaft, i.e., are relatively rotatable with respect to the main shaft  86 . The fourth main drive gear  104  is fixed to an output shaft  105  that mounts the output pulley  62 . 
         [0042]    A second main drive gear  110  and a third main drive gear  112  are fixedly mounted to the main shaft  86 , i. e., there is no relative rotation between the gears  110 ,  112  and the main shaft  86 . The gears  110 ,  112  can be keyed or splined to the main shaft  86  or otherwise fixedly fastened to the main shaft  86 . 
         [0043]    Clutch friction disks  116  are mounted on the main shaft  86  between the reverse drive gear  106  and the clutch plate  92 . Clutch friction disks  118  are mounted on the main shaft  86  between the clutch plate  96  and the fourth drive gear  104 . Clutch friction disks  120  are mounted on the main shaft  86  between the clutch plate  96  and the first drive gear  102 . According to one embodiment, the clutch friction disks  116 ,  118 ,  120  are free to rotate on the main shaft  86 , i.e., are relatively rotatable with respect to the main shaft  86 . 
         [0044]    A countershaft  132  is mounted within the transmission casing  87 , parallel to the main shaft  86 . The counter shaft  132  transmits rotary power to clutch plate  133  that is fixed on the counter shaft  132  to rotate therewith. The clutch plate  133  can be keyed or splined to the shaft  132  or otherwise fixedly fastened to the shaft  132 . The clutch plate  133  includes clutch engaging faces  133   a,    133   b.    
         [0045]    A drive counter gear  134 , a first counter gear  136 , and a reverse counter gear  138  are fixedly mounted to the counter shaft  132 , i. e., there is no relative rotation between the gears  134 ,  136 ,  138  and the countershaft  132 . The gears  134 ,  136 ,  138  can be keyed or splined to the countershaft  132  or otherwise fixedly fastened to the countershaft  132 . The drive counter gear  134  is en mesh with the fourth main drive gear  104 . The first counter gear  136  is en mesh with the first main drive gear  102 . The reverse counter gear  138  is chain driven by the reverse main drive gear  106 , via a chain  139 ; the gears  106 ,  138  are not en mesh, i.e. the gears  106 ,  138  rotate in the same direction. 
         [0046]    A second counter gear  140  and a third counter gear  142  are mounted axially on the counter shaft  132  but are free to rotate on the counter shaft, i.e., are relatively rotatable with respect to the counter shaft  132 . The second counter gear  140  is en mesh with the second main drive gear  110 . The third counter gear  142  is en mesh with the third main drive gear  112 . 
         [0047]    Clutch friction disks  150  are mounted on the counter shaft  132  between the second counter gear  140  and the clutch plate face  133   a.  Clutch friction disks  152  are mounted on the counter shaft  132  between the third counter gear  142  and the clutch plate face  133   b.  According to one embodiment, the clutch friction disks  150 ,  152  are free to rotate on the counter shaft  132 , i.e., are relatively rotatable with respect to the counter shaft  132 . 
         [0048]    The gears  102 ,  104 ,  106 ,  110 ,  112 ,  134 ,  136 ,  1138 ,  140 ,  142  all have outer circumferential teeth. The gear pair  102 ,  136  forms first gear; the gear pair  110 ,  140  forms second gear; the gear pair  112 ,  142  forms third gear and the fourth main drive gear  104  in effect forms fourth gear, i.e. a direct drive from the main shaft  86 . 
         [0049]      FIG. 3  illustrates the operation of the transmission in first gear mode. The torque converter  52  is turned via the input pulley  54 . A fluid coupling within the torque converter turns the main shaft  86 . The main shaft  86  turns the clutch plate  96  which turns first main drive gear  102  via the clutch friction disks  120  which are selected by a controller to be engaged to the clutch plate  96 , particularly the face  96   a.  First main drive gear  102  turns the corresponding first counter gear  136 , which turns the countershaft  132 , which turns the counter drive gear  134 , which turns the fourth main drive gear  104  that is fixed to the output shaft  105  and the pulley  62 . The output pulley  62  is turned, which turns the rear wheel  30  via the drive sprocket  66  and the secondary chain  68 . 
         [0050]      FIG. 4  illustrates the operation of the transmission in second gear mode. The torque converter  52  is turned via the input pulley  54 . A fluid coupling within the torque converter turns the main shaft  86 . The main shaft  86  turns the second main drive gear  110 , which turns the second counter gear  140 . The clutch control has engaged the clutch discs  150  to cause the second counter gear  140  to turn the clutch plate  133  at the same speed as the second counter gear  140 . The clutch plate  133  turns the counter shaft  132  which turns the counter drive gear  134  which turns the fourth main drive gear  104  that is fixed to the output pulley  62 . The output pulley  62  is turned, which turns the rear wheel  30  via the drive sprocket  66  and the secondary chain  68 . 
         [0051]      FIG. 5  illustrates the operation of the transmission in third gear mode. The torque converter  52  is turned via the input pulley  54 . A fluid coupling within the torque converter turns the main shaft  86 . The main shaft  86  turns the third main drive gear  112 , which turns the third counter gear  142 . The clutch control has engaged the clutch discs  152  to cause the third counter gear  142  to turn the clutch plate  133  at the same speed as the third counter gear  142 . The clutch plate  133  turns the counter shaft  132  which turns the counter drive gear  134  which turns the fourth main drive gear  104  that is fixed to the output pulley  62 . The output pulley  62  is turned, which turns the rear wheel  30  via the drive sprocket  66  and the secondary chain  68 . 
         [0052]      FIG. 6  illustrates the operation of the transmission in fourth gear mode. The torque converter  52  is turned via the input pulley  54 . A fluid coupling within the torque converter turns the main shaft  86 . The main shaft  86  turns the clutch plate  96 . The control actuates clutch discs  118  to cause the clutch plate  96  to turn the fourth main drive gear  104  at the same speed as the clutch plate  96 . The fourth gear  104  is fixed to the output pulley  62 . The output pulley  62  is turned, which turns the rear wheel  30  via the drive sprocket  66  and the secondary chain  68 . 
         [0053]      FIG. 7  illustrates the operation of the transmission in reverse gear mode. The torque converter  52  is turned via the input pulley  54 . A fluid coupling within the torque converter turns the main shaft  86 . The main shaft  86  turns the clutch plate  92 . The control actuates clutch discs  116  to cause the clutch plate  92  to turn the reverse main drive gear  106  at the same speed as the clutch plate  92 . The reverse main drive gear  106  drives the reverse counter gear  138  in the same direction via the chain  139 . The reverse counter gear  138  turns the counter shaft  132  which turns the counter drive gear  134 . The counter drive gear  134  turns the fourth main drive gear  104  in an opposite direction. The fourth main drive gear  104  is fixed to the output pulley  62  via the output shaft  105 . The output pulley  62  is turned, which turns the rear wheel  30  via the drive sprocket  66  and the secondary chain  68 . 
         [0054]      FIG. 8  illustrates a control system  300  of the invention. A controller  302  is in signal-communication with clutch engagement devices  304 ,  306 ,  308 ,  310 ,  312  through signal conductors  304   a,    306   a,    308   a,    310   a,    312   a  respectively. The controller  302  receives input signals via sensors  320 . The input signals can be parameters such as engine RPM, transmission RPM, throttle position, engine torque, gear lever position for gear selection, or other parameters. A manual control override  326  can be used to manually select the gear mode of operation. 
         [0055]    The clutch engagement devices  304 ,  306 ,  308 ,  310 ,  312  can be electromechanical devices, hydraulic or fluid operate devices such as disclosed in U.S. Pat. Nos. 2,825,235; or 4,627,312, herein incorporated by reference. Preferably, the clutch engagement devices are analog or digital solenoids that control hydraulic actuators. Solenoids can also control torque converter fluid fill and fluid line pressure. The controller correlates the input from the sensors  320  to select the appropriate gear mode of operation, such as a first gear mode, second gear mode, third gear mode, fourth gear mode or reverse gear mode. The corresponding engagement device  304 ,  306   308 ,  310 ,  312  is energized to engage the selected one of the friction disks  116 ,  118 ,  120 ,  150 ,  152 , while the respective other friction disks remain disengaged; or no engagement device is engaged so the transmission remains in neutral mode. 
         [0056]    The controller  302  can be an electronic controller and the system can be an electronic system, such as disclosed in U.S. Pat. Nos. 6,604,438 or 4,627,312, herein incorporated by reference. Alternatively, the controller  302  could be a fluid or pneumatically operated valve selector. Preferably, the controller  302  is a programmable electronic controller (PLC) that sends a signal to one or more electromagnetic valves, or solenoid valves, to control actuation of the clutches. Depending on the type of system and controller  302  and the type of engagement devices  304 ,  306 ,  308 ,  310 ,  312  the conductors  304   a,    306   a,    308   a,    310   a,    312   a  can be electric wires, optical fibers, fluid lines, or other known signal carrying conduit. 
         [0057]      FIGS. 1-8  are diagrammatic or schematic drawings and the description herein leaves out information that would be within the knowledge and skill of one of skill in the art. For example, the gears and shafts within the transmission casing would require the necessary bearings and oil seals for proper design and operation. The placement and design of such elements are within the skill of one of ordinary skill in the art. 
         [0058]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.