Patent Publication Number: US-2006019797-A1

Title: Input shaft brake

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a vehicle transmission system that has an input shaft brake disposed between a clutch and a multiple speed gear transmission.  
      2. Background Art  
      Vehicles are provided with transmissions that provide multiple gear ratios for different power and speed requirements. Many different types of transmissions have been developed, including manual transmissions, automatic transmissions and automated shift transmissions. Automatic transmissions are generally provided for cars and light trucks that provide fully automatic shifting by means of a complex hydraulic and electronic control system. Manual transmissions are simpler and generally require manual disengagement of a clutch and manual movement of a shift lever to engage different gear ratios. Automated shift manual transmissions have been developed that provide the convenience of an automatic transmission but are shifted by means of X-Y shift control motors that move a shift lever in manual transmissions.  
      Each of the above-described transmission systems may be provided with a synchronizing system that synchronizes a selected gear with a rotating input shaft. The synchronizing system facilitates smooth shifting without the noise caused by a failure of gears to properly mesh as they are engaged. Prior art automated shift transmissions are generally coupled to an input shaft without a brake. Synchronizing systems cause input shaft supported gears and output shaft supported gears to rotate at near synchronous speeds. Synchronizing systems add cost and weight to transmissions synchronizing systems require time to synchronize rotation of gears and can delay shifting operations.  
      One approach to permit more rapid shift performance is to provide an inertia brake that is mounted to a transmission power takeoff location. An inertia brake mounted at a power takeoff location can be used to slow shaft rotation and may allow shifts to be synchronized more rapidly. One disadvantage of power takeoff mounted inertia brakes is that such devices add weight to the transmission that can adversely impact fuel economy. Another disadvantage is that assembling a power takeoff mounted inertia brake to the transmission increases the cost of parts and labor. In addition, mounting the inertia brake to a power takeoff location makes that power takeoff location unavailable for other purposes.  
      In the design of transmissions, of any type, it is an objective to provide capability to shift more quickly and smoothly. By providing quicker shifts, transmission performance and efficiency may be improved.  
      There is a need for a low cost system for providing quicker shifts by allowing more rapid transmission gear synchronization. The present invention is directed to improving transmission performance and providing quicker shifting capability as summarized below.  
     SUMMARY OF THE INVENTION  
      According to one aspect of the present invention, a combination of a vehicle engine, a multiple ratio geared transmission and an input shaft inertia brake is provided. The input shaft inertia brake is secured to an input shaft and is at least partially disposed in a housing. The input shaft is disposed between the crankshaft of the engine and the transmission. In one embodiment of the invention the input shaft brake may comprise a rotor, or disk, secured to the input shaft and a brake piston that is axially shiftable relative to the input shaft. At least one member is grounded to the housing and mounted adjacent to one side of the rotor for relative axial movement. A second member may also be grounded to the housing and mounted adjacent to another side of the rotor for relative axial movement. A fluid cavity is defined by the housing and one side of the brake piston. At least one fluid port (hydraulic or pneumatic) is provided in the housing that is in fluid flow communication with the fluid cavity so that fluid supplied to the cavity through the fluid port may selectively move the rotor and at least one of the members into engagement. A return spring may be provided that applies a biasing force to urge the members out of engagement with the rotor.  
      According to another aspect of the present invention, a transmission system for a vehicle having an engine is provided with an inertia brake between a clutch and the transmission. The clutch is operatively connected to the engine to selectively transfer torque from the engine. A multiple speed gear transmission has an input shaft that receives torque from the engine through the clutch. The input shaft is at least partially disposed within a housing located between the engine and the transmission. The inertia brake in one embodiment may comprise a rotor that is secured to the input shaft and a brake piston that is axially movable relative to the input shaft. The brake may further comprise first and second members that are grounded to the housing and are mounted for relative axial movement on opposite sides of the disk. A fluid cavity is defined on one side of the brake piston. At least one fluid port is provided in the housing that is in fluid flow communication with the fluid cavity on the one side of the brake piston. Fluid supplied to the cavity through the fluid port moves the piston into engagement with the first member that shifts relative to the rotor and may also shift the rotor into engagement with the second member. A return spring biases the first end second members out of engagement with the rotor.  
      Other aspects of the invention relate to a control system that may be provided to control gear selection. The brake piston may be actuated during a shift operation upon a determination that it is desired to change gears. The control system may be a hydraulic or pneumatic control system. The control system may have a first sensor for determining the speed of rotation of the input shaft and a driving gear attached to the input shaft. A second sensor may be provided for determining the speed of rotation of a driven gear in the transmission. The control system controls application of the inertia brake to reduce the speed of rotation of the input shaft and facilitate engagement of the drive gear and driven gear.  
      According to another aspect of the invention, the return spring may apply a biasing force to the brake piston indirectly by engaging the first and second disk brake plates to separate them from each other. The return spring may be disposed in the housing adjacent a radially outer margin of the disk that is secured to the input shaft.  
      According to other aspects of the invention, anti-rotation means may be provided to prevent rotation of the piston and/or the first and second members. The anti-rotation means may comprise bosses formed in the housing that are receptacles by cooperating receptacles in the piston. Alternatively, the anti-rotation means may be axially extending recesses in the housing that receive tabs, ears, or other protrusions formed on the piston or first and second members. The anti-rotation means may also comprise dowel pins or bolts that connect or ground the piston, first and second members or a bearing cap to the housing.  
      According to another aspect of the invention, a method of controlling a multiple speed transmission system of a vehicle is provided in which an input shaft brake is utilized to reduce the speed of rotation of the input shaft. According to the method, a transmission system is provided that has a clutch and an input shaft brake that is disposed between a crankshaft of the engine and the multiple speed transmission portion of the transmission system. A controller has a first sensor associated with the input shaft and a second sensor associated with an output shaft. The method further comprises determining the speed of rotation of a first rotating component with the first sensor while also determining the speed of rotation of a second rotating component with the second sensor. Next, the input shaft brake is actuated to apply a braking force to reduce the speed of rotation of the input shaft. The input shaft is coupled to the output shaft through the transmission when the speed rotation of the first and second rotating components are matched to within a predetermined degree of speed differential.  
      According to a further aspect of the invention as it relates to the method, a synchronizer may be provided in the transmission that synchronizes a drive gear with a driven gear. Application of the input shaft brake may be used to reduce the speed of rotation of the input shaft and allow the synchronizer to synchronize the drive gear and driven gear in less time. Alternatively, the transmission may be provided without a synchronizer and the inertia brake may provide the sole mechanism for matching the speed of rotation of the drive gear and driven gear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic diagram of an engine and a multiple speed geared transmission made according to one embodiment of the present invention;  
       FIG. 2  is a fragmentary cross-sectional view of an input shaft brake made according to one embodiment of the present invention;  
       FIG. 3  is a fragmentary exploded perspective view of the input shaft brake as illustrated in  FIG. 2 ;  
       FIG. 4  is a fragmentary cross-sectional view of an input shaft brake made according to one alternative embodiment of the present invention;  
       FIG. 5  is a fragmentary exploded perspective view of the input shaft brake illustrated in  FIG. 4 ;  
       FIG. 6  is a fragmentary cross-sectional view of an input shaft brake made according to another alternative embodiment of the present invention;  
       FIG. 7  is a fragmentary cross-sectional view of an input shaft brake made according to another alternative embodiment of the present invention;  
       FIG. 8  is a fragmentary cross-sectional view of an input shaft brake made according to another alternative embodiment of the present invention;  
       FIG. 9  is a fragmentary perspective partially cut-away view of another alternative embodiment of the present invention;  
       FIG. 10  is a fragmentary cross-sectional view of an input shaft brake made according to another alternative embodiment of the present invention;  
       FIG. 11  is a fragmentary perspective partially cut-away view of another alternative embodiment of the present invention; and  
       FIG. 12  is a fragmentary cross-sectional view of an input shaft brake made according to another alternative embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
      Referring to  FIG. 1 , a transmission system  10  for a vehicle engine  12  is schematically illustrated. The engine  12  has a crankshaft  14  that is connected through a clutch  16  to an input shaft  18 . An input shaft brake  20  is assembled to the input shaft  18 . The input shaft  18  is connected to a multi-speed gear transmission  22  that is controlled by a controller  24 . Controller  24  monitors transmission operations and may also monitor engine operations. The controller may also obtain data from other signal sources as is well known in the art. For example, a rotation sensor  26  may be provided to monitor the speed of rotation of the input shaft  18 . The controller  24  may also receive data from an engine speed tachometer or the engine controller  28 . A wide variety of sensors may be used to provide data to the controller  28 .  
      Referring to  FIGS. 2 and 3 , a portion of a transmission  22  is shown that is adapted to receive torque from an input shaft  18  of the engine  12 . An inertia brake housing  34  encloses an input shaft brake  20  and is either secured to or integrally formed with the transmission housing  36 . Input shaft brake  20  has a disk  40 , or rotor, having splines  42  formed on its inner diameter that are engaged by and mate with splines  44  formed on the input shaft  18 . Input shaft  18  is received within an opening  46  in the inertia brake housing  34 .  
      A brake piston  50  is disposed in a chamber  52  defined within the inertia brake housing  34 . A port  54  opening into the chamber  52  is connected to a source of control fluid such as a hydraulic pump or air compressor  56 . The hydraulic pump or air compressor  56  is controlled by the transmission controller  24 . Control fluid is used to shift the brake piston  50  within the chamber  52  when pressurized fluid is injected into the port  54  under pressure.  
      The brake piston  50  has an inner O-ring seal  57  and an outer O-ring seal  58  that seal between the piston  50  and the chamber  52  as the brake piston  50  is moved.  
      A thrust bearing  60  is provided between the brake piston  50  and the input shaft disk  40 . The input shaft disk  40  rotates with the input shaft  18  while the brake piston  50  does not rotate.  
      A brake disk  62  is formed of a friction material and is retained in the inertia brake housing  34  by grounding teeth  66  that are received in recesses  68  formed in the transmission housing  36 . The brake disk  62  is prevented from rotating by the grounding teeth  66  that are held by the recesses  68 .  
      A return spring  70  is disposed in an annular space  72  defined between the outer diameter of the input shaft disk  50  and the inertia brake housing  34 . Return spring  70  exerts a biasing force against the brake piston  50  to bias the brake piston  50  into a disengaged position. The return spring  70  is received in an annular groove  74  formed in the brake piston  50  on one end and on the other end is received in an annular seat  76  formed by the brake disk  62  and inertia brake housing  34 .  
      In operation, when the transmission is to be shifted, it may be advantageous to slow input shaft  18  rotation to improve shift or synchronizer performance. When the transmission control system  24  determines the need for input shaft  18  braking, hydraulic fluid or compressed air may be provided to the port  54 . In either case, the fluid pressure applied to the brake piston  50  causes the brake piston  50  to shift toward the input shaft disk  40 . The brake piston  50  engages the thrust bearing  60  that in turn engages the input shaft disk  40 . Input shaft disk  40  is axially shifted within the inertia brake housing  34 . Splines  42  and  44  permit the disk  40  to move axially to a limited extent allowing the input shaft disk  40  to be forced into engagement with brake disk  62 . When the input shaft disk  40  engages the brake disk  62 , rotation of the disk  40  is slowed as a result of the application of braking force. Brake disk  62  is grounded by means of the grounding teeth  66  to the recesses  68  formed in the inertia brake housing  34 .  
      When the transmission control determines that sufficient braking force has been applied to the input shaft disk  40 , the hydraulic or pneumatic fluid is exhausted through the port  54  as a result of the biasing force applied to the brake piston  50  by the return spring  70 . The brake piston  50  shifts axially to disengage the input shaft disk  40  and eliminate the braking force applied to the input shaft disk  40 .  
      Referring now to  FIGS. 4 and 5 , an alternative embodiment of a transmission  80  is partially shown with its input shaft  82 . The input shaft  82  is received within an inertia brake housing  84  or, alternatively, could be received within a transmission housing  86 . An input shaft disk  90  rotates with the input shaft  82 . Input shaft disk  90  has a plurality of splines  92  formed on its inner diameter that receive splines  94  formed on the input shaft  82 . The input shaft  82  extends through an opening  96  formed in the inertia brake housing  84 .  
      A brake piston  100  is disposed in a chamber  102  formed in the inertia brake housing  84 . A port  104  opens into the chamber  102 . Port  104  is connected to a source of fluid such as a hydraulic pump or air compressor that are controlled by the transmission controller. The control fluid is used to selectively move the brake piston  100  within the chamber  102 .  
      The brake piston  100  has an inner O-ring seal  106  and an outer O-ring seal  108  that seal between the brake piston  100  and the chamber  102 .  
      First and second brake disks  110  and  112  have first and second sets of grounding teeth  114  and  116  that ground the brake disks  110 ,  112  to the inertia brake housing  84 . Axially relieved recesses  118  are provided in the inertia brake housing  84  for the grounding teeth  114  of the first brake disk  110 . The axially relieved recesses  118  allow the first brake disk  110  to move to a limited extent in an axial direction when the brake piston  100  is axially shifted within the chamber  102 . When the brake piston  100  is shifted within the chamber  102 , first brake disk  110  engages a first side  122  of the input shaft disk  90  causing it to shift axially on the splines  92  and  94  until a second side  124  of the input shaft disk  90  engages the second brake disk  112 . In this way, the first and second brake disks  110  and  112  engage opposite sides of the input shaft disk  90  to apply a braking force to the input shaft disk and slow rotation of the input shaft  82 .  
      A return spring  128  is provided in an annular space  130  formed between the outer diameter of the input shaft disk  90  and the inertia brake housing  84 . An angular groove  132  in the brake piston  100  receives one end of the return spring  128 . The other end of the return spring  128  is received in an annular seat  134  formed in the inertia brake housing  84 .  
      In operation, this alternative embodiment of the input shaft brake of the present invention is engaged during a shift operation as controlled by the transmission control. When the transmission control determines that it would be advantageous to apply a braking force to the input shaft  82 , compressed air or hydraulic fluid is supplied to the chamber  102  through the port  104 . The fluid exerts a force on brake piston  100  causing it to be axially shifted within the chamber  102 . Brake piston  100  contacts the first brake disk  110  and shifts it to a limited extent in an axial direction toward the input shaft disk  90 . Input shaft disk  90  is shifted into contact with the second brake disk  112 . The first and second brake disks  110 ,  112  apply a braking force to first and second sides  122  and  124  of the input shaft disk  90 . When the transmission control determines that sufficient braking force has been applied to the input shaft disk  90 , the control fluid, either compressed air or hydraulic fluid, is exhausted through the port  104  as a result of the biasing force applied by the return spring  128  to the brake piston  100 . When the brake piston  100  is shifted by the spring  128 , the first and second brake disks  110 ,  112  cease applying brake pressure to the input shaft disk  90 .  
       FIGS. 6 through 12  provide additional alternative embodiments of the invention that operate in a manner similar to the previously described embodiments. The following embodiments focus on different anti-rotation structures and combinations of braking elements that may be implemented within the spirit and scope of the invention. Other combinations are possible and the invention should not be limited to any approach.  
      Referring to  FIG. 6 , an alternative embodiment of the present invention is shown. A portion of a transmission housing  140  is shown in conjunction with a portion of an inertia brake housing  142 . An input shaft  144  extends through the inertia brake housing  142  into the transmission housing  140 . The inertia brake housing  142  defines a chamber  146  in which a piston  148  is contained for a limited degree of axial shifting relative to the input shaft  144 . The piston  148  is prevented from axial rotation by bosses  150  that are integrally formed on the inertia brake housing  142  to extend into the chamber  146 . The bosses  150  are received within receptacles  152  formed in the piston  148 . The piston  148  is axially shiftable to engage a plate  154  which in turn engages a rotor  156  that is formed of friction material and may be a powder metal disk having friction material disposed in the matrix of the disk. A plate  158  is provided on the opposite side of the rotor  156  from the plate  154 . When the piston  148  is shifted by hydraulic or pneumatic pressure described above with regard to the embodiments of  FIGS. 1-6 , the piston  148  shifts axially to cause the plate  154  to engage the rotor  156  that in turn engages the plate  158 . Plate  158  is held against rotation by the inertia brake housing  142  that traps the plate  158  against the transmission housing  140 . A bearing cap  160  is mounted to the transmission housing  140  that also engages a part of an antifriction bearing  162 . Another part of the antifriction bearing  162  is secured to the input shaft  144 . The input shaft  144  rotates with the rotor  156  and is supported within the bearing cap  160  by the antifriction bearing  162 . The piston  148 , plate  154 , plate  158 , and bearing cap  160  are non-rotatably attached between the transmission housing  140  and inertia brake housing  142 .  
      Referring to  FIG. 7 , another embodiment of the present invention is shown in which the transmission housing  170  and inertia brake housing  172  are assembled as previously described. An input shaft  174  extends through the inertia brake housing  172  and into transmission housing  170 . The inertia brake housing  172  defines a chamber  176  in which a piston  178  is mounted for limited axial movement. The piston  178  is secured to a plurality of bosses  180  performed on the inertia brake housing  172 . The bosses  180  are received within receptacles  182  formed on one side of the piston  178 . A plate  184  is assembled around the input shaft  174  with a friction disk  186  and a bearing cap  190 . The plate  184  is axially shifted by movement of the piston  178  against the plate  184  causing it to engage the rotor  186  that in turn is pressed against the bearing cap  190 . A bolt  194  secures the piston  178  to the plate  184 . The piston is prevented from rotation by the bosses  180  while the plate is held against rotation by the piston  178  which is connected to the plate by a bolt  194 .  
      A wave spring  196  is provided radially outboard of the rotor  186 . The wave spring  196  holds the plate  184  away from the bearing cap  190  so that normally, when no fluid pressure is applied to the piston  178 , the plate  184  is held away from the rotor  186 , and is also separated from the bearing cap  190 .  
      Referring to  FIG. 8 , another alternative embodiment of the invention is shown in which a transmission housing  200  and inertia brake housing  202  are fragmentarily illustrated in conjunction with a portion of an input shaft  204  that extends through the inertia brake housing  202  and into the transmission housing  200 . A chamber  206  is defined in the inertia brake housing  202 . A piston  208  is disposed in the chamber  206 . The piston  208  is axially shiftable to engage a plate  214  that is also axially shiftable relative to a friction disk  216 . Plate  214  is grounded to the inertia brake housing  202  by teeth or splines (not shown) for preventing rotation. The friction disk  216  is assembled for rotation to the input shaft  204  and is axially shiftable to a limited extent so that it may engage bearing cap  220 . Bearing cap  220  is stationary and is mounted in the transmission housing  200 . A friction bearing  222  is provided between the bearing cap  220  and input shaft  204  to facilitate rotation of the input shaft  204  within the transmission housing  200  and inertia brake housing  202 . A bolt  224  is provided to secure the bearing cap  220  to the transmission housing  200  and thereby prevent rotation of the bearing cap  220  with the input shaft  204 . A wave spring  226  is provided radially outboard of the rotor or friction disk  216 . The wave spring exerts a force on the plate  214  and bearing cap  220  to hold them apart and thereby permit the rotor  216  and the input shaft  204  to rotate freely whenever a pneumatic or hydraulic pressure is removed from the piston  208 .  
      Referring to  FIG. 9 , an improved inertia brake housing  230  is shown that has a chamber  232  in which a piston  234  is received for limited axial movement. A front plate  236  is mounted concentrically with the piston  234  within the chamber  232 . The front plate  236  is adapted to axially engage friction disk  238  when the piston  234  is axially shifted causing the front plate  236  and a rear plate  240  to engage opposite sides of the friction disk  238 . The front plate  236  has teeth or splines (not shown) for preventing rotation. The rear plate  240  is prevented from rotating by the engagement of ribs  242 , or grounding teeth, in corresponding slots  244  formed in the inertia brake housing  230 . The slots  244  are elongated and also preferably received ribs or teeth (not shown) that are formed in the outer periphery of the front plate  236 . Ribs  242  prevent the rear plate  240  from rotating.  
      Referring to  FIG. 10 , the transmission housing  250  and inertia brake housing  252  are shown assembled together with a piston  254  axially shiftably disposed within the inertia brake housing  252 . Receptacles  256  formed in the piston  254  are adapted to receive bosses  258  that may be integrally formed in the inertia brake housing  252  for preventing rotation while allowing limited axial movement. The piston  254  in the illustrated embodiment directly engages a friction disk  260  that in turn engages a bearing cap  262 . The piston  254  is shifted by the application of hydraulic or pneumatic pressure on the side of the piston  254  opposite the rotor  260 . The rotor  260  is preferably formed of friction material embedded in a powder metal. The bearing cap  262  is retained within the transmission housing  250  and supports an outer race of the bearing  264 . Inner race of the bearing  264  is secured to the input shaft  266  so that the input shaft  266  may rotate within the bearing cap  262  except for when the input shaft break is engaged. A wave spring  268  is assembled in an inertia brake housing  252  outboard of the rotor  260 . The wave spring  268  functions to hold the piston  254  and bearing cap  262  apart from the rotor  260 .  
      Referring to  FIG. 11 , an inertia brake housing  270  is shown for an alternative embodiment of the present invention. The inertia brake housing  270  encloses a piston  272  that is shiftable within a chamber  274  defined by the inertia brake housing  270 . A plate  276  is mounted for limited axial shifting within the inertia brake housing  270 . The plate  276  may be shifted when hydraulic or pneumatic pressure is applied to the piston  272  to cause the plate  276  to engage the rotor  280 . Rotor  280  includes friction material and is preferably formed by a powder metal forming process. A wave spring  282  is assembled to the inertia brake housing  270  to apply a return force to the plate  276 . Anti-rotation dowels  284  may be provided in bores  286  that are spaced around the inertia brake housing  270 . The anti-rotation dowels  284  prevent rotation of the plate  276  while allowing axial movement. The inner diameter of the rotor  280  is provided with keys  288  that are used to secure the rotor  280  to an input shaft (not shown) but as previously described with reference to the preceding embodiments.  
      Referring to  FIG. 12 , a transmission housing  300  is shown in conjunction with an inertia brake housing  302  and input shaft  304 . The input shaft  304  extends through the inertia brake housing  302  and into the transmission housing  300 . A piston  306  is provided within a chamber  308  defined by the inertia brake housing  302 . A plate  312  is engaged by the piston  306  that causes the plate  312  to be shifted when hydraulic or pneumatic pressure is applied to the piston  306 . The plate  312  is prevented from rotating by circumferentially spaced notches in an outer edge flange  314  that allow the plate  312  to slide axially on shoulder bolts  316  that engage the friction disk, or rotor  318 . When pressure is applied by the piston  306 , the plate  312  is permitted to shift axially to engage a rotor  318  that is made of friction material. The rotor  318  also shifts axially to engage a bearing cap  320 . A braking force is developed between the plate  312 , rotor  318  and bearing cap  320  when pressure is applied by the piston  306 . The bearing cap  320  is secured to the transmission housing  300  and also retains the outer race to the bearing  322 . Bearing  322  supports on its inner race the input shaft  304  for rotation within the transmission housing  300  and inertia brake housing  302 . A wave spring  324  exerts an outward force between the plate  312  and bearing cap  320  causing the plate  312  and bearing cap  322  to release the rotor  318  when no braking force is applied to the rotor  318  by the piston  306 .  
      While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.