Abstract:
An electro-hydraulic control system for a vehicle clutch, that operates in both a manual and an automatic mode. The invention provides a way of switching between operating modes not only when the clutch is engaged, but at any time while the vehicle is operating, smoothly and without shock, using a system that contains only one hydraulic circuit and reservoir.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus and system for controlling a clutch, more specifically such an apparatus and system that operates in both a manual and an automatic mode. 
       BACKGROUND OF THE INVENTION 
       [0002]    The characteristics of speed, torque (turning or twisting force), and power (rate or speed at which work is performed) for a typical internal combustion engine in a motor vehicle such as a motorcycle or a car usually do not match the requirements of the final propulsion component. For example, the range of output of the engine in a motorcycle does not match the range of requirements of the wheels in contact with the road surface. A clutch, disengageably connecting the engine to the transmission, provides the means to apply and remove engine torque to the transmission&#39;s input drive shaft. 
         [0003]    A typical hydraulic clutch arrangement includes a clutch hand lever placed at the handlebars which actuates a master cylinder. The master cylinder is fluidly coupled to a slave cylinder mounted on or near the engine casing. The slave cylinder in turn actuates a push rod or alternatively a clutch lever which forcibly disengages the clutch. A hydraulic fluid reservoir typically attached at or near the master cylinder and becomes isolated from the system during master cylinder actuation. Spring biasing, integral to the clutch, biases the slave cylinder and master cylinder at rest so that the fluid reservoir may provide relief against environmental changes. 
         [0004]    A typical hydraulic clutch is disengaged by depressing the clutch lever which compresses the master cylinder, generating pressure that actuates the slave cylinder, and transmits force along the push rod through to a pressure plate, lifting the pressure plate away from the clutch housing, relieving pressure between the friction and friction bearing elements, resulting in the disengagement of the engine from the transmission. This approach has a number of disadvantages, including the physical effort required to disengage the clutch lever which may lead to rider fatigue. Additionally, careful operation of the clutch lever in conjunction with the gear selector requires a level of concentration that may distract the rider and lead to loss of control. Also, mechanical clearances coupled with non-linear hydraulic effects limit clutch feedback and response, which in turn retards the rider&#39;s ability to finely control the clutch. 
         [0005]    Many modern vehicles may incorporate a so-called automatic clutch instead of a manually-actuated clutch, such as the one described above, which automatically engages and disengages a friction clutch with some form of actuator. 
         [0006]    The automatic clutch suffers from a number of drawbacks. If the automatic clutch fails, the vehicle is inoperable. There is no fail-safe mode of operation that permits the continued operation of the vehicle under those conditions. Additionally, the control system for automatics is not intuitive and may not respond to various driving situations when specific modes of clutch operation are desired. For example, the transmission may shift at a time when the rider of the vehicle does not expect it, which may lead to a loss of control. 
         [0007]    In response, the so-called semi-automatic clutch was developed, which included both a manually-actuated clutch in addition to an automatic clutch. The known semi-automatic clutch has a problem when switching between the manual and the automatic modes of operation. During this switching process, when one mode is switched to the other mode during the disconnection of the clutch, the clutch may rapidly be engaged, which may cause unexpected acceleration and a jarring sensation. 
         [0008]    In U.S. Pat. No. 6,170,624, a system is proposed to address connection shock. This application discloses a semi-automatic clutch that may prevent connection shock from occurring during the transfer from one mode to another, but only after the connection of the clutch is finished. 
         [0009]    A drawback of the current state of the art in semi-automatic clutches is that there is a limitation on when the switch may occur between a manual mode and an automatic mode of operation. This limitation on timing prevents the operator from having the complete freedom to engage the manual override of the clutch at any time during operation of the vehicle. 
         [0010]    Another drawback of the current state of the art is the complexity of the current semi-automatic systems. In particular, many alternative systems use a number of isolated hydraulic circuits, which require a separate reservoir for each hydraulic circuit. This complexity may increase the chances of mechanical failure during the prolonged operation that modern vehicles routinely endure, and increase the difficulty and cost of regular maintenance, and repair in the event of a failure. 
         [0011]    There is a need to provide a way of switching between operating modes not only when the clutch is engaged, but at any time while the vehicle is operating, smoothly without shock, using a device that contains only one hydraulic circuit and reservoir. 
       SUMMARY OF THE INVENTION 
       [0012]    An electro-hydraulic control system for a vehicle clutch, comprising:
       a sub-assembly, comprising:
           a manual hydraulic pressure source,   an automatic hydraulic pressure source, and   a slave cylinder that actuates a clutch,   
           with both the automatic hydraulic pressure source and the manual hydraulic pressure source hydraulically feeding the slave cylinder; and   a reservoir; and   an isolation valve, connected hydraulically with the reservoir;
 
wherein the isolation valve isolates the reservoir from the sub-assembly during the actuation of either the manual hydraulic pressure source or the automatic hydraulic pressure source.
       
 
         [0020]    A controller, connected energetically to the isolation valve, the manual hydraulic pressure source, and the automatic hydraulic pressure source, actuates the isolation valve prior to the actuation of either the manual hydraulic pressure source or the automatic hydraulic pressure source so that the reservoir becomes isolated from the sub-assembly. 
         [0021]    The controller, upon receiving a signal from the manual hydraulic pressure source, freezes the flow from the automatic hydraulic pressure source. Alternatively, the controller, upon receiving a signal from the manual hydraulic pressure source, dynamically controls the flow from the automatic hydraulic pressure source so as to transmit mechanical feedback through the manual hydraulic pressure source to a human operator. 
         [0022]    An electro-hydraulic control system for a vehicle clutch, comprising:
       a first sub-assembly, comprising:
           an automatic hydraulic pressure source, and   a slave cylinder that actuates a clutch;   
           a second sub-assembly comprising:
           a manual hydraulic pressure source,   a reservoir, connected hydraulically with the manual hydraulic pressure source, and   a valve interposed between the manual hydraulic pressure source and the reservoir, the valve isolating the reservoir when the manual clutch cylinder is actuated; and   
           an isolation valve, connected hydraulically with the first sub-assembly and the second sub-assembly;
 
wherein both the automatic hydraulic pressure source and the isolation valve connect hydraulically to the slave cylinder, and the isolation valve isolates the first sub-assembly from the second sub-assembly during the actuation of the automatic hydraulic pressure source.
       
 
         [0031]    The manual hydraulic pressure source comprising a manual clutch cylinder connected mechanically to a clutch lever, the clutch lever being moved using direct human effort, wherein the reservoir is proximate the manual clutch cylinder and connected hydraulically with the manual clutch cylinder, and the valve is interposed between the manual clutch cylinder and a reservoir, the valve isolating the reservoir when the manual clutch cylinder is actuated. 
         [0032]    A controller, connected energetically to the isolation valve, the manual hydraulic pressure source, and the automatic hydraulic pressure source, actuates the isolation valve prior to the actuation of the automatic hydraulic pressure source so that the reservoir becomes isolated from the sub-assembly. 
         [0033]    The controller, upon receiving a signal from the manual hydraulic pressure source, freezes the flow from the automatic hydraulic pressure source. Alternatively, the controller, upon receiving a signal from the manual hydraulic pressure source, dynamically controls the flow from the automatic hydraulic pressure source so as to permit the depression of the clutch lever. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Embodiments of the invention will be described by way of example and with reference to the drawings in which: 
           [0035]      FIG. 1  is a schematic view of the invention; 
           [0036]      FIG. 2  is a cross-sectional view of an embodiment of the invention showing the slave cylinder and valve means, when the clutch is engaged; 
           [0037]      FIG. 3  is a cross-sectional view of an embodiment of the invention showing the slave cylinder and valve means, when the clutch is disengaged by the automatic hydraulic pressure source; and 
           [0038]      FIG. 4  is a cross-sectional view of an embodiment of the invention showing the slave cylinder and valve means, when the clutch is disengaged by the manual hydraulic pressure source. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]      FIG. 1  is one embodiment of the invention.  FIG. 2  is a cross-sectional view of a second and preferred embodiment of the invention, at rest.  FIG. 3  shows the embodiment in  FIG. 2  when the primary hydraulic pressure source is actuated.  FIG. 4  shows the embodiment in  FIG. 2  when the manual hydraulic pressure source (the manual override) is actuated. The basic mechanism involves connecting a manual hydraulic pressure source  100  together with an automatic hydraulic pressure source  113  into a slave cylinder  115  so that when either pressure source is actuated, the clutch  130  is disengaged. 
         [0040]    The manual hydraulic pressure source  100  and the automatic hydraulic pressure source  113  may be connected to a tee connection  111  through a manual hydraulic circuit line  109  and an automatic hydraulic circuit line  112 , respectively. From the tee connection  111 , the flow from either pressure source would travel into the slave cylinder  115 , and force a piston  116  to travel. The movement of the piston  116  in turn places pressure on a push rod  121  that travels through the engine casing  114  to a friction clutch  130 . A master cylinder piston  101 , connected to the clutch lever  102 , compresses the fluid in a master cylinder within the manual hydraulic pressure source  100 . 
         [0041]    An isolation valve  110  may be interposed between the manual hydraulic pressure source  100  and the tee connection  111  so as to ensure that when the automatic hydraulic pressure source  113  is activated, there may not be backflow along the manual hydraulic circuit line  109  into the manual hydraulic pressure source  100 . 
         [0042]    A control system (not shown) may be connected to the manual hydraulic pressure source  100  through a clutch switch  108  or other similar sensor so that the control system is signaled upon the actuation of the manual hydraulic pressure source  100  by a clutch lever  102 . The control system may also be connected to the slave cylinder  115  through a position sensor  120 , which measures the position of the piston  116  within the slave cylinder  115 . The control system may also be connected to the isolation valve  110  to ensure the proper and timely activation of the isolation valve  110  during the actuation of the automatic hydraulic pressure source  113 , and the deactivation of the isolation valve  110  when the pressure from the manual hydraulic pressure source  100  exceeds that present at the tee connection  111 , and whenever neither pressure source  100   113  is actuated and the system is at rest. The control system may be connected to the automatic hydraulic pressure source  113  to determine its state at any given time. 
         [0043]    A reservoir  103  may be located at the manual hydraulic pressure source  100  so that when the master cylinder piston  101  travels past the reservoir tie-in point  107  during actuation, the master cylinder piston  101  seals off the reservoir from the rest of the system, preventing backflow to the reservoir  103  during an override event. 
         [0044]    The connection of the hydraulic lines  112   109  to the various hydraulic components  100   115   113  may be made using banjo fittings  106   118 , which may be sealed in place using crush washers  104   105  and bolts. 
         [0045]    The slave cylinder  115  may be affixed to the engine casing  114 . The slave cylinder  115  contains the piston  116 . The piston  116  may be biased by a biasing spring  117  when the system is at rest. The slave cylinder  115  may incorporate a bleed screw  119 , which allows the system to be easily bled of trapped air bubbles during maintenance. 
         [0046]    During automatic operation of the clutch, upon determining that the clutch needs to be disengaged, the controller first activates the isolation valve  110 , so as to prevent backflow into the reservoir  103  and the manual hydraulic pressure source  100 . The controller next actuates the automatic hydraulic pressure source  113 , which delivers pressure to the slave cylinder  115  and disengages the clutch  130 . Once shifting of the transmission is completed, the clutch  130  may be reengaged by relaxing the pressure from the automatic hydraulic pressure source  113 , which allows the piston  116  to return to a neutral position. Isolation of the manual hydraulic pressure source may no longer be required after the piston  116  returns to a neutral position and the automatic hydraulic pressure source  113  stops providing pressure, so the isolation valve  110  deactivates. This permits the system to equilibrate after each disengagement of the clutch, making it more tolerant of environmental changes and small leaks. 
         [0047]    During manual operation of the clutch, the operator depresses the clutch lever  102 , which both slides the master cylinder piston  101  and activates the clutch switch  108 . The master cylinder piston  101  both isolates the reservoir  103  and delivers pressure to the slave cylinder  115 . The isolation valve  110  remains deactivated throughout this operation, and the automatic hydraulic pressure source  113  remains static. Pressure on the piston  116  disengages the clutch  130 . Once shifting of the transmission is completed, the clutch  130  may be reengaged by relaxing the clutch lever  107 , which allows the piston  116  to return to a neutral position. 
         [0048]    During a manual override of an automatic shifting event, the isolation valve  110  may be activated, followed by actuation of the automatic hydraulic pressure source  113 , of the normal automatic operation described above. The operator may then depress the clutch lever  102  to override the clutch. Pressure may build in the manual hydraulic circuit line  109  as the operator squeezes, until the pressure in the manual hydraulic circuit line  109  exceeds that of the automatic hydraulic circuit line  112 , triggering an override event. During an override event, the check valve contained within the isolation valve  110  may open, permitting the flow of fluid from the manual hydraulic pressure source  100  into both the slave cylinder  115  and the automatic hydraulic pressure source  113 . Sensors, such as the clutch switch  108 , may signal the controller that there is an override event in progress. The controller may freeze the automatic hydraulic pressure source  113 , or alternatively may allow the automatic hydraulic pressure source  113  to absorb a volume of fluid at a rate equal to that being displaced by the master cylinder piston  101  as the clutch lever  102  is depressed. The later option is preferable, as it may provide the operator with feedback though the clutch lever  102 , and may smooth the transition between the automatic and manual states. 
         [0049]    The preferred embodiment shown in  FIG. 2  integrates a number of the elements shown in  FIG. 1  into an assembly integral to the housing of the slave cylinder  200 . Specifically, the tee connection  111  and the isolation valve  110  may be incorporated into the slave cylinder  200  to make the system easier to install and maintain. The isolation valve  110  has taken on the form of a pilot operated—poppet type solenoid valve. 
         [0050]    A manual pressure source (not shown) may be connected through the manual hydraulic circuit line  207  to the slave cylinder  200 . This manual pressure source could take the form of the manual hydraulic pressure source  100  or a variation thereof such as any hand or foot operated lever or button assembly, or any mechanically operated pressure source that when actuated isolates the system reservoir (not shown). 
         [0051]    An automatic hydraulic pressure source (not shown) may be connected through the automatic hydraulic circuit line  206  to the slave cylinder  200 . Both circuit lines may be connected to the slave cylinder using a banjo fitting  216  and crush washers  212   213  as shown in  FIG. 2 . 
         [0052]    The isolation valve  203  may comprise a valve body  217 , a solenoid coil  219 , a solenoid armature  220  connected to a plunger  218 , and a poppet  208 . The poppet may contain orifices that act in conjunction with the plunger  218  to form a pilot valve  209  within the poppet  208 . The pilot valve  209  may be biased with a biasing spring  210  to be open when the system is at rest, as shown in  FIG. 2 . On assembly, the isolation valve  203  may be passed though the banjo fitting  221  connected to the automatic hydraulic circuit line  206 , the banjo fitting  221  having crush washers  222   223  on either side, through the slave cylinder  200  housing, and through the banjo fitting  216  connected to the manual hydraulic circuit line  207 , the banjo fitting  213  having crush washers  211   212  on either side. A capping nut  215  may be used to fix the isolation valve  203  and the banjo fittings  216  in place. A bleed screw  214  may be included to allow trapped gas bubbles to escape during maintenance or repair of the system. A circuit isolation seal  211  may be placed on the outside of the isolation valve  203  so that there is no leakage between the circuit lines  207   206  along the outside of the valve. 
         [0053]    The slave cylinder  200  may be affixed to the engine casing  204 . The slave cylinder  200  contains the piston  201 . The piston  201  may be biased by a biasing spring  202  when the system is at rest. During actuation of either or both of the pressure sources, the piston  201  may travel, putting pressure on the push rod  205 , and disengaging the clutch. 
         [0054]    When the system is at rest, and neither pressure source is actuated, the poppet  208  and the plunger  218  may be positioned as shown in  FIG. 2 . The biasing spring  210  may hold the pilot valve  209  open. The solenoid coil  219  may not be energized, the solenoid armature  220  may be in a neutral position, and the plunger  218  may be in a retracted position relative to the poppet  208 , so the pilot valve  209  may be in an open position. Fluid in all pathways may be relaxed. 
         [0055]    In  FIG. 3 , the automatic hydraulic pressure source is actuated. The solenoid coil  219  may be energized, the solenoid armature  220  may be in a forward position, and the plunger  218  may be in an engaged position relative to the poppet  208 , so the pilot valve  209  may be in a closed position. The poppet  208  may be held closed by the force from the energized solenoid though the plunger  218  and pilot valve  209  combined with the pressure differential across the poppet  208 . Fluid may be permitted to flow from the automatic hydraulic pressure source along the automatic hydraulic circuit line  206  around the isolation valve  203  and into the slave cylinder  200 . The piston  201  may move under pressure as the fluid flows into the slave cylinder  200 . 
         [0056]    In  FIG. 4 , the manual hydraulic pressure source is actuated while the automatic hydraulic pressure source is actuated. Pressure may build up in the manual hydraulic circuit line  207 . When the pressure in the manual hydraulic circuit line  207  exceeds that in the automatic hydraulic circuit line  206  and the pressure provided by the energized solenoid though the plunger  218  and though the pilot valve  209 , the poppet  208 , pilot valve  209 , and the plunger  218  may all be forced downwards, permitting fluid to flow from the manual hydraulic circuit line  207  though the isolation valve  203  into both the automatic hydraulic circuit line  206  and the slave cylinder  200 . This flow of fluid may maintain pressure on the piston  201 , keeping the clutch disengaged. The automatic hydraulic pressure source may absorb a volume of fluid at a rate equal to that being displaced by manual hydraulic pressure source, providing the operator with feedback though the clutch lever  102 , and smoothing the transition between the automatic and manual states. 
         [0057]    A digital controller may be used, reading in data from sensor inputs such as switches and position sensors, and writing data to actuators such as relays and solenoids. An analog circuit may be used to support the digital controller. Position sensors, pressure transducers, or switches may be used to detect the states of the valves and cylinders, including to detect manual operation during normal operation, and may be used by the controller to disable any automatic clutch operation except during engine damaging conditions. 
         [0058]    The isolation valve  110  may be replaced with a simple on/off valve (not shown) that blocks flow during the activation of the automatic hydraulic force  100 . Such a variant may require precise timing from the controller. 
         [0059]    In one embodiment, the isolation valve and the reservoir are hydraulically connected with the hydraulic circuit formed between the manual hydraulic pressure source, the automatic hydraulic pressure source, and the slave cylinder, instead having the manual hydraulic pressure source interposed between the isolation valve and the reservoir, as described above. 
         [0060]    It will be appreciated that the above description relates to the preferred embodiments by way of example only. Many variations on the system and method for delivering the invention without departing from the spirit of same will be clear to those knowledgeable in the field, and such variations are within the scope of the invention as described and claimed, whether or not expressly described.