Abstract:
A vehicle clutch control system that can eliminate discomfort due to a sudden start of a vehicle. The vehicle clutch control system includes an engine speed detector ( 203 ) for detecting an engine revolution speed, and an engine controller ( 211 ) for controlling an accelerator opening of an engine ( 222 ). A vehicle speed detector ( 204 ) is also provided for detecting vehicle speed. A clutch actuator ( 212 ) engages and disengages a friction clutch ( 304 ), and a clutch controller ( 205 ) controls engagement and disengagement of the clutch by giving commands to the clutch actuator. In a vehicle start stand-by state in which the vehicle speed is zero and a certain start gear has been selected, if the engine speed detected by the engine speed detector ( 203 ) is higher than a predetermined speed, then a clutch engaging control is not performed because otherwise the vehicle would start suddenly upon clutch engagement.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority under 35 USC 119 of Japanese Patent Application No. 2000-127662 filed on Apr. 24, 2000, the entire disclosure of which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a clutch control device for a vehicle provided with an automatic clutch function and an automatic transmission (gear speed change) function, and in particular to such a clutch control device that can eliminate the discomfort upon a sudden start of a vehicle.  
           [0004]    2. Description of the Related Art  
           [0005]    Some of recent vehicles are equipped with a controller and actuators that in combination operate various parts of the vehicles automatically. Specifically, the operation of mechanical parts necessary for the vehicle motion is caused not manually upon movements of pedals and levers, but a controller detects the movements of the pedals and levers, and operates the mechanical parts via actuators. Such vehicles are often equipped with an automatic clutch function and automatic transmission function such that the controller automatically determines the appropriate time for changing the gear speed of the transmission, controlling the clutch and the transmission without waiting for the driver&#39;s operation.  
           [0006]    In vehicles with a conventional automatic clutch function and automatic transmission function, to let the vehicle start move from a halting position, a driver puts (shifts) the gear change lever (shift lever) into a position such as drive or reverse, and the transmission automatically switches to a suitable gear speed, thus preparing the vehicle for start. When the vehicle thus has been prepared for start, it is in a “vehicle start stand-by” condition; the vehicle still stands and the gear position of the transmission is set to a certain start gear. In the “vehicle start stand-by” condition, clutch engaging control is performed in response to the driver&#39;s stepping onto the accelerator pedal, which causes the vehicle to start moving. That is to say, when the vehicle start stand-by condition is detected, the amount that the driver has stamped the accelerator pedal or the engine speed is detected. Then, if the engine speed is faster than a predetermined speed, it is assumed that the driver intends to start moving the car, and a clutch engaging control is performed.  
           [0007]    On the other hand, if the engine speed is not higher than the predetermined speed, for example when the driver is not stepping on the accelerator pedal, then it is assumed that the driver does not intend to start moving the car. Thus, the clutch engaging control is not performed, and the vehicle stays in the vehicle start stand-by state.  
           [0008]    However, when the engine&#39;s idling speed is increased, for example due to warming up or overload of the air condition, or when a driver has stepped on the accelerator pedal to check the engine (racing), and the driver shifts the speed change lever to a start gear position, then the vehicle is brought into the vehicle start stand-by condition. Likewise, when the gear change lever is abusively put into a start position (that is, in an action discouraged by the manual) or erroneously while the accelerator pedal is depressed down considerably, then the vehicle goes into the start stand-by state. Subsequently, the vehicle starts moving due to the automatic clutch function since the engine speed is higher than the predetermined speed. As a result, a sudden start of the vehicle occurs upon engaging of the clutch, and the driver will experience the impact of this sudden start, i.e., the discomfort due to a jerking movement.  
         SUMMARY OF THE INVENTION  
         [0009]    It is an object of the present invention to provide a vehicle clutch control device that can eliminate the aforementioned problems.  
           [0010]    In order to attain this object, the present invention provides a vehicle clutch control device that includes a clutch actuator unit for engaging and disengaging a friction clutch, and a controller for prohibiting the clutch actuator unit from engaging the clutch when a vehicle speed is zero and a start gear is selected, but a rotational speed of an engine is higher than a predetermined speed.  
           [0011]    The controller may cause the engine rotational speed to drop below the predetermined speed when it prohibits the clutch actuator unit from engaging the clutch. The controller may further allow the clutch actuator unit to engage the clutch when the engine rotational speed drops below the predetermined speed. The controller may hold an accelerator opening of the engine to a predetermined value (e.g., 0%) until the engine rotational speed drops below the predetermined speed.  
           [0012]    The controller may hold an accelerator opening of the engine to a predetermined value (e.g., 0%) for a prescribed period after it prohibits the clutch actuator unit from engaging the clutch, and may allow the clutch actuator unit to engage the clutch after the prescribed period regardless of the engine rotational speed. The prescribed period is, for example, about 5 seconds.  
           [0013]    Additional objects, aspects and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the embodiment(s) and the appended claims, taken in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 illustrates a flowchart of the procedure for preventing vehicle start performed by a clutch control device in an embodiment of the present invention.  
         [0015]    [0015]FIG. 2 illustrates a diagram of the main parts of a vehicle using the clutch control device of the present invention.  
         [0016]    [0016]FIG. 3 illustrates a detail of the multi-speed transmission system and the pneumatic cylinder system in FIG. 2.  
         [0017]    [0017]FIG. 4 illustrates the actuator system in the clutch control device of the present invention.  
         [0018]    [0018]FIG. 5 is a graph used for clutch position control in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    The following is a detailed description of a preferred embodiment of the present invention.  
         [0020]    Clutch control devices in accordance with the present invention may be used, for example, in vehicles employing multi-speed transmission systems. Main components of such a vehicle will first be described.  
         [0021]    Referring to FIG. 2, such a vehicle includes an engine  222 , a friction clutch  304 , a multi-speed transmission system  201  which is coupled to the engine  222  over the friction clutch  304 , and a pneumatic cylinder system  202  which serves as the actuator for the multi-speed transmission system  201 . An engine speed sensor  203  (engine speed detection means) is attached to the engine  222  to detect the engine revolution speed. An output shaft speed sensor  204  (means for detecting the vehicle speed) is attached to the transmission  201  to detect the revolution speed of the output shaft of the transmission  201  as vehicle speed information. A controller (TMCU)  205  for the multi-speed transmission  201  constitutes the clutch control means controlling the engaging and disengaging of the clutch  304  and the transmission control means controlling the change of the gear speeds of the multi-speed transmission system  201 . An accelerator sensor  206  detects an accelerator opening desired by the driver based on how deep the accelerator pedal has been stamped. A gear change lever unit  207  communicates gear changes performed by a driver to the transmission controller  205 . An automatic/manual (A/M) toggle switch is provided at a top of a shift lever stem for setting the operation of the transmission to automatic or manual operation mode. An emergency gear change switch  208  allows the driver to forcibly select a gear speed in special circumstances, such as emergencies. A clutch pedal  209  is stamped and released by the driver to disengage and engage the clutch  304  in the manual operation mode. A gear display  210  in the dashboard console displays the currently selected gear as a number. An engine control unit (ECU)  211  is associated with the engine  222  and constitutes the engine control means instructing the engine of the controlled accelerator opening and the fuel injection time. A clutch actuator  212  is associated with the clutch  304  to engage and disengage the clutch  304 . A clutch stroke sensor  213  is used to detect a position of the actuator  212 . Reference numeral  226  designates a valve for maintaining an air pressure.  
         [0022]    The transmission controller  205  receives signals indicative of the vehicle&#39;s running status from the engine speed sensor  203 , the output shaft speed sensor  204  and other sensors/detectors, and reads data from shift-down and shift-up maps from its memory. The transmission controller  205  can perform various processes at time intervals of several dozen ms by multi-timer interrupts. The transmission controller  205  and the engine controller  211  are connected by a bus cable and can communicate with one another. The gear change lever  207  has the stable positions of reverse (R), neutral (N), drive (D) and hold (H), as well as the momentary positions of shift-up operation request (UP) and shift-down operation request (DOWN).  
         [0023]    The detail of the multi-speed transmission system  201  and the pneumatic cylinder system  202  shown in FIG. 2 will be described with reference to FIG. 3.  
         [0024]    In the multi-speed transmission system  201 , a two-speed transmission splitter  302  whose transmission ratio is relatively small is located prior to a 4-speed main gear box  301 , and a 2-speed transmission range  303  whose transmission ratio is relatively large is located behind the main bear box  301 . The splitter  302  has the three positions, i.e., high speed (H), low speed (L) and neutral. A splitter gear  316 , a splitter dog gear  317 , and a sleeve  319  are arranged inside the splitter  302 . The splitter gear  316  is normally engaged with a counter gear  315 ′ on a counter shaft  306 . The splitter dog gear  317  is formed in one piece with the splitter gear  316 . The sleeve  319  is normally engaged with an input shaft gear  318  formed in one piece with the input shaft  305 , and can engage with either the splitter dog gear  317  or another dog gear  321  in the main transmission  301  (described below). The splitter  302  can transmit the rotation of the input shaft  305 , taken from a driven plate of the clutch  304 , at the transmission ratio H or L to the counter shaft  306 , or block it.  
         [0025]    The main transmission  301  has six positions, i.e., 1st, 2nd, 3rd, 4th, reverse and neutral. A plurality of counter gears  315 , a plurality of main gears  320 , a plurality of dog gears  321 , and a plurality of sleeves  323  are arranged inside the main transmission  301 . The counter gears  315  are formed in one piece with the counter shaft  306 . The main gears  320  are normally engaged with the corresponding counter gears  315 . The dog gears  321  are formed in one piece with the main gears  320 . The sleeves  323  are normally engaged with main shaft gears  322  formed in one piece with the main shaft  307 , and can engage with adjacent dog gears  321 . When the splitter  302  is in the L position, the rotation of the input shaft  305  is transferred to the counter shaft  306  at the lower ratio and causes the dog gears  321  to rotate relatively slowly in the main transmission  301 . Upon sliding one of the sleeves  323  over one adjacent dog gear  321 , one of the four forward speeds or the reverse is selected in the main gear transmission  301  at the engaged dog gear so that the rotation of the input shaft is transferred to the main shaft  307 . The sleeves  323  are actuated by the pneumatic cylinder system  202 . If no sleeves  323  are slid, the rotations of the dog gears  321  are not transferred to the main shaft  307 , i.e., blocked in the main transmission  301 . On the other hand, when the splitter  302  is in the H position, the rotation of the input shaft  305  is transferred to the counter shaft  306  at the higher ratio, and the dog gears  321  are caused to rotate at a relatively high speed. Upon sliding one sleeve  323 , one of the four forward speeds or the reverse is selected and the rotation of the engaged dog gear is transferred to the main shaft  307 . If no sleeves  232  are slid, no rotations are transmitted to the main shaft  307  in the main transmission  301 .  
         [0026]    The transmission range  303  has a planetary gear set. A sun gear  308  positioned at the center of the planetary gear set is fixed to the main shaft  307 , a carrier  310  coaxially holding the planetary gears  309  disposed around the sun gear  308  is fixed to an output shaft  311 , and the rotation of the main shaft  307  can be transmitted to the output shaft  311  at the transmission ratio L or H of the range gear by switching the coupling of a ring gear  312  disposed around the planetary gears  309  between splines  324  extending from the transmission housing and splines  325  extending from the output shaft  311 .  
         [0027]    Numeral  313  denotes a counter shaft brake, and numeral  314  denotes a counter shaft speed sensor. These components are used for synchronizing the speed of the dog gears on the main shaft to the speed of the sleeves, in an electronic synchronization control that replaces the mechanical synchronization control.  
         [0028]    The pneumatic cylinder system  202  includes a splitter cylinder  330  whose stroke is controlled by three electromagnetic valves, a select cylinder  340  whose stroke is controlled by three electromagnetic valves, a sleeve shift cylinder  350  whose stroke is controlled by two electromagnetic valves, a range cylinder  360  whose stroke is controlled by two electromagnetic valves, and a counter shaft brake cylinder  313  which is turned on and off with one electromagnetic valve  371 , and the combined operation of these electromagnetic valves selectively actuates the various parts and portions of the multi-speed transmission system  201 . Numeral  380  denotes an air source.  
         [0029]    In the splitter cylinder  330 , the electromagnetic valve MVH is connected to the cylinder base, the electromagnetic valve MVF is connected to the cylinder body, and the electromagnetic valve MVG is connected to the cylinder top, a head  331  provided with rods on both sides is accommodated in the cylinder body, and another head  332  without rods is accommodated in the cylinder base.  
         [0030]    The splitter cylinder  330  operates as follows: When only the electromagnetic valve MVF is actuated, then the head  331  moves toward the cylinder head (to the right in FIG. 3) so that in the splitter  302  the splitter sleeve  319  linked to the rod  333  moves into L position. When only the electromagnetic valve MVG is actuated, then the head  331  moves toward the cylinder base (to the left in FIG. 3) so that the splitter sleeve  319  moves into H position. When the electromagnetic valves MVG and MVH are actuated, then the other head  332  moves toward the cylinder body so that a movement of the head  331  toward the cylinder base is checked by its left rod and stopped at an intermediate position. As a result, the splitter sleeve  319  stops at a neutral position.  
         [0031]    In the select cylinder  340  the electromagnetic valve MVE is connected to the cylinder base, the electromagnetic valve MVD is connected to the cylinder body, and the electromagnetic valve MVC is connected to the cylinder head. A head  341  provided with rods on both sides is accommodated in the cylinder body, and another head  342  without rods is accommodated in the cylinder base.  
         [0032]    The select cylinder  340  operates as follows: When only the electromagnetic valve MVD is actuated, then the head  341  moves toward the cylinder head (downward in FIG. 3) so that the selector  391  linked to the rod  343  moves to the N 3  position of the shifter  392 . From N 3  position, the main gear transmission  301  can be put into 3rd or 4th gear. When only the electromagnetic valve MVC is actuated, then the head  341  moves toward the cylinder base (upward in the drawing) so that the selector  391  moves to the N 1  position of the shifter  393 . From N 1  position, the main gear transmission  301  can be put into the reverse gear. When the electromagnetic valves MVC and MVE are operated, the other head  342  moves toward the cylinder body so that a movement of the head  341  toward the cylinder base is checked by the rod and stopped at an intermediate position, and the selector  391  stops at the N 2  position of the shifter  294 . From the N 2  position, the main gear transmission  301  can be put into 1st or 2nd gear.  
         [0033]    In the sleeve shift cylinder  350 , the electromagnetic valve MVB is connected to the cylinder head, and the electromagnetic valve MVA is connected to the cylinder base. A single head  351  provided with a single rod  352  is accommodated in the cylinder body.  
         [0034]    The sleeve shift cylinder  350  operates as follows: When only the electromagnetic valve MVA is actuated, then the head  351  moves toward the cylinder head (to the left in FIG. 3), so that the selector  391  linked to the rod  352  moves toward the direction of the reverse, 2nd and 4th (to the left in the drawing). When only the electromagnetic valve MVB is actuated, then the head  351  moves toward the cylinder base (to the right in FIG. 3) so that the selector  391  moves to the direction of the 1st and 3rd gears. When the electromagnetic valves MVA and MVB are operated, the head  351  is in neutral position, and the selector  391  is also in neutral position.  
         [0035]    The shifters  393 ,  394  and  392  are coupled to the corresponding sleeves  323  of the main transmission  301 . If the select cylinder  340  moves the selector  391  into one of the positions N 1 , N 2  and N 3  and then the sleeve shift cylinder  350  moves the selector  391  right or left in FIG. 3, a desired sleeve  323  meshes with a desired dog gear  321  so that the main transmission  301  can be changed into the first, second, third or fourth forward gear and the reverse gear. Moreover, it is possible to put the main transmission  301  into neutral by putting the selector  391  into neutral position.  
         [0036]    In the range shift cylinder  360 , the electromagnetic valve MVI is connected to the cylinder head, and the electromagnetic valve MVJ is connected to the cylinder base. A single head  361  provided with a rod  362  is accommodated in the cylinder body.  
         [0037]    The range shift cylinder  360  operates as follows: When only the electromagnetic valve MVI is actuated, then the head  361  moves toward the cylinder base (to the right in FIG. 3), so that the range sleeve  326  of the range  303  coupled to the rod  362  moves into H position. When only the electromagnetic valve MVJ is actuated, then the head  361  moves toward the cylinder head (to the left in FIG. 3) so that the range sleeve  326  moves into L position.  
         [0038]    By selectively turning the electromagnetic valves of this pneumatic cylinder system  202  on and off in combination, the multi-speed transmission system  201  can be switched to 16 forward speed positions and two reverse speed positions, as well as the splitter neutral position and the main transmission neutral position.  
         [0039]    The configuration of the actuator system for clutch disengagement and engagement will be described with reference to FIG. 4.  
         [0040]    This actuator system includes a clutch booster  401  which constitutes the actuator  212  (FIG. 2) for engaging and disengaging the clutch, a proportional valve  402  which pneumatically gives a stroke amount to this clutch booster  401 , an on/off valve  403  located upstream of the proportional valve to block air supply, an emergency valve  404  for forcibly disengaging the clutch completely, and the clutch pedal  209  which hydraulically drives a relay piston  405  of the clutch booster  401 . Numeral  411  denotes an air source, and numeral  412  denotes a double-check valve. The clutch booster  401  causes a member  406  to stroke, in proportion to the supplied air, and this member  406  is coupled with the pressure plate of the clutch  304  (FIG. 3).  
         [0041]    The following describes how the actuator system in FIG. 4 operates.  
         [0042]    When the main power source is turned on with the vehicle&#39;s key switch, the controller (TMCU)  205  turns on the valve  403  and allows air supply to the proportional valve  402 . When the main power source is turned off, the controller  205  turns off the valve  403  and prevents a drop of the pressure in the air source  411  due to draining of air from the proportional valve  402 . When the clutch is disengaged and engaged, the controller  205  provides a control current to the proportional valve  402 . The proportional valve  402  supplies air to the clutch booster  401  in an amount that is proportional to the current, so that any clutch position from clutch complete disengagement to complete engagement can be regulated with the current. Consequently, it is possible to perform a finely tuned control, such as partly engaged condition, with the controller  205 . The emergency valve  404  can completely disengage the clutch  304  quickly, and is used to prevent a jerking forward of the vehicle in extra-ordinary circumstances. The emergency valve  404  is turned on and off by the controller  205 , but it can also be actuated manually with an emergency switch (not shown). When the clutch pedal  209  is pushed down by a driver&#39;s foot, the member  406  is pushed outward by hydraulic pressure, and the relay piston  405  is driven whereby air is supplied to the clutch booster  401 , and helps and supports the stroke of the member  406 .  
         [0043]    Referring back to FIG. 3, “vehicle start preparation”, “vehicle start stand-by”, and “vehicle start” with the automatic clutch function and automatic transmission (speed change) function will be described.  
         [0044]    In the automatic speed change mode, when the gear change lever  207  in FIG. 2 is put into D position or reverse position while the vehicle speed is zero (which means that the vehicle speed based on the speed of the output shaft  311  detected by the output shaft speed sensor  204  is 0 km/h), then, as the vehicle start preparation, the controller  205  sets the optimum gear speed for starting off the vehicle as the target gear speed while the clutch  304  is disengaged by the actuator system of FIG. 4, and the multi-speed transmission system  201  switches the start gear speed to the target gear speed by regulating the pneumatic cylinder system  202  accordingly. When this vehicle start preparation is complete, the vehicle then goes into the start stand-by condition, which means that the vehicle speed is still zero, and a certain start gear speed has been selected for the gear position of the multi-speed transmission system  201 . In this vehicle start stand-by condition, if the engine speed detected by the engine speed detection means  203  is higher than a predetermined speed, then the clutch engaging control is not carried out. The engine speed is lowered below the predetermined speed by holding the engine&#39;s accelerator opening for a predetermined time at 0%, after which the clutch engaging control becomes possible with the actuator of FIG. 4.  
         [0045]    Subsequently, the clutch engagement is performed. Specifically, the controller  205  changes the regulation target of the clutch and the regulated accelerator opening notified to the engine by the controller  211  along the control curve shown in FIG. 5. That is to say, starting with a regulated accelerator opening of 0%, the accelerator opening is gradually increased, and also the regulation target of the clutch starts at a position of complete disengagement and is gradually changed toward an engaging position. By driving the proportional valve  402  of FIG. 4 in correspondence to the changing clutch regulation target, the clutch position is gradually changed to engaging. Eventually, the vehicle starts moving so that the regulated accelerator opening switches from the control curve in FIG. 5 to a value corresponding to the accelerator opening requested depending on the amount the accelerator pedal has been pushed down.  
         [0046]    Thus, a smooth start is achieved with the automatic clutch function, and the pushing of the accelerator pedal can be reflected quickly in the acceleration, so that a calm vehicle start is possible.  
         [0047]    It should be noted that after the predetermined time has elapsed, the clutch engaging control may be enabled even when the engine speed has not been lowered below the predetermined speed.  
         [0048]    The following is a detailed description of the procedure of prohibiting vehicle start, with reference to FIG. 1.  
         [0049]    First of all, in Step S 1 , based on the speed of the output shaft  311  detected by the output speed sensor  204 , it is determined whether the vehicle speed is 0 km/h. If the vehicle speed is not 0 km/h, then the driving control should be performed, so that this procedure is unnecessary, and the program advances to Step S 6  and is terminated. If the vehicle speed at Step S 1  is 0 km/h, then the program advances to Step S 2 , and it is determined whether the gear change lever is in a position other than the neutral (N). If the gear change lever at Step  2  is in the N position, then the start prohibition procedure is unnecessary, so that the program advances to Step S 6  and is terminated. If the gear change lever is not in the N position at Step S 2 , then the automatic clutch function is in operation and the vehicle is about to start moving, so that the program advances to Step S 3 , and it is determined whether the engine speed detected by the engine speed sensor  203  is higher than a predetermined speed (for example, set to 700 rpm; idling speed set to 500 rpm). If the engine speed is lower than the predetermined speed, then a smooth start in a regular start motion is possible, so that the program advances to Step S 6  and is terminated.  
         [0050]    If the engine speed at Step S 3  is higher than the predetermined speed, then the program advances to Step S 4 , and it is determined whether the time indicated by a timer has not reached a predetermined value (for example, 5 sec). The timer starts counting the time when a start gear is selected. Consequently, at first, the time indicated by the timer is lower than the predetermined value. If the time indicated by the timer at Step S 4  is lower than the predetermined value, then the procedure advances to Step S 5 , and the timer is incremented (that is, one unit is added). The timer sums up the time at intervals that correspond to the interrupt time interval of this procedure. Then, in Step S 7 , the 0% accelerator opening regulation for holding the regulated accelerator opening at 0% begins. If the regulated accelerator opening is held at 0%, the regulation target of the clutch is held at a position of complete disengagement, in accordance with the control chart in FIG. 5, so that the clutch engaging control is effectively prohibited, and the start of the vehicle is deferred.  
         [0051]    Eventually, the engine speed drops below the predetermined speed (No at Step S 3 ), and the program advances to Step S 6 . At Step S 6 , the 0% accelerator opening regulation is released. Thus, the clutch engaging control becomes possible. Because the engine speed is now lower than the predetermined speed, a smooth start is performed in a regular start motion.  
         [0052]    It is possible that the time indicated by the timer exceeds the predetermined value, while the engine speed is still faster than the predetermined speed. Usually, when the accelerator opening is narrowed to 0%, the engine should return to idling speed within 5 sec, even if the engine was at the highest speed. If the engine speed does not decrease below the predetermined speed even after the predetermined time has passed, then this may be because the idling speed is for some reason made higher than normal. In this case, in order to allow driving as soon as possible, the 0% accelerator opening regulation should be released to get out of the situation of deferred start. To do this, if the predetermined time has elapsed in Step S 4 , the program advances to Step S 6  in this embodiment. At Step S 6 , the 0% accelerator opening regulation is released, and the clutch engaging control becomes possible, so that the vehicle starts moving as in a regular start.