Abstract:
A manual transmission clutch protection apparatus includes a shift gate cylinder acted upon by the operator controlled shift lever having a first shift pattern that represents all possible shift positions and two or more additional but limited shift patterns corresponding to certain gears which limit the gears selectable and enagageable by the vehicle operator. Two or more actuators which may be solenoids or other electric, hydraulic or pneumatic actuators translate blocking pins or plungers into the additional or limited shift patterns to lockout or block motion of the shift lever and shift gate cylinder into certain gears. Engine speed and temperature sensors, a vehicle speed sensor and a current gear sensor provide data which is utilized to compute which gears, under current sensed operating conditions, should be locked out, that is, unavailable for selection by the vehicle operator.

Description:
FIELD 
     The present disclosure relates to clutches for manual transmissions for motor vehicles and more particularly to a speed limiting device for manual transmission clutches for motor vehicles. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     Although no longer the most popular choice in consumer motor vehicles (passenger cars, sport utility vehicles and light trucks), the manual transmission and clutch were originally and for many years the sole powertrain speed and torque matching components available. Nonetheless, for certain uses and for certain consumers, the manual transmission and manual clutch remain the speed and torque matching components of choice. The absolute and positive control of the vehicle powertrain, generally better fuel economy and freedom of operation offered by such components to the driver has not been duplicated in even the most sophisticated automatic transmissions. 
     The freedom of operation is not without drawbacks, however. For example, selection and operation in a gear ratio, i.e., fourth or fifth, which is too high for the current vehicle speed results in lugging by the engine and sluggish vehicle acceleration. Engagement and disengagement of the clutch by the vehicle operator which is excessively slow or preventing full engagement of the clutch by resting a foot on the clutch pedal causes excessive wear of the clutch surface and can significantly shorten clutch life. A downshift which skips a gear, i.e., a fourth to second gear downshift or a fourth to first gear downshift, can cause dramatic increases in clutch disk speed which can damage the clutch disk and, again, shorten its life. Newer manual transmissions with multiple cone synchronizers can achieve synchronization with much larger speed differentials than single cone synchronizers, thus generating even higher, vehicle driven clutch disk speeds during skipped gear downshifts. Clutch failures which are the result of such overspeed constitute approximately 20 percent of the total of clutch failures. While such drawbacks are generally associated with drivers who are either unskilled or unfamiliar with the vehicle, it is apparent that intervention by vehicle systems could reduce or eliminate some or all of these problems. The present invention is so directed. 
     SUMMARY 
     The present invention provides a manual transmission clutch protection apparatus. The apparatus includes a shift gate cylinder or similar member acted upon by the operator controlled shift lever having a first shift pattern engaged by a stationary register pin that represents and allows all possible shift positions and two or more additional but limited shift patterns corresponding to certain gears which limit the gears selectable and enagageable by the vehicle operator. Two or more actuators which may be solenoids or other electric, hydraulic or pneumatic actuators translate blocking pins or plungers into the additional or limited shift patterns to block motion of the shift lever and shift gate cylinder into certain gears. An engine speed sensor and a vehicle speed sensor as well as an optional temperature sensor and an optional current gear sensor provide data which is utilized to compute which gears, under current sensed operating conditions, should be locked out, that is, unavailable for selection by the vehicle operator, in order to prevent damage to the clutch. 
     Thus it is an aspect of the present invention to provide a clutch protection apparatus for a manual transmission. 
     It is a further aspect of the present invention to provide a clutch protection apparatus having a shift gate cylinder including a shift pattern that represents all possible shift positions. 
     It is a still further aspect of the present invention to provide a clutch protection apparatus having a shift gate cylinder including multiple shift patterns that prevent certain shifts. 
     It is a still further aspect of the present invention to provide a clutch protection apparatus having multiple actuators having pins or plungers that selectively engage multiple shift patterns that prevent certain shifts. 
     It is a still further aspect of the present invention to provide a clutch protection apparatus having an engine speed sensor, a vehicle speed sensor, an optional temperature sensor and an optional current gear sensor. 
     It is a still further aspect of the present invention to provide a clutch protection apparatus having components which receive data from sensors and compute which gears, under current sensed operating conditions, should be locked out, that is, unavailable for selection by the vehicle operator. 
     Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a side elevational view of a manual transmission shift assembly incorporating the present invention; 
         FIG. 2  is an enlarged, end elevational view of a portion of a manual transmission shift assembly incorporating the present invention; 
         FIG. 3  is an enlarged, bottom view of a portion of a manual transmission shift assembly incorporating the present invention; 
         FIG. 4  is an enlarged, bottom view of a portion of an alternate embodiment of a manual transmission shift assembly incorporating the present invention; and 
         FIG. 5  is a diagram of the components and operational scheme of a clutch protection apparatus according to the present invention for a manual transmission. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     With reference to  FIGS. 1 and 2 , a clutch protection apparatus for a manual transmission is illustrated and generally designated by the reference number  10 . The clutch protection apparatus  10  is associated with a manual transmission  12  having a housing  14  which supports, positions and protects various components of the transmission  12  including the clutch protection apparatus  10 . The transmission  12  includes a main, friction plate clutch  16  which is operably disposed between an output shaft  18  of a prime mover  20  such as a gasoline, flex-fuel or Diesel engine or hybrid or electric power plant, a transmission input shaft  22  and a transmission output shaft  24 . 
     The transmission  12  also includes a shift lever  26  which extends into the vehicle passenger compartment (not illustrated) and is engageable and moveable by the vehicle operator (also not illustrated). Alternatively, the transmission  12  may be coupled to the shift lever  26  by levers and cables (also not illustrated). The shift lever  26  is operably coupled to a shift gate or location cylinder  30  or similar member. The shift gate or location cylinder  30  is secured to or formed integrally with a shift actuation shaft  32  that is co-axial with the shift gate cylinder  30 . The shift gate cylinder  30  and the shift actuation shaft  32  are supported in suitable apertures, slots or blind openings (not illustrated) in the housing  14  so that they may freely translate and rotate about the axis defined thereby in accordance with forces applied thereto by the shift lever  26 . 
     Secured to the shift actuation shaft  32  at multiple locations are two or more shift forks  34  that engage and translate synchronizer clutches  36 . Each of the synchronizer clutches  36  is associated with one or two gears (not illustrated) that are disposed upon countershafts or layshafts  38  and which are first synchronized with such countershafts or layshafts  38  and then directly and positively connected to the countershafts or layshafts  38  by the synchronizer clutches  36  in accordance with conventional manual transmission operation. The shift actuation shaft  32  also includes one or more lockout mechanisms  39  that ensure that more than one gear cannot be engaged at any one time. 
     Returning to the shift gate cylinder  30 , it includes a rotation and translation limiting gate assembly  40 . The gate assembly  40  defines a plurality of spaced apart channels or slots  42 A,  42 B,  42 C and  42 D that are arranged circumferentially on the outside surface of the shift gate cylinder  30  and are connected by a continuous axial channel or slot  44  (or plurality of short channels or slots) disposed at the circumferential mid-point of the channels or slots  42 B,  42 C and  42 D. A single register or locator pin  46  is mounted to and secured within the housing  14  or to any suitable component thereof and extends radially into the channels or slots  42 A,  42 B,  42 C,  42 D and  44 . The register or locator pin  46  and the rotation and translation limiting gate assembly  40  thus cooperate to control and define the allowed or available motion of the shift gate cylinder  30  and the shift actuation shaft  32 . This motion corresponds to the motion of the shift lever  26  necessary to select and engage the various forward and reverse gears of the manual transmission  12 . 
     Typically, though not necessarily, the half slot  42 A will be assigned to and actuate reverse, the upper half of the full left slot  42 B will be assigned to and actuate first gear and the lower half of the full left slot  42 B will be assigned to and actuate second gear. The upper half of the full middle slot  42 C will be assigned to and actuate third gear and the lower half of the full middle slot  42 C will be assigned to and actuate fourth gear. The upper half of the full right slot  42 D will be assigned to and actuate fifth gear and the lower half of the full right slot  42 D will be assigned to and actuate sixth gear. It should be appreciated that the foregoing described shift pattern is exemplary and illustrative only and that other shift patterns and shift patterns having more or fewer slots and gears are well within the scope of this invention. 
     Referring now to  FIGS. 1 ,  2  and  3 , preferably disposed at any convenient circumferential remove, e.g., 90° or 180°, from the location of the register or locator pin  46  are a pair of gate blocking actuator assemblies  50  and  60 . A first gate blocking actuator  52  includes a pin, plunger or stub shaft  54  that is selectively received within a first circumferential slot  56  having a circumferential length at least as long as the right slot  42 D. The first gate blocking actuator  52  may be a solenoid or an electric linear, hydraulic or pneumatic actuator. When the pin, plunger or shaft  54  of the first gate blocking actuator  52  is extended into the first circumferential slot  56 , motion of the shift gate cylinder  30  is restricted to rotation in the right slot  42 D and selection of either (only) fifth or sixth gears. As will be explained more fully below, this prevents a downshift into a lower gear that, given current operating conditions, might overspeed the clutch  16  and cause damage thereto. 
     A second gate blocking actuator  62  includes a pin, plunger or stub shaft  64  that is selectively received within a second circumferential “H” pattern slot  66  having circumferential lengths at least as long as the slots  42 C and  42 D and identical axial spacing. The gate blocking actuator  62  may also be a solenoid or an electric linear, hydraulic or pneumatic actuator. When the pin, plunger or shaft  64  of the second gate blocking actuator  62  is extended into the second circumferential “H” slot  66 , motion of the shift gate cylinder  30  is restricted to rotation in the full middle slot  42 C and the full right slot  42 D and selection of either third, fourth, fifth or sixth gears. Note that, as clearly shown in  FIG. 3 , the pin or plunger  64  is similarly located in the slot  66  relative to the register pin  46  and the slots  42 C and  42 D, that is, assuming the “H” slot  66  corresponds to the slots  42 C and  42 D and relates to third, fourth, fifth and sixth gears, the pin or plunger  64  is disposed to the left in  FIG. 3 , in the slot corresponding to third and fourth gears. As will be explained more fully below, this arrangement also prevents a downshift into a lower gear that, given current operating conditions, might overspeed and damage the clutch  16 . 
     In  FIG. 4 , an alternate embodiment of a portion of a manual transmission shift assembly according to the present invention is illustrated and designated by the reference number  80 . The alternate embodiment shift assembly  80  includes a shift gate cylinder  30 ′ which is disposed on and secured to the shift actuation shaft  32  or may be formed integrally therewith. Not shown in  FIG. 4  but included in the shift gate cylinder  30 ′ is the rotation and translation limiting gate assembly  40  of  FIG. 1  defining the plurality of spaced apart, interconnected channels or slots  42 A,  42 B,  42 C and  42 D. The shift gate cylinder  30 ′ also includes a second, selectively engageable rotation and translation limiting gate assembly  82 . The gate assembly  82  defines four spaced apart shift or gate patterns  84 ,  92 ,  98  and  106  that are preferably arranged along a longitudinal axis on the outside surface of the shift gate cylinder  30 ′. Each of the shift or gate patterns  84 ,  92 ,  98  and  106  locks out or prohibits operator selection of certain gears much as described above except that the four shift or gate patterns  84 ,  92 ,  98  and  106  provide improved and more targeted lockout control and operation. 
     The first shift or gate pattern  84  is associated with a first actuator  86  which may be electric, hydraulic or pneumatic and which includes a pin, plunger or shaft  88  which may be activated or energized to extend into the shift or gate pattern  84  and lockout or inhibit selection of all gears except fifth and sixth. The second shift or gate pattern  92  is associated with a second actuator  94  which may be electric, hydraulic or pneumatic and which includes a pin, plunger or shaft  96  which may be activated or energized to extend into the shift or gate pattern  92  and lockout or inhibit selection of first, second and third gears. 
     The third shift or gate pattern  98  is associated with a third actuator  102  which may be electric, hydraulic or pneumatic and which includes a pin, plunger or shaft  104  which may be activated or energized to extend into the shift or gate pattern  98  and lockout or inhibit selection of first and second gears. The fourth shift or gate pattern  106  is associated with a fourth actuator  108  which may be electric, hydraulic or pneumatic and which includes a pin, plunger or shaft  112  which may be activated or energized to extend into the shift or gate pattern  106  and lockout or inhibit selection of first gear. Once again, it should be noted that except for the pin or plunger  88 , the pins or plungers  96 ,  104  and  112  are arranged similarly such that they all reside in the same region of the shift or gate pattern corresponding to, in this example, third and fourth gears when the single register or locator pin  46  (shown in  FIG. 1 ) is similarly disposed. 
     Referring now to  FIG. 5  and the other drawing Figures, components relating to operation of the manual transmission clutch protection apparatus  10  and  80  according to the present invention are generally designated by the reference number  120  and will now be described. The components  120  relating to operation include an engine speed sensor  122  and an optional engine temperature sensor  124 . Data from the engine speed sensor  122  is provided to a first comparator  126  which determines if the speed of the engine  20  is above or below 1800 r.p.m. or other minimum threshold speed. If it is below 1800 r.p.m., the first comparator  126  provides a signal to a control module  130  which disables the clutch protection apparatus  10  and  80 . If the speed of the engine  20  is above 1800 r.p.m., the first comparator  126  provides a signal to a second comparator  136 . 
     The second comparator  136  receives data from a first computational module  138  which receives data regarding both the speed of the engine  20  from the engine speed sensor  122  and the temperature of the engine  20  from the optional engine temperature sensor  124 . The first computational module  138  determines a combined engine speed/temperature value which is provided to the second comparator  136 . If the second comparator  136  determines that the current combined engine speed/temperature value is below a predetermined (threshold) value, it provides a signal to the control module  130  which again disables the clutch protection apparatus  10  and  80 . If the second comparator  136  determines that the current combined engine speed/temperature value is above a predetermined (threshold) value, it provides a signal to a second control module  140  which enables the clutch protection apparatus  10  and  80  by providing a signal to a second computational module  142 . The second computational module  142  receives data from a vehicle speed sensor  144  and an optional current gear sensor  146  which is typically associated with the shift gate cylinder  30  or  30 ′. Based upon this data, the second computational module  142  issues commands to the actuators  52  and  62  in accordance with the lookup table  150  to lockout or block the selection of certain gears by the vehicle operator. In the lookup table, an “X” in a column means an actuator is activated and an “O” in a column means it is de-activated. For example, if the manual transmission  12  is in fourth gear and the second control module  140  has enabled the apparatus  10  and  80 , the actuator  62  will be activated to prevent or block a shift into first or second gear, that is, into the full left slot  42 B of the rotation and translation limiting gate assembly  40 . 
     It should be appreciated that the determination of the particular gears that are blocked or locked out by the activation of the actuators  52 ,  62 ,  86 ,  94 ,  102  and  108  and the conditions under which they are blocked or locked out, will be based upon many factors including engine speed, engine temperature, vehicle speed, the gear ratios of the transmission, the number of gears, the clutch size and clutch safety factor, to name the more significant factors. 
     The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.