Automatic clutch control system

A method of operating an automatic clutch control system in a vehicle having an engine with a throttle, said system including a shift lever having a neutral position and at least one run position, a clutch having drive and driven shafts, first speed detecting means for detecting the rotational speed of said drive shaft, second speed detecting means for detecting the rotational speed of said driven shaft, throttle detecting means for detecting the opening of a throttle valve, position detecting means for detecting the position of said shift lever, clutch control means for controlling a degree of engagement of said clutch in accordance with a clutch engagement control signal, and electronic control means for generating said clutch engagement control signal, said method comprising the steps of:

• (a) monitoring said shift lever position for a detected change of said shift lever position from its neutral position to its run position;
• (b) calculating a ratio of the rotational speed of said driven shaft to the rotational speed of said drive shaft when said change in shift lever position is detected and provided that the rotational speed of the drive shaft is equal to or greater than a first preset speed value, and applying to said clutch control means a clutch engagement control signal representing a minimum degree of engagement of said clutch when said ratio is equal to or less than a first preset ratio value provided that either the throttle opening is equal to or greater than a first preset throttle value or the rotational speed of said drive shaft is equal to or greater than a second preset speed value;
• (c) monitoring said shift lever position and (1) upon detecting that the shift lever is in its neutral position, applying to said clutch control means a clutch engagement control signal instructing the disengagement of said clutch and thereafter returning to said monitoring step described in paragraph (a) above, and (2) applying to said clutch control means a clutch engagement control signal instructing the disengagement of said clutch and returning to said calculating and applying step described in paragraph (b) above when said shift lever is in a position other than its neutral position and said throttle opening is equal to or less than a second preset throttle value, and when said throttle opening exceeds said second preset throttle value, effecting a clutch engagement control over a long time interval by selecting a particular group of clutch engagement control signals having a level change rate which corresponds to the current values of said ratio and said throttle opening and applying to said clutch control means at short time intervals a sequence of clutch engagement control signals from said selected group;
• (d) effecting clutch engagement control in accordance with the procedure in the above-described step (c) over successive long time intervals while continually updating said clutch engagement control signals until a clutch engagement control signal is applied to said clutch control means indicating a maximum degree of engagement of said clutch, and thereafter ceasing the updating of said clutch engagement control signals, monitoring said shift lever position and returning to said monitoring step described in paragraph (a) above if said shift lever is detected in its neutral position, and monitoring the throttle opening and generating a clutch engagement control signal indicating disengagement of said clutch and returning to step (b) above when the throttle opening is equal to or less than said second preset value;
• (e) when said ratio exceeds said first preset ratio value, comparing said ratio to a second preset ratio value and advancing to step (c) if said ratio is equal to or less than said second preset ratio value, and effecting a vehicle braking mode of clutch control over further long time intervals if said ratio exceeds said second preset ratio value, said step of effecting a vehicle braking mode comprising specifying a particular group of clutch engagement control signals having a signal level change rate which corresponds to said ratio and applying to said clutch control means at short time intervals a sequence of clutch engagement control signals from said specified group while continually updating said clutch engagement control signals until a clutch engagement control signal has been applied which indicates a maximum degree of engagement of said clutch, and thereafter ceasing the updating of said clutch engagement control signals and monitoring said shift lever position, the throttle position and the rotational speed of said drive shaft and returning to step (a) and generating a clutch engagement control signal for disengaging said clutch if said shift lever is detected in its neutral position or if the throttle opening and rotational speed of said drive shaft are not within given limits.