Clutch upshift control

Claim 1

A method of operating a motor vehicle which prevents driveline torque disturbances due to lash in speed ratio mechanisms when a reduction in operator demand causes the torque carried by a transmission input shaft to reverse polarity, in a motor vehicle having an engine (l2) for producing output torque in accordance with operator demand, an automatic transmission (l4) having upper and lower speed ratio mechanisms for effecting predefined upper and lower speed ratios between input (42) and output (22) shafts thereof and a fluid-operated torque-establishing device (28 to 32) associated with each of the upper and lower speed ratio mechanisms, each such torque-establishing device (28 to 32) being effective when activated to establish a bidirectional path of torque transmission between the transmission input (42) and output (22) shafts via the associated speed ratio mechanism, a fluid coupling (24) for transmitting the engine output torque to the transmission input shaft (42), and a shift controller (270) for selecting a desired speed ratio in accordance with the operator demand and selectively activating and de-activating the torque-establishing devices (28 to 32) so as to establish the desired speed ratio, the method comprising the steps of: monitoring the operator demand and detecting the occurrence of a specified operating condition which is likely to result in a relatively sharp reversal in the polarity of torque applied to the transmission input shaft (42) by way of the fluid coupling (24); determining a measure of the torque transmitted through the fluid coupling (24) in relation to the relative speeds of the engine (l2) and transmission input shaft (42) following the detection of the specified operating condition; and de-activating any activated torque-establishing device (28 to 32) when the measure of torque becomes less than a reference amount, so that when the reversal in applied torque occurs the torque-establishing devices (28 to 32) are ineffective to transmit such torque to the vehicle driveline.

Claim 2

A method of operating a motor vehicle which prevents driveline torque disturbances due to lash in speed ratio mechanisms when a reduction in operator demand causes the torque carried by a transmission input shaft to reverse polarity, in a motor vehicle having an engine (l2) for producing output torque in accordance with operator demand, an automatic transmission (l4) having upper and lower speed ratio mechanisms for effecting predefined upper and lower speed ratios between input (42) and output (22) shafts thereof and a fluid-operated torque-establishing device (28 to 32) associated with each of the upper and lower speed ratio mechanisms, each such torque-establishing device (28 to 32) being effective when activated to establish a bidirectional path of torque transmission between the transmission input (42) and output (22) shafts via the associated speed ratio mechanism, a fluid coupling (24) for transmitting the engine output torque to the transmission input shaft (42), and a shift controller (270) for selecting a desired speed ratio in accordance with the operator demand and selectively activating and de-activating the torque-establishing devices (28 to 32) so as to establish the desired speed ratio, the method comprising the steps of: monitoring the operator demand and detecting the occurrence of a specified operating condition which is likely to result in a relatively sharp reversal in the polarity of torque applied to the transmission input shaft (42) by way of the fluid coupling (24); determining a measure of the torque transmitted through the fluid coupling (24) in relation to the relative speeds of the engine (l2) and transmission input shaft (42) following the detection of the specified operating condition; and de-activating any activated torque-establishing device (28 to 32) when the measure of torque becomes less than a reference amount, so that when the reversal in applied torque occurs the torque-establishing devices (28 to 32) are ineffective to transmit such torque to the vehicle driveline.

Claim 3

A method according to claim l, characterised in that the measure of torque transmitted through the fluid coupling (24) is determined in relation to the ratio of engine speed to transmission input shaft speed.

Claim 4

A method according to claim l or 2, characterised in that the engine (l2) has a throttle (l6) adjustable in accordance with operator demand, and the operator demand is monitored by sensing the throttle position.

Claim 7

A method according to any one of claims l to 5, characterised in that the method includes the step of: inhibiting the de-activation of an activated torque-establishing device (28 to 32) if the measure of torque transmitted through the fluid coupling (24) fails to become less than the reference amount within a predetermined time after the specified operating condition has been detected.

Claim 8

A method according to any one of claims l to 6, characterised in that the method includes the step of: inhibiting the de-activation of an activated torque-establishing device (28 to 32) if the detected operating conditions will not cause the shift controller (270) to effect an upshift from the lower speed ratio to the upper speed ratio.

Claim 9

A method according to any one of claims l to 7, characterised in that: the step of monitoring the operator demand is effected to identify the occurrence of a first set of operating conditions likely to result in a relatively minor reversal in the polarity of torque applied to the transmission input shaft (42) and a second set of operating conditions likely to result in a relatively sharp reversal of the polarity of torque applied to the transmission input shaft (42); in response to the identification of the first or second set of operating conditions the predetermined shift parameters of the shift controller (270) are adjusted so as to soften the activation of the torque-establishing device (28 to 32) associated with the upper speed ratio mechanism in the impending upshift; and the step of determining a measure of the torque transmitted through the fluid coupling (24) is effected in response to the identification of the second set of operating conditions, with the de-activation of any activated torque-establishing device (28 to 32) being effected when such measure becomes less than a reference amount corresponding to a relatively low input torque level.

Claim 12

A method according to any one of claims 8 to l0, characterised in that the first reference position is determined in direct relation to the engine speed so that for a given throttle movement the first set of operating conditions will be more likely to be detected at a relatively high engine speed than at a relatively low engine speed.

Claim 13

A method according to any one of claims 8 to ll, characterised in that the predetermined shift parameters of the shift controller (270) include a predetermined fill time during which the torque-establishing device (28 to 32) associated with the upper speed ratio mechanism is filled in preparation for activation, and the adjustment of the predetermined shift parameters comprises the step of shortening the predetermined fill time for the impending upshift to the upper speed ratio.