In an automotive vehicle, a shift in speed position is suppressed by increasing a hysteresis amount in vehicle speed between an shift-up vehicle speed and a shift-down vehicle speed when a periodic variation in engine output is effected under the control of a slip control unit, or by inhibiting a downshift for a predetermined length of time during the periodic variation in engine output effected under the control of the slip control unit.
A shift control apparatus for an automatic transmission eliminates or reduces a sense of discomfort to the driver and other occupants during slip, while maintaining the necessary driving force. When slip is determined by detection of wheel speed, a slip signal is output. A controller which receives the slip signal outputs a maintaining signal for maintaining the gear stage which existed at the time the slip signal was received, until a predetermined period of time has passed. If the slip continues after the predetermined period of time, the controller outputs a shift signal to the automatic transmission to shift it to a predetermined gear stage, thus reducing driving force and preventing slip from continuing. If the slip stops within the predetermined period of time, the slip signal is canceled such that the current gear stage is maintained and no shift is executed.
A gear shift control system according to this invention includes a throttle opening sensor, a vehicle speed sensor and a controller for delivering a shift command signal to an automatic transmission. The controller is previously stored with shift lines, which divide the respective regions of gear-shift stages, on the basis of the throttle opening and the vehicle speed. The controller delivers the shift command signal to the transmission when any of the shift lines is crossed by a shift point which is defined by the throttle opening and the vehicle speed. Taking account of the changing rate of the throttle opening, the past throttle opening, and the acceleration of the vehicle, however, the controller calculates a decision value which is indicative of the running state of the vehicle, on the basis of the fuzzy theory. When the decision value exceeds a predetermined value, the controller corrects the shift lines depending on the running state.
A gear-shift control system of an automatic transmission, in which gear shift schedule is appropriately changed-over in correspondence with the change of a road surface situation. Low-friction road surface detection device detects a low-friction road surface so as to select the gear shift schedule for the low-friction road surface adopted to start the motor vehicle with second gear. After the selection, a holding device holds the gear shift schedule for the low-friction road surface until an accelerator is pressed next.
In an automatic transmission control system provided for an internal combustion engine having an automatic transmission system equipped with a traction control system in which a throttle valve is adjusted towards a closed state from a throttle position corresponding to an operation of an accelerator pedal when wheel slippage occurs, a detection unit detects a degree of operation of the accelerator pedal. A shift point changing unit changes a shift point so that gear shifting occurs on the basis of the degree of operation of the accelerator pedal in a normal state and gear shifting occurs at an engine speed lower than a predetermined engine speed at which gear shifting normally occurs when the degree of operation of the accelerator pedal is equal to or greater than a predetermined value.
The invention is based on a motor vehicle having a drive unit (101) and a transmission (103) which is operatively connected to the drive unit by way of a converter unit (102) and which automatically changes its step-ups, whereby at least two wheels (104) of the motor vehicle are driven. For the purpose of gear detection in accordance with the invention, the mean velocity (Vrad) or the mean rotational speed of the driven wheels is detected and/or ascertained, and the output rotational speed N(Nmot) of the drive unit is detected. Furthermore, a variable (Nmot/Vrad), representing the ratio of the output rotational speed of the drive unit to the mean wheel velocity or the mean wheel rotational speed, is formed. This variable is then compared with at least two threshold values ((Sup, Sdown), wherein change-up or change-down operations of the transmission are inferred from the comparison result. With knowledge of change-up or change-down operations, the step-up of the transmission (Gi) actually set may then be inferred on the basis of the step-up set before the comparison.
