Abstract: A hydraulic control system of an automatic transmission for a vehicle which includes a pressure regulator for regulating hydraulic pressure created by an oil pump, manual and automatic shift controllers for forming a shift mode according to a position of a shift selection lever, a hydraulic controller for controlling shift quality and shift response to smoothly change transmission speeds when shifting, and a hydraulic pressure distributor and release mechanism which distributes an appropriate amount of hydraulic pressure to and releases pressure from each of the friction elements in the automatic transmission, A hydraulic distribution and release device has a 2-4/3-4 shift valve, a 2-3/4-3 shift valve, and an end-clutch valve for supplying to or releasing from friction elements hydraulic pressure.

Abstract: An automotive automatic transmission has an input shaft receiving a rotational force from an engine, an output shaft for outputting a rotational force to a vehicle driving wheel, a frictional engagement device having an adjustable engagement condition, and a transmission device for transmitting a rotational force from the input shaft to the output shaft at a gear speed ratio depending on the engagement condition of the frictional engagement device. A control apparatus for the automotive automatic transmission includes an engagement condition adjusting device for adjusting the engagement condition of the frictional engagement device by feeding a hydraulic pressure thereto in response to an instructed control amount.

Abstract: In an automatic transmission including a gear unit with a second brake connected in series with a one-way clutch and a first brake that is not connected with a one-way clutch, the second brake and the first brake are controlled by linear solenoid valves individually. A vehicle load is detected, and when the vehicle is in a high load state, at first the second brake performs an engagement control, then after input rotation to the gear unit is synchronized with output rotation of the gear unit, the first brake performs an engagement control. When the vehicle is in a low load state, at first the first brake performs an engagement control, then after input rotation to the gear unit is synchronized with output rotation of the gear unit, the second brake performs an engagement control.

Abstract: A torque responsive hydraulic control system for an automatic transmission with a plurality of hydraulically actuated friction control elements. A working hydraulic pressure in the elements is controlled during shifting such that a pressure in a first element is removed after a specific state of the element is achieved. The removal being responsive to the torque of an input shaft of the transmission, the expiration of a specific time period, or a position of the throttle valve of a driving engine.

Abstract: An up-shift control apparatus includes an engine racing detecting means for detecting engine racing during an up-shift and an engine racing preventing means. The up-shift control apparatus is installed to an automatic transmission which executes the up-shift by disengaging a first friction element and by engaging a second friction element. The engine racing preventing means outputs a command signal to a valve actuator to temporally increase an engagement force of the first friction element when the engine racing is detected during the up-shift.

Abstract: A gear shift control apparatus for use in an automatic transmission having friction elements each of which is operable on a working fluid pressure applied thereto in an engaged and released state. A change is produced from the current gear ratio to a desired gear ratio by increasing the pressure of the working fluid to a first one of the friction elements at a first rate to engage the first friction element while decreasing the pressure of the working fluid to a second one of the friction elements at a second rate to release the second friction element. A time elapsed for a torque phase in the gear ratio change is measured. The first rate is decreased when the measured torque phase time is shorter than a predetermined value. The second rate is increased when the measured torque phase time is longer than the predetermined value.

Abstract: A control for shifting from an off-going speed range to an on-coming speed range comprises an off-going range releasing stage, an on-coming range void-stroke-clearing stage, an on-coming range engaging stage and an on-coming range final stage. During the off-going range releasing stage, an off-going engaging element is released in response to a shift command signal. During the on-coming range void-stroke-clearing stage, the engagement-actuation pressure of the on-coming engaging element is set at a predetermined high-pressure for a predetermined time period after the shift command signal is generated, whereby the void stroke of the on-coming engaging element is cleared. During the on-coming range engaging stage, after the completion of the on-coming range void-stroke-clearing stage, the on-coming engaging element is engaged. During the on-coming range final stage, following the on-coming range engaging stage, the on-coming engaging element is engaged completely.

Abstract: In order to precisely determines the time to start feedback control of line pressure during a shifting period, a shift control computer calculates an effective gear ratio Ge=Nt/Nos at the time of an shift instruction based on input shaft rotational speed Nt and detected vehicle speed Nos and then calculates a parameter F=Nos.times.Ge-Nt indicating the point to start feedback control based on the input shaft rotational speed Nt, the detected vehicle speed Nos and the effective gear ratio Ge. By comparing the calculated parameter F with a predetermined value .DELTA.Nt, hydraulic pressure at the start of shift operation is maintained if F<.DELTA.Nt and, if F.gtoreq..DELTA.Nt, feedback control is performed to cause the input shaft rotational speed Nt to vary in a predetermined manner.

Abstract: A control system of an automatic transmission includes a torque converter, a lock-up clutch for directly connecting input and output members of the torque converter, a pressure control valve which changes a hydraulic pressure to control an engaging force of the lock-up clutch, and a pressure regulator, disposed in an engaging passage, which supplies hydraulic pressure to engage a frictional element. The pressure regulator adjusts a primary pressure and produces an output hydraulic pressure corresponding to a control pressure introduced into a control port of the pressure regulator. A control pressure supply device is provided for introducing the control pressure, controlled by the pressure control valve, into the control port of the pressure regulator. The number of parts can be reduced without producing any inconvenience.

Abstract: An apparatus for controlling an automatic transmission of a motor vehicle which is shifted to a non-drive position with a releasing action of a hydraulically operated frictional coupling clutch upon operation of a manually operated member from a drive position to a non-drive position, the apparatus including a non-drive shift detecting device for detecting a non-drive shifting operation of the manually operated member from the drive position to the non-drive position, a rapid pressure reduction device operated upon detection of the non-drive shifting operation for rapidly reducing a pressure of the hydraulically operated frictional coupling device to a predetermined pressure level, and a continuous pressure reduction device for continuously reducing the pressure of the frictional coupling device from the predetermined pressure level at a predetermined reduction rate.

Abstract: A control system for an automatic transmission includes: a clutch adapted to be applied when a forward running range is selected, to transmit the rotation of an engine to the transmission mechanism of a speed change unit and a hydraulic servo for applying/releasing the clutch. A control unit controls oil pressure fed to the hydraulic servo and includes: an application starting pressure detector for detecting application starting pressure at the instant when the application of the clutch is started; an initial application pressure setter for setting an initial application pressure on the basis of the detected application starting pressure; and an oil pressure regulator for adjusting the oil pressure fed to the hydraulic servo, when a change is made to a forward running range, and then gradually raising that oil pressure.

Abstract: A control system for an automatic transmission having friction coupling elements, at least one of which is locked in 3rd and 4th gears and unlocked in 1st and 2nd gears, includes a first shift valve shiftable between 3rd and 4th gears, and second shift valve shiftable between in 2nd gear and 1st gear in which engine brake available, and a solenoid valve providing control pressure which is selectively directed to these shift valves and cause them to shift so as to lock or unlock the friction coupling elements.

Abstract: A power train controller and control method are provided for a passenger car driven by a combustion engine and an automatic gear changing transmission. Control sensors detect a current operating state of the passenger car. Three different modes of operation, including sports mode, economy mode, and comfortable mode are selected by the driver. Depending on the selected mode, the automobile transmission is controlled in different shifting patterns as a function of the sensed vehicle operating conditions.

Abstract: A method of establishing an adaptive pressure term in an automatic transmission having a pressure command developed from a base line pressure term and an adaptive pressure term extends implementation of adaptive pressure corrections during non-ideal periods of operation such as low temperatures, short operating cycles and driver variations by establishing an adaptive pressure term proportional to a measure of confidence in a pressure correction term calculated at each ratio change of the transmission. The measure of confidence is determined according to a variety of functions of predetermined powertrain operating parameters and measures of criticality.

Abstract: A shift control system for an automatic transmission to execute a clutch-to-clutch shift by applying a first frictional engagement device and releasing a second frictional engagement device and another shift by applying the first frictional engagement device to cause a rotational change in a predetermined rotary member. At a shift other than the clutch-to-clutch shift, there is detected a stroke time from the feed of an oil pressure to the first frictional engagement device to the start of the engagement. At the clutch-to-clutch shift, the timing for releasing the second frictional engagement device is controlled on the basis of the stroke time.

Abstract: A process is proposed for controlling an automatic transmission wherein a transition occurs from a first, lower reduction step to a second, higher reduction step when a first clutch disengages and a second clutch engages and a synchronizer speed is calculated by multiplying the transmission output speed by the reduction ratio of the second reduction step. A speed value, at which the pressure increase of the second clutch begins, is assigned to the synchronizer speed from a characteristic curve. The characteristic curve is adapted if the transmission input speed exceeds the synchronizer speed or if the gradient of the transmission input speed exceeds a limit value.

Abstract: A shift control method for executing a shift-up control from an off-going range to an on-coming range comprises an off-going-range releasing stage, an off-going-range controlling stage, and an on-coming-range invalid-stroke-clearing stage. In the off-going-range releasing stage, a pressure command signal is generated to quickly lower the engagement-actuation pressure of the off-going engaging element. In the off-going-range controlling stage, a pressure command signal is generated to control the engagement-actuation pressure of the off-going engaging element in such a way that the off-going engaging element is kept slipping within a predetermined range of input/output rotational speed ratio (=output rotational speed/input rotational speed).

Abstract: A system for controlling a vehicle automatic transmission, in which a gear ratio to be shifted to is determined based on the vehicle speed and throttle opening degree and a clutch is supplied with hydraulic pressure such that the rotational speed of the transmission input shaft concurs with a desired rotational speed change rate. The system includes means for discriminating whether the engine load fluctuates and the operation is discontinued when it is discriminated that the engine load fluctuates. Specifically, even when the accelerator pedal is operated only somewhat rapidly and the engine output is able to follow the change in the degree of throttle opening, the degree of throttle opening nevertheless differs between that at the start of gearshift and that in the course of gearshift thereafter, causing unexpected gearshift shock to occur. The arrangement can solve the problem.

Abstract: An automatic transmission includes the transmission control device which sets a control time upon changeover from the second gear condition to the third gear condition during which the brake device is maintained in the engaged condition until changing to the disengaged condition. The transmission control device also adds a compensating time to the control time upon changeover from the second gear condition to the third gear condition in certain circumstances such as when changeover from the second gear condition to the third gear condition follows operation under the first gear condition, and when change over from the second gear condition to the third gear condition follows vehicle operation under the second gear condition for a period exceeding a predetermined time (e.g., 10 seconds).

Abstract: A control system for an automatic transmission includes a clutch for transmitting the rotation of an engine to the transmission and a hydraulic servo for applying/releasing the clutch. A starting state is determined by satisfaction of at least one of the following conditions: the throttle opening is not fully closed; the brake pedal is released; and/or the vehicle speed is substantially above zero. Sensors detect the throttle opening of the engine and the applied/released state of the clutch and send signals to a control unit. A hydraulic controller controls the oil pressure fed to the hydraulic servo. When the starting state is detected, the control unit detects the actual applied/released state of the clutch to determine the difference between the applied/released state and a predetermined ideal applied/released state to set an oil pressure correction according to that difference.

Abstract: Detecting means for detecting driving conditions of a vehicle such as engine load such as throttle opening, vehicle speed, gear position or gear ratio and so on and memory means for storing characteristics of the vehicle such as engine power characteristic, torque converter characteristic, fuel consumption rate characteristic and so on are provided. Driving shaft torques before and after gear shift, an estimating value of fuel consumption rate and a gear shift point of a transmission are calculated in real time to perform transmission control using the signals from said detecting means and the signals from said memory means. With the construction according to the present invention described above, an automatic transmission can be controlled in real time by calculating a gear shift point of the transmission in a short time through estimating the driving shaft torques before and after gear shift.

Abstract: In machines such as hauling units having electro-hydraulic transmission controls, it is desirable to ensure that in the event of an electrical malfunction or power failure the transmission remains in one of its gear ratios. In the subject invention, a dependent latching system is provided in a transmission which in the event of an electrical malfunction latches the transmission in the existing gear ratio or a gear ratio within at least two gears ratios. This is accomplished by providing a master latch valve mechanism, a logic valve arrangement, and a latching shuttle valve to act in cooperation with an electrically controlled proportional valve and a hydraulic proportional valve that controls engagement of a plurality of hydraulically actuated clutches. The master latch valve mechanism directs pressurized fluid from a source of pressurized fluid through the logic valve to urge the latching shuttle valve to an open position.

Abstract: A control unit 11b which consists of a microcomputer compensates the detected intake manifold pressure Pb with an atmospheric pressure, obtains a first estimated position of the throttle when the amount of by-pass air is null and a second estimated position of the throttle when the mount of by-pass air is the maximum from the intake manifold pressure compensated with the atmospheric pressure and the detected revolution speed Ne, obtains the ratio of the amount of by-pass air currently under control to the maximum controllable amount of by-pass air, estimates the position of the throttle from the ratio and the first and second estimated positions of the throttle, and collates the estimated position of the throttle after compensation and the detected vehicle speed V.sub.s with the speed change map to shift the gear of the automatic transmission 3.

Abstract: A control system for an automatic transmission for a vehicle provides an enhancement in a shifting characteristic in a manually shifting mode by controlling an operating hydraulic pressure for hydraulic engage elements in an appropriate manner. In a first range from the output of a shifting command to a time point when a timer TOIPU reaches a counting-up value, or a time point when the slip rate ECL of the hydraulic engage elements exceeds a value YECLIPUS, the operating hydraulic pressure is set at a preset value depending upon the type of shifting. In a second range from the end of the first range to a time point when the timer TOIPU reaches a counting-up value, or a time point when a slip rate ECL exceeds a value TECLIPUS, and in a third range from the end of the second range to a time point when a timer TKAK reaches a counting-up value, the operating hydraulic pressure QAT is set at a value corresponding to an engine torque or a transmission input torque.

Abstract: An automatic transmission gear shift control system controls a transitional pressure level during a gear shift according to engine output conditions and correctively changes a rate at which the transitional pressure changes according to a time difference between an actual gear shift time and a target gear shift time when an engine output is less than a specified level. If the corrected rate is greater than a specified rate, then the transitional pressure level is increased. According to the control system, even when a drop in the transitional pressure does not cause a change in shifting time, a shifting time learning control is properly conducted.

Abstract: A degree of sporty driving, or degree of load on tires of a vehicle, is detected based on a usage degree of tire performance. A horizontal force exerted on a tire is calculated and estimated based on longitudinal acceleration and lateral acceleration. Then a ratio, of the horizontal force to a maximum limit gripping force of the tire, is determined to enable detection of the load on a tire at all times.

Abstract: A hydraulic control system of an automatic transmission during a shift operation wherein a control pressure is controlled to selectively engage and release a plurality of frictional elements to establish a desirable shift stage comprising inertia phase detecting device for detecting a starting point of an inertia phase of the shift operation from one shift stage to another, and control pressure reducing device for gradually reducing the control pressure introduced to a frictional element to be engaged after the inertia phase is detected. The torque shock in the shift operation can be effectively reduced.

Abstract: A power train controller and control method are provided for a passenger car driven by a combustion engine and an automatic gear changing transmission. Control sensors detect a current operating state of the passenger car. Three different modes of operation, including sports mode, economy mode, and comfortable mode are selected by the driver. Depending on the selected mode, the automobile transmission is controlled in different shifting patterns as a function of the sensed vehicle operating conditions.

Abstract: The present invention provides a sensing system and method for providing information relating to a drivetrain during shifting operations. The drivetrain includes an engine, a torque converter and a transmission. The system includes sensors for detecting the output speed of the engine, the output speed of the torque converter, and the output speed of the transmission. The system detects the starting condition of a shifting operation, responsively determines a set of performance parameters, and produces a set of performance parameter signals.

Abstract: A five-speed parallel-shaft clutch-to-clutch shifting automatic transmission has an hydraulically responsive clutch priority valve effective to exhaust fluid pressure from lower priority clutches upon undesirable simultaneous application two or more clutches. Two clutches associated with numerically nonadjacent gear ratios are supplied fluid pressure from a single solenoid controlled fluid valve vis-a-vis a two mutually exclusive state multiplex valve. The clutch priority valve is interposed between the solenoid controlled fluid valve and the multi-plex valve thereby rendering the two clutch states associated with the single solenoid valve indistinguishable by the clutch priority valve.

Abstract: Detecting means for detecting driving conditions of a vehicle such as engine load such as throttle opening, vehicle speed, gear position or gear ratio and so on and memory means for storing characteristics of the vehicle such as engine power characteristic, torque converter characteristic, fuel consumption rate characteristic and so on are provided. Driving shaft torques before and after gear shift, an estimating value of fuel consumption rate and a gear shift point of a transmission are calculated in real time to perform transmission control using the signals from said detecting means and the signals from said memory means. With the construction according to the present invention described above, an automatic transmission can be controlled in real time by calculating a gear shift point of the transmission in a short time through estimating the driving shaft torques before and after gear shift.

Abstract: A method of selecting a pinion for a vehicle speedometer system uses a transmission output speed sensor and a transmission controller which applies a pinion factor to the signal from the sensor to generate an output signal representing the speed of the vehicle.

Abstract: An arrangement for controlling an automatic selector device of a change-speed gearbox has two selecting connections engageable alternately by selecting actuators operated by pressure medium can be actuated into two non-transient and two transient selector conditions. This alternate engageability is provided by an electronic control unit by way of just one electromagnetic control valve. The arrangement also uses three pressure systems and two multi-way valve arrangements.

Abstract: A control system for an automatic transmission is constructed so that when failing to detect an operation of skid reduction control, an optimum hydraulic pressure value is determined based on a basic line pressure determined by throttle opening degrees, etc. and a correction value thereof, and an optimum hydraulic pressure signal is provided to a hydraulic pressure adjusting actuator. At this time, the correction value is modified so that a shift time upon current shift approaches a reference shift time. On the other hand, when detecting an operation of skid reduction control, at least modification of the correction value is prohibited.

Abstract: An automobile automatic transmission shift control system causes a specific gear shift by locking a first frictional element and unlocking a second frictional element simultaneously. The system delays a commencement of the unlocking of the second frictional element relative to a commencement of the locking of the first frictional element during the specific gear shift while a down control of engine torque is not conducted or when an engine output torque is large.

Abstract: The present invention relates to an adaptive control method for an automatic transmission. The method includes the steps of:(a) commanding a predetermined clutch to fill in accordance with a plurality of clutch fill parameters;(b) determining the actual time to completely fill the clutch;(c) comparing the actual fill time with a predetermined fill time; and(d) adjusting at least one of the plurality of clutch fill parameters in response to the comparison in order to modify the clutch fill period during subsequent shifts to the predetermined clutch. Accordingly, the present invention adapts future shifts based on past shifts to improve the shift quality of the transmission.

Abstract: A method for control of a preferably electro-hydraulically activated automatic transmission of a motor vehicle equipped with an internal combustion engine provides for prevention of upshifting, i.e. reduction in translation in and before a curve. The upshift prevention is initiated if pressure is removed quickly from the gas pedal in idle operation. The upshift prevention is cancelled if the vehicle does not drive through a curve after elapse of a certain time period after traction operation is recognized. If idle operation is again recognized during elapse of the time period, the upshift prevention is maintained for another time period. After termination of the upshift prevention, step by step adjustment of the gear level to the value determined by the shifting characteristic field takes place.

Abstract: A shift control system of an automatic transmission includes a first element which is to be released in a shift operation, a second element which is to be engaged in the shift operation, and a target shift time set section for setting a target time period of the shift operation needed for releasing the first frictional element and engaging the second frictional element. A shift time calculation section is provided for obtaining an actual time period of the shift operation needed for releasing the first frictional element and engaging the second frictional element, and a releasing pressure control section is provided for receiving output of the target shift time set section and the shift time calculation section for controlling a releasing pressure of the first frictional element in the shift operation based on the difference between the target and actual time periods of the shift operation.

Abstract: A hydraulic control system of a four-speed automatic transmission whereby second-to-fourth skip shifting or fourth-to-second skip shifting is possible. Line pressure is controlled variably to improve the power train efficiency and the response of shifting time during gear shifting. The exhaust port of the pressure control valve, which is controlled by the line pressure varying solenoid valve according to a duty ratio, is selectively opened to control line pressure. First and second pressure control solenoid valves are controlled according to a duty ratio such that the shift valves are controlled by drive pressure and speed line pressure.

Abstract: A hydraulic control system for 4-speed automatic transmission which is controlled by torque control hydraulic pressure in regular succession and can provide a skip shift comprises a fluid pump (32), a pressure regulator valve (34) for regulating the line pressure generated at the fluid pump (32), a plurality of frictional elements (108, 62, 120, 84, 94, 100, 126) actuated by drive hydraulic pressure or reverse hydraulic pressure in accordance with the position of a valve spool of a manual valve (58), a first transmission control portion (D) having at least two valves (78, 86, 98) for supplying hydraulic pressure to at least one of the frictional elements, and a second transmission control portion (E) for selecting at least one of the frictional elements.

Abstract: A diagnostic strategy for an automatic transmission having electronic shift control solenoids for controlling application and release of clutches and brakes during the establishment and disestablishment of torque ratios in multiple-ratio gearing for the transmission wherein provision is made for developing diagnostic data that detects failure modes due to a faulty shift solenoid by using predetermined failure modes stored in the RAM portion of a microprocessor and comparing those known failure modes to the actual performance of the shift solenoids.

Abstract: A control system (104)/method for a vehicular automated mechanical transmission is provided, which will compare input signals indicative of input shaft speed (IS) to the product of input signals indicative of output shaft speed multiplied by engaged gear ratio (OS*GR) to develop control parameters indicative of drivetrain torque magnitude and/or phase requiring a driveline torque transducer.

Abstract: A system and method for controlling the bypass clutch of an automatic transmission includes an electronic microprocessor, an electronic memory accessible to the microprocessor, solenoid-operated bypass valve, pressure actuated bypass clutche, a variable force solenoid-operated bypass valve, a torque converter bypass friction clutch, and control algorithms that produce output signals to control the state of the solenoid-operated valve. The vehicle speed at which the bypass clutch engages and disengages, according to a reference schedule, is compensated for loss of engine torque at conditions that differ from the conditions at which the reference schedule is defined. Vehicle speed is compensated for torque variation with reference to the ratio of current calculated engine torque divided by current engine output torque.

Abstract: In one aspect of the present invention, an electronic shift control for a powershift transmission is disclosed. The transmission includes a plurality of speed and direction changing clutches. A plurality of pressure control valves are individually connected to the clutches. A hydraulic pump delivers pressurized hydraulic oil to predetermined pressure control valves to meter hydraulic fluid in response to receiving a clutch command signal. The method produces a shift from a first transmission ratio to a second transmission ratio through disengagement of an off-going clutch associated with the first transmission ratio and engagement of an on-coming clutch associated the second transmission ratio. The method includes filing an on-coming speed clutch, releasing an off-going direction clutch in response to the on-coming speed clutch being filled, and thereafter, gradually increasing the on-coming speed clutch pressure to engage the speed clutch.

Abstract: The invention is directed to a method for adjusting the hydraulic pressure actuating at least one clutch of an automatic transmission. The hydraulic pressure is pregiven only by one pressure controller and the automatic transmission coacts with the motor which is especially a drive motor of a motor vehicle. The pressure supplied by the pressure controller is determined in dependence upon the trace of a pregiven motor desired torque.

Abstract: An automatic transmission having multiple-ratio gearing, fluid pressure-operated clutches and brakes adapted to establish and to disestablish multiple torque ratios and electronic shift control solenoids that can be energized and de-energized under the control of an electronic microprocessor that senses transmission operating variables, and a control strategy inherent in the microprocessor that uses predetermined failure modes to perform functional testing on the shift solenoids without special hydraulic and electronic hardware for developing the diagnostic information that detects shift solenoid failures or malfunctions.

Abstract: An automatic transmission shift control system calibrates a locking speed, which is regulated by a regulating valve and at which locking of a specific frictional element is performed so as to shift an transmission gear mechanism to a specific gear, in accordance with a deviation of an input speed of rotation to the transmission from a specified input speed of rotation while shifting the transmission to the specific gear. The system further varies the calibration according to a transitional period of time which is defined from a completion of shifting to a preceding gear from which the transmission is shifted directly to the specific gear to a commencement of shifting to the specific gear subsequently to the shifting to the preceding gear.

Abstract: The present invention provides improved initial shift quality in an electronically controlled automatic transmission by enabling the friction element fill volumes to be "learned" by the transmission controller before the vehicle leaves the assembly line. An end of line (EOL) volume learn procedure is intended for final check out at car assembly or for other appropriate circumstances such as for service after a transaxle has been rebuilt or replaced, or as a diagnostic tool to help confirm an indicated condition of an element.Upon satisfaction of a set of initial conditions, an end of line volume learn procedure is initiated wherein the transmission is cycled through a number of phases, each phase generally corresponding to the application of a different friction element.

Abstract: A control for a motor vehicle drive having an automatic transmission includes a circuit configuration for generating an output signal adapting shifting points to a load state of the motor vehicle from an evaluation of a power takeoff rpm of the transmission or of a variable equivalent to it. The circuit configuration ascertains a deviation between a calculated and a measured power takeoff rpm in successive time intervals and forms a correction term by multiplication with a factor. At least one characteristic curve memory stores shifting points of the transmission. The at least one characteristic curve memory receives the correction term as an output signal for adapting a characteristic curve to the load state. In a method for controlling a vehicle drive having an automatic transmission, shifting points or characteristic curves for shifting are varied as a function of driving parameters.

Abstract: A speed change control method and apparatus for a vehicular automatic transmission having a first-speed clutch for establishing a first speed and a second-speed clutch for establishing a second speed, includes subjection of at least a duty ratio Dr of a second-speed solenoid valve for supplying oil pressure to the second-speed clutch to feedback control, so that the first-speed clutch is engaged while disengaging the second-speed clutch. This thereby increases a turbine rotational speed Nt toward the first-speed synchronous rotational speed. Further, an upper limit value Dmax of the duty ratio Dr is set, and the duty ratio Dr is subject to feedback control within a resultant duty ratio range. This thereby prevents the duty ratio Dr from being set at an excessive value caused by a delay in the rise of the oil pressure. As a result, even if a depression of an accelerator pedal is suddenly increased during a downshifting process, an interlock problem can be prevented, thereby ensuring smooth speed change.