Abstract: A vehicle control device includes a processor and memory. The memory stores relation-defining data for defining a relation between a state of a vehicle and an action variable that is a variable relating to operations of a transmission installed in the vehicle. The processor is configured to execute acquisition processing, operation processing, reward calculation processing, updating processing, counting processing, and limiting processing. The processor is configured to output the relation-defining data updated so that an expected income is increased when the transmission is operated following the relation-defining data, based on an updating map.

Abstract: A method for operating a motor vehicle drivetrain having a transmission connected between a drive aggregate and a drive output, a Power Take-Off (PTO) that can be coupled to the drive aggregate on drive aggregate side to take up drive torque from the drive aggregate. In order to determine the torque taken up by the PTO, the transmission is first shifted to interrupt torque to the transmission output. Thereafter, a defined torque is delivered by the drive aggregate, at least with the PTO coupled to the drive aggregate, and, during this at defined time-points, rotational speeds of a shaft driven by the drive aggregate are determined and from this an angular acceleration of the shaft is determined. A first torque of the shaft is determined from the shaft angular acceleration while the PTO is coupled. Based on the first torque, the torque taken up by the PTO is determined.

Abstract: A transport apparatus includes: a driving source; an output shaft; and a power transmission device capable of performing power transmission between the driving source and the output shaft. The transport apparatus comprises a control device which controls the driving source and the power transmission device, wherein the power transmission device includes a connecting/disconnecting unit configured to control a fastened state in which the power transmission is performed, and a released state in which the power transmission is not performed, and wherein the control device controls the connecting/disconnecting unit based on a thermal history of the connecting/disconnecting unit.

Abstract: A control device that controls a vehicle transmission device including an input drivingly coupled to an internal combustion engine, an output drivingly coupled to wheels, a shift input drivingly coupled to the input via a fluid coupling having a lock-up clutch, and a speed change mechanism disposed on a power transmission path connecting the shift input and the output, wherein the speed change mechanism is capable of performing both continuously variable shifting that continuously changes a speed ratio, and stepped shifting that changes a speed ratio in a stepwise manner, the control device including: an electronic control unit that is configured to perform, when the stepped shifting is performed, rotation maintained engagement control that controls an engagement pressure of the lock-up clutch such that a rotational speed of the input follows a predetermined target rotational speed, regardless of a change in rotational speed of the shift input.

Abstract: A resilient electrical connector assembly includes a base PCB and stacked layers of interconnected resilient conductive structures where each structure has at least two resilient conductive strips and at least two conductive contacts. One contact is integrated with a conductive path on the base PCB and another contact pad is positioned to establish a conductive path with a target PCB when the latter is mounted parallel to the base PCB. The resilient conductive strips flex due to a compressive force exerted between the base PCB and target PCB on the stacked layers. The resilient conductive structures are formed by depositing metal to sequentially form each of the stacked layers with one contact being initially formed in engagement with the conductive path on the base PCB.

Abstract: A control device of an automatic transmission that controls the automatic transmission including a friction engagement element capable of continuously changing a transmission torque includes: a first heat load estimation unit configured to estimate a heat load state in the friction engagement element based on an indication value of the transmission torque; and an estimation stop unit configured to stop the estimation of the heat load state based on a state where the indication value of the transmission torque differs from an actual value of the transmission torque actually transmitted by the friction engagement element.

Abstract: A method for terminating a gearshift for an automatic transmission for a motor vehicle is provided, wherein a positive-locking shifting element is involved. After the initiation of the gearshift, there is an evaluation of the continuous signals of at least one control unit of the vehicle, which affect the engine torque and thus the turbine speed gradient. Based on the evaluation of the signals, an upcoming change to the turbine speed gradient that exceeds a first predetermined threshold value or falls short of a second predetermined threshold value is detected, and, upon such detection, the gearshift is terminated.

Abstract: A torque converter includes an input connected to an engine. An output is connected with a transmission. A lockup clutch is connected with the output and is disposed to engage the input to couple the input with the output via an apply pressure corresponding to a target lockup strategy based on at least one vehicle operating condition. A pressure regulator is configured to modulate the apply pressure. Systems and methods are disclosed.

Abstract: A clutch control unit includes a clutch motor controller that controls a clutch motor. The clutch motor controller has a target clutch motor current computing unit that computes a target clutch motor current for adjusting torque of the clutch motor to be torque corresponding to an operating state of the vehicle, and a motor driving and braking selection unit that selects a motor driving mode in which the clutch motor is driven by applying feedback control on an output of the clutch motor or a motor braking mode in which the clutch motor is braked by short-circuiting the clutch motor according to a difference between the target clutch motor current and an actually detected clutch motor current. It thus becomes possible to provide a control system of a transmission that engages a clutch by a motor braking force in a manner that suits the running state of the vehicle.

Abstract: A powertrain system includes an electric machine mechanically coupled to an internal combustion engine mechanically coupled to a transmission. A method for operating the powertrain system includes determining an engine stall threshold rate during engine operation in a low load condition. A time-rate change in an accessory load is controlled by the electric machine operating in an electric power generating mode in response to the engine stall threshold rate during the engine operation in the low load condition.

Abstract: The invention relates to a controller for a vehicle having installed thereon a drive power source, a transmission, and a torque converter that is equipped with a lockup clutch and is provided between the drive power source and the transmission. The controller includes a detection unit that detects an actual revolution speed of the drive power source, and a control unit that controls the lockup clutch so that a state of the lockup clutch becomes any state from among a disengaged state, an engaged state, and a slip state. When executing a slip control, the control unit compares the actual revolution speed with the target revolution speed, and feedback controls a transmission torque of the lockup clutch on the basis of a comparison result of the actual revolution speed and a target revolution speed so as to cause the actual revolution speed to follow the target revolution speed.

Abstract: Provided is a device for performing speed change not leading to engine stall in a working vehicle such as a wheel loader while sustaining a required tractive force and reducing fuel consumption. When a speed (“forward”, “second speed”) suitable for a work is selected by a speed change operator, control means makes a modulation clutch engaged in response to the vehicle speed drop and makes a lock-up state where a lock-up clutch is engaged transit to a lock-up and modulation clutch slip state where the lock-up clutch is engaged while the modulation clutch slips. Subsequently, the control means performs a clutch control for causing a transition to both clutch slip state where the lock-up clutch and the modulation clutch slip in response to the vehicle speed drop, hence causing the transition to a torque converter operation state where the modulation clutch is engaged and the lock-up clutch is released.

Abstract: When a downshift is performed while a vehicle travels in a coasting state, a determination is made as to whether or not a fuel cut recovery will be performed. When a fuel cut recovery will be performed, an offset oil pressure is set and an initial oil pressure set after raising an oil pressure of an engagement side frictional engagement element to a pre-charge oil pressure is set at an oil pressure obtained by subtracting the offset oil pressure from a reference initial oil pressure.

Abstract: A control device for an automatic transmission for a vehicle including a torque converter interposed between an output shaft of an engine and an input shaft of the automatic transmission, the torque converter having a lock-up clutch for mechanically connecting the output shaft and the input shaft in a direct manner, and a lock-up clutch engagement control unit for engaging the lock-up clutch by a predetermined engagement force in a predetermined operational region determined by a throttle angle and a vehicle speed. The control device further includes a shift map having a slip region for the lock-up clutch set in relation to a plurality of shift characteristics preliminarily set according to vehicle speeds, the slip region being defined by a downshift line and a slip start line deviated from the downshift line by a predetermined range of throttle angle toward lower throttle angles.

Abstract: A system and method for providing TCC control and/or transmission gear shift control by considering the rate of change of the accelerator pedal or throttle position. The method determines whether the rate of change of the throttle position exceeds a predetermined positive rate of change or a predetermined negative rate of change and, if so, releases the TCC to provide TCC control. Alternatively, or additionally, the method can provide a transmission gear down-shift or up-shift depending on which direction the throttle position is changing. Once the TCC and/or gear shift control has been initiated, the method can start a timer and then return to normal TCC and/or gear shift control after the timer has expired. The TCC and/or gear shift control can also return to normal if the rate of change of the throttle position indicates that the throttle is being returned to its previous position.

Abstract: A torque converter lockup clutch control system is provided for an associated automatic transmission. The system includes a torque converter having an impeller operatively coupled to an associated internal combustion engine and a turbine operatively coupled to an input shaft of the associated automatic transmission. A lockup clutch is disposed within the torque converter for selectively locking the impeller to the turbine. A pressure regulator is operatively coupled to the torque converter for adjusting the pressure of a working fluid to at least one shift clutch of the associated automatic transmission in response to a speed differential between the impeller and turbine of the torque converter. A shift clutch slip detector is provided for detecting a slip condition of the at least one shift clutch of the associated automatic transmission and outputs a slip value.

Abstract: A system and method for providing TCC control and/or transmission gear shift control by considering the rate of change of the accelerator pedal or throttle position. The method determines whether the rate of change of the throttle position exceeds a predetermined positive rate of change or a predetermined negative rate of change and, if so, releases the TCC to provide TCC control. Alternatively, or additionally, the method can provide a transmission gear down-shift or up-shift depending on which direction the throttle position is changing. Once the TCC and/or gear shift control has been initiated, the method can start a timer and then return to normal TCC and/or gear shift control after the timer has expired. The TCC and/or gear shift control can also return to normal if the rate of change of the throttle position indicates that the throttle is being returned to its previous position.

Abstract: An electromechanical power transfer system for a vehicle, comprises: an electrical power source; a system controller; at least two dynamoelectric machines; an electrically engageable clutch for each machine; an input shaft coupled to the jack shaft; an output shaft coupled to a load presented by the vehicle; and at least two electrically engageable transmission gear sets for coupling the input shaft to the output shaft; wherein the system controller selectively engages each machine clutch and each transmission gear set.

Abstract: The input rotation speed of an automatic transmission is fixed, and an output shaft is fixed. Oil pressure supplied to a measurement subject engagement element is then increased, and a determination is made as to whether or not rotary variation in a turbine rotation speed is equal to or greater than a set value. When the rotary variation reaches or exceeds the set value, an oil pressure controlled variable at this time is measured and stored. Then, on the basis of the measurement data, a correction amount relating to the unique characteristic variation of the automatic transmission incorporated into a vehicle body is determined and written to a TCU.

Abstract: A lock-up clutch control device which controls a lock-up clutch (6) provided in a torque converter (5) interposed between an engine (3) and a transmission (4) used with a vehicle, is disclosed. The lock-up clutch control device has a differential pressure generating device (7,8), a vehicle speed sensor (13), a throttle valve opening sensor (14), an transmission input shaft rotation speed sensor (16), engine torque detection means (2), and a controller (1). The controller (1) determines, based on the detected vehicle speed (VSP) and the detected throttle valve opening (TVO), whether or not a control region of a torque converter is a converter region wherein control is performed to disengage the lock-up clutch.

Abstract: A lock-up clutch control device controls a lock-up clutch provided in a torque converter mounted between an engine and a transmission of a vehicle. The lock-up clutch control device switches between a converter state and a lock-up state by controlling a differential pressure supplied to the lock-up clutch. The lock-up clutch control device has a controller and a differential pressure generator for generating the differential pressure in response to a differential pressure command value. The controller calculates a first differential pressure command value which decreases at a predetermined rate, after the vehicle speed becomes a first predetermined speed; sets the differential pressure command value to a second differential pressure command value, before the vehicle speed becomes a second predetermined speed; and sets the differential pressure command value to a value at which the lock-up clutch is immediately released, when the vehicle speed becomes the second predetermined speed.

Abstract: When it has been determined that control for a predetermined upshift has been started while an accelerator pedal was not being depressed, and that a factor that changes an input torque of an automatic transmission has been generated, an engaging pressure of a predetermined hydraulic frictional engagement device is corrected by a correction amount in accordance with the factor that changes the input torque. As a result, undershooting of an engine speed, as well as shift shock which results from that undershooting, is able to be preferably suppressed.

Abstract: An initial command oil pressure of a lock-up control of coasting lock-up region is set by using a lock-up learning correction amount calculated by a learning control in a lockup control of the other of the plurality of lock-up regions such as slip lock-up region and complete lock-up region when one of the lock-up control of these other lock-up regions is performed before the lock-up control of the coasting lock-up region. Thus, a lock-up learning correction amount can be commonly used among three kinds of lock-up regions, and a lock-up as set is early realized in each lock-up region.

Abstract: In an automatic transmission having a torque converter interposed between an engine and a transmission mechanism, the torque converter includes a lock-up clutch capable of directly coupling an output shaft of the engine and an input shaft of the transmission mechanism. A speed difference detector is provided for detecting a difference between engine rotational speed and input shaft rotational speed. An engine speed controller means is also provided for controlling the engine speed to cause the speed difference to converge within a predetermined range. By detecting the speed difference, it is possible to precisely detect the actual vehicle state, and to reliably and smoothly engage the lock-up clutch without generating shift shock in any vehicle state. With this structure, the lock-up clutch can be reliably engaged and the engine brake can be secured.

Abstract: An apparatus for controlling a power transmission device, having a lockup shift valve that changes the operating state and non-operating state of the lockup mechanism, and a regulator valve that is capable of changing the pressure (line pressure) of working oil used to operate a speed changer CVT between a low pressure and a high pressure, wherein changeover between a mode, where the lockup mechanism is operated and the line pressure is set to a low pressure, and a mode, where the lockup mechanism is not operated and the line pressure is set to a high pressure, is carried out by changing the output of ON and OFF signals from the first solenoid valve.

Abstract: An initial command oil pressure of a lock-up control of coasting lock-up region is set by using a lock-up learning correction amount calculated by a learning control in a lockup control of the other of the plurality of lock-up regions such as slip lock-up region and complete lock-up region when one of the lock-up control of these other lock-up regions is performed before the lock-up control of the coasting lock-up region. Thus, a lock-up learning correction amount can be commonly used among three kinds of lock-up regions, and a lock-up as set is early realized in each lock-up region.

Abstract: The invention relates to a method for controlling a high-temperature operating mode of an automatic transmission wherein at least one value of an actual engine (CMO) or transmission (CGT) temperature is continuously measured. In the electronic control unit several gear shift control programs are stored and are accessed at normal operating temperatures according to an evaluation counter provided with a driving activity characteristic. It is proposed that the evaluation counter be provided with a high-temperature operating value (MAX(UDCHMMO, UDCHMGT)) with which is associated a gear shift program which also has temperature-lowering properties when the actual temperature value (CMO, CGT) is higher than a first limit value (MOMIN, GTMIN).

Abstract: An apparatus for controlling an automatic transmission of an automobile and a control method thereof. When a feedback control is executed by the automatic transmission while the speed is being changed, the control operation may often lose stability. This is due to a large deviation between a target value and a practical value at the start of the feedback control operation being caused by a change in the opening degree of the throttle and a change in the oil temperature in the automatic transmission. To solve such a technical problem, the invention employs a control apparatus which detects that the automatic transmission is changing the speed, operates the output shaft torque of the automatic transmission, recognizes a point of inflection of the output shaft torque while the speed is being changed, sets a target output shaft torque of the automatic transmission, and sets an initial target value at a moment of said point of inflection.

Abstract: A pre-compensator equipped slip control system for a lock-up torque converter employing a lock-up clutch, includes a slip-rotation control section that begins to calculate a compensated target slip rotation from a time when an actual slip rotation between input and output elements of the torque converter becomes less than a predetermined slip-rotation threshold value after shifting from a torque-converter action area to a slip-control area, so that the actual slip rotation is brought closer to the compensated target slip rotation. Also provided is a feedforward control section that determines a lock-up clutch engagement pressure by way of feedforward control during a period of time from a time when the torque converter is shifted from the torque-converter action area to the slip-control area to the time when the actual slip rotation becomes less than the predetermined slip-rotation threshold value.

Abstract: In a vehicle wherein the output of an engine is transmitted to an output shaft via a torque converter and clutches, for forward/reverse change-over, a control device is provided which can control a creep phenomenon.

Abstract: A controller of an automatic transmission having a lockup clutch and a control method of the automatic transmission, in which engine rotational speed is prevented from changing even though turbine rotational speed changes at gear shift and slip control can be carried out without making a driver feel uncomfortable are provided. When a speed change command is detected and it is determined that an inertia phase has not yet started, target engine rotational speed during a replenish period is calculated and the target engine rotational speed control is carried out to have the target engine rotational speed. When it is determined that the control is in the inertia phase, another target engine rotational speed during the inertia phase is calculated. Then, target engine rotational speed control in which the engine rotational speed at the start of the inertia phase is maintained as the target engine rotational speed is carried out.

Abstract: A control apparatus for an automatic transmission of a vehicle having a forward friction element for engaging or disengaging a turbine shaft with the automatic transmission in a forward running direction and a lock-up clutch for directly transmitting a rotation of an engine to the turbine shaft, comprises an abrupt deceleration control means for disengaging the forward engagement element and the lock-up clutch when an abrupt deceleration of the vehicle is detected, and a restoring means for canceling the abrupt deceleration control means and for restoring the forward friction element to an engagement state when an accelerator pedal is depressed for acceleration.

Abstract: A torque converter lock-up clutch controlling system for a vehicle drive train inputs a vehicle speed signal and an engine load signal. The vehicle drive train includes an automatic transmission operable in a manual ("M") ratio change mode when an operator selects a "M" range position. The system enables the automatic transmission to behave like a manual transmission upon selection of the "M" range position. A memory includes a "M" range lock-up shift point map for storing data which relates the lock-up application and release to the vehicle speed and engine load signals. The "M" range lock-up shift point map includes lock-up application values, which correspond to the magnitudes of the vehicle speed signal at which lock-up clutch applications are to occur. The magnitudes of the vehicle speed signal at which lock-up clutch applications are to occur are determined in a manner as a function of the magnitudes of the engine load signal.

Abstract: A lock-up control method of an automatic transmission for making the optimum lock-up control correspond to a shift control. In the lock-up control method of the automatic transmission in which the fastening force of a lock-up clutch is temporarily dropped to cause the lock-up clutch to slip in shifting the automatic transmission, the maximum value of a rate of change of speed of an input element is found while shifting the automatic transmission, the fastening force of the lock-up clutch is corrected so that a deviation between the maximum value and a target rate of change of speed of the input element is zeroed and the lock-up clutch is fastened by the corrected fastening force in the next shift.

Abstract: An apparatus and method control an automatic transmission of an automobile. When a feedback control is executed by the automatic transmission while the speed is being changed, the control operation may often lose stability due to a large deviation between a target value and a practical value at the start of the feedback control operation being caused by a change in the opening degree of the throttle and a change in the oil temperature in the automatic transmission. To solve such a technical problem, the control apparatus which detects that the automatic transmission is changing the speed, operates the output shaft torque of the automatic transmission, recognizes a point of inflection of the output shaft torque while the speed is being changed, sets a target output shaft torque of the automatic transmission, and sets an initial target value at a moment of the point.

Abstract: In order to improve the fuel consumption by maintaining the lock-up clutch as tightly as possible during the down-shift operation, a lock-up clutch control apparatus is provided.

Abstract: A multi-ratio automatic transmission has a plurality of fluid operated clutching devices, a fluidic torque converter and a fluid operated torque converter clutch mechanism. During certain operational periods, a hot mode is invoked to eliminate certain heat sources and increase heat dissipation to thereby prevent the fluid temperature from exceeding a predetermined maximum temperature. The hot mode is invoked as a function of both the temperature of the transmission fluid and the rate of change of the fluid temperature.

Abstract: A control system for controlling an automatic transmission equipped with a torque converter which is locked and unlocked through a lockup clutch has a lockup release control device which releases locking of the torque converter at different release rates between a downshift resulting from an increase in engine load and a downshift resulting not from an increase in engine load.

Abstract: A method and system for testing the functionality of a solenoid used to change the apply state of a torque converter clutch in a vehicle having an electronic control unit and a driveline system including an engine, a transmission, a torque converter. A first torque converter speed ratio is established. The commanded apply state of the torque converter clutch is determined, then a second torque converter speed ratio is calculated using engine speed and output shaft speed. The functionality of the torque converter clutch solenoid is established by determining whether the torque converter clutch solenoid has changed the applied state of the torque converter clutch by performing a comparison of the first and second torque converter speed ratios.

Abstract: The slip control system of a lockup clutch including a lockup relay valve and a duty solenoid (50). The lockup relay valve switches the engagement state of the lockup clutch in response to the actuation of a switching solenoid. In the state in which the lockup relay valve is switched to a position for exhausting working oil out of a release side oil chamber in a torque converter, the duty solenoid receives a duty factor correspondent to the desired value of a slip magnitude as delivered from a controller (58) and then controls the quantity of exhaust of the working oil. Thus, the slip control system can attain a reduced cost and a smaller size as well as a lighter weight while being enhanced in reliability and controllability.

Abstract: A lock-up clutch control method controls a torque converter comprising an input shaft through which a rotating force from an engine is input, an output shaft which outputs a driving force to the side of driving wheels and a lock-up clutch which operates in response to a hydraulic pressure. A control element controls an engaging pressure of the lock-up clutch by way of the hydraulic pressure. The engaging force of the clutch is controlled in accordance with calculated results of a target following up section for calculating a controlled variable so that a slip follows up a target slip and a control system stabilizing section for calculating the controlled variable so that the disturbance applied to the control system is compensated. Thereby, a stable control may be realized without receiving any effect of the disturbance. The disturbance may be estimated and learned for more accurate control.

Abstract: An apparatus including a slip control device for controlling an amount of slip of a lock-up clutch disposed between pump and turbine impellers in a power transmission system of a motor vehicle, a slip-parameter monitoring device for detecting the actual slip speed of the lock-up clutch or a control error between actual and target slip speeds of the lock-up clutch, a summing device for obtaining a sum of values of the actual slip speed or control error detected by the slip-parameter monitoring device for a predetermined period of time, and a defect detecting device for determining the presence or absence of a defect in slip control of the lock-up clutch by the slip control device, on the basis of the sum as compared with a predetermined reference.

Abstract: A method of determining the deterioration of automatic transmission fluid by detecting shudder during the EMCC portion of air conditioner clutch engagement. Shudder is detected by calculating the acceleration of the turbine during EMCC slip with the following equation:.SIGMA..alpha..sub.t =.SIGMA..alpha..sub.t (i-1)+.alpha..sub.twhere .alpha..sub.t represents the absolute value of turbine acceleration. In a preferred embodiment, the turbine acceleration is summed for twenty-eight periods of 7 msec each after the start of EMCC and the determination that shudder occurred made if the resulting value exceeds a predetermined number. In a further preferred embodiment, the method is used to modify the air conditioner compressor clutch engagement sequence. Once it is determined that shudder is occurring during the EMCC portion of the air conditioner compressor clutch engagement sequence, the EMCC portion of the air conditioner clutch engagement sequence is eliminated or bypassed.

Abstract: In response to a signal indicating the present throttle valve opening degree detected by a throttle valve sensor and a signal indicating the present vehicle speed detected by a vehicle speed sensor, a lock-up controller determines whether a lock-up clutch should be brought into the operatively connected state or it should be released from the operatively connected state, and on completion of the foregoing determination, the controller outputs a certain signal to a solenoid valve. In the case that the lock-up clutch has been released, this state is maintained. On the contrary, in the case that the lock-up clutch has been in the operatively connected state, the controller determines whether maintains this state or selects a lock-up clutch releasing pattern depending on the present throttle valve opening degree.

Abstract: An apparatus for controlling a lock-up clutch between pump and turbine impellers in a power transmitting system of a motor vehicle, including a slip control device for controlling the amount of slip of the lock-up clutch, and a judder detector for detecting a judder of the lock-up clutch based on the number of detected speed variations of the turbine impeller during slip control of the lock-up clutch by the slip control device, wherein the judder detector is inhibited from using a variation of the turbine impeller speed variation for the detection of the judder, if the amount of change of the variation amplitude is larger than a predetermined threshold or if the period of the variation is outside a predetermined range.

Abstract: Electronic and hydraulic control system of an automatic transmission for automotive vehicle and method for controlling hydraulic pressure whereby line hydraulic pressure can be compensated. A hydraulic pressure state within the electronic and hydraulic control system is precisely detected and the signal of this detected hydraulic pressure is transmitted to a transmission control unit such that the malfunction of the valves and the correct gear shifting stage can be determined. Since the hydraulic pressure state can be detected to be compensated by the control of the TCU, such that the shift quality can be improved.

Abstract: An apparatus for controlling the amount of slip of a lock-up clutch between pump and turbine impeller of a torque converter or other fluid-filled power transmitting device in a motor vehicle, the lock-up clutch including a piston which is operated by a pressure difference between pressures in two oil chambers on the opposite sides of the piston, and the apparatus including a slip control device for controlling the lock-up clutch according to a slip control output such that the actual slip of the lock-up clutch coincides with a target slip speed, and an output oscillating device for oscillating the slip control output to oscillate the pressure difference without vibrating the piston.

Abstract: A lock-up clutch by way of which input/output shafts of a torque converter are operatively connected to each other is connected to an electronic type pressure control valve. During speed changing in a transmission, the problem of interruption of torque transmission can be solved by turning off the lock-up clutch at the time when filling of one of the speed changing clutches to be next brought into an operatively engaged state with hydraulic oil is completed. Hydraulic pressure (P.sub.t) in the torque converter is exerted on the back 100 pressure portion of a piston of the lock-up clutch while hydraulic pressure (P.sub.t) in the torque converter is exerted on the proportional solenoid side of the pressure control valve, making it possible to reduce the initial hydraulic pressure. During speed changing, the lock-up clutch is not fully released from the engaged state but maintains its operative state at low pressure, causing shock from shifting the lock-up state to be reduced.

Abstract: A torque converter clutch control provides for a controlled capacity mode of operation wherein clutch slip is controlled to a reference value. A lock mode is also provided wherein clutch slip is eliminated. The transition from the controlled capacity mode to the lock mode is caused to occur when clutch slip is stabilized by increasing clutch engagement force by an amount sufficient to smoothly reduce slip speed to zero and thereafter maintain zero slip. The increase in engagement force is marginally sufficient to maintain slip at zero thereby allowing engine torque excursions to be absorbed by allowing slip during such excursions. Transitions back to the controlled capacity mode are adapted to current torque and slip conditions.

Abstract: An automatic transmission system provided with a power take-off unit, which is composed of a torque converter equipped with a lock-up clutch and a control unit that serves to set the lock-up clutch ON/OFF. With the power take-off unit in operation, the control unit sets the lock-up clutch ON only when an engine output is determined to be higher than a predetermined level, and a shift lever is set in either neutral or parking position.