Abstract: A vehicle having an engine that drives a transmission includes a pump that provides fluid to the transmission and a temperature sensor that monitors a temperature of the fluid. The temperature sensor generates a temperature signal. A control module receives the temperature signal and operates the pump to provide the fluid at a first pressure when the temperature signal is below an upper temperature limit. The control module operates the pump to provide the fluid at a second pressure when the temperature signal is above the upper temperature limit.

Abstract: A hydraulic control system for an automatic transmission includes a lubrication passage for feeding lubricating oil to a wet clutch and lubrication points of the transmission, first and second passages with a large-diameter orifice and a small-diameter orifice, respectively, arranged upstream of the lubrication passage, a switching valve for switching fluid communication between the lubrication passage and the first and second passages, a solenoid for controlling the switching valve, and an ECU for controlling the solenoid.

Abstract: A control system and control method for a swap-shift transmission having auxiliary and main gearsets wherein precise synchronization control of ratio changes of each gearset at the start and at the end of a swap-upshift progression is achieved using an adaptive control to adjust friction element pressure values and slip times for friction elements of each gearset, whereby shift synchronization is achieved throughout the operating life of the transmission.

Abstract: An automatic transmission including plural friction engaging elements configures plural shift ranges based on combinations of each friction engaging element being in engaging or disengaging condition and a controlling unit for controlling the friction engaging elements to be in engaging or disengaging condition by controlling a hydraulic pressure applied.

Abstract: Under the learning mode during a vehicle stationary condition, an oil pressure of the friction engagement element for setting a standby oil pressure value is increased by a predetermined step pressure while a transmission input shaft rotational speed has been maintained, and a standby oil pressure is set for shifting the friction engagement element to an engagement side. A controlled value is verified whether it is within a predetermined range corresponding to the predetermined step pressure when a change of the input value due to decrease of the turbine rotational speed satisfies a predetermined condition. The controlled value is learned when the controlled value is within the predetermined range corresponding to the step pressure. A step pressure larger than the step pressure is set when the controlled value is beyond the predetermined range corresponding to the step pressure.

Abstract: A method for a shift control of a power shift transmission includes closing an incoming, engaging clutch unit assigned to a new gear and opening the outgoing, disengaging clutch unit assigned to an old gear such that the closing and the opening overlap in time. The incoming clutch unit is closed after performing a filling operation for providing a filling pressure for the incoming clutch unit. The filling operation is concluded by a filling end. In case of a manually triggered power shift, the filling operation for the incoming clutch unit is performed with an increased filling pressure corresponding to an order of magnitude of the clutch capacity of the outgoing clutch unit. After the filling end is identified, the outgoing clutch unit is opened and, overlapping in time, a clutch capacity of the incoming clutch unit is adapted.

Abstract: A hydraulic clutch transmits driving torque in a power train of a vehicle. An oil pressure supply unit supplies oil pressure for engagement to the clutch and a controller controls the unit. The controller causes the unit, prior to engagement of the clutch, to precharge the interior of the clutch with hydraulic fluid. The controller counts an elapsed time since the last release of the clutch and shortens the precharge period as the elapsed time decreases, thereby optimizing the precharge state of the clutch.

Abstract: In control apparatus and method for an automatic transmission, an initial hydraulic reference value is calculated which provides a reference value of an initial hydraulic from a shift kind and a throttle opening angle or from the parameter value corresponding to the throttle opening angle and a correction quantity is calculated for the reference value of the initial hydraulic on the basis of squares of a revolution speed of a piston calculated and of the revolution speed of the piston detected, the initial hydraulic reference value being set to the initial hydraulic during the ordinary gear shift and the initial hydraulic reference value being corrected by a correction quantity to set the corrected initial hydraulic reference value to the initial hydraulic when the gear shift to a predetermined target gear shift stage is carried out at a drive point different from during the ordinary gear shift.

Abstract: According to an aspect of the present invention, an automatic transmission includes plural friction engaging elements configures plural shift ranges based on combinations of each friction engaging element being in engaging or disengaging condition, a controlling unit for controlling the friction engaging elements to be in engaging or disengaging condition by controlling a hydraulic pressure applied.

Abstract: A clutch is operated by an actuating pressure pressure during an engaging process of the clutch. The actuating pressure is controlled over time such that predetermined characteristics for an engagement of said clutch are approximated by starting a process for changing a rotational speed of an output shaft of the torque converter for an adaptation of the rotational speed to an actual velocity of the vehicle during engagement of the clutch. An ideal signal for the rotational speed is determined which corresponds to an estimate for an engagement of the clutch with the predetermined characteristics. An actual signal of the rotational speed of the output shaft over time is measured during said process. Deviations are determined between the actual signal and the ideal signal. Finally the signal of the actuating pressure over time is automatically changed in order to reduce the deviations between the actual signal and the ideal signal if the deviations exceed a threshold.

Abstract: A shift pressure control apparatus for an automatic transmission is arranged to hold the shift pressure during a shift at a starting input-torque-dependent pressure determined from a transmission input torque at a start of a shift. A controller is configured to monitor an operating parameter representing an engine load of an engine, to detect an engine load change. When the engine load change is detected, the controller modifies the shift pressure to a modified pressure determined by modifying the starting input-torque-dependent pressure with a difference between a second engine-load-dependent pressure determined from the engine load after the engine load change and a first engine-load-dependent pressure determined from the engine load at the start of the shift.

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 automatic transmission system for a vehicle includes a rotational speed detector for detecting a variation of a rotation number of driving torque transmitting member when a friction engagement element, which has been disengaged based upon oil pressure controlled by a control unit, a side of which has been transmitted with the rotation of the driving torque transmitting member, and the other side of which is locked not to be rotated during the vehicle at a stationary condition, is controlled to be engaged, wherein an oil pressure characteristic value of the friction engagement element is learned by the control unit based upon the variation of the rotation number of the driving torque transmitting member when the friction engagement element is initially engaged.

Abstract: An ECT-ECU includes an abrupt turbine speed increase learning control circuit which prevents simultaneous release of both a frictional engagement element to be released and a frictional engagement element to be engaged, a tie-up learning control circuit which prevents simultaneous engagement of both the frictional engagement element to be released and the frictional engagement element to be engaged, a determination circuit that determines whether one of tie-up learning control and abrupt turbine speed increase learning control is necessary based on the turbine speed, and a control circuit that prohibits execution of the tie-up learning control unless the number of trips after the abrupt turbine speed increase learning control has been executed is at least equal to a predetermined number, when it has been determined that the tie-up learning control is necessary.

Abstract: A control device for a vehicle controls a motor-driven pump at an appropriate timing when an internal combustion engine is stopped or starts. An ECU of the control device comprises an operation determination section which determines whether or not the motor-driven pump is operated depending on the value of an idling stop flag that makes the internal combustion engine stop, depending on a measured value output from an oil pressure sensor for measuring oil pressure in oil lines providing operation oil to a torque converter and a transmission, and depending on a measured value output from an oil temperature sensor for measuring the temperature of the operation oil; and a target electrical current calculation section for calculating a target value of electrical current to be supplied during the operation of the motor-driven oil pump depending on the determination result by the operation determination section.

Abstract: According to an aspect of the present invention, an automatic transmission includes plural friction engaging elements configures plural shift ranges based on combinations of each friction engaging element being in engaging or disengaging condition, a controlling unit for controlling the friction engaging elements to be in engaging or disengaging condition by controlling a hydraulic pressure applied.

Abstract: A shift control system of a toroidal CVT for a vehicle is arranged to calculate a command gear ratio by adding a desired gear ratio and a torque shift compensation quantity for compensating a difference between the desired gear ratio and an actual gear ratio which difference is generated by a shifting operation of the toroidal CVT, and to set a magnitude of the torque shift compensation quantity employed in an automatic shift range to be larger than a magnitude of the torque shift compensation quantity employed in other shift range except for the automatic shift range when the actual gear ratio is in a first gear ratio region except for a second gear ratio region including a largest gear ratio.

Abstract: When shifting the gear position into a target gear position from a current gear position, some gear position different from said current gear position is used as one distributing gear position. The control unit controls the pressing load of a synchromesh of one distributing gear position to make at least part of the rotation torque from the drive power source transfer by the friction. Thereby it makes at least part of the rotation torque transferred by a synchromesh of the current gear position decrease. And then it moves the synchromesh of said current gear position to a disengaging position not meshed with said idle gear. Thereafter another gear position different from said target gear position and said one distributing gear position is used as another distributing gear position.

Abstract: A method and apparatus for operating an automatic transmission as a function of the engine rotational speed of a variable speed internal combustion engine. Upon a failure of the electronic control system, a return home of a motor vehicle under its own power is enabled. A delivery system delivers a working medium with which a transmission ratio adjusting device is actuated by a first control device that, in turn, is controlled by a pilot pressure that can be accurately changed by a second control device to actuate the transmission ratio adjusting device. The pilot pressure for controlling the first control device is changed by a third control device as a function of the rotational speed of the internal combustion engine when an adjusting device is switched out of a normal operation position into an emergency operation position.

Abstract: A control unit for a hybrid vehicle includes a take-off detection unit that detects a start of movement of the hybrid vehicle from a stopped state; and a torque control unit that limits a engine torque input to an automatic transmission from becoming excessive by generating negative torque using a regeneration operation of a motor on occasions when the start of running of the hybrid vehicle is detected by the take-off detection unit. Accordingly, it is possible to reliably inhibit problems, such as an occupant of the hybrid vehicle being caused to feel an unpleasant jolt due to torque transmitted to a driven wheel side increasing instantaneously as a result of change in an application state of a clutch during the start of movement.

Abstract: The clutch oil pressure (PC1) supplied to a hydraulic controller of an automatic transmission is detected. If it is detected that the clutch oil pressure (PC1) is less than or equal to a first threshold value PA when a first oil pump cooperative with a drive power source is to stop, the second oil pump is driven. Therefore, after the oil pressure (for example, PY) remaining from the first oil pump has decreased, the second oil pump is driven, and an oil pressure (PX) needed for the hydraulic control of friction engagement elements is maintained. If it is detected that the clutch oil pressure (PC1) is greater than or equal to a second threshold value (PB) when the first oil pump is to be driven, the second oil pump is stopped. Therefore, the second oil pump is stopped when the oil pressure provided by the first oil pump rises to such a level that the oil pressure (PX) can be secured. Thus, the load on the second oil pump is reduced so as to allow it to be reduced in size.

Abstract: A pressure regulating valve which is comprised of a valve body being comprised of a cylinder, a spool slidably disposed in the cylinder with a clearance, the spool and the cylinder defining a pressure chamber and a space portion, and an urging member which urges the spool in a direction opposite to a direction of a force applied to the spool by fluid pressure in the pressure chamber. A supply passage fluidly communicates the cylinder and a fluid pressure supply source, and a drain passage fluidly communicates the cylinder and a sump. A through-passage formed in the spool fluidly communicates the pressure chamber and the space portion. An orifice disposed between the space portion and a sump limits a flow rate of fluid drained from the space portion to the sump. The spool is made of material having a lower thermal expansion coefficient than material of the valve body.

Abstract: A transmission control system, includes:

Abstract: In an automatic transmission provided with a plurality of torque transmission means between the input shaft and output shaft of a gear-type shifting means, in which said torque transmission means for at least one shifting stage is a multi-disc clutch and the torque transmission means for all other shifting stages are claw clutches and said multi-disc clutch is controlled to accomplish smooth shifting from one shifting stage to another shifting stage, the torque capacity of the multi-disc clutch is increased above the maximum output shaft torque of the transmission and the torque of the multi-disc clutch is generated so that the output shaft torque does not change significantly during shifting.

Abstract: In a gearbox control system (8) for detecting systematic errors and long-term changes, the behavior of a real gearbox (1) is compared to the behavior of an ideal gearbox (7), which is implemented in the form of a gearbox model in the gearbox control system (8).

Abstract: A process for regulating stopping of an engine during a typical traffic idling event in order to reduce fuel consumption. There is an interactive process between the engine and the transmission involving shutting down the engine when the driver has braked to a stop and restarting upon release of brake pressure. The transmission input elements are clamped during the engine shut down to minimize transient torque disturbance and the vehicle is restarted when motion is detected. The process involves pressurizing of first gear friction elements during the stop period using an auxiliary pump so that the transmission will be ready to transmit torque on restart. Restart surge is avoided by transmitting a limited amount of torque in a controlled manner during a restart.

Abstract: When a different speed change request occurs during pre-charging, an indicated pressure is stepwise changed up to a standby pressure for after pre-charge, and a processing in accordance with the different speed change request is commenced with the indicated pressure after the stepwise change, as an initial pressure.

Abstract: A control device for an automatic transmission has a torque transmission provided between an input shaft and an output shaft of a gear-type transmission The torque transmission in at least one change gear stage is a friction clutch. When performing a change gear from one change gear stage to another change gear stage, the friction clutch is controlled. A transfer torque capacity detector detects or computes transfer torque of the friction clutch when performing a change gear to a predetermined change gear stage, and a clutch release timing determining apparatus determines a timing when releasing the claw-type clutch into a neutral state based on the value detected or computed by the torque capacity detector.

Abstract: A power transmission comprises an engine E with a plurality of cylinders, a belt-type continuously variable transmission CVT, which changes the rotational speed being transmitted from the engine, a control valve CV, which variably sets the line pressure used for controlling the speed change ratio of the transmission, and an electrical control unit ECU, which calculates the torque of the output shaft of the engine when the engine is decelerating in a partial cylinder operation mode. While a vehicle equipped with this power transmission is decelerating with the engine being in a partial cylinder operation mode, the control valve CV sets the line pressure in correspondence to the torque of the engine output shaft calculated by the electrical control unit ECU.

Abstract: A method of driving a vehicle having an automatic transmission with an electronic control device input with a clutch pressure through the loading standing device of a clutch where the clutch pressure is isolated according to the gearbox input factor and a gear as a characteristic curve in an electronic driving device and the clutch pressure of a clutch along the power flow path is defined during the motion outside the gear change according to the real transmission capability of the clutch.

Abstract: An automatic transmission has a gear transmission mechanism with engaging devices. Up-shifting is achieved with oil pressure, which is controlled with an open control component, a gradient of which is determined based on input torque, and a feedback control component, which is based on a target gear ratio. To prevent shock during an up-shift caused by releasing the accelerator, the feedback control component is set to zero when the amount of change in the throttle opening is equal to or greater than a predetermined threshold value. As a result of inhibiting increase in feedback to make up for a tendency for oil pressure depending on an open control component to decrease as a result of the throttle opening reducing and input torque falling, increase of the oil pressure command value becomes smooth. Peaks of the output torque are therefore suppressed.

Abstract: A method for control of a transmission of a vehicle, especially of an automatic transmission or an automated manual mechanical transmission with hydraulically actuatable shifting elements is described. A speed signal (n_ab_ist, n_t_ist) of the output train with precalculatable time curve (n_ab_soll, n_t_soll) is determined and for adjustment of a nominal filling of the shifting elements an interference signal (P1, P2, P3, P4, PF1, PF2, PF3, PF4) is applied. In case of a untolerable divergence of the speed signal (n_ab_ist, n_t_ist) of the output train from its precalculated curve, a divergence from the nominal filling of the shifting element is detected, the information being processed for control of the shifting elements.

Abstract: A shift control apparatus is arranged to effect a shift in an automatic transmission by changeover of friction elements to be engaged with disengagement of a disengagement-side friction element and engagement of an engagement-side friction element. A shift controller is configured to detect an end of a loss stroke in the engagement-side friction element, and performs an operation to decrease the disengagement-side working oil pressure at a set gradient and to increase the engagement-side working oil pressure at a predetermined gradient upon detection of the end of the loss stroke in the engagement-side friction element. The predetermined gradient of the engagement-side working oil pressure for the engagement-side friction element is made lower for a low engine load than for a high engine load.

Abstract: A hydraulic control unit including a hydraulic servo for engaging and disengaging each friction engagement element, hydraulic pressure supply device for supplying hydraulic pressure to a hydraulic servo of a predetermined friction engagement element selected according to a gearshift position to be achieved, failure detection device for detecting a failure has occurred in the hydraulic pressure supply device, and fail-safe device for preventing interlock that occurs due to a plurality of friction engagement elements being engaged, and also prevents a gearshift from a high-speed position to a low-speed position, when the failure detection device detects that a failure has occurred.

Abstract: An ECT-ECU includes an abrupt turbine speed increase learning control circuit to avoid a situation in which both a frictional engagement element to be released and a frictional engagement element to be engaged are in a state of release at the same time, a tie-up learning control circuit to avoid a situation in which both the frictional engagement element to be released and the frictional engagement element to be engaged are in a state of engagement at the same time, a determination circuit that determines whether one of tie-up learning control and abrupt turbine speed increase learning control is necessary based on a signal input from a turbine speed sensor, and a control circuit that prohibits execution of the tie-up learning control unless the number of trips after the abrupt turbine speed increase learning control has been executed is equal to, or greater than, a predetermined number, when it has been determined that the tie-up learning control is necessary.

Abstract: A control system for controlling operation of a pre-charge system of an automatic transmission. The control system comprises a first section which receives first and second gear change instructions which are issued in succession. The first and second gear change instructions are of a type of needing an engaged condition of a same friction element. The control system further comprises a second section which, when the second gear change instruction is issued during a pre-charge period of the friction element which is needed by the first gear change instruction, extends the pre-charge period of the friction element to a time when a pre-charge period needed by the second gear change instruction lapses.

Abstract: An engagement pressure control apparatus for a torque-transmitting mechanism in a transmission control apparatus includes a regulator valve and a boost valve. The regulator valve provides a controlled pressure rise to a torque-transmitting mechanism within the transmission during a shifting event, and the boost valve is effective to increase the fluid pressure from the regulator valve to the torque-transmitting mechanism when the shift event has been completed, thereby providing a high pressure at the torque-transmitting mechanism to prevent slipping.

Abstract: In a process wherein a before-shifting gear ratio Gx changes to a gear ratio of the target gear position, an actual shift time is measured by regarding as a shift starting point an earlier one between a time point when the present gear ratio G has repeated decreasing by a value equal to or larger than a predetermined unit gear ratio &Dgr;G a predetermined number of times N and a time point when the present gear ratio reaches a first gear ratio G1 that is set to a value smaller than the gear ratio Gx by a predetermined value. If the gear ratio changes rapidly, the start of shifting can be detected at a time ts1 when the present gear ratio G reaches the gear ratio G1, and if the gear ratio changes slowly, the start of shifting can be detected at a time ts4 when the gear ratio has repeated decreasing by a value equal to or larger than a predetermined unit gear ratio a predetermined number of times N. In either case, the start of shifting can be detected early at a point in proximity to a shift starting point ts.

Abstract: In a process wherein a before-shifting gear ratio Gx changes to a gear ratio of the target gear position, an actual shift time is measured by regarding as a shift starting point an earlier one between a time point when the present gear ratio G has repeated decreasing by a value equal to or larger than a predetermined unit gear ratio &Dgr;G a predetermined number of times N and a time point when the present gear ratio reaches a first gear ratio G1 that is set to a value smaller than the gear ratio Gx by a predetermined value. If the gear ratio changes rapidly, the start of shifting can be detected at a time tsl when the present gear ratio G reaches the gear ratio G1, and if the gear ratio changes slowly, the start of shifting can be detected at a time ts4 when the gear ratio has repeated decreasing by a value equal to or larger than a predetermined unit gear ratio a predetermined number of times N.

Abstract: A method for controlling a transmission of a motor vehicle, especially of an automatic transmission or of an automated manual mechanical transmission. The transmission has hydraulically actuatable shifting elements which, during gear shifts, are engaged or disengaged via pressure curves (p_kzu, p_kab) stored in an electronic control unit. For one gear shift are carried out at least one adaptation of the pressure curves (p_kzu, p_kab) of the shifting elements for compensation of tolerances of components and alternative to this one adaptation for compensation of influences determinant of shifting quality for different shifting strategies and/or shifting kinds, the filling parameters of the engaging shifting elements being determined during the gear shift itself or by preset test pressure curves outside the gear shift.

Abstract: Apparatus for controlling a vehicle drive system including an automatic transmission, including a feedback controller operable upon a shift-down action of the transmission effected by concurrent releasing and engaging actions of first and second frictional coupling devices during an operation of a manually operable vehicle accelerating member to drive the vehicle with the drive power soruce, for controlling an engaging force of the first frictional coupling device, and a learning compensator operable upon detection of an abnormality of the shift-down action, for learning compensation of an initial value of the engaging force at which a feedback control of the engaging force is initiated, or an output reducing device for reducing an output of a drive power source when input speed of the transmission has been increased to a value close to a synchronization value, and/or upon racing of the drive power source during the shift-down action.

Abstract: A hydraulic control system including: a rotating speed raising unit for raising the rotating speed of the prime mover while the transmission is not rotated by the prime mover, to increase an output volume of the hydraulic pump; at oil pressure instructor for outputting a plurality of instruction signals of different pressure instruction values to the valve modulating mechanism while the output volume of the hydraulic pump is increased; an oil pressure detector for detecting the oil pressure to be modulated and fed to the transmission, at a plurality of pressure levels; and a learning corrector for learning and correcting the instruction signals on the basis of the outputted pressure instruction value and the detected oil pressure detected.

Abstract: A hydraulic system for an automatic transmission for a vehicle with an engine having idle-stop control includes a bypass passage which allows communication between a first hydraulic passage downstream of a manual valve and a forward engagement element, a first switching valve arranged on the bypass passage to be switched between a communicating state and a non-communicating state, and a first switching device which switches the first switching valve between the communicating state and the non-communicating state. The first switching device switches the first switching valve to the communicating state when the hydraulic pressure is lower than a predetermined pressure.

Abstract: The transmission is equipped with engaging devices in a gear transmission mechanism, and when up-shifting from a first gear position to a higher second gear position, oil pressure command value for an engaging device used in the up-shift is made up of an open control component, the gradient of which is determined based on input torque, and a feedback control component based on a target gear ratio. In order to prevent a shock during up-shift caused by releasing a foot from the accelerator pedal, the feedback control component is set to zero when the amount of change in the throttle opening is equal to or greater than a predetermined threshold value. As a result of inhibiting increase in feedback in order to make up for a tendency for oil pressure depending on an open control component to decrease as a result of the throttle opening reducing and input torque falling, increase of the oil pressure command value becomes smooth. Peaks of the output torque are therefore suppressed.

Abstract: A line pressure control system for an automatic transmission wherein a shift range is determined by selectively engaging friction elements by means of a line pressure controlled according to an input torque of said automatic transmission. In the present invention, an engine output torque at the front stage of the automatic transmission is estimated from the operating condition. The input torque of the automatic transmission is calculated from the estimated engine output torque and the operation state of a torque converter. The calculated input torque of the automatic transmission is decreased during a predetermined time corresponding to an estimation response delay of the engine output torque after the engine is made in a no-load state, so as to properly control the line pressure.

Abstract: As the disengage pressure command value PO lowers and as the engagement pressure command value PC rises, a changeover shift is effected by bringing a disengagement side friction element into disengagement and a disengagement side friction element into engagement. The rising gradient of the engagement pressure command value PC at and after the ON instant t2 of the oil pressure switch, when the engagement side friction element takes the engaging capacity, is made as low as &ggr;1 for a low throttle opening degree but as high as &ggr;2 for a high throttle opening degree, and the lowering gradient of the disengagement side pressure command value PO is also made as small as &bgr;1 at the low throttle opening degree and as large as &bgr;2 at the high throttle opening degree.

Abstract: The patent offers a method of driving a vehicle having an automatic transmission. According to the method, an electronic control device is put in with a clutch pressure through the loading standing device of a clutch. The clutch pressure is isolated according to the gearbox input factor and a gear as a characteristic curve in an electronic driving device. The clutch pressure of a clutch along the power flow is defined during the motion outside the gear change according to the real transmission capability of the clutch.

Abstract: When the selector lever is operated from P or N range to D range, an input clutch to be engaged at the fifth gear position is temporally engaged to reduce shift shock at the time of engagement of the engaging element for the first gear position. An oil pressure command value for actuating the input clutch is increased with a constant inclination from a start point oil pressure value, and the start point oil pressure value is lowered when an engine speed is low or when an oil temperature is high. Thereby, even if a timing of completion of filling of working fluid to the input clutch is fluctuated, a difference between an actual oil pressure and the oil pressure command value is suppressed to a small level and the occurrence of shock due to surge at the time of the filling completion is prevented. Moreover, since an inclination of increase of the oil pressure command value is constant, the difference between an actual oil pressure and the oil pressure command value is prevented from widening.

Abstract: A vehicle transmission, for example a CVT transmission, is provided with a decoupling device between an engine output shaft and a vehicle driveline. The decoupling device in one embodiment includes a clutch assembly which is fixed to a shaft coupled to the transmission output and engageable with a driveline through a piston arrangement. The piston can be urged against the force of a spring by fluid pressure to cause engagement of the clutches of the clutch assembly and thereby to couple engine torque to the vehicle driveline. When fluid pressure is released, the spring urges the piston to a position in which the clutches of the clutch assembly are disengaged, so as to disengage the engine output from the vehicle driveline. In the disengaged state, the vehicle can be towed.

Abstract: A method of controlling a hydraulic actuation system for an automated transmission system including, a hydraulic clutch actuator for controlling engagement of a clutch, a gear engagement actuator for controlling engagement of a gear, said gear engagement actuator being in the form of a double acting ram having first and second working chambers acting on opposite sides of a piston, a main control valve, the main control valve selectively connecting the clutch actuator and/or the gear engagement actuator to an accumulator or to a reservoir; a gear engagement control valve selectively connecting the first and second working chambers of the gear engagement actuator to the main control valve or to the reservoir; an electrically driven pump being provided to charge the spring accumulator, the pressure of fluid in the system being controlled by switching of the pump and connection of the clutch actuator to the accumulator.