Abstract: A vehicle control device includes: a travel section determination unit configured to determine a forward travel section that is a travel section having a different road gradient from a current travel section in which a vehicle is currently traveling and that is ahead in a travel direction of the vehicle; a forward gear stage selection unit configured to select a forward gear stage which is a gear stage of the vehicle in the forward travel section; and a shift control unit configured to, in a case where the selected forward gear stage is lower by two or more stages than the current gear stage which is a gear stage of the vehicle in the current travel section and when the vehicle is positioned within a predetermined range from a start position of the forward travel section, perform downshift from the current gear stage to the forward gear stage.

Abstract: A hydraulic system of a transmission having a controller and a variable displacement pump. The pump includes an inlet and outlet and is adapted to be driven by a torque-generating mechanism. The system also includes a lube circuit fluidly coupled to the pump. A lube regulator valve is disposed in the lube circuit, such that the lube regulator valve is configured to move between at least a regulated position and an unregulated position. The regulated position corresponds to a regulated pressure in the lube circuit. A pressure switch is fluidly coupled to the lube regulator valve and configured to move between a first position and a second position, where the switch is disposed in electrical communication with the controller. A solenoid is disposed in electrical communication with the controller and is controllably coupled to the pump to alter the displacement of the pump.

Abstract: A control apparatus for a vehicle includes an electronic control unit that is configured to set a value of a target generated voltage of the generator. The electronic control unit is configured to execute power generation control to control a generated voltage of a generator. The electronic control unit is configured to maintain a value of the generated voltage in the power generation control to be constant during an upshift gear change when the upshift gear change control of a transmission is executed while the lock-up clutch control is executed during deceleration of the vehicle. The electronic control unit is configured to increase the value in the power generation control during the downshift control to the value of the target generated voltage at a first specified rate when a downshift gear change of the transmission is executed while the lock-up clutch control is executed during the deceleration.

Abstract: A method for operating a motor vehicle including an all-wheel drive that can be enabled and disabled, and a drive train including two clutches actuated by a control unit for enabling and disabling the all-wheel drive, and components rotating between the two clutches, which components are driven when the all-wheel drive is enabled and are uncoupled from the remaining drive train when the all-wheel drive is disabled. In order to allow early detection of defects and, in particular, bearing defects of the rotating components, and to determine the applied drag torque even without knowing the oil temperature, in one embodiment, when the all-wheel drive is disabled, the rotational speed (n) of at least one of the uncoupled components is measured in a time interval, and an angular acceleration of the uncoupled components is determined therefrom.

Abstract: A multi-speed automatic vehicle transmission has an electronic control unit which permits multiple downshifts if certain conditions are satisfied. Such downshifts are direct and omit engagement and disengagement of one or more intermediate speed ratios. Multiple downshifting may allow the actual speed ratio to better match the ideal speed ratio, for example under heavy braking.

Abstract: A method of operating a transmission which is shifted to various operating conditions by engaging shifting elements. At least one of the shifting elements is an interlocking shifting element which has to be engaged to obtain at least one defined operating condition of the transmission during which force flows between an input and an output shaft. When a command is received to engage the interlocking shifting element, a rotational speed of the transmission input shaft is displaced in the direction toward a synchronous rotational speed produced in the engaged operating condition of the interlocking shifting element at least as a function of the rotational speed of the transmission output shaft. When the variation of the rotational speed of the transmission input shaft crosses a predefined rotational speed threshold, the interlocking shifting element is actuated in its engaging direction.

Abstract: A method is provided for controlling an actuator of a vehicle transmission, the actuator being connected to an engaging sleeve, the engaging sleeve being axially displaceable between a gear wheel disengaging position and a gear wheel engaging position of the vehicle transmission for executing a transmission gear shift.

Abstract: An electric vehicle system featuring a novel idling capability is presented. The vehicle performs without electricity from an external power source resulting in decreased entropy generation. It also asserts a zero carbon footprint while excluding typical emissions produced by conventional all-electric vehicles. This novel invention has a capacity between idle speed (1000 rpm) and high speed (6000 rpm) using a constant electric current.

Abstract: Disclosed herein is a method for controlling gear shifting of an automatic transmission from an N gear stage to an N? gear stage. The gear shifting is embodied by means of engaging and releasing friction elements. The method includes selecting at least two among an rpm of a turbine, an rpm of a first motor generator (MG1), an rpm of a second motor generator (MG2) and an rpm of a planetary gear set as control factors, and controlling engagement and release of the friction elements using the control factors.

Abstract: The present invention relates to a method for determination of one or more shift points for a gearbox in a motor vehicle which comprises an engine connected to, in order to drive, said gearbox, where a shift point represents an engine speed at which said gearbox is adapted to effecting a downshift or upshift, said one or more shift points are determined on the basis of an engine target speed ?T and a first engine speed difference ??TT, said target speed ?T is a desired speed for said engine, said first engine speed difference ??TT is a difference between a first engine speed at a first time t1 and said target speed ?T at a second time t2, and said first and second times t1 and t2 are separated by a time period T. The invention relates also to a system, a motor vehicle, a computer program and a computer program product thereof.

Abstract: In a downshift of an automatic transmission in a state where an accelerator pedal is depressed, one of a clutch-to-clutch shift in which the shift is carried out by gradually reducing an engagement pressure of a clutch or a brake to be disengaged in the shift and a rotation synchronization shift in which the shift is carried out by reducing the engagement pressure of the clutch or the brake more quickly than in the clutch-to-clutch shift is selected based on an output shaft torque of the automatic transmission, a region where the rotation synchronization shift is selected is lower in output shaft torque than a region where the clutch-to-clutch shift is selected, and hence it is possible to appropriately selectively execute a shift placing emphasis on a shock and a shift placing emphasis on a shift speed in accordance with the output shaft torque.

Abstract: A hybrid powertrain includes an engine, an electric machine, and a transmission. A method to control the powertrain includes monitoring operation of the powertrain, determining whether conditions necessary for growl to occur excluding motor torque and engine torque are present, and if the conditions are present controlling the powertrain based upon avoiding a powertrain operating region wherein the growl is enabled.

Abstract: An automatic transmission device for a wheel loader includes: a shift mechanism; a work detection device that detects that the wheel loader is performing an excavation work; and a shift control device that executes control so as to downshift a speed stage at the shift mechanism if the work detection device detects that the wheel loader is performing the excavation work.

Abstract: A method for operating a multi-step automatic transmission arranged in a drive train of a vehicle with a combustion engine. When downshifting from the third gear ratio to a second gear ratio, higher inertia must be shifted than when shifting from the third gear ratio to the first gear ratio. Upon a demand for a coasting downshift from the third gear ratio to the second gear ratio or to the first gear ratio with no performance demand on the combustion engine, the coasting downshift to the second gear ratio is not executed and the first gear ratio is engaged when the requirements for downshifting to the first gear ratio are met.

Abstract: When it is determined to perform nth to (n+1)th coast downshift during nth to (n+1)th power-off upshift, an ECU starts increasing control to increase the hydraulic pressure of an engage-side element A in a predetermined mode and maintains the hydraulic pressure of a release-side element B at a value at which the increasing control is started until a predetermined period of time elapses from when the start of the increasing control. When a turbine rotational speed does not increase even after the predetermined period of time has elapsed, as the turbine rotational speed decreases below a value lower by a predetermined value than a synchronous rotational speed in the (n+1)th gear, the ECU executes feedback control over the hydraulic pressure of the element B so that the turbine rotational speed becomes the value lower by the predetermined value than the synchronous rotational speed in the (n+1)th gear.

Abstract: A parameter ?(OUT) having an accelerator pedal position, a vehicle speed and a drive force as components is set according to information representing a driver's operation and information representing running environment of a vehicle. A gear is set according to the parameter ?(OUT) and a map determining the gear based on the accelerator pedal position, the vehicle speed and the drive force. A gear shift line is defined such that a rate of increase of the drive force with respect to the vehicle speed is zero or more. A down-shift line is defined such that the drive force decreases with increase in accelerator pedal position. Down-shift after up-shift as well as the up-shift after the down-shift are inhibited when both a condition that an amount of change of the accelerator pedal position after last gear shift is larger than a threshold and a condition that an amount of change of the drive force after the last gear shift is larger than the threshold are satisfied.

Abstract: A method for controlling a vehicles drivetrain including an engine and automatic transmission, such that transmission ratios are shifted within a range of transmission ratios in a continuous and/or stepped manner as function of preset target speeds that are adjustable via a vehicle speed control and actual vehicle inclinations in relation to the vehicles longitudinal axis. When the actual speed of the vehicle differs from a preset threshold speed, a request to change an actual ratio of the transmission is generated, if it has been determined that the output torque is smaller than a threshold value or an output torque required to adjust the preset threshold speed of the vehicle. The ratio of the transmission is shifted so the torque applied to the output is modified toward the output torque required to adjust the threshold speed.

Abstract: The invention relates to a vehicle integrated-control apparatus and method that sets a final control target by coordinating a control target primarily set based on an input of a driver with instruction values from the control systems; and that causes a drive control system to control a drive source and a stepped automatic transmission to achieve the final control target. With this apparatus and method, at least one of the control systems, which provide instruction values to be coordinated with the primarily set control target, is notified of a range of control targets that can be achieved at a current shift speed; a range of control targets that can be achieved by changing the current shift speed to a currently achievable shift speed; and a range of control targets that can be achieved without changing the current shift speed to another shift speed.

Abstract: A shift control method and apparatus of an automatic transmission for controlling a shift from one speed, achieved by engagement of a first and a second frictional element, to another speed, achieved by engagement of a third and a fourth frictional element. The method includes detecting a rotation speed of a turbine, detecting a rotation speed of at least one operating member of at least one planetary gear set of the automatic transmission, and controlling the shift according to the rotation speeds of the turbine and the operating member. The control includes overlapping a first shift, from the one speed to an additional speed, with a second shift, from the additional speed to the other speed. The additional speed has a gear ratio that is near a gear ratio of the one speed.

Abstract: A method of controlling a clutch-to-clutch transmission. The method includes detecting transmission slip speed that exceeds a predetermined amount for a predetermined time period. Based on the detecting, a shift of a gear ratio of the transmission is forced. When this method is implemented in a vehicle, loss of driver control of the vehicle can be prevented in the event of a non-commanded neutral condition in the transmission.

Abstract: An automotive automatic transmission control system is provided which is designed to increase the output of an engine in response to a driver's request to downshift a transmission for setting up the engine braking and to load the amount of working fluid to an on-coming clutch quickly during the downshift. The system works to determine whether the loaded amount of working fluid is excessive or lacking using the speeds of an input shaft of the transmission and the engine to correct the amount of working fluid to be used upon a subsequent downshift request. The use of the two speeds enables the fact that the loaded fluid amount is excessive which arises from a rise in the speed of the input shaft caused by the engine output increasing control, not by completion of the loading of the working fluid to the on-coming clutch to be found accurately.

Abstract: In shift control apparatus and method for an automatic transmission in which an engine speed is inputted, and a shift change in a shift stage of the automatic transmission is performed to make a gear shift, a shift revolution synchronization control in synchronization with the engine speed is performed and, in a case where the gear shift is made under a driving state in which there is a possibility of an occurrence of a shift shock, an engagement section which performs a power transmission under a presently selected shift stage is gradually released and another engagement section which enables a power transmission through the next selection scheduled shift stage is gradually engaged without an execution of the shift revolution synchronization control.

Abstract: Whenever a 4 to 3 shift condition is satisfied during a 3 to 4 upshift, 4 to 3 shifting is started before the 3 to 4 shifting is finished. The 4 to 3 shifting is executed according to a predetermined hydraulic control pattern. Therefore, responsiveness in shifting is enhanced.

Abstract: A shift control method for a gearset with greater than or equal to 5 speeds, allowing to perform a sequential shift and a multi-skip shift in relation to the multi-shift stages, contributing to an improved response during shifting. The shift control method comprises steps of performing a preceding shift control when disengagement components of a preceding shift stage and a final target shift stage are identical during skip shifting, then executing a one-stage skip control toward the final target shift stage if a certain set of required conditions are satisfied; and standing by for a predetermined time period without performing the preceding shift control when the disengagement components of the preceding shift stage and the final target shift stage are different during skip shifting, then performing a one-stage skip control toward the final target shift stage only if pertinent conditions are met.

Abstract: A method for controlling an automatic transmission in a vehicle is provided. The method selectively provides automatic engine braking for the vehicle. When it is determined that automatic engine braking is desired, the upshift schedule is increased, such that a higher vehicle speed is required to upshift for any given accelerator pedal position. The transmission is automatically downshifted to a lower gear to provide engine braking for the vehicle, when a vehicle acceleration threshold is exceeded. The automatic downshifting of the transmission can occur when the brake pedal is engaged, and when the brake pedal is disengaged.

Abstract: A shift control apparatus for a vehicular automatic transmission provided with a fuel cut apparatus which cuts off fuel supplied to an engine when an engine speed exceeds a predetermined value during deceleration of a vehicle, and an automatic transmission in which a gearshift is achieved with a clutch-to-clutch downshift in which a hydraulic friction device to be released is released and a hydraulic friction device to be applied is applied, further includes a controller. The controller corrects, through learning control, an apply pressure of at least one of the hydraulic friction devices to be operated for the clutch-to-clutch downshift such that an amount of drop in a rotational speed of an input shaft of the automatic transmission increases when that amount of drop is less than a predetermined value during the clutch-to-clutch downshift.

Abstract: In a vehicle in which a moderate throttle opening degree control of maintaining a degree of throttle opening that is less than a degree of throttle opening that corresponds to an accelerator operation is performed for a predetermined period following a beginning of the accelerator operation, if it is determined that a clutch-to-clutch downshift judgment has been made, the reduction of the engaging pressure of a disengage-side friction engagement device is restrained until it is determined that the moderate throttle opening degree control has ended. Therefore, even if the turbine torque is returned to a normal value at the end of the moderate throttle opening degree control, insufficient engaging torque is avoided, and the takeover of engaging torque for the clutch-to-clutch downshift is smoothly performed while the turbine torque is stable. Hence, occurrence of a shock related to the end of the moderate throttle opening degree control is suitably prevented.

Abstract: In a vehicle with a gear-shift transmission of a kind that requires a torque-free state to shift gears, the riding comfort is improved by a method of shifting gears where a gear shift is preceded by the steps of: reducing the vehicle acceleration at a time t1 from an existing level (1) to a first acceleration level (3), maintaining the vehicle acceleration at the reduced level (3) for a predetermined time interval, and at the end point t3 of the predetermined time interval, reducing the acceleration further to a second acceleration level that is lower than the first level.

Abstract: Described is a method for the control of a transmission of a motor vehicle, especially an automatic transmission, with hydraulically activated shifting elements. The shifting elements are shifted to engage or disengage by means of specified pressure pattern (pkab, pkzu) which have been input into an electronic control unit. In the said method, an applied pressure (pkab) on a disengaged shifting element, by the release of a force flow generated by a holding pressure (pkab-h) is reduced to a shift pressure (pkab-sd) and a transmission input speed of rotation (nt) experiences a change dependent upon the applied pressure (pkab) on a disengaged shifting element.

Abstract: An apparatus for controlling an automatic transmission of an automotive vehicle, which is shifted to a selected one of operating positions by an engaging action of a frictional coupling device, wherein an overshoot engagement control device is provided to shift the automatic transmission to the selected one operating position such that a shifting action of the automatic transmission is initiated while an input speed of the automatic transmission is lower than a synchronizing speed of the selected operating position. The overshoot engagement control device is arranged to control an engaging force of the frictional coupling device such that the input speed is first raised above the synchronizing speed and is then lowered down toward the synchronizing speed.

Abstract: A control strategy for a multiple-ratio transmission for an automotive vehicle comprising a shift valve system that responds to shift valve signals developed by a microprocessor controller, the controller being in communication with engine sensors indicating engine operating variables and transmission sensors indicating transmission operating variables, the shift valve system responding to shift signals developed by the microprocessor during coasting downshift of the vehicle from one gear ratio to a lower gear ratio with a closed engine throttle whereby torque reversals are avoided during coast-down, thereby eliminating inertia torque changes to improve the smoothness of coasting downshifts during cold engine operation.

Abstract: A down-shift is carried out when a) the sum of a dry force of a vehicle and a predetermined value, is smaller than a running resistance, and b) when an accelerator opening is larger than a threshold value which is based on vehicle speed, road inclination, and speed change step (gear position).

Abstract: A method/system for controlling downshifting in an automated mechanical transmission system (10) utilized on a vehicle. When a downshift from a currently engaged ratio (GR) is required (ES<ES.sub.D/S), skip downshifts (GR.sub.TARGET =GR-N, N>1) and then single downshifts (GR.sub.TARGET =GR-1) are evaluated in sequence. If throttle demand is high (THL>REF), skip downshifts are evaluated to determine if they can be completed at no greater than a reference value (ES.sub.DES =ES.sub.DES-DEFAULT +offset), which is higher than otherwise (ES=ES.sub.DES-DEFAULT) allowed.

Abstract: In executing a clutch-to-clutch gearshift based on the release and engagement of two clutches by the control of the hydraulic pressures of the clutches, the fluctuating magnitude of the output shaft r.p.m. (No in FIG. 2) of the automatic transmission is calculated, and the degree of the drag (tie-up) state of the clutches is detected on the basis of the calculated fluctuating magnitude. As a result, the pressure increasing/decreasing timings of the hydraulic pressures of the clutches can be optimized to realize a feedback control or learning control of higher precision.

Abstract: A vehicle automatic transmission control controls fluid pressure changes applied to a frictional engagement element which is being changed from an engaged state to a disengaged state at a stage before input shaft rotational speed starts to increase from the beginning of a down-shift control. The control instruction value is set to gradually decrease the applied fluid pressure and to increase the ratio of such decrease with elapsed time. Specifically, a solenoid is used to control the fluid pressure applied to a clutch. The duty-cycle instruction for the solenoid is determined based on a quadratic function expressed as: duty cycle value=initial value-at.sup.2.

Abstract: In a gearshift control apparatus for an automatic transmission which performs a downshift under power ON state, after a command for a clutch-to-clutch downshift has been issued, the hydraulic pressure of a higher-speed-stage side clutch is first lowered to raise the input r.p.m. of the transmission. When the beginning of rise in the input r.p.m. of the transmission has been detected, the hydraulic pressure of the higher-speed-stage side clutch is subjected to a feedback control so that the change rate of the input r.p.m. of the transmission may become a specific value. Upon the detection that the input r.p.m. of the transmission have come near to the synchronous r.p.m. of a lower speed stage, the hydraulic pressure of the lower-speed-stage side clutch is gradually raised, and simultaneously, the hydraulic pressure of the higher-speed-stage side clutch is subjected to a feedback control on the basis of the input r.p.m. of the transmission.

Abstract: Even if a rotational speed of an engine has already increased due to slipping of a fluid torque converter at the time of start of downshifting, a smooth downshifting is performed. For that purpose, there is obtained a speed change developing degree function K(etrm) of the rotational speed of the engine at the time of start of downshifting, the developing degree being dependent on an increase in the rotational speed of the engine due to slipping in the fluid torque converter. The function K(etrm) is obtained with a speed ratio "etrm" of the fluid torque converter at the time of starting of downshifting as a parameter. A boosting correction value QDNOFFZ is computed by multiplying a reference correction value QDNOFFZO by K(etrm) (step S108-5). The hydraulic pressure of the hydraulic engaging element on the disengaging side during downshifting is boosted by the amount of QDNOFFZ (step S108-6).

Abstract: In a method for the production of actuator signals as a function of sensor signals in an open-loop and/or closed-loop control system, the sensor signals are read into a data processing device and converted into internal input signals. The internal input signals are evaluated together with stored status information with the use of predetermined functions, whereby internal output signals and possibly new status information to be stored result. Actuator signals are derived from the internal output signals and fed to at least one actuator.

Abstract: The present invention prevents shift shock and reduces time required to execute the complete speed change operation in the case where a second speed change is commanded while a first speed change operation is still in progress. If a down-shift to a first speed stage is commanded during an up-shift operation from the first to the second speed, the hydraulic pressure in the second speed change operation is controlled in accordance with the state of the first speed change operation at the time of generation of the command for the second speed change. For example, if a down-shift to the first speed stage is commanded during the torque phase of an up-shift operation from first to second speeds, namely, before change in the rotational speed of the input shaft has started, only completion control of the down-shift operation is executed.

Abstract: If a shift to the 3rd speed is decided during the 5th-4th speed shift, in which the hydraulic servo for a second clutch is released by pressure regulation control, a changeover valve is switched by a solenoid valve so that the fluid pressure P.sub.C2 from the pressure regulating valve is conducted to a third clutch hydraulic servo. Thereby, the third clutch hydraulic servo pressure P.sub.C3 stands by at a predetermined engaging pressure P.sub.H and, at the same time, the servo-start of a fourth brake fluid pressure P.sub.B4 is performed by another pressure regulating valve. Meanwhile, the fluid pressure P.sub.C2 is released by an accumulator. After the servo-start ends and the 4th speed is established, the 4-3 speed shift control is performed, thus preventing shift shock and reducing shift duration.

Abstract: An automatic transmission control system for an automatic transmission including a hydraulic pressure control circuit which supplies locking and unlocking pressures selectively to a plurality of friction coupling elements to lock and unlock the selected friction coupling elements, changing a torque transmission path in a transmission gear mechanism to provide available gears, a specific one of which is achieved by locking and unlocking simultaneously specific friction coupling elements.

Abstract: A downshift control device for an automatic transmission is provided in which the transmission is shifted down by releasing an oil pressure from a first engaging element that has been engaged while applying an oil pressure to a second engaging element that has been released. This downshift control device determines whether a downshift command is generated to shift down the transmission while an accelerator pedal is being depressed, and detects a gear ratio that changes during the pedal-depressed downshift control. First control actuator controls the back pressure of a first accumulator provided in an oil path leading to the first engaging element, and second control actuator controls back pressure of a second accumulator provided in an oil path leading to the second engaging element.

Abstract: A method of controlling and regulating an automatic transmission with overlapping gearshifts. The change from the control mode to the regulating mode for the disengaging clutch (11) is made here when a defective engagement of the engaging clutch (12) is detected.

Abstract: A self-organizing fuzzy logic controller develops an adaptive pressure adder that modifies the magnitude of pressure supplied to a friction element of an automatic transmission. The controller uses a turbine speed versus engine torque table in KAM to store the adaptive pressure adder for each shift. Tables in KAM represent fuzzy rules which are altered based on shift performance criteria to produce a self-organizing fuzzy logic controller. The criteria, which define shift performance, include the ratio change slip time and the initial ratio change time divided by the desired slip time (called target ratio). The desired slip time is determined from a calibratable matrix. After a shifting event, an adaptive pressure adjustment is determined for the next shifting event having the same conditions. A two-input (slip time and target ratio) fuzzy logic controller is used to determine the pressure adjustment.

Abstract: A shift control apparatus in a vehicle automatic transmission, where down-shift is carried out from a high velocity step to a low- velocity step.A flatness-aiming control has a common targetted change rate with respect to a turbine rotational speed in the inertia phase, and aims a hydraulic command value for the engaging side element and a hydraulic command value for the releasing side element at flatness in the inertia phase with the passage of time.An initial value setting control sets an engaging side initial value and a releasing side initial value at the beginning of the inertia phase in response to the turbine torque and the turbine rotational speed.

Abstract: In a shift control apparatus in a vehicle automatic transmission, up-shift is carried out from a low velocity step to a high velocity step. When a rotational blow is generated, a controlling device controls the releasing side element of frictional engaging elements in such a target that the releasing side element of frictional engaging elements slips on the mating member with the engaging side element of frictional engaging elements moving for engagement.

Abstract: An automatic transmission control system including a hydraulic pressure control circuit which supplied locking and unlocking pressure to selectively lock and unlock the selected friction coupling elements so as to change a torque transmission path in the transmission gear mechanism and thereby to provide desired gears, a specific one of which is achieved by locking and unlocking simultaneously specific friction coupling elements.

Abstract: An automatic transmission control system for an automatic transmission including a hydraulic pressure control circuit which supplies locking and unlocking pressures selectively to a plurality of friction coupling elements to lock and unlock the selected friction coupling elements, changing a torque transmission path in a transmission gear mechanism to provide available gears, a specific one of which is achieved by locking and unlocking simultaneously specific friction coupling elements.

Abstract: A downshift control device for an automatic transmission is provided in which a drive command is generated to a shift actuator when a shift command to change a gear ratio of the transmission is generated, to switch a shift valve and change oil paths, thereby to release a first engaging element that has been engaged in a first gear position established by the automatic transmission before the shifting operation, and engage a second engaging element that has been released in the first gear position, so as to establish a second gear position after the shifting operation.

Abstract: The invention relates to a hydraulic changing device for a multi-ratio vehicle transmission, especially for a commercial vehicle such as a mobile excavator. The hydraulic changing device feeds gear actuator (3, 4) with pressure medium conveyed by a servopump (10). There is a control slide (26) which is acted upon by the effect of a control spring (33), on the one hand, and by a pressure in a low-pressure chamber (23), on the other. The low-pressure chamber (23) is coupled to a low-pressure pump (20) operating in dependence upon the engine speed. The arrangement is completed by a shuttle valve (6) and a leakage valve (5). The pressure prevailing in the low-pressure chamber (23) actuates the control slide (26), against the force of the control spring (23), in such a way that undesired changes from a higher to a lower gear are prevented. The hydraulic changing device, of the invention, is advantageously distinguished by its low structural and design expenditures.