Abstract: A control of a drive train for a wheel loader having one pressure-medium actuated brake and one transmission operated via a torque converter and at least one forward and/or reverse gear respectively actuated via a power shift clutch and one power take off wherein, when a predetermined value of the power delivered by the transmission to the power take off is exceeded, the pressure of the engaged power shift clutch for the forward or reverse gear is reduced to a residual level.

Abstract: A hydraulic system for controlling the engagement and disengagement of a friction element includes a source of line pressure, a source of exhaust pressure, a manual valve having a forward state and a reverse state, connected to the exhaust pressure source and line pressure source and including a first outlet and a second outlet, for opening and closing communication between said outlets and said pressure sources in response to changes in the states, a friction element communicating with the line pressure source through the manual valve in the reverse state, and a control valve including a port communicating with the friction element, the control valve producing control pressure at the port when the manual valve is in the forward state.

Abstract: A clutch control system for a standard transmission includes a gearshift lever sensor that is mechanically coupled to the gearshift lever to sense the position thereof and produce a gear state signal. A monitor device is also provided to produce a signal corresponding to the vehicle's speed. A selectively actuable latch mechanism has an unlock state to permit the clutch to move from its transmission disabling state to an enabling state but may move to a lock state to prevent the clutch from moving to the enable state. A controller responds to the gear state signal and the speed signal to place the latch mechanism in the lock state when the speed of the vehicle is above a pre-selected maximum speed for the selected gear state. A method implemented by this system is also disclosed.

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 transmission equipped with a continuously variable ratio-change mechanism CVT and a LOW rotational transmission mechanism GT, which are disposed parallel with each other, comprises a forward clutch 65 and a reverse brake 66, which are used to set a power transmission through the continuously variable ratio-change mechanism, a LOW clutch 46, which is used to set a power transmission through the LOW rotational transmission mechanism, and a control unit ECU and a hydraulic control valve HV, which control the engagement of the clutches and the brake. When the transmission is switched from its neutral mode to its in-gear mode, at first, the forward clutch 65 is brought gradually into engagement, and then it is released before the LOW clutch 46 is brought into engagement in a squat control.

Abstract: A control apparatus for a power train including a continuously variable transmission and a clutch arranged in series with the continuously variable transmission is provided in which an engaging pressure of the clutch is first reduced until a slip occurs, and is then increased after detection of the slip so as to re-engage the clutch, and an engaging pressure of the clutch to be established is calculated by giving an excess pressure to the engaging pressure at which the clutch is re-engaged, such that an excess amount of the transmitted torque of the clutch is set smaller than that of the continuously variable transmission. The control apparatus is adapted to determine a learned value as a correction value of the engaging pressure that is set in advance in accordance with an input torque applied to the clutch, based on the engaging pressure calculated by giving the excess pressure to the engaging pressure at which the clutch is re-engaged.

Abstract: A shift interlock mechanism that requires an operator to press a brake mechanism before changing transmission gears to prevent extra motion in the transmission, insuring a smoother shifting operation. The shift interlock mechanism with a brake arm that moves in a first direction to stop motion of at least a first ground engaging drive wheel and a shift arm that moves in a second direction to change movement of a vehicle.

Abstract: A power transfer apparatus 1 of a four-wheel drive vehicle includes, a clutch, an inversion detector, and controller. The clutch generates an engagement force that effects a driving force output from an engine to wheels of the vehicle via a transmission. The transmission includes the inversion detector 23, 27 for detecting inversion or non-inversion of a gear-shifting direction of the transmission 13. The controller 23 subjects the electromagnet to energization control such that torque to be transmitted by the clutch is decreased to a target value in accordance with an inversion signal pertaining to said gear-shifting direction detected by said inversion detector 23, 27.

Abstract: An apparatus for clutch braking in a multi-speed transmission comprising a prime mover, a transmission system, an output shaft and a torque converter. The transmission comprises a first stage and a second stage wherein the first stage comprises at least two range clutches and the second stage comprises at least two direction clutches. The range and direction clutches are slipped, locked and/or engaged to brake the system.

Abstract: The invention pertains to a motor vehicle with overspeed protector. The clutch in the power train of the motor vehicle can be operated in dependency upon the engine speed in such a way that it is disengaged or operates with slip when the engine speed exceeds a preselected limit while the clutch is engaged. The threshold value of the engine speed is ascertained on the basis of the prevailing (instantaneous) engine speed and the prevailing (instantaneous) or desired increase of transmission ratio. Gear shifting errors and overspeeding of the vehicle are thus prevented in a manner which is more reliable than by following prior proposals.

Abstract: The invention relates to a method and an apparatus for operating an automated change-speed gearbox of a motor vehicle. The control device of the change-speed gearbox communicates via signals with a control unit of an anti-block control system. To allow particularly comforatable operation of the change-speed gearbox, the invention envisages that, as a function of signals from the control unit of the anti-lock control system, the change-speed gearbox is set to a neutral position, an appropriate gear ratio is determined and this gear ratio is engaged.

Abstract: Hydraulic control system for a vehicle transmission connected to an output shaft from a hydraulic torque converter (1) with a hydraulically operated disc clutch for locking the torque converter and which has two hydraulically operated disc clutches for shifting. The control system has a low pressure circuit (30) with a low-pressure pump feeding fluid through the torque converter, and a high pressure circuit (34) with a high-pressure pump (35), which feeds fluid via valves (38) to the disc clutches. The high-pressure pump has variable displacement, which is regulated by the operating pressure of the disc clutch of the torque converter, so that the high-pressure pump is set to a lower displacement when this last-mentioned clutch is engaged than when it is disengaged.

Abstract: A vehicular transmission system is disclosed that includes an engine, a transmission having an input shaft, a master friction clutch for drivingly connecting the engine to the transmission, an inertia brake for selectively controlling rotation of the input shaft, and at least one control unit. The control unit includes logic rules that selectively disable operation of the inertia brake in response to a system operating condition during at least one mode of operation of the vehicular transmission system. The system also includes at least one input corresponding to a system operating condition and at least one output corresponding to a command to log a fault or disable operation of the inertia brake in response to the system operating condition during the at least one mode of operation. A control system and method for operating the vehicular transmission system are also disclosed.

Abstract: A strategy for overcoming a tooth butt condition includes changing a target closed clutch position over time. When a tooth butt condition exists, a controller selectively closes a clutch to provide limited engagement between the engine and the transmission. A first target closed clutch position is used on the first attempt. If the tooth butt condition is not resolved, the controller then changes the target closed clutch position to provide a different level of engagement between the engine and the transmission. This process is repeated until the tooth butt condition is resolved, a preselected period of time expires, a maximum number of attempts has been completed or the maximum desirable closed clutch position has been used.

Abstract: An interlock mechanism is provided for a transmission system having a gear unit with a plurality of selectable gear ratios. A manually operated clutch control pedal is manually movable from a clutch engaged position to a clutch disengaged position. The transmission has a pair of shift rails movable to select gear ratios. The shift rails have detent grooves which interact with a pair of detent balls. An interlock member is normally in a lock position wherein the interlock member engages both detent balls and holds them in the detent grooves to prevent movement of either or both shift rails. The interlock member is movable to a release position wherein the interlock member is disengaged from the both detent balls whereby the detent balls will allow one of the shift rails to be moved. An interlock spring is biased to urge the interlock member to the lock position.

Abstract: A control apparatus for controlling a shift operation sets an output Mout from a reference model M(s), which is ideally changed, as a target slip amount of a feedback controller Cpi(s). The controller Cpi(s) controls torque transmitted to an off-going friction engagement element for matching a control slip amount sp with the target slip amount. The characteristics of the controller Cpi(s) is determined for optimally performing a clutch-to-clutch shift operation during a lock-up clutch being engaged. When the lock-up clutch has been disengaged, an input shaft rotation speed is filtered by a notch filter NF for removing a frequency component in a predetermined frequency domain, wherein the control slip amount sp is obtained based upon the filtered input shaft rotation speed.

Abstract: A method for the control of a bi-directional overrunning clutch assembly (10) disposed within a vehicle transmission, including the steps of initiating a drive function control routine (112) within an electronic control unit and sensing the commanded gear ratio within the transmission. The method steps further include determining whether a first gear function (132) should be initiated based on the commanded gear ratio and determining whether a second gear function (150) should be initiated based on the commanded gear ratio. The method also includes sensing whether the reverse engagement members (24B) and the forward engagement members (24A) of the bi-directional clutch (10) are engaged when neither the first gear function (132) nor the second gear function (150) are initiated.

Abstract: The invention relates to a method for early recognition of abnormal occurrences in the operation of automatic or automated gearboxes wherein at least one variable Akraftschl. directly or indirectly characterizing the strain on elements which are to be coupled to each other in a non-positive fit is continuously determined after an n-th shift at least until a synchronous rev speed is reached or during a maximum shift period Tmax; wherein the variable Akraftschlüssig characterizing the strain on the elements that are to be coupled is mathematically combined with the time, or if several variables Akraftschlüssig Exist, said variables are mathematically combined with each other and the product of said combination is added up in the form of a variable Wsum; wherein the product thereof is compared with a first pre-definable or defined threshold value Wmax0 Which, if exceeded, defines a state from which damage can be deduced and the shift action is aborted.

Abstract: In a vehicle transmission system including a transmission having an input shaft driven by an engine, an output shaft, and a clutch for controlling the transfer of torque from the input shaft to the output shaft, the clutch is controlled by sensing the speed of the engine and controlling engagement of the clutch according to the sensed engine speed. The system normally operates in a mode wherein clutch engagement is controlled according to the position of a clutch pedal. An auto-clutch mode, wherein engine speed controls clutch engagement is invoked when the transmission is in gear, brake pedals are depressed, and the engine speed is less than a predetermined speed.

Abstract: A clutch pedal locking assembly for a vehicle having a manual transmission and a clutch. A latch assembly, when actuated, holds a clutch pedal down after the vehicle operator presses the clutch pedal down, thus leaving the vehicle clutch disengaged even when the operator removes his foot from the clutch pedal. When the latch assembly is deactivated, the clutch pedal will operate the same as a conventional clutch pedal in a manual transmission vehicle. The latch assembly may be activated and deactivated by a cable that connects to an activation collar on the gear shift lever.

Abstract: A transmission for changing a ratio of a rotational number of a power source and a rotational number of an output shaft by shifting a gear train provided between the power source and the output shaft by moving a shift fork. The transmission includes a shift drum for moving the shift fork, a clutch provided between the power source and the gear train, a shift spindle for urging the shift drum and the clutch. When the shift spindle is pivoted, lift of a clutch is started by pivoting a clutch arm. In accordance with pivoting the shift spindle, a sub arm is pivoted and preload is applied on a master arm by a preload spring. Thereafter, when the sub arm is further pivoted, the master arm follows the sub arm and a shift drum is pivoted via index pins. Since the preload is applied, when the clutch is disengaged, the shift drum is pivoted immediately, a shift fork is displaced and gears are switched.

Abstract: A working vehicle is provided which can be smoothly started with a large driving force, and uniformly conducts a various types of works even if a travel speed varies. A working machine such as a working pump, which is also driven by an engine for driving the vehicle, is mounted on the working vehicle. The power is transmitted from a crank shaft of the engine to wheels through a torque converter provided with a lock-up clutch and an automatic transmission. The crank shaft is also connected to a driving unit for driving the working pump through gears. A transmission ratio of the automatic transmission is set to a predetermined value corresponding with work modes J1-J6. In such a way, the work modes J1-J6 are set according to characteristics of the work, in which there exists a predetermined relationship between a work amount and a vehicle speed. Therefore, fertilizer, sand, and chemicals can be appropriately and uniformly spread through a changeover of the modes.

Abstract: A control apparatus for controlling a shift operation sets an output Mout from a reference model M(s), which is ideally changed, as a target slip amount of a feedback controller Cpi(s). The controller Cpi(s) controls torque transmitted to an off-going friction engagement element for matching a control slip amount sp with the target slip amount. The characteristics of the controller Cpi(s) is determined for optimally performing a clutch-to-clutch shift operation during a lock-up clutch being engaged. When the lock-up clutch has been disengaged, an input shaft rotation speed is filtered by a notch filter NF for removing a frequency component in a predetermined frequency domain, wherein the control slip amount sp is obtained based upon the filtered input shaft rotation speed.

Abstract: The invention relates to a method and an apparatus for operating an automated change-speed gearbox of a motor vehicle. The control device of the change-speed gearbox communicates via signals with a control unit of an anti-block control system. To allow particularly comforatable operation of the change-speed gearbox, the invention envisages that, as a function of signals from the control unit of the anti-lock control system, the change-speed gearbox is set to a neutral position, an appropriate gear ratio is determined and this gear ratio is engaged.

Abstract: A system includes a unit for controlling a transmission line of a motor vehicle with a transmission. The transmission has a plurality of wheel sets for engaging and disengaging transmission gears and a plurality of shift clutches which can be operated by an operating device for engaging and disengaging transmission gears. In the transmission, at least one shift clutch to be shifted is operable while a shifted shift clutch is still engaged. The unit (10) is designed to guide at least during one shifting operation the shift clutch (S1,3, S2,4, S5,6) to be shifted to its synchronizing point when the shifted shift clutch (S1,3, S2,4, S5,6) is still engaged, and to guide an input clutch (11) of the transmission at least before the end of a synchronizing operation of the shift clutch (S1,3, S2,4, S5,6) to be shifted by way of an actuator (12) of the transmission into its opening position.

Abstract: A hydraulic actuation system for an automated transmission system including an active clutch includes, a hydraulic clutch actuator for controlling engagement of the active clutch, a gear engagement actuator for controlling engagement of a gear, a hydraulic accumulator, a hydraulic fluid reservoir, a main control valve for selectively connecting the hydraulic clutch actuator and the gear engagement actuator to the accumulator or to the reservoir and an isolation valve for isolating the gear engagement actuator from the main control valve, when the clutch actuator is connected to the accumulator, the clutch actuator causing the clutch to engage when connected to the accumulator and causing the clutch to disengage when connected to the reservoir. Two such hydraulic actuation systems may be connected in parallel to control the clutches of a twin clutch transmission system, allowing the twin clutch transmission system to be driven in a restricted emergency mode, using only one clutch.

Abstract: A control system for a selective clutch that prevents interference with automatic engagement/disengagement of a friction clutch (2) when manual engagement/disengagement is selected at the time of starting a vehicle. The selective clutch includes an autoclutch device that automatically disengages and engages the clutch (2) using an actuator (10) under the control of a controller (6, 9). The selective clutch also includes a manual clutch device that allows engagement and disengagement of the clutch based on depressing of a clutch pedal (11). The clutch disengagement and engagement by the autoclutch device is prohibited, or the prohibition is canceled, based on a vehicle velocity (28), gear speed (23) of a gear box (3), and clutch pedal depression (16).

Abstract: A control system is utilized for the starting and running-down of a PTO shaft on an agricultural vehicle, such as a tractor. The hydraulically actuated clutch, as well as the other parts and sub-assemblies connected with the clutch as part of the drive, attain a maximum service life under all conditions of use. The control system, both in normal operating mode and also in management operating mode, protects the cardan shaft against destruction through too great an angle of flexion. Finally, in the management mode of operation, the control system prevents the occurrence of a loss of time, which would reduce the effective time of use of the tractor with the tool in question, and renders impossible a stalling of the engine when starting the PTO shaft through too early ground contact of the tool, in which the PTO shaft is not yet turning.

Abstract: A torque transfer system, particularly an automated shift transmission of a motor vehicle, has a movable shifter element that is subject to a position-dependent force. The gear positions of the transmission correspond to minima of potential energy of the position-dependent force, so that the movable element will have a tendency to fall into the nearest one of the shift positions. To perform a gear shift, the movable shifter element is moved into the vicinity of the targeted gear position by means of a control device directing a shift actuator. When the movable shifter element has stopped moving within a given tolerance band of the targeted position, the control device generates a stall-releasing signal, e.g., a series of pulses of alternating polarity to overcome a holding force or holding torque of the movable element, so that the latter will seek a position of minimum potential energy and thus move towards the targeted gear-shift position.

Abstract: Disclosed is a shift control method comprising the steps of determining if an input shift signal is a power-on upshift signal; determining if driving conditions satisfy power-on upshift learn conditions if the input shift signal is a power-on upshift signal; performing power-on upshift control if power-on upshift learn conditions are satisfied; learning an initial fill time and completing shifting; determining if shifting is completed; determining if run-up occurred during the shift operation if shifting is completed; determining if interlocking occurred if run-up did not occur; determining, if interlocking occurred, if the interlocking is above a predetermined level; and learning a fill time if the interlocking is above the predetermined level.

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: The present invention provides a clutch connection method which controls the disconnection/connection of a wet friction clutch on the basis of a duty pulse outputted from an electronic control unit. When the clutch is connected, the electronic control unit initially outputs a start duty (Dst) for largely connecting the clutch as far as the vicinity of a torque point, and, thereafter, outputs, at prescribed time intervals (&Dgr;t), a gradual connection duty (Dk) for gradually connecting the clutch, and determines a gradual connection duty value on the basis of a clutch input/output side revolution difference &Dgr;N. Since the clutch is gradually connected while monitoring the clutch connection state, variations between connection times and connection shock, resulting from individual clutch differences or the like, can be eliminated, whereby it is possible to achieve a stable feel.

Abstract: A control unit controls a lockup duty ratio to be maintained at a first duty ratio, which is the minimum value within such a range as not to slip a lockup clutch, during a period of time since a decision is made to perform a shifting operation until an actual shifting operation is started. The control unit then lowers the lockup duty ratio to a corrected (learned) second duty ratio and gradually lowers the lockup duty ratio from the second duty ratio at a predetermined rate of change so that a slip revolutionary speed can be equal to a target slip revolutionary speed when the shifting operation is finished. Alternatively, the control unit corrects the rate of change while maintaining the second duty ratio at a uniform value so that the slip revolutionary speed can be equal to the target slip revolutionary speed when the shifting operation is finished.

Abstract: A method and device for a coupling (2) in a motor vehicle, transmission (1) are proposed in which the coupling is controlled and regulated during three operational states via a first regulating circuit (3). The regulated quantity corresponds to the actual value of a differential rotational speed of the coupling (2). The first state corresponds to a starting operation, the second state to the operation with constant ratio and the third state exists when a gear shift under load or a change of ratio from a first to a second ratio step of an automatic transmission (1) is initiated.

Abstract: A transmission system for vehicle transmission mechanism (B) having a low speed hydraulic clutch (CL) and a high speed hydraulic clutch (CH) as a wet multi-disk clutch for transmission, wherein both the low speed hydraulic clutch (CL) and the high speed hydraulic clutch (CH) are disengaged so as to disconnect a transmission of an engine power to the transmission system, namely, so as to bring a main clutch into off condition, a dry clutch device (A) is installed on the upstream side of transmission of the transmission mechanism as a corotation prevention mechanism, only the low speed hydraulic clutch (CL) of large capacity is used as an inching clutch to bring the main clutch into a partial engaged condition when the main clutch is moved to on or off in the transmission mechanism (B) and, when the main clutch is operated from off to on with a shift lever (91) set at a high speed position, hydraulic pressure control is performed so that the high speed hydraulic clutch (CH) is brought into off condition and the

Abstract: The invention relates to a transmission system with a shift mechanism for controlling the transmission system, a control device for controlling a transmission system with a shift mechanism, a method for controlling such a transmission system or shift mechanism, as well as an application for the transmission system.

Abstract: In a power transmission apparatus for a vehicle having a hydraulic pressure type clutch capable of switching to transmit and cut power between a crankshaft of an engine and driving wheels and a clutch control valve for controlling hydraulic pressure provided to the clutch, the operational characteristic of the hydraulic pressure clutch is made variable and an adjuster mechanism for compensating for a wear amount of clutch plates is dispensed with. A clutch control valve includes a valve housing having an input port connected to a hydraulic pump and an output port connected to a clutch. A spool is capable of switching to communicate and cut the input port and the output port and is slidably fitted in the valve housing. Furthermore, a linear solenoid is coaxially connected to the spool and is capable of controlling output hydraulic pressure from the output port to a value in accordance with input current of the linear solenoid.

Abstract: The present invention provides an apparatus and a method for controlling automatic transmission of a motor vehicle having an engine and an automatic transmission including a clutch with an actuator for changing gear position comprising a detecting means for detecting a completion of the changing gear position and a signal generating means for generating a control signal to the actuator for applying continued pressure to the clutch for a predetermined time after the completion of the changing gear position.

Abstract: Vehicle gearbox with a control shaft rotatably and axially displacebly mounted transversely to the axial direction of the vehicle gearbox, the rotational movement of the control shaft from a neutral position effecting, via motion-transmitting elements, engagement of a gear speed. A lock element cooperating with the control shaft is coordinated with a sensor sensing the position of a clutch connected to the gearbox, and locks the control shaft in the neutral position when the clutch pedal is not depressed.

Abstract: A torque transfer system, particularly an automated shift transmission of a motor vehicle, has a movable shifter element that is subject to a position-dependent force. The gear positions of the transmission correspond to minima of potential energy of the position-dependent force, so that the movable element will have a tendency to fall into the nearest one of the shift positions. To perform a gear shift, the movable shifter element is moved into the vicinity of the targeted gear position by means of a control device directing a shift actuator. When the movable shifter element has stopped moving within a given tolerance band of the targeted position, the control device generates a stall-releasing signal, e.g., a series of pulses of alternating polarity to overcome a holding force or holding torque of the movable element, so that the latter will seek a position of minimum potential energy and thus move towards the targeted gear-shift position.

Abstract: A hydraulic actuation system for an automated transmission system including an active clutch includes, a hydraulic clutch actuator for controlling engagement of the active clutch, a gear engagement actuator for controlling engagement of a gear, a hydraulic accumulator, a hydraulic fluid reservoir, a main control valve for selectively connecting the hydraulic clutch actuator and the gear engagement actuator to the accumulator or to the reservoir and an isolation valve for isolating the gear engagement actuator from the main control valve, when the clutch actuator is connected to the accumulator, the clutch actuator causing the clutch to engage when connected to the accumulator and causing the clutch to disengage when connected to the reservoir. Two such hydraulic actuation systems may be connected in parallel to control the clutches of a twin clutch transmission system, allowing the twin clutch transmission system to be driven in a restricted emergency mode, using only one clutch.

Abstract: A vehicle clutch engagement condition determining apparatus determines the engagement condition of a clutch for disengaging an engine from a transmission. This determining apparatus estimates a motor speed corresponding value through an ECU, sets the motor speed corresponding value to the target speed of an electric motor when a gear shift lever of the transmission is operated, determines a control current value for controlling the speed of the electric motor so that the speed of the electric motor detected matches the target speed while drive wheels are driven by the electric motor and determines the engagement condition of the clutch based on an electric current deviation.

Abstract: A hydraulic actuation system for an automated transmission system including, a hydraulic clutch actuator (22) for controlling engagement of a clutch (14), a gear engagement actuator (114,115) for controlling engagement of a gear, said gear engagement actuator (114,115) being in the form of a double acting ram having first and second working chambers (118,119) acting on opposite sides of a piston (116,117), a main control valve (120), the main control valve (120) selectively connecting the clutch actuator (22) and/or the gear engagement actuator (114,115) to an accumulator (275) or to a reservoir (278); a gear engagement control valve (144,146) selectively connecting the first and second working chambers (118,119) of the gear engagement actuator (114,115) to the main control valve (120) or to the reservoir (278); an electrically driven pump (223) being provided to charge the accumulator, the pressure of fluid supplied by the pump being controlled by variation of-the current driving the pump (223).

Abstract: In a transmitting system for a small-sized vehicle in which a crankshaft of an engine and an input shaft of a multi-stage transmission are connected to each other through a fluid transmitting device, the fluid transmitting device including a pump impeller leading to the engine, and a turbine impeller leading to the transmission, a shifting clutch is interposed between the crankshaft of the engine and the multi-stage transmission in a series relation to the fluid transmitting device. Thus, a creep phenomenon of the fluid transmitting device can be eliminated, and the shifting operation of the transmission can be conducted lightly, by bringing the shifting clutch into its OFF state.

Abstract: An automatic transmission for a vehicle comprises a torque converter TC equipped with a lock-up clutch 4. This automatic transmission further comprises FIRST˜FOURTH speed clutches 31˜34 for a shift control executing a shift from an off-going speed ratio to an on-coming speed ratio by controlling the release of the hydraulic pressure from the off-going clutch and by controlling the supply of the hydraulic pressure to the on-coming clutch. A control system comprises first and second off-going pressure releasing valves 70 and 80, which release the hydraulic pressure from the off-going clutch during the shift, a lock-up control valve 40 and a lock-up timing valve 50, which control the engagement of the lock-up mechanism, and a linear solenoid valve 60, which supplies a control pressure to these valves and controls the operation of these valves.

Abstract: An interlock system for use with a cutting assembly of a lawn tractor is disclosed. The interlock system automatically disengages the cutting assembly when the lawn tractor is shifted into a reverse mode and automatically re-engages the cutter assembly when the lawn tractor is subsequently shifted into a non-reverse mode.

Abstract: A pressure control apparatus and method are provided for controlling hydraulic clutches of a backward and forward drive switching device mounted in a transmission of a working vehicle such as a tractor. When a backward and forward drive switching shuttle lever is operated, a current supplied to an electromagnetic proportional valve is controlled to gradually increase the pressure for a hydraulic clutch corresponding to a direction of movement. When a propelling drive connecting and disconnecting clutch pedal is operated, the pressure for that hydraulic clutch is controlled through the electromagnetic proportion valve, based on a depressed position of the pedal. When the operator switches the shuttle lever from forward to backward or vice versa, a microcomputer causes the shuttle control current to rise at a point of time of start of a clutch engaging operation of the clutch pedal.

Abstract: A vehicle clutch control system that can eliminate discomfort due to a sudden start of a vehicle. The vehicle clutch control system includes an engine speed detector (203) for detecting an engine revolution speed, and an engine controller (211) for controlling an accelerator opening of an engine (222). A vehicle speed detector (204) is also provided for detecting vehicle speed. A clutch actuator (212) engages and disengages a friction clutch (304), and a clutch controller (205) controls engagement and disengagement of the clutch by giving commands to the clutch actuator. In a vehicle start stand-by state in which the vehicle speed is zero and a certain start gear has been selected, if the engine speed detected by the engine speed detector (203) is higher than a predetermined speed, then a clutch engaging control is not performed because otherwise the vehicle would start suddenly upon clutch engagement.

Abstract: A transmission for changing a ratio of a rotational number of a power source and a rotational number of an output shaft by shifting a gear train provided between the power source and the output shaft by moving a shift fork. The transmission includes a shift drum for moving the shift fork, a clutch provided between the power source and the gear train, a shift spindle for urging the shift drum and the clutch. When the shift spindle is pivoted, lift of a clutch is started by pivoting a clutch arm. In accordance with pivoting the shift spindle, a sub arm is pivoted and preload is applied on a master arm by a preload spring. Thereafter, when the sub arm is further pivoted, the master arm follows the sub arm and a shift drum is pivoted via index pins. Since the preload is applied, when the clutch is disengaged, the shift drum is pivoted immediately, a shift fork is displaced and gears are switched.

Abstract: During a shifting operation to slide a shift gear of an auxiliary change speed device, clutches of a backward and forward drive switching device acting also as a propelling clutch and of a main change speed device are automatically disengaged to place these devices in neutral state. After the shift gear is switched to a high-speed position or low-speed position, the clutches of the main change speed device are automatically engaged to return the main change speed device to a transmitting state. After the main change speed device returns to the transmitting state, the clutches of the backward and forward drive switching device are automatically engaged to return the backward and forward drive switching device to a transmitting state.