Abstract: A cylindrical cylinder chamber formed by a casing and having inlet and outlet ports for pressure liquid at its both axial ends is installed in a liquid passage communicating a liquid chamber of the master cylinder device with a liquid chamber of the slave cylinder device. A cylindrical friction member divided circumferentially into plural pieces contacting with a peripheral wall of the cylinder chamber, a moving body carrying the friction member, plural first urging members fitted to the moving body for pressing the friction member onto the peripheral wall of the cylinder chamber, and a second urging member for urging the moving body in its axial direction in order to locate the moving body at a prescribed axial position of the cylinder chamber, are installed in the cylinder chamber. An orifice is formed on the moving body or the friction member in the axial direction.

Abstract: In a work vehicle including a hydraulic clutch for a transmission system, the invention discloses an art of quickly yet shocklessly controlling the engagement of the clutch by properly judging a preliminary oil pressure condition and a half-clutched condition through a detection of torque developed in the transmission system.

Abstract: A hydraulic control apparatus for a transmission comprising a hydraulic change speed clutch, an oil line connecting the change speed clutch to an oil pump, an electromagnetic proportional reduction valve mounted on the oil line for varying oil pressure output to the change speed clutch in response to control current applied to the reduction valve, a microcomputer for producing the control current and applying the same to the reduction valve, and a command unit for transmitting a command to the microcomputer to engage the change speed clutch.

Abstract: A controller for an automatic transmission hydraulic clutch includes a hydraulic clutch engaged by hydraulic pressure, a hydraulic pressure control valve for regulating the hydraulic pressure, and a detector for detecting a condition immediately before engagement of the hydraulic clutch based upon a change in the hydraulic pressure. A timing controller adjusts timing to change a control force in the hydraulic pressure control valve in response to detection of a condition immediately before engagement of the clutch.

Abstract: A clutch assembly is provided for selectively establishing a drive connection between a pair of relatively rotatable members. The clutch assembly includes a series of interleaved plates operably effective when axially compressed to couple the rotatable members. A fluid pressure operated clutch actuator is provided for effecting clutch engagement and regulating the torque carrying capacity of the clutch assembly. The clutch actuator includes an annular clutch engaging face area. The present invention contemplates arranging a series of deflectable springs between the annular face area on the clutch actuator and the interleaved plates to provide a gradual deceleration of the clutch actuator during clutch engagement in a manner significantly reducing impact loading and associated torque peak to the clutch assembly.

Abstract: In a fluid controlled automatic transmission for a motor vehicle, a fixed orifice which restricts communication between a low clutch source of line pressure and a friction element which is engaged in forward speeds, is by-passed for a predetermined period following a neutral-to-drive select to allow the friction element to rapidly engage while attenuating selection shock.

Abstract: A propelling clutch apparatus for a working vehicle comprises a friction type hydraulic clutch mounted on a propelling line, a valve for adjusting an oil pressure applied to the hydraulic clutch, a sensor for detecting angular acceleration of a rotary shaft included in the propelling line, and a control unit for controlling the hydraulic clutch in response to a change in a vehicle running state. The control unit effects controls in three stages. The first stage includes a preliminary step of narrowing spaces between friction disks of the hydraulic clutch by applying the oil pressure at a maximum level to the hydraulic clutch for a predetermined time from receipt of a clutch engaging command, and a subsequent main step of applying the oil pressure with predetermined characteristics. The second stage is for maintaining the hydraulic clutch in a half-clutch state when the angular acceleration in an accelerating direction or a decelerating direction reaches a predetermined value.

Abstract: An anti-vibration system (10) for the foot pedal (11) of a hydraulic clutch release system (9) utilizes a pulse dissipating canister (30) interposed between a first conduit portion (20) and a second conduit portion (21). The first conduit portion (20) communicates between a slave cylinder (22) and the canister (30), and the second conduit portion (21) communicates between a master cylinder (15) and the canister (30). The canister (30) has a hollow interior chamber (31), which is axially bounded by laterally spaced, circular front and rear walls (32 and 34, respectively) and circumferentially bounded by an annular wall (34) which extends between the front and rear walls (32 and 33) to define the outer periphery of the canister (30). The first conduit portion (20) communicates with the hollow interior chamber (31) of the canister (30) through the center portion of the front wall (32).

Abstract: A lock-up device for a torque converter, in which a piston actuated by hydraulic force and a lock-up damper are disposed between a front cover and a turbine wheel of the torque converter, a pressing force of the piston causes both friction surfaces of a friction plate of the lock-up damper to press on a friction plate of the front cover, and plural hydraulic chambers are provided by forming a pressure surface of the piston into a multiple-stage structure. A hydraulic chamber located at the most inner peripheral side is connected to a passage of hydraulic oil. The plural hydraulic chambers are connected with each other through fine clearances. A pressure area of the piston in the most inner peripheral side hydraulic chamber is set to a size which does not permit the piston to press on the front cover side friction plate under a state where the hydraulic oil is filled only in the most inner hydraulic chamber.

Abstract: Fluid systems for controlling clutch engagement of a vehicle drive train normally have modulating pressure relief valves to aid in smooth clutch engagement. It is desired in such systems to ensure that the system pressure is reduced during a shift so that the load piston of the modulating pressure relief valve is fully reset prior to engagement of the vehicle drive train. In this arrangement, a fluid system is provided which has a plurality of clutches. In order to ensure that the load system is fully reset, a load piston reset control mechanism is provided which establishes a path to vent the pressurized fluid from a load piston pressure chamber of a modulating presure relief valve in response to the pressure of the fluid in one of the clutches being below a predetermined pressure level.

Abstract: In a proportional pressure reducing valve including a spool having a first end connected to a solenoid and a second end exposed to a feedback chamber, and formed with a groove for allowing a supply port to communicate with an output port when the spool is driven by the solenoid in proportional to solenoid current under balanced condition of an axial force of the solenoid and feedback pressure, the pressure reducing valve further comprises a valve for allowing the feedback chamber to communicate with a drain port to control the valve into inbalanced condition to momentarily raise output port pressure up to supply pressure, when the hydraulic output pressure within the feedback chamber rises beyond a predetermined relief pressure.

Abstract: A fluid pressure control for a transmission having a fluid pressure operated clutch includes a pressure regulating piston communicating with a pressurized fluid source for affording fluid pressure to the clutch; a load piston disposed in a common bore with the pressure regulating piston wherein the pistons are reciprocally disposed in such common bore and are biased away from one another by an associated spring; and a signal pressure chamber is formed between an end of the bore and an end wall of the load piston and communicates with a fluid passage running from the pressurized fluid source to the clutch. Concaved fluid communication grooves are provided in a sliding face of the load piston wherein a first groove communicates with the signal pressure chamber, a second groove communicates with a discharge port and a third groove communicates with the pressurized fluid source via a timing orifice.

Abstract: A hydraulic control system for a transmission including a speed transmission assembly, a range transmission assembly, and a hydraulically actuated master clutch for selectively coupling the transmission assemblies. The speed transmission assembly includes a plurality of hydraulically actuated clutch assemblies for effecting different forward output speeds and at least one reverse output speed. The range transmission assembly also includes a plurality of hydraulically actuated clutch assemblies. The control system includes a valve body connected to a hydraulic source of fluid pressure. A plurality of control valves are positioned in the valve body by an operator controlled shift lever. The control valves direct fluid pressure to various clutch assemblies in the speed and range transmission assemblies to condition the transmission into a forward, reverse, or neutral mode of operation as a function of shift lever position.

Abstract: A transmission control system for actuating a hydraulically controlled vehicle transmission that includes a pair of shiftable valve members determining four range speed conditions and two shiftable valve members determining whether the vehicle is in forward or reverse. Operating in conjunction with the speed range valve members is a fill control system which provides for rapid filling of the clutches and a pressure control system which provides for the controlled rate of energization of the clutches once the clutches have been filled to eliminate shift shock.

Abstract: In an automotive transmission, an improved accumulator of the piston-cylinder type. The piston and cylinder are formed of the same material, e.g., aluminum, whereby the two components thermally expand at the same rate, thereby providing leak-free operation over wide operating temperature ranges. Spring steel piston rings are used in pairs to provide redundant seals, thereby giving an added measure of seal assurance.

Abstract: Inching valves for providing controlled slow movement of a vehicle normally have a valve mechanism therein to control the pressure level of the fluid being directed to the driving clutch of the vehicle. Upon release of the pedal, a sudden jerk of the vehicle may occur. The modulating inching valve of the subject arrangement provides a housing having a valving mechanism slidably disposed therein and operative to selectively block communication between an inlet port and an outlet port. The modulating inching valve further includes an input actuator mechanism operative to selectively control the valve mechanism in response to the position of the operator's inching pedal. Through a portion of a predetermined travel distance of the input mechanism the operator controls the rate of pressure being supplied to the fluid actuated device and during the remaining portion of the predetermined travel distance the modulating relief valve automatically controls the rate of pressure rise.

Abstract: The present invention is an air control valve of an air clutch wherein an air valve assembly interlocking with an operated quantity of a clutch pedal is provided for controlling an air pressure supplied from an air pressure source to the air clutch. Control mechanism is provided for controlling a valve-open pressure of the air valve assembly by a hydraulic pressure from a master cylinder interlocking with the clutch pedal. The control mechanism includes first, second and third spring members of which spring constants gradually decreases in this order, and the valve-open pressure of the air valve body is adapted to be controlled while switching spring forces of the spring members in accordance with the operated quantity of the clutch pedal.

Abstract: A hydraulically actuated clutch is included in a four wheel drive device included in a vehicle power train, and is utilized for torque distribution between the front vehicle wheels and the rear vehicle wheels. A hydraulic control device for this torque distribution clutch includes a device for producing a control hydraulic fluid pressure for this clutch according to an oscillatory method such as a duty factor method or a dither method, an output conduit for conducting this control hydraulic fluid pressure out from this device for producing it, and a device for smoothing hydraulic pressure fluctuations in this output conduit.

Abstract: A manually operable creep control mechanism for a tractor of the like having multiple direct drive gears and a creep clutch. The mechanism comprises an elongated arm pivotally mounted on the control box cover plate adjacent the slot through which the gear shift lever travels to shift into the direct drive gear positions. In a first position, the arm is clear of the slot and the gear shift lever is free to move through the entire range of gear positions, while preventing inadvertent pivoting of the arm out of the first position once the lever is in a predetermined low gear, such a fourth. When pivoted to a second position, the arm lies across the slot and limits shifting of the lever to a predetermined higher gear, such as twelfth, while preventing inadvertent movement of the arm out of the second position once the lever is at or beyond the fourth gear position. A flexible switching cable is connected to the arm and an electrical switch for actuating the creep clutch.

Abstract: A hydraulic load power train control for reversible shifting with a pressure control device for the controlled build-up of a shift clutch pressure, a foot clutch valve for arbitrary control of the shift clutches, and a manually operable shift valve for shifting of the reversible power train. The foot clutch valve is connected parallel to the pressure control device. The pressure control device is formed by a changeover valve indirectly reversible by the shift valve by which the pressure controlled in the supply pressure line can be fed to two shift pressure lines which are connected to a valve device. At the same time, the valve device is so controlled by the foot clutch valve that the effective shift clutch pressure can be controlled without influencing the position of the changeover valve as a function of the actuation of the foot clutch.

Abstract: A transmission includes a range selector valve that eliminates the possibility of unintentional simultaneous multiple gear engagement by a fail safe arrangement of fluid flow paths and valving. A pair of parallel paths connect to clutches that operate a high-low power shift transmission and a multiple speed power shift main transmission. The fluid flow path to the multiple speed power shift main transmission clutches is valved to select either a first or second group of speed/direction settings. Each of these groups then includes at least one valve to select a particular transmission speed or direction setting.

Abstract: A vehicle includes an engine and an automatic transmission which has a fluid torque converter, a forward clutch, and a manual range setting valve. Idling control for providing anti creep control is performed by, during engine idling time while the manual range setting valve is set to a forward driving range and the vehicle is substantially stationary, reducing the engagement pressure of the forward clutch by reducing the actuating pressure provided to it. A rotational speed associated with the fluid torque converter is detected, and the actuating pressure provided to the forward clutch is controlled so that the rotational speed associated with the fluid torque converter does not drop below a certain rotational speed value. Thereby good anti creep control is provided. A system is also disclosed for performing the method.

Abstract: A method of controlling a direct-coupling mechanism of hydraulic power transmission device of an automatic transmission for an automotive vehicle, wherein the transmission capacity of the direct-coupling mechanism is controlled such that the valve of a predetermined parameter indicative of an amount of relative slip between input and output members of the hydraulic power transmission device which are mechanically engaged with each other by the direct-coupling mechanism lies within a predetermined reference range. The predetermined parameter value is detected and the detected value is compared with the predetermined reference range. A desired value of the predetermined reference range and a predetermined period of time are determined on the basis of the comparison result. The transmission capacity is controlled to the determined desired value for the determined predetermined period of time.

Abstract: A selectively engageable friction torque transmitter has a housing in which is slidably disposed a piston to which housing is drivingly connected a plurality of friction discs or plates. The transmitter further includes a hub member to which are drivingly connected a plurality of second friction plates or disks interleaved with the aforementioned first plates. The first plate closest to the piston has a portion of the outer periphery thereof removed to permit fingers on the piston to bypass said plate and to be in close proximity with the next of the first plates. When the piston is initially moved axially to cause engagement of the friction transmitter, the first plate closest to the piston does not transmit torque while the remaining first plates and the associated second plates do transmit torque. An apply ring on the piston is placed in abutment with the first plate after initial engagement, to cause all of the interleaved plates to be frictionally engaged.

Abstract: A control system for controlling a fluid pressure to engage a start clutch of a vehicular automatic transmission has an actuator such as a solenoid valve for varying the fluid pressure supplied to the start clutch, a group of sensors for sensing one or more operating conditions of the vehicle and producing a start signal representing a start of the vehicle, and a controller such as a microcomputer for controlling the fluid pressure by sending a control signal to the actuator. In order to ensure a smooth start of the vehicle from a standing position in which the start clutch is disengaged, the controller varies the value of the control signal upon receipt of the start signal in such a manner that the control signal rises immediately, then falls rapidly to a low value, and finally increases gradually from the low value to an ultimate value.

Abstract: In an automatic transmission having a four-element two-stage torque converter and a planetary gear transmission which carries out a change-over operation of drive stage of plural planetary gear elements by hydraulically engaging and disengaging plural friction elements from the rear stage of the torque converter transmitting engine power by means of fluid; a drive stage control mechanism for automatic transmission, in which a piston carrying out the engagement and disengagement of the friction members by means of hydraulic force. The pressure surface of the piston is formed into plural concentric stepped surfaces. A pressure oil passage port interconnecting with a control valve for controlling charge and discharge of hydraulic pressure is provided at any one stage of the plural stepped surfaces. A passage leading the hydraulic pressure from such any one stage to another stage and having a throttling function is provided.

Abstract: A hydraulic circuit construction for a power shift transmission having logical operation valves mounted on a pressure oil supply passage connecting a hydraulic clutch to a pressure oil source, the logical operation valves being operable to engage and disengage the hydraulic clutch by opening and closing the pressure oil supply passage in response to a switching operation of a change speed device connected upstream of and in series to the hydraulic clutch. The pressure oil supply passage has mounted thereon a pressure control device including a first valve mechanism, a second valve mechanism and an orifice parallel-connected to the pressure oil supply passage, and an accumulator is mounted between the pressure control device and the hydraulic clutch to assure a speedy and smooth operation of the hydraulic clutch.

Abstract: In a creep preventing device of the type in which an oil discharge passage communicating with an oil tank is branched from an oil feed passage for supplying an operating oil pressure to a starting clutch or other starting elements of an automatic transmission of a vehicle and an electromagnetic valve capable of closing the oil discharge passage under the demagnetized state and opening it under the excited state is disposed in the oil discharge passage, a method of controlling the creep preventing device is characterized in that when the electromagnetic valve is returned from the excited state to the demagnetized state, the electromagnetic valve is chopped a predetermined number of times. This method can re-connect the starting elements smoothly without incurring any shock.

Abstract: A ships propulsion transmission system with at least one engageable friction clutch (10, 18) in the drive line between the ship engine (28, 30) and propeller (26), characterized by a device (20, 70, 6, 14, 76, 108) for setting the operating pressure of the friction clutch (10, 18) during the starting up process time-dependent and sequentially so that the operating pressure during the starting up process, is at least once, at a peak level and then subsequently is at a lower intermediate level, before it then is held at the final level.

Abstract: The transmission control for a vehicle hydraulic transmission includes a sequence control valve that includes a shuttle valve and an interconnected sequence valve which are connected with speed and direction clutches of the transmission. The shuttle valve senses the drop in pressure in the direction clutches when they are shifted to actuate the sequence control valve to initially dump the speed clutch and then to keep that clutch disengaged until the direction clutch has fully re-engaged.

Abstract: An electrically controlled valve for automatically controlling the engagement of the clutch in heavy vehicle gear transmissions giving a "soft shifting" action. The position of a three way, three position, pressure actuated, directional valve is controlled by an electrically proportional and controlled relief valve which regulates the pressure on the directional valve. In the first position, the clutch is communicated to tank. In the second position, there is full flow to the clutch. In the third position, there is first a restricted flow to and then control of the pressure on the clutch by the relief valve.

Abstract: In a self-propelled working vehicle having a speed change mechanism wherein a plurality of change gears journaled on a shaft are coupled one at a time by key means disposed within and shiftable along the shaft, fluid-actuated clutch is provided for interrupting input of power to the speed change mechanism before shifting operations. For protecting gear-engaging clutch portion of the key means for damage, fluid pressure applied to the clutch from a disengaged condition thereof is increased gradually by a relief valve including a pressure-modulating control piston. For disengaging the clutch before shifting operations, an unloader valve is provided which is actuated by moving a speed change lever along a direction other than the key-shifting direction.Relief valve means also acting as an unloader valve for disengaging the clutch is disclosed. Differential-locking clutch is also disclosed which is operated by fluid for actuating the clutch in the transmission path.

Abstract: A pressure modulation valve, for supplying a smooth pressure increase, having desired characteristics, to a load port in a hydraulic control system. A single spool provides initial and final bypass phases of rapid pressure rise, and an intermediate modulated phase. The pressure characteristics can be adjusted by varying the loads and openings.

Abstract: The present invention relates to a variable orifice device for modulating a clutch oil pressure of a power transmission. The device includes a body member having a pocket and a first and a second port. The pocket is open to one side of the body member with the first port connecting the pocket to an oil pump and the second port connecting the pocket to a modulator valve device. A plate member is arranged in the pocket and has a passage and a plurality of orifices. Each of the orifices has a different diameter. A selected one of the orifices communicates with the second port and the passage communicates with the first port. A cover member is arranged in the pocket and has a recess for connecting the passage to the selected one of the orifices.

Abstract: A direct-coupling control system for a fluid gear in an automatic vehicular transmission, having a fluid gear provided with input and output members; a direct-coupling mechanism capable of connecting the input and output members of the fluid gear mechanically and directly by a locking force which is determined on the basis of a function of a difference between a working pressure and an internal pressure in the fluid gear; and a control valves provided between a pressure supply source and the direct-coupling mechanism and adapted to control the working pressure. The direct-coupling control system includes a pressure retainer valve for controlling the internal pressure in the fluid gear so as to reduce the same in accordance with an increase in a vehicle speed or an engine output.

Abstract: A combination range and master clutch assembly includes a separator plate, at least one clutch, a fluid actuated main piston for engaging each clutch, and at least one fluid actuated accelerator piston. The separator plate and main piston define first and second main chambers in communication with each other. The main piston and each accelerator piston define an accelerator chamber. Sliding of each accelerator piston blocks communication between the main chambers. The assembly is controlled by providing fluid at an operating pressure which may be modulated between low and high pressures. Fluid is selectively delivered to an accelerator chamber at the operating pressure when it is below a threshold pressure level, and to both the accelerator chamber and its associated main chamber at the operating pressure when it is above the threshold pressure level.

Abstract: In a motor vehicle equipped with a countershaft manual transmission for producing various ratios of the speed of an engine that is clutched to the transmission and the speed of a transmission output shaft, a system for maintaining the clutch disengaged while the transmission shift lever is in the neutral position and the clutch pedal is released includes a hydraulic damper actuated by a clutch pedal arm that moves a piston within a master cylinder connected hydraulically through an interrupter valve to a slave cylinder, which is connected mechanically to a clutch arm whose movement engages and disengages the clutch. An electrical circuit includes an ignition switch in series with a neutral switch and with a clutch switch, an interrupter valve coil in series with the switches and a clutch switch relay in parallel with the clutch switch. When the electrical circuit is closed, the interrupter valve closes hydraulic communication between the master cylinder and the slave cylinder.

Abstract: Fluid systems having modulating pressure relief valves ar normally needed in systems having clutches that require smooth engagement. It is also necessary in many systems to keep the sizes of components small to fit all of the necessary elements into a small area while simultaneously keeping the controls simple in construction for ease of manufacturing. The present modulating relief valve includes a housing having a dump valve, a load piston, and a relief valve spool concentrically disposed in the housing and adapted to control the rate of pressure rise of a fluid to a clutch and to further control the fluid flow to a torque converter while maintaining the system at a maximum pressure level. The load piston is operatively associated in a fluid flow controlling relation with each of the dump valve and the relief valve spool to control the flow of fluid to the torque converter and to simultaneously control the rate of pressure rise of the fluid in the clutch as well as limit the maximum system pressure.

Abstract: A vehicular clutch apparatus including a clutch unit disposed between an engine output shaft and a transmission, the clutch unit having driving clutch plates and driven clutch plates interleaved with the driving plates and a piston movable upon receipt of hydraulic pressure from a pressure source to press those plates into engagement, wherein in the hydraulic flow path leading from the hydraulic pressure source to the piston is disposed a directional control valve which is interlocked with a clutch lever and for cutting off the communication between the piston and pressure source and release the hydraulic pressure fed to the piston to the atmosphere. A valve is further disposed in the flow path to automatically release the hydraulic pressure in the path to the atmosphere in response to gear shift operation, thereby disengaging the clutch unit.

Abstract: Fluid systems having modulating pressure relief valves are normally needed in systems having clutches that require smooth engagement. It is also desired in many systems to maintain a difference in pressure levels between the fluid in different clutches, such as, speed and directional clutches during initial engagement in order to ensure that only one of the clutches absorbs the initial load. In order to reduce power losses and improve system efficiency, it is desirable to reduce the pressure level of the higher clutch once the clutches are fully engaged. The present modulating pressure relief valve assembly provides a valve device that is effective to limit the maximum pressure in the system and change the pressure difference between the clutches upon full engagement thereof. The valve device is located in a single bore thus reducing total valve size and manufacturing costs.

Abstract: A hydraulic circuit is disclosed for activating a clutch as well as a throttle valve which is used in the circuit. The hydraulic circuit includes a hydraulic actuator which is connected to a source of pressurized fluid to alternatively activate the clutch. Connected between the source of pressurized fluid in the actuator is a control valve and a pressure-responsive throttle valve. The control valve is basically an on/off valve which controls the flow of fluid to the clutch actuator or from the clutch actuator to a reservoir. The throttle valve, on the other hand, is arranged in series with the control valve and is responsive to fluid pressure on its downstream side to cause increased throttling of the fluid as the fluid pressure to the actuator increases. Such a circuit is beneficial in preventing the clutch from snatching as it is being engaged.

Abstract: A hydraulic pressure modulation device disposed between a hydraulic pressure source and a selector valve comprising a cylinder; a spool fitted into the cylinder; an accumulator; an actuation chamber formed in the cylinder; a passage openly connecting the chamber to the selector valve; a spring forcing the spool against a pressure in the chamber; a first passage openly connecting the pressure source to the selector valve; a second passage operable to introduce the oil from the pressure source into the accumulator while the outlet pressure of the device increases from a first value to a second value; and a third passage operable to connect the accumulator to an oil tank substantially after the second passage is closed, the passages being formed in the cylinder and the spool.

Abstract: An electrical solenoid operates a three-way valve having a vent port, a port connected to a source of high pressure hydraulic fluid and a port connection to a pilot valve. A check valve supplied from a source of low pressure hydraulic fluid is connected to the cylinder of a clutch or servo of an automatic transmission when a pilot valve opens this communication upon energizing the solenoid coil. The clutch cylinder is depressurized through the pilot valve to the vent port of the solenoid-operated valve.

Abstract: A remotely controlled automotive transmission shifting mechanism for effecting engagement of the respective gears with a force that varies in accordance with the gear selected. Pneumatic pressure from a compressed air storage tank is connected via a choke to a pneumatic actuating cylinder that effects gear engagement. A signal corresponding to the instantaneous pressure effective at the actuating cylinder is compared in an evaluating circuit with a reference value assigned to the gear selected. When the compared signals match, a solenoid valve is actuated to cut off further pressurization of the actuating cylinder and thereby modulate the gear actuating force in accordance with the gear selected. Following gear engagement, the gear actuating pressure is released.

Abstract: A single accumulator is operatively connected to a fluid operated clutch so as to retard a rise in fluid pressure supplied to the fluid operated clutch which is to be engaged during a downshift from the highest speed ratio to any one of the lower speed ratios and when the transmission shifts from a neutral to a forward drive.

Abstract: A rear wheel drive vehicle is converted to a four-wheel drive vehicle by operation of a hydraulically operated clutch which is controlled by a hydraulic valve. The hydraulic valve is spring biased to a clutch disengaged position and is hydraulically actuated to its clutch engaged position through operation of a pilot valve circuit which includes an electrically operated solenoid valve. The pilot valve circuit includes a flow restrictor providing modulated flow thereby affording a controlled pressure rise in the clutch whereby a smooth engagement of the front wheel drive is achieved.

Abstract: A bypass drive line (27) for a torque converter type automatic transmission (11) in which the bypass drive line includes a viscous coupling (30). The viscous coupling is of a sandwich construction including an annular body member (32) formed of aluminum, an annular cover member (34) of steel secured at its outer periphery (34a) to the outer peripheral portion (32a) of the body member and radially inwardly thereof spaced axially from the body member to define a viscous fluid chamber therebetween, and an annular clutch member (36a) disposed in the chamber and having a central hub portion (36e) adapted to be drivingly connected to the output shaft (16) of the torque converter. Confronting portions (36e, 32f) and (36c, 36d) of the body and clutch members define closely spaced working area, for viscously transmitting force from the body member to the clutch member.

Abstract: A control mechanism of a power shift transmission is disclosed and arranged in oil passages between the hydraulic pressure source and a hydraulic clutch, comprising an inching valve disposed in an upstream passage of said passages; a selector valve disposed in a downstream passage of said passages; a sequence valve of which an operation chamber is connected to a portion between the selector valve and the hydraulic clutch; and a modulator valve having a modulation chamber connected to a portion between the pressure source and the selector valve. The sequence valve is provided with a spool operable to move in accordance with a pressure in the operation chamber and to alternatively connect a booster chamber in the modulator valve to the inching valve and an upstream portion to the inching valve, so that a hydraulic pressure is always supplied into the booster chamber while the selector valve introduces the pressure into the clutch and the inching valve is operated.

Abstract: A drive shaft is connected with one coupling half of a synchronizing tooth clutch and with a primary part of a fluid coupling. A driven shaft is connected with another clutch half of the tooth clutch and with a secondary part of the fluid coupling. The tooth clutch has a clutch star which is axially displaceably guided by a first straight tooth system at the one clutch half by continuous tooth mesh and can be engageable with a second straight tooth system provided at the second clutch half. Threadably connected with the second clutch half a is also connected by a ratchet with the clutch star and is conjointly axially displaceable therewith. The ratchet engages and causes a screw-like relative movement of the screw socket in relation to the second clutch half causing of the clutch star to engage, when the rotational speed of the first clutch half, in normal forward rotation, is about to fall below the rotational speed of the second clutch half.

Abstract: A hydraulic circuit is disclosed for activating a clutch as well as a throttle valve which is used in the circuit. The hydraulic circuit includes a hydraulic actuator which is connected to a source of pressurized fluid to alternatively activate the clutch. Connected between the source of pressurized fluid in the actuator is a control valve and a pressure-responsive throttle valve. The control valve is basically an on/off valve which controls the flow of fluid to the clutch actuator or from the clutch actuator to a reservoir. The throttle valve, on the other hand, is arranged in series with the control valve and is responsive to fluid pressure on its downstream side to cause increased throttling of the fluid as the fluid pressure to the actuator increases. Such a circuit is beneficial in preventing the clutch from snatching as it is being engaged.