Abstract: Eight forward speeds and one reverse speed of an automatic transmission are achieved by: controlling a first clutch by a first pressure control valve controlled a first proportional control solenoid valve and a first pressure switching valve; controlling a second clutch by a second pressure control valve controlled by a second proportional control solenoid valve and a second pressure switching valve; controlling a third clutch by a third pressure control valve controlled by a third proportional control solenoid valve and a third pressure switching valve; controlling a first brake by first and second switching valves and a fourth pressure control valve controlled by a fourth proportional control solenoid valve and a fourth pressure switching valve; and controlling a second brake by a fifth pressure control valve controlled by a fifth proportional control solenoid valve and a fifth pressure switching valve.

Abstract: In a hydraulic control apparatus for a vehicular automatic transmission, if it is determined that there is a failure that may cause tie-up in an automatic transmission, communication is provided between a first output port and a first drain port in a switching valve. As a result, a hydraulic frictional engagement device, which should be disengaged when there is a failure, is disengaged. Also, a specific shift speed is achieved by controlling the switching valve. Therefore, it is not necessary to select a shift speed that is achieved on the condition that the hydraulic frictional engagement device, which should be disengaged when there is a failure, is engaged. Thus, it is possible to prevent a shift that may impair driveability when there is a failure that may cause tie-up in the automatic transmission.

Abstract: A cost for manufacturing an automatic transmission can be reduced since a separate solenoid valve for controlling a damper clutch is not required when a hydraulic control system of an automatic transmission for a vehicle includes: a regulator valve that forms a line pressure by regulating a hydraulic pressure generated by a hydraulic pump; a torque converter control valve that receives a hydraulic pressure from the regulator valve and supplies a torque converter operating pressure to a torque converter; and a damper clutch control valve that receives the hydraulic pressure of the torque converter control valve and selectively supplies the torque converter operating pressure and a damper clutch operating pressure, wherein the damper clutch control valve is controlled by a control pressure supplied from a switch valve that is controlled an operating pressure of an overdrive clutch that operates at third and fourth forward speeds.

Abstract: A pressure control system of an automatic transmission includes a control-pressure regulating valve, a path switching valve, and a coupling-pressure regulating valve. The path switching valve selectively outputs a control pressure or a line pressure, so that the coupling-pressure regulating valve regulates a coupling pressure based on the control pressure during gear shifting, and regulates the coupling pressure based on the line pressure after completion of the gear shifting.

Abstract: A hydraulic control apparatus for an automatic transmission includes a forward travel engaging element, a reverse travel engaging element, a first signal electromagnetic valve, a first switching valve, and a second switching valve. The hydraulic control apparatus is structured so as to change the output state of the signal pressure of the first signal electromagnetic valve when changing from the reverse travel shift position and/or shift range to the non-travel shift position and/or shift range and when changing from the forward travel shift position and/or shift range to the non-travel shift position and/or shift range, and to enable quick draining of hydraulic pressure of the hydraulic servo of the reverse travel engaging element and hydraulic pressure of the hydraulic servo of the forward travel engaging element.

Abstract: A calibration system for calibrating a transmission adjusts a clutch fill pulse width and hold level current for an oncoming clutch via calibration shifts during operation of the associated machine, thus establishing the desired shift timing and duration. The pulse width is calibrated based on torque transfer characteristics of the clutch during a test shift, and the hold level current is calibrated based on the shift duration of a further test shift.

Abstract: Assembly of multiple individual fluid pressure control solenoid valves and an individual fluid temperature sensor so packaged relative to a respective one of the individual solenoid valves as to permit direct or indirect fluid temperature measurement at individual solenoid valves. The assembly can include a lead-frame support (e.g. a printed circuit board) having multiple individual fluid pressure control solenoid valves and an individual transmission oil temperature sensor disposed on the lead-frame support in an oil passage that communicates to an output flow port of a respective one of the individual solenoid valves to provide transmission oil temperature information to a transmission electronic control unit, wherein the transmission electronic control unit provides command signals to the individual solenoid valves in response to the individual transmission oil temperature input signals associated with an individual solenoid valve to achieve more accurate pressure control.

Abstract: A hydraulic control system of a six-speed automatic transmission provides an enhanced overall performance by achieving precise and effective control by providing a fail-safe function in at least two ways.

Abstract: Each control portion for controlling each friction element includes a switch valve and pressure control valve such that hydraulic pressure supplied to the friction element is fully controlled, and a control portion for controlling a friction element that is operated both at low and high speeds includes a switch valve that senses an operation of a friction member cooperatively with the friction element at the high speed such that the friction member receives different hydraulic pressure at low and high speeds. A plurality of fail-safe valves is included for enhancement of a fail-safe function of an automatic transmission.

Abstract: The oil supply device for a change-under-load transmission having a high-pressure circuit and a low-pressure circuit is designed in such a manner that the high-pressure feed line to the consumer devices of the transmission system incorporates an inlet aperture of small size, the low-pressure feed line is connected between the inlet aperture and the consumer device, and the low-pressure feed line can be cut off from the high-pressure feed line by a one-way valve.

Abstract: An oil pressure control device has bypass drain oil passages that bypass a control valve and that are capable of draining the engaging pressure K from a hydraulic servo of a clutch when releasing the clutch. A drain-prohibiting check ball blocks a drain path between a manual valve and an input port.

Abstract: An electrohydraulic transmission control apparatus (10) that produces, controls and directs hydraulic pressure inputs to the clutches, brakes and shift mechanisms of an automatic transmission to shift the transmission. A module body (14) supports control apparatus components and is removably mountable to a transmission housing (16) of the transmission. The module body (14) defines a plurality of fluid conduits (28). A plurality of control valves (26) is disposed on the module body (14) and meter hydraulic fluid through the conduits (28) to brake and clutch hydraulic cylinders and shift mechanisms in the transmission. A plurality of solenoid-operated control valves (26) is also disposed on the module body. A controller (34) disposed on the module body is connected to the solenoids (30) and controls the valves by operating the solenoids (30) in accordance with inputs received from sensors (36-44) that detect various factors representing the running state of the transmission and the vehicle it's mounted in.

Abstract: A hydraulic control system for an automotive automatic transmissions includes a pressure regulator for regulating hydraulic pressure, a pressure reducer having a reducing valve for reducing hydraulic pressure, a shift controller having a manual valve cooperating with a shift selector lever and connected to a plurality of range pressure lines, a pressure controller comprising first, second and third solenoid valves for controlling control pressure reduced by the reducing valve, and first, second and third pressure control valves for controlling hydraulic pressure supplied from the manual valve, the first, second and third pressure control valves being independently controlled by control pressure supplied from the first, second and third solenoid valves, respectively, a switching controller comprising a first switch valve for supplying hydraulic pressure from the first pressure control valve to one of first and second switching lines and a second switch valve for supplying hydraulic pressure from the third pres

Abstract: An automatic transmission comprises a forward/reverse selection hydraulic servomechanism 70 which actuates a dog clutch and a plurality of clutches 11, 12, 13, 14 and 15. For this automatic transmission, a control system comprises first˜fifth on/off solenoid valves 81˜85 and first˜third linear solenoid valves 86˜88. These valves are used to control the supply and drain of a line pressure to and from the forward/reverse selection hydraulic servomechanism 70 and first˜fifth shift valves 60, 62, 64, 66 and 68 so as to control the actuation thereof for the selective engagement of the clutches. This system, when it detects, by a hydraulic switch 93, a condition that the D range is selected and that the actuation command signals being sent to the solenoid valves correspond to one of the signal combinations which are used for setting the driving modes of the D range, allows the actuation of the solenoid valves by these actuation command signals.

Abstract: A power transmission includes a plurality of torque transmitting mechanisms controlled by an electro-hydraulic control system to provide a reverse drive ratio, a neutral condition and a plurality of forward drive ratios. The electro-hydraulic control has three shift valves, two variable pressure control valves, and a manual control valve. Each of the shift valves have a hydraulically on position, established by a respective solenoid valve, and a hydraulically off position, established by a spring. The manual control valve is moveable to a neutral condition, a reverse drive condition and a forward drive condition. In each of the positions during a neutral to reverse, neutral to forward, or forward/reverse interchange, the shift valves are conditioned to be hydraulically on thereby permitting the manual control valve to be the controlling valve member for completing the interchange.

Abstract: A valve body for use in an automatic overdrive transmission where the hydraulic fluid passages are blocked in selected locations in the body. The blockages result in increased pressure in the free passages and redirection of fluid flow such that the reverse clutch assembly is operable in third gear. By this procedure, the torque capacity of the transmission is increased.

Abstract: A method for controlling the fill time of an oncoming transmission clutch of a vehicle within a predetermined range of speed conditions is disclosed, the method including the steps of: (a) sensing an engine speed within the predetermined range; (b) reading an incremental pulse time value corresponding to the speed sensed in step (a); and (c) determining an adjusted pulse time value using the incremental pulse value read in step (b) and a predetermined nominal pulse time value.

Abstract: A hydraulic control system includes a pressure regulator for controlling hydraulic pressure generated by an oil pump, the pressure regulator being realized through a pressure regulator valve; a pressure reducer realized through a reducing valve for maintaining pressure at a level lower than line pressure; a damper clutch controller for operating a damper clutch of a torque converter; a shift controller for forming shift modes, the shift controller being realized through a manual valve indexed with a select lever operated by a user; a hydraulic pressure controller for providing shift quality and shift responsiveness to enable smooth shifting; and a hydraulic pressure distributor for supplying suitable hydraulic pressures to first, second, third, fourth and fifth friction elements operating as input and reaction elements in each shift stage, the hydraulic pressure distributor being realized through a plurality of spool valves.

Abstract: The present invention is directed to methods and systems for improving the operation of transmissions for automotive vehicles, and in particular, the "factory installed" automotive transmission as installed by an original automobile manufacturer. The methods and systems of the present modify both the structural components and hydraulic circuitry of original transmissions to adjust applied pressure and shifting patterns to enhance the operation of the modified transmissions.

Abstract: An oil pressure supply path to a transmission is changed over using a spool valve comprising a spool which displaces in conjunction with a selector lever of the transmission. The displacement of the spool is detected by an inhibitor switch. By supporting the inhibitor switch directly by the spool valve, the spool displacement position and inhibitor switch output signal always precisely correspond. Therefore, it is unnecessary to adjust the relative position of the spool valve and inhibitor switch unlike the case where these members are supported separately in the transmission.

Abstract: In an automotive transmission, a method for determining whether an upshift should be enabled or disabled determines the predetermined upshift vehicle speed at which the upshift is scheduled to occur with reference to current throttle position and vehicle speed. The method employs the difference between upshift vehicle speed and current vehicle speed, the current vehicle acceleration, an empirically determined upshift vehicle acceleration referenced to current vehicle speed and the speed difference. If the current vehicle acceleration is equal to or greater than upshift vehicle acceleration, the upshift is enabled; otherwise, the scheduled upshift is disabled.

Abstract: A hydraulic control system for an automatic transmission includes a pressure regulator for regulating hydraulic pressure produced in an oil pump, and a plurality of valves selectively supplying the regulated hydraulic pressure to a first number of friction elements. A second number of solenoid valves controls operation of the first number of friction elements by controlling supply of the regulated hydraulic pressure to the plurality of valves; wherein the second number is less than the first number. A manual valve controls supply of the regulated pressure to the second number of solenoid valves.

Abstract: An electrohydraulic control device for power shift gearboxes, in particular in construction machinery, has switching elements (SE1, SE2, SE3) which can be actuated by a system pressure from an external pressurized medium source (1). Shift valves (SV1, SV2, SV3) are provided between the pressurized medium source (1) and the switching elements (SE1, SE2, SE3) and can each be actuated by pilot pressure. Each of the switching elements (SE1, SE2, SE3) can be actuated in a defined switching state by at least two actuated shift valves (SV1, SV2, SV3) and at least one non-actuated shift valve.

Abstract: A hydraulic control system for an automatic transmission including a plurality of friction elements associated with respective transmission speeds. The hydraulic control system includes a hydraulic fluid source, a line pressure controller, a reducing pressure controller, a range controller, a shift controller, a hydraulic pressure controller, wherein the hydraulic pressure distributor includes a 3-4 shift valve, a 2-3/4-3 shift valve, a 1-2 shift valve, a control switch valve for selectively supplying/exhausting hydraulic pressure from the shift controller to at least one of the friction elements corresponding to the respective transmission speeds to control operating timing of each corresponding friction element and supplying the hydraulic pressure from the shift controller to the line pressure controller to reduce line pressure at a high speed state; and a solenoid valve for controlling the control switch valve in accordance with a control signal of the transmission control unit.

Abstract: A shift control system of an automatic transmission sets a predetermined gear stage by applying a first frictional engagement element and releasing a second frictional engagement element. A pressure regulating mechanism regulates an oil pressure to be fed to or drained from the first frictional engagement element. A failure detector detects a failure of an apparatus to participate in the regulation and control of the oil pressure which is to be fed to or drained from at least one of the first and second frictional engagement elements. A gear stage inhibitor inhibits the setting of the predetermined gear stage if the failure is detected by the failure detector.

Abstract: A hydraulic control system for automatic transmission, which has a plurality of friction elements for selectively transmitting rotational force of a torque convertor to gear elements therein, controls engagement of the plurality of friction elements in proportion to forward and reverse speeds by operation of a plurality of valves for regulating, controlling and distributing hydraulic fluid supplied by an oil pump. The hydraulic control system includes a manual valve moving based on operation of a shift select lever by a user to select an operation range. The manual valve controls the supply of hydraulic fluid to at least one of the plurality of valves such that the hydraulic fluid generated by the oil pump is used as lubricating fluid for the torque convertor when the shift select lever is in a park operation range.

Abstract: Disclosed is a hydraulic control system for automatic transmissions including a plurality of friction elements, comprising a hydraulic pressure source; hydraulic pressure regulating parts for controlling hydraulic pressure from the hydraulic pressure source; damper clutch control parts for actuating a damper clutch of the torque converter by supplying hydraulic pressure fed from the pressure regulating parts to the torque converter; shift control parts for selecting a shift mode by converting hydraulic pressure from the pressure regulating parts into drive pressure; hydraulic pressure control parts for controlling the drive pressure from the shift control parts; and hydraulic pressure distributing parts for suitably distributing hydraulic pressure from the hydraulic pressure control parts to each friction element, said hydraulic pressure distributing parts comprising a 1-2 shift valve; a 2-3/4-3 shift valve; and shift timing control parts having a shift timing control valve for supplying hydraulic pressure to

Abstract: A hydraulic control system for an automatic transmission includes a hydraulic pressure source, a line pressure controller for constantly controlling hydraulic pressure from the hydraulic pressure source, a reducing pressure controller for generating reduced pressure, a damper clutch controller for supplying hydraulic pressure fed from the line pressure controller to a torque converter, a shift controller for converting hydraulic pressure from the line pressure controller into drive pressure corresponding to each speed stage, a hydraulic controller for controlling drive pressure from the shift controller; and a pressure distributer for distributing hydraulic pressure from the hydraulic controller to each friction member for each speed stage by being controlled by drive pressure from the shift controller.

Abstract: In an automatic transmission including a gear unit with a second brake connected in series with a one-way clutch and a first brake that is not connected with a one-way clutch, the second brake and the first brake are controlled by linear solenoid valves individually. A vehicle load is detected, and when the vehicle is in a high load state, at first the second brake performs an engagement control, then after input rotation to the gear unit is synchronized with output rotation of the gear unit, the first brake performs an engagement control. When the vehicle is in a low load state, at first the first brake performs an engagement control, then after input rotation to the gear unit is synchronized with output rotation of the gear unit, the second brake performs an engagement control.

Abstract: The hydraulic control system for an automatic transmission having a plurality of friction elements includes a pressure regulator which regulates hydraulic pressure produced by an oil pump, a plurality of valves selectively supplying hydraulic pressure to the plurality of friction elements, and a pressure controller controlling and selectively supplying hydraulic pressure to a plurality of pressure control lines operationally connected to the plurality of valves and at least one of the plurality of valves. The plurality of valves include a first valve operationally controlled by hydraulic pressure in a first one of the pressure control lines to pass the hydraulic pressure output by the pressure controller to at least one of the plurality of friction elements in each operational range except a first speed stage of a drive range.

Abstract: Disclosed is a hydraulic control system.

Abstract: A control system of an automatic transmission includes a torque converter, a lock-up clutch for directly connecting input and output members of the torque converter, a pressure control valve which changes a hydraulic pressure to control an engaging force of the lock-up clutch, and a pressure regulator, disposed in an engaging passage, which supplies hydraulic pressure to engage a frictional element. The pressure regulator adjusts a primary pressure and produces an output hydraulic pressure corresponding to a control pressure introduced into a control port of the pressure regulator. A control pressure supply device is provided for introducing the control pressure, controlled by the pressure control valve, into the control port of the pressure regulator. The number of parts can be reduced without producing any inconvenience.

Abstract: A manual shift control device of a transmission control system for an automotive automatic transmission. A solenoid feed valve feeds line pressure passing through a pressure regulator valve to first, second and third solenoid valves. A torque control regulator valve changes drive pressure into torque pressure. A control switch valve alternatively feeds torque pressure to first and second torque pressure passages. An N-D control valve sequentially feeds torque pressure and drive pressure to a second friction member, which is applied at an initial shift operation together with a first friction member, to thereby alleviate shift shock from neutral range "N" to drive range "D". A first-to-second speed shift valve feeds part of the torque pressure and part of the drive pressure to a third friction member during a shift operation from the first speed to the second speed.

Abstract: A control system for an automatic transmission having friction coupling elements, at least one of which is locked in 3rd and 4th gears and unlocked in 1st and 2nd gears, includes a first shift valve shiftable between 3rd and 4th gears, and second shift valve shiftable between in 2nd gear and 1st gear in which engine brake available, and a solenoid valve providing control pressure which is selectively directed to these shift valves and cause them to shift so as to lock or unlock the friction coupling elements.

Abstract: A rotary switch, used to select the operating range of an automatic transmission, controls solenoid-operated valves corresponding to the selected range to open and close a connection between a range valve assembly and a control pressure source. A forward range selection electric circuit includes a forward range high side driver, a solenoid-operated control valve, the rotary switch, a power source, and a current monitor. There is a similar circuit for the reverse range. A forward range valve and reverse range valve respond to control pressure produced by the circuit to open a fluid pressure source to a line that is pressurized to produce forward drive, a second position opens a connection between the fluid pressure source and a line that is pressurized to produce reverse drive and vents those lines to sump.

Abstract: A power transmission control selectively establishes five forward speeds and one reverse speed by the controlling of three relay valves and two variable pressure TRIM valves. The TRIM valves normally control the pressure in the on-coming and off-going friction devices, respectively. The TRIM valves switch functions between ranges. In the fifth speed, the relay valves provide a pathway or passage for directing the fluid output of one of the TRIM valves to a control area on a system regulator valve to effect a variable main pressure.

Abstract: A hydraulic control system of an automatic transmission for a vehicle comprises a pressure regulator means changing hydraulic pressure supplied from an oil pump, a torque pressure changing/supplying device changing line pressure supplied from the pressure regulator into a torque pressure and supplying it, a shift controller supplying the hydraulic pressure through a drive pressure line in D range and through a rear pressure line in R range, a hydraulic pressure distributing device selecting and supplying the hydraulic pressure supplied from the shift controller by the control of the solenoid valves to the first, second, third, fourth, fifth, sixth, seventh friction members, and a plurality of accumulators disposed on the first, fourth, and seventh friction members.

Abstract: Methods and systems for improving the operation of a transmission for an automotive vehicle, and in particular the transmission as installed by the original automobile manufacturer, modify the original hydraulic fluid circuits of the automotive transmission installed by the automobile manufacturer to enable the "factory installed" transmission to hold first gear in the first gear selector position through any rotational speed of the engine. Further modifications to the hydraulic circuitry enable the operator of the vehicle to select fourth gear manually at relatively high vehicle speeds at wide open throttle conditions. Additional modifications to the hydraulic circuitry increase the third clutch capacity at high throttle during a "2-3" shift, and result in firm and more correctly timed shifts.

Abstract: A hydraulic control system for automatic transmission systems includes: an oil pump, a pressure control valve, a solenoid supply valve, a manual valve, a torque control regulator valve, a control switch valve, an N-D control valve, a 1st-2nd speed shift valve, a 2nd-3rd speed shift valve, a 3rd-4th speed shift valve, a second clutch valve, a third clutch valve, a fourth clutch valve, and an N-R control valve. Accumulators are provided to each supply line of first, second, third and sixth frictional elements to alleviate shock resulting from gear shifting and maintain stability in actuating hydraulic pressure.

Abstract: A hydraulic control system for an automatic transmission includes a hydraulic pump, a pressure regulating valve, a solenoid supply valve, a manual valve, a torque control regulator valve, a control switching valve, a N-D control valve, a 1-2 shift valve, a 2-3 shift valve, a 3-4 shift valve, and a N-R control valve. Accumulators are disposed in conduits to first and seventh friction members for reducing shift shock caused by line pressure and drive pressure fed from fourth and second clutch valves.

Abstract: A hydraulic control system for an automatic transmission of an automotive vehicle is provided which has a fail-safe function of preventing unsafe operation of the automatic transmission if a failure occurs in any of solenoid valves which control engagement operations of frictional elements such as clutches and brakes of the transmission. The hydraulic control system includes a hydraulic pressure flow control unit which controls hydraulic pressure flow between at least one of the frictional elements and at least one of the solenoid valves to allow the hydraulic pressure to be supplied to a predetermined combination of the frictional elements to achieve the power transmission at one of given gear ratios. The hydraulic pressure flow control unit restricts the hydraulic pressure flow to an inoperative combination of the frictional elements which provides no power transmission. With these arrangements, the power transmission is established if any of the solenoid valves malfunctions to allow the vehicle to travel.

Abstract: In a hydraulic control system for automatic transmissions of a vehicle, drive pressure is fed to a first friction member at the first, second and third speeds of a "D" range, drive pressure is fed to a third friction member at a fourth speed, a 2-4/3-4 shift valve for exhausting pressure from the first friction member at third-to-fourth and second-to-fourth speed shifting is connected to an end clutch valve to allow pressure from a first pressure control valve to be fed to the third friction member at the fourth speed, and exhausting of pressure from a releasing conduit of a second friction member and the third friction member via an exhaust conduit connecting the 2-4/3-4 shift valve and a 2-3/4-3 shift valve during fourth-to-second, fourth-to-first and third-to-second speed shifting is delayed by an orifice.

Abstract: A shift control system of an automatic transmission for setting a predetermined gear stage by applying first frictional engagement means and releasing second frictional engagement means, comprising: a pressure regulating mechanism for regulating an oil pressure to be fed to or drained from the first frictional engagement means; a failure detector for detecting a failure of an apparatus to participate in the regulation and control of the oil pressure which is to be fed to or drained from at least one of the first and second frictional engagement means: and a gear stage inhibitor for inhibiting the setting of the predetermined gear stage if the failure is detected by the failure detector.

Abstract: If there is a need to accelerate abruptly, or shift a speed stage from a fourth speed stage to a second speed stage, to accomplish a skip shift from the fourth speed stage to the second speed stage without going via a third speed stage and, therefore, enhance the shift-responsiveness and the power performance, a high-low pressure valve which is connected to a fourth friction pressure line in the third and fourth speed stages is duty controlled by a damper clutch solenoid valve to vary a line pressure in a pressure regulating valve with the operation of a damper clutch, and a shift valve is controlled to a drive pressure passage and a third speed line pressure by controlling a first and second pressure control solenoid valves to enable the skip shift, and by supplying a first friction element with the operation pressure at times of the second to the third speed stage shifting, after the shifting to the third speed stage, when the operation pressure for the fourth friction element is supplied to a releasing val

Abstract: Disclosed is a hydraulic control system of an automatic transmission used in a vehicle, which comprises a torque converter for transferring the engine power to the input shaft of the transmission, an oil pump for pumping an oil by means of the engine power, a pressure regulation means for regulating the line pressure produced by the oil pump according to the forward and reverse drive and the amount of a throttle opening, a damper clutch working control means for changing the direction of the pressure delivered to the torque converter in order to increase the power transfer rate of the torque converter, a shift pressure control means for delivering the pressure supplied from the pressure regulation means to the first, second, third, fourth, fifth, sixth and seventh solenoid valves controlled on/off by a transmission control unit to adjust the control pressure during shifting operation, and a pressure distribution means for selectively distributing the pressure supplied from the pressure control means during sh

Abstract: Disclosed is a hydraulic control system of an automatic transmission used in a vehicle, which includes an oil pump, a manual valve for selecting one of the parts of a hydraulic pressure line to deliver the hydraulic pressure produced by the oil pump according to the vehicle speed range, a first to a fourth pressure control valve with a first port to receive the pressure supplied by the manual valve in a forward drive range, a first to a fourth solenoid valve for respectively controlling the pressure control valves according to a vehicle speed, a rear clutch valve for receiving a hydraulic pressure from the pressure control valves, a low/reverse valve, a fail-safe valve, and a high-low pressure valve for receiving a hydraulic pressure from the fourth pressure control valve to vary the line pressure.

Abstract: A hydraulic control system of an automatic transmission for an automotive vehicle which may simplify a structure, minimize a shift shock for improving a shift responsiveness, and improve shift quality even in a driven state by a manual range shift and a power off state.

Abstract: A hydraulic control system of an automatic transmission, which includes a line pressure regulator for regulating the hydraulic pressure supplied from an oil pump to the hydraulic control line, and a shift structure for selectively delivering the regulated hydraulic pressure to the friction elements, wherein the shift structure further comprises a manual valve operatively linked with a shift lever for delivering the regulated hydraulic pressure according to shift ranges, a plurality of solenoid valves controlled on/off by a transmission control unit to control the friction elements, a first to a fifth pressure control valves for simultaneously controlling both releasing and connecting end of the friction elements, a first-to-second shift valve for making a port change by the hydraulic pressure flowing out from the pressure control valves to deliver the pressure to the friction elements, a forward drive clutch release valve, a second-to-third shift valve, and a reverse drive clutch valve.

Abstract: Power transmissions incorporate gear ratios including a plurality of forward ratios, a neutral condition and at least one reverse ratio. The establishment of each ratio is controlled by selectively engageable hydraulically operated friction devices, such as clutches and brakes. The interchange between forward ratios is controlled by the interchange of at least one friction device. The control elements to accomplish the establishment and interchange of the ratios include a pressure source, shift valve, solenoid control valves and pressure control valves. The solenoid valves are electrically actuated and the hydraulic portion of the control includes elements that permit continued operation of the transmission in selected ratios in the event of electrical discontinuance.

Abstract: A hydraulic pressure control system for an automatic transmission that includes a torque control regulating valve for converting a portion of the hydraulic pressure from an oil pump to a control pressure in accordance with a variation in the torque, and a control switch valve for supplying a torque pressure to a friction member prior to a shift valve being supplied with supply and release pressures for a friction member.