Abstract: A control system for a continuously variable automatic transmission for an automotive vehicle, includes a throttle opening sensor that detects a throttle opening, and a controller that executes a change-speed control in a normal mode in which a desired transmission input speed is determined based on operating conditions of the vehicle and a desired transmission ratio is determined based on the desired transmission input speed when the throttle opening is less than a first value, and that executes the change-speed control in a linear mode in which the desired transmission ratio is fixed to a second value when the throttle opening is greater than or equal to the first value. The second value is set based on the desired transmission ratio used in the normal mode prior to switching to the linear mode.

Abstract: A control system for a continuously variable automatic transmission for an automotive vehicle, includes a throttle opening sensor that detects a throttle opening, and a controller that executes a change-speed control in a normal mode in which a desired transmission input speed is determined based on operating conditions of the vehicle and a desired transmission ratio is determined based on the desired transmission input speed when the throttle opening is less than a first value, and that executes the change-speed control in a linear mode in which the desired transmission ratio is fixed to a second value when the throttle opening is greater than or equal to the first value. The second value is set based on the desired transmission ratio used in the normal mode prior to switching to the linear mode.

Abstract: A shift control system for an automatic transmission is disclosed, which comprises, in the first embodiment for example, an orifice bypass valve including a spool, a spring and a pilot port. The spool is movable between an interrupting position where a first hydraulic passage is interrupted from a third hydraulic passage, and a connecting position where a first passage is connected with a third passage, and it is pressed to the interrupting position by the spring. The pilot port induces a force by which the spool is pressed in the direction opposite to a force of the spring when the hydraulic fluid is supplied, and it is connected with a fourth hydraulic passage for receiving the hydraulic fluid for operating an overrunning clutch.

Abstract: An automatic transaxle comprises a rotary motion transmitting unit which transmits a rotary motion between two parallel shafts including an input shaft in driving connection with a turbine of a hydrodynamic unit, i.e., a torque converter. The rotary motion transmitting unit includes a driver sprocket, a follower sprocket, and a chain in driving connection between the sprockets. The pump has a pump housing fixed to a stationary support plate. The driver and follower sprockets are rotatably supported at this stationary support plate. A reaction shaft in driving connection with an inner race of a one-way clutch of a stator of the torque converter extends through the stationary support plate and rotatably supports the driver sprocket. The reaction shaft is hollow to allow the input shaft to extend therethrough. The input shaft is drivingly connected with the driver sprocket.

Abstract: A transmission case has a wall portion defining an oil pressure chamber of a fluid operated friction device, and an end portion having a threaded hole receiving a bolt for fastening a side cover to the case. In order to make the wall portion impervious to oil notwithstanding defects formed by casting, the wall portion is separated from the end portion by a U-shaped groove. Furthermore, the end portion is shaped into an outward flange through which the threaded hole passes from one side to the other.

Abstract: An output shaft is supported by means of a ball bearing at one end, a radial needle bearing and a thrust bearing. The ball bearing is arranged for supporting the output shaft against most part of radial load. On the other hand, the trust bearing is arranged for supporting the output shaft against the thrusting force which is exerted on the output shaft while the engine driving torque is transferred therethrough. Such construction reduces radial and thrusting stress to be exerted on the needle bearing. Therefore, the radial needle bearing to be used in the shown construction is required substantially small load capacity and thus can be satisfactorily small for allowing the transaxle unit to be designed compact.

Abstract: In an automatic transaxle having an idler gear center axis below a line interconnecting a main power train center axis and a differential center axis, a control valve assembly is disposed on one of opposite sides of a transaxle case divided by the idler gear center axis. The differential is disposed on the other of the opposite sides of the transaxle. An oil storing chamber is disposed next to the control valve assembly and free from occupation by same. The oil storing chamber extends from one to the other of the opposite sides of the transaxle case.

Abstract: A shift control system for an automatic transmission is disclosed, which comprises, in the first embodiment for example, an orifice bypass valve including a spool, a spring and a pilot port. The spool is movable between an interrupting position where a first hydraulic passage is interrupted from a third hydraulic passage, and a connecting position where a first passage is connected with a third passage, and it is pressed to the interrupting position by the spring. The pilot port induces a force by which the spool is pressed in the direction opposite to a force of the spring when the hydraulic fluid is supplied, and it is connected with a fourth hydraulic passage for receiving the hydraulic fluid for operating an overrunning clutch.

Abstract: A shift valve which controls the shifting of the transmission between the top speed and the next lower one is arranged to have a port which is communicable with an overrunning clutch viz a relatively short conduit arrangement. The port is arranged to be constantly supplied with line pressure while the manual valve is set in any of the forward drive ranges, and to be communicated with the conduit when the shift valve is supplied with a top speed inhibit signal and induced to assume its downshift position.

Abstract: A one-way valve is arranged with an accumulator in a manner wherein the discharging of the accumulator is restricted. During upshifting, the stroking of a band brake servo in a release direction is induced before the charging stroke of the accumulator and the appropriate timing of the engagement of a high clutch and the disengagement of a band brake is induced. During downshifting, the pressure which is prevailing in the conduit interconnecting the two friction elements is allowed to drop rapidly during the initial stage of the shift due to the provision of the one-way orifice and allows the torque transmission capacity of the clutch to quickly reduce while inducing the stroking of the band brake servo in an engaging direction before the discharge stroke of the accumulator.

Abstract: A shift control system for an automatic transmission comprises a shift valve for an auxiliary gear train, an orifice bypass passage and an accumulator for low gear train. The shift valve includes a spool which is movable between a first position where the hydraulic fluid is supplied to a first passage and hydraulic fluid is discharged from a second passage, and a second position where the hydraulic fluid is supplied to the second passage and hydraulic fluid is discharged from the first passage. The orifice bypass valve includes a spool and a pilot port. The former is movable between an interrupting position where the first passage is interrupted from a third passage, and a connecting position where the first passage is connected to the third passage, and it is pressed to the interrupting position by a spring. The latter is connected with a fourth passage or engine brake passage.

Abstract: During D-RANGE operation under which a 4-2 downshift is required, a 4-2 downshift sequence valve is responsive to the pressure which is supplied to a friction element which is involved with the production of 3rd gear, and is maintained in a position wherein the 4th speed apply chamber of a band brake servo is maintained pressurized, until such time as the pressure in the 3rd speed friction element drops below a predetermined limit.When a manual valve is moved out of the D-RANGE position to one wherein engine braking is required, a control pressure is applied to the 4-2 sequence valve which immediately switches it to a position wherein it drains the 4th speed apply chamber irrespective of the 3rd speed pressure. At the same time an overrunning clutch control valve is supplied with the same control pressure and is moved to a position wherein an overrunning clutch is supplied with line pressure and engaged to enable engine braking.

Abstract: A shift control system for an automatic transmission comprises a shift valve for an auxiliary gear train and an accumulator for low gear train. The shift valve includes a spool which is movable between a first position where the hydraulic fluid is supplied to a first passage and hydraulic fluid is discharged from a second passage, and a second position where the hydraulic fluid is supplied to the second passage and hydraulic fluid is discharged from the first passage. The accumulator includes a working pressure chamber and a back pressure chamber which is connected with a third passage or engine brake passage.

Abstract: In an automatic transmission, a governor shaft is arranged so that a center axis of a governor shaft is interposed between a center axis of an idler shaft and a center axis of a final drive gear. In one embodiment, the center axis of the governor shaft is further disposed between a center axis of an output gear and the center axis of the final drive gear, and a governor valve is disposed above a drive shaft joint. In another embodiment, the governor valve is disposed below the drive shaft joint.

Abstract: In order to increase a torque transmission capacity of a lock-up clutch without any increase in the internal pressure of a torque converter, a lock-up clutch release circuit and a lock-up clutch engagement circuit share a primary relief valve, and the lock-up release circuit is further provided with a secondary relief valve disposed between a lock-up control valve and the torque converter. Thus, when the lock-up clutch engagement circuit is opened, the primary relief valve works to prevent the pressure of hydraulic fluid from increasing above a first predetermined value, whereas, when the lock-up clutch release circuit is opened, the secondary relief valve causes a drop in the hydraulic pressure and prevents the hydraulic pressure from increasing above a second predetermined value. The first predetermined value is higher than the second predtermined value.

Abstract: A second spool valve element which is engageable with the one which actually controls discharging of hydraulic fluid in a manner which controls the level of the line pressure, has first and second lands, the first and second lands defining a pressure differential area which can be exposed to a first control pressure indicative of the transmission being shifted out of D range into a lower one, in a manner to bias the second valve toward the first spool valve element; a chamber is defined in the valve bore to which the engageable ends of the first and second spools are exposed and which is supplied with a second control pressure indicative of the torque being applied to the tranmission, the second control pressure producing a bias which tends to move the the first and second spool valve elements apart.

Abstract: A hydraulic system for an automatic transmission comprises a governor valve generating a governor pressure, a throttle valve generating a throttle pressure, a throttle modifier valve generating a throttle modifier pressure which is an amplified pressure of the throttle pressure and thus higher than said throttle pressure, a throttle opening detecting valve generating a partial throttle pressure, and a shift valve. The shift valve has a spool subject to the governor pressure to be biased toward an up position thereof. The spool has a pressure acting area which is exposed to the throttle modifier pressure when the spool is in a down position thereof. This pressure acting area is exposed the partial throttle pressure when the spool is in the up position thereof.

Abstract: A throttle presure and a modified throttle pressure which is higher than the throttle pressure are developed and the spool of the 2-3 shift valve arranged to be biased toward its downshift position by the throttle pressure when in its upshift position and toward its downshift position by the modified throttle pressure when in its downshift position. The difference between the throttle pressure and the modified throttle pressure is arranged to increase as the level of the throttle pressure decreases.

Abstract: A single sequence valve is connected to a 3-4 shift valve thereby defining a drain circuit. The sequence valve is responsive to hydraulic pressures which act on a fourth speed apply chamber of a band brake and a high clutch, respectively. The sequence valve normally defines the drain circuit, but delivers hydraulic fluid to the 3-4 shift valve, then to the fourth speed apply chamber of the band brake after a command for a 4-2 downshift has taken place until the hydraulic pressure in the high clutch drops to a predetermined value.

Abstract: A planetary gearing for an automatic transmission comprises a main and auxiliary planetary gearings which are operatively coupled with each other. The auxiliary planetary gearing has a reduction drive state and a direct drive state and it shifts from the reduction drive state thereof to the direct drive state thereof when the main planetary gearing state has shifted up to the n-1 speed state thereof, where n is an integer not less than four. The main planetary gearing has n forward speeds.