Abstract: An accumulator which is pressurized during the engagement of the band brake, is arranged with a one-way valve so that the discharge therefrom, which accompanies the downshifting of an associated shift valve, temporarily maintains a pressure which is supplied to an overrunning clutch control valve and which holds the spool valve elements therein in a position wherein the overrunning clutch is drained.

Abstract: A system for controlling a lock-up clutch of a torque converter comprises a lock-up control valve, and a shuttle valve. The lock-up control valve includes a spool having a first and a second pressure acting areas. The shuttle valve delivers an output hydraulic pressure when at least one of two inlet ports is pressurized. One of the inlet ports is subject to a first hydraulic pressure which builds up at a band brake during operation with the fourth speed ratio, while the other inlet port is subject to a second hydraulic pressure which builds up at an overrun clutch during operation with the third, second, and first speed ratios when an engine brake operation range is selected. The output hydraulic pressure of the shuttle valve is transmitted to the lock-up control valve to act on the second pressure acting area. The first pressure acting area is subject to a third hydraulic pressure which builds up at a high clutch during operation with each of the third and fourth speed ratios.

Abstract: A low restrictor is provided in a hydraulic line having one end connected to a fourth speed servo apply chamber of a friction device, in the form of a band brake, and an opposite end connected to a 3-4 shift valve. An accumulator is connected to the hydraulic line at a first section between the flow restrictor and the friction device. A lock-up control valve is connected to the hydraulic line at a second section between the flow restrictor and the 3-4 shift valve. The lock-up control valve includes a spool movable to a first position where a lock-up clutch is released from a second position where the lock-up clutch is engaged in response to a drop in hydraulic pressure within the second section of the hydraulic line upon shifting from the fourth speed ratio to the third speed ratio. Since the transmission of this drop to the first section of the hydraulic line is delayed by the flow restrictor and the accumulator, the release of the friction device is delayed.

Abstract: An oil pump of an automatic transmission, which comprises a casing having an oil pump gear chamber formed therein, the casing having first and second bores exposed to the oil pump gear chamber, the first and second bores being coaxially spaced from each other with an interposal of the oil pump gear chamber therebetween; gears operatively disposed in the oil pump gear chamber of the casing; a first splined portion formed on a leading end portion of a stator shaft of a torque converter; and a second splined portion formed on an inner surface of the second bore, wherein the stator shaft is thrusted through the first and second bores in this order into a fixed position wherein the first and second splined portions are operatively engaged.

Abstract: A pressure regulating valve has a bore in which in a spool and an accumulator piston are disposed. A spring is disposed between the two elements and arranged to bias the spool in a first axial direction which tends to maximize the amount of hydraulic fluid which is supplied to a friction element. As the accumulator chamber defined by the accumulator piston fills, the spring is compressed increasing the bias on the spool.The spool defines a feedback chamber, the pressure in which which tends to bias the spool in a second axial direction which minimizes the supply of hydraulic fluid, and which features a chamber which is supplied directly with a pressure indicative of transmission torque. This chamber is arranged so that the pressure therein produces a bias which also acts in the first axial direction and so that no resistance to the stroking of the accumulator piston is produced.

Abstract: A hydraulic control system for an automatic transmission comprises a one-way valve arranged between a hydraulic line leading to a second speed apply chamber of a band brake and a hydraulic line leading to a fourth speed apply chamber of the band brake in such a manner as to allow fluid communication between them when a pressure dfferential takes place. The pressure differential takes place when the transmission upshifts from the first speed ratio to fourth speed ratio. Thus, during the 1-4 shift, a pressure build-up in the fourth speed apply chamber takes place in the same manner as a pressure build-up taking place in the second speed apply chamber under the control of a 1-2 accumulator valve.

Abstract: A spring is disposed between first and second reciprocal spool valve elements and arranged to bias the same apart when the level of throttle pressure falls to a low level. The first valve is arranged to control the communication between a source of line pressure and a friction element or elements and is subject to the effects of the governor pressure. The second of the spool valve elements is subject to the effect of throttle pressure and a second spring which biases the second element toward the first one.

Abstract: The stroking order of the band brake servo piston and the accumulator piston are reversed under high and low transmission loads, therefore reversing the pressure modifying effects provided by the same. This is achieved by selecting the various areas and springs which determined the resistance against which the piston must stroke under high and low load conditions (wherein the level of the line pressure changes), and the forces which drive the pistons against the resistances.

Abstract: An accumulator designed to alleviate a so-called N-D select shock is connected in a hydraulic control system for an automatic transmission such that it can also alleviate a 3-4 shift shock. The accumulator includes a piston and a spring biasing the piston. The spring force of the spring is appropriately set such that the piston starts moving against the spring in response to small pressure build-up of a drive range select pressure.

Abstract: A control for an automatic transmission with a lock-up type torque converter, comprises a lock-up control valve, a forward clutch control valve, an electromagnetic valve, and a shuttle valve. The shuttle valve normally assumes a first position where a control signal regulated by the electromagnetic valve is supplied to the forward clutch control valve to render same to regulate forward pressure for activating a forward clutch. The shuttle valve shifts to a second position thereof when the transmission establishes forward speed ratios except the first speed ratio. In the second position of the shuttle valve, the control pressure regulated by the electromagnetic valve is supplied to the lock-up control valve to render same to effect slip control and lock-up control of the torque converter.

Abstract: An accumulator designed to alleviate a so-called N-D select shock is connected in a hydraulic control system for an automatic transmission such that it can also alleviate a 3-4 shift shock. The hydraulic control system includes a solenoid that controls a first hydraulic fluid pressure which is variable in a first pattern, a pressure modifier valve that changes the first pattern of variation of the first hydraulic fluid pressure to a second pattern and generates a second hydraulic fluid pressure variable in a second pattern, and a pressure regulator that is responsive to the second hydraulic fluid pressure to generate a third hydraulic fluid pressure that varies in response to the second hydraulic fluid pressure.

Abstract: A transmission comprises two planetary gear sets which are interconnected to provide four forward speeds and one reverse between an input shaft and an output shaft, and friction elements arranged to cause the two planetary gear sets to provide any one of the four forward speeds. The friction elements include a clutch and a one-way clutch arranged in series with the clutch.

Abstract: An engine brake control for a transmission is disclosed. The transmission includes a hydraulically operated clutch selectively establishing a drive connection between a first rotary member and a second rotary member, and a one-way clutch arranged in parallel to the hydraulically operated clutch such that when the hydraulically operated clutch is released the one-way clutch transmits forward torque from the first rotary member to the second rotary member, but interrupts transmission of reverse torque to the first rotary member from the second rotary member. When a driver demands engine brake, a manual selector valve generates an engine brake command fluid pressure.

Abstract: There is provided in an automatic transmission a shift valve which is provided with a plug movable responsive to an engine brake command to hold a valve spool of the shift valve to a downshift position thereof. The plug is designed to supply working hydraulic pressure to an engine brake friction element after it has moved responsive to the engine brake command to hold the valve spool of the shift valve to the downshift position thereof. When the engine brake command is not available, the plug allows the valve spool of the shift valve to move between the downshift position thereof and an upshift position thereof.

Abstract: A hydraulic control system comprises a control valve with a solenoid valve operatively connected thereto to modulate the characteristic of hydraulic fluid pressure supplied to a friction element that is to be engaged during a shift in speed ratio. The current supplied to the solenoid is varied in ON/OFF manner in accordance with a duty factor computed by a control unit. The control unit includes a memory storing a map containing various duty factors corresponding to various kinds of shifts and determines an adequate duty factor for a shift which is to take place in the transmission. The characteristic of the hydraulic fluid pressure is modulated during a time period variable with vehicle speed and engine torque which are measured by sensors associated with the control unit.

Abstract: An accumulator designed to alleviate a so-called N-D select shock is connected in a hydraulic control system for an automatic transmission such that it can also alleviate a 3-4 shift shock. The accumulator includes a piston and a spring biasing the piston. The spring force of the spring is appropriately set such that the piston starts moving against the spring in response to small pressure build-up of a drive range select pressure.

Abstract: In order to obviate shift shock during shifting between second and third gears in a transmission wherein a front clutch and a band brake having apply and release chambers, an accumulator is connected to the circuit via which line pressure is supplied from a 2-3 shift valve in a manner that the engagement/release of the two friction elements is staged in a manner that reduces sharp fluctuations in the output shaft torque.

Abstract: A hydraulic control system according to the present invention which features in providing an orifice fluidly disposed in a passage that allows fluid supply of hydraulic fluid pressure to a clutch in selecting a forward drive range from a neutral range and in shifting between speed ratios involving engagement of the clutch in the forward drive range, and an orifice control valve having means for providing a one-way flow bypass passage bypassing the orifice in selecting the forward drive range from the neutral range and selecting the neutral range from the forward drive range, and providing a restricted flow bypass passage bypassing the orifice in shifting between speed ratios involving engagement of the clutch. The one-way flow bypass passage prevents fluid flow therethrough toward the clutch.

Abstract: An electro-hydraulic control for an automatic transmission for an automotive vehicle, comprises a 3-2 timing valve, an overrun clutch control valve, an electromagnetic valve under the control of a computer, and a shuttle valve. The shuttle valve has a spool movable responsive to a line pressure variable with the engine throttle opening degree. The spool is movable between a first position where the overrun clutch control valve is under the control of the electromagnetic valve and a second position where the 3-2 timing valve is under the control of the electromagnetic valve.

Abstract: Herein disclosed is an improved arrangement of a park lock device for use with an automatic transmission, by which the transmission casing can be constructed simple and compact in size. The park lock device comprises a parking gear secured to the output shaft of the transmission to rotate therewith; a parking pawl pivotally connected to the casing to lock and unlock the parking gear, the pawl including first and second wing portions which extend in the opposed directions from the pivoted portion of the pawl, the first wing portion being formed with a tooth lockably engageable with a tooth gap of the parking gear; and an actuating mechanism having a cam member which is slidably engageable with the second wing portion to pivot the parking pawl in a direction to achieve the locking engagement between the tooth of the parking pawl and the tooth gap of the parking gear. The actuating mechanism is positioned essentially inboard of the parking pawl with respect to the transmission casing.