摘要:
A hydraulic servo includes a cylinder, a piston and a rod. The piston divides the interior space of the cylinder between a closed hydraulic chamber and a back chamber which has an opening to the interior space of an automatic transmission. The rod is slidably mounted in the piston for relative movement through a predetermined distance. A frictional engagement element is engaged by the rod which is extended from one end of the cylinder by applying a hydraulic pressure to the hydraulic chamber. A passage is provided between the piston and the rod which is opened or closed by the relative movement between the piston and rod so that the hydraulic chamber and the back chamber are connected or disconnected. A valving arrangement (“closer”) closes the passage at the end of the return stroke of the piston toward the hydraulic chamber.
摘要:
The automatic transmission of the present invention prevents fluctuation of torque transmission through a band brake. In the hydraulic operator for the band brake, a resilient elastic cushion is provided between a rod abutting one end of the band of the band brake and a piston. Any slippage between the band and drum of the band brake will result in oscillation of the rod. However, the elastic cushion absorbs oscillation of the rod, thereby isolating the piston from that oscillation.
摘要:
When a vehicle is halted with the transmission in a forward drive range, an input clutch is disengaged to enhance the fuel efficiency and, at the same times a hill-hold brake is engaged to prevent the vehicle from rolling backward on a steep up-slope. At that time, the hydraulic pressure P.sub.C-1 of the input clutch C1 is gradually reduced by .DELTA.P.sub.CIR (P.sub.C-1 =P.sub.C-1 -.DELTA.P.sub.CIR) while the hydraulic pressure P.sub.B-1 of the hill-hold brake B1 is increased gradually so as to satisfy an equation P.sub.B-1 =K1+K2 X e where .DELTA.P.sub.cir is a change in hydraulic pressure which is required for gradually disengaging the first clutch C1, K1 is a hill-hold brake pressure at which braking resistance begins, K2 is hill-hold brake pressure producing a fully braked condition, and e is the input/output rotational-speed ratio of a torque converter Subsequently during start of vehicle movement, the hydraulic pressure P.sub.C-1 of the input clutch C1 is gradually increased (P.sub.C-1 =p.sub.C-1 +.DELTA.P.sub.C-1A) while the hydraulic pressure P.sub.B-1 of the hill-hold brake B1 is gradually decreased (P.sub.B-1 ==P.sub.B-1-.DELTA.P.sub.B-1) until the ratio of the rotational speed N.sub.C-1 of the first clutch C1 becomes less than a rotational speed N.sub.C-1E corresponding to the clutch being almost engaged .DELTA.P.sub.C-1A and .DELTA.P.sub.B-1 are incremental values proportional to accelerator depression so that a delay in starting is reduced in accordance with driver demand.
摘要:
A control apparatus executes appropriate speed change control under any operating conditions encountered during an up-shift by change-over, without requiring an increase in control logic. Engagement side hydraulic pressure is swept up as a result of an arithmetic operation in torque phase speed change control. Disengagement side hydraulic pressure is calculated by initial speed change control, dependent on the engagement side hydraulic pressure. The engagement side hydraulic pressure is directly controlled and the disengagement side hydraulic pressure is indirectly controlled, i.e. responsive to the engagement side control. Consequently, the same control scheme can be executed regardless of power-on state or power-off state and regardless of vehicle operating conditions.
摘要:
A system and method for controlling an automatic transmission in a vehicle drive train including an engine, the automatic transmission and a fluid coupling for transmitting the rotation of the engine to the transmission. The transmission includes a clutch applied when a forward running range is selected; a second one-way clutch which is applied, when the first clutch is applied, to establish a forward 1st speed; and a brake for locking the one-way clutch, when applied, to block the reverse rotation of the output shaft of the transmission. A first hydraulic servo receives a first oil pressure for applying the first clutch and a second hydraulic servo receives a second oil pressure for applying the brake. When a forward running range is selected, with the vehicle stopped, the engine idling and a foot brake engaged, the oil pressure of the first hydraulic servo is lowered from the oil pressure at the 1st speed whereas the oil pressure of the second hydraulic servo is raised to a modulated pressure. The modulated pressure is set to generate, against the reverse force on the vehicle facing up an incline, a resistance corresponding to the forward driving force generated when the engine is idling in 1st speed.
摘要:
An automatic transmission control system providing a neutral control state in which there is no slipping engagement of a first clutch which is engaged upon selection of a forward range and, as a result, the vehicle is not subjected to idling vibration. The fuel consumption reducing effect of the neutral control state is maintained and there is no heating and consequent deterioration of the friction material of the clutch. The control system includes a hydraulic servo for operation of the clutch, an input side speed sensor for detecting the input side speed of a fluid power coupling device connecting the transmission to the output of an engine, an output side speed sensor for detecting the output side speed of the fluid power coupling device, and a controller. The controller includes differential speed calculator, differential speed change detector, a pressure increasing device for increasing the hydraulic pressure of the hydraulic servo by a set pressure when the differential speed has not changed, and a pressure reducing device for reducing the hydraulic pressure of the hydraulic servo by a set pressure when the differential speed has changed.
摘要:
When a vehicle driving state of an automatic transmission is changed to a power-off state from a power-on state during a down shift involving the disengagement of one friction element and the engagement of another friction element, a disengagement side pressure PA is reduced rapidly by a feedback control based on the change in gear ratio because of a reduction of an input torque. The disengagement side pressure control is unable to complete change of the gear ratio to complete the down shift. When the disengagement side pressure is reduced to a value less than a return spring load pressure PG or when the gear ratio change has not achieved a basic value in a predetermined time, the down shift control is changed from primary control by the disengagement side pressure control to primary control by an engagement side control so that the gear ratio change is completed by control of the engagement side pressure.
摘要:
In power-on, high-vehicle-speed and high-torque conditions, a control unit sets a torque allotment ratio such that a main clutch bears all the torque. Thereby, the input shaft rotational speed is increased by controlling solely the main clutch releasing pressure. In power-on and low-torque or low-vehicle-speed conditions, the control unit sets a torque allotment ratio for the main clutch torque and the sub-clutch torque to 1:1. Thereby, control of the main clutch releasing pressure and control of the sub-clutch engaging pressure simultaneously proceed in parallel to produce a change in the input shaft rotational speed without a time lag. The hydraulic control apparatus thus conducts proper downshift control for a shift involving clutch engagement changeover, under all vehicle running conditions, without need for additional control logic.
摘要:
To achieve a predetermined speed by engaging or releasing friction engagement elements of an auxiliary shift mechanism, a fluid pressure changeover valve is switched to a position for communication between a regulated pressure input port and an output port, so that regulated fluid pressure from a pressure regulating valve is supplied through second shift mechanism-side shift valves to the friction engagement elements of the auxiliary shift mechanism to be engaged or released. This position switch of the changeover valve also connects a line pressure input port to an output port whereby line pressure is supplied to the main shift mechanism-side shift valves to maintain the main shift mechanism in a predetermined speed state. To achieve a predetermined speed by a shift in the main shift mechanism, the regulated pressure input port is connected to the output port providing communication with the main shift mechanism shift valves, and the line pressure input port becomes connected to the output port providing communication with the auxiliary shift mechanism shift valves.
摘要:
During transmission shifts, a band brake is used in either a self-loosening direction in which an engaging force thereof is not sensitive to variations in hydraulic pressure or a self-tightening direction in which the engaging force is sensitive to variations in hydraulic pressure. In the self-loosening direction, a second regulated hydraulic pressure generated by a second pressure regulating valve (B-4 control valve) in accordance with a control hydraulic pressure generated by a second (throttle-pressure-control) linear solenoid valve in a margin control region thereof is supplied to a hydraulic servo of the fourth brake (band brake). In this clutch-to-clutch shift, a first regulated hydraulic pressure generated by a first pressure regulating valve (a shift-pressure control valve) in accordance with a control hydraulic pressure generated by a first (pressure-regulation) linear solenoid valve is supplied to a hydraulic servo of a third (UD direct) clutch. In the self tightening direction, the first regulated hydraulic pressure generated by the first pressure regulating valve (the shift-pressure control valve) is supplied to the hydraulic servo of the fourth brake (band brake).