The clutches connecting and disconnecting the power are C1 and C2. The clutch C1 acts to transmit power from the torque converter to the front ring gear via the input shaft. The discs and plates are lined up alternately. The discs are splined to the front ring gear and the plates are splined to the forward clutch drum. The front ring gear is splined to the ring gear flange and the forward clutch drum is splined to the direct clutch hub. The clutch C2 transmits power from the input shaft to the direct clutch drum (sun gear). The discs are splined to the direct clutch hub and the plates are splined to the direct clutch drum. The direct clutch drum meshes with the sun gear input drum and the sun gear input drum is splined to the front and rear sun gears. The structure is such that the three units of discs, plates, and drums turn together.
1. Engaged (C1)
When pressurized fluid flows into the piston cylinder, it pushes the piston check ball, causing it to close off the check valve. This in turn causes the piston to move inside the cylinder, forcing the plates into contact with the discs. Because of the high frictional force between plates and discs, the drive side plates and driven discs rotate at the same speed. This means that the clutch is engaged, the input shaft is connected to the ring gear, and the power from the input shaft is transmitted to the ring gear.
2. Disengaged (C1)
When the hydraulic pressurized is released, the fluid pressure in the cylinder decreases. This allows the check ball to move away from the check valve, which it attempts to do due to the centrifugal force that is applied to it, and the fluid in the cylinder is drained out through the check valve. As a result, the piston is returned by the return spring to it its original position, disengaging the clutch.
The number of clutch discs and plates differs depending on the automatic transaxle model. Even in automatic transaxles of the same model, the number of discs may differ depending on the engine the transaxle is combined with.
When replacing clutch discs with new discs, soak the new discs in the ATF for 15 minutes or longer before installation.
3. Centrifugal fluid pressure canceling
In the conventional clutch mechanism, to prevent the generation of pressure by the centrifugal force that is applied to the fluid in the piston fluid pressure chamber when the clutch is released, a check ball is provided to discharge the fluid. Therefore, before the clutch can be subsequently applied, it took time for the fluid to fill the piston fluid pressure chamber. During shifting, in addition to the pressure that is controlled by the valve body, the pressure that is applied on the fluid in the piston fluid pressure chamber also exerts influence, which is dependent upon engine speed fluctuations. In order to eliminate this influence, a canceling fluid pressure chamber is provided opposite to the piston fluid pressure chamber. By utilizing the lubrication fluid such as that of the shaft, the same amount of centrifugal force is applied, thus canceling the centrifugal force that is applied to the piston itself. Accordingly, it is not necessary to discharge the fluid through the use of a check ball, and a highly responsive and smooth shifting characteristic has been achieved.
When the planetary gear unit is designed without considering shifting shock, B2, F1, and F2 are not necessary. Just C1, C2, B1, and B3 are adequate. Also, it is difficult to make the fluid pressure is applied on the brake simultaneous with the moment that the clutch operating fluid pressure is released. Therefore, the No.1 one-way clutch (F1) operates via the B2 brake to prevent the front and rear sun gears from turning counterclockwise. The No.2 one-way clutch (F2) prevents the rear planetary carrier from turning counterclockwise. The outer race of the No.2 one-way clutch is fixed to the transaxle case. It is assembled so that it locks when the inner race (rear planetary carrier) is turning counterclockwise and turns freely when the inner race is turning clockwise. In this way, using one-way clutches switches the gears by always applying or releasing the fluid pressure on one element. That is, the function of the one-way clutch in the planetary gear unit is to ensure smooth gear shifting.