There are two types of brakes fixing elements: the band type and the wet multiple-disc type. The band type is used for the B1 brake and the wet multiple-disc type for the B2 and B3 brakes. In some automatic transaxles, the wet multiple- disc type is used for the B1 brake also.
1.Band type brake (B1)
The brake band is wound the outer circumference of the drum. One end of this brake band is locked to the transaxle case with a pin, while the other end contacts the brake piston through the piston rod, which is operated by hydraulic pressure. The brake piston can move on the piston rod by compressing the springs. Piston rods of two different lengths are provided to enable the clearance between the brake band and drum to be adjusted.
When the brake band is being replaced with a new one during overhauling of an automatic transaxle, soak the new brake band for 15 minutes or longer in the ATF (Automatic Transaxle Fluid) before installation.
2. Band type brake (B1) operation
When hydraulic pressure is applied to the piston, the piston moves to the left in the piston cylinder, compressing the springs. The piston rod moves to the left with the piston and pushes one end of the brake band. As the other end of the brake band is fixed to the transaxle case, the diameter of the brake band decreases, so the brake band clamps down on the drum, holding it immovable. At this time, a high frictional force is generated between the brake band and drum to cause the drum, or a member of the planetary gear set, to become immovable. When the pressurized fluid is drained from the cylinder, the piston and piston rod are pushed back by the force of the outer spring, so the drum is released by the brake band. Also, the inner spring has two functions: to absorb the reactive force from the drum, and to reduce the shock that is generated when the brake band clamps the drum.
3. Wet Multiple- disc Type Brakes (B2 and B3)
The B2 brake operates via the No.1 one-way clutch to prevent the front and rear sun gears from turning counterclockwise. The discs are splined to the outer race of the No.1 one-way clutch, and the plates are fixed to the transaxle case. The No.1 one-way clutch’s inner race (front and rear sun gears) is so designed that when it turns counterclockwise, it locks but when it turns clockwise it is able to turn freely. The purpose of the B3 brake is to prevent rotation of the rear planetary carrier. The discs mesh with the B3 hub of the rear planetary carrier. The B3 hub and rear planetary carrier are built in one unit and rotate together. The plates are fixed to the transaxle case.
4. Wet Multiple-disc Type Brakes (B2 and B3) operation
When hydraulic pressure is applied to the piston cylinder, the piston moves inside the cylinder, forcing the plates and discs into contact with each other. Consequently, a high frictional force is generated between each disc and plate. As a result, the carrier or sun gear is locked to the transaxle case. When the pressurized fluid is drained from the piston cylinder, the piston is returned to its original position by the return spring, causing the brake to be released.
The number of brake 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 brake discs with new discs, soak the new discs in the ATF for 15 minutes or longer before installation.