Reduction Reducing Valve

Reduction Reducing Valve

Outline
^ The reduction reducing valve reduces the line pressure and adjusts to the reduction reducing pressure allowing the reduction brake to operate at the optimal pressure. while in the forward drive ranges, the line pressure is depressurized by the reduction reducing valve and is applied to the reduction brake. While in R position, the line pressure does not depressurize and is applied to the reduction brake.

Operation
^ Spring force and back pressure of accumulator control valve B (39) are applied to the bottom end of the valve and push the valve upward.

Forward drive range
^ Spring force and back pressure of accumulator control valve B (39) are applied to the bottom end of the valve and push the valve upward. Conversely, reduction brake operation pressure (38) flows through the inside of the valve, is applied to the top end of the valve, and pushes the valve downward. The back pressure of accumulator control valve B (39) and reduction brake operation pressure (38) maintain the balance. This causes line pressure (34) to decrease and is applied to the reduction brake.
^ When reduction brake operation pressure (38) is lower than back pressure of the accumulator control valve B (39), the valve moves upward and opens line pressure (34) oil passage (See figure). This causes the line pressure to flow through oil passage (34) to oil passage (38) and pressurizes reduction brake operation pressure (38). Pressurized reduction brake operation pressure (38) moves the valve downward and closes the oil passage of line pressure (34). This causes reduction brake operation pressure (38) to not depressurize. When reduction brake operation pressure (38) is higher than the back pressure of accumulator control valve (39), the valve moves downward and opens drain port (X) (See figure). This causes reduction brake operation pressure (38) to depressurize. When reduction brake operation pressure (38) is depressurized, the force to push the valve downward decreases, the valve moves upward and drain port (X) closes. This causes the reduction brake operation pressure to not depressurize. Thus, reduction brake operation pressure (38) is adjusted according to the change in the back pressure of accumulator control valve B (39).

R position
^ While in R position also, the valve operates by the balance of reduction brake operation pressure (38) and back pressure of accumulator control valve B (39), the same as when in the forward drive ranges. However, while in the R position, since the line pressure (reverse clutch operation pressure) is applied to the oil passage (4), the line pressure is applied to the reduction brake irrelevant of the valve motion.