Hydraulic pressure control device for vehicle continuously variable transmission

Abstract

A hydraulic pressure control device is provide for a belt type continuously variable transmission that appropriately controls hydraulic pressure supplied to each pulley. The hydraulic pressure control device has a positive input torque calculation section that calculates a positive input torque that is inputted to a primary pulley from an engine; a negative input torque calculation section that calculates a negative input torque based on the calculated speed ratio and the positive input torque; and a hydraulic pressure regulation section that calculates a hydraulic pressure of hydraulic fluid supplied to each pulley depending on the sum of the positive input torque and the negative input torque and controls hydraulic pressure to each the pulley to the calculated hydraulic pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure:

FIG. 1 is a simplified schematic view of a vehicle equipped with a belt type continuously variable transmission in accordance with a first embodiment of the present invention;

FIG. 2 is a graph for explaining the relationship between an input torque to a continuously variable section and the slipping of a V-belt;

FIG. 3 is a time chart for explaining hydraulic pressure control when there is a changeover from an on-road running state to an off-road running state;

FIG. 4 is a characteristic view of a negative input torque;

FIG. 5 is a flow chart showing the control operations executed by the control unit in order to calculate the supply hydraulic pressures to a primary pulley and a secondary pulley;

FIG. 6 is a map of necessary secondary pressure depending on speed ratio and total torque; and

FIG. 7 is a map of necessary primary pressure depending on speed ratio and total torque.

Claims

1. A hydraulic pressure control device comprising: a speed ratio calculation section configured to calculate a speed ratio between a primary pulley and a secondary pulley of a belt type continuously variable transmission;a running state determination section configured to determine if a vehicle running state exists in which a negative input torque will be likely to be inputted to the primary pulley from a drive wheel;a positive input torque calculation section configured to calculate a positive input torque that is inputted to the primary pulley from an engine;a negative input torque calculation section configured to calculate a negative input torque based on the speed ratio and the positive input torque that were calculated;a primary pressure regulation section configured to perform pressure regulation of hydraulic fluid supplied to the primary pulley;a secondary pressure regulation section configured to perform pressure regulation of hydraulic fluid supplied to the secondary pulley; anda hydraulic pressure calculation section configured to regulate a target hydraulic pressure of hydraulic fluid supplied to the primary pulley and a target hydraulic pressure of hydraulic fluid supplied to the secondary pulley depending on a sum of the positive input torque and the negative input torque that were calculated and to control the primary pressure regulation section and the secondary pressure regulation section obtain target hydraulic pressures of the primary pulley and the secondary pulley.

2. The hydraulic pressure control device as recited in claim 1, further comprising a running state changeover section configured to change a running state in which the negative input torque occurs and a running state in which the negative input torque does not occur, andthe running state determination section configured to determine a current running state depending on an output signal of the running state changeover section.

3. The hydraulic pressure control device as recited in claim 2, wherein the running state determination section is further configured to determine an off-road running state as the vehicle running state in which the negative input torque is likely to occur and an off-road running state as the vehicle running state in which the negative input torque is not likely to occur is an on-road running state, with the off-road running state having a greater speed ratio than the on-road running state.

4. The hydraulic pressure control device as recited in claim 1, wherein the hydraulic pressure calculation section is further configured to calculate torque capacity of the belt type continuously variable transmission and controls the pressure regulation in a range when the calculated torque capacity is greater than the sum of the positive input torque and the negative input torque.

5. A hydraulic pressure control device comprising: speed ratio calculation means for calculating a speed ratio between a primary pulley and a secondary pulley of a belt type continuously variable transmission;running state determination means for determining if a vehicle running state exists in which a negative input torque will be likely to be inputted to the primary pulley from a drive wheel side;positive input torque calculation means for calculating a positive input torque that is inputted to the primary pulley from an engine;negative input torque calculation means for calculating a negative input torque based on the speed ratio and the positive input torque that were calculated;primary pressure regulation means for regulating pressure of hydraulic fluid supplied to the primary pulley;secondary pressure regulation means for regulating pressure of hydraulic fluid supplied to the secondary pulley; andhydraulic pressure calculation means for calculating a target hydraulic pressure of hydraulic fluid supplied to the primary pulley and a target hydraulic pressure of hydraulic fluid supplied to the secondary pulley depending on a sum of the positive input torque and the negative input torque that were calculated and to control the primary pressure regulation means and the secondary pressure regulation means obtain the target hydraulic pressures of the primary pulley and the secondary pulley.