Shift control device and shift control method of vehicular continuously variable transmission

• US 20080039279A1
• Filed: 07/12/2007
• Published: 02/14/2008
• Est. Priority Date: 08/11/2006
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Ogata, Yusuke, Soga, Yoshinobu
• Granted Patent: US 7,568,995 B2
• Time in Patent Office: Days
• US Class Current: 477/45
• CPC Class Codes: F16H 61/16 Inhibiting or initiating shift during unfavourable conditions, e.g. preventing forward reverse shift at high vehicle speed, preventing engine over speed unintentional control input F16H61/18
• CPC Class Codes: F16H 61/66259 using electrical or electronical sensing or control means
• CPC Class Codes: F16H 61/66263 using only hydraulical and mechanical sensing or control means

Abstract

A hydraulic control circuit that shuts off an oil passageway so that the ratio between the shift pressure and the belt clamping pressure is not caused to be in a predetermined relationship even when a speed change ratio control valve and/or a speed change ratio control valve are not supplying/discharging hydraulic oil. Therefore, even if the speed change ratio control valve and/or the speed change ratio control valve cease supplying/discharging the hydraulic oil, the action of a thrust ratio control oil pressure Pτ output from a thrust ratio control valve on a primary hydraulic cylinder is avoided. Thus, impairment of the continuity of control at the time of a shift of the continuously variable transmission is prevented.

Claims

1. A shift control device of a vehicular continuously variable transmission that is provided in a power transmission path between a vehicle power source and a driving wheel, and that includes a primary pulley;

a secondary pulley;

a belt, wrapped around the two pulleys;

a primary hydraulic cylinder that alters a groove width of the primary pulley; and

a secondary hydraulic cylinder that alters the groove width of the secondary pulley;

comprising;

a hydraulic circuit having a shift control valve that adjusts an amount of hydraulic oil supplied to or discharged from the primary hydraulic cylinder in order to shift the continuously variable transmission, and a pressure reducing valve that causes a ratio between an oil pressure in the primary hydraulic cylinder and the oil pressure in the secondary hydraulic cylinder to be in a predetermined relationship by causing a predetermined oil pressure to act on the primary hydraulic cylinder when the shift control valve is not supplying/discharging the hydraulic oil, the hydraulic circuit shutting off an oil passageway connecting an output port of the pressure reducing valve and the primary hydraulic cylinder so that the ratio is not caused to be in the predetermined relationship even when the shift control valve is not supplying/discharging the hydraulic oil.

2. The shift control device according to claim 1, wherein the hydraulic circuit is selectively switchable among a first state, in which the shift control valve is supplying/discharging the hydraulic oil and the oil passageway is shut off;

a second state, in which the shift control valve is not supplying/discharging the hydraulic oil and the oil passageway is shut off; and

a third state, in which the shift control valve is not supplying/discharging the hydraulic oil and the oil passageway is opened.

3. The shift control device according to claim 2,

wherein the hydraulic circuit is constructed so as to be capable of shutting off the oil passageway by the shift control valve, and

wherein the shift control valve is selectively switchable among the first state, the second state and the third state.

4. The shift control device according to claim 1, wherein the predetermined relationship is such that a speed change ratio of the continuously variable transmission is caused to be a maximum speed change ratio.

5. A shift control method of a vehicular continuously variable transmission comprising:

determining whether an amount of hydraulic oil supplied to or discharged from a primary hydraulic cylinder is adjusted in order to shift a continuously variable transmission that includes the primary hydraulic cylinder that alters a groove width of a primary pulley; and

a secondary hydraulic cylinder that alters the groove width of a secondary pulley;

determining whether a predetermined oil pressure to act on the primary hydraulic cylinder is caused so that a ratio between an oil pressure in the primary hydraulic cylinder and the oil pressure in the secondary hydraulic cylinder is caused to be in a predetermined relationship; and

executing a control so that the ration is not caused to be in a predetermined relationship even when the shift control valve is not supplying/discharging the hydraulic oil, when it is determined that a predetermined condition is met.

6. The shift control method according to claim 5, wherein it is determined that the predetermined condition is met, when an actual input shaft speed of the continuously variable transmission becomes a target input shaft speed.

7. The shift control method according to claim 5, wherein

the predetermined oil pressure is acted on the primary hydraulic cylinder so that the ratio between the oil pressure in the primary hydraulic cylinder and the oil pressure in the secondary hydraulic cylinder is caused to be in the predetermined relationship, when it is determined that a vehicle speed is below a predetermined vehicle speed.

8. The shift control method according to claim 7, wherein the predetermined relationship is such that a speed change ratio of the continuously variable transmission is caused to be a maximum speed change ratio.