Control system for continuously variable transmission in motor vehicle

Claim 1

A method for controlling a speed of an engine in a motor vehicle using a continuously variable transmission, the transmission having a driving pulley comprising a fixed member and a movable member, the movable member being actuated by a hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley with another fixed member and another movable member, said another movable member being similarly actuated by another hydraulic cylinder to form a similar V-shaped opening between said another movable member and said another fixed member, and a flexible belt member spanning the pulleys so that the diameters of the pulleys can be varied with regard to each other with the movable members of the driving and driven pulleys being moved by the respective hydraulic cylinder, whereby different speed ratios can be obtained, the method comprising the steps of: detecting a change in a throttle position in throttle means on the engine; detecting an actual engine speed at a point immediately after said change occurs in the throttle position in the throttle means; determining a desired steady state engine speed corresponding to a newly established throttle position established by said change; determining an intermediate engine speed as a desired engine speed in a transient shifting condition of the continuously variable transmission which is established by said change in the throttle position, said intermediate engine speed used during acceleration of the vehicle being different in value from that used during deceleration of the vehicle, and being intermediate in value between the determined desired steady state engine speed and the detected actual engine speed; changing the actual engine speed to said intermediate engine speed; and gradually changing the actual engine speed from the intermediate engine speed to said determined desired steady state engine speed corresponding to said newly established throttle position.

Claim 2

A method for controlling a speed of an engine in a motor vehicle using a continuously variable transmission, the transmission having a driving pulley comprising a fixed member and a movable member, the movable member being actuated by a hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley with another fixed member and another movable member, said another movable member being similarly actuated by another hydraulic cylinder to form a similar V-shaped opening between said another movable member and said another fixed member, and a flexible belt member spanning the pulleys so that the diameters of the pulleys can be varied with regard to each other with the movable members of the driving and driven pulleys being moved by the respective hydraulic cylinder, whereby different speed ratios can be obtained, the method comprising the steps of: detecting a change in a throttle position in throttle means on the engine; detecting an actual engine speed at a point immediately after said change occurs in the throttle position in the throttle means; determining a desired steady state engine speed corresponding to a newly established throttle position established by said change; determining an intermediate engine speed as a desired engine speed in a transient shifting condition of the continuously variable transmission which is established by said change in the throttle position, said intermediate engine speed used during acceleration of the vehicle being different in value from that used during deceleration of the vehicle, and being intermediate in value between the determined desired steady state engine speed and the detected actual engine speed; changing the actual engine speed to said intermediate engine speed; and gradually changing the actual engine speed from the intermediate engine speed to said determined desired steady state engine speed corresponding to said newly established throttle position.

Claim 4

A method for controlling a speed of an engine in a motor vehicle using a continuously variable transmission, the transmission having a driving pulley comprising a fixed member and a movable member, the movable member being actuated by a hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley with another fixed member and another movable member, said another movable member being similarly actuated by another hydraulic cylinder to form a similar V-shaped opening between said another movable member and said another fixed member, and a flexible belt member spanning the pulleys so that the diameters of the pulleys can be varied with regard to each other with the movable members of the driving and driven pulleys being moved by the respective hydraulic cylinders, whereby different speed ratios can be obtained, the method comprising the steps of: detecting a change in a throttle position in throttle means on the engine; determining a desired steady state engine speed corresponding to a newly established throttle position established by said change; detecting an actual engine speed at a point immediately after said change occurs in the throttle position in the throttle means; calculating a magnitude of a difference between the determined desired steady state engine speed and the detected actual engine speed; determining whether the calculated magnitude of said difference exceeds a predetermined value, or not; if said calculated magnitude exceeds said predetermined value, determining an intermediate engine speed as a desired engine speed in a transient shifting condition of said transmission, said intermediate engine speed being intermediate between the determined desired steady state engine speed and the detected actual engine speed, said intermediate engine speed used during acceleration of the vehicle being different from that used during deceleration of the vehicle; and changing the actual engine speed to the determined intermediate engine speed, upon elapse of a predetermined time after said change in the throttle position occurrs.

Claim 5

A method for controlling a speed of an engine in a motor vehicle using a continuously variable transmission, the transmission having a driving pulley comprising a fixed member and a movable member, the movable member being actuated by a hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley with another fixed member and another movable member, said another movable member being similarly actuated by another hydraulic cylinder to form a similar V-shaped opening between said another movable member and said another fixed member, and a flexible belt member spanning the pulleys so that the diameters of the pulleys can be varied with regard to each other with the movable members of the driving and driven pulleys being moved by the respective hydraulic cylinders, whereby different speed ratios can be obtained, the method comprising the steps of: detecting a change in a throttle position in throttle means on the engine; determining a desired steady state engine speed corresponding to a newly established throttle position established by said change; detecting an actual engine speed at a point immediately after said change occurs in the throttle position in the throttle means; calculating a magnitude of a difference between the determined desired steady state engine speed and the detected actual engine speed; determining whether the calculated magnitude of said difference exceeds a predetermined value, or not; if said calculated magnitude exceeds said predetermined value, determining an intermediate engine speed as a desired engine speed in a transient shifting condition of said transmission, said intermediate engine speed being intermediate between the determined desired steady state engine speed and the detected actual engine speed, said intermediate engine speed used during acceleration of the vehicle being different from that used during deceleration of the vehicle; and changing the actual engine speed to the determined intermediate engine speed, upon elapse of a predetermined time after said change in the throttle position occurrs.

Claim 11

A method for controlling a speed of an engine in a motor vehicle using a continuously variable transmission, the transmission having a driving pulley comprising a fixed member and a movable member, the movable member being actuated by a hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley with another fixed member and another movable member, said another movable member being similarly actuated by another hydraulic cylinder to form a similar V-shaped opening between said another movable member and said another fixed member, a flexible belt member spanning the pulleys, and electronic control means, the electronic control means including memory means for storing a relationship between a desired engine speed and a throttle position, said electronic control means controlling pressures in the hydraulic cylinders so as to provide an optimal desired engine speed of the engine, the method comprising the steps of: detecting a change in a throttle position in throttle means provided on said engine, from a first throttle position to a second throttle position; determining a first desired steady state engine speed corresponding to said first throttle position, and a second desired steady state engine speed corresponding to said second throttle position, said first and second steady state engine speeds being determined from said first and second throttle positions, respectively, in accordance with said relationship stored in said memory means; calculating a difference between said first and second desired steady state engine speeds; comparing said difference with a predetermined value; determining a transient value as a desired engine speed in a transient condition of the transmission, said transient value being intermediate between said first and second desired engine speed, said transient value during acceleration of the vehicle being different from that used during deceleration of the vehocle; and changing an actual engine speed of the engine in accordance with said comparison, such that when said difference is smaller than said predetermined value, said actual engine speed is changed to approach said second desired engine speed gradually at a rate lower than that when said difference is larger than said predetermined value, and such that when said difference is larger than said predetermined value, said actual engine speed is rapidly changed to said transient value, and is then gradually changed from the determined transient value to approach said second desired engine speed.

Claim 12

A method for controlling a speed of an engine in a motor vehicle using a continuously variable transmission, the transmission having a driving pulley comprising a fixed member and a movable member, the movable member being actuated by a hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley with another fixed member and another movable member, said another movable member being similarly actuated by another hydraulic cylinder to form a similar V-shaped opening between said another movable member and said another fixed member, a flexible belt member spanning the pulleys, and electronic control means, the electronic control means including memory means for storing a relationship between a desired engine speed and a throttle position, said electronic control means controlling pressures in the hydraulic cylinders so as to provide an optimal desired engine speed of the engine, the method comprising the steps of: detecting a change in a throttle position in throttle means provided on said engine, from a first throttle position to a second throttle position; determining a first desired steady state engine speed corresponding to said first throttle position, and a second desired steady state engine speed corresponding to said second throttle position, said first and second steady state engine speeds being determined from said first and second throttle positions, respectively, in accordance with said relationship stored in said memory means; calculating a difference between said first and second desired steady state engine speeds; comparing said difference with a predetermined value; determining a transient value as a desired engine speed in a transient condition of the transmission, said transient value being intermediate between said first and second desired engine speed, said transient value during acceleration of the vehicle being different from that used during deceleration of the vehocle; and changing an actual engine speed of the engine in accordance with said comparison, such that when said difference is smaller than said predetermined value, said actual engine speed is changed to approach said second desired engine speed gradually at a rate lower than that when said difference is larger than said predetermined value, and such that when said difference is larger than said predetermined value, said actual engine speed is rapidly changed to said transient value, and is then gradually changed from the determined transient value to approach said second desired engine speed.