Continuously variable transmission and method for controlling continuously variable transmission

Patent metadata

Field	Value
Publication number	US-10815846-B2
Application number	US-201616462604-A
Country	US
Kind code	B2
Filing date	Nov 24, 2016
Priority date	Nov 24, 2016
Publication date	Oct 27, 2020
Grant date	Oct 27, 2020

Abstract

A method for controlling a continuously variable transmission is a control method for controlling in/out of oil to/from a primary oil chamber by using an oil pump provided in an oil passage between the primary oil chamber and a secondary oil chamber. The method for controlling the continuously variable transmission includes: a current command value calculation step of calculating a current command value for the oil pump in accordance with an operating state; a current limiting step of limiting the current command value to a lower-limit current at which belt slip does not occur when an oil pressure in the primary oil chamber falls below a lower-limit oil pressure in the primary oil chamber at which the belt slip does not occur; and a pump control step of driving the oil pump by using the current command value to control a piston position of the primary oil chamber.

First claim

The invention claimed is:

1. A method for controlling a continuously variable transmission, the method controlling in/out of oil to/from a primary oil chamber by using an oil pump provided in an oil passage between the primary oil chamber and a secondary oil chamber, the method comprising:
a current command value calculation step of calculating a current command value for the oil pump in accordance with an operating state;
a pump control step of driving the oil pump by using the current command value to control a piston position of the primary oil chamber; and
a current limiting step of limiting the current command value to a lower-limit current at which belt slip does not occur when an oil pressure in the primary oil chamber falls below a lower-limit oil pressure in the primary oil chamber at which the belt slip does not occur, wherein
the current limiting step includes:
predicting a predicted oil pressure in the primary oil chamber when the oil pump is activated with the current command value and limiting the current command value to the lower-limit current when the predicted oil pressure falls below the lower-limit oil pressure; and
performing a correction by using at least one of a predicted differential pressure obtained by a transfer function or a deviation between a predicted value and a measured value in the predicting the predicted oil pressure in the primary oil chamber when the oil pump is activated with the current command value.

2. The method for controlling the continuously variable transmission according to claim 1 , wherein the current command value calculation step includes calculating the current command value for the oil pump in accordance with the operating state and a fed-back actual rotation speed of the oil pump.

3. The method for controlling the continuously variable transmission according to claim 1 , wherein the predicted oil pressure is corrected based on a deviation between a predicted value and a measured value of the oil pressure in the primary oil chamber when shift is not performed.

4. A method for controlling a continuously variable transmission, the method controlling in/out of oil to/from a primary oil chamber by using an oil pump provided in an oil passage between the primary oil chamber and a secondary oil chamber, the method comprising:
a current command value calculation step of calculating a current command value for the oil pump in accordance with an operating state;
a pump control step of driving the oil pump by using the current command value to control a piston position of the primary oil chamber; and
a current limiting step of limiting the current command value to a lower-limit current at which belt slip does not occur when an oil pressure in the primary oil chamber falls below a lower-limit oil pressure in the primary oil chamber at which the belt slip does not occur, wherein
the current limiting step includes predicting a predicted oil pressure in the primary oil chamber when the oil pump is activated with the current command value and limiting the current command value to the lower-limit current when the predicted oil pressure falls below the lower-limit oil pressure, and
the predicted oil pressure is calculated based on an oil pressure in the secondary oil chamber and a between-before-and-after differential pressure generated before and after the oil pump in which a current of the current command value flows.

5. The method for controlling the continuously variable transmission according to claim 4 , wherein the between-before-and-after differential pressure is calculated based on the current command value and a characteristic of the oil pump.

6. A control device for a continuously variable transmission comprising:
a primary oil chamber;
a secondary oil chamber;
an oil pump provided in an oil passage between the primary oil chamber and the secondary oil chamber; and
a controller configured to control the oil pump to control in/out of oil to/from the primary oil chamber,
the controller comprising:
a current command value calculating unit configured to calculate a current command value for the oil pump in accordance with an operating state;
a pump control unit configured to drive the oil pump by using the current command value to control a piston position of the primary oil chamber; and
a current limiting unit configured to limit the current command value to a lower-limit current at which belt slip does not occur when an oil pressure in the primary oil chamber falls below a lower-limit oil pressure in the primary oil chamber at which the belt slip does not occur, wherein

the current limiting unit:
predicts a predicted oil pressure in the primary oil chamber when the oil pump is activated with the current command value and limits the current command value to the lower-limit current when the predicted oil pressure falls below the lower-limit oil pressure; and
performs a correction using at least one of a predicted differential pressure obtained by a transfer function or a deviation between a predicted value and a measured value on the prediction of the predicted oil pressure in the primary oil chamber when the oil pump is activated with the current command value.

7. A control device for a continuously variable transmission comprising:
a primary oil chamber;
a secondary oil chamber;
an oil pump provided in an oil passage between the primary oil chamber and the secondary oil chamber; and
a controller configured to control the oil pump to control in/out of oil to/from the primary oil chamber,
the controller comprising:
a current command value calculating unit configured to calculate a current command value for the oil pump in accordance with an operating state;
a pump control unit configured to drive the oil pump by using the current command value to control a piston position of the primary oil chamber; and
a current limiting unit configured to limit the current command value to a lower-limit current at which belt slip does not occur when an oil pressure in the primary oil chamber falls below a lower-limit oil pressure in the primary oil chamber at which the belt slip does not occur, wherein

the current limiting unit:
predicts a predicted oil pressure in the primary oil chamber when the oil pump is activated with the current command value based on an oil pressure in the secondary oil chamber and a between-before-and-after differential pressure generated before and after the oil pump in which a current of the current command value flows; and
limits the current command value to the lower-limit current when the predicted oil pressure falls below the lower-limit oil pressure.

Assignees

• Nissan Motor

Inventors

• Terai Hiromu

Classifications

• F16H61/66259 Primary

  using electrical or electronical sensing or control means · CPC title

• F16H61/0025

  Supply of control fluid; Pumps therefor · CPC title

• F16H61/0204

  for gearshift control, e.g. control functions for performing shifting or generation of shift signal · CPC title

• F01M1/16 Primary

  Controlling lubricant pressure or quantity (rendering machines or engines inoperative or idling on lubricant pressure failure F01M1/22) · CPC title

• F16H7/023

  with belts having a toothed contact surface or regularly spaced bosses or hollows for slipless or nearly slipless meshing with complementary profiled contact surface of a pulley · CPC title