Continuously variable transmission control device and control method

Patent metadata

Field	Value
Publication number	US-11054028-B2
Application number	US-201816643650-A
Country	US
Kind code	B2
Filing date	Nov 13, 2018
Priority date	Nov 14, 2017
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A CVT is provided with a primary pulley ( 1 ) and a secondary pulley ( 2 ) between which a belt ( 3 ) is wound, and hydraulic pressure control valves ( 5, 6, 7 ) which control pulley hydraulic pressures. A CVT controller ( 8 ) sets a base current indicated value to be output to solenoids ( 5 a, 6 a, 7 a ) of the hydraulic pressure control valves ( 5, 6, 7 ), on the basis of a pulley hydraulic pressure indicated value. A dither control unit ( 58 ) of the CVT controller ( 8 ) superimposes a dither current onto the base current indicated value to be output to the solenoids ( 5 a, 6 a, 7 a ) if, during pulley hydraulic pressure control, the situation is determined, on the basis of belt slip determination information, to be such that belt slipping is highly likely to occur.

First claim

The invention claimed is:

1. A continuously variable transmission control device comprising:
a hydraulic pressure control valve structured to control a pulley hydraulic pressure supplied to primary and secondary pulleys, wherein a belt is wound around the primary and secondary pulleys; and
a controller configured to set a command base current outputted to a solenoid of the hydraulic pressure control valve, based on a command value of the pulley hydraulic pressure;
wherein the controller includes a dither control section configured to:
acquire belt-slip-determining information for determining a possibility of occurrence of slip of the belt during control of the pulley hydraulic pressure; and
perform a dither operation in response to a determination based on the belt-slip-determining information that the possibility of occurrence of slip of the belt is high, wherein the dither operation is to superimpose a dither current on the command base current.

2. The continuously variable transmission control device as claimed in claim 1 , wherein the dither control section is configured to perform the dither operation based on safety factor determination by:
acquiring a safety factor as the belt-slip-determining information during control of the pulley hydraulic pressure (Ppri, Psec), wherein the safety factor is a ratio of an actual belt thrust to a required belt thrust; and
determining the possibility of occurrence of slip of the belt as being high, in response to a determination that the safety factor is less than a predetermined value.

3. The continuously variable transmission control device as claimed in claim 2 , wherein the dither control section is configured to perform the dither operation in response to satisfaction of a start condition, wherein the start condition is a condition that the determination that the safety factor is less than the predetermined value has continued for a predetermined time period.

4. The continuously variable transmission control device as claimed in claim 1 , wherein the dither control section is configured to perform the dither operation based on secondary pressure fall determination by:
acquiring an oil quantity balance lower limit pressure as the belt-slip-determining information during control of the pulley hydraulic pressure, wherein the oil quantity balance lower limit pressure is a lower limit of a secondary pressure that is determined by an oil quantity balance based on a quantity of oil discharged from an oil pump; and
determining the possibility of occurrence of slip of the belt as being high, in response to a determination that an actual value of the secondary pressure is lower than the oil quantity balance lower limit pressure.

5. The continuously variable transmission control device as claimed in claim 4 , wherein the dither control section is configured to perform the dither operation based on the secondary pressure fall determination by:
setting a first start condition for starting the dither operation in a situation that the control of the pulley hydraulic pressure is in a steady state, and a second start condition for starting the dither operation in a situation that the control of the pulley hydraulic pressure is in a transient state, wherein the first start condition is different from the second start condition;
setting the first start condition to contain a first delay from the secondary pressure fall determination to start of the dither operation; and
setting the second start condition to contain a second delay from the secondary pressure fall determination to start of the dither operation, wherein the second delay is shorter than the first delay.

6. The continuously variable transmission control device as claimed in claim 1 , wherein the dither control section is configured to:
determine whether or not a hydraulic pressure deviation is greater than or equal to a predetermined pressure value during control of the pulley hydraulic pressure, wherein the hydraulic pressure deviation is a deviation between a command secondary pressure and an actual secondary pressure; and
perform the dither operation based on safety factor determination and based on secondary pressure fall determination simultaneously, in response to a determination that the hydraulic pressure deviation is greater than or equal to the predetermined pressure value, wherein the safety factor determination employs a safety factor that is a ratio of an actual belt thrust to a required belt thrust, and wherein the secondary pressure fall determination employs an oil quantity balance lower limit pressure that is a lower limit of the actual secondary pressure that is determined by an oil quantity balance based on a quantity of oil discharged from an oil pump.

7. A continuously variable transmission control method for a continuously variable transmission including a hydraulic pressure control valve structured to control a pulley hydraulic pressure supplied to primary and secondary pulleys, wherein a belt is wound around the primary and secondary pulleys, the continuously variable transmission control method comprising:
setting a command base current outputted to a solenoid of the hydraulic pressure control valve, based on a command value of the pulley hydraulic pressure;
acquiring belt-slip-determining information for determining a possibility of occurrence of slip of the belt during control of the pulley hydraulic pressure; and
performing a dither operation in response to a determination based on the belt-slip-determining information that the possibility of occurrence of slip of the belt is high, wherein the dither operation is to superimpose a dither current on the command base current.

8. The continuously variable transmission control method as claimed in claim 7 , comprising:
acquiring a safety factor as the belt-slip-determining information, wherein the safety factor is a ratio of an actual belt thrust to a required belt thrust;
comparing the safety factor with a predetermined value; and
determining the possibility of occurrence of slip of the belt as being high, in response to a determination that the safety factor is less than the predetermined value.

9. The continuously variable transmission control method as claimed in claim 7 , comprising:
acquiring an oil quantity balance lower limit pressure as the belt-slip-determining information during control of the pulley hydraulic pressure, wherein the oil quantity balance lower limit pressure is a lower limit of a secondary pressure that is determined by an oil quantity balance based on a quantity of oil discharged from an oil pump;
comparing an actual value of the secondary pressure with the oil quantity balance lower limit pressure; and
determining the possibility of occurrence of slip of the belt as being high, in response to a determination that the actual value of the secondary pressure is lower than the oil quantity balance lower limit pressure.

Assignees

• Jatco Ltd
• Nissan Motor

Inventors

• Matsui Junki

Classifications

• F16H2061/66277

  by optimising the clamping force exerted on the endless flexible member · CPC title

• F16H61/66259

  using electrical or electronical sensing or control means · CPC title

• F16H2059/683

  Sensing pressure in control systems or in fluid-controlled devices, e.g. by pressure sensors · CPC title

• F16H2059/465

  Detecting slip, e.g. clutch slip ratio · CPC title

• F16H61/02

  characterised by the signals used · CPC title