# US 10,479,351 B2 · Downshift control method for hybrid DCT vehicle

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- Number: US 10,479,351 B2
- Document ID: US10479351B2
- Status: Granted
- Kind: B2
- Application number: 15/985,008
- Filed: 2018-05-21
- Published: 2019-06-13
- Granted: 2019-11-19
- Earliest claimed: 2017-12-13
- Assignees: Hyundai Motor Company; Kia Motors Corporation
- Applicants: Hyundai Motor Company; Kia Motors Corporation
- Inventors: Sung Hyun Cho
- Web page: https://patentgrep.com/patent/US10479351B2

## CPC

- B60W 20/30: Control strategies involving selection of transmission gear ratio {(control of change speed gearings, together with other vehicle sub-units B60W10/10; HEV transmission gearing B60K6/36; gearings and control thereof F16H)}
- B60K 6/387: Actuated clutches, i.e. clutches engaged or disengaged by electric, hydraulic or mechanical actuating means
- B60K 6/48: Parallel type
- B60K 6/547: the transmission being a stepped gearing
- B60W 10/08: including control of electric propulsion units, e.g. motors or generators
- B60W 10/113: with two input flow paths, e.g. double clutch transmission selection of one of the torque flow paths by the corresponding input clutch
- B60W 30/188: Controlling power parameters of the driveline, e.g. determining the required power
- B60W 30/19: Improvement of gear change, e.g. by synchronisation or smoothing gear shift
- F16H 61/0403: {Synchronisation before shifting}
- F16H 61/688: with two inputs, e.g. selection of one of two torque-flow paths by clutches
- B60K 2006/4825: {Electric machine connected or connectable to gearbox input shaft}
- B60W 2510/0208: Clutch engagement state, e.g. engaged or disengaged
- B60W 2510/081: Speed
- B60W 2510/1005: Transmission ratio engaged
- B60W 2510/1015: Input shaft speed, e.g. turbine speed
- B60W 2552/15: Road slope, i.e. the inclination of a road segment in the longitudinal direction
- B60W 2710/021: Clutch engagement state
- B60W 2710/027: Clutch torque
- B60W 2710/083: Torque
- B60W 2710/1005: Transmission ratio engaged
- B60Y 2200/92: Hybrid vehicles
- B60Y 2300/181: Hill climbing or descending
- B60Y 2300/188: Controlling power parameters of the driveline, e.g. determining the required power
- B60Y 2300/19: Improvement of gear change, e.g. synchronisation or smoothing gear shift
- F16H 3/006: {power being selectively transmitted by parallel flow paths, e.g. dual clutch transmissions}
- F16H 2003/0931: {each countershaft having an output gear meshing with a single common gear on the output shaft}
- F16H 2059/663: {Road slope}
- F16H 2061/0422: {by an electric machine, e.g. by accelerating or braking the input shaft}
- Y02T 10/62: Hybrid vehicles
- Y10S 903/914: Actuated, e.g. engaged or disengaged by electrical, hydraulic or mechanical means
- Y10S 903/919: Stepped shift
- Y10S 903/93: Conjoint control of different elements
- B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60K: ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
- F16H: GEARING
- B60Y: INDEXING SCHEME RELATING TO ASPECTS CROSS-CUTTING VEHICLE TECHNOLOGY
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

Disclosed is a downshift control method for a hybrid DCT vehicle. The method includes: determining, by a controller, whether a downshift is desired while a vehicle travels on a slope having equal to or more than a predetermined reference gradient; comparing, by the controller, a motor speed with a desired shift stage input shaft speed, and selectively performing either a forward control step of increasing a motor torque in a forward direction to increase the motor speed in the forward direction or a negative control step of increasing the motor torque in a negative direction to increase the motor speed in the negative direction. Thus, it is possible to reduce the backward sliding of the vehicle by suppressing the motor speed from unnecessarily increasing and rapidly finishing the downshift.

## Claims

### Claim 1

A downshift control method for a dual clutch transmission for a hybrid vehicle, the method comprising the steps of:
determining, by a controller, whether a vehicle travels on a slope having equal to or more than a predetermined reference gradient for a downshift;
releasing, by the controller, a release-side clutch by reducing a torque thereof when the controller determines that the vehicle travels on the slope having equal to or more than the reference gradient;
comparing, by the controller, a motor speed with a desired shift stage input shaft speed when the release of the release-side clutch is completed in the step of releasing the release-side clutch by reducing the torque;
increasing, by the controller, a motor torque in a forward direction when the motor speed is lower than or equal to the desired shift stage input shaft speed in the comparing step;
increasing, by the controller, the motor torque in a negative direction when the motor speed is determined to exceed the desired shift stage input shaft speed in the comparing step;
checking, by the controller, whether the motor speed is synchronized with the desired shift stage input shaft speed in the step of increasing the motor torque in the forward direction or in the step of increasing the motor torque in the negative direction when gear engagement in the desired shift stage is completed; and
completing, by the controller, gear shifting by controlling a torque of an engagement-side clutch and the torque of the release-side clutch when the motor speed is synchronized with the desired shift stage input shaft speed.

### Claim 2 (depends on 1)

The downshift control method according to claim 1, further comprising:
determining, by the controller, whether the vehicle already begins to slide backward when the gear shifting to the desired shift stage is completed by comparing the desired shift stage input shaft speed with a predetermined reference speed while the step of releasing the release-side clutch is performed,
wherein, when the vehicle is determined to already begin to slide backward in the completion of the gear shifting, the comparing step is not performed, and the step of increasing the motor torque in the negative direction to increase the motor speed in the negative direction is performed.

### Claim 3 (depends on 2)

The downshift control method according to claim 2, wherein, in the step of increasing the motor torque in the negative direction, the reduced torque of the release-side clutch is gradually increased until the gear engagement in the desired shift stage is performed.

### Claim 4 (depends on 1)

The downshift control method according to claim 1, wherein, in the step of increasing the motor torque in the forward direction to increase the motor speed in the forward direction, the torque of the released release-side clutch is gradually increased until the gear engagement in the desired shift stage is performed.

### Claim 5 (depends on 1)

The downshift control method according to claim 1, wherein:
when a difference between the motor speed and the desired shift stage input shaft speed is less than a predetermined amount of reference slip in the checking step, the controller determines that the synchronization is completed; and
the controller releases the release-side clutch by reducing the torque thereof and simultaneously engages the engagement-side clutch by increasing the torque thereof, and causes the motor torque to be gradually converged to a desired motor torque so that the gear shifting is completed.