Method and system for shifting a gear of a hybrid electric vehicle

• US 9,701,303 B2
• Filed: 06/18/2015
• Issued: 07/11/2017
• Est. Priority Date: 06/18/2014
• Status: Active Grant

• Current Assignee: Beiqi Foton Motor Company Limited
• Original Assignee: Beiqi Foton Motor Company Limited
• Inventors: Yang, Weibin
• Primary Examiner(s): Smith, Jelani
• Assistant Examiner(s): Martinez Borrero, Luis A
• Application Number:
  US14/743,639
• Publication Number:
  US 20150367840A1
• Time in Patent Office: 754 Days
• Field of Search: 701 22, 701 54, 701 51, 701 55, 701 53, 701 52, 701 28, 701110, 701113, 701 49, 701 56, 701 67, 701123, 701 36, 701100, 701118, 701 21, 701533, 701102, 701 3, 701 18, 701124, 180 65265, 180 65235, 180 65275, 903945, 903947, 903902, 903910, 903918
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 20/13 in order to stay within battery power input or output limits; in order to prevent overcharging or battery depletion
• CPC Class Codes: 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
• CPC Class Codes: B60W 20/40 Controlling the engagement or disengagement of prime movers, e.g. for transition between prime movers power-up or power-down of the driveline B60W30/192
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/0657 Engine torque
• CPC Class Codes: B60W 2510/083 Torque
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2710/0644 Engine speed
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: B60W 2710/1005 Transmission ratio engaged
• CPC Class Codes: B60W 30/1882 characterised by the working point of the engine, e.g. by using engine output chart
• CPC Class Codes: F16H 2059/148 Transmission output torque, e.g. measured or estimated torque at output drive shaft
• CPC Class Codes: F16H 2059/366 : Engine or motor speed
• CPC Class Codes: F16H 2059/6815 : Post shift value of gearing, i.e. calculated or estimated parameters after shift is completed, e.g. estimated output torque after shift is performed
• CPC Class Codes: F16H 2061/0015 : Transmission control for optimising fuel consumptions
• CPC Class Codes: F16H 59/44 : dependent on machine speed of the machine, e.g. the vehicle
• CPC Class Codes: F16H 59/70 : dependent on the ratio established
• CPC Class Codes: F16H 61/0213 : characterised by the method for generating shift signals
• CPC Class Codes: Y02T 10/40 : Engine management systems
• CPC Class Codes: Y02T 10/60 : Other road transportation technologies with climate change mitigation effect
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/84 : Data processing systems or methods, management, administration
• CPC Class Codes: Y10S 903/93 : Conjoint control of different elements
• CPC Class Codes: Y10S 903/945 : Characterized by control of gearing, e.g. control of transmission ratio

Abstract

A method and a system for shifting a gear of a hybrid electric vehicle are provided. The method includes following steps. A state of a battery is determined according to a remaining capacity of the battery, a required torque and a state of the hybrid electric vehicle, in which the state of the battery comprises a discharging state or a charging state. A plurality of optional target gears, a torque and a rotating speed of an engine corresponding to each optional target gear are determined according to the state of the battery and a speed of the hybrid electric vehicle. An optional target gear with a minimum fuel consumption of the engine is selected as a target gear from the plurality of optional target gears. It is determined whether to perform a gear shift by comparing with a current gear.

Claims

1. A method for shifting a gear of a hybrid electric vehicle, comprising the following acts performed by a gear shifting system of the vehicle:

determining a remaining capacity of a battery relative to a first threshold and a second threshold, wherein the second threshold is less than the first threshold;

determining a state of the battery based on the remaining capacity, wherein;

the battery is determined to be in a discharging state if the remaining capacity of the battery is larger than the first threshold;

the battery is determined to be in a charging state if the remaining capacity of the battery is less than the second threshold; and

if the remaining capacity of the battery is between the first threshold and the second threshold;

further determining whether a required torque is larger than a predetermined threshold;

determining the battery is in the discharging state, if the required torque is larger than the predetermined threshold; and

keeping the battery in a previous state, if the required torque is less than or equal to the predetermined threshold;

determining the battery is in the discharging state without considering the remaining capacity of the battery, if the hybrid electric vehicle has just been started;

determining a plurality of optional target gears and a torque and a rotating speed of an engine corresponding to each optional target gear according to the state of the battery and a speed of the hybrid electric vehicle;

selecting an optional target gear with a minimum fuel consumption of the engine as a target gear from the plurality of optional target gears; and

comparing the selected optional target gear with a current gear and performing a gear shift as based on the comparison.

2. The method according to claim 1, wherein determining a plurality of optional target gears and a torque and a rotating speed of an engine corresponding to each optional target gear according to the state of the battery and a speed of the hybrid electric vehicle comprises:

determining whether the engine is in an idling state;

judging whether the speed of the hybrid electric vehicle is larger than a minimum speed, if the engine is in the idling state;

determining a starting gear as the optional target gear, if the speed of the hybrid electric vehicle is less than or equal to the minimum speed;

determining a plurality of available gears corresponding to the speed of the hybrid electric vehicle according to a predetermined maximum rotating speed and a predetermined minimum rotating speed of the engine, if the speed of the hybrid electric vehicle is larger than the minimum speed, and obtaining the plurality of optional target gears from the plurality of available gears and the torque and the rotating speed of the engine corresponding to each optional target gear according to the state of the battery.

3. The method according to claim 2, wherein when the battery is in the discharging state, a motor of the hybrid electric vehicle works in a power assistance mode, and obtaining the plurality of optional target gears from the plurality of available gears and the torque and the rotating speed of the engine corresponding to each optional target gear according to the state of the battery comprises:

determining a minimum assisted torque and a maximum assisted torque of the motor;

determining an output torque of the engine corresponding to each available gear under the speed of the hybrid electric vehicle;

judging whether one or more gears exist such that the required torque is satisfied when the engine outputs the output torque and an assisted torque of the motor is between the minimum assisted torque and the maximum assisted torque;

if yes, determining the one or more gears as the plurality of optional target gears and obtaining the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, determining whether one or more gears exist such that the required torque is satisfied just by the engine;

if yes, determining the one or more gears as the plurality of optional target gears and obtaining the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, determining whether one or more gears exist such that the required torque is satisfied when the motor outputs the maximum assisted torque and the engine provides the rest torque;

if yes, determining the one or more gears as the plurality of optional target gears and obtaining the torque and the rotating speed of the engine corresponding to each optional target gear.

4. The method according to claim 2, wherein when the battery is in the charging state, a motor works in a power generation mode, and obtaining the plurality of optional target gears from the plurality of available gears and the torque and the rotating speed of the engine corresponding to each optional target gear according to the state of the battery comprises:

determining a minimum power generating torque and a maximum power generating torque of the motor;

determining an output torque of the engine corresponding to each available gear under the speed of the hybrid electric vehicle;

judging whether one or more gears exist such that the required torque is satisfied when the engine outputs the output torque and a power generating torque of the motor is between the minimum power generating torque and the maximum power generating torque;

if yes, determining the one or more gears as the plurality of optional target gears and obtaining the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, determining whether one or more gears exist such that a sum of the maximum power generating torque of the motor and the required torque is satisfied by the output torque of the engine;

if yes, determining the one or more gears as the plurality of optional target gears and obtaining the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, obtaining a corresponding gear as the optional target gear when only the engine works and obtaining the torque and the rotating speed of the engine corresponding to each optional target gear.

5. The method according to claim 1, wherein selecting an optional target gear with a minimum fuel consumption of the engine as a target gear from the plurality of optional target gears comprises:

determining a fuel consumption of the engine in each optional target gear according to the torque and the rotating speed of the engine corresponding to each optional target gear and by using a universal characteristic of the engine; and

selecting the optional target gear with the minimum fuel consumption of the engine as the target gear.

6. The method according to claim 1, wherein determining whether to perform a gear shift by comparing with a current gear comprises:

determining whether a time interval between a previous gear shift and the gear shift to be performed is larger than a threshold;

if yes, performing the gear shift according to the target gear; and

if not, keeping the hybrid electric vehicle in the current gear.

7. A system for shifting a gear of a hybrid electric vehicle, comprising:

a non-transitory computer-readable medium comprising computer-executable instructions stored thereon; and

an instruction execution system, which is configured by the instructions to implement acts of;

determining a remaining capacity of a battery relative to a first threshold and a second threshold, wherein the second threshold is less than the first threshold;

determining a state of the battery based on the remaining capacity, wherein;

the battery is determined to be in a discharging state if the remaining capacity of the battery is larger than the first threshold;

the battery is determined to be in a charging state if the remaining capacity of the battery is less than the second threshold; and

if the remaining capacity of the battery is between the first threshold and the second threshold;

further determining whether a required torque is larger than a predetermined threshold;

determining the battery is in the discharging state, if the required torque is larger than the predetermined threshold; and

keeping the battery in a previous state, if the required torque is less than or equal to the predetermined threshold;

determining the battery is in the discharging state without considering the remaining capacity of the battery, if the hybrid electric vehicle has just been started;

determining a plurality of optional target gears and a torque and a rotating speed of an engine corresponding to each optional target gear according to the state of the battery and a speed of the hybrid electric vehicle;

selecting an optional target gear with a minimum fuel consumption of the engine as a target gear from the plurality of optional target gears; and

comparing the selected optional target gear with a current gear and performing a gear shift based on the comparison.

8. The system according to claim 7, wherein the instruction execution system is configured to implement the act of determining a plurality of optional target gears and a torque and a rotating speed of an engine corresponding to each optional target gear according to the state of the battery and a speed of the hybrid electric vehicle by acts of:

determining whether the engine is in an idling state;

judging whether the speed of the hybrid electric vehicle is larger than a minimum speed, if the engine is in the idling state;

determining a starting gear as the optional target gear, if the speed of the hybrid electric vehicle is less than or equal to the minimum speed;

determining a plurality of available gears corresponding to the speed of the hybrid electric vehicle according to a predetermined maximum rotating speed and a predetermined minimum rotating speed of the engine, if the speed of the hybrid electric vehicle is larger than the minimum speed, and obtaining the plurality of optional target gears from the plurality of available gears and the torque and the rotating speed of the engine corresponding to each optional target gear according to the state of the battery.

9. The system according to claim 8, wherein when the battery is in the discharging state, a motor of the hybrid electric vehicle works in a power assistance mode and the instruction execution system is configured to implement the act of obtaining the plurality of optional target gears from the plurality of available gears and the torque and the rotating speed of the engine corresponding to each optional target gear according to the state of the battery by acts of:

determining a minimum assisted torque and a maximum assisted torque of the motor;

determining an output torque of the engine corresponding to each available gear under the speed of the hybrid electric vehicle;

judging whether one or more gears exist such that the required torque is satisfied when the engine outputs the output torque and an assisted torque of the motor is between the minimum assisted torque and the maximum assisted torque;

if yes, determining the one or more gears as the plurality of optional target gears and obtain the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, determining whether one or more gears exist such that the requires torque is satisfied just by the engine;

if yes, determining the one or more gears as the plurality of optional target gears and obtain the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, determining whether one or more gears exist such that the required torque is satisfied when the motor outputs the maximum assisted torque and the engine provides the rest torque;

if yes, determining the one or more gears as the plurality of optional target gears and obtain the torque and the rotating speed of the engine corresponding to each optional target gear.

10. The system according to claim 8, wherein when the battery is in the charging state, a motor works in a power generation mode and the instruction execution system is configured to implement the act of obtaining the plurality of optional target gears from the plurality of available gears and the torque and the rotating speed of the engine corresponding to each optional target gear according to the state of the battery by acts of:

determining a minimum power generating torque and a maximum power generating torque of the motor;

determining an output torque of the engine corresponding to each available gear under the speed of the hybrid electric vehicle;

judging whether one or more gears exist such that the required torque is satisfied when the engine outputs the output torque and a power generating torque of the motor is between the minimum power generating torque and the maximum power generating torque;

if yes, determining the one or more gears as the plurality of optional target gears and obtain the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, determining whether one or more gears exist such that a sum of the maximum power generating torque of the motor and the required torque is satisfied by the output torque of the engine;

if yes, determining the one or more gears as the plurality of optional target gears and obtain the torque and the rotating speed of the engine corresponding to each optional target gear;

if not, obtaining a corresponding gear as the optional target gear when only the engine operates and obtain the torque and the rotating speed of the engine corresponding to each optional target gear.

11. The system according to claim 7, wherein the instruction execution system is configured to implement the act of selecting an optional target gear with a minimum fuel consumption of the engine as a target gear from the plurality of optional target gears by acts of:

determining a fuel consumption of the engine in each optional target gear according to the torque and the rotating speed of the engine corresponding to each optional target gear and by using a universal characteristic of the engine; and

selecting the optional target gear with the minimum fuel consumption of the engine as the target gear.

12. The system according to claim 7, wherein the instruction execution system is configured to implement the act of comparing the selected optional target gear with a current gear and performing a gear shift based on the comparison by acts of:

determining whether a time interval between a previous gear shift and the gear shift to be performed is larger than a threshold;

if yes, performing the gear shift according to the target gear; and

if not, keeping the hybrid electric vehicle in the current gear.