A hybrid vehicle shift control method

Abstract

This invention relates to hybrid vehicle system control technology, specifically to a shift control method for hybrid vehicles. After a shift request is issued, the urgency of the request is calculated, and the priority of shift suppression at that time is also calculated. If the urgency of the shift request is greater than the priority of the shift suppression, the shift is executed; otherwise, suppression is performed. Suppression is executed until the current suppression is resolved, then the system returns to query other shift suppression priorities until the urgency of the shift request is greater than the priority of the shift suppression, at which point the shift is executed. This invention controls the shift timing of multi-engine, multi-axle drive hybrid vehicle systems, ensuring reasonable shift timing control and achieving good coordination between reflecting driving intentions, vehicle driving comfort, and vehicle stability.

Description

Technical Field

[0001] This invention relates to automotive hybrid power system control technology, specifically to a hybrid vehicle shift control method. Background Technology

[0002] The automatic transmission shifting in hybrid electric vehicles differs from that in conventional gasoline vehicles, involving the coordination of multiple power units. Taking a three-motor, four-wheel-drive hybrid electric vehicle powertrain configuration as an example, see... Figure 1 As shown, the transmission is mounted on the drive unit assembly on the front axle, with an electric motor coupled to the engine output. A drive motor is also located on the rear axle for rear-axle drive, thus enabling the entire powertrain to provide independent front-axle drive, independent rear-axle drive, and on-demand four-wheel drive. The transmission controls the input and output power ratio through gear shifting. Although gear shifting itself only occurs on the front axle, it actually requires coordination between the engine and electric motor on the front axle, and the electric motor on the rear axle.

[0003] During automatic transmission gear shifts, it is advisable to avoid transmitting large torques and frequent operation of the shift control mechanism within the shifting time (approximately 300ms-500ms). Energy loss also occurs during gear shifts. Therefore, there is a coordination relationship between shift requests and appropriate shift suppression. After the control system outputs the shift target based on the driver's intention and vehicle operating conditions, it considers other potential vehicle function control requirements and confirms that there are no conflicts with these requirements before the shift control mechanism executes the shift.

[0004] Chinese patent CN114426015B describes a situation where, for example, shortly after a gear shift has occurred, the driver's setting of a power style switch might cause the system to calculate a new gear shift target. If the system responds according to driving needs, frequent gear shifts may occur in the short term, causing driving comfort issues. To address driving comfort control requirements, a reasonable gear shift suppression scheme is designed to optimize this problem. Beyond this reason, when ESP controls driving or braking forces to maintain vehicle stability, gear shifts should also be suppressed during ESP response to prioritize vehicle stability. Furthermore, when changing between front-wheel drive, rear-wheel drive, and four-wheel drive, there is a redistribution of driving or braking forces between the front and rear axles. The driving forces of the front and rear axles change rapidly in a short time to transition to the corresponding driving state. If gear shifts occur during this time, it may cause inaccurate coordination control torque, transmission oscillations during torque transition, and impact damage to transmission components; therefore, gear shift suppression is also necessary.

[0005] Due to the complexity of the vehicle's powertrain structure, there is a certain need to coordinate the control of gear shifting timing. How to achieve good coordination between vehicle control and driving comfort and vehicle stability is the technical problem that this invention aims to solve. Summary of the Invention

[0006] This invention provides a method for shift control in a hybrid electric vehicle.

[0007] Hybrid vehicles trigger shift requests for various reasons, such as accelerator pedal engagement / disengagement, power unit coupling status, energy optimization, switching between two-wheel drive and four-wheel drive modes, and the need to switch driving styles (e.g., aggressive sporty driving versus a more moderate, fuel-efficient driving style). In the vehicle's control system, to reflect the driver's acceleration and deceleration intentions, multiple upshift and downshift curves are preset based on the vehicle's operating status and its own information. Generally, due to the complexity of hybrid vehicle operating modes, different shift curves are formed by combining elements such as whether the engine is running, whether there is remaining battery power, whether the vehicle is in front-wheel drive / rear-wheel drive / four-wheel drive mode, and the vehicle's power output style. During driving, the vehicle control system searches for the preset shift curves based on the above information and outputs upshift or downshift requests according to changes in operating conditions.

[0008] Most hybrid vehicles currently use automatic transmissions, and their control systems can automatically calculate shift commands. Due to the driver's active throttle control, four-wheel drive and two-wheel drive settings, and the switching of the vehicle's power output style, the system's gear target will switch. Changes in vehicle operating conditions, such as changes in vehicle speed and battery SOC (state of charge), will also require adjustments to the output ratio of the electric drive and internal combustion engine, thus resulting in gear changes.

[0009] A shift request is urgent under some conditions, but not so urgent under others. For example, when the load is high, the vehicle speed is low, and acceleration is rapid with heavy throttle, downshifting to increase torque is a more urgent shift demand. Conversely, when the vehicle speed is high, the load is low, and acceleration is slow with light throttle, the need to upshift is less urgent. Therefore, the urgency of a shift can be determined by comprehensively considering factors such as load level, remaining driving force, acceleration intention, and vehicle speed.

[0010] Shift suppression has different priorities depending on the situation. Generally speaking, ESP suppresses shifts differently depending on the amount of torque applied to the drive shaft, and shift suppression is triggered by changes in driving style.

[0011] The specific solution of the present invention is as follows:

[0012] After a shift request is issued, the urgency of the shift request is calculated, and the priority of the shift suppression at this time is calculated. If the urgency of the shift is greater than the priority of the shift suppression, the shift is executed; otherwise, the suppression is executed. After the suppression is executed until the current suppression is released, the system returns to query the priority of other shift suppressions until the urgency of the shift is greater than the priority of the shift suppression, at which point the shift is executed.

[0013] The urgency of the shift request is calculated as follows:

[0014] When the load gradient is greater than 10%, the throttle opening is greater than 50%, and the vehicle speed is less than 20 km / h, the urgency of the downshift request is 3.

[0015] Aside from the situation where the urgency is 3, during acceleration, when the throttle opening is ≥50%, the shift request is issued according to the shift curve. During deceleration, when the engine uses its own resistance to participate in braking and the hill descent control function is activated, the shift request is issued according to the shift curve. At this time, the urgency of the shift request is 2.

[0016] Aside from cases where the urgency is 3 or 2, during acceleration, coasting, and deceleration, the urgency of the shift request issued based on the shift curve is 1.

[0017] The priority of shift suppression is calculated as follows:

[0018] The shift suppression priority issued by the Electronic Stability Program (ESP) is 3;

[0019] When the vehicle switches between front-wheel drive, rear-wheel drive, and dual-axle co-drive modes, the priority of suppressing gear shifts is 2.

[0020] When driving style changes, the priority of suppressing gear shifts is 1;

[0021] If there is no suppression priority of 1, 2 or 3, then the priority of shift suppression is 0.

[0022] This invention controls the shift timing of multi-engine, multi-axle hybrid vehicle systems, making the shift timing reasonable and achieving good coordination between reflecting driving intention, vehicle driving comfort, and vehicle driving stability. Attached Figure Description

[0023] Figure 1 , Powertrain configuration structure diagram of hybrid vehicle system.

[0024] Figure 2 , Schematic diagram of gear shift control process. Detailed Implementation

[0025] This invention provides a shift control method for hybrid electric vehicles, the scheme of which is as follows: Figure 2 As shown, the details are as follows:

[0026] After a shift request is issued, the urgency of the shift request is calculated, and the priority of the shift suppression at this time is calculated. If the urgency of the shift is greater than the priority of the shift suppression, the shift is executed; otherwise, the suppression is executed. After the suppression is executed until the current suppression is released, the system returns to query the priority of other shift suppressions until the urgency of the shift is greater than the priority of the shift suppression, at which point the shift is executed.

[0027] The shift request is triggered by the vehicle control system's shift curve based on vehicle speed and acceleration request. The shift curve type of hybrid vehicles is relatively complex and can be formed by arranging and combining elements from the following types: power combination type (pure engine drive, pure electric drive, hybrid drive), front and rear axle drive status (front axle drive, rear axle drive, and both axles drive), and driving style (aggressive sporty style, economy style).

[0028] When a vehicle is being operated, the urgency of gear shifting varies depending on its own power output, driving intention, and driving environment. This invention calculates the urgency of gear shifting based on load gradient, remaining driving force, acceleration intention, and vehicle speed. The calculation scheme is as follows:

[0029] When the load gradient is greater than 10%, the throttle opening is greater than 50%, and the vehicle speed is less than 20 km / h, the urgency of the downshift request is 3.

[0030] Aside from the situation where the urgency is 3, during acceleration, when the throttle opening is ≥50%, the shift request is issued according to the shift curve. During deceleration, when the engine uses its own resistance to participate in braking and the hill descent control function is activated, the shift request is issued according to the shift curve. At this time, the urgency of the shift request is 2.

[0031] Aside from cases where the urgency is 3 or 2, during acceleration, coasting, and deceleration, the urgency of the shift request issued based on the shift curve is 1.

[0032] The priority calculation method for shift suppression is as follows:

[0033] The shift suppression priority is 3: The ESP system issues a short-term shift suppression request; the need for ESP is prioritized, and shifting is temporarily suppressed.

[0034] Shift suppression priority 2: Suppress shift requests when the vehicle switches from front-wheel drive, rear-wheel drive, or dual-axle co-drive. At this time, there is a rapid torque redistribution process in the distribution of driving force or braking force between the front and rear axles. When the torque of the front axle is rapidly loaded or unloaded, a temporary shift suppression will be requested.

[0035] Shift suppression priority 1: Suppressing frequent shift requests caused by changes in driving style. For example, at a vehicle speed of 45 km / h, the target gear for an aggressive sport shifting style is 4th gear, but the target gear for an economy shifting style is 5th gear. If the current mode is switched from economy to sport shifting style, without proper suppression, the gear will jump from 5th to 4th gear. Under rapid acceleration, it will quickly return to 5th gear, resulting in frequent shifts between 5th and 4th gears in a short period of time. This can easily cause inconsistent acceleration, a jerky and uncomfortable feeling, and also increase the loss of transmission energy in the system.

[0036] When there is no suppression, the shift suppression priority is 0;

[0037] This invention calculates the urgency of gear shift requests based on load, remaining driving force, acceleration intention, and vehicle speed. Priority calculations are performed for gear shift suppression. Then, based on the comparison calculation results, a comprehensive coordination is achieved between gear shift requests and short-term gear shift suppression. This invention is applicable to complex hybrid power structures and handling functions, and is suitable for a wider range of operating conditions.

Claims

1. A method for shifting control in a hybrid electric vehicle, characterized in that: After a shift request is issued, the urgency of the shift request is calculated, and the priority of the shift suppression at this time is also calculated. If the urgency of the shift is greater than the priority of the shift suppression, the shift is executed; otherwise, the suppression is executed. After the suppression is executed until the current suppression is released, the system returns to query the priority of other shift suppressions until the urgency of the shift is greater than the priority of the shift suppression, at which point the shift is executed. The urgency of the shift request is calculated as follows: When the load gradient is greater than 10%, the throttle opening is greater than 50%, and the vehicle speed is less than 20 km / h, the urgency of the downshift request is 3. Aside from the situation where the urgency is 3, during acceleration, when the throttle opening is ≥50%, the shift request is issued according to the shift curve. During deceleration, when the engine uses its own resistance to participate in braking and the hill descent control function is activated, the shift request is issued according to the shift curve. At this time, the urgency of the shift request is 2. Aside from cases where the urgency is 3 or 2, during acceleration, coasting, and deceleration, the urgency of the shift request issued based on the shift curve is 1. The priority of shift suppression is calculated as follows: The shift suppression priority issued by the Electronic Stability Program (ESP) is 3; When the vehicle switches between front-wheel drive, rear-wheel drive, and dual-axle co-drive modes, the priority of suppressing gear shifts is 2. When driving style changes, the priority of suppressing gear shifts is 1; If there is no suppression priority of 1, 2 or 3, then the priority of shift suppression is 0.

2. The hybrid electric vehicle shift control method according to claim 1, characterized in that: The shift request is triggered by the vehicle control system's shift curve based on vehicle speed and acceleration request.

3. The hybrid electric vehicle shift control method according to claim 2, characterized in that: The shift curves are formed by arranging and combining elements from the powertrain type, the drive status of the front and rear axles, and the driving style to create multiple preset upshift and downshift curves.

4. The hybrid electric vehicle shift control method according to claim 3, characterized in that: The powertrain combination type includes pure engine drive, pure electric drive, or hybrid drive; the drive state of the front and rear axles includes front axle drive, rear axle drive, or both axles drive; and the driving style includes sport style or economy style.

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