Gear shifting control method for hybrid electric vehicle

Abstract

The invention relates to an automobile hybrid power system control technology, in particular to a hybrid power automobile gear shifting control method. After the gear shifting request is sent out, the urgency of the gear shifting request is calculated, and the priority of gear shifting suppression at the moment is calculated; executing gear shifting when the gear shifting urgency is greater than the priority of gear shifting suppression, otherwise, executing suppression; and after the suppression is executed until the current suppression is relieved, returning to query other gear shifting suppression priorities, and executing gear shifting until the gear shifting urgency is greater than the gear shifting suppression priorities. According to the method, the gear shifting opportunity of the multi-engine and multi-shaft driving hybrid electric vehicle system is controlled, so that the gear shifting opportunity is reasonably controlled, and good coordination is achieved among reflecting the driving intention, comfortable vehicle driving and stable vehicle running.

Description

Technical Field

[0001] The present invention relates to the control technology of automotive hybrid power systems, and specifically to a shift control method for hybrid vehicles. Background Art

[0002] The automatic transmission shifting of hybrid vehicles is different from that of ordinary fuel vehicles, and it involves the coordination of multiple power units. Taking the power configuration structure of a three-motor four-wheel-drive hybrid vehicle as an example, as shown in Figure 1 shown, the transmission is set on the drive unit assembly of the front axle, and a motor is coupled to the engine output end. There is also a drive motor on the rear axle to achieve rear axle drive. In this way, the entire power system can achieve front axle independent drive, rear axle independent drive, and timely four-wheel drive. The transmission controls the power ratio of input and output through shifting. Although the shifting itself only occurs on the front axle, in fact, the working states of the engine, motor on the front axle, and the motor on the rear axle all need to be coordinated.

[0003] During the shifting operation of the automatic transmission (about 300ms - 500ms), it is not suitable to transmit a large torque, and the shifting mechanism should not operate frequently. Energy loss will also occur during transmission during shifting. Therefore, there is a coordination relationship between the shift request and the reasonable suppression of shifting. When the control system outputs a shift target according to the driving control intention and vehicle working condition requirements, considering the possible other functional control requirements of the vehicle, it is necessary to confirm that there is no conflict with other functional requirements before the shift mechanism performs the shift.

[0004] Chinese Patent CN114426015B illustrates a situation. For example, within a short period after the system has shifted gears, if the driver sets a power style switch, it may cause the system to calculate a new shift target. If the driving demand is responded to, frequent shifting may occur in the short term, which will also cause problems with driving comfort. For the driving comfort control requirements, a reasonable shift suppression scheme is designed to optimize this problem. Not only for this reason, in fact, when the ESP controls the driving force or braking force to maintain vehicle body stability, in order to give priority to the vehicle body stability requirements, shifting should also be suppressed when the ESP responds. Also, when changing between driving modes such as front-wheel drive, rear-wheel drive, and four-wheel drive, there is a problem of re-distributing the driving force or braking force between the front and rear drive axles. The driving force of the front and rear axles changes rapidly in a short time to transition to the corresponding driving state. If shifting occurs at this time, it may also cause problems such as inaccurate coordinated control torque, transmission oscillation during the torque transition period, and impact damage to transmission components. Therefore, there is also a shift suppression.

[0005] Due to the complexity of the vehicle power system structure, there are certain coordination requirements for the control of the shift timing. How to achieve good coordination among reflecting the driving intention, vehicle driving comfort, and vehicle driving stability in vehicle control is the technical problem to be solved by the present invention. Summary of the Invention

[0006] The present invention provides a shift control method for a hybrid vehicle.

[0007] There are many reasons for a hybrid vehicle to trigger a shift request, such as the opening degree of the accelerator pedal, the coupling state of the power unit, energy optimization, the jump between two-wheel drive and four-wheel drive forms, and the vehicle driving style switching requirements (for example, an aggressive sports style and a relatively mild economic style). In the vehicle control system, in order to reflect the driver's intention of accelerating and decelerating, multiple upshift curves and downshift curves are preset based on the vehicle working state and its own information. Generally speaking, due to the complexity of the hybrid vehicle working mode, different shift curves will be formed by combining elements such as whether the engine is started, whether the battery power is surplus, the vehicle is in front-wheel drive / rear-wheel drive / four-wheel drive, and the vehicle power output style. During the driving operation, the vehicle control system searches for the set shift curves according to the above element information and outputs a request for upshifting or downshifting according to the change of working conditions.

[0008] Currently, most hybrid vehicles are automatic transmission vehicles, and the control system can automatically calculate shift commands. Due to the driver's active throttle control, four-wheel drive and two-wheel drive settings, and the vehicle power output style switching, the system gear target will switch. Also, due to vehicle working condition changes, such as vehicle speed changes and battery SOC (remaining battery power) changes, the output ratio of the system's electric drive and internal combustion engine drive needs to be adjusted, resulting in gear changes.

[0009] The shift request command is urgent under some conditions, and it may not need to be executed urgently under some conditions. For example, when the load is high, the vehicle speed is low, and the vehicle accelerates with a large throttle, downshifting to increase torque is a relatively urgent shift requirement. When the vehicle speed is high, the load is low, and the vehicle accelerates with a light throttle to upshift, the upshift requirement is less urgent than the former. Therefore, the urgency of shifting can be comprehensively determined by the load degree, remaining driving force, acceleration willingness, and vehicle speed.

[0010] There are also different levels of priorities for shift inhibition in different situations. Generally speaking, the priorities of ESP for shift inhibition, drive shaft torque transition for shift inhibition, and driving style switching for shift inhibition are also different.

[0011] The solution of the present invention is as follows: After a shift request is issued, calculate the urgency of the shift request and calculate the priority of the current shift inhibition; when the shift urgency is greater than the priority of the shift inhibition, perform the shift, otherwise perform the inhibition; after performing the inhibition until the current inhibition is released, return to query the priority of other shift inhibitions until the shift urgency is greater than the priority of the shift inhibition and then perform the shift.

[0012] The urgency of the shift request is calculated as follows: The load gradient is greater than 10%, the throttle opening is ≥ 50%, and the vehicle speed is < 20 km / h. At this time, the urgency of the downshift request is 3; Except for the situation with an urgency of 3, during acceleration, when the throttle opening is ≥ 50%, the upshift / downshift request sent according to the shift curve, and during deceleration, when the engine participates in braking using its own resistance and the hill descent control function is activated, the upshift / downshift request sent according to the shift curve. At this time, the urgency of the shift request is 2; Except for the cases with an urgency of 3 or 2, during acceleration, coasting, and deceleration, the upshift / downshift request sent according to the shift curve. At this time, the urgency of the shift request is 1.

[0013] The priority of shift inhibition is calculated as follows: The priority of shift inhibition issued by the Electronic Stability Program (ESP) of the vehicle body is 3; When the vehicle switches between front-wheel drive, rear-wheel drive, and dual-axis co-drive modes, the priority of inhibiting shifts is 2; When the driving style changes, the priority of inhibiting shifts is 1; When there is no shift inhibition priority of 1, 2, or 3, the priority of shift inhibition is 0.

[0014] The present invention controls the shift timing of a hybrid vehicle system with multiple engines and multiple-axis drive, making the shift timing control reasonable and achieving good coordination among reflecting the driving intention, vehicle driving comfort, and vehicle driving stability. Brief Description of the Drawings

[0015] Figure 1 , Structural diagram of the power configuration of the hybrid system vehicle.

[0016] Figure 2 , Schematic diagram of the shift control flow. Detailed Embodiment

[0017] The present invention provides a shift control method for a hybrid vehicle. The solution is as Figure 2 shown, specifically as follows: After a shift request is issued, calculate the urgency of the shift request and calculate the priority of shift inhibition at this time; when the shift urgency is greater than the priority of shift inhibition, perform the shift, otherwise perform inhibition; after performing inhibition until the current inhibition is lifted, return to query other shift inhibition priorities until the shift urgency is greater than the priority of shift inhibition and then perform the shift.

[0018] The shift request is triggered by the shift curve of the vehicle control system based on the vehicle speed and the acceleration request. The shift curve types of hybrid vehicles are relatively complex and can be formed by arranging and combining elements from these types: power combination types (pure engine drive, pure electric drive, hybrid drive), drive states of the front and rear axles (front axle drive, rear axle drive, front and rear axles jointly drive), and driving styles (aggressive sports style, economy style) to form multiple upshift and downshift preset curves.

[0019] When the vehicle is being controlled, due to different requirements for shift urgency regarding its own power output, driving intention, and driving environment, the present invention calculates the shift urgency based on the load gradient, remaining driving force, acceleration intention, and vehicle speed. The calculation scheme is as follows: When the load gradient is greater than 10%, the throttle opening ≥ 50%, and the vehicle speed < 20 km / h, the urgency of the downshift request at this time is 3; Except for the situation with an urgency of 3, during acceleration, when the throttle opening ≥ 50%, for the upshift and downshift requests issued according to the shift curve, and during deceleration, when the engine uses its own resistance to participate in braking and the hill descent control function is activated, for the upshift and downshift requests issued according to the shift curve, the urgency of the shift request at this time is 2; Except for the cases with an urgency of 3 or 2, during acceleration, coasting, and deceleration, for the upshift and downshift requests issued according to the shift curve, the urgency of the shift request at this time is 1.

[0020] The calculation method for the priority of shift inhibition is as follows: The shift inhibition priority is 3: The Electronic Stability Program (ESP) system of the vehicle body stability control issues a short-term shift inhibition request; due to the need for priority vehicle body stability control, the shift is temporarily inhibited.

[0021] The shift inhibition priority is 2: When the vehicle switches between front-wheel drive, rear-wheel drive, and dual-axis co-drive, the shift request is inhibited; at this time, there is a rapid torque redistribution process in the driving force or braking force distribution of the front and rear axles. When the torque of the front axle is rapidly loaded or unloaded, a temporary shift inhibition is requested.

[0022] The shift inhibition priority is 1: Frequent shift inhibitions may be caused by changes in the driving style leading to shift requests. For example, when the vehicle speed is 45 km / h, the gear target for the aggressive sports shift style corresponds to the 4th gear, but the gear target for the economy shift style corresponds to the 5th gear. If the current mode switches from the economy shift style to the sports shift style, without reasonable inhibition, the gear will jump from the 5th gear to the 4th gear. Under relatively fast acceleration, it will quickly enter the 5th gear subsequently, thus forming frequent shifts between the 5th gear, 4th gear, and 5th gear in a short period, which is likely to cause discontinuous acceleration, a jerky and uncomfortable feeling, and also increase the energy loss of the system transmission.

[0023] When there is no inhibition, the shift inhibition priority is 0; The method of the present invention calculates the urgency of gear shifting for a gear shifting request based on load, remaining driving force, acceleration intention, and vehicle speed. It calculates the priority for gear shifting inhibition. Then, based on the comparison calculation results, it comprehensively coordinates between the gear shifting request and short-term gear shifting inhibition. The method of the present invention is applicable to complex hybrid structures and control functions and is suitable for more variable working conditions.

Claims

1. A hybrid electric vehicle shift control method, characterized in that: After a gear shift request is issued, the urgency of the gear shift request is calculated, and the priority of the gear shift inhibition at this time is calculated; when the gear shift urgency is greater than the gear shift inhibition priority, the gear shift is executed, otherwise the inhibition is executed; after the inhibition is executed until the current inhibition is released, return to query other gear shift inhibition priorities until the gear shift urgency is greater than the gear shift inhibition priority, and the gear shift is executed.

2. The hybrid vehicle shift control method according to claim 1, characterized in that: The urgency of a shift request is calculated as follows: When the load gradient is greater than 10%, the throttle opening is ≥50%, and the vehicle speed is <20 km / h, the urgency of the downshift request is 3; Except for the case where the urgency is 3, during acceleration, when the throttle opening is ≥50%, the upshift and downshift requests are issued according to the gear shift curve; during deceleration, when the engine uses its own resistance to participate in braking and the steep slope descent function is activated, the upshift and downshift requests are issued according to the gear shift curve. The urgency of the gear shift request at this time is 2; Except for the case where the urgency is 3 or 2, during acceleration, coasting, or deceleration, an upshift or downshift request is issued according to the shift curve, and the urgency of the shift request at this time is 1.

3. The hybrid vehicle shift control method according to claim 1, characterized in that: The priority of shift inhibition is calculated as follows: The gear shift inhibition priority issued by the ESP system is 3; When the vehicle switches between front-wheel drive, rear-wheel drive, and dual-axle co-drive modes, the priority of inhibiting gear shifting is 2; When the driving style changes, the priority of suppressing gear shifting is 1; If there is no inhibition priority of 1, 2 or 3, the priority of the shift inhibition is 0.

4. The hybrid vehicle shift control method according to claim 1, characterized in that: The shift request is triggered by the shift profile of the vehicle control system based on vehicle speed and acceleration request.

5. The hybrid vehicle shift control method according to claim 4, characterized in that: The shift curve type is formed by arranging and combining elements of the power combination type, the driving state of the front and rear axles, and the driving style to form a plurality of upshift and downshift preset curves.

6. The hybrid vehicle shift control method according to claim 5, characterized in that: The power combination type includes pure engine drive, pure electric drive or hybrid drive, the driving state of the front and rear axles includes front axle drive, rear axle drive or front and rear axle common drive, and the driving style includes sports style or economical style.

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