A braking energy recovery method for a heavy-duty hybrid commercial vehicle

Abstract

The present invention discloses a braking energy recovery method for a heavy-duty hybrid commercial vehicle, which calculates the recovery torque of the motor and the braking torque of the mechanical brake in real time according to the current vehicle speed and the brake pedal depth value; when the motor speed is lower than the base speed, the hybrid controller sends a downshift request to the gearbox; the gearbox completes the downshift action, and the motor continues to output the recovery torque; the motor speed increases after the downshift and is greater than the base speed again, at which time the motor will recover the kinetic energy of the whole vehicle at maximum power; if the motor speed drops below the base speed again, the hybrid system will repeat the above-mentioned downshift process. The present invention improves the existing braking energy recovery strategy by controlling the gearbox to downshift during the recovery process to maximize the motor recovery power, thereby improving the degree of recovery of the whole vehicle kinetic energy. After analyzing the measured data, the vehicle using the braking energy recovery method proposed by the present invention can recover more energy than the vehicle using the original strategy.

Description

Technical Field

[0001] The present invention relates to the field of energy recovery of hybrid vehicles, and in particular to a braking energy recovery method for a heavy-loaded hybrid commercial vehicle. Background Art

[0002] Major commercial vehicle manufacturers have begun to transform existing traditional commercial vehicle models into hybrid vehicles to improve the fuel economy of existing commercial vehicles. Because heavy-duty commercial vehicles are heavy, even if drive motors are introduced during the hybridization process, they need to be equipped with multi-speed gearboxes to better drive heavy-duty commercial vehicles. The heavy weight of heavy-duty commercial vehicles and the power limitation of the drive motor will result in the kinetic energy of the entire vehicle not being fully used by the motor for power generation during the process of braking energy recovery. This means that a considerable portion of the kinetic energy of the entire vehicle will be converted into heat energy dissipation by the mechanical braking mechanism. Therefore, using the motor to recover the kinetic energy of the entire vehicle as much as possible is of great significance to improving the energy efficiency of heavy-duty hybrid commercial vehicles.

[0003] At present, most manufacturers adopt a braking energy recovery strategy for heavy-duty hybrid commercial vehicles that is similar to that for hybrid passenger vehicles. That is, the motor's recovery torque is calculated in real time based on the current vehicle speed and brake pedal opening, and the motor will not switch gears during the entire braking process. For passenger cars with lighter weight, this strategy can achieve a better driving experience while ensuring that most of the vehicle's kinetic energy is recovered. However, for heavy-duty commercial vehicles with heavier weight, the current strategy recovers too little energy and cannot meet the fuel economy indicators that commercial vehicles are more concerned about.

[0004] like Figure 1 As shown in the figure, the existing heavy-duty hybrid commercial vehicles have a similar strategy to hybrid passenger vehicles in terms of braking energy recovery. First, when the driver steps on the brake pedal, the hybrid control unit (HCU) will calculate the recovery torque of the motor and mechanical brake in real time according to the brake pedal depth and vehicle speed. Then the motor will output the recovery torque according to the recovery torque request of the hybrid controller to generate electricity, and keep the gear position of the motor unchanged. In this process, if the braking capacity of the motor is insufficient, the mechanical braking system will participate in braking to ensure safety. As mentioned above, the gear position of the motor remains unchanged during the entire braking energy recovery process. Due to the limited power of the motor and the large kinetic energy of the heavy-duty vehicle, a considerable part of the kinetic energy of the vehicle will be dissipated in the form of heat energy by the mechanical brake. In addition, the speed of the vehicle will decrease during the braking process. Since the gear position remains unchanged, this will cause the motor speed to decrease, so the power recovered by the motor will also decrease, resulting in a further reduction in the amount of kinetic energy recovered by the vehicle. Summary of the invention

[0005] The purpose of the present invention is to provide a new type of brake energy recovery method for hybrid heavy-duty commercial vehicles. In combination with the characteristics of heavy-duty commercial vehicles, a brake energy recovery strategy is designed to maximize the recovery of the vehicle's kinetic energy by controlling the motor and the gearbox, thereby improving the fuel economy of the hybrid heavy-duty commercial vehicle.

[0006] The technical solution of the present invention is:

[0007] A method for braking energy recovery of a heavy-duty hybrid commercial vehicle comprises the following steps:

[0008] S1. When the driver presses the brake pedal, the current brake pedal depth value is sent to the hybrid controller;

[0009] S2: The hybrid controller calculates the motor's recovery torque and the mechanical brake's braking torque in real time based on the current vehicle speed and brake pedal depth value;

[0010] S3, control the motor to output the recovery torque, and control the mechanical brake to output the braking torque, at this time the vehicle speed will decrease;

[0011] S4: When the motor speed is lower than the base speed, the hybrid controller sends a downshift request to the transmission;

[0012] S5: The gearbox completes the downshift action according to the received downshift request, and the motor continues to output the recovery torque; the motor speed increases after the downshift and is greater than the base speed again. At this time, the motor will recover the kinetic energy of the vehicle at the maximum power;

[0013] S6. In the subsequent process, if the motor speed drops below the base speed again, the hybrid system will repeat the downshift process from S4 to S5.

[0014] Preferably, in step S4, when the motor speed is higher than the base speed, the motor enters a constant power region.

[0015] Preferably, in step S2, the method in which the hybrid controller calculates the recovery torque of the motor and the braking torque of the mechanical brake in real time according to the current vehicle speed and the brake pedal depth value is:

[0016] a. Look up the table based on the current vehicle speed and the current pedal opening to obtain a total wheel-end recovery torque Tre;

[0017] b. Due to the inertia of heavy-duty commercial vehicles, the motor will output the current maximum torque, so the braking torque is distributed as follows:

[0018] T mot =T mot_max ;

[0019] T Mec_brk =T re -T mot *i mot ;

[0020] Where T mot is the target torque output by the motor, T mot_max is the maximum torque of the current motor; T Mec_brk is the braking torque of the current mechanical braking system, i mot is the speed ratio from the motor to the wheel end.

[0021] Preferably, during braking, such as downshifting, the speed ratio from the motor to the wheel end is i mot will increase. According to the calculation formula of mechanical braking torque, at this time, the mechanical braking torque T Mec_brk will decrease; due to the mechanical braking torque T Mec_brk A decrease will result in a decrease in the amount of vehicle kinetic energy converted into heat energy for the braking system, thereby increasing the energy recovered for power generation through the motor, ultimately achieving the goal of improving fuel economy.

[0022] The advantages of the present invention are:

[0023] The new hybrid heavy-duty commercial vehicle energy recovery method proposed in the present invention improves the existing brake energy recovery strategy by controlling the gearbox downshift during the recovery process to maximize the motor recovery power, thereby improving the recovery of the vehicle's kinetic energy. After analyzing the measured data, the vehicle using the brake energy recovery method proposed in the present invention can recover more energy than the vehicle using the original strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0025] Figure 1 This is a flow chart of the current heavy-duty hybrid commercial vehicle braking energy recovery;

[0026] Figure 2 This is a flow chart of the braking energy recovery of the new heavy-duty hybrid commercial vehicle proposed in the present invention. DETAILED DESCRIPTION

[0027] like Figure 2 FIG. 1 is a flowchart of a heavy-duty hybrid commercial vehicle braking energy recovery method provided by the first embodiment of the present invention. Typically, this embodiment is applicable to the braking energy recovery of a P2.5 hybrid commercial vehicle. In this embodiment, during the braking energy recovery process, the hybrid controller issues a downshift request to downshift the transmission to increase the recovery power of the motor. Specifically, the method includes the following steps:

[0028] A method for braking energy recovery of a heavy-duty hybrid commercial vehicle comprises the following steps:

[0029] S1. When the driver presses the brake pedal, the current brake pedal depth value is sent to the hybrid controller;

[0030] S2: The hybrid controller calculates the motor's recovery torque and the mechanical brake's braking torque in real time based on the current vehicle speed and brake pedal depth value;

[0031] Since heavy-duty commercial vehicles have large inertia, under most braking conditions, the motor will output the current maximum torque, so the braking torque is distributed as follows:

[0032] T mot =T mot_max ;

[0033] T Mec_brk =T re -T mot *i mot ;

[0034] Where T mot is the target torque output by the motor, T mot_max is the maximum torque of the current motor; T Mec_brk is the braking torque of the current mechanical braking system, i mot is the speed ratio from the motor to the wheel end;

[0035] During braking, if downshifting is performed, the speed ratio from the motor to the wheel end is i mot will increase. According to the calculation formula of mechanical braking torque, at this time, the mechanical braking torque T Mec_brk will decrease; due to the mechanical braking torque T Mec_brk A decrease will result in a decrease in the amount of vehicle kinetic energy converted into heat energy for the braking system, thereby increasing the energy recovered for power generation through the motor, ultimately achieving the goal of improving fuel economy.

[0036] S3, control the motor to output the recovery torque, and control the mechanical brake to output the braking torque, at this time the vehicle speed will be reduced;

[0037] S4: When the motor speed is higher than the base speed, the motor enters the constant power zone; when the motor speed is lower than the base speed, the hybrid controller sends a downshift request to the gearbox;

[0038] S5: The gearbox completes the downshift action according to the received downshift request, and the motor continues to output the recovery torque; the motor speed increases after the downshift and is greater than the base speed again. At this time, the motor will recover the kinetic energy of the vehicle at the maximum power;

[0039] S6. In the subsequent process, if the motor speed drops below the base speed again, the hybrid system will repeat the downshift process from S4 to S5.

[0040] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any modifications made according to the spirit of the main technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A braking energy recovery method for a heavy-duty hybrid commercial vehicle, characterized in that: Includes steps: S1. When the driver presses the brake pedal, the current brake pedal depth value is sent to the hybrid controller; S2: The hybrid controller calculates the motor's recovery torque and the mechanical brake's braking torque in real time based on the current vehicle speed and brake pedal depth value; S3, control the motor to output the recovery torque, and control the mechanical brake to output the braking torque, at this time the vehicle speed will be reduced; S4: When the motor speed is lower than the base speed, the hybrid controller sends a downshift request to the transmission; S5: The gearbox completes the downshift action according to the received downshift request, and the motor continues to output the recovery torque; the motor speed increases after the downshift and is greater than the base speed again. At this time, the motor will recover the kinetic energy of the vehicle at the maximum power; S6. In the subsequent process, if the motor speed drops below the base speed again, the hybrid system will repeat the downshift process from S4 to S5.

2. The braking energy recovery method for a heavy-duty hybrid commercial vehicle according to claim 1, characterized in that: In step S4, when the motor speed is higher than the base speed, the motor enters the constant power zone.

3. The braking energy recovery method for a heavy-duty hybrid commercial vehicle according to claim 1, characterized in that: In step S2, the method in which the hybrid controller calculates the recovery torque of the motor and the braking torque of the mechanical brake in real time is: a. According to the current vehicle speed and the current pedal opening, the total wheel end recovery torque T is obtained by looking up the table. re ; b. Due to the inertia of heavy-duty commercial vehicles, the motor will output the current maximum torque, so the braking torque is distributed as follows: T mot =T mot_max ; T Mec_brk =T re -T mot *i mot ; Where T mot is the target torque output by the motor, T mot_max is the maximum torque of the current motor; T Mec_brk is the braking torque of the current mechanical braking system, i mot is the speed ratio from the motor to the wheel end.

4. The braking energy recovery method for a heavy-duty hybrid commercial vehicle according to claim 3, characterized in that: During braking, if downshifting is performed, the speed ratio from the motor to the wheel end is i mot will increase. According to the calculation formula of mechanical braking torque, at this time, the mechanical braking torque T Mec_brk will decrease; Due to the mechanical braking torque T Mec_brk A decrease will result in a decrease in the amount of vehicle kinetic energy converted into heat energy for the braking system, thereby increasing the energy recovered for power generation through the motor, ultimately achieving the goal of improving fuel economy.

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