CN111483453B

CN111483453B - double-BSG (binary System generator) weakly mixing system for medium-weight card and control method

Info

Publication number: CN111483453B
Application number: CN202010316615.0A
Authority: CN
Inventors: 郄鹤峰; 申培锋; 祝贺; 冯帅; 姜杨; 刘诗逸
Original assignee: Dongfeng Commercial Vehicle Co Ltd
Current assignee: Dongfeng Commercial Vehicle Co Ltd
Priority date: 2020-04-21
Filing date: 2020-04-21
Publication date: 2021-08-31
Anticipated expiration: 2040-04-21
Also published as: CN111483453A

Abstract

The invention discloses a double-BSG (base band generator) weak hybrid system of a medium-weight truck and a control method, which relate to the technical field of automobile control and comprise a motor controller, a 48V storage battery and two BSGs (base band generators), wherein the 48V storage battery and the two BSGs are respectively connected with the motor controller; when the engine is in a starting state or an accelerating state, the motor controller is used for controlling the two BSGs to output positive torque, and the 48V storage battery is in a discharging state and provides power for the two BSGs; when the engine is in an economical rotating speed state or a braking state, the motor controller is used for controlling the two BSGs to output negative torque, and the 48V storage battery is in a charging state and used for storing electric energy output by the two BSGs. According to the invention, the double BSGs are connected in parallel, and the motor controller controls the two BSGs to be in different working states according to different working conditions, so that starting and stopping, power assistance and energy recovery are provided for the medium and heavy truck engine, a better oil-saving effect is achieved, and the economy of the whole truck is improved.

Description

double-BSG (binary System generator) weakly mixing system for medium-weight card and control method

Technical Field

The invention relates to the technical field of automobile control, in particular to a double BSG (base band gap) weak mixing system for a medium-weight card and a control method.

Background

At present, the country pays more and more attention to environmental protection, and national V emission standard is implemented nationwide in 2018 and 1 month, and the requirement on emission is more and more strict. In addition, from the viewpoint of national energy safety, oil consumption for automobiles accounts for six of the total oil consumption, and therefore, whether it is a passenger car or a commercial car, it is inevitable to produce a more energy-saving automobile.

The automobile 48V weak hybrid system overcomes the problem of low power and overlarge current of a low-voltage system, and compared with a traditional automobile and a heavily-hybrid new energy automobile, the cost of the automobile 48V weak hybrid system is extremely high in cost performance. BSG (Belt-Driven Starter Generator, Belt-Driven starting/power generation integrated motor) is the first choice of the 48V weak mixing system of the passenger vehicle, and has the advantages of cost performance and high reliability.

For a medium and heavy truck engine with large starting power and starting torque, the starting power of a low-power BSG is insufficient, and the BSG can not be really commercialized and applied in the field of commercial vehicles; when the high-power BSG is installed at the front end of an engine, the large-power BSG has difficulty in spatial arrangement due to large volume and does not have the cost performance advantage. Therefore, the current 48V weak mixing system has no practical application in medium heavy trucks.

Disclosure of Invention

Aiming at one of the defects in the prior art, the invention aims to provide a double-BSG weak mixing system and a control method for a medium-heavy truck.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows: a double-BSG weak hybrid system of a medium-weight truck comprises a motor controller, a 48V storage battery and two belt transmission starting/power generation integrated motor BSGs, wherein the 48V storage battery and the two belt transmission starting/power generation integrated motor BSGs are respectively connected with the motor controller;

when the engine is in a starting state or an accelerating state, the motor controller is used for controlling the two BSGs to output positive torque, and the 48V storage battery is in a discharging state and provides power for the two BSGs;

when the engine is in an economical rotating speed state or a braking state, the motor controller is used for controlling the two BSGs to output negative torque, and the 48V storage battery is in a charging state and used for storing electric energy output by the two BSGs.

On the basis of the technical scheme, the system further comprises a DC-DC converter, the DC-DC converter is respectively connected with the motor controller and the 48V storage battery, and the motor controller is further used for controlling the DC-DC converter to convert the 48V electric energy output by the two BSGs and supply power to the whole vehicle.

On the basis of the technical scheme, the two BSGs are both arranged at the front end of the engine and are connected with the engine through the same belt.

On the basis of the technical scheme, the two BSGs are both arranged at the front end of the engine and are respectively connected with the engine through a group of belts.

The invention also provides a control method based on the double BSG weak hybrid system of the medium-weight card, which comprises the following steps:

judging the state of the engine through the vehicle control unit;

when the engine is in a starting state or an accelerating state, the motor controller controls the two BSGs to output positive torque, and the 48V storage battery is in a discharging state and provides power for the two BSGs;

when the engine is in an economical rotating speed state or a braking state, the motor controller controls the two BSGs to output negative torque, and the 48V storage battery is in a charging state and is used for storing electric energy output by the two BSGs.

On the basis of the technical scheme, when the engine is in a starting state, the motor controller controls the two BSGs to output positive torques, and the method specifically comprises the following steps:

determining the SOC value of the current residual electric quantity of the storage battery;

when the SOC value is smaller than a first electric quantity threshold value and larger than a second electric quantity threshold value, the motor controller controls a BSG to start and drag the engine firstly; if the dragging time of the engine reaches a first time threshold value and does not reach a rotating speed threshold value, the motor controller controls another BSG to start and drag the engine;

and if the time for simultaneously working the two BSGs does not exceed the second time threshold and the engine reaches the rotating speed threshold, the engine is considered to be successfully started, otherwise, the engine is failed to be started, and the starting state is exited.

On the basis of the technical scheme, the two BSGs start in turn or the BSG with larger torque applied to the crankshaft end of the engine always starts first.

On the basis of the technical scheme, when the SOC value is larger than or equal to a first electric quantity threshold value, the motor controller controls the two BSGs to simultaneously drive the engine at the maximum power output.

On the basis of the technical scheme, when the engine is in an economic rotating speed state, the motor controller controls the two BSGs to output negative torques, and the method specifically comprises the following steps:

and if the SOC value is smaller than a third electric quantity threshold value, the motor controller controls the two BSGs to simultaneously output negative torque and controls the absolute value of the difference value of the output voltages of the two BSGs to be smaller than a voltage threshold value.

On the basis of the technical scheme, when the engine is in a braking state, the motor controller controls the two BSGs to output maximum negative torque.

Compared with the prior art, the invention has the advantages that:

(1) according to the medium-weight truck double-BSG weak mixing system, the double BSGs are connected in parallel, the volumes of the two BSGs are relatively small, and therefore the existing space can be utilized for direct installation and arrangement on the existing engine wheel system, and redesign of the engine structure is avoided; in addition, the two BSGs are connected with the motor controller, the motor controller controls the two BSGs to be in different working states according to different working conditions, starting and stopping, power assisting and energy recovery are provided for the medium-weight truck engine, a better oil saving effect is achieved, and the economy of the whole truck is improved.

(2) According to the control method of the double BSG weak hybrid system of the medium-weight truck, when the engine is in a starting state, the motor controller carries out time-sharing or cooperative control on the two BSGs according to the current SOC value of the storage battery, so that starting torque is increased, and starting performance is improved. In addition, the time-sharing starting assisting force can reduce the dead-drag clamping condition in the starting process.

Drawings

Fig. 1 is a block diagram of a medium-heavy-card dual-BSG weakly-mixed system according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a dual-BSG weakly-mixed system with a medium-density card according to an embodiment of the present invention;

fig. 3 is a first connection diagram of two BSGs according to an embodiment of the present invention;

FIG. 4 is a second exemplary connection diagram of two BSGs, according to an embodiment of the invention;

fig. 5 is a flowchart of an engine start state according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Referring to fig. 1, the present invention provides an embodiment of a dual BSG weak hybrid system for a medium-heavy truck, which includes a motor controller, two BSGs and a 48V battery, wherein the motor controller is respectively connected to the two BSGs and the 48V battery through a CAN bus, and the two BSGs are connected in parallel to an engine.

When the engine is in a starting state or an accelerating state, the motor controller is used for controlling the two BSGs to output positive torque to provide power for the engine, and the 48V storage battery is in a discharging state to provide power for the two BSGs.

Preferably, when the engine is in a braking state, the motor controller is configured to control the two BSGs to output a maximum negative torque to assist the engine braking.

In the medium-heavy truck dual-BSG weak hybrid system, the dual BSGs are connected in parallel, the volumes of the two BSGs are relatively small, and the existing space can be utilized for direct installation and arrangement on the existing engine wheel train, so that the redesign of the engine structure is avoided; in addition, the two BSGs are connected with the motor controller, the motor controller controls the two BSGs to be in different working states according to different working conditions, starting and stopping, power assisting and energy recovery are provided for the medium-weight truck engine, a better oil saving effect is achieved, and the economy of the whole truck is improved.

Further, the weak mixing system of the embodiment further includes a DC-DC converter (Direct current-Direct current converter). The DC-DC converter is respectively connected with the motor controller and the 48V storage battery, and the motor controller is also used for controlling the DC-DC converter to convert the 48V electric energy output by the two BSGs so as to provide electric energy for the whole vehicle.

In this embodiment, the 48V battery is further connected to an original vehicle 24V electrical system through a DC-DC converter, and the original vehicle 24V electrical system is used for electrical power supply of the entire vehicle.

Referring to fig. 2, the motor controller is connected to a VECU (Vehicle Electronic Control Unit) through a CAN bus, and the motor controller controls the two BSGs to cooperatively operate according to a communication command of the VECU, and stabilizes output electric energy of the two BSGs into direct current having a voltage of 48 to 57V and outputs the direct current by controlling torque of the BSGs when the two BSGs output negative torque, and the BSGs are in a power generation state at this time. Meanwhile, the motor controller controls the DC-DC converter to work in a voltage reduction mode, the output voltage of the motor controller is reduced to 25.2-28.8V direct current, and then 24V electricity of the original vehicle is used for supplying power to the electric appliances of the whole vehicle.

Alternatively, the 48V battery has a capacity of 20-170AH, starting power of 5-20KW for single BSG, and starting torque of 20-80Nm for single BSG.

In this embodiment, the motor controller is a dual BSG motor controller, and the torques of the two BSGs can be coupled through a small crankshaft wheel. In addition, compared with the development of a single high-power motor, the double BSG application has cost advantage, and the air cooling can meet the use requirement without adding an additional water cooling device.

Referring to fig. 3, in the present embodiment, the two BSGs are both disposed at the front end of the engine, and the two BSGs are connected to the engine through the same belt.

Specifically, two BSGs are coupled to a crankshaft pulley via the same belt, which in turn cranks the engine. The engine, the clutch, the gearbox and the main speed reducer are connected in sequence, and the main speed reducer is connected with wheels.

The 48V battery is a 48V50AH lithium battery, the power of a single BSG motor is 10KW, the starting torque is 35Nm, the starting and stopping of the engine, power assistance and energy recovery can be achieved, and electric energy is provided for the whole vehicle.

Referring to fig. 4, in another embodiment, two BSGs are disposed at a front end of the engine, and the two BSGs are connected to the engine through a set of belts, respectively.

Specifically, two BSGs are connected to a crankshaft pulley via a set of belts, respectively, to start the engine by driving the crankshaft.

Wherein the 48V battery is a 48V40AH lithium battery, wherein the power of a single BSG motor is 5KW and the starting torque is 20 Nm.

The invention also provides an embodiment of a control method based on the double-BSG weak hybrid system of the medium-heavy card, which comprises the following steps:

first, the state of the engine is determined by the VECU. In the present embodiment, the state of the engine includes a starting state, an accelerating state, an economical rotation speed state, or a braking state.

When the engine is in a starting state or an accelerating state, the motor controller controls the two BSGs to output positive torque to provide power for the engine, and the 48V storage battery is in a discharging state to provide power for the two BSGs.

When the engine is in an acceleration state, the motor controller controls the two BSGs to output positive torque at the same time, so that auxiliary power is provided for the engine, and the driving assistance function is realized.

Further, when the engine is in a starting state, the motor controller controls the two BSGs to output positive torque, and the method specifically comprises the following steps:

first, the motor controller determines the current remaining capacity SOC value of the battery.

When the SOC value is smaller than a first electric quantity threshold value and larger than a second electric quantity threshold value, the motor controller controls a BSG to start and drag the engine firstly; if the engine reaches the rotating speed threshold value when the dragging time does not exceed the first time threshold value, the engine is considered to be started successfully, and the other BSG does not need to participate in starting; and if the engine does not reach the rotating speed threshold value when the dragging time reaches the first time threshold value, the motor controller controls another BSG to start and drag the engine.

When the engine is in a starting state, the BSG is started at the maximum power, namely, the maximum positive torque is output.

If the time for simultaneously working the two BSGs does not exceed a second time threshold and the engine reaches a rotating speed threshold, the engine is considered to be successfully started, and the starting state is exited; otherwise, the engine is considered to be failed to start, the starting state is also exited, and the follow-up action of the driver is waited. In this embodiment, the threshold rotation speed is 80 r/min.

Preferably, the two BSGs start in turn, that is, in the current engine starting state, if one BSG starts first, the other BSG starts first when the engine is restarted next time, so as to reduce fatigue loss to the BSGs.

The relatively small BSG belt reduction ratio, and the relatively large output torque, makes it easier for the engine to reach the threshold speed when a single BSG is being towed to the first time threshold. Therefore, in other embodiments, the BSG with the larger torque applied to the crankshaft end of the engine through the crankshaft small wheel can be always started first, and the engine is dragged by the BSG first.

Further, when the SOC value is greater than or equal to a first electric quantity threshold, the motor controller controls the two BSGs to simultaneously drive the engine at a maximum power output.

In this embodiment, when the SOC value is smaller than the second electric quantity threshold, it indicates that the electric quantity of the battery is insufficient to support the vehicle to start, and the motor controller controls the two BSGs to exit the start state.

In this embodiment, when the engine is in a starting state, the motor controller performs time-sharing or cooperative control on the two BSGs according to the current SOC value of the battery, so as to increase the starting torque and improve the starting performance. In addition, the time-sharing starting assisting force can reduce the dead-drag clamping condition in the starting process.

Referring to fig. 5, the control method of the present embodiment in the engine starting state specifically includes:

s1, judging whether the SOC value of the current 48V storage battery is larger than or equal to a first electric quantity threshold value, if so, turning to S2, and otherwise, turning to S3.

S2, the motor controller controls the two BSGs to simultaneously drag the engine with the maximum power output until the engine is successfully started, and then the engine can exit the starting state.

S3, judging whether the SOC value is larger than a second electric quantity threshold value, if so, turning to S4, and otherwise, turning to S8.

And S4, the motor controller controls the BSG which is not started first last time to start and drag the engine.

S5, judging whether the engine reaches a rotating speed threshold value before the dragging time exceeds a first time threshold value, if not, turning to S6, and if so, determining that the engine is started successfully.

And S6, controlling another BSG to start and drag the engine by the motor controller.

And S7, judging whether the engine reaches a rotating speed threshold value before the time that the two BSGs work simultaneously exceeds a second time threshold value, if not, turning to S8, and if so, determining that the engine is started successfully.

And S8, the engine fails to start and exits from the starting state.

In this embodiment, the first electric quantity threshold and the second electric quantity threshold can be obtained through a bench test or a whole vehicle test. The first electric quantity threshold value is determined according to the characteristics of a 48V storage battery, most of the 48V storage batteries are lithium ion batteries, the electric quantity is in a high state when the electric quantity is more than 85% -90%, the storage battery is generally discharged without being charged, and the second electric quantity threshold value is not less than the lowest electric quantity capable of starting the vehicle. Preferably, the first charge threshold is 85% and the second charge threshold is 10%.

Optionally, the first time threshold is determined by matching the engine model with a vehicle model platform, and can be obtained by a bench test or a whole vehicle test. Since the BSG may not continue to operate at maximum power for too long a time that would otherwise impair motor life, the second time threshold is typically within 30 s. In this embodiment, the first time threshold is 1s, and the second time threshold is 25 s.

Therefore, when the SOC value of the present battery is greater than 85%, i.e., the 48V battery is sufficiently charged, the starting performance can be pursued while neglecting energy consumption, and the dual BSG can be directly output at the maximum power to reduce the mechanical loss of the BSG. When the SOC value of the current storage battery is more than 10% and less than 85%, namely the 48V storage battery is insufficient in electric quantity, one BSG can be controlled to drag the engine with the maximum power, and if the engine does not reach the rotating speed threshold value when the dragging time reaches 1s, the motor controller controls the other BSG to start and drag the engine, so that the starting success probability is increased.

And under the summer condition, the first time threshold value obtained according to a certain vehicle sample is measured and is added for 0.2 second, and the first time threshold value is the first time threshold value under the winter condition.

In this embodiment, the motor controller performs bus control on the two BSGs and performs distinguishing and identification according to different bus addresses of the two BSGs.

Further, when the engine is in the economical speed state, the motor controller may control the two BSGs to output negative torques, specifically including:

first, the motor controller determines the current remaining capacity SOC value of the battery and compares it with a third capacity threshold. Optionally, the third electric quantity threshold may be obtained by a vehicle electric balance test according to the vehicle load configuration. In this embodiment, the third electric quantity threshold is 85%.

And if the SOC value is smaller than a third electric quantity threshold value, the motor controller controls the two BSGs to simultaneously output negative torque, and controls the absolute value of the difference value of the output voltages of the two BSGs to be smaller than a voltage threshold value, so that power generation is performed through the double BSGs, and the driving power generation amount is increased. In this embodiment, the voltage threshold is 0.1V.

Specifically, the output voltages of the two BSGs are monitored by the motor controller. When the deviation of the output voltages of the two BSGs is more than 0.1V, the exciting current of the BSG with higher output voltage is reduced, and the output power of the BSG is adjusted, so that the condition that the two BSGs are inconsistent in load and the durability is reduced is avoided.

Preferably, when the engine is in a braking state, the motor controller controls the two BSGs to simultaneously output a maximum negative torque to brake the engine, thereby recovering braking energy into the 48V battery.

The control method provided by the embodiment of the invention is suitable for the double-BSG weak mixing system of the medium and heavy trucks, and the motor controller can control the two BSGs to be in different working states according to different working conditions, so that starting and stopping, power assistance and energy recovery are provided for the engine of the medium and heavy trucks, and the problem of difficulty in commercialization of the BSGs in the field of the medium and heavy trucks is solved.

The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention.

Claims

1. A double-BSG weak mixing system of a medium-weight card is characterized in that: the device comprises a motor controller, a 48V storage battery and two belt drive starting/generating integrated motors BSG which are respectively connected with the motor controller, wherein the two BSGs are connected with an engine in parallel;

when the engine is in an economical rotating speed state or a braking state, the motor controller is used for controlling the two BSGs to output negative torque, and at the moment, the 48V storage battery is in a charging state and is used for storing electric energy output by the two BSGs;

when the engine is in a starting state, the motor controller is also used for determining the current residual charge SOC value of the storage battery;

the motor controller is also used for controlling a BSG to start and drag the engine firstly when the SOC value is smaller than a first electric quantity threshold value and larger than a second electric quantity threshold value; if the dragging time of the engine reaches the first time threshold value and does not reach the rotating speed threshold value, controlling another BSG to start and drag the engine;

the motor controller is also used for controlling the two BSGs to start in turn or controlling the BSG with larger torque applied to the crankshaft end of the engine to start all the time;

the motor controller is further configured to control the two BSGs to simultaneously tow the engine at maximum power output when the SOC value is greater than or equal to a first charge threshold.

2. The medium-heavy-card dual-BSG weakly-mixed system of claim 1, wherein: the system further comprises a DC-DC converter, the DC-DC converter is respectively connected with the motor controller and the 48V storage battery, and the motor controller is further used for controlling the DC-DC converter to convert the 48V electric energy output by the two BSGs and supply power to the whole vehicle.

3. The medium-heavy-card dual-BSG weakly-mixed system of claim 1, wherein: the two BSGs are both arranged at the front end of the engine, and the two BSGs are connected with the engine through the same belt.

4. The medium-heavy-card dual-BSG weakly-mixed system of claim 1, wherein: the two BSGs are both arranged at the front end of the engine and are respectively connected with the engine through a group of belts.

5. A method for controlling the dual-BSG weakly mixing system according to claim 1, comprising the steps of:

judging the state of the engine through the vehicle control unit;

when the engine is in an economical rotating speed state or a braking state, the motor controller controls the two BSGs to output negative torque, and at the moment, the 48V storage battery is in a charging state and is used for storing electric energy output by the two BSGs; when the engine is in a starting state, the motor controller controls the two BSGs to output positive torques, and the method specifically comprises the following steps:

if the time for simultaneously working the two BSGs does not exceed the second time threshold and the engine reaches the rotating speed threshold, the engine is considered to be successfully started, otherwise, the engine is failed to be started, and the starting state is exited;

the two BSGs start in turn or the BSG with larger torque applied to the crankshaft end of the engine always starts first;

when the SOC value is greater than or equal to a first electric quantity threshold value, the motor controller controls the two BSGs to simultaneously drive the engine at the maximum power output.

6. The control method of claim 5 wherein the motor controller controls the two BSGs to output negative torque when the engine is in the economy speed state, specifically comprising:

7. The control method according to claim 5, characterized in that: when the engine is in a braking state, the motor controller controls the two BSGs to output maximum negative torque.