CN111645686A

CN111645686A - Driving force recovery control method and device and 48V driving system

Info

Publication number: CN111645686A
Application number: CN202010507889.8A
Authority: CN
Inventors: 王歆誉; 曹龙; 朱桂庆; 张荣辉; 李长洲
Original assignee: FAW Group Corp
Current assignee: FAW Group Corp
Priority date: 2020-06-05
Filing date: 2020-06-05
Publication date: 2020-09-11
Anticipated expiration: 2040-06-05
Also published as: CN111645686B; WO2021244464A1

Abstract

The invention discloses a driving force recovery control method and device and a 48V driving system. When the running condition is switched from the stop sliding mode to the driving mode, the control method comprises the following steps: determining a target gear of a transmission, a target speed of an engine, and a clutch speed; and controlling the rotating speed of the engine to be increased to a target rotating speed, and controlling a shifting fork of the transmission to be connected into a target gear when the engine starts to increase the rotating speed, wherein the target gear is matched with the rotating speed of the clutch. According to the control method provided by the invention, in the driving force recovery stage, the target gear is selected firstly, and the shifting fork which is emptied in the shutdown sliding stage is directly connected to the target gear, so that the up-shifting and down-shifting operations in the driving force recovery process are avoided, and the time for switching the shutdown sliding mode to the driving mode can be reduced.

Description

Driving force recovery control method and device and 48V driving system

Technical Field

The embodiment of the invention relates to an automobile driving control technology, in particular to a driving force recovery control method and device and a 48V driving system.

Background

An automobile with a 48V electrical system has a stop-coast mode in which the engine of the automobile is stopped and the drive train between the engine and the clutch is disconnected, and when the driver depresses the accelerator pedal again, the entire automobile needs to be returned to a normal drive mode.

In the prior art, when the driver needs to switch from the stop coasting mode to the normal driving mode, in order to meet the driving demand of the driver, the downshift control is usually required during the stop coasting, and in addition, the clutch controller needs to supply oil pressure to the friction coupling element in the transmission during the stop coasting so that the driving system can respond to the acceleration request of the driver in time. In the control method in the prior art, the control of the clutch and the transmission is required to be realized in the stop sliding stage, extra resistance exists in the stop sliding process to influence the sliding distance, and meanwhile, due to the control processes of downshift and the like of the transmission, a certain delay time exists when the stop sliding mode is switched to the driving mode.

Disclosure of Invention

The invention provides a driving force recovery control method and device and a 48V driving system, which are used for achieving the purposes of prolonging the stop sliding distance and enabling a vehicle to recover driving force quickly and stably.

In a first aspect, an embodiment of the present invention provides a driving force recovery control method, where when a driving condition is switched from a stop-and-coast mode to a driving mode, the control method includes:

determining a target gear of a transmission, a target speed of an engine, and a clutch speed; controlling the rotating speed of the engine to be increased to the target rotating speed, controlling a shifting fork of a transmission to be connected into the target gear when the rotating speed of the engine starts to be increased,

wherein the target gear is matched with the clutch speed.

Further, controlling a shift fork of a transmission to access the target gear includes:

controlling clutch oil filling to enable the oil pressure in the clutch to be at a set target oil pressure, wherein the difference between the target oil pressure and the oil pressure corresponding to Kp is a first pressure value.

Further, when the engine is at the target rotation speed and the oil pressure of the clutch is at the target oil pressure,

and controlling the engine to be combined with the clutch, and controlling the output torque of the clutch to follow the output torque of the engine in a segmented mode when the rotating speed of the engine is continuously increased from the target rotating speed.

Further, two-stage control is performed on the output torque of the clutch based on the coefficient of variation,

and controlling the variation of the output torque of the clutch to be the same as that of the output torque of the engine when the first-stage control is performed on the output torque of the clutch.

Further, when the first-stage control is performed on the output torque of the clutch, the feed-forward control is performed on the rotation speed of the engine at the same time, so that the rotation speed of the engine is stably increased.

Further, when the output torque of the clutch is controlled in the second stage, the output torque is controlled to be the same as the allowable torque according to the slip difference.

Further, the target rotation speed is determined by the transmission output shaft rotation speed, the target gear, and the slip difference.

In a second aspect, an embodiment of the present invention further provides a driving force recovery control apparatus, including a driving force recovery module configured to:

when the running condition is switched from a stop sliding mode to a driving mode, determining a target gear of a transmission, a target rotating speed of an engine and a clutch rotating speed; controlling the rotating speed of the engine to be increased to the target rotating speed, controlling a shifting fork of a transmission to be connected into the target gear when the rotating speed of the engine starts to be increased,

wherein the target gear is matched with the clutch speed.

In a third aspect, the embodiment of the invention also provides a 48V driving system, which comprises an engine control unit and a transmission control unit,

the engine control unit is connected with an engine, the transmission control unit is connected with a wet type dual-clutch transmission, the engine control unit is in communication connection with the transmission control unit through a CAN bus,

the transmission control unit is configured to execute a driving force recovery control method described in an embodiment of the present invention.

Compared with the prior art, the invention has the beneficial effects that: in the driving force recovery stage, a target gear is selected at first, and the shifting fork which is emptied in the shutdown and slide stage is directly connected to the target gear, so that the up-shifting and down-shifting operations in the driving force recovery process are avoided, and the time for switching the shutdown and slide mode to the driving mode can be shortened.

Drawings

FIG. 1 is a flowchart of a control method in the embodiment;

FIG. 2 is a 48V drive system in an embodiment;

FIG. 3 is a flowchart of another control method in the embodiment

FIG. 4 is a timing chart of a control method in the embodiment;

fig. 5 is a control graph in the embodiment.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Example one

Fig. 1 is a flowchart of a control method in a first embodiment, where the present embodiment is applicable to a case where driving force of a vehicle is recovered when a vehicle is switched from a coast mode to a drive mode, the method may be executed by a driving force recovery control device, the device may be implemented in a software manner, and the device may be configured in an electronic device, for example, a transmission control unit TCU, as shown in fig. 1, and the method may specifically include:

s1, determining a target gear of a transmission, a target rotating speed of an engine and a rotating speed of a clutch.

In an exemplary embodiment, the transmission device adopts a wet dual clutch transmission, which generally includes a shifting fork, two sets of gear gears, an input shaft, two output shafts, two clutches, two solenoid valves, and a hydraulic pump, wherein the two sets of gear gears are respectively disposed on one output shaft, for example, one output shaft is configured with 1-gear, 3-gear, 5-gear, and 7-gear gears, and the other output shaft is configured with 2-gear, 4-gear, and 6-gear gears. The two clutches respectively control one output shaft to be in transmission connection or disconnection with the engine under the action of the electromagnetic valves. Exemplarily, in the present embodiment, the shift fork, the input shaft, the output shaft, and the gear constitute a transmission.

In the present embodiment, the control method is used to control the 48V system to recover driving force, fig. 2 is the 48V driving system in the embodiment, and referring to fig. 2, the 48V system includes an engine control unit 100, a transmission control unit 200, an engine 300, and a wet dual clutch transmission 400.

The engine control unit 100 is in communication connection with the engine 300, the transmission control unit 200 is in communication connection with the wet dual-clutch transmission 400, and the engine control unit 100 and the transmission control unit 200 realize information interaction through a CAN bus. The engine 300 is mechanically connected with the wet dual clutch transmission 400.

In this embodiment, the 48V system mainly relates to two modes, namely a stop-and-slide mode and a driving mode, when in the stop-and-slide mode, the transmission control unit 200 controls two clutches in the wet dual-clutch transmission 400 to be separated from output shafts configured with odd-numbered gears and output shafts configured with even-numbered gears, and controls all shifting forks to be disengaged, at this time, a transmission shaft of an engine and the clutches, and gear gears in the transmission are in a separated state, so that the vehicle does not have the engine to drag back for braking when sliding in the stop-and-slide mode, and the clutches do not generate drag torque, and further the vehicle can keep the sliding process for the longest time by using its own inertia.

When the driver depresses the accelerator pedal, the vehicle exits the coast stop mode and enters the drive mode, at which time a control command is generated mainly by the transmission control unit 200 to restore the vehicle to drive force.

Specifically, the operation process of the transmission control unit 200 in this step includes:

the transmission control unit 200 receives the start flag EMS _ ESR transmitted by the engine control unit 100 through the CAN bus, and upon receiving the start flag, the transmission control unit 200 determines the target gear TR of the wet dual clutch transmission 400 and the target rotation speed TCU _ ETS of the engine 300, and transmits a start permission flag TCU _ ESA, an engine rotation speed control request TCU _ ESCR, and an engine target rotation speed to the engine control unit 100.

For example, the transmission control unit 200 may determine the target gear by fuzzy control according to the current vehicle speed; when the target rotating speed is determined, the formula is as follows:

TCU_ETS＝OS×TR+Slip

in the formula, OS is the current rotating speed value of the output shaft corresponding to the target gear, TR is the target gear, and Slip is the target Slip difference.

In this embodiment, the Slip is determined in the following manner: the transmission control unit 200 obtains the oil temperature of the hydraulic oil in the wet dual-clutch transmission 400, and obtains the target slip-friction difference through table lookup according to the oil temperature and the target gear.

After the transmission control unit 200 determines the target gear, it determines the clutch speed matched with the target gear at the same time, and controls the clutch to rotate at the specified speed, so as to synchronize the engine speed with the clutch speed corresponding to the target gear, ensure the stable engagement between the engine and the clutch, and ensure the driving smoothness when the power is restored.

And S2, controlling the rotating speed of the engine to be increased to a target rotating speed, and controlling the shifting fork to be connected to a target gear when the rotating speed of the engine starts to be increased.

Specifically, in step S2, engine control unit 100 receives the start permission flag, the engine speed control request, and the target speed sent from transmission control unit 200, and then controls engine 300 to enter the speed control mode, and controls the speed of engine 300 to increase from zero to the target speed TCU _ ETS.

In step S2, transmission control unit 200 monitors the change in the rotational speed of engine 300, and the rotational speed control process of engine 300 is characterized by a variable ESP, which is calculated by the following formula:

ESP＝(ES-ESI)/(TCU_ETS-ESI)

in the formula, ES is the engine speed, ESI is the engine initial speed, and when in the shutdown coasting mode, ESI is zero.

At the initial time of engine speed control, that is, when the ESP is 0, the transmission control unit 200 controls the shift fork to directly engage the target gear, and after the engagement is successful, the transmission control unit 200 controls the clutch corresponding to the target gear to be filled with oil, so that the engine 300 and the clutch are half-engaged, and the torque of the engine 300 is input to the wet dual clutch transmission 400.

Fig. 3 is a flowchart of another control method in the embodiment, and referring to fig. 3, as a preferable aspect, the control process of the transmission control unit 200 further includes:

and S3, controlling oil filling of the clutch to enable the oil pressure in the clutch to be at a set target oil pressure, wherein the difference between the target oil pressure and the oil pressure corresponding to the Kp point is a first pressure value.

The Kp point is a clutch half joint point, when the clutch oil pressure is at the Kp point, the output torque of the engine starts to drive an input shaft in the transmission to rotate, and the transmission starts to output the torque. In step S201, the engine is in a speed increasing stage, where the target oil pressure of the clutch is slightly less than Kp point, and the input shaft of the transmission is in a stationary state, so as to avoid vehicle hump caused by high oil pressure of the clutch when the engine is controlled by the speed increasing stage.

And S4, when the engine is at the target rotating speed and the oil pressure of the clutch is at the target oil pressure, controlling the engine to be combined with the clutch, and when the rotating speed of the engine is continuously increased from the target rotating speed, controlling the output torque of the clutch to follow the output torque of the engine in a segmented mode.

When the ESP is 1, that is, the engine speed is the same as the target speed, the transmission control unit 200 stops sending the engine speed control request, the engine 300 enters the torque control mode, and the engine control unit 100 controls the engine 300 to output the target torque, accordingly, the speed of the engine 300 is greater than the target speed of the engine 300 in the speed control mode in the process. Illustratively, the target torque of the engine 300 is determined by the depression depth of the accelerator pedal.

While the engine 300 is in the speed control mode, the engine speed is gradually increased from 0 to the target speed, and accordingly the value of the ESP is gradually changed from 0 to 1, fig. 4 is a timing chart of a control method in the embodiment, and referring to fig. 4, when the value of the ESP is close to 1, the transmission control unit 200 controls the oil pressure in the clutch to be increased from the target oil pressure to the Kp point, and the transmission control unit 200 starts torque control of the clutch.

Fig. 5 is a control graph in an embodiment, and referring to fig. 5, it is exemplified that the engine 300 is in a torque control mode, the transmission control unit 200 performs torque control of the clutch, performs two-stage control of the output torque of the clutch based on a change coefficient, and controls the amount of change of the output torque of the clutch to be the same as the amount of change of the output torque of the engine in the first-stage control of the output torque of the clutch. When the first-stage control is carried out on the output torque of the clutch, the feedforward control is carried out on the rotating speed of the engine at the same time, so that the rotating speed of the engine is stably improved.

For example, the process of engaging the engine and the clutch may be divided into two main stages, namely, a slip stage (first stage) in which the output torque of the transmission is related to the engagement position of the clutch, and a synchronous engagement stage (second stage), in step S202, the transmission control unit 200 adjusts the engagement position of the clutch and thus the allowable transmission torque of the clutch by controlling the oil pressure of the clutch, so that the allowable transmission torque of the clutch may be increased following the increase of the output torque of the engine. In the slip phase, if the engagement speed of the clutch is too slow and the output torque of the engine is increased too fast, the rotational speed of the engine may be increased, so in the slip phase, the transmission control unit 200 performs feedforward control on the rotational speed of the engine to stably increase the output torque of the engine.

Illustratively, the feedforward torque Torq is introduced in the step, and the expression is as follows:

Torq＝Profile×Gain

in the formula, Profile is a change coefficient, and the value of the change coefficient is gradually reduced from 1 to 0 from the starting time of the sliding grinding stage to the starting time of the synchronous jointing stage. Gain is used as an exemplary Gain link, the transmission control unit 200 obtains the current oil pressure change rate of the clutch, determines the expected rising torque rate of the engine according to the oil pressure change rate and the target gear, and uses the expected rising torque rate as the Gain link Gain, and the corresponding relation between the oil pressure change rate, the target gear and the expected rising torque rate is obtained through test calibration.

After determining the feed-forward torque Torq, transmission control section 200 transmits the feed-forward torque to engine control section 100, and engine control section 100 preferentially controls the output torque of the engine based on the received feed-forward torque.

And when the output torque of the clutch is controlled in the second stage, controlling the output torque to be the same as the allowable torque according to the slip difference.

For example, in the second stage control, the engine and the clutch are synchronously engaged, and the wet dual clutch transmission needs to maintain a certain slip difference during the torque transmission process, so in this step, the transmission control unit 200 performs PI closed-loop control on the oil pressure with the actual slip difference and the target slip difference as control inputs and the oil pressure of the clutch as a controlled variable, so that the output torque and the allowable torque are the same.

In the embodiment, the driving force recovery control method controls the clutch to be separated and the shifting fork to be disengaged in the shutdown sliding stage so as to reduce sliding resistance to the maximum extent. And in the driving force recovery stage, the clutch torque is controlled in a sectional control mode, and the variable quantity of the engine torque is controlled through the feedforward torque, so that the driving force can be stably and quickly increased to the expected value of a driver.

Example two

The present embodiment proposes a driving force recovery control apparatus, the control apparatus being disposed in a transmission control unit, the control apparatus including a driving force recovery module for:

when the running condition is switched from a stop sliding mode to a driving mode, determining a target gear of a transmission, a target rotating speed of an engine and a clutch rotating speed; and controlling the rotating speed of the engine to be increased to a target rotating speed, and controlling a shifting fork of the transmission to be connected into the target gear when the engine starts to increase the rotating speed, wherein the target gear is matched with the rotating speed of the clutch.

Optionally, when the transmission control unit controls the shifting fork of the transmission to access the target gear:

the driving force recovery module is used for controlling oil filling of the clutch to enable the oil pressure in the clutch to be at a set target oil pressure, wherein the difference between the target oil pressure and the oil pressure corresponding to the Kp point is a first pressure value.

Alternatively, the driving force recovery module is configured to control the engine to be coupled to the clutch when the engine is at a target rotation speed and the oil pressure of the clutch is at the target oil pressure, and control the output torque of the clutch to follow the output torque of the engine in a stepwise manner when the rotation speed of the engine is continuously increased from the target rotation speed.

The driving force recovery module controls the output torque of the clutch in two stages based on the change coefficient, controls the change amount of the output torque of the clutch to be the same as the change amount of the output torque of the engine when the output torque of the clutch is controlled in the first stage, and performs feedforward control on the rotating speed of the engine when the output torque of the clutch is controlled in the first stage to stably increase the rotating speed of the engine.

When the second-stage control is performed on the output torque of the clutch, the driving force recovery module controls the output torque to be the same as the allowable torque according to the slip difference.

In this embodiment, the beneficial effects of the driving force recovery control device are the same as those described in the first embodiment, and are not described herein again.

EXAMPLE III

Referring to fig. 2, the present embodiment proposes a 48V drive system including an engine control unit 100 and a transmission control unit 200.

The engine control unit 100 is connected with the engine 300, the transmission control unit 200 is connected with the wet dual clutch transmission 400, and the engine control unit 100 is in communication connection with the transmission control unit 200 through a CAN bus.

In the present embodiment, the transmission control unit 200 is configured to execute the driving force recovery control method described in the first embodiment, and the advantageous effects are the same as those described in the first embodiment.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A driving force recovery control method, characterized in that when a running condition is switched from a stop coasting mode to a driving mode, the control method comprises:

wherein the target gear is matched with the clutch speed.

2. The driving force recovery control method according to claim 1, wherein controlling a shift fork of a transmission to engage the target gear includes:

3. The drive force recovery control method according to claim 2, characterized in that when the engine is at the target rotation speed and the oil pressure of the clutch is at the target oil pressure,

4. The drive power recovery control method according to claim 3, characterized in that the output torque of the clutch is controlled in two stages based on a coefficient of variation,

5. The driving force recovery control method according to claim 4, wherein while the output torque of the clutch is controlled in the first stage, the rotational speed of the engine is feed-forward controlled to stably increase the rotational speed of the engine.

6. The driving force recovery control method according to claim 4, wherein in the second-stage control of the output torque of the clutch, the output torque is controlled to be the same as an allowable torque in accordance with a slip difference.

7. The drive power recovery control method according to claim 1, characterized in that the target rotation speed is determined by a transmission output shaft rotation speed, the target gear, and a slip.

8. A driving force recovery control device characterized by comprising a driving force recovery module configured to:

wherein the target gear is matched with the clutch speed.

9. A48V driving system is characterized by comprising an engine control unit and a transmission control unit,

the transmission control unit is configured to execute the driving force recovery control method according to any one of claims 1 to 7.