WO2016189592A1

WO2016189592A1 - Yaw moment control device and yaw moment control method

Info

Publication number: WO2016189592A1
Application number: PCT/JP2015/064796
Authority: WO
Inventors: 勝義小川; 洋平対馬; 信人谷口
Original assignee: 日産自動車株式会社
Priority date: 2015-05-22
Filing date: 2015-05-22
Publication date: 2016-12-01

Abstract

This yaw moment control device controls a yaw moment of a vehicle provided with: a right-and-left-wheel driving force distribution mechanism that changes the driving force distribution of right and left wheels of a vehicle; and a right-and-left-wheel braking force distribution mechanism that changes the braking force distribution of the right and left wheels of the vehicle. The yaw moment control device causes only the right-and-left-wheel driving force distribution mechanism to generate a yaw moment necessary for turning of the vehicle in the case where a lateral acceleration generated during turning of the vehicle is less than a preset predetermined lateral acceleration.

Description

Yaw moment control apparatus and yaw moment control method

The present invention relates to yaw moment control of a vehicle that performs left and right wheel driving force control and left and right wheel braking force control.

Left and right wheel driving force control and left and right wheel braking force control are known as controls for improving vehicle running performance. Left and right wheel driving force control controls the yaw moment of the vehicle by changing the driving force distribution to the left and right driving wheels, that is, the driving wheels on the inner side of the turning and the driving wheels on the outer side of the turning according to the turning state of the vehicle. Is. Left and right wheel braking force control is to control the yaw moment of the vehicle by changing the distribution of braking force to the left and right wheels, that is, the inner wheel and the outer wheel according to the turning state of the vehicle. .

Japanese Patent Application Laid-Open No. 2011-162145 discloses a control device that generates a yaw moment by left and right wheel driving force control when the yaw moment to be generated during turning is less than the maximum value of the yaw moment that can be generated by left and right wheel driving force control. Is described. This control device generates the maximum yaw moment that can be generated by left and right wheel driving force control when the yaw moment that should be generated during turning exceeds the maximum value of yaw moment that can be generated by left and right wheel driving force control. The shortage is covered by left and right wheel drive force control.

However, since the control in the above document does not consider the state of lateral acceleration, there is a possibility that the driver may feel uncomfortable.

Therefore, an object of the present invention is to control the yaw moment of the vehicle by the left and right wheel driving force control and the left and right wheel braking force control without giving the driver a sense of incongruity.

According to an aspect of the present invention, there is provided a vehicle including a left and right wheel driving force distribution mechanism that changes the driving force distribution of the left and right wheels of the vehicle, and a left and right wheel braking force distribution mechanism that changes the braking force distribution of the left and right wheels of the vehicle. A yaw moment control device for controlling a yaw moment is provided. When the lateral acceleration generated during turning of the vehicle is smaller than a predetermined lateral acceleration set in advance, the yaw moment control device generates a yaw moment necessary for turning of the vehicle using only the left and right wheel driving force distribution mechanism.

According to the above aspect, in turning with low lateral acceleration, only the left and right wheel driving force distribution control is executed, so that the vehicle can be turned without decelerating. That is, the vehicle can turn without giving the driver a sense of incongruity.

FIG. 1 is a schematic plan view showing a vehicle drive system and a drive system control system. FIG. 2 is a cross-sectional view showing the configuration of the left and right rear wheel driving force distribution unit. FIG. 3 is a flowchart showing a control routine for generating the yaw moment. FIG. 4 is a control map that defines left and right wheel driving force distribution control areas and left and right wheel braking force distribution areas.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic plan view showing a wheel drive system and a drive system control system of a vehicle 100 to which the first embodiment is applied.

Vehicle 100 is a four-wheel drive vehicle having left front wheel 1L and right front wheel 1R as main drive wheels and left rear wheel 2L and right rear wheel 2R as auxiliary drive wheels. In the present description, “driving force” means torque.

Vehicle 100 includes an internal combustion engine (hereinafter also simply referred to as “engine”) 3 as a drive source. In addition, vehicle 100 includes a transaxle 4 including a transmission and a differential gear device for shifting rotational power from engine 3. Rotational power from the engine 3 is shifted by the transaxle 4 and transmitted to the left and right

front wheels

1L and 1R via the left and right front

wheel axle shafts

5L and 5R.

The vehicle 100 uses a part of the rotational power shifted by the transaxle 4 as a transfer 6, a propeller shaft 7, left and right rear wheel driving force distribution unit (left and right wheel driving force distribution mechanism) 8, and left and right rear

wheel axle shafts

9L and 9R. There is also provided a transmission system for transmitting to the left and right

rear wheels

2L, 2R via the.

The left and right rear wheel driving force distribution unit 8 has a function of distributing and outputting the rotational power transmitted through the propeller shaft 7 to the left and right

rear wheels

2L and 2R. The left and right rear wheel driving force distribution unit 8 includes a center shaft 39 extending in the axial direction of the

axle shafts

9L and 9R between the left and

right axle shafts

9L and 9R. The left and right rear wheel driving force distribution unit 8 further includes a left rear wheel side clutch 11L for connecting and controlling the center shaft 39 and the left rear wheel axle shaft 9L, and between the center shaft 39 and the left rear wheel axle shaft 9R. A right rear wheel side clutch 11R for coupling control. By controlling the fastening force of the left rear wheel side clutch 11L and the right rear wheel side clutch 11R, the driving force is distributed to the left and right

rear wheels

2L, 2R as described above. The detailed configuration of the left and right rear wheel driving force distribution unit 8 will be described later.

The vehicle 100 includes wheel speed sensors 22 that detect the rotational speeds of the left and right

front wheels

1L and 1R and the left and right

rear wheels

2L and 2R. The detection value of each wheel speed sensor 22 is read into a stability control (VDC: Vehicle Dynamics Control) control unit (hereinafter referred to as VDCCU) 26. The VDCCU 26 calculates the vehicle speed based on the average value of the detection values of the wheel speed sensors 22. Further, the VDCCU 26 controls the brake pressure, that is, the braking force, of the brake mechanism 10 provided in each

wheel

1L, 1R, 2L, 2R as stability control. The stability control will be described later.

The vehicle 100 includes a yaw rate / G sensor 23 for detecting a yaw rate and acceleration around a vertical axis passing through the center of gravity of the vehicle 100, a steering angle sensor 24 for detecting a steering wheel steering angle, and an accelerator pedal opening for detecting an accelerator pedal opening. Degree sensor 27. The detection value of the accelerator pedal opening sensor 27 is read into an engine control unit (ENG Control, hereinafter referred to as ENGCU) 25 in the drawing. ENGCU 25 also reads a detection value of a crank angle sensor (not shown) that detects the engine rotation speed. The detection value of the steering angle sensor 24 is read into the ENGCU 25 and the four-wheel drive control unit (4WD Control unit in the figure, hereinafter referred to as 4WDCU) 21.

ENGCU 25, 4WDCU 21 and VDC control unit (VDC control unit) 26 are connected to each other via a communication line 28 of CAN (Controller area network) so as to be capable of bidirectional communication.

FIG. 2 is a cross-sectional view showing the configuration of the left and right rear wheel driving force distribution unit 8. Since the configuration of the left and right rear wheel driving force distribution unit 8 is known, the main part will be briefly described.

The left and right rear wheel driving force distribution unit 8 has a center section housing 3a that is divided in a vertical direction along the axis of the input side hypoid gear 12a of FIG. 2 and that passes through the axis of the center shaft 39. The center section housing 3a includes a center section front housing 38 that houses the input-side hypoid gear 12a and a part of the center shaft 39 and the output-side hypoid gear 12b. Further, the center section housing 3a has a center section rear housing 30 that houses a part of the center shaft 39 and the output side hypoid gear 12b. The center section front housing 38 and the center section rear housing 30 are each divided into an upper side and a lower side along the axis of the input side hypoid gear 12a so that the center shaft 39, the output side hypoid gear 12b and the like can be assembled from the radial direction. It is configured.

The substantially cup-

shaped coupling housings

51 and 52 that respectively house the left rear wheel side clutch 11L and the right rear wheel side clutch 11R are disposed on both sides of the center section housing 3a in the center shaft axial direction. The

coupling housings

51 and 52 are attached by bolts 53 from the side of the center section housing 3a in the center shaft axial direction.

Between the center section front housing 38 and the input-side hypoid gear 12a, a front bearing 34 and a rear bearing 33 that rotatably support the input-side hypoid gear 12a, and a bearing spacer that maintains a space between the front bearing 34 and the rear bearing 33 are provided. 37 are arranged. The input side hypoid gear 12a includes a companion flange 60 connected to the propeller shaft 7 on the front side of the vehicle, and a companion flange nut 61 that fixes the companion flange 60 and the input side hypoid gear 12a. An oil seal 35 and a companion flange dust shield 36 that covers the oil seal 35 from the opening side of the center section front housing 38 are disposed between the companion flange 60 and the center section front housing 38.

A center shaft 39 is rotatably supported by the center section housing 3a via

bearings

31 and 32. The output side hypoid gear 12b is attached to the center shaft 39 by spline fitting. A left shim 41 that adjusts the axial position of the bearing 31 is attached to the center section housing 3a outside the bearing 31 in the axial direction (left side in FIG. 2). Similarly, a right shim 42 that adjusts the axial position of the bearing 32 is attached to the center section housing 3a outside the bearing 32 in the axial direction (right side in FIG. 2).

The center shaft 39 is a hollow, substantially cylindrical member, and has shaft fitting

portions

39L and 39R formed with splines on the inner periphery of both ends. A coupling input shaft 111L that is integral with the left rear wheel side clutch 11L and has a spline on the outer periphery thereof, and a coupling input shaft 111R that is also integral with the right rear wheel side clutch 11R are connected to the shaft

fitting portions

39L and 39R. Are inserted along the axial direction. As a result, the shaft

fitting portions

39L and 39R mesh with the outer periphery of the

coupling input shaft

111L and 111R, and the center shaft 39 is connected to the left rear wheel side clutch 11L and the right rear wheel side clutch 11R.

Between the left rear wheel side clutch 11L and the right rear wheel side clutch 11R, and the

coupling input shafts

111L and 111R, pedestal portions 11L1 and 11R1 having diameters larger than the

coupling input shafts

111L and 111R are formed. . Oil seals 43 and 44 are attached between the pedestals 11L1 and 11R1 and the center section housing 3a. Thereby, the accommodation parts of the left rear wheel side clutch 11L and the right rear wheel side clutch 11R are liquid-tight.

Further, an electronically controlled coupling (not shown) is provided between the rear end of the propeller shaft 7 extending from the transfer 6 to the rear of the vehicle and the bevel gear type final reduction gear 12 composed of the input side hypoid gear 12a and the output side hypoid gear 12b. Intervened. The electronically controlled coupling electronically controls the pressing force of the multi-plate clutch, so that the ratio of the front wheel driving torque and the rear wheel driving torque, that is, the driving torque of the left and right

front wheels

1L, 1R and the driving torque of the left and right

rear wheels

2L, 2R. And the ratio can be changed.

With the above configuration, part of the rotational power of the engine 3 is transmitted from the transfer 6 to the center shaft 39 via the propeller shaft 7, the electronically controlled coupling, and the final reduction gear 12. Then, it is distributed from the center shaft 39 to the left and right

rear wheels

2L, 2R according to the respective fastening forces of the left rear wheel side clutch 11L and the right rear wheel side clutch 11R. The 4WDCU 21 executes this fastening force control.

Note that each of the left rear wheel side clutch 11L and the right rear wheel side clutch 11R is an electromagnetic type in which the fastening force is determined according to the supply current. Supply to the

clutches

11L and 11R is such that the engagement forces of the

clutches

11L and 11R are the engagement forces corresponding to the target drive forces of the left and right

rear wheels

2L and 2R calculated in the left and right wheel drive force distribution control described later. Control the current.

The 4WDCU 21 reads the detection values of the wheel speed sensor 22, the yaw rate / G sensor 23, and the steering angle sensor 24 via the CAN communication line 28. Further, the 4WDCU 21 reads the output torque Te and the engine rotation speed of the engine 3 calculated by the ENGCU 25 and the transmission ratio of the transaxle 4 calculated by a transmission control unit (not shown) via the CAN communication line 28.

The 4WDCU 21 executes driving force distribution control to the

front wheels

1L and 1R and the

rear wheels

2L and 2R in order to improve the start performance and acceleration performance of the vehicle. The 4WDCU 21 basically distributes the total driving force to the left and right

front wheels

1L and 1R which are main driving wheels. Hereinafter, traveling in this state is referred to as front wheel drive traveling. When the left and right

front wheels

1L and 1R slip, etc., the 4WDCU 21 distributes a part of the driving force to the left and right

rear wheels

2L and 2R. Hereinafter, traveling in this state is referred to as four-wheel drive traveling. The distribution of driving force to the

front wheels

1L and 1R and the

rear wheels

2L and 2R is determined according to changes in road surface conditions, vehicle turning conditions, wheel slip conditions, and the like.

Also, even if the left and right

front wheels

1L and 1R are not slipping, the 4WDCU 21 distributes the driving force to the left and right

rear wheels

2L and 2R to improve the turning performance when the vehicle 100 is turning. At that time, the 4WD CU 21 executes not only front / rear wheel driving force distribution but also left / right wheel driving force distribution control by controlling the fastening force of the left rear wheel side clutch 11L and the right rear wheel side clutch 11R. For example, by increasing the distribution of driving force to the outer wheel during turning, a yaw moment that turns inward is generated, and turning performance is improved. The 4WDCU 21 performs control so that the driving force transmitted to the rear wheels increases as the yaw moment necessary for turning increases.

Furthermore, the 4WDCU 21 may execute the left / right driving force distribution control during turning in cooperation with the left / right wheel braking force distribution control executed by the VDCCU 26. The left and right wheel braking force distribution control is one of the stability controls executed by the VDCCU 26. Stability control (VDC: Vehicles Dynamics Control) determines the distribution of braking force to the left and right

front wheels

1L and 1R and the left and right

rear wheels

2L and 2R in accordance with the turning state for the purpose of stabilizing vehicle behavior and improving turning performance. It is control to do. For example, the VDCCU 26 detects an understeer tendency or an oversteer tendency of a vehicle that is turning based on the steering angle, the vehicle speed, the lateral acceleration, and the like in order to stabilize the vehicle behavior, and suppresses the detected tendency. Control power and braking force distribution. For example, during an oversteer tendency, a yaw moment that turns outward by applying a braking force to the front and rear outer wheels during turning is generated to suppress oversteer. When the vehicle is understeering, a braking force is applied to the rear outer wheel during turning to generate a yaw moment that turns inward to suppress understeer.

Note that the understeer tendency is a turning tendency in which the vehicle traveling direction deviates outside the turning circle when the centrifugal force of the vehicle exceeds the ground friction force of the front wheels during turning. The oversteer tendency is a turning tendency in which the vehicle traveling direction deviates to the inside of the turning circle due to the centrifugal force of the vehicle exceeding the ground frictional force of the rear wheel during turning.

Also, the VDCCU 26 executes left and right wheel braking force distribution control for generating a yaw moment by applying different braking forces to the outer wheel and the inner wheel during turning, regardless of the brake pedal depression force, in order to improve turning performance. For example, as with the suppression of understeer, turning performance can be improved by generating a yaw moment that applies a braking force to the rear outer wheel and responds inward during turning.

Next, left and right wheel driving force distribution control and left and right wheel braking force distribution control will be described.

According to the left / right braking force distribution control, understeer and oversteer can be suppressed and turning performance can be improved as described above. Further, in the left and right wheel braking force distribution control, the vehicle inevitably decelerates due to the nature of the control, so that it is possible to improve the safety when turning at an overspeed. However, such deceleration of the vehicle may give the driver a feeling of strangeness. In particular, there may be a feeling of deceleration in a driving scene in which the vehicle yaw moment is generated to the left and right with the lateral G not being large, such as when the driving lane is changed by a quick steering operation.

On the other hand, according to the left and right wheel driving force distribution control, the turning performance can be improved as described above. However, the left and right wheel driving force distribution control gives the driver a sense of acceleration because the vehicle is hardly decelerated due to the nature of the control, and the driving efficiency is increased by distributing appropriate driving force to the left and right wheels. In particular, the higher the side G is, the more the driver feels uncomfortable with this acceleration feeling.

Therefore, in this embodiment, the 4WD CU 21 executes the left and right wheel driving force distribution control and the left and right wheel braking force distribution control in a coordinated manner in order to improve the turning performance of the vehicle without giving the driver a sense of incongruity.

FIG. 3 is a flowchart showing a control routine executed by the 4WDCU 21. “TV” in the figure is an abbreviation of “Torque Vectoring”, and means left and right wheel driving force distribution control. Similarly, “Brake” means left and right wheel braking force distribution control. Hereinafter, it demonstrates according to the step of a flowchart.

In step S10, the 4WD CU 21 calculates an estimated lateral acceleration (hereinafter also referred to as an estimated lateral G). The estimated lateral G is lateral acceleration during a turn estimated based on the vehicle running state. The actual lateral acceleration may be detected by a lateral acceleration sensor. However, in order to eliminate the influence of the time delay from when the steering is steered until the lateral acceleration is generated and detected by the sensor, in the present embodiment, the lateral acceleration is detected. Use an estimate of acceleration. The 4WDCU 21 calculates the estimated lateral G using the wheel steering angle, vehicle speed, and yaw rate. 4WDCU21 calculates the steering angle of a wheel based on the detected value of the steering angle sensor 24 which detects the steering angle of a steering wheel. The 4WDCU 21 reads the average value of the detection values of the wheel speed sensors 22 calculated by the VDCCU 26 as the vehicle speed. The 4WDCU 21 reads the detection value of the yaw rate / G sensor 23 as the yaw rate. Since the method for calculating the estimated lateral G based on these values is known, the description thereof is omitted.

In step S20, the 4WDCU 21 calculates a target rear yaw moment gain. The target rear yaw moment gain refers to the yaw moment generated by the left and right wheel driving force distribution control in order to generate the yaw moment necessary for turning according to the steering of the driver (hereinafter referred to as the target yaw moment). It is calculated by dividing by etc. The greater the yaw moment gain, the greater the force required to turn the vehicle.

In step S30, the 4WD CU 21 defines the left and right wheel driving force distribution control region and the left and right wheel braking force distribution control region based on the control map shown in FIG. When the target lateral G is large, the necessary yaw moment also increases. However, since giving a yaw moment greater than a predetermined value may reduce the vehicle stability during the turn, the control map shows the turning performance and the vehicle. It is set to achieve both stability. For example, when the estimated lateral G is 0.8 G and the target yaw moment gain is 0.4, both the left and right wheel driving force distribution control and the left and right wheel braking force distribution control are performed from the control map. Execute. For example, when the estimated lateral G is 0.3 G and the target yaw moment gain is 0.2, only the left and right wheel driving force distribution control is performed based on the control map.

In step S40, the 4WDCU 21 determines to execute the left and right wheel driving force distribution control and the left and right wheel braking force distribution control in a coordinated manner. In step S60, the 4WD CU 21 sets the distribution between the yaw moment generated by the left and right wheel driving force distribution control and the yaw moment generated by the left and right wheel braking force distribution control.

The 4WDCU 21 calculates a yaw moment (target rear yaw moment) to be generated by distributing the driving force to the left and right

rear wheels

2L, 2R in order to eliminate the difference between the target yaw moment and the actual yaw moment yaw rate. Specifically, the 4WDCU 21 first transmits the drive to the left and right

rear wheels

2L, 2R via the electronically controlled coupling based on the engine speed, the intake air amount, and the shift position of the transmission in the transaxle 4. Calculate the force. Next, the 4WDCU 21 calculates a target yaw moment when performing a turn according to the steering of the driver based on the vehicle speed and the steering angle. Then, the 4WDCU 21 calculates a yaw moment (target rear yaw moment) to be generated by distributing the driving force to the left and right

rear wheels

2L, 2R in order to eliminate the difference between the target yaw moment and the actual yaw moment.

If the restored yaw moment changes due to factors such as changes in vehicle speed or vehicle skidding, the target rear yaw moment calculated as described above becomes excessively large relative to the restored yaw moment, resulting in unstable controllability. There is. In order to prevent this, the target rear yaw moment may be corrected based on the steering steering angular velocity and the lateral acceleration change rate. Further, the vehicle body behavior may be disturbed due to slipping of the wheel during turning. Therefore, the driving force distribution to the left and right

rear wheels

2L and 2R may be corrected based on the slip ratio of the turning wheel.

The distribution of the yaw moment generated by the left and right wheel driving force distribution control and the yaw moment generated by the left and right wheel braking force distribution control is such that the yaw moment generated by the left and right wheel braking force distribution control increases as the target rear yaw moment increases. Set to. The specific distribution differs depending on the specifications of the vehicle 100 such as the wheel base, and therefore is set according to the specification of each vehicle.

On the other hand, in step S50, the 4WDCU 21 sets the driving force distribution of the left and

right wheels

2L and 2R so as to generate the target rear yaw moment only by the left and right wheel driving force distribution control.

Next, the function and effect of this embodiment will be described.

In the present embodiment, a 4WDCU (yaw moment) that controls the yaw moment of a vehicle 100 that includes a left and right rear wheel driving force distribution unit (left and right wheel driving force distribution mechanism) 8 and a brake mechanism (left and right wheel braking force distribution mechanism) 10. A control device 21 is provided. When the lateral acceleration generated during the turning of the vehicle is smaller than a predetermined lateral acceleration set in advance, the 4WDCU 21 generates a yaw moment necessary for the turning of the vehicle using only the left and right rear wheel driving force distribution unit 8. That is, in a turn with a small lateral acceleration, the vehicle does not decelerate and does not give the driver a sense of incongruity because the vehicle actively turns in response to the left and right wheel driving force distribution control.

In the present embodiment, when the lateral acceleration generated during turning of the vehicle 100 is equal to or greater than a predetermined lateral acceleration, the yaw moment necessary for turning the vehicle is obtained using the left and right rear wheel driving force distribution unit 8 and the brake mechanism 10. generate. In turning with a large lateral acceleration, the left and right wheel braking force distribution control is also performed, so that the driver can turn without giving an excessive feeling of acceleration to the driver and without decelerating.

In the above-described embodiment, the case where the driving force distribution to the left and right

rear wheels

2L and 2R is controlled using the wet multi-plate clutch type left and right rear wheel driving force distribution unit 8 is described, but the present invention is not limited to this. Absent. For example, a configuration in which the left and right power distribution mechanism is provided on the front wheels, or an electric motor in each of the left and right

rear wheels

2L and 2R, and a driving force of each electric motor may be controlled.

The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

Claims

A left and right wheel driving force distribution mechanism for changing the driving force distribution of the left and right wheels of the vehicle;
Left and right wheel braking force distribution mechanism for changing the braking force distribution of the left and right wheels of the vehicle;
In a yaw moment control device for controlling the yaw moment of a vehicle comprising:
A yaw moment control device for generating a yaw moment necessary for turning of a vehicle only by the left and right wheel driving force distribution mechanism when a lateral acceleration generated during the turning of the vehicle is smaller than a predetermined lateral acceleration set in advance.
In the yaw moment control device according to claim 1,
When the lateral acceleration generated during the turning of the vehicle is equal to or greater than the predetermined lateral acceleration, the yaw moment necessary for the turning of the vehicle is generated using the left and right wheel driving force distribution mechanism and the left and right wheel braking force distribution mechanism. Yaw moment control device.
A left and right wheel driving force distribution mechanism for changing the driving force distribution of the left and right wheels of the vehicle;
Left and right wheel braking force distribution mechanism for changing the braking force distribution of the left and right wheels of the vehicle;
In a yaw moment control method for controlling a yaw moment of a vehicle comprising:
A yaw moment control method for generating a yaw moment necessary for turning of a vehicle only by the left and right wheel driving force distribution mechanism when a lateral acceleration generated during the turning of the vehicle is smaller than a predetermined lateral acceleration set in advance.