JP4962321B2 - Vehicle motion control system - Google Patents

Description

  The present invention relates to a vehicle motion control system, and more particularly, durability of driving force distribution control when traction control by driving force distribution control is performed in a situation where a wheel speed difference between left and right driving wheels tends to be large. The present invention relates to a vehicle motion control system that can suppress deterioration of the vehicle.

  Recent vehicle motion control systems include a driving force distribution control device that can control the driving force distribution to the left and right drive wheels. This drive force distribution control device has a control differential, and controls the drive force distribution to the left and right drive wheels by actively providing a left-right difference in the differential output shaft speed (drive force distribution control).

  As a conventional vehicle motion control system related to this problem, a technique described in Patent Document 1 is known. A conventional vehicle motion control system (a vehicle left / right driving force adjusting device) transfers the driving force between the left and right rotating shafts between the left wheel rotating shaft and the right wheel rotating shaft in the vehicle. A driving force transmission control mechanism capable of adjusting the driving force of the left and right wheels is provided, and the driving force transmission control mechanism is connected to one of the left and right rotating shafts and is connected to the one rotating shaft side. Is interposed between the other rotating shaft side of the left and right rotating shafts and the output part side of the shifting mechanism. A transmission capacity variable control torque transmission mechanism capable of transmitting a driving force between the left and right rotating shafts when engaged, and a control means for controlling the engagement state of the transmission capacity variable control torque transmission mechanism. The rotational speed ratio of the left and right wheels is When the rotation speed on the output side of the speed mechanism and the rotation speed on the other rotating shaft side become larger than the changing boundary value, the engagement of the transmission capacity variable control type torque transmission mechanism is released. Control stop means for stopping the driving force transmission control is provided.

Japanese Patent No. 2848126

  Also, in recent vehicle motion control systems, control is performed to prevent tire slip when starting or accelerating the vehicle (traction control). In particular, when starting on a straddle road (running roads with different friction coefficients on the road surface contacting the tires of the left and right drive wheels), control is performed to suppress wheel slip on the road surface side with a low friction coefficient. (Straddle traction control). Such control is realized by the driving force distribution control device performing the driving force distribution control.

  However, in straddle traction control, since the driving force distribution control is performed when the wheel applied to the road surface side having a low friction coefficient slips, the wheel speed difference between the left and right driving wheels tends to increase. Then, when torque movement is performed in the driving force distribution control, the load on the driving force distribution control device becomes excessive, the durability of the driving force distribution control device deteriorates, and the driving force distribution control device is damaged. (Such as clutch wear or seizure).

  For this reason, in the conventional vehicle motion control system, traction control by the driving force distribution control is not performed in a situation where the wheel speed difference between the left and right driving wheels tends to be large, such as when starting on a crossing road.

  Therefore, the present invention has been made in view of the above, and the driving force distribution control is performed when the traction control by the driving force distribution control is performed in a situation where the wheel speed difference between the left and right driving wheels tends to increase. An object of the present invention is to provide a vehicle motion control system capable of suppressing deterioration in durability of the vehicle.

  In order to achieve the above object, a vehicle motion control system according to the present invention applies driving force to left and right wheels and controls driving force distribution to the left and right wheels (hereinafter referred to as driving force distribution control). A force distribution control device and a braking force control device capable of independently controlling the braking force of the left and right wheels (hereinafter referred to as braking force control) are provided, and traction control for suppressing wheel slip is performed. A vehicle motion control system comprising road surface μ information acquisition means for acquiring information on a friction coefficient of a road surface at a current position of the wheel (hereinafter referred to as road surface μ information), and an accelerator opening based on the road surface μ information The upper limit value is set, and the traction control by the driving force distribution control is performed only when the current accelerator opening is equal to or smaller than the upper limit value.

  In this vehicle motion control system, since traction control is performed by driving force distribution control, suitable vehicle motion control (for example, smooth and efficient start on a crossing road) is realized. At this time, the upper limit value of the accelerator opening is set based on the road surface μ information, and the traction control by the driving force distribution control is performed only when the current accelerator opening is equal to or smaller than the upper limit value. That is, when the current accelerator opening is larger than the predetermined upper limit value, the left and right drive wheels are likely to be highly differential, and traction control by drive force distribution control is prohibited. Thereby, there exists an advantage by which the deterioration of the durability of the control differential resulting from the difference between the left and right wheel speeds is suppressed.

  In the vehicle motion control system according to the present invention, the road surface μ information acquisition means acquires the road surface μ information by vehicle-to-vehicle communication or from an external facility.

  In this vehicle motion control system, the road surface μ information is obtained with high accuracy, and thus there is an advantage that vehicle motion control is appropriately performed.

  In the vehicle motion control system according to the present invention, when the current accelerator opening exceeds the upper limit value, the traction control by the braking force control is performed.

  In this vehicle motion control system, when the current accelerator opening is larger than a predetermined upper limit value, traction control by driving force distribution control is prohibited. In such a configuration, since the traction control by the braking force control is performed when the left and right drive wheels are likely to be highly differential, deterioration of the durability of the control differential due to the difference between the left and right wheel speeds is effectively suppressed. There are advantages.

  In the vehicle motion control system according to the present invention, the traction control is performed at the time of starting on a traveling road where the friction coefficients of road surfaces contacting the left and right wheel tires are different.

  On the lane, smooth and efficient start is required, while the left and right drive wheels tend to be highly differential. In this respect, in this vehicle motion control system, the traction control by the driving force distribution control and the traction control by the braking force control are appropriately selected according to the relationship between the current accelerator opening and the upper limit value. As a result, the deterioration of the durability of the control differential due to the difference between the left and right wheel speeds is effectively suppressed, and the driving force distribution control is used as much as possible to achieve smooth and efficient start. is there.

  In the vehicle motion control system according to the present invention, the traction control is performed by the driving force distribution control, so that suitable vehicle motion control (for example, smooth and efficient start on a crossing road) is realized. At this time, the upper limit value of the accelerator opening is set based on the road surface μ information, and the traction control by the driving force distribution control is performed only when the current accelerator opening is equal to or smaller than the upper limit value. That is, when the current accelerator opening is larger than the predetermined upper limit value, the left and right drive wheels are likely to be highly differential, and traction control by drive force distribution control is prohibited. Thereby, there exists an advantage by which the deterioration of the durability of the control differential resulting from the difference between the left and right wheel speeds is suppressed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a block diagram showing a vehicle motion control system according to an embodiment of the present invention. 2 and 3 are a flowchart (FIG. 2) and an explanatory diagram (FIG. 3) showing the operation of the vehicle motion control system shown in FIG.

[Vehicle motion control system]
The vehicle motion control system 1 controls the motion or behavior of the vehicle 10 (hereinafter referred to as vehicle motion control) to prevent the vehicle 10 from spinning, drifting out, wheel slipping, and the like. The vehicle motion control system 1 includes a driving force distribution control device 2, a braking force control device 3, and a control system 4 (see FIG. 1). In this embodiment, the left rear wheel 11RL and the right rear wheel 11RR of the vehicle 10 are drive wheels of the vehicle 10, and the left front wheel 11FL and the right front wheel 11FR are steering wheels of the vehicle 10.

  The driving force distribution control device 2 is a device that distributes the driving force to the left and right driving wheels 11 RR and 11 RL, and includes, for example, a control differential 21. In the driving force distribution control device 2, when the engine 12 generates driving force, the driving force is transmitted to the control differential 21 through the transmission (reduction gear) 13, the propeller shaft 14 and the viscous coupling 15. Then, this driving force is distributed to the left and right drive shafts 22RR, 22RL by the control differential 21, and transmitted to the drive wheels 11RR, 11RL. At this time, the distribution ratio of the driving force to the driving wheels 11RR and 11RL is controlled (driving force distribution control). In this embodiment, the driving force distribution control device 2 is disposed only on the rear wheels 11RR and 11RL of the vehicle 10. The vehicle motion control system 1 may be applied to a 2WD (two-wheel drive) vehicle or a 4WD (four-wheel drive) vehicle. For example, the driving force distribution control device 2 may be installed on the rear wheels of the 2WD vehicle (rear wheel drive), or the driving force distribution control device 2 may be installed only on the rear wheels of the 4WD vehicle.

  The braking force control device 3 is a device that controls the braking force applied to the wheels 11FR to 11RL, and includes a hydraulic circuit 31, wheel cylinders 32FR to 32RL, a brake pedal 33, and a master cylinder 34. The hydraulic circuit 31 includes a reservoir, an oil pump, various valves, and the like (not shown). The braking force control device 3 applies a braking force to the wheels 11FR to 11RL as follows. That is, (1) during normal operation, when the brake pedal 33 is depressed by the driver, the depression amount is transmitted to the hydraulic circuit 31 via the master cylinder 34. The hydraulic circuit 31 adjusts the hydraulic pressures of the wheel cylinders 32FR to 32RL, so that the wheel cylinders 32FR to 32RL are driven to apply a braking force (braking pressure) to the wheels 11FR to 11RL. On the other hand, at the time of (2) vehicle motion control, the target braking force for each wheel 11FR to 11RL is calculated based on the motion state of the vehicle, and the hydraulic circuit 31 is driven based on this target braking force, and each wheel cylinder 32FR to 32RL. Is controlled (braking force control).

  The control system 4 includes an ECU (Electronic Control Unit) 41, wheel speed sensors 42FR to 42RL that detect wheel speeds of the wheels 11FR to 11RL, a steering angle sensor 43 that detects a steering angle, and a yaw rate sensor that detects a yaw rate. 44, longitudinal acceleration sensor 45 that detects longitudinal acceleration, lateral acceleration sensor 46 that detects lateral acceleration, vehicle speed sensor 47 that detects vehicle speed, accelerator opening sensor 48 that detects accelerator opening, and road surface μ information And a road surface μ sensor 49 for acquiring In the control system 4, the ECU 41 drives the engine 12, the driving force distribution control device 2, and the braking force control device 3 based on the detection results of the sensors 42 to 49. Thereby, total driving force control by the engine 12, driving force distribution control by the driving force distribution control device 2, and braking force control by the braking force control device 3 are performed, and vehicle motion control is performed.

[Vehicle motion control]
In this vehicle motion control system 1, under a situation where the wheel speed difference between the left and right drive wheels 11RR and 11RL is likely to be large (for example, the road where the friction coefficients of the road surfaces contacting the tires of the left and right drive wheels 11RR and 11RL are different) The following traction control is performed at the time of (starting on a crossing road) (see FIG. 2).

  The traction control generally refers to control for preventing tire slip when starting or accelerating the vehicle. For example, when traction control (stretching traction control) is performed when the vehicle 10 starts, slipping of the drive wheels 11RR (11RL) contacting the road surface with a low friction coefficient is suppressed. Further, the acceleration performance of the vehicle is improved by providing a difference in the driving force between the left and right driving wheels 11RR and 11RL. Such traction control is performed when, for example, the difference between the wheel speeds VxRR and VxRL of the left and right drive wheels 11RR and 11RL | VwRR−VwRL | exceeds a predetermined threshold (for example, 1.5 [m / s]). Necessary.

  In the traction control, first, it is determined whether or not information on the friction coefficient μ of the road surface (hereinafter referred to as road surface μ information) at the own wheel position (current position of the drive wheels 11RR and 11RL) can be acquired (ST1). The road surface μ information may be acquired by, for example, (1) other vehicle (a vehicle ahead of the vehicle started at the intersection) by vehicle-to-vehicle communication when the vehicle 10 starts at the intersection, or (2) other The road surface μ information acquired by the vehicle is stored in an external facility such as a traffic light, and may be acquired via the external facility. Further, the road surface μ information is acquired via the road surface μ sensor 49.

  If the road surface μ information cannot be acquired, traction control by braking force control is performed (ST8). Specifically, the traction control is performed by the braking force control device 3 controlling the braking force to the left and right drive wheels 11RR and 11RL. This prevents slipping of the drive wheels 11RR and 11RL. An existing technique can be adopted for traction control only by braking force control.

  On the other hand, when the road surface μ information can be acquired, the road surface μ information is acquired (ST2). Next, accelerator opening Accel_open [%] is acquired via accelerator opening sensor 48 (ST3). Based on the road surface μ information and the accelerator opening Accel_open, the command value targetFx_diff to the driving force distribution control device 2 (control differential 21), the upper limit value Accel_open_max and the lower limit value Accel_open_min of the accelerator opening at the time of driving force distribution control are obtained. Calculated (ST4 and ST5).

At this time, first, an output Fx_rec based on the driver request is calculated by the following formula (1). Note that (μL * WL + μR * WR) is the maximum value of the output Fx that can be output at present. ΜL and μR are friction coefficients of the road surface on which the left and right drive wheels 11RR and 11RL are grounded, and WL and WR are ground loads on the left and right drive wheels 11RR and 11RL.
Fx_rec = (μL * WL + μR * WR) * Accel_open / 100 (1)

Next, the upper limit value Accel_open_max and the lower limit value Accel_open_min of the accelerator opening are calculated by the following mathematical formulas (2) and (3) (ST4).
Accel_open_max = {2 * MIN (μL * WL, μR * WR)} / (μL * WL + μR * WR) * 100 (2)
Accel_open_min = {2 * MIN (μL * WL, μR * WR) + Fx_diff_max} / (μL * WL + μR * WR) * 100 (3)
In Equation (2), {2 * MIN (μL * WL, μR * WR)} is the maximum value of the output Fx when the driving force distribution control is not performed. In Formula (3), {2 * MIN (μL * WL, μR * WR) + Fx_diff_max} is the maximum value of the output Fx when the driving force distribution control is performed. Fx_diff_max is a design maximum value of the control differential 21 (a numerical value defined by the durability of the clutch), and is determined based on predetermined experimental data.

Next, the command value targetFx_diff to the driving force distribution control device 2 when the accelerator opening Accel_open is between the upper limit value Accel_open_max and the lower limit value Accel_open_min is set by the following equation (4) (ST5) (FIG. 5). 3).
targetFx_diff = Fx_rec-2 * MIN (μL * WL, μR * WR) (4)

  Next, it is determined whether or not the current accelerator opening Accel_open is between the upper limit value Accel_open_max and the lower limit value Accel_open_min (ST6). If the current accelerator opening Accel_open is not within this range, traction control by braking force control is performed (ST8). That is, if the traction control by the driving force distribution control is performed when the current accelerator opening Accel_open is larger than the upper limit value Accel_open_max, the left and right driving wheels 11RR and 11RL are likely to be highly differential. Therefore, in such a case, traction control by braking force control is performed. Thereby, deterioration of the durability of the control differential 21 due to the difference between the left and right wheel speeds is suppressed.

  On the other hand, when the current accelerator opening Accel_open is within this range, traction control by drive force distribution control is performed (ST7). In the traction control based on the driving force distribution control, first, a command value targetFx_diff to the driving force distribution control device 2 is calculated based on the current accelerator opening Accel_open (see Formula (4) and FIG. 3). Then, the command value targetFx_diff is input to the driving force distribution control device 2, and driving force distribution control is performed. Thereby, suitable traction control (for example, smooth start of the vehicle 10 on a crossing road) is realized.

[effect]
As described above, in the vehicle motion control system 1, traction control is performed by driving force distribution control, so that suitable vehicle motion control (for example, smooth and efficient start on a crossing road) is realized. At this time, the upper limit value Accel_open_max of the accelerator opening is set based on the road surface μ information (ST3 and ST4), and the traction control by the driving force distribution control is performed only when the current accelerator opening Accel_open is less than or equal to the upper limit value Accel_open_max. (ST6 and ST7) (see FIG. 2). That is, when the current accelerator opening is larger than the predetermined upper limit value Accel_open_max, the left and right drive wheels 11RR, 11RL are likely to be highly differential, and traction control by drive force distribution control is prohibited. Thereby, there exists an advantage by which the deterioration of durability of the control differential 21 resulting from the wheel speed difference between right and left is suppressed.

  Further, in the vehicle motion control system 1, the road surface μ sensor 49 (road surface μ information acquisition means) acquires the road surface μ information by inter-vehicle communication or from the equipment outside the vehicle. In such a configuration, road surface μ information is obtained with high accuracy, and thus there is an advantage that vehicle motion control is appropriately performed.

  In the vehicle motion control system 1, when the current accelerator opening exceeds the upper limit value Accel_open_max, traction control by braking force control is performed (ST6 and ST8) (see FIG. 2). That is, when the current accelerator opening is larger than the predetermined upper limit value Accel_open_max, traction control by driving force distribution control is prohibited. In such a configuration, since the traction control by the braking force control is performed when the left and right drive wheels 11RR and 11RL are likely to be highly differential, the deterioration of the durability of the control differential 21 due to the difference between the left and right wheel speeds is effective. Has the advantage of being suppressed.

  Further, in this vehicle motion control system 1, the traction control is performed at the time of starting on a traveling road (crossing road) where the friction coefficients μR and μL of the road surfaces contacting the tires of the left and right wheels 11RR and 11RL are different. It is preferable. On the crossroads, while smooth and efficient start is required, the left and right drive wheels 11RR and 11RL are likely to be highly differential. Therefore, traction control by driving force distribution control and traction control by braking force control are appropriately selected according to the relationship between the current accelerator opening and the upper limit value Accel_open_max. As a result, the deterioration of the durability of the control differential 21 due to the difference between the left and right wheel speeds is effectively suppressed, and the driving force distribution control is used as much as possible to achieve smooth and efficient start. There is.

  As described above, the vehicle motion control system according to the present invention provides durability of the driving force distribution control when the traction control by the driving force distribution control is performed in a situation where the wheel speed difference between the left and right driving wheels tends to be large. It is useful in that it can suppress the deterioration of sex.

It is a block diagram which shows the vehicle motion control system concerning the Example of this invention. It is a flowchart which shows the effect | action of the vehicle motion control system described in FIG. It is explanatory drawing which shows the effect | action of the vehicle motion control system described in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle motion control system 2 Driving force distribution control apparatus 21 Control differential 22RR, 22RL Drive shaft 3 Braking force control apparatus 31 Hydraulic circuit 32FR-32RL Wheel cylinder 33 Brake pedal 34 Master cylinder 4 Control system 42FR-42RL Wheel speed sensor 43 Steering angle Sensor 44 Yaw rate sensor 45 Longitudinal acceleration sensor 46 Lateral acceleration sensor 47 Vehicle speed sensor 48 Accelerator opening sensor 49 Road surface μ sensor 10 Vehicle 11FR to 11RL Wheel 12 Engine 14 Propeller shaft 15 Viscous coupling

Claims (4)

A driving force distribution control device that applies driving force to the left and right wheels and controls the distribution of driving force to the left and right wheels (hereinafter referred to as driving force distribution control); and the braking force of the left and right wheels independently. A vehicle motion control system including a braking force control device capable of controlling (hereinafter referred to as braking force control) and performing traction control for suppressing wheel slip,
Road surface μ information acquisition means for acquiring information on the friction coefficient of the road surface at the current position of the wheel (hereinafter referred to as road surface μ information) is provided, and an upper limit value of the accelerator opening is set based on the road surface μ information. In addition, the vehicle motion control system in which the traction control by the driving force distribution control is performed only when the current accelerator opening is equal to or less than the upper limit value.   2. The vehicle motion control system according to claim 1, wherein the road surface μ information acquisition unit acquires the road surface μ information through inter-vehicle communication or from a facility outside the vehicle.   The vehicle motion control system according to claim 1 or 2, wherein traction control by the braking force control is performed when a current accelerator opening exceeds the upper limit value.   The vehicle motion control system according to any one of claims 1 to 3, wherein the traction control is performed at the time of starting on a traveling road in which friction coefficients of road surfaces contacting left and right wheel tires are different.

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