JP6388258B2 - Vehicle behavior control device - Google Patents

Description

  The present invention relates to a vehicle behavior control device, and more particularly to a vehicle behavior control device that controls the behavior of a vehicle in which front wheels are steered.

  2. Description of the Related Art Conventionally, there are known devices that control the behavior of a vehicle in a safe direction when the behavior of the vehicle becomes unstable due to slip or the like (such as a skid prevention device). Specifically, it is known to detect that understeer or oversteer behavior has occurred in the vehicle during cornering of the vehicle, and to impart appropriate deceleration to the wheels to suppress them. ing.

  On the other hand, unlike the above-described control for improving the safety in the driving state where the behavior of the vehicle becomes unstable, the acceleration / deceleration linked with the steering operation operated from the daily driving range is automatically performed, and the limit 2. Description of the Related Art A vehicle motion control device that reduces skid in a driving region is known (see, for example, Patent Document 1).

Japanese Patent No. 5193858

  However, in a vehicle equipped with the vehicle motion control device described in Patent Document 1, the front wheel load during steering differs between when the acceleration / deceleration control is activated and when it is not activated, and is generated on the ground contact surface of the front wheel. Since the lateral force is different, the characteristics when the reaction torque transmitted from the road surface to the column shaft via the front wheels changes according to the vehicle speed and the steering angle are also different between when the acceleration / deceleration control is activated and when it is not activated. Therefore, even if the driver tries to operate the steering wheel in the same way, the reaction force (steering weight) when operating the steering wheel is different between when the acceleration / deceleration control is activated and when it is not activated. Will remember.

  The present invention has been made to solve the above-described problems of the prior art, and controls the behavior of the vehicle so that the stability of the vehicle posture and the ride comfort are improved. It is an object of the present invention to provide a vehicle behavior control device capable of suppressing a feeling of strangeness when operating a steering wheel during operation.

In order to achieve the above object, a vehicle behavior control device according to the present invention is a vehicle behavior control device that controls the behavior of a vehicle in which a front wheel is steered, a steering speed acquisition unit that acquires the steering speed of the vehicle, cut when the steering speed during steering becomes more than 0 greater than a predetermined threshold value, the motor that applies a driving force reducing means for reducing the driving force of vehicles, the assist torque to the column shaft that connects the front wheels and the steering wheel If the target assist torque setting means for setting a target assist torque corresponding to the steering of the steering wheel by the driver, when the driving force reducing means is to reduce the driving force of the vehicle, the driving force reducing means of the vehicle a target assist torque increasing means for increasing the target assist torque than not reduce the driving force, and the target assist torque setting means And having a an assist control means for controlling the motor to output the target assist torque set by the target assist torque increasing means.
In the present invention configured as described above, the target assist torque setting means sets the target assist torque in accordance with the steering wheel steering by the driver, and the target assist torque increasing means has the driving force reducing means at the steering speed. Accordingly, when the output torque of the engine is reduced , the driving force reduction means increases the target assist torque more than when the driving force reduction means does not reduce the driving force of the vehicle. Accordingly, the target assist torque is reduced even when the reaction torque transmitted from the road surface through the front wheels to the column shaft is larger during the steering operation than when the output torque reduction control is not performed because the output torque of the engine is reduced accordingly. By increasing the, the steering weight can be suppressed from becoming too heavy, The engine output torque is controlled to improve the stability and riding comfort of both postures, and there is a sense of incongruity when operating the steering wheel between when the engine output torque control is activated and when it is not activated. Can be suppressed.

In the present invention, it is preferable that the target assist torque setting means sets the target assist torque so that the target assist torque decreases as the vehicle speed increases , and the target assist torque increase means increases the target assist torque as the vehicle speed increases . Increase the amount of increase.
In the present invention configured as described above, the target assist torque setting means sets the target assist torque so that the target assist torque decreases as the vehicle speed increases , while the target assist torque increase means increases as the vehicle speed increases . When the driving force reduction means reduces the output torque of the engine according to the steering speed, the amount of increase when the target assist torque is increased is increased, so that the target assist torque is relatively increased due to the relatively high vehicle speed. Even when the reaction force torque transmitted to the column shaft at the time of incision steering increases due to the driving force reduction means reducing the engine output torque, the target assist torque will be increased as the vehicle speed increases. Increasing the amount increases the tendency of the steering to become heavier. The can be suppressed, thereby, between the time of operation during the non-operation of the output torque control of the engine can be reliably prevented that the uncomfortable feeling is caused when operating the steering wheel.

  According to the vehicle behavior control apparatus of the present invention, the steering wheel is controlled between when the behavior control is activated and when it is not activated, while controlling the behavior of the vehicle so that the stability and riding comfort of the vehicle posture is improved. It is possible to suppress a feeling of strangeness when operating.

1 is a block diagram showing an overall configuration of a vehicle equipped with a vehicle behavior control apparatus according to an embodiment of the present invention. 1 is a block diagram showing an electrical configuration of a vehicle behavior control apparatus according to an embodiment of the present invention. It is a schematic perspective view which shows EPAS by embodiment of this invention. It is a flowchart of the engine control process which controls the engine by the vehicle behavior control apparatus by embodiment of this invention. It is a flowchart of the torque reduction amount determination process in which the vehicle behavior control apparatus by embodiment of this invention determines a torque reduction amount. It is the map which showed the relationship between the target additional deceleration and the steering speed which the behavior control apparatus for vehicles by embodiment of this invention determines. FIG. 7A is a time chart showing changes over time in parameters related to engine control when a vehicle equipped with a vehicle behavior control apparatus according to an embodiment of the present invention turns, and FIG. 7A shows a vehicle turning right. FIG. 7B is a schematic diagram showing a change in the steering angle of a vehicle turning right, and FIG. 7C is a diagram showing a change in the steering speed of a vehicle turning right. FIG. 7D is a diagram showing the value of the torque reduction flag set based on the steering speed, and FIG. 7E is a diagram showing the change in the additional deceleration determined based on the steering speed and the torque reduction flag. 7 (f) is a diagram showing a change in the torque reduction amount determined based on the additional deceleration, and FIG. 7 (g) is a change in the final target torque determined based on the basic target torque and the torque reduction amount. FIG. FIG. 8A is a diagram showing vehicle behavior when a vehicle is equipped with a vehicle behavior control device according to an embodiment of the present invention and a vehicle not equipped with the vehicle behavior control, and FIG. FIG. 8B is a diagram showing the change in the steering speed of the vehicle, and FIG. 8C is a line showing the change in the additional deceleration determined based on the steering speed and the torque reduction flag. FIG. 8 (d) is a diagram showing a change in lateral force generated on the front wheel, and FIG. 8 (e) is a diagram showing a change in reaction force torque transmitted from the road surface to the column shaft via the front wheel. It is a flowchart of the assist torque determination process in which the vehicle behavior control apparatus by embodiment of this invention determines target assist torque. It is an amplification factor map referred when the vehicle behavior control apparatus by embodiment of this invention sets target assist torque. It is a correction coefficient map referred when the vehicle behavior control apparatus by embodiment of this invention correct | amends a target assist torque.

  Hereinafter, a vehicle behavior control apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  First, a vehicle equipped with a vehicle behavior control apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of a vehicle equipped with a vehicle behavior control apparatus according to an embodiment of the present invention.

  In FIG. 1, the code | symbol 1 shows the vehicle carrying the vehicle behavior control apparatus by this embodiment. An engine 4 that drives drive wheels (left and right front wheels 2 in the example of FIG. 1) is mounted at the front of the vehicle body. The engine 4 is an internal combustion engine such as a gasoline engine or a diesel engine.

  The vehicle 1 also includes an EPAS (Electric Power Assisted Steering) 8 that assists steering of the steering wheel 6 with an electric motor. The EPAS 8 outputs the rotation angle (steering angle) of the steering wheel 6 to a PCM (Power-train Control Module) 14.

  The vehicle 1 also has an accelerator opening sensor 10 that detects the opening of the accelerator pedal (accelerator opening) and a vehicle speed sensor 12 that detects the vehicle speed. Each of these sensors outputs a detected value to the PCM 14.

Next, the electrical configuration of the vehicle behavior control apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing an electrical configuration of the vehicle behavior control apparatus according to the embodiment of the present invention.
PCM14 by embodiment of this invention is based on the detection signal which the various sensors which detect the driving | running state of the engine 4 output other than the detection signal of the sensors 8-12 mentioned above, each part (for example, throttle valve, A control signal is output to control the turbocharger, variable valve mechanism, ignition device, fuel injection valve, EGR device, and the like.

The PCM 14 includes a basic target torque determination unit 16 that determines a basic target torque based on the driving state of the vehicle 1 including the operation of an accelerator pedal, and torque reduction for adding deceleration to the vehicle 1 based on the steering speed of the steering wheel 6. A torque reduction amount determination unit 18 that determines the amount, a final target torque determination unit 20 that determines the final target torque based on the basic target torque and the torque reduction amount, and an engine that controls the engine 4 to output the final target torque. And a control unit 22.
Each component of the PCM 14 includes a CPU, various programs that are interpreted and executed on the CPU (including a basic control program such as an OS and an application program that is activated on the OS to realize a specific function), a program, It is configured by a computer having an internal memory such as a ROM or RAM for storing various data.
Although details will be described later, the PCM 14 corresponds to a part of the vehicle behavior control device of the present invention, and functions as a steering speed acquisition unit and a driving force reduction unit.

  Next, the EPAS 8 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic perspective view showing the EPAS 8 according to the embodiment of the present invention.

  As shown in FIG. 3, the steering wheel 6 is connected to the upper end of the column shaft 24, and a steering force for operating the steering wheel 6 is transmitted to the column shaft 24. A tie rod 26 is connected to the lower end of the column shaft 24 via a link mechanism, and front wheels 2 (steered wheels) are attached to both ends of the tie rod 26.

A motor 28 is connected to the column shaft 24 via a speed reduction mechanism. The motor 28 applies assist torque to the column shaft 24.
The steering wheel 6 is provided with a steering angle sensor 30 that detects the steering angle of the steering wheel 6. The column shaft 24 is provided with a torque sensor 32 that detects a steering torque acting on the column shaft 24. The motor 28 is provided with a motor angle sensor 34 that detects the rotation angle of the motor 28. Signals output from the steering angle sensor 30, torque sensor 32, and motor angle sensor 34 are input to the assist control unit 36. The assist control unit 36 controls the motor 28 based on signals input from the steering angle sensor 30, the torque sensor 32, and the motor angle sensor 34. Further, the assist control unit 36 outputs the detection value of the steering angle sensor 30 to the PCM 14 and acquires information related to the control of the engine 4 from the PCM 14.
Although details will be described later, the assist control unit 36 corresponds to a part of the vehicle behavior control apparatus according to the present invention, and functions as a target assist torque setting unit, a target assist torque increasing unit, and an assist control unit.

Next, an engine control process performed by the vehicle behavior control apparatus will be described with reference to FIGS.
FIG. 4 is a flowchart of an engine control process in which the vehicle behavior control apparatus according to the embodiment of the present invention controls the engine 4. FIG. 5 is a flowchart illustrating the torque reduction amount determined by the vehicle behavior control apparatus according to the embodiment of the present invention. FIG. 6 is a map showing the relationship between the target additional deceleration and the steering speed determined by the vehicle behavior control apparatus according to the embodiment of the present invention.

The engine control process of FIG. 4 is started and executed repeatedly when the ignition of the vehicle 1 is turned on and the vehicle behavior control device is turned on.
When the engine control process is started, as shown in FIG. 4, in step S <b> 1, the PCM 14 acquires various types of information related to the driving state of the vehicle 1. Specifically, the PCM 14 determines the steering angle detected by the steering angle sensor 30, the accelerator opening detected by the accelerator opening sensor 10, the vehicle speed detected by the vehicle speed sensor 12, and the gear currently set for the transmission of the vehicle 1. The detection signals output by the various sensors described above, including the steps and the like, are acquired as information related to the driving state.

  Next, in step S2, the basic target torque determination unit 16 of the PCM 14 sets a target acceleration based on the driving state of the vehicle 1 including the operation of the accelerator pedal acquired in step S1. Specifically, the basic target torque determination unit 16 determines the current vehicle speed and gear from the acceleration characteristic maps (created in advance and stored in a memory or the like) defined for various vehicle speeds and various gear stages. The acceleration characteristic map corresponding to the step is selected, and the target acceleration corresponding to the current accelerator opening is determined with reference to the selected acceleration characteristic map.

  Next, in step S3, the basic target torque determination unit 16 determines the basic target torque of the engine 4 for realizing the target acceleration determined in step S2. In this case, the basic target torque determination unit 16 determines the basic target torque within the range of torque that the engine 4 can output based on the current vehicle speed, gear stage, road surface gradient, road surface μ, and the like.

  In parallel with the processing of steps S2 and S3, in step S4, the torque reduction amount determination unit 18 determines the torque reduction amount for adding a deceleration to the vehicle 1 based on the steering operation. Execute. The torque reduction amount determination process will be described with reference to FIG.

  As shown in FIG. 5, when the torque reduction amount determination process is started, in step S21, the torque reduction amount determination unit 18 calculates a steering speed based on the steering angle acquired in step S1.

Next, in step S22, the torque reduction amount determination unit 18 determines whether or not the steering speed is greater than a predetermined threshold value T _S1 .
As a result, if the steering speed is greater than the threshold value T _S1 , the process proceeds to step S23, where the torque reduction amount determination unit 18 satisfies a condition for reducing the output torque of the engine 4 in order to add deceleration to the vehicle 1. A torque reduction flag indicating whether or not to be set is set to True (true value) indicating a state in which a condition for reducing torque is satisfied.

  Next, in step S24, the torque reduction amount determination unit 18 acquires the target additional deceleration based on the steering speed. This target additional deceleration is a deceleration to be applied to the vehicle 1 in accordance with the steering operation in order to accurately realize the vehicle behavior intended by the driver.

Specifically, the torque reduction amount determination unit 18 acquires the target additional deceleration corresponding to the steering speed calculated in step S21 based on the relationship between the target additional deceleration and the steering speed shown in the map of FIG. .
The horizontal axis in FIG. 6 indicates the steering speed, and the vertical axis indicates the target additional deceleration. As shown in FIG. 6, when the steering speed is equal to or less than the threshold value T _S1 , the corresponding target additional deceleration is zero. That is, when the steering speed is equal to or less than the threshold value T _S1 , the PCM 14 stops the control (specifically, reduction of the output torque of the engine 4) for adding deceleration to the vehicle 1 based on the steering operation.
On the other hand, when the steering speed exceeds the threshold value T _S1 , the target additional deceleration corresponding to this steering speed gradually _{approaches the} predetermined upper limit value D _max as the steering speed increases. That is, as the steering speed increases, the target additional deceleration increases, and the increase rate of the increase amount decreases. This upper limit value D _max is set to such a deceleration that the driver does not feel that there is a control intervention even if a deceleration is added to the vehicle 1 according to the steering operation (for example, 0.5 m / s ² ≈0). .05G).
Furthermore, when the steering speed is equal to or higher than the threshold value T _S2 larger than the threshold value T _S1 , the target additional deceleration is maintained at the upper limit value D _max .

Next, in step S25, the torque reduction amount determination unit 18 determines the additional deceleration in the current process in a range where the rate of change of the additional deceleration is equal to or less than a threshold value Rmax (for example, 0.5 m / s ³ ).
Specifically, when the change rate from the additional deceleration determined in the previous process to the target additional deceleration acquired in step S24 of the current process is equal to or less than Rmax, the torque reduction amount determination unit 18 determines in step S24. The acquired target additional deceleration is determined as the additional deceleration in the current process.
On the other hand, when the rate of change from the additional deceleration determined in the previous process to the target additional deceleration acquired in step S24 of the current process is greater than Rmax, the torque reduction amount determination unit 18 adds the value determined in the previous process. A value changed by the rate of change Rmax from the acceleration to the deceleration is determined as the additional deceleration in the current process.

  Next, in step S26, the torque reduction amount determination unit 18 determines the torque reduction amount based on the current additional deceleration determined in step S25. Specifically, the torque reduction amount determination unit 18 determines the torque reduction amount required to realize the current additional deceleration based on the current vehicle speed, gear stage, road surface gradient, etc. acquired in step S1. To do.

In step S22, if the steering speed is not greater than the threshold value T _S1 (is equal to or less than the threshold value T _S1 ), the process proceeds to step S27, where the torque reduction amount determining unit 18 The torque reduction flag indicating whether or not the condition for reducing the output torque is satisfied is set to False (false value) indicating that the condition for reducing the torque is not satisfied.

  After step S26 or S27, the torque reduction amount determination unit 18 ends the torque reduction amount determination processing and returns to the main routine.

  Returning to FIG. 4, after performing the processes of steps S2 and S3 and the torque reduction amount determination process of step S4, in step S5, the final target torque determination unit 20 performs the process of step S4 from the basic target torque determined in step S3. The final target torque is determined by subtracting the torque reduction amount determined in the torque reduction amount determination process.

Next, in step S6, the engine control unit 22 controls the engine 4 to output the final target torque set in step S5. Specifically, the engine control unit 22 performs various state quantities (for example, air filling amount, fuel, etc.) required to realize the final target torque based on the final target torque set in step S5 and the engine speed. The injection amount, the intake air temperature, the oxygen concentration, etc.) are determined, and each actuator that drives each component of the engine 4 is controlled based on the state quantities. In this case, the engine control unit 22 sets a limit value or a limit range according to the state quantity, and sets a control amount for each actuator such that the state value complies with the limit value or the limit range. To do.
After step S6, the PCM 14 ends the engine control process.

  Next, an example of engine control of the vehicle behavior control apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 7 is a time chart showing temporal changes in parameters related to engine control when the vehicle 1 equipped with the vehicle behavior control apparatus according to the embodiment of the present invention turns.

  FIG. 7A is a plan view schematically showing the vehicle 1 that makes a right turn. As shown in FIG. 7A, the vehicle 1 starts turning right from position A and continues turning right from position B to position C with a constant steering angle.

FIG. 7B is a diagram showing changes in the steering angle of the vehicle 1 that turns right as shown in FIG. In FIG. 7B, the horizontal axis indicates time, and the vertical axis indicates the steering angle.
As shown in FIG. 7B, rightward steering is started at the position A, and the rightward steering angle is gradually increased by performing the steering addition operation, and the rightward steering angle is maximized at the position B. It becomes. Thereafter, the steering angle is kept constant up to position C (steering holding).

FIG.7 (c) is a diagram which shows the change of the steering speed of the vehicle 1 which turns right as shown in FIG.7 (b). In FIG. 7B, the horizontal axis indicates time, and the vertical axis indicates the steering speed.
The steering speed of the vehicle 1 is expressed by time differentiation of the steering angle of the vehicle 1. That is, as shown in FIG. 7C, when the rightward steering is started at the position A, a rightward steering speed is generated, and the steering speed is kept substantially constant between the position A and the position B. Thereafter, the rightward steering speed decreases, and when the rightward steering angle becomes maximum at the position B, the steering speed becomes zero. Further, the steering speed remains zero while the rightward steering angle is maintained from position B to position C.

FIG. 7D is a diagram showing the truth value of the torque reduction flag set based on the steering speed. In FIG. 7D, the horizontal axis indicates time, and the vertical axis indicates the true / false value of the torque reduction flag.
As shown in FIG. 7D, before the rightward steering is started at the position A, the torque reduction flag is set to False. When rightward steering is started at position A, the torque reduction flag changes from False to True when the steering speed exceeds the threshold value T _S1 . Thereafter, as the vehicle approaches the position B, the steering speed decreases. When the steering speed becomes equal to or less than the threshold value T _S1 , the torque reduction flag changes from True to False.

FIG. 7E is a diagram showing changes in the additional deceleration determined based on the steering speed and the torque reduction flag. The horizontal axis in FIG.7 (e) shows time and a vertical axis | shaft shows an additional deceleration.
As described with reference to FIG. 5, when the steering speed is larger than the threshold value T _S1 in step S22 (that is, when the torque reduction flag is True), the torque reduction amount determination unit 18 is based on the steering speed in step S24. Get target additional deceleration. Subsequently, in step S25, the torque reduction amount determination unit 18 determines the additional deceleration in each processing cycle in a range where the increase rate of the additional deceleration is equal to or less than the threshold value Rmax.

  As shown in FIG. 7 (e), the additional deceleration starts to increase when the torque reduction flag is switched from False to True, and is maintained substantially constant between the position A and the position B, and thereafter the steering speed is increased. It decreases according to the decrease, and becomes 0 when the torque reduction flag is switched from True to False.

FIG. 7F is a diagram showing changes in the torque reduction amount determined based on the additional deceleration shown in FIG. In FIG. 7F, the horizontal axis indicates time, and the vertical axis indicates the torque reduction amount.
As described above, the torque reduction amount determination unit 18 determines the torque reduction amount necessary for realizing the additional deceleration based on parameters such as the current vehicle speed, gear stage, road surface gradient, and the like. Therefore, when these parameters are constant, the torque reduction amount is determined so as to change in the same manner as the change of the additional deceleration shown in FIG.

FIG. 7G is a diagram showing changes in the final target torque determined based on the basic target torque and the torque reduction amount. In FIG. 7G, the horizontal axis indicates time, and the vertical axis indicates torque. Moreover, the broken line in FIG.7 (g) shows a basic target torque, and a continuous line shows a final target torque.
As described with reference to FIG. 4, the final target torque determination unit 20 subtracts the torque reduction amount determined in the torque reduction amount determination process in step S <b> 4 from the basic target torque determined in step S <b> 3. Determine the target torque.
That is, as shown in FIG. 7G, while the torque reduction flag is set to True between the position A and the position B, the final target torque is reduced from the basic target torque by the amount of torque reduction, Since deceleration corresponding to the torque reduction occurs in the vehicle 1, load movement to the front wheels 2 occurs. As a result, the frictional force between the front wheel 2 and the road surface increases, and the cornering force of the front wheel 2 increases.

  Here, referring to FIG. 8, when the control for reducing the output torque of the engine 4 according to the steering speed is performed by the vehicle behavior control apparatus according to the embodiment of the present invention, and when the output torque reduction control is not performed. The difference in the operational feeling of the steering wheel 6 will be described.

  In order to evaluate how the operational feeling of the steering wheel 6 differs depending on whether or not the output torque reduction control is performed by the vehicle behavior control device, the present inventors have changed from a straight traveling state to a turning state. Various parameters related to the vehicle behavior when traveling through a single corner that again goes straight through the vehicle are calculated by simulation for each of the cases where the output torque reduction control is performed and not performed by the vehicle behavior control device.

8A is a diagram showing changes in the steering angle of the vehicle, FIG. 8B is a diagram showing changes in the steering speed of the vehicle, and FIG. 8C is determined based on the steering speed and the torque reduction flag. FIG. 8 (d) is a diagram showing a change in lateral force generated on the front wheel 2, and FIG. 8 (e) is a diagram showing the change from the road surface to the column shaft via the front wheel. It is a diagram which shows the change of the transmitted reaction torque.
8A to 8C and 8E, a solid line indicates a case where the output torque reduction control is performed by the vehicle behavior control device, and a broken line indicates a case where the output torque reduction control is not performed. In FIG. 8D, the solid line indicates the change in lateral force generated on the front wheel 2 outside the turn when the vehicle behavior control device performs the output torque reduction control, and the broken line performs the output torque reduction control. The change in lateral force generated on the front wheel 2 outside the turn when there is not, the alternate long and short dash line indicates the change in lateral force generated on the front wheel 2 inside the turn when the output torque reduction control is performed, and the two-dot chain line indicates the output A change in lateral force generated on the front wheel 2 inside the turn when torque reduction control is not performed is shown.

  As shown in FIGS. 8A and 8B, at the time of turning steering in which the steering angle increases, the steering speed increases almost at the same time as the vehicle enters the corner and the steering angle starts to increase. Subsequently, as the steering angle approaches the maximum value (ie, the vehicle approaches the minimum point of curvature radius at the corner), the steering speed decreases toward zero. As described above, while the steering speed is generated, the torque reduction flag is set to True, and the output torque is reduced according to the steering speed. Therefore, as shown by the solid line in FIG. Speed occurs. In FIG. 8 (c), the vehicle is accelerated at the time of the switching back operation in which the steering angle is decreased in order to cancel the deceleration of the vehicle due to the reduction of the driving torque.

  As shown in FIG. 8C, when deceleration occurs in the vehicle due to the reduction of the output torque according to the steering speed during the turning steering, the load movement from the rear part of the vehicle to the front part is caused according to the deceleration. As a result, the vertical load on the front wheel 2 increases. When the vertical load on the front wheel 2 increases, the frictional force on the ground contact surface of the front wheel 2 increases, so that the lateral force generated on the ground contact surface of the front wheel 2 increases. That is, as shown in FIG. 8 (d), the lateral force generated on the front wheels 2 becomes larger than when the output torque reduction control is not performed.

  It is known that the magnitude of the reaction torque transmitted from the road surface to the column shaft 24 via the front wheel 2 is proportional to the lateral force generated on the front wheel 2 in a tire linear region where the slip angle of the front wheel 2 is relatively small. Yes. Therefore, when deceleration occurs in the vehicle due to the reduction of the output torque according to the steering speed during the turning steering, the lateral force generated on the front wheels 2 increases, and as shown in FIG. 8 (e), the lateral force increases. Accordingly, the reaction force torque transmitted to the column shaft 24 increases. That is, when the output torque reduction control is performed by the vehicle behavior control device, the steering weight at the time of turning steering becomes heavier than when the output torque reduction control is not performed, so that a sense of incongruity occurs.

Further, as shown in FIGS. 8A and 8B, the steering speed becomes 0 or a negative value at the time of steering holding at which the steering angle is held and at the time of switchback steering at which the steering angle is reduced. . At this time, the torque reduction flag is set to False, and output torque reduction control according to the steering speed is not performed.
Therefore, the lateral force generated on the front wheel 2 during the steering holding and the turning-back steering does not increase as when the output torque reduction control is performed during the turning steering. Further, since the output torque reduction control at the time of turning steering is performed, the vehicle speed at the time of steering holding and at the time of turning back steering is lower than that at the time of turning steering, so that the front wheels 2 are required to turn the vehicle. Lateral force decreases. As a result, as shown in FIG. 8E, the reaction torque transmitted to the column shaft 24 at the time of steering holding and turning-back steering becomes smaller than when output torque reduction control is not performed at the time of turning steering. In other words, when the output torque reduction control is performed by the vehicle behavior control device, the weight of the steering wheel at the time of steering holding and switchback steering becomes lighter than when the output torque reduction control is not performed. Arise.

Further, as described above, when the output torque reduction control is performed by the vehicle behavior control device, the weight of the steering wheel at the time of turning steering becomes heavier than when the output torque reduction control is not performed. In addition, since the weight of the steering wheel is reduced during the steering holding and the switching back steering, the characteristics of the steering weight change in the process from the switching steering to the switching back steering, and a sense of incongruity is generated.
Therefore, as described below, the vehicle behavior control apparatus according to the present embodiment operates the steering wheel 6 by correcting the assist torque applied to the column shaft 24 when the output torque reduction control is performed. To prevent a sense of incongruity from occurring.

Next, an assist torque determination process performed by the vehicle behavior control apparatus will be described with reference to FIGS.
FIG. 9 is a flowchart of an assist torque determination process in which the vehicle behavior control apparatus according to the embodiment of the present invention determines the target assist torque. FIG. 10 is a flowchart of the assist torque determination process according to the embodiment of the present invention. FIG. 11 is a correction coefficient map referred to when the vehicle behavior control apparatus according to the embodiment of the present invention corrects the target assist torque.

The assist torque determination process of FIG. 9 is started and executed repeatedly when the ignition of the vehicle 1 is turned on and the vehicle behavior control device is turned on.
When the assist torque determination process is started, as shown in FIG. 9, in step S <b> 31, the assist control unit 36 reads the steering torque τ detected by the torque sensor 32 and the vehicle speed V detected by the vehicle speed sensor 12.

  Next, in step S32, the assist control unit 36 refers to the amplification factor map shown in FIG. 10A, and acquires the amplification factor gradient K corresponding to the vehicle speed V read in step S31.

  The gain map shown in FIG. 10A is an input / output characteristic of the steering torque that is input and the gain that is output (obtained by dividing the assist torque (output torque of the motor 28) by the steering torque). And is created in advance for each vehicle speed. Specifically, the steering torque is defined on the horizontal axis, and the amplification factor is defined on the vertical axis. In FIG. 10, input / output characteristics are created when the vehicle speed is 10 km / h, 30 km / h, 80 km / h, and 150 km / h. The larger the steering torque and the lower the vehicle speed, the larger the amplification factor is set (that is, the assist torque becomes larger).

  When the amplification factor is plotted against the steering torque, a straight line passing through the origin (0, 0) is obtained. That is, the steering torque and the amplification factor have a linear relationship. A value corresponding to the slope of this straight line (a value obtained by dividing the amplification factor by the steering torque) is defined as the amplification factor gradient K. The assist control unit 36 reads each amplification factor gradient K set in the amplification factor map, and calculates the amplification factor gradient K corresponding to the vehicle speed V read in step S31 by interpolation or the like.

Next, in step S <b> 33, the assist control unit 36 determines based on the change in the steering angle detected by the steering angle sensor 30 whether or not the steering is in the incision steering in which the steering angle increases.
As a result, when the turning steering is being performed, the process proceeds to step S34, and the assist control unit 36 determines whether the torque reduction flag is set to True by the torque reduction amount determination unit 18.

As a result, when the torque reduction flag is not set to True (when the torque reduction flag is set to False), that is, while the turning steering is being performed, the steering speed is equal to or less than the threshold value T _S1 . When the output torque reduction control is not performed, the process proceeds to step S35, and the assist control unit 36 calculates the target assist torque using the gain gradient K acquired in step S32 as it is. Specifically, since amplification factor = amplification factor gradient K × steering torque τ and target assist torque = amplification factor × steering torque τ, calculation is performed using target assist torque = K × τ ² .

  On the other hand, when the torque reduction flag is set to True in step S34, that is, when the engine control unit 22 is performing the reduction control of the output torque of the engine 4 during the turning steering, the process proceeds to step S36 and assist control is performed. The unit 36 refers to the correction coefficient map for turning steering shown in FIG. 11A, and acquires the correction coefficient A of the target assist torque at the time of turning steering corresponding to the vehicle speed V read in step S31.

  The correction coefficient map shown in FIG. 11A shows the relationship between the vehicle speed V and the correction coefficient A of the target assist torque during the turning steering. As shown in FIG. 11A, the correction coefficient A is a positive value, and is set so that the correction coefficient A increases as the vehicle speed increases.

Next, in step S37, the assist control unit 36 corrects the amplification factor gradient K acquired in step S32 with the correction coefficient A at the time of turning steering acquired in step S36, and uses the corrected amplification factor gradient to achieve the target. Assist torque is calculated. Specifically, the assist control unit 36 sets a value obtained by adding the correction coefficient A at the time of turning steering to the gain gradient K acquired in step S32 as a corrected gain gradient. In this case, since amplification factor = amplification factor gradient (K + A) × steering torque τ and target assist torque = amplification factor × steering torque τ, target assist torque = (K + A) × τ ² .

  FIG. 10B is an amplification factor map when the amplification factor gradient K is corrected by the correction factor A at the time of turning steering. In FIG. 10B, the amplification factor gradient is larger than in the case of FIG. 10A (when correction is not performed with the correction coefficient A). Further, as described above, the correction coefficient A increases as the vehicle speed increases, so that the change width of the amplification factor according to the change in the vehicle speed is narrower than that in the case of FIG. That is, when the gain gradient K is corrected by the correction coefficient A at the time of turning steering, the target assist torque decrease amount corresponding to the increase in the vehicle speed is the target assist torque decrease corresponding to the vehicle speed increase without the correction. Smaller than the amount.

If it is determined in step S33 that the steering angle is not increasing and the steering is not being turned (steering is being held or turned back), the process proceeds to step S38, and the assist control unit 36 performs the torque reduction flag during the immediately preceding turning steering. Whether or not is set to True is determined.
For example, the assist control unit 36 makes a determination with reference to a torque reduction control execution flag indicating whether or not the torque reduction flag is set to True during the immediately preceding turning steering. This torque reduction control execution flag is set to True when the torque reduction flag is set to True during the turning steering, and is reset to False when the turning steering is started again after the switching back steering is performed. The

As a result, if the torque reduction flag is not set to True during the immediately preceding cutting steering, that is, if the output torque reduction control of the engine 4 is not being performed during the immediately preceding cutting steering, the process proceeds to step S35 and assist control is performed. The unit 36 calculates the target assist torque using the amplification factor gradient K acquired in step S32 as it is. That is, target assist torque = K × τ ² .

  On the other hand, if the torque reduction flag is set to True during the last turning steering, the process proceeds to step S39, and the assist control unit 36 refers to the correction coefficient map for switching back steering shown in FIG. Then, the correction coefficient B at the time of switchback steering corresponding to the vehicle speed V read in step S31 is acquired.

  The correction coefficient map shown in FIG. 11B shows the relationship between the vehicle speed V and the correction coefficient B of the target assist torque at the time of switchback steering. As shown in FIG. 11B, the correction coefficient B is a negative value, and is set so that the absolute value of the correction coefficient B decreases as the vehicle speed increases.

Next, in step S40, the assist control unit 36 corrects the amplification factor gradient K acquired in step S32 with the correction coefficient B at the time of switchback steering acquired in step S39, and uses the corrected amplification factor gradient. A target assist torque is calculated. Specifically, the assist control unit 36 sets a value obtained by adding the correction coefficient B at the time of steering back to the gain gradient K acquired in step S32 as a corrected gain gradient. In this case, since amplification factor = amplification factor gradient (K + B) × steering torque τ and target assist torque = amplification factor × steering torque τ, target assist torque = (K + B) × τ ² .

  FIG. 10C is an amplification factor map when the amplification factor gradient K is corrected by the correction factor B at the time of steering back. In FIG. 10C, the amplification factor gradient is smaller than in the case of FIG. 10A (when the correction coefficient B is not used for correction). Further, as described above, the higher the vehicle speed, the smaller the absolute value of the correction coefficient B. Therefore, the change width of the amplification factor according to the change in the vehicle speed is narrower than that in the case of FIG. That is, when the gain gradient K is corrected by the correction coefficient B at the time of turning steering, the amount of decrease in the target assist torque according to the increase in the vehicle speed is the decrease in the target assist torque according to the increase in the vehicle speed without correction. Smaller than the amount.

  After step S35, S37, or S40, the assist control unit 36 ends the process.

Next, further modifications of the embodiment of the present invention will be described.
In the above-described embodiment, it has been described that the torque reduction amount determination unit 18 obtains the target additional deceleration based on the steering speed and determines the torque reduction amount based on the target additional deceleration, but other than the operation of the accelerator pedal. The torque reduction amount may be determined based on the driving state of the vehicle 1 (steering angle, lateral acceleration, yaw rate, slip ratio, etc.).
For example, the torque reduction amount determination unit 18 acquires the target additional deceleration based on the lateral acceleration input from the acceleration sensor and the lateral jerk obtained by time differentiation of the lateral acceleration so as to determine the torque reduction amount. It may be.

  Further, in the above-described embodiment, it has been described that the vehicle 1 equipped with the vehicle behavior control device is equipped with the engine 4 that drives the drive wheels. However, the motor that drives the drive wheels with electric power supplied from a battery or a capacitor. The vehicle behavior control apparatus according to the present invention can also be applied to a vehicle equipped with a vehicle. In this case, the PCM 14 performs control to reduce the motor torque in accordance with the steering speed of the vehicle 1.

  Next, effects of the vehicle behavior control apparatus according to the above-described embodiment of the present invention and the modification of the embodiment of the present invention will be described.

  First, the assist control unit 36 sets a target assist torque according to the steering of the steering wheel 6 by the driver, and the target assist torque when the PCM 14 reduces the output torque of the engine 4 according to the steering speed. Therefore, the PCM 14 reduces the output torque of the engine 4 in accordance with the steering speed at the time of the turning steering, thereby reducing the column shaft from the road surface via the front wheel 2 at the time of the turning steering more than when the output torque reduction control is not performed. Even when the reaction force torque transmitted to 24 increases, by increasing the target assist torque, it is possible to suppress the weight of the steering from becoming too heavy, thereby improving the stability of the vehicle posture and the ride comfort. While controlling the output torque of the engine 4 at the same time, Between the time of actuation can be suppressed uncomfortable feeling occurs when operating the steering wheel 6.

  In particular, the assist control unit 36 sets the target assist torque so that the target assist torque decreases as the vehicle speed increases, while the PCM 14 decreases the output torque of the engine 4 according to the steering speed as the vehicle speed increases. In this case, since the amount of increase when the target assist torque is increased is increased, the PCM 14 reduces the output torque of the engine 4 in a situation where the target assist torque is set relatively small due to the relatively high vehicle speed. As a result, even when the reaction torque transmitted to the column shaft 24 at the time of turning steering is increased, the tendency that the steering weight becomes heavier is promoted by increasing the amount of increase in the target assist torque in accordance with the increase in the vehicle speed. This can be suppressed, so that the output torque control of the engine 4 is activated and deactivated. Between, it can be reliably prevented that the uncomfortable feeling is caused when the steering wheel 6.

Further, the assist control unit 36 sets a target assist torque according to the steering of the steering wheel 6 by the driver, and after the PCM 14 reduces the output torque of the engine 4 according to the steering speed equal to or higher than T _S1 , the steering is performed. When the speed is less than T _S1 , the target assist torque is decreased. Therefore, the PCM 14 reduces the output torque of the engine 4 according to the steering speed at the time of turning steering, so that the output torque reduction control is not performed. Even if the reaction force torque transmitted from the road surface to the column shaft 24 via the front wheel 2 is smaller during steering holding and switchback steering, the steering weight is reduced by reducing the target assist torque. It is possible to prevent the engine 4 from becoming excessively large, and thereby improve the stability and ride comfort of the vehicle posture. While controlling the torque, between the time of operation during the non-operation of the output torque control of the engine 4 it can be suppressed uncomfortable feeling occurs when operating the steering wheel 6.

In particular, the assist control unit 36 sets the target assist torque so that the target assist torque decreases as the vehicle speed increases. On the other hand, as the vehicle speed increases, the steering speed becomes less than T _S1 after the output torque of the engine 4 is reduced. In this case, since the amount of decrease when the target assist torque is decreased is reduced, the PCM 14 has reduced the output torque of the engine 4 in a situation where the target assist torque is set relatively large due to the relatively low vehicle speed. As a result, even when the reaction torque transmitted to the column shaft 24 during steering holding or switchback steering is reduced, the weight of the steering is reduced by increasing the amount of decrease in the target assist torque in accordance with the reduction in the vehicle speed. It is possible to suppress the tendency from being promoted, and thereby, when the output torque control of the engine 4 is activated and not Between the time of movement, it can be reliably prevented that the uncomfortable feeling is caused when the steering wheel 6.

1 Vehicle 2 Front Wheel 4 Engine 6 Steering Wheel 8 EPAS
10 Accelerator opening sensor 12 Vehicle speed sensor 14 PCM
DESCRIPTION OF SYMBOLS 16 Basic target torque determination part 18 Torque reduction amount determination part 20 Final target torque determination part 22 Engine control part 24 Column shaft 28 Motor 30 Steering angle sensor 36 Assist control part

Claims (2)

In a vehicle behavior control device for controlling the behavior of a vehicle in which front wheels are steered,
Steering speed acquisition means for acquiring the steering speed of the vehicle;
A driving force reducing means for reducing the driving force of the vehicle when the steering speed is equal to or greater than a predetermined threshold value greater than 0 during the turning steering;
A motor that applies assist torque to the column shaft that connects the front wheel and the steering wheel;
Target assist torque setting means for setting a target assist torque according to the steering of the steering wheel by the driver;
When the driving force reducing means reduces the driving force of the vehicle, target assist torque increasing means for increasing the target assist torque than when the driving force reducing means does not reduce the driving force of the vehicle; ,
A vehicle behavior control device comprising: an assist control unit that controls the motor so as to output an assist torque set by the target assist torque setting unit and the target assist torque increasing unit. The target assist torque setting means sets the target assist torque so that the target assist torque decreases as the vehicle speed increases,
The vehicle behavior control apparatus according to claim 1, wherein the target assist torque increasing means increases the increase amount of the target assist torque as the vehicle speed increases.

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