JP2011063132A - Vehicle control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably maintain behavior of a vehicle by taking various types of measures for recovering the wheel grip or preventing the wheel grip from deteriorating. <P>SOLUTION: The vehicle 10 includes a driving force distribution means 300 for adjusting front and rear driving force distribution; and a steering angle correction means 400 for correcting the steering angle of a steering wheel, and further includes a steering torque application means 500 for applying a steering torque to a steering mechanism. The vehicle also includes a detection means 100 for detecting at least one of an over-steering state and an under-steering state; a first control means 100 for controlling, upon detection of at least one of the states, a behavior stabilization means so that the detected at least one state is suppressed; a specification means 100 for specifying an accelerator opening degree of the vehicle; and a second control means 100 for controlling, when the accelerator opening degree is a predetermined value or more in a period of time during which the behavior stabilization means is controlled, the steering torque application means through the steering torque application so as to call a driver's attention. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a vehicle configured to be able to stabilize behavior by suppressing an oversteer (hereinafter abbreviated as “OS” where appropriate) or understeer (hereinafter abbreviated as “US” where appropriate) state. The present invention relates to a technical field of a control device for a vehicle to be controlled.

  As this type of device, a device that suppresses the OS state and the US state by changing the driving force distribution, correcting the rudder angle, and selectively braking the selected wheel has been proposed (see, for example, Patent Document 1). . According to the vehicle disclosed in Patent Document 1, in order to suppress the OS state and the US state, the driver's driving is performed by executing these in order of change of the driving force distribution, correction of the steering angle, and selective braking. It is said that these states can be suppressed while keeping the intention.

  In addition, a technique for informing the driver that the vehicle is at the turning limit by applying a steering torque and prompting the driver to perform a spontaneous deceleration operation has been proposed (for example, see Patent Document 2).

  In the technical field of running a vehicle while maintaining a lane, a technique for applying a steering torque according to the accelerator opening is also proposed (see, for example, Patent Document 3).

  In the technical field of suppressing the slip of the drive wheel, a technique for warning the driver when the accelerator opening at the time of clutch meeting is a predetermined value or more has been proposed (for example, see Patent Document 4).

JP 2007-131297 A JP 2000-264237 A JP-A-8-263790 JP 2001-260686 A

  In the vehicle disclosed in Patent Document 1, the order of changing the driving force distribution, correcting the steering angle, and selectively braking the selected wheel is defined in consideration of the point that it is difficult for the driver to feel uncomfortable. Here, the change of the driving force distribution and the correction of the rudder angle are controls that make little sense unless the wheels have a practically significant gripping force, while the selective braking of the selected wheels is This is a control that can control the behavior of the vehicle even in a situation where the grip force is extremely lowered when the wheel exceeds the grip limit. Therefore, when keeping in mind that the driver does not feel uncomfortable, at the time when selective braking of the selected wheel is started, the wheel is in an area that exceeds or is very close to the grip limit. It is reasonable to think that

  However, the change in driving force distribution and the correction of the rudder angle are controls that make it difficult for the driver to perceive the intervention compared to the selective braking of the selected wheel. During the maintenance period, the driver rarely fears that the wheel grip limit is approaching. Therefore, in the vehicle according to Patent Document 1, it is almost impossible to urge the driver to restrain himself / herself from driving operation that hinders stabilization of the vehicle behavior, and the frequency that the wheels exceed the grip limit inevitably increases. easy. Even in such a situation, although it is possible to stabilize the behavior by selective braking of the selected wheel, it is necessary to reestablish the behavior of the vehicle in which the wheel is moving in the region beyond the grip limit. Time is never short, and in such situations, the vehicle is forced to behave unstable over a reasonable amount of time. That is, the vehicle according to Patent Document 1 has a technical problem that it is difficult to avoid instability of vehicle behavior.

  This invention is made | formed in view of the problem which concerns, and makes it a subject to provide the control apparatus of the vehicle which can continue maintaining the behavior of a vehicle stably.

  In order to solve the above-described problem, a vehicle control apparatus according to the present invention includes a driving force distribution unit capable of adjusting at least one of the front and rear and left and right driving force distributions and a steering angle capable of correcting the steering angle of the steered wheels. An apparatus for controlling a vehicle comprising behavior stabilization means including at least one of correction means and steering torque application means capable of applying steering torque to a steering mechanism, wherein the apparatus is at least one of an oversteer state and an understeer state Detection means for detecting the state of the first control means, and when the at least one state is detected, the first control means for controlling the behavior stabilization means so that the detected at least one state is suppressed, and When the specified accelerator opening is greater than or equal to a predetermined value in a period in which the specifying means for specifying the accelerator opening of the vehicle and the behavior stabilizing means are controlled Characterized by comprising a second control means for controlling the steering torque applying means so that the driver attention is invoked through the application of the steering torque.

  The vehicle according to the present invention includes behavior stabilizing means and steering torque applying means. The behavior stabilization means is one or a plurality of means for stabilizing the vehicle behavior at the time of turning, and particularly includes at least one of a driving force distribution means and a steering angle correction means in the present invention.

  The driving force distribution means adjusts at least one of a distribution ratio of the driving force supplied from a power source such as an internal combustion engine to the front and rear wheels and a distribution ratio to the left and right wheels (that is, binary, Means with a possible physical, mechanical, electrical or magnetic configuration (meaning to change stepwise or continuously). As a general steering characteristic of a vehicle, the US tendency becomes stronger as the driving force is distributed to the front wheel side, and the OS tendency becomes stronger as the driving force is distributed to the rear wheel side. Further, the OS tendency increases as the driving force is distributed to the wheels outside the turning track, and the US tendency increases as the driving force is distributed to the wheels inside the turning track. Therefore, according to the driving force distribution, it is possible to stabilize the vehicle behavior. In addition, comparing the case where the driving force is distributed back and forth with the case where the driving force is distributed left and right, the former (front / rear distribution) has a higher effect of guiding the behavior of the vehicle to the stable side. Therefore, the vehicle according to the present invention is a vehicle capable of four-wheel drive traveling at all times or selectively as a preferred embodiment.

  The steering angle correction means is a means having a physical, mechanical, electrical, or magnetic configuration capable of correcting the steering angle of the steered wheels (the so-called actual steering angle). When the steering angle of the steered wheels is corrected, the steering angle (the operation angle of the steering input means such as the steering wheel (that is, the rotation angle) is not necessarily different). However, the steering angle of the steered wheels is corrected in a state in which the steering angle is maintained as a preferred form. In this case, the rudder angle correcting means may be a device that can rotate the steering output shaft relative to the steering input shaft, such as VGRS (Variable Gear Ratio Steering), or SBW ( A device physically separated from the steering input means, such as Steer By Wire (electronically controlled steering angle variable device), may be used. Generally, at one steering angle, the US tendency increases if the steered wheel steer angle is corrected to the switchback side, and the OS tendency increases if the steered wheel is corrected to the additional turn side. Therefore, it is possible to stabilize the vehicle behavior by correcting the steering angle of the steered wheels.

  On the other hand, the steering torque applying means is a means having a configuration capable of applying a steering torque to the steering mechanism by, for example, physical, mechanical, electrical, or magnetic action. The “steering torque” according to the present invention is a torque different from a driver input torque that is appropriately applied by a driver via a steering input means that can take various modes such as a steering wheel. As a preferred embodiment, the steering torque applying means can apply the assist torque for assisting the driver input torque as the steering input applied by the driver via the steering input means as the steering torque according to the present invention. It may be a kind of power steering device such as an EPS (Electronic Control Power Steering) configured.

  Incidentally, the steering torque applying means includes means for enabling a kind of automatic steering called so-called active steering or the like by applying steering torque regardless of the driver input torque at least in concept. . In other words, the steering torque applying means can change the steering angle of the steered wheels regardless of the driver's steering intention, and the steering input means can increase or decrease regardless of the driver's intention when correcting the steering angle. If it is allowed to be returned, it can function as a form of the rudder angle correction means in some cases.

  On the other hand, the “steering mechanism” according to the present invention, which is an object to which steering torque is applied, is connected to the above various steering input means for giving a steering input by a driver, regardless of whether it is direct or indirect ( In other words, it is a mechanism that allows the driver to perceive that the steering torque is applied, for example, various steering shafts (for example, a steering shaft, an upper steering shaft, a lower steering shaft, etc.) It may be a pinion gear or a rack bar in a rack and pinion mechanism or the like.

  In view of the concept of such a steering mechanism, the steering mechanism according to the present invention does not necessarily include a mechanism that applies a physical steering force that prompts the steered wheels to steer the steered wheels. That is, an input system (which may include the above-described various steering input means) in which a driver input torque as a steering input given by the driver based on the steering intention, such as SBW, exerts a physical action, and steering of the driver When the mechanism is separated from an output system (for example, various actuators) that actually applies a steering force to the steered wheels according to a physical quantity (for example, the driver input torque or steering angle) corresponding to the input, The steering mechanism according to the present invention may be a part of the input system. In this case, the “part of the input system” may be, for example, a device that applies an appropriate steering reaction force to the driver.

  The vehicle control device according to the present invention is a device for controlling the vehicle according to the present invention, and includes, for example, one or a plurality of CPUs (Central Processing Units), MPUs (Micro Processing Units), various processors, or various types. Various processing such as a single or multiple ECUs (Electronic Controlled Units), which may appropriately include various storage means such as a controller or ROM (Read Only Memory), RAM (Random Access Memory), buffer memory or flash memory Various computer systems such as a unit, various controllers or a microcomputer device may be used.

  According to the vehicle control apparatus of the present invention, during the operation, various slip states (for example, grip state and one-to-one, one-to-many, many-to-one or Oversteer state (based on various state quantities that can define the steering characteristics of the vehicle, such as the yaw state defined by the yaw rate deviation (deviation between the target yaw rate and the actual yaw rate), etc.) At least one of an OS state and an understeer state (US state) is detected.

  When at least one state is detected by the detection means, the above-described behavior stabilization means is controlled by the first control means so that the detected at least one state is suppressed. As a result, the vehicle can ideally maintain a neutral steer state, or can maintain a weak understeer state or a weak oversteer state, and the turning behavior of the vehicle can be stably maintained.

  On the other hand, the state in which the turning behavior is stably maintained by the action of the first control means is, in other words, the state in which the effect of the behavior stabilizing means is required to maintain the turning behavior stably. This is a state where the wheel is forced to move in an area close to the grip limit as compared with a state where the effect of the adjusting means is not required. For example, if the driving operation of the driver is allowed without limitation during the period in which the vehicle is in such a state, a situation in which the wheel reaches the grip limit or exceeds the grip limit is likely to occur. Regardless of changing the driving force distribution in the front and rear or left and right, or correcting the rudder angle, it is assumed that the wheel moves within the range not exceeding the grip limit, and in the state where the wheel loses the grip, These make little sense for stabilizing the turning behavior of the vehicle. Therefore, as the wheel approaches the grip limit, the vehicle tends to enter the US state by following a trajectory that swells more outward than the turning trajectory intended by the driver.

  Here, one of the driving conditions that can greatly affect the turning behavior of the vehicle is the accelerator opening. The accelerator opening can be paraphrased as a driver acceleration request or a driving force request in practical terms. That is, the magnitude of the accelerator opening can be directly linked to the magnitude of the driving force supplied to the driving wheels and the level of the vehicle speed. These are physical quantities that greatly affect the grip state of the wheel, and in the period of stabilizing the turning behavior of the vehicle using the behavior stabilizing means, for example, when no restrictions are imposed on the accelerator opening, The possibility that the grip state of the wheel is extremely deteriorated is increased.

  Of course, even in such a situation, as described above, when a braking device capable of selectively braking the selected wheel is provided, for example, the braking force acting on the wheel on the inside of the turning track is turned. By taking measures such as making it larger than the braking force acting on the wheels outside the track, the vehicle can be guided to the OS tendency and the behavior can be stabilized. However, the stabilization of vehicle behavior by braking force includes an emergency avoidance implication, so the deviation from the driver's intention tends to be large, and the state in which the vehicle performs turning behavior when the wheel grip state deteriorates is It is hard to say that it is at least preferable.

  Therefore, the vehicle control apparatus according to the present invention provides that the accelerator opening specified by the specifying means is fixed or variable at a predetermined value or more during the turning control stabilization control by the first control means. In some cases, the steering torque applying means is controlled by the action of the second control means, and the driver is alerted that the wheel is approaching the grip limit through the application of the steering torque.

  Here, the steering torque applied under the control of the second control means is a steering torque that can alert the driver, and the practical aspect is not limited as long as the driver can be alerted. For example, the steering torque may be the assist torque that is applied to assist the driver input torque (however, the magnitude is different from the value under the normal mode for the purpose of assisting the driver input torque). ), This type of assist torque may be corrected to a decreasing side or canceled. That is, in these cases, since the assist torque finally increases or decreases, the driver feels that the steering burden in the increasing direction becomes heavy, and that attention is drawn. . Further, this steering torque may be a torque that can actively operate the steering input means to the switchback side (that is, a torque that acts in a direction opposite to the driver's steering direction (neutral direction)). In this case, since the steering torque acts in a direction against the driver's steering intention, it may be possible to attract the driver's attention more remarkably. Here, the case where the assist torque for assisting the driver input torque is applied is shown, but the steering torque applied under the second control is based on whether or not this kind of assist torque is applied. Needless to say, it can call the driver's attention.

  Thus, under the control of the second control means, this kind of alert steering torque is applied, so that the driver feels uncomfortable in the operation of the steering input means in the process of operating the accelerator pedal. Thus, it is possible to clearly perceive that the grip limit is approaching the wheel. Accordingly, it is possible to take various measures for restoring the grip of the wheel or preventing the grip of the wheel from being lowered, and the behavior of the vehicle is stably maintained.

  Supplementally, according to the vehicle control apparatus of the present invention, (1) the OS state or the US state is suppressed by the first control means via the behavior stabilizing means, and (2) the second control means, During the period when the behavior stabilization means is functioning effectively, i.e. before the wheel still reaches the grip limit, the driver is warned that he should avoid driving in a direction that causes the wheel to lose grip. Can be given. Therefore, it is possible to remarkably reduce the chance that the wheel moves in the region exceeding the grip limit, and it is possible to maintain a good steer characteristic close to neutral steer. That is, the behavior of the vehicle can be maintained stably.

  In one aspect of the vehicle control apparatus according to the present invention, the second control means applies the steering torque in a neutral direction.

  According to this aspect, the steering torque is applied in the neutral direction (substantially equivalent to the switchback direction unless the steering angle passes through the neutral point) by the second control means. For this reason, it is possible to clearly notify the driver that the vehicle is turning under behavior stabilization control by the behavior stabilization means, and it is preferable that the driving operation may exceed the grip limit of the wheel. It is possible to reduce it.

  In another aspect of the vehicle control apparatus according to the present invention, when the accelerator opening is decreased, the second control means applies the steering torque in an increasing direction so as to reduce a driver's steering burden. Let

  In a state in which the second control means is calling attention to the driver through the application of steering torque, when the accelerator opening is decreased and, as a preferred form, at least less than the predetermined value, the grip state of the wheel is , Grip degree tends to recover away from the grip limit. If the wheel grip is sufficiently secured, the steering torque applied through the steering torque applying means is used for the purpose of assisting the driver's steering operation rather than for the purpose of alerting the driver. Is useful in practice. This is even more reasonable if such a decrease in accelerator opening was obtained as a result of alerting by steering torque.

  According to this aspect, for example, it can be determined that the grip state of the wheel has recovered to an extent that there is no problem in practice, and the grip state of the wheel is experimentally, empirically, theoretically or based on simulation or the like in advance. It can be determined that the vehicle behavior has been restored to a level that does not cause instability of the vehicle behavior or does not cause the vehicle behavior that is not intended by the driver, or the degree of grip of the wheels can define this type of state. Steering torque reduces the driver's steering burden, such as when a decrease in accelerator opening that can be determined or estimated to have reached or exceeded a predetermined fixed or variable reference value is detected. It is applied in a direction that functions as assist torque. For this reason, it is possible to control the behavior of the vehicle in accordance with the driver's steering intention. More specifically, in such a situation, since the vehicle has a US tendency, the driver's additional operation is facilitated, and the suppression of the US state can be suitably achieved.

  In addition, in this aspect, in addition to the above, when a decrease in the accelerator opening is detected, it is determined whether the separately estimated wheel grip level has reached or exceeded the reference value. Along with this, provision of steering torque as assist torque may be permitted or started.

  In another aspect of the vehicle control apparatus according to the present invention, the second control means performs steering by the driver when a steering input is generated by the driver after the steering torque is applied to alert the driver. The steering torque is corrected according to the input direction.

  For example, when the attention is alerted via the steering torque, the steering input means is operated further in the direction of increasing, and when the attention is alerted via the steering torque, the steering input means switches back. The characteristics of the steering torque to be applied differ from those when operated in the direction.

  According to this aspect, when a driver's steering input is generated after alerting by the second control means, the steering torque is corrected in accordance with the direction of the steering input. For this reason, it becomes possible to suppress the discomfort imparted to the driver as much as possible while stably maintaining the turning behavior of the vehicle.

  In another aspect of the vehicle control apparatus according to the present invention, the behavior stabilizing means applies a braking force to each of the driving force distributing means, the steering angle correcting means, and the wheels of the vehicle independently of each other. A braking unit that can be applied, and the first control unit controls the behavior stabilizing unit to suppress the detected at least one state by a predetermined state quantity that defines the detected at least one state. In accordance with the control, the driving force distribution means, the turning angle correction means, and the braking means are sequentially controlled, and the second control means controls the braking means to suppress at least one of the detected states. The steering torque applying means is controlled before the operation is started.

  According to this aspect, the behavior stabilizing means includes the braking means, and the braking means applies the independent braking force to each of the wheels (the above-described selective braking of the selected wheel can be conceptually included). Thus, the turning behavior of the vehicle is stably maintained.

  Here, in particular, in this aspect, in order to maintain the turning behavior of the vehicle stably, the priority order is determined for each behavior stabilization means, and these are in the order of the driving force distribution means, the steering angle correction means, and the braking means. The control is started. When the behavior is stabilized by the driving force distribution means, the front and rear driving force distribution is only changed, and the driving force of the entire vehicle is not changed. Therefore, the driver is almost aware of the intervention. Absent. On the other hand, the stabilization of behavior by the braking means includes the meaning of emergency avoidance more strongly, and the driver must clearly perceive the intervention and feel uncomfortable. That is, this order is an order determined so that the driver does not feel uncomfortable. Therefore, according to this aspect, when the turning behavior of the vehicle is stabilized by the first control means, it is possible to eliminate the feeling of discomfort to the driver as much as possible, which is extremely useful in practice.

  On the other hand, according to this aspect, the application of the steering torque by the second control means is executed before the behavior stabilization by the braking means is started. As already mentioned, the provision of steering torque by the second control means has the meaning of giving information to the driver that the wheel is approaching the grip limit. The possibility of taking measures such as lowering or operating the steering input means to the switchback side increases dramatically.

  As a result, the opportunity to activate the behavior stabilization control by the braking means, which is necessary when the wheel moves in the region exceeding the grip limit or very close to the grip limit, is significantly reduced in this embodiment. That is, according to this aspect, the turning behavior of the vehicle can be favorably maintained by the driving force distribution and the steering angle correction without making the driver feel as uncomfortable as possible.

  In another aspect of the vehicle control apparatus according to the present invention, the steering mechanism is a mechanism capable of transmitting a steering force that prompts the steered wheels to steer the steered wheels.

  As described above, when the steering mechanism includes a mechanism capable of transmitting a steering force for urging the steered wheels to steer the steered wheels, in other words, the input system and the output system described above are connected directly or indirectly. If the steering torque is applied to any of the paths from the input system to the output system, the driver can perceive the applied steering torque via the steering input means. Become.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

1 is a schematic configuration diagram conceptually illustrating a configuration of a vehicle according to an embodiment of the present invention. 2 is a flowchart of behavior stabilization control performed in the vehicle of FIG. 1. It is a figure showing the characteristic of basic assist torque ATbase with respect to steering torque MT. It is a figure showing the characteristic of standard information torque ATinfb with respect to state quantity S. It is a figure showing the characteristic of gain G1 to accelerator opening A. It is a figure showing the characteristic of gain G2 to accelerator opening change rate dA. It is a figure showing the characteristic of gain G1 with respect to cutting steering amount STR1. It is a figure showing the characteristic of the gain G1 with respect to the switchback steering amount STR2.

Hereinafter, various embodiments according to a vehicle control apparatus of the present invention will be described with reference to the drawings as appropriate.
<Embodiment of the Invention>
<Configuration of Embodiment>
First, with reference to FIG. 1, the structure of the vehicle 10 which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram conceptually showing the basic configuration of the vehicle 10.

  In FIG. 1, the vehicle 10 includes a pair of left and right left front wheels FL and a right front wheel FR as steered wheels, and these front wheels can travel in a desired direction by turning. The vehicle 10 includes an ECU 100, an engine 200, a driving force distribution device 300, a VGRS actuator 400, a VGRS driving device 410, an EPS actuator 500, an EPS driving device 510, and a brake actuator 600.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) (not shown) and is configured to be able to control the entire operation of the vehicle 10. This is an example of a “vehicle control device”. The ECU 100 is configured to execute behavior stabilization control, which will be described later, according to a control program stored in the ROM.

  The ECU 100 is an integrated electronic control unit configured to function as an example of each of the “detection unit”, “first control unit”, “specification unit”, and “second control unit” according to the present invention. The operations related to these means are all configured to be executed by the ECU 100. However, the physical, mechanical, and electrical configurations of each of the units according to the present invention are not limited to this. For example, each of these units includes a plurality of ECUs, various processing units, various controllers, a microcomputer device, and the like. It may be configured as various computer systems.

  The engine 200 is an in-line four-cylinder gasoline engine that functions as a driving force source for the vehicle 10. The vehicle according to the present invention preferably includes an internal combustion engine as at least a part of its driving force source. However, the “internal combustion engine” mentioned here is a concept that encompasses an engine that can convert fuel combustion into mechanical power and take it out, and its practical aspect is not limited to the engine 200 that is an in-line four-cylinder gasoline engine. It is the purpose. Since the detailed configuration of the engine 200 has little correlation with the gist of the present invention, it is omitted here, but the crankshaft that is the driving force output shaft of the engine 200 is connected to the driving force distribution device 300.

  The driving force distribution device 300 is configured to be able to distribute the driving force of the engine 200 transmitted through the crankshaft, that is, the engine torque Te, to the front wheels and the rear wheels at a predetermined ratio. It is an example of “driving force distribution means”. A front wheel drive shaft 12 connected to the front wheel side differential 13 and a rear wheel drive shaft 14 connected to the rear wheel side differential 15 are connected to the driving force distribution device 300, and the rear wheel drive shaft 14 includes Further, an electromagnetic clutch (not shown) is interposed. This electromagnetic clutch is configured such that its engagement state changes continuously according to the drive state of a solenoid (not shown), and in the state where the electromagnetic clutch is completely engaged, the engine torque Te is determined by the front wheel side drive shaft. 12 and the rear wheel drive shaft 14 are distributed at a ratio of 50:50. Further, when the clutch plate of the electromagnetic clutch starts to slip as the engagement current of the electromagnetic clutch decreases, the engine torque distributed to the rear wheel drive shaft 14 decreases and the electromagnetic clutch is completely released. The engine torque Te is transmitted to the 100% front wheel side drive shaft 12. The solenoid that drives the electromagnetic clutch is electrically connected to the ECU 100, and the driving state of the electromagnetic clutch is controlled by the ECU 100 via the solenoid.

  The configuration of the driving force distribution device 300 is merely an example of a practical aspect that can be adopted by the driving force distribution means according to the present invention. As long as it can be distributed in a variable ratio, it may have any configuration regardless of whether it is publicly known or not.

  The VGRS actuator 400 is a transmission ratio variable device as an example of the “steering angle correction means” according to the present invention, which includes a housing, a VGRS motor, a speed reduction mechanism, a lock mechanism (all not shown), and the like.

  In the VGRS actuator 400, the VGRS motor, the speed reduction mechanism, and the lock mechanism are accommodated in a housing. This housing is fixed to an end portion on the downstream side of the upper steering shaft 17 connected to a steering wheel 16 as a steering input means, and is configured to be rotatable substantially integrally with the upper steering shaft 17.

  The VGRS motor is a DC brushless motor having a rotor as a rotor, a stator as a stator, and a rotation shaft as an output shaft of driving force. The stator is fixed inside the housing, and the rotor is rotatably held inside the housing. The rotating shaft is fixed so as to be coaxially rotatable with the rotor, and the downstream end thereof is connected to the speed reduction mechanism.

  The speed reduction mechanism is a planetary gear mechanism having a plurality of rotational elements capable of differential rotation. One rotation element of the plurality of rotation elements is connected to the rotation shaft of the VGRS motor, and one of the other rotation elements is connected to the housing. The remaining rotating elements are connected to the lower steering shaft 18.

  According to the speed reduction mechanism having such a configuration, the rotation speed of the upper steering shaft 17 (that is, the rotation speed of the housing) corresponding to the operation amount of the steering wheel 16 and the rotation speed of the VGRS motor (that is, the rotation of the rotation shaft). Speed) uniquely determines the rotation speed of the lower steering shaft 18 connected to the remaining one rotation element. At this time, the rotational speed of the lower steering shaft 18 can be increased or decreased by controlling the rotational speed of the VGRS motor to increase or decrease by the differential action between the rotating elements. That is, the upper steering shaft 17 and the lower steering shaft 18 can be rotated relative to each other by the action of the VGRS motor and the speed reduction mechanism. The rotational speed of the VGRS motor is transmitted to the lower steering shaft 18 in a state of being decelerated according to a predetermined reduction ratio determined according to the gear ratio between the respective rotary elements because of the configuration of each rotary element in the speed reduction mechanism.

  Thus, in the vehicle 10, the upper steering shaft 17 and the lower steering shaft 18 can rotate relative to each other, so that the steering angle MA that is the amount of rotation of the upper steering shaft 17 and the amount of rotation of the lower steering shaft 18 are determined. The steering transmission ratio, which is uniquely determined (which also relates to the gear ratio of a rack and pinion mechanism described later) and the steering angle ω of the front wheel, which is a steered wheel, is continuously variable within a predetermined range.

  The lock mechanism is a clutch mechanism including a clutch element on the VGRS motor side and a clutch element on the housing side. In a state in which both clutch elements are engaged with each other, the rotational speeds of the upper steering shaft 17 and the rotation shaft of the VGRS motor coincide with each other, so that the rotational speed of the lower steering shaft 18 necessarily coincides therewith. That is, the upper steering shaft 17 and the lower steering shaft 18 are directly connected. However, the details of the locking mechanism are omitted here because the correlation with the present invention is weak.

  The VGRS drive device 410 is an electric drive circuit including a PWM circuit, a transistor circuit, an inverter, and the like that are configured to be energized to the stator of the VGRS motor. The VGRS driving device 410 is electrically connected to a battery (not shown), and is configured to be able to supply a driving voltage to the VGRS motor by electric power supplied from the battery. Further, the VGRS driving device 410 is electrically connected to the ECU 100, and its operation is controlled by the ECU 100. The VGRS driving device 410, together with the VGRS actuator 400, constitutes an example of the “steering angle correction unit” according to the present invention.

  In the vehicle 10, the rotation of the lower steering shaft 18 is transmitted to a rack and pinion mechanism. The rack and pinion mechanism is a transmission mechanism including a pinion gear 19 connected to a downstream end portion of the lower steering shaft 18 and a rack bar 20 formed with gear teeth that mesh with gear teeth of the pinion gear. When the rotation of 19 is converted into a horizontal movement of the rack bar 20, the steering force is transmitted to each steered wheel via tie rods and knuckles (not shown) connected to both ends of the rack bar 20. It is the composition which becomes. That is, the transmission mechanism of the steering force from the steering wheel 16 to each front wheel is an example of the “steering mechanism” according to the present invention.

  The EPS actuator 500 includes an EPS motor as a DC brushless motor including a rotor (not shown) that is a rotor to which a permanent magnet is attached and a stator that is a stator that surrounds the rotor. It is an example of “torque applying means”. This EPS motor is configured to be able to generate an assist torque TA in the direction of rotation when the rotor is rotated by the action of a rotating magnetic field formed in the EPS motor by energizing the stator via the EPS driving device 510. ing.

  On the other hand, a reduction gear (not shown) is fixed to a motor shaft that is a rotation shaft of the EPS motor, and this reduction gear is also meshed with a reduction gear provided on the lower steering shaft 18. For this reason, in the present embodiment, the assist torque TA generated from the EPS motor functions as a torque that assists the rotation of the lower steering shaft 18. Therefore, when the assist torque TA is applied in the same direction as the driver input torque MT applied to the upper steering shaft 17 via the steering shaft 16, the driver's steering burden is reduced by the assist torque TA. The

  The EPS drive device 510 is an electric drive circuit including a PWM circuit, a transistor circuit, an inverter, and the like that are configured to be energized to the stator of the EPS motor. The EPS driving device 510 is electrically connected to a battery (not shown), and is configured to be able to supply a driving voltage to the EPS motor by electric power supplied from the battery. Further, the EPS driving device 510 is electrically connected to the ECU 100, and its operation is controlled by the ECU 100. The EPS driving device 510, together with the EPS actuator 500, constitutes an example of “steering torque applying means” according to the present invention.

  The aspect of the “steering torque applying means” according to the present invention is not limited to the one illustrated here. For example, the assist torque TA output from the EPS motor is used to reduce the rotational speed by a reduction gear (not shown). Accordingly, it may be transmitted to the pinion gear 19 or may be transmitted to the upper steering shaft 17.

  On the other hand, the vehicle 10 includes various sensors including a steering angle sensor 21 and a steering torque sensor 22.

  The steering angle sensor 21 is an angle sensor configured to be able to detect a steering angle MA that represents the amount of rotation of the upper steering shaft 17. The steering angle sensor 21 is electrically connected to the ECU 100, and the detected steering angle MA is referred to by the ECU 100 at a constant or indefinite period.

  The steering torque sensor 22 is a sensor configured to be able to detect a driver input torque MT given from the driver via the steering wheel 16. More specifically, the upper steering shaft 17 is divided into an upstream portion and a downstream portion, and has a configuration in which they are connected to each other by a torsion bar (not shown). Rings for detecting a rotational phase difference are fixed to both upstream and downstream ends of the torsion bar. The torsion bar is twisted in the rotational direction according to the steering torque (that is, the driver input torque MT) transmitted through the upstream portion of the upper steering shaft 17 when the driver of the vehicle 10 operates the steering wheel 16. The configuration is such that the steering torque can be transmitted to the downstream portion while causing such a twist. Therefore, when the steering torque is transmitted, a rotational phase difference is generated between the above-described rings for detecting the rotational phase difference. The steering torque sensor 22 is configured to detect such a rotational phase difference and convert the rotational phase difference into a steering torque so as to be output as an electrical signal corresponding to the driver input torque MT. The steering torque sensor 22 is electrically connected to the ECU 100, and the detected driver input torque MT is referred to by the ECU 100 at a constant or indefinite period.

  The brake actuator 600 individually supplies hydraulic fluid to the braking devices 610FL, 610FR, 610RL, and 610RR provided individually for the left front wheel FL, the right front wheel FR, the left rear wheel RL, and the right rear wheel RR. The hydraulic pressure adjusting actuator is configured to be possible. The brake actuator 600 is composed of a master cylinder, an electric oil pump, a plurality of hydraulic pressure transmission passages, and electromagnetic valves installed in each of the hydraulic pressure transmission passages. By controlling the open / close state of the electromagnetic valves, The hydraulic pressure of the hydraulic fluid supplied to the wheel cylinder provided in each brake device is configured to be individually controllable for each brake device. The hydraulic pressure of the hydraulic fluid has a one-to-one relationship with the pressing force of the brake pad provided in each braking device, and the hydraulic pressure of the hydraulic fluid corresponds to the magnitude of the braking force in each braking device. Yes. The brake actuator 600 is electrically connected to the ECU 100, and the braking force applied to each wheel from each braking device is controlled by the ECU 100.

  Although illustration is omitted for the purpose of preventing complication of the drawings, the vehicle 10 detects an accelerator opening sensor that detects the accelerator opening A, a plurality of wheel speed sensors that detect the wheel speed for each wheel, and a vehicle speed V. It is assumed that various sensors other than those shown in the drawing are provided, such as a vehicle speed sensor that detects the lateral acceleration Gy of the vehicle 10 and a yaw rate sensor that detects the yaw rate Yr of the vehicle 10. These are also configured to provide sensor output values to various controls performed by the ECU 100 by being electrically connected to the ECU 100.

<Operation of Embodiment>
Next, the details of the behavior stabilization control executed by the ECU 100 will be described as operations of the present embodiment with reference to FIG. FIG. 2 is a flowchart of the behavior stabilization control.

  In FIG. 2, the ECU 100 calculates a vehicle state quantity S (step S101).

  Here, the vehicle state quantity S is a state quantity that defines the turning behavior of the vehicle 10 (meaning the behavior during turning), and in this embodiment, it is assumed to be the yaw rate deviation ΔYr. The yaw rate deviation ΔYr is defined by the following equation (1).

ΔYr = Yrtg−Yr (1)
In the above equation (1), Yr is the actual yaw rate of the vehicle 10 detected by the yaw rate sensor, and Yrtg is the target yaw rate of the vehicle 10. The target yaw rate Yrtg is a yaw rate that should be originally estimated from the current state of the vehicle 10, and if the target yaw rate Yrtg is equal to or approximately equal to the actual yaw rate Yr to be detected, that is, the yaw rate deviation ΔYr≈0. If the relationship is established, it can be estimated that the turning behavior of the vehicle 10 is in the neutral steer state. Further, when the target yaw rate Yrtg is larger than the yaw rate Yr, that is, when the relationship of yaw rate deviation ΔYr> 0 is established, the vehicle 10 is traveling on a trajectory that swells outward from the turning trajectory to be originally traced. It can be estimated that the turning behavior of the vehicle 10 is in the US state. Similarly, when the target yaw rate Yrtg is smaller than the yaw rate Yr, that is, when the relationship that the yaw rate deviation ΔYr <0 is established, the vehicle 10 is traveling on the inner track than the originally intended trajectory, It can be estimated that the turning behavior of the vehicle 10 is in the OS state.

  The target yaw rate Yrtg is calculated by the following equation (2). In equation (2), N is the transmission ratio (gear ratio) of the steering mechanism including the rack and pinion mechanism and the VGRS actuator 400, L is the wheel base of the vehicle 10, and Kh is a predetermined star. It is a stability factor. The ECU 100 reads the sensor output from each sensor and each constant stored in the ROM, calculates the target yaw rate Yrtg according to the equation (2), and calculates the yaw rate deviation ΔYr. The calculated yaw rate deviation ΔYr is stored in the RAM of the ECU 100 so that it can be referred to. The calculation of the vehicle state quantity S is started at step S101 and then repeatedly executed at a predetermined cycle, so that the latest value is always stored in the RAM.

Yrtg = V · MA / (N · L) −Kh · Gy · V (2)
In this embodiment, the yaw rate deviation ΔYr is adopted as the vehicle state quantity S, but the state quantity that defines the turning behavior of the vehicle 10 is not limited to the yaw rate deviation ΔYr. For example, the vehicle state quantity S may be a slip amount of each front and rear wheel, or an average value thereof. Since the slip amount of each wheel can be calculated according to various known methods based on the wheel speed detected by the wheel speed sensor, the details thereof will not be described here, but qualitatively, the slip amount Since the wheel is closer to the grip limit, the slip amount functions sufficiently effectively in practice as an index value for determining how much the grip state of each wheel of the vehicle 10 is. Further, by comparing the slip amounts of the front and rear wheels, it is also possible to determine whether the vehicle 10 is currently in the US state, the neutral steer state, or the OS state, and the behavior is stable. As the vehicle state amount S related to the overall control, the slip amount of the front and rear wheels is also sufficiently effective.

  When the vehicle state quantity S (here, the yaw rate deviation ΔYr) is calculated, the ECU 100 simply calculates the absolute value of the calculated vehicle state quantity S (hereinafter referred to as “vehicle state quantity S” for the purpose of preventing complication of explanation). Is determined to be greater than or equal to the first reference value S1 (step S102). Here, the first reference value S1 is experimentally determined in advance as a limit value that can stably maintain the turning behavior of the vehicle 10 only by changing the driving force distribution.

  When the vehicle state quantity S is less than the first reference value S1 (step S102: NO), the ECU 100 returns the process to step S101 and repeats a series of processes. That is, when the vehicle state quantity S is less than the first reference value S1, the ECU 100 does not operate any of the driving force distribution device 300, the VGRS actuator 400, and the brake actuator 600 that function as behavior stabilization means. In this case, the ECU 100 only assists the driver input torque MT via the EPS actuator 500, and the vehicle 10 performs a normal turning operation.

Here, with reference to FIG. 3, the assist of the driver input torque MT by the EPS actuator 500 will be described. FIG. 3 is a diagram showing characteristics of the basic assist torque ATbase with respect to the driver input torque MT. In FIG. 3, the horizontal axis represents the driver input torque MT, and the vertical axis represents the basic assist torque ATbase. . On the horizontal axis, a region on the right side of the illustrated zero is a positive region corresponding to the right steering direction, and a left region is a negative region corresponding to the left steering direction. Similarly, on the vertical axis, an area above zero is a positive area corresponding to the right steering direction, and a lower area is a negative area corresponding to the left steering direction.

  As shown in the figure, the basic assist torque ATbase is set such that its absolute value increases according to the driver input torque MT, except for the dead zone region where the absolute value of the driver input torque MT is small and the saturation region where the absolute value is large. Has been. The basic assist torque ATbase is a steering torque applied in the same direction as the driver input torque MT. That is, when the basic assist torque ATbase is applied to the lower steering shaft 18, the steering burden on the driver is reduced.

  Returning to FIG. 2, when the vehicle state quantity S is equal to or greater than the first reference value S1 (step S102: YES), the ECU 100 executes a driving force distribution process (step S103). The driving force distribution process means a process for inviting the turning behavior of the vehicle 10 to the neutral steer side by changing the front / rear driving force distribution ratio by the driving force distribution device 300. That is, the ECU 100 increases the driving force distribution on the rear wheel side if the turning behavior of the vehicle 10 is in the US state, and increases the driving force distribution on the front wheel side if it is in the OS state. It is assumed that the driving force distribution ratio as the control amount with respect to the vehicle state quantity S is determined in advance through experimental adaptation and stored as a fixed value in the ROM.

  According to this driving force distribution process, the front / rear distribution ratio of the engine torque Te, which is the driving force, only changes, and the driving force does not fluctuate. Therefore, the driver hardly perceives the intervention of the driving force distribution device 300. In other words, the turning behavior of the vehicle 10 can be converged to the neutrast steer side without making the driver feel uncomfortable.

  When the driving force distribution process is executed, the ECU 100 determines whether or not the vehicle state quantity S is greater than or equal to the second reference value S2 (S2> S1) (step S104). When the vehicle state quantity S is less than the second reference value S2 (step S104: NO), the ECU 100 returns the process to step S101 and repeats a series of processes. That is, in this case, the turning behavior of the vehicle 10 is stabilized only by the driving force distribution process.

  On the other hand, when the vehicle state quantity S is greater than or equal to the second reference value S2 (step S104: YES), the ECU 100 executes a steering angle correction process (step S105). In the steering angle correction process, the lower steering shaft 18 and the upper steering shaft 17 are rotated relative to each other by the drive control of the VGRS actuator 400 to correct the steering angle ω of the front wheel that is a steered wheel, and the turning behavior of the vehicle 10 is neutral. It means processing to invite to the steer side. That is, the ECU 100 corrects the steering angle ω to the increased side if the turning behavior of the vehicle 10 is in the US state, and corrects the steering angle ω to the return side if it is in the OS state. Note that the correction amount (corrected steering angle) of the steering angle ω related to the steering angle correction processing is determined in advance through experimental adaptation and stored as a fixed value in the ROM.

  According to this steering angle correction process, the characteristic of the steering angle ω of the steered wheels with respect to the steering angle MA that is the steering input of the driver is changed, so that the driver tends to feel uncomfortable as compared with the driving force distribution process. On the other hand, since the control directly affects the steering angle of the steered wheels, the influence on the turning behavior of the vehicle 10 is larger than that in the driving force distribution process, and the turning behavior of the vehicle 10 is stabilized in a larger range of the vehicle state quantity S. It becomes possible to make it.

  When the steering angle correction process is executed, the ECU 100 determines whether or not the detected accelerator opening A is equal to or greater than a reference value Ath as an example of the “predetermined value” according to the present invention (step S106). Here, the reference value Ath is an adapted value that has been experimentally determined in advance as a possibility that the possibility that each wheel of the vehicle 10 will exceed the grip limit increases to a level that is practically difficult to ignore in the accelerator opening range beyond that. It is.

  In this embodiment, the accelerator opening A is used, but in the determination process in step S106, the accelerator opening A and other control amounts corresponding to one-to-one, one-to-many, many-to-one, or many-to-many. Physical quantities or index values may be used. For example, the opening degree of a throttle valve provided in the intake passage of engine 200 (that is, the throttle opening degree) may be used. At this time, as long as the correspondence relationship is defined in advance, the accelerator opening is indirectly specified through the throttle opening, and the operation of the “specifying means” according to the present invention is performed without any problem.

  If accelerator opening A is less than reference value A (step S106: NO), ECU 100 returns the process to step S101 and repeats a series of processes. In other words, in the behavior stabilization control, the turning behavior of the vehicle 10 is basically stabilized by the driving force distribution process and the steering angle correction process, and the discomfort to the driver is eliminated as much as possible. It has a configuration.

  On the other hand, when the accelerator opening A is equal to or greater than the reference value Ath (step S106: YES), the ECU 100 executes an information torque applying process (step S107). The case where step S106 branches to the “YES” side is an example of “when the accelerator opening specified during the period during which the behavior stabilizing means is controlled is greater than or equal to a predetermined value” according to the present invention.

  The information torque applying process is information for notifying the driver that the wheel grip limit is approaching from the above-described basic assist torque ATbase that assists the driver input torque MT with respect to the steering torque applied from the EPS actuator 500. It means a process of switching to the torque ATinf to call attention to the driver.

  The information torque ATinf is defined by the following equation (3). In the following formula (3), ATinfb is a reference information torque that defines a reference of information torque, and G1 is a gain.

ATinf = ATinfb · G1 (3)
Here, the reference information torque ATinfb will be described with reference to FIG. FIG. 4 is a graph showing the characteristic of the reference information torque ATinfb with respect to the vehicle state quantity S.

  In FIG. 4, the reference information torque ATinfb is zero in a range where the vehicle state quantity S is 0 or more and less than S2 (when the vehicle state quantity S is in this range, step S107 is not executed), and the vehicle state quantity S is In a range that is greater than or equal to S2, it linearly increases according to the vehicle state quantity S. Further, in a range where the vehicle state quantity S is equal to or greater than S2 '(S2'> S2), the vehicle state quantity S is saturated at the maximum value ATinfbmax.

  Particularly noteworthy in FIG. 4 is the direction in which the reference information torque ATinfb is applied. Unlike the basic assist torque ATbase described above, the reference information torque ATinfb is a torque applied in the neutral direction (substantially the switchback direction), that is, in the direction opposite to the driver input torque MT. Since the reference information torque ATinfb acts in the direction opposite to the driver input torque MT, when the application of the information torque ATinf is started, the steering wheel 16 is being steered or the steering wheel 16 is held. The driver in the middle perceives that the steering burden related to the cutting operation or the steering operation has suddenly increased. That is, the application of the information torque ATinf is information for notifying that the wheel has approached the grip limit.

  Next, the gain G1 will be described with reference to FIG. FIG. 5 is a diagram illustrating the characteristics of the gain G1 with respect to the accelerator opening A.

  In FIG. 5, the gain G1 is zero in the range less than the reference value Ath (in this range, the information torque ATinf is not applied), and linearly increases to the maximum value 1 with the reference value Ath as a boundary. 4 and 5 and the above equation (3), the information torque ATinf takes ATinfbmax as the maximum value, and as the accelerator opening A increases and the vehicle state quantity S increases, in other words, The closer to the grip limit, the greater. When the information torque ATinf is applied, the driver is significantly burdened with steering in the cutting direction. For example, the driver operates the steering wheel 16 to the cut back side. Alternatively, the accelerator opening A is decreased. As a result, when the information torque ATinf is applied, the vehicle state quantity S changes to the decreasing side, and the opportunity to activate the VSC process described later is reduced.

  Returning to FIG. 2, once the information torque applying process is executed, the ECU 100 determines whether or not the vehicle state quantity S is equal to or greater than the third reference value S3 (step S108). When the vehicle state quantity S is less than the third reference value S3 (step S108: NO), the ECU 100 returns the process to step S101 and repeats a series of processes.

  On the other hand, when the vehicle state quantity S is greater than or equal to the third reference value S3 (step S108: YES), the ECU 100 executes a VSC process (step S109).

  Here, the VSC process is a process for individually controlling the braking force of each wheel via the drive control of the brake actuator 600 to realize a so-called VSC (Vehicle Stability Control). More specifically, when the braking force applied to the wheel corresponding to the inside of the turning track of the vehicle 10 is increased with respect to the braking force applied to the wheel corresponding to the outside of the turning track, the turning behavior of the vehicle 10 becomes OS. When the braking force applied to the wheel corresponding to the inside of the turning track of the vehicle 10 is decreased with respect to the braking force applied to the wheel corresponding to the outside of the turning track, the turning behavior of the vehicle 10 changes to the US direction. To change. Using this characteristic, if the braking force is controlled as in the former if the turning behavior of the vehicle 10 is in the US state, and the latter in the case of the OS state, the turning behavior of the vehicle 10 is invited in the neutral steering direction. Is possible. When the VSC process is executed, the process returns to step S101. The behavior stabilization control is executed as described above.

  The VSC process uses the braking force applied to each wheel individually to stabilize the turning behavior of the vehicle. Even if the wheel is approaching the grip limit or exceeds the grip limit, the vehicle 10 It is a process that can invite the turning behavior of to the stabilization direction. Therefore, from the viewpoint of stabilizing the turning behavior of the vehicle 10, it can be said that the reliability is higher than the driving force distribution process and the steering angle correction process. On the other hand, such behavior stabilization using braking force has a greater significance of emergency avoidance operation than the other two processes, and the driver feels the most uncomfortable compared to the above two processes.

  However, according to the present embodiment, the information torque application process is activated before the VSC process is activated, and the vehicle state quantity S is changed to the decreasing side as described above by the information torque application process. In view of the high possibility, the VSC process clearly reduces the opportunity for activation compared to the control flow without the information torque application process. That is, according to the present embodiment, the vehicle behavior in the vicinity of the grip limit of the wheel or in the region exceeding the grip limit is prevented while maintaining the turning behavior in accordance with the driver's intention without giving the driver a sense of incongruity. Therefore, the behavior of the vehicle 10 can be stably maintained.

  Here, it supplements about the detail of the information torque provision process which concerns on step S107.

  As described above, the information torque applying process is a process of notifying the driver that the wheel grip limit is approaching, and therefore, the driver's reaction is likely to occur. The first thought as such a reaction is a change of the accelerator opening A to the decreasing side by loosening the accelerator pedal. When such a change in the accelerator opening A to the decreasing side occurs, the possibility of wheel grip reduction (that is, the shift to the US state as the steering state) due to an increase in accelerator depression decreases. The steering operation on the cut side of the steering wheel 16 that can be performed by the driver to rebuild the swung trajectory should be facilitated.

  Therefore, when the accelerator opening A decreases (for example, decreases to less than the reference value Ath) after the application of the information torque according to step S107, the ECU 100 reduces the steering torque applied from the EPS 500 to the normal torque again from the information torque ATinf. Return to basic assist torque ATbase. In the transition period of switching of the steering torque characteristic from the information torque ATinf to the basic assist torque ATbase, the transitional period basic assist torque ATbase 'is applied according to the following equation (4). Here, G2 is a gain.

ATbase '= ATbase · G2 (4)
Here, the gain G2 will be described with reference to FIG. FIG. 6 is a schematic diagram showing the characteristic of the gain G2 with respect to the change rate dA of the accelerator opening.

  In FIG. 6, the gain G2 is a region where the accelerator opening change rate dA (that is, the time differential value of the accelerator opening A) is less than dAth, that is, when the accelerator opening A decreases relatively slowly. Takes a maximum value of 1. On the other hand, when the accelerator opening change rate dA is equal to or greater than dAth, that is, when the accelerator opening A decreases relatively steeply, the gain G2 decreases nonlinearly as dA increases.

  This is because when the accelerator opening is suddenly reduced, the vehicle 10 tends to transition to the OS state transiently due to a so-called tuck-in phenomenon. That is, if a normal basic assist torque is applied to the vehicle that easily shifts to the OS state in the increasing direction, the vehicle 10 may shift to an excessive OS state and cause unstable behavior. The grant is started slowly.

  Here, the accelerator opening A is used as a criterion for switching the steering torque applied from the EPS 500 from the information torque ATinf to the assist torque ATbase, and the accelerator opening A is used to apply the information torque. The reference value Ath, which is a threshold value for starting, is exemplified for comparison, but the reference value used for such comparison may be different from the reference value Ath. Alternatively, on the condition that the accelerator opening A is decreased, such switching may be performed using another index value, physical quantity, or control quantity as a determination criterion.

  For example, the necessity for switching from the information torque to the assist torque described above may have a high correlation with the grip degree of the wheels. Therefore, it is possible to use the grip degree of the wheel instead of the accelerator opening A as this kind of determination criterion. At this time, for example, switching to the assist torque may be permitted or started when the grip degree reaches a preset reference value or exceeds the reference value. In addition, this reference value is set in multiple steps or as a continuous value, and switching to the assist torque in multiple steps or continuously (that is, substantially equivalent to gradually changing the assist torque). ) May be made.

  Further, the relationship between the accelerator opening A and this kind of index value, physical quantity, or control quantity that can include the grip degree, etc. is previously grasped experimentally, empirically, theoretically, or based on simulation. If this is the case, determination processing based on the accelerator opening may be performed with an accelerator opening that satisfies this kind of index value, physical quantity, or control amount as a threshold.

  In addition, switching from the information torque to the assist torque can be determined that the grip state of the wheel, which can take the grip degree of the wheel as a practical aspect, has been recovered to an extent that there is no practical problem, or experimentally in advance. Permitted when it can be determined that the vehicle behavior has been restored to an extent that does not cause instability of the vehicle behavior based on empirical, theoretical or simulation, etc. May be started.

  Next, the second thought as such a reaction is the operation of the steering wheel 16 without the operation of the accelerator pedal. This type of operation needs to be handled differently depending on the operation direction. That is, when the driver does not notice the information or loses his / her calmness when he / she notices it, and further operates the steering wheel 16 further (hereinafter referred to as “first case” as appropriate), This is the case where the driver notices the information but operates the steering wheel 16 to the switchback side without returning the accelerator opening A (hereinafter referred to as “second case” as appropriate).

  Here, the details of the gain G1 (gain multiplied by the basic assist torque ATbase) in each of the first and second cases will be described with reference to FIGS. FIG. 7 is a diagram illustrating the characteristics of the gain G1 with respect to the additional steering amount STR1, and FIG. 8 is a diagram illustrating the characteristics of the gain G1 with respect to the return steering amount STR2. That is, FIG. 7 corresponds to the first case, and FIG. 8 corresponds to the second case.

  In FIG. 7, the gain G <b> 1 is 1 in a relatively small increase area less than STR <b> 1 th, and takes a value larger than 1 in an area beyond it. That is, in the first case, the maximum value of the information torque ATinf acting in the switchback direction is larger than the above-described ATinfbmax, and the steering operation in the switch-over direction is further inhibited. The increase operation without the decrease in the accelerator opening A only induces the US state, and only invites the turning behavior of the vehicle 10 in a more unstable direction. By increasing the steering torque in the switchback direction in this way, it is possible to prevent such a situation from occurring.

  On the other hand, in FIG. 8, the gain G1 is 1 in a relatively small switchback region less than STR2th, and takes a value less than 1 in a region beyond that. That is, in the second case, the maximum value of the information torque ATinf acting in the switchback direction is smaller than the above-described ATinfbmax except for the initial switchback, and the steering operation in the switchback direction is performed by the driver itself. It is entrusted. Although there is no decrease in the accelerator opening A, there is no possibility of inducing an excessive US state if the steering operation is in the return direction. By reducing this, natural steering that respects the driver's will is realized.

  As described above, in the information torque application process, there is a subroutine (not shown) in FIG. 2, and thus, the stabilization of the turning behavior of the vehicle and the prevention of the driver from feeling uncomfortable are suitably realized. As a result, a situation in which the vehicle state quantity S increases to a region accompanied by the activation of the VSC process is prevented, and safer behavior control is realized within the range of the wheel grip limit.

  The present invention is not limited to the above-described embodiments, and can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

  The present invention can be used, for example, in a vehicle provided with means for stabilizing the turning behavior.

  FL, FR, RL, RR ... wheels, 10 ... vehicle, 16 ... steering wheel, 17 ... upper steering shaft, 18 ... lower steering shaft, 21 ... steering angle sensor, 22 ... steering torque sensor, 100 ... ECU, 200 ... engine , 300 ... Driving force distribution device, 400 ... VGRS actuator, 410 ... VGRS driving device, 500 ... EPS actuator, 510 ... EPS driving device, 600 ... Brake actuator.

Claims (6)

Behavior stabilization means including at least one of driving force distribution means capable of adjusting at least one of the front and rear and left and right driving force distribution and steering angle correction means capable of correcting the steering angle of the steered wheels;
An apparatus for controlling a vehicle comprising a steering torque applying means capable of applying a steering torque to a steering mechanism,
Detecting means for detecting at least one of an oversteer state and an understeer state;
First control means for controlling the behavior stabilizing means so that the detected at least one state is suppressed when the at least one state is detected;
Specifying means for specifying the accelerator opening of the vehicle;
When the specified accelerator opening is greater than or equal to a predetermined value during the period during which the behavior stabilizing means is controlled, the steering torque applying means is urged to alert the driver through the application of the steering torque. And a second control means for controlling the vehicle. The vehicle control device according to claim 1, wherein the second control unit applies the steering torque in a neutral direction. 3. The second control unit according to claim 1, wherein when the accelerator opening is decreased, the second control unit applies the steering torque in an increasing direction so as to reduce a driver's steering burden. 4. Vehicle control device. The second control means corrects the steering torque according to the direction of the steering input by the driver when the steering input by the driver occurs after the steering torque is applied to alert the driver. The vehicle control device according to any one of claims 1 to 3. The behavior stabilizing means includes braking means capable of independently applying braking force to each of the driving force distribution means, the steering angle correction means, and the wheels provided in the vehicle,
In suppressing the detected at least one state, the first control unit causes the behavior stabilizing unit to perform the driving force distribution unit according to a predetermined state quantity that defines the at least one detected state. , Sequentially control in the order of the turning angle correction means and the braking means,
The said 2nd control means controls the said steering torque provision means before the control of the said braking means is started in order to suppress the said at least one state detected, The any one of Claim 1 to 4 characterized by the above-mentioned. The vehicle control device according to claim 1. The vehicle control device according to any one of claims 1 to 5, wherein the steering mechanism is a mechanism capable of transmitting a steering force that prompts the steered wheels to steer the steered wheels.

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