JP4730543B2 - Vehicle driving force distribution control device - Google Patents

Vehicle driving force distribution control device Download PDF

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JP4730543B2
JP4730543B2 JP2006091063A JP2006091063A JP4730543B2 JP 4730543 B2 JP4730543 B2 JP 4730543B2 JP 2006091063 A JP2006091063 A JP 2006091063A JP 2006091063 A JP2006091063 A JP 2006091063A JP 4730543 B2 JP4730543 B2 JP 4730543B2
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force distribution
control amount
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JP2007261483A (en
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祐一 後田
祐介 藤井
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Mitsubishi Motors Corp
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本発明は車両の前後輪間の駆動力分配を制御する駆動力分配制御装置に関するものである。   The present invention relates to a driving force distribution control device that controls driving force distribution between front and rear wheels of a vehicle.

例えば電子制御式オンディマンド４輪駆動車では、エンジンからの駆動力を前輪または後輪の一方に伝達し、伝達した駆動力の一部を電子制御カップリングなどの駆動力分配装置を介して前輪または後輪の他方に分配し、駆動力分配の制御により適切な車両の走行特性を実現する技術が実用化されている（例えば、特許文献１参照）。
当該特許文献１に開示された技術は車両旋回時のアンダステアやオーバステアの抑制を目的としたものであり、ＦＲ車ベースの４輪駆動車に適用されている。車両の前後輪間には後輪の駆動力の一部を前輪側に分配する駆動力分配装置としてトランスファが設けられ、後輪の左右輪間には差動制限力を発生する差動制限装置が設けられ、旋回外輪の車輪速が旋回内輪の車輪速より高くて内輪がグリップしていると推測されるときには、トランスファによる前後輪間の駆動力分配を低めることで前輪に分配される駆動力を低下させると共に、差動制限装置による左右輪間の差動制限力を低下させ、これによりアンダステアの抑制を図っている。
特許第２５２７２０４号明細書 For example, in an electronically controlled on-demand four-wheel drive vehicle, the driving force from the engine is transmitted to one of the front wheels or the rear wheels, and a part of the transmitted driving force is transmitted to the front wheels or the rear via a driving force distribution device such as an electronically controlled coupling. A technique for distributing to the other of the rear wheels and realizing appropriate vehicle running characteristics by controlling driving force distribution has been put into practical use (for example, see Patent Document 1).
The technique disclosed in Patent Document 1 is intended to suppress understeer and oversteer during turning of the vehicle, and is applied to an FR vehicle-based four-wheel drive vehicle. A transfer limiting device is provided between the front and rear wheels of the vehicle as a driving force distribution device that distributes a part of the driving force of the rear wheel to the front wheel side, and generates a differential limiting force between the left and right wheels of the rear wheel. When the wheel speed of the outer turning wheel is higher than the wheel speed of the inner turning wheel and the inner wheel is estimated to be gripping, the driving force distributed to the front wheels is reduced by reducing the driving force distribution between the front and rear wheels by the transfer. And the differential limiting force between the left and right wheels by the differential limiting device is reduced, thereby suppressing understeer.
Japanese Patent No. 2527204

上記特許文献１の技術は左右輪間の差回転に着目してトランスファによる駆動力分配及び差動制限装置による差動制限力を制御しているが、左右輪間の差回転や前後輪間の差回転は車両の旋回状態を表す指標の一つに過ぎず、駆動力分配や差動制限力を適切に制御するには不十分であった。例えば左右輪間或いは前後輪間の差回転が同一条件であっても車両のステア特性がアンダステアであるかオーバステアであるかによって最適な駆動力分配や差動制限力が相違することから、結果として車両の旋回状態によってはトランスファの駆動力分配や差動制限装置の差動制限力が不適切に制御されて良好なステア特性を実現できないという問題が生じた。   The technique of Patent Document 1 focuses on the differential rotation between the left and right wheels, and controls the driving force distribution by the transfer and the differential limiting force by the differential limiting device. The differential rotation is only one of the indices indicating the turning state of the vehicle, and is insufficient for appropriately controlling the driving force distribution and the differential limiting force. For example, even if the differential rotation between the left and right wheels or the front and rear wheels is the same, the optimal driving force distribution and differential limiting force differ depending on whether the vehicle's steering characteristics are understeer or oversteer. Depending on the turning state of the vehicle, the driving force distribution of the transfer and the differential limiting force of the differential limiting device are improperly controlled, resulting in a problem that good steering characteristics cannot be realized.

本発明はこのような問題点を解決するためになされたもので、その目的とするところは、車両の旋回状態を端的に表す指標に基づいて前後輪間の駆動力分配を適切に制御でき、もって車両の旋回状態に関わらず良好なステア特性を実現することができる車両の駆動力分配制御装置を提供することにある。   The present invention has been made to solve such problems, and the object of the present invention is to appropriately control the driving force distribution between the front and rear wheels based on an index that represents the turning state of the vehicle. Accordingly, it is an object of the present invention to provide a driving force distribution control device for a vehicle that can realize a good steering characteristic regardless of the turning state of the vehicle.

上記目的を達成するため、請求項１の発明は、車両の前後輪間に設けられ、駆動源から前輪に伝達された駆動力の一部を後輪側に可変分配可能な駆動力分配手段と、車両の旋回状態に基づいて後輪側に分配させるべき駆動力分配に対する補正量として旋回対応制御量を算出する制御量算出手段と、車両の現在のステア特性を判定するステア特性判定手段と、前後輪の車輪速をそれぞれ検出する車輪速検出手段と、車輪速検出手段による検出結果に基づき前輪の車輪速が後輪の車輪速より高いと判定した場合、ステア特性判定手段により判定されたステア特性がアンダステアのときには前後輪間の駆動力分配を旋回対応制御量に基づき増加補正する一方、ステア特性がオーバステアのときには前後輪間の駆動力分配を旋回対応制御量に基づき減少補正し、前輪の車輪速が後輪の車輪速より低いと判定した場合、ステア特性判定手段により判定されたステア特性に関わらず前後輪間の駆動力分配を旋回対応制御量に基づき減少補正し、補正後の駆動力分配に基づいて駆動力分配手段を制御する駆動力分配制御手段とを備えたものである。 In order to achieve the above object, the invention of claim 1 is provided between the front and rear wheels of the vehicle , and driving force distribution means capable of variably distributing a part of the driving force transmitted from the driving source to the front wheels to the rear wheels. A control amount calculating means for calculating a control amount corresponding to turning as a correction amount for driving force distribution to be distributed to the rear wheel side based on a turning state of the vehicle, a steer characteristic determining means for determining a current steering characteristic of the vehicle, When it is determined that the wheel speed of the front wheel is higher than the wheel speed of the rear wheel based on the detection result by the wheel speed detecting means and the wheel speed detecting means for detecting the wheel speeds of the front and rear wheels respectively , the steer characteristic determined by the steer characteristic determining means When the characteristic is understeer, the driving force distribution between the front and rear wheels is increased and corrected based on the turning control amount. When the steering characteristic is oversteer, the driving force distribution between the front and rear wheels is reduced based on the turning control amount. Corrected, if the front wheel speed is determined to be lower than the wheel speed of the rear wheels, decrease corrected on the basis of the turning corresponding control variable the driving force distribution between the front and rear wheels regardless of the steering characteristic which is determined by the steering characteristic determination means And a driving force distribution control unit that controls the driving force distribution unit based on the corrected driving force distribution .

従って、車両の旋回状態に基づいて制御量算出手段により後輪側に分配させるべき駆動力分配に対する補正量として旋回対応制御量が算出されると共に、ステア特性判定手段により現在の車両のステア特性が判定され、前後輪の車輪速が車輪速検出手段により検出される。前後輪間の駆動力分配によるトルク移動は車輪速の高い側から低い側へと行われるため、前輪の車輪速が後輪の車輪速より高い場合には駆動力分配手段を介して前輪から後輪へとトルクが移動しており、アンダステアであるとして旋回対応制御量に基づき駆動力分配が増加補正されると、前輪の駆動力低下に伴って横力が増加してヨーモーメントの増加によりアンダステアが抑制され、オーバステアであるとして駆動力分配が減少補正されると、後輪の駆動力低下に伴って横力が増加してヨーモーメントの低下によりオーバステアが抑制される。 Therefore, the control amount calculation means calculates the turning correspondence control amount as a correction amount for the driving force distribution to be distributed to the rear wheels based on the turning state of the vehicle, and the steering characteristic determination means determines the current vehicle steering characteristic. The wheel speed of the front and rear wheels is detected and detected by the wheel speed detecting means. Torque movement by the driving force distribution between the front and rear wheels is performed from the high wheel speed side to the low wheel speed side. Therefore, when the front wheel speed is higher than the rear wheel speed, the rear wheel is moved from the front wheel through the driving force distributing means. If the torque is moving to the wheel and the driving force distribution is increased and corrected based on the turning control amount because it is understeering, the lateral force increases as the driving force of the front wheels decreases, and the yaw moment increases, causing the understeering. When the driving force distribution is corrected to decrease because the steering is oversteered, the lateral force increases as the driving force of the rear wheels decreases, and the oversteer is suppressed due to the decrease of the yaw moment.

また、前輪の車輪速が後輪の車輪速より低い場合には駆動力分配手段を介して後輪から前輪へとトルクが移動し、前輪が後輪側から逆駆動されると共に、後輪が制動力（負の駆動力）を発生しており、アンダステアの場合に駆動力分配が減少補正されると、前輪の駆動力低下に伴って横力が増加してヨーモーメントの増加によりアンダステアが抑制され、オーバステアの場合に駆動力分配が減少補正されると、後輪の制動力低下に伴って横力が増加してヨーモーメントの低下によりオーバステアが抑制される。これにより前後輪の車輪速のみならず車両のステア特性も反映して統合的に前後輪の他方側に分配させるべき駆動力分配が制御され、車両の旋回状態に関わらず良好なステア特性が実現される。 Also, when the front wheel speed is lower than the rear wheel speed, the torque moves from the rear wheel to the front wheel via the driving force distributing means, the front wheel is reversely driven from the rear wheel side, and the rear wheel When braking force (negative driving force) is generated and the driving force distribution is corrected to decrease in the case of understeer, the lateral force increases as the driving force of the front wheels decreases, and understeer is suppressed by increasing the yaw moment. If the driving force distribution is corrected to decrease in the case of oversteering, the lateral force increases as the braking force of the rear wheels decreases, and the oversteer is suppressed due to the decrease in yaw moment. This controls the driving force distribution that should be distributed to the other side of the front and rear wheels in an integrated manner, reflecting not only the wheel speeds of the front and rear wheels, but also the vehicle's steering characteristics, realizing good steering characteristics regardless of the turning state of the vehicle Is done.

請求項２の発明は、車両の前後輪間に設けられ、駆動源から後輪に伝達された駆動力の一部を前輪側に可変分配可能な駆動力分配手段と、車両の旋回状態に基づいて前輪側に分配させるべき駆動力分配に対する補正量として旋回対応制御量を算出する制御量算出手段と、車両の現在のステア特性を判定するステア特性判定手段と、前後輪の車輪速をそれぞれ検出する車輪速検出手段と、車輪速検出手段による検出結果に基づき後輪の車輪速が前輪の車輪速より高いと判定した場合、ステア特性判定手段により判定されたステア特性がアンダステアのときには前後輪間の駆動力分配を旋回対応制御量に基づき減少補正する一方、ステア特性がオーバステアのときには前後輪間の駆動力分配を旋回対応制御量に基づき増加補正し、後輪の車輪速が前輪の車輪速より低いと判定した場合、ステア特性判定手段により判定されたステア特性に関わらず前後輪間の駆動力分配を旋回対応制御量に基づき減少補正し、補正後の駆動力分配に基づいて駆動力分配手段を制御する駆動力分配制御手段とを備えたものである。 The invention of claim 2 is provided between the front and rear wheels of the vehicles, a part of the driving force transmitted to the rear wheel from a drive source and a variable dispensable driving force distributing means to the front wheel side, a turning state of the vehicle Control amount calculation means for calculating a control amount corresponding to turning as a correction amount for driving force distribution to be distributed to the front wheel based on, steer characteristic determination means for determining the current steering characteristic of the vehicle, and wheel speeds of the front and rear wheels respectively When it is determined that the wheel speed of the rear wheel is higher than the wheel speed of the front wheel based on the detection result by the wheel speed detecting means and the wheel speed detecting means, the front and rear wheels are determined when the steer characteristic determined by the steer characteristic determining means is understeer. While the steering force is oversteer, the driving force distribution between the front and rear wheels is increased and corrected based on the turning control amount. If it is determined to be lower than the wheel speed of the wheels, the steering characteristic determination means by reducing corrected on the basis of the turning corresponding control variable the driving force distribution between the front and rear wheels regardless of the steering characteristic is determined, based on the driving force distribution of the corrected Driving force distribution control means for controlling the driving force distribution means .

従って、車両の旋回状態に基づいて制御量算出手段により前輪側に分配させるべき駆動力分配に対する補正量として旋回対応制御量が算出されると共に、ステア特性判定手段により現在の車両のステア特性が判定され、前後輪の車輪速が車輪速検出手段により検出される。前後輪間の駆動力分配によるトルク移動は車輪速の高い側から低い側へと行われるため、後輪の車輪速が前輪の車輪速より高い場合には駆動力分配手段を介して後輪から前輪へとトルクが移動しており、アンダステアであるとして旋回対応制御量に基づき駆動力分配が減少補正されると、前輪の駆動力低下に伴って横力が増加してヨーモーメントの増加によりアンダステアが抑制され、オーバステアであるとして駆動力分配が増加補正されると、後輪の駆動力低下に伴って横力が増加してヨーモーメントの低下によりオーバステアが抑制される。 Accordingly, the control amount calculation means calculates the turning correspondence control amount as a correction amount for the driving force distribution to be distributed to the front wheels based on the turning state of the vehicle, and the steering characteristic determination means determines the current steering characteristic of the vehicle. The wheel speeds of the front and rear wheels are detected by the wheel speed detecting means. The torque movement by the driving force distribution between the front and rear wheels is performed from the high wheel speed side to the low wheel speed side. Therefore, when the wheel speed of the rear wheel is higher than the wheel speed of the front wheel, from the rear wheel through the driving force distribution means. If the torque is moving to the front wheel and the driving force distribution is corrected to be reduced based on the turning control amount because it is understeering, the lateral force increases as the driving force of the front wheel decreases and the yaw moment increases, causing the understeering. If the driving force distribution is corrected to increase due to the suppression of oversteering, the lateral force increases as the driving force of the rear wheels decreases, and the oversteer is suppressed due to the decrease in yaw moment.

また、後輪の車輪速が前輪の車輪速より低い場合には駆動力分配手段を介して前輪から後輪へとトルクが移動し、後輪が前輪側から逆駆動されると共に、前輪が制動力（負の駆動力）を発生しており、アンダステアの場合に駆動力分配が減少補正されると、前輪の制動力低下に伴って横力が増加してヨーモーメントの増加によりアンダステアが抑制され、オーバステアの場合に駆動力分配が減少補正されると、後輪の駆動力低下に伴って横力が増加してヨーモーメントの低下によりオーバステアが抑制される。これにより前後輪の車輪速のみならず車両のステア特性も反映して統合的に前後輪の他方側に分配させるべき駆動力分配が制御され、車両の旋回状態に関わらず良好なステア特性が実現される。
好ましい態様として、制御量算出手段を、旋回対応制御量に加えて、前後輪の車輪速の差に基づく差回転対応制御量、アクセル操作に伴う車両の加速状態に基づく加速対応制御量、及びブレーキ操作に伴う車両の減速状態に基づく減速対応制御量などの内の少なくとも一つを駆動力分配のベース制御量として算出するように構成し、駆動力分配制御手段を、ベース制御量を旋回対応制御量に基づいて増加補正または減少補正するように構成することが望ましい。
従って、駆動力分配のベース制御量として差回転対応制御量、加速対応制御量、減速対応制御量の内の少なくとも一つが算出され、このベース制御量が旋回対応制御量に基づいて増加補正または減少補正される。即ち、ベース制御量に対して旋回対応制御量に基づく補正が行われるため、増加補正のみならず減少補正も常に可能となり、旋回対応制御量を確実に前後輪の他方側に分配させるべき駆動力分配に反映させることができる。
請求項３の発明は、請求項１または２において、ステア特性判定手段が、車両の走行状態に基づいて目標旋回状態指標を決定する目標旋回状態指標決定手段と、車両の実際の旋回状態指標を検出する実旋回状態指標検出手段とを備え、目標旋回状態指標と実旋回状態指標とに基づき現在の車両のステア特性を判定すると共に、制御量算出手段が、ステア特性判定手段によりステア特性として判定されたアンダステア及びオーバステアに基づき前後輪のスリップ輪を特定し、スリップ輪の駆動力及び横力からグリップ限界と相関するグリップ限界指標を推定するグリップ限界指標推定手段と、車両の旋回状態に基づいてアンダステアまたはオーバステアを抑制するための要求ヨーモーメントを算出し、要求ヨーモーメントを達成可能なスリップ輪の要求横力を算出する要求横力算出手段と、グリップ限界指標算出手段により算出されたグリップ限界指標を前提として、要求横力算出手段により算出された要求横力を達成するために必要なスリップ輪の駆動力低下量を算出する駆動力低下量算出手段とを備え、駆動力低下量算出手段により算出されたスリップ輪の駆動力低下量に応じて旋回対応制御量を算出するものである。
従って、目標旋回状態指標決定手段により決定された目標旋回状態指標と、実旋回状態指標検出手段により検出された実際の旋回状態指標とに基づき車両のステア特性が判定される。車両旋回中のアンダステアの発生は前輪の横力不足によるスリップに起因し、オーバステアの発生は後輪の横力不足によるスリップに起因するため、ステア特性としてアンダステアが判定されたときには前輪がスリップ輪として特定され、オーバステアのときには後輪がスリップ輪として特定される。
そして、スリップ輪の駆動力及び横力からグリップ限界と相関するグリップ限界指標、例えば駆動力及び横力に対するグリップ限界を規定する摩擦円がグリップ限界指標推定手段により推定される。さらに車両の旋回状態に基づいて要求横力算出手段によりアンダステアまたはオーバステアを抑制するための要求ヨーモーメントが算出された上で、要求ヨーモーメントを達成可能なスリップ輪の要求横力が算出され、グリップ限界指標を前提として要求横力を達成するためのスリップ輪の駆動力低下量が駆動力低下量算出手段により算出され、この駆動力低下量に応じて制御量算出手段により旋回対応制御量が算出される。
即ち、具体的な目標旋回状態指標と実旋回状態指標に基づいて車両のステア特性が判定される一方、スリップ輪のグリップ限界と相関するグリップ限界指標を前提とし、ステア特性として判定されたアンダステアやオーバステアを抑制するための要求ヨーモーメント、要求ヨーモーメントを達成可能なスリップ輪の要求横力、要求横力を達成するためのスリップ輪の駆動力低下量などの具体的な算出値に基づいて旋回対応制御量が算出されるため、例えば過去の経験則や実験結果に基づいて旋回対応制御量を設定する場合などに比較して、より現実に即した旋回対応制御量を算出可能となる。
好ましい態様として、上記要求横力算出手段を、車両の旋回状態から決定した目標ヨーレイトと実際のヨーレイトとの偏差に基づき、アンダステアまたはオーバステアを抑制するための要求ヨーモーメントを算出し、該要求ヨーモーメントからスリップ輪の要求横力を算出するように構成することが望ましい。
このように構成すれば、車両の旋回状態を端的に表すヨーレイトに基づいて適切な要求ヨーモーメント、ひいては一層適切な旋回対応制御量を算出することができる。 Also, when the rear wheel speed is lower than the front wheel speed, the torque moves from the front wheel to the rear wheel via the driving force distribution means, the rear wheel is driven backward from the front wheel side, and the front wheel is controlled. When power (negative driving force) is generated and the driving force distribution is corrected to decrease in the case of understeer, the lateral force increases as the braking force of the front wheels decreases, and understeer is suppressed due to the increase in yaw moment. When the driving force distribution is corrected to decrease in the case of oversteer, the lateral force increases as the driving force of the rear wheels decreases, and the oversteer is suppressed due to the decrease in yaw moment. This controls the driving force distribution that should be distributed to the other side of the front and rear wheels in an integrated manner, reflecting not only the wheel speeds of the front and rear wheels, but also the vehicle's steering characteristics, realizing good steering characteristics regardless of the turning state of the vehicle Is done.
As a preferred embodiment, the control amount calculation means includes a control amount for differential rotation based on a difference in wheel speed between the front and rear wheels, an acceleration corresponding control amount based on an acceleration state of the vehicle accompanying an accelerator operation, and a brake It is configured to calculate at least one of the deceleration control amount based on the deceleration state of the vehicle accompanying the operation as the base control amount of the driving force distribution, and the driving force distribution control means controls the base control amount to turn. It is desirable to configure to increase or decrease based on the amount.
Accordingly, at least one of the control amount corresponding to the differential rotation, the control amount corresponding to the acceleration, and the control amount corresponding to the deceleration is calculated as the base control amount of the driving force distribution, and this base control amount is corrected to increase or decrease based on the turning control amount. It is corrected. That is, since the base control amount is corrected based on the turning control amount, not only the increase correction but also the reduction correction is always possible, and the driving force that should reliably distribute the turning control amount to the other side of the front and rear wheels. It can be reflected in the distribution.
According to a third aspect of the present invention, in the first or second aspect, the steer characteristic determining unit includes a target turning state index determining unit that determines a target turning state index based on a running state of the vehicle, and an actual turning state index of the vehicle. An actual turning state index detecting means for detecting, and determining the steering characteristic of the current vehicle based on the target turning state index and the actual turning state index, and the control amount calculating means is determined as the steer characteristic by the steer characteristic determining means Grip limit index estimating means for identifying the front and rear slip wheels based on the understeer and oversteer and estimating the grip limit index correlating with the grip limit from the driving force and lateral force of the slip wheel, and based on the turning state of the vehicle Calculates the required yaw moment to suppress understeer or oversteer and can achieve the required yaw moment Slip required to achieve the required lateral force calculated by the required lateral force calculating means on the premise of the required lateral force calculating means for calculating the required lateral force and the grip limit index calculated by the grip limit index calculating means Driving force reduction amount calculating means for calculating the driving force reduction amount of the wheel, and calculating a turning correspondence control amount according to the driving force reduction amount of the slip wheel calculated by the driving force reduction amount calculation means.
Accordingly, the steering characteristic of the vehicle is determined based on the target turning state index determined by the target turning state index determination unit and the actual turning state index detected by the actual turning state index detection unit. The occurrence of understeer during turning of the vehicle is caused by slip due to insufficient lateral force of the front wheel, and occurrence of oversteer is caused by slip due to insufficient lateral force of the rear wheel, so when the understeer is determined as the steer characteristic, the front wheel becomes a slip wheel. When the vehicle is oversteered, the rear wheel is specified as a slip wheel.
Then, a grip limit index correlating with the grip limit from the driving force and lateral force of the slip wheel, for example, a friction circle defining a grip limit for the driving force and the lateral force is estimated by the grip limit index estimating means. Further, after calculating the required yaw moment for suppressing understeer or oversteer by the required lateral force calculation means based on the turning state of the vehicle, the required lateral force of the slip wheel that can achieve the required yaw moment is calculated, and the grip The driving force decrease amount of the slip wheel for achieving the required lateral force on the assumption of the limit index is calculated by the driving force decrease amount calculating means, and the turning control amount is calculated by the control amount calculating means according to the driving force decrease amount. Is done.
That is, the vehicle steer characteristic is determined based on the specific target turning state index and the actual turning state index, and on the premise of the grip limit index that correlates with the grip limit of the slip wheel, Turning based on specific calculated values such as the required yaw moment to suppress oversteer, the required lateral force of the slip wheel that can achieve the required yaw moment, and the amount of decrease in the driving force of the slip wheel to achieve the required lateral force Since the corresponding control amount is calculated, it is possible to calculate the turn corresponding control amount that is more realistic compared to, for example, the case where the turn corresponding control amount is set based on past empirical rules and experimental results.
As a preferred aspect, the required lateral force calculating means calculates a required yaw moment for suppressing understeer or oversteer based on a deviation between the target yaw rate determined from the turning state of the vehicle and the actual yaw rate, and the required yaw moment It is desirable that the required lateral force of the slip wheel is calculated from the above.
With such a configuration, it is possible to calculate an appropriate required yaw moment and thus a more appropriate turning correspondence control amount based on a yaw rate that directly represents the turning state of the vehicle.

以上説明したように請求項１の発明の車両の駆動力分配制御装置によれば、前輪の駆動力の一部を後輪に分配する車両において、車両の旋回状態を端的に表す現在のステア特性と前後輪の車輪速の大小関係との組合せに応じて前後輪間の駆動力分配を増加補正または減少補正するため、前後輪間の駆動力分配を適切に制御でき、もってアンダステアやオーバステアを確実に抑制することができる。
請求項２の発明の車両の駆動力分配制御装置によれば、後輪の駆動力の一部を前輪に分配する車両において、車両の旋回状態を端的に表す現在のステア特性と前後輪の車輪速の大小関係との組合せに応じて前後輪間の駆動力分配を増加補正または減少補正するため、前後輪間の駆動力分配を適切に制御でき、もってアンダステアやオーバステアを確実に抑制することができる。
請求項３の発明の車両の駆動力分配制御装置によれば、請求項１または２に加えて、具体的な目標旋回状態指標と実旋回状態指標に基づいて車両のステア特性を判定した上で、スリップ輪のグリップ限界と相関するグリップ限界指標を前提とし、ステア特性として判定されたアンダステアやオーバステアを抑制するための要求ヨーモーメント、スリップ輪の要求横力や駆動力低下量などの具体的な算出値に基づいて駆動力分配手段に適用する旋回対応制御量を算出するため、より現実に即した旋回対応制御量に基づいて前後輪間の駆動力分配を適切に制御でき、車両のアンダステアやオーバステアを確実に抑制することができる。 As described above, according to the vehicle driving force distribution control device of the first aspect of the present invention, in the vehicle that distributes a part of the driving force of the front wheels to the rear wheels, the current steering characteristic that directly represents the turning state of the vehicle. Since the driving force distribution between the front and rear wheels is corrected to increase or decrease according to the combination of the front and rear wheel speeds, the driving force distribution between the front and rear wheels can be controlled appropriately, thereby ensuring understeer and oversteer. Can be suppressed .
According to the vehicle driving force distribution control device of the second aspect of the present invention, in the vehicle that distributes a part of the driving force of the rear wheels to the front wheels, the current steering characteristic that directly represents the turning state of the vehicle and the wheels of the front and rear wheels Since the driving force distribution between the front and rear wheels is corrected to increase or decrease according to the combination with the magnitude relationship of the speed, the driving force distribution between the front and rear wheels can be controlled appropriately, thereby reliably suppressing understeer and oversteer. it can.
According to the driving force distribution control device for a vehicle of the invention of claim 3 , in addition to claim 1 or 2 , after determining the steering characteristic of the vehicle based on the specific target turning state index and the actual turning state index. Based on the grip limit index that correlates with the grip limit of the slip wheel, the specific yaw moment to suppress the understeer and oversteer determined as the steer characteristics, the required lateral force of the slip wheel, the amount of decrease in driving force, etc. Since the turning control amount applied to the driving force distribution means is calculated based on the calculated value, the driving force distribution between the front and rear wheels can be appropriately controlled based on the turning correspondence control amount that is more realistic, and the vehicle understeer and Oversteer can be reliably suppressed.

[第１実施形態]
以下、本発明をＦＦ車ベースの電子制御式オンディマンド４輪駆動車の前後輪間の駆動力分配を制御する駆動力分配制御装置に具体化した第１実施形態を説明する。
図１は本実施形態の車両の駆動力分配制御装置を示す全体構成図である。車両前部にはフロントディファレンシャル１（以下、フロントデフと称する）が設けられ、フロントデフ１に固定されたリングギア２には図示しないエンジンの駆動力が変速機を介して入力される。フロントデフ１にはドライブシャフト３を介して左右の前輪４が接続され、フロントデフ１はリングギア２に入力されたエンジンの駆動力を、差動を許容しながら左右の前輪４に伝達する。フロントデフ１にはフロント電子制御ＬＳＤ５が併設され、当該フロント電子制御ＬＳＤ５は内蔵された図示しない電磁クラッチの係合状態に応じて左右前輪４間に差動制限力を作用させる。 [First embodiment]
Hereinafter, a first embodiment in which the present invention is embodied in a driving force distribution control device that controls driving force distribution between front and rear wheels of an electronically controlled on-demand four-wheel drive vehicle based on an FF vehicle will be described.
FIG. 1 is an overall configuration diagram showing a vehicle driving force distribution control apparatus according to this embodiment. A front differential 1 (hereinafter referred to as a front differential) is provided at the front of the vehicle, and an engine driving force (not shown) is input to the ring gear 2 fixed to the front differential 1 via a transmission. The front differential 1 is connected to the left and right front wheels 4 via a drive shaft 3. The front differential 1 transmits the driving force of the engine input to the ring gear 2 to the left and right front wheels 4 while allowing a differential. The front differential 1 is provided with a front electronic control LSD5, and the front electronic control LSD5 applies a differential limiting force between the left and right front wheels 4 in accordance with an engagement state of an electromagnetic clutch (not shown) incorporated therein.

フロントデフ１のリングギア２にはフロントプロペラシャフト６の前端に固定されたピニオンギア７が噛合し、フロントプロペラシャフト６の後端は電子制御カップリング８（駆動力分配手段）を介してリアプロペラシャフト９の前端に接続されている。リアプロペラシャフト９の後端に固定されたピニオンギア１０はリアディファレンシャル１１（以下、リアデフと称する）のリングギア１２に噛合し、リアデフ１１にはドライブシャフト１３を介して左右の後輪１４が接続されている。   The ring gear 2 of the front differential 1 meshes with a pinion gear 7 fixed to the front end of the front propeller shaft 6, and the rear end of the front propeller shaft 6 is connected to the rear propeller via an electronic control coupling 8 (driving force distribution means). It is connected to the front end of the shaft 9. A pinion gear 10 fixed to the rear end of the rear propeller shaft 9 meshes with a ring gear 12 of a rear differential 11 (hereinafter referred to as rear differential), and left and right rear wheels 14 are connected to the rear differential 11 via a drive shaft 13. Has been.

エンジンの駆動力の一部はフロントデフ１からプロペラシャフト６，９及び電子制御カップリング８を介してリアデフ１１側に分配され、リアデフ１１により差動を許容されながら左右の後輪１４に伝達される。電子制御カップリング８は内蔵された図示しない電磁クラッチの係合状態に応じて前輪４側から後輪１４側に分配される駆動力、即ち、前後輪４，１４間の駆動力分配を調整する。なお、駆動力配分を調整する原理はこれに限ることはなく、ポンプやモータなどの制御デバイスを利用して駆動力配分を調整可能なのもであれば任意に変更可能であり、例えば油圧ポンプから供給した作動油により油圧ピストンを作動させてクラッチの係合状態を調整してもよい。   A part of the driving force of the engine is distributed from the front differential 1 to the rear differential 11 side through the propeller shafts 6 and 9 and the electronic control coupling 8, and is transmitted to the left and right rear wheels 14 while allowing the differential differential. The The electronic control coupling 8 adjusts the driving force distributed from the front wheel 4 side to the rear wheel 14 side, that is, the driving force distribution between the front and rear wheels 4, 14 in accordance with the state of engagement of a built-in electromagnetic clutch (not shown). . The principle of adjusting the driving force distribution is not limited to this, and any change can be made as long as the driving force distribution can be adjusted using a control device such as a pump or a motor. The engagement state of the clutch may be adjusted by operating the hydraulic piston with the supplied hydraulic oil.

一方、車両の室内には４ＷＤ用ＥＣＵ２１が設置され、この４ＷＤ用ＥＣＵ２１は図示しない入出力装置、制御プログラムや制御マップ等の記憶に供される記憶装置（ＲＯＭ，ＲＡＭ等）、中央処理装置（ＣＰＵ）、タイマカウンタ等を備えている。４ＷＤ用ＥＣＵ２１の入力側には、ステアリングの操舵角θstrを検出する操舵角センサ２２、車速Ｖを検出する車速センサ２３、車両のヨーレイトＹＲを検出するヨーレイトセンサ２４、車両の各輪４，１４の車輪速ＮFR,ＮFL,ＮRR,ＮRLを検出する車輪速センサ２５、車両旋回時に発生する横加速度ＧＹを検出する横加速度センサ２６などの各種センサ類が接続され、４ＷＤ用ＥＣＵ２１の出力側には、上記フロント電子制御ＬＳＤ５の電磁クラッチ及び電子制御カップリング８の電磁クラッチなどの各種デバイス類が接続されている。   On the other hand, a 4WD ECU 21 is installed in the interior of the vehicle. The 4WD ECU 21 includes an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, and a central processing unit ( CPU), a timer counter, and the like. On the input side of the 4WD ECU 21 are a steering angle sensor 22 that detects the steering angle θstr of the steering, a vehicle speed sensor 23 that detects the vehicle speed V, a yaw rate sensor 24 that detects the yaw rate YR of the vehicle, and the wheels 4 and 14 of the vehicle. Various sensors such as a wheel speed sensor 25 for detecting wheel speeds NFR, NFL, NRR, NRL and a lateral acceleration sensor 26 for detecting a lateral acceleration GY generated when the vehicle turns are connected, and on the output side of the ECU for 4WD, Various devices such as the electromagnetic clutch of the front electronic control LSD 5 and the electromagnetic clutch of the electronic control coupling 8 are connected.

４ＷＤ用ＥＣＵ２１は上記各種センサからの検出情報に基づいてフロント電子制御ＬＳＤ５や電子制御カップリング８の電磁クラッチの係合状態を制御する。本実施形態では車両旋回時のアンダステアやオーバステアの抑制を目的として、前後輪４，１４のグリップ限界と相関する摩擦円（グリップ限界指標）に基づき電子制御カップリング８による前後輪４，１４間の駆動力分配の制御を実行しており、以下、当該電子制御カップリング８の制御量の設定手順を説明する。   The 4WD ECU 21 controls the engagement state of the electromagnetic clutch of the front electronic control LSD 5 and the electronic control coupling 8 based on the detection information from the various sensors. In the present embodiment, for the purpose of suppressing understeer and oversteer during turning of the vehicle, based on a friction circle (grip limit index) correlated with the grip limit of the front and rear wheels 4, 14, the distance between the front and rear wheels 4, 14 by the electronically controlled coupling 8 is determined. The control of the driving force distribution is executed, and the procedure for setting the control amount of the electronic control coupling 8 will be described below.

電子制御カップリング８の制御量の設定は、車両のステア特性がアンダステアであるかオーバステアであるかに応じて異なる手順で実行されるため、ステア特性毎に場合分けして説明する。本実施形態ではＥＣＵ２１はヨーレイトセンサ２４（実旋回状態指標検出手段）により検出された実ヨーレイトＹＲ（実旋回状態指標）と後述する目標ヨーレイトＹＴ（目標旋回状態指標）との比較結果に基づいて現在車両に発生しているステア特性を判定した上で（ステア特性判定手段）、ステア特性に応じた制御量の設定を実行している。但し、ステア特性の判定手法はこれに限るものではなく任意に変更可能である。   The setting of the control amount of the electronically controlled coupling 8 is executed according to a different procedure depending on whether the steering characteristic of the vehicle is understeer or oversteer, and will be described separately for each steering characteristic. In the present embodiment, the ECU 21 is currently based on a comparison result between an actual yaw rate YR (actual turning state index) detected by the yaw rate sensor 24 (actual turning state index detecting means) and a target yaw rate YT (target turning state index) described later. After determining the steering characteristic occurring in the vehicle (steer characteristic determination means), the control amount is set according to the steering characteristic. However, the steer characteristic determination method is not limited to this, and can be arbitrarily changed.

図２はアンダステア発生時にＥＣＵ２１により実行される電子制御カップリング８の制御量の設定手順を示すブロック図、図３，４は設定された制御量に基づく駆動力分配の制御状況を示す模式図であり、まず、これらの図に従ってアンダステアが発生した場合について述べる。なお、図３，４は左右前輪４の車輪速ＮFR,ＮFL及び左右後輪１４の車輪速ＮRR,ＮRLを平均化して２輪モデルとして模式的に表しており、図３は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い場合を示し、図４は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い場合を示している。   FIG. 2 is a block diagram showing a procedure for setting the control amount of the electronic control coupling 8 that is executed by the ECU 21 when understeer occurs, and FIGS. 3 and 4 are schematic views showing a control state of driving force distribution based on the set control amount. First, the case where understeer occurs according to these figures will be described. 3 and 4 schematically show a two-wheel model by averaging the wheel speeds NFR and NFL of the left and right front wheels 4 and the wheel speeds NRR and NRL of the left and right rear wheels 14, and FIG. 3 shows the average front wheel speed NFave. FIG. 4 shows a case where the rear wheel average wheel speed NRave is lower than the rear wheel average wheel speed NRave.

また、図３，４において、前後輪４，１４に付した上下方向の黒塗り直線矢印Ａdrvの長さ及び方向は駆動力の大きさ及び方向（駆動か制動か）を表し、前後輪４，１４に付した左方向の黒塗り直線矢印Ａcorneringの長さは横力の大きさを表し、これに対して白抜き直線矢印Ａdrv，Ａcorneringはステア特性に応じた制御量（ヨーレイト対応制御量Ｔy）に基づく駆動力および横力に対する補正状況を表している。また、前後輪４，１４に付した白抜き回転矢印Ａrevの長さは前輪平均車輪速ＮFave及び後輪平均車輪速ＮRaveを表し、前後輪４，１４間の黒塗り直線矢印Ａtrqの長さ及び方向は電子制御カップリング８の最終制御量Ｔに応じた駆動力分配によるトルク移動量及び移動方向を表している。   3 and 4, the length and direction of the vertical black solid arrows Adrv attached to the front and rear wheels 4 and 14 indicate the magnitude and direction of driving force (whether driving or braking). The length of the black solid straight arrow Acornering in the left direction attached to 14 represents the magnitude of the lateral force, while the white straight arrows Adrv and Acornering are control amounts corresponding to the steering characteristics (control rate Ty corresponding to yaw rate). The correction | amendment condition with respect to the driving force and lateral force based on is represented. The lengths of the white rotating arrows Arev attached to the front and rear wheels 4 and 14 represent the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave. The direction represents the torque movement amount and the movement direction by the driving force distribution according to the final control amount T of the electronic control coupling 8.

車両のアンダステアは前輪４の横力不足によるスリップに起因する現象であり、このときの前輪４は自己の摩擦円により規定される駆動力及び横力に対するグリップを限界まで使用しているものと推測でき、換言すれば、前輪４の駆動力の低下により横力を増加させてアンダステアを抑制できる余地があると解釈できる。一方、前輪４の駆動力は、電子制御カップリング８を介して前輪４から後輪１４に分配されるトルク、或いは後輪１４から前輪４に伝達されるトルクに応じて変化するため、前後輪４，１４間の駆動力分配に応じて調整可能である。   Understeer of the vehicle is a phenomenon caused by slip due to insufficient lateral force of the front wheel 4, and it is assumed that the front wheel 4 at this time uses the driving force and the grip against the lateral force defined by its own friction circle to the limit. In other words, it can be interpreted that there is room for increasing the lateral force by reducing the driving force of the front wheels 4 and suppressing understeer. On the other hand, the driving force of the front wheel 4 changes according to the torque distributed from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8 or the torque transmitted from the rear wheel 14 to the front wheel 4. 4 and 14 can be adjusted according to the driving force distribution.

以上の観点の下に図２に従ってアンダステア時の電子制御カップリング８の制御量が設定される。まず、前輪駆動力算出部３１ではエンジントルク及び前後輪４，１４間の駆動力分配に基づき前輪４が発生している駆動力ＦＸが算出され、前輪横力算出部３２では横加速度センサ２６により検出された横加速度ＧＹと予め判明している前輪分担質量ＭＦとから次式(1)に従って前輪４が発生している横力ＦＣＦが算出される。   Under the above viewpoint, the control amount of the electronic control coupling 8 at the time of understeer is set according to FIG. First, the front wheel driving force calculation unit 31 calculates the driving force FX generated by the front wheels 4 based on the engine torque and the driving force distribution between the front and rear wheels 4 and 14, and the front wheel lateral force calculation unit 32 calculates the driving force FX. A lateral force FCF generated by the front wheels 4 is calculated according to the following equation (1) from the detected lateral acceleration GY and the previously determined front wheel shared mass MF.

ＦＣＦ＝ＭＦ×｜ＧＹ｜………(1)
前輪駆動力算出部３１からの前輪駆動力ＦＸと前輪横力算出部３２からの前輪横力ＦＣＦは前輪摩擦円算出部３３に入力され、これらの情報に基づき前輪摩擦円算出部３３では次式(2)に従って前輪摩擦円ＦＦＲが当該摩擦円ＦＦＲの半径として算出される（グリップ限界指標推定手段）。 FCF = MF × | GY | ... (1)
The front wheel driving force FX from the front wheel driving force calculation unit 31 and the front wheel lateral force FCF from the front wheel lateral force calculation unit 32 are input to the front wheel friction circle calculation unit 33. Based on these information, the front wheel friction circle calculation unit 33 calculates the following equation: According to (2), the front wheel friction circle FFR is calculated as the radius of the friction circle FFR (grip limit index estimation means).

ＦＦＲ＝√（ＦＸ２＋ＦＣＦ２）………(2)
前輪４が発揮するグリップ力は、タイヤの磨耗状態の相違、天候（晴天や降雪）や路面形態（舗装路やダート）に応じた路面摩擦係数の相違などの種々の要因に影響されるが、前輪４がグリップ限界に達してアンダステアを生じたときの駆動力ＦＸ及び横力ＦＣＦから摩擦円ＦＦＲが推定されるため、推定された摩擦円ＦＦＲは前輪４のグリップ力と正確に相関する大きさとなる。 FFR = √ (FX 2 + FCF 2 ) (2)
The grip force exerted by the front wheels 4 is influenced by various factors such as the difference in tire wear, the difference in road surface friction coefficient according to the weather (clear weather and snowfall) and the road surface form (paved road and dirt), Since the friction circle FFR is estimated from the driving force FX and the lateral force FCF when the front wheel 4 reaches the grip limit and causes understeer, the estimated friction circle FFR has a magnitude that accurately correlates with the grip force of the front wheel 4. Become.

ヨーモーメント算出部３４では、操舵角センサ２２からの操舵角θstr及び車速センサ２３からの車速Ｖに基づいて目標ヨーレイトＹＴが算出され（目標旋回状態指標決定手段）、目標ヨーレイトＹＴとヨーレイトセンサ２４により検出された実ヨーレイトＹＲとの偏差ΔＹに基づきアンダステアを抑制するために必要な要求ヨーモーメントＹＡＷＭが算出される。要求ヨーモーメントＹＡＷＭは前輪要求横力算出部３５に入力され、前輪要求横力算出部３５では次式(3)に従って要求ヨーモーメントＹＡＷＭを達成するために必要な前輪４の要求横力ＦＣＦＴが算出される（要求横力算出手段）。   The yaw moment calculation unit 34 calculates a target yaw rate YT based on the steering angle θstr from the steering angle sensor 22 and the vehicle speed V from the vehicle speed sensor 23 (target turning state index determination means), and the target yaw rate YT and the yaw rate sensor 24 Based on the detected deviation ΔY from the actual yaw rate YR, a required yaw moment YAWM required to suppress understeer is calculated. The required yaw moment YAWM is input to the front wheel required lateral force calculation unit 35, and the front wheel required lateral force calculation unit 35 calculates the required lateral force FCFT of the front wheel 4 necessary to achieve the required yaw moment YAWM according to the following equation (3). (Required lateral force calculation means).

ＦＣＦＴ＝ＹＡＷＭ/ＬＦ………(3)
ここに、ＬＦは重心から前軸までの距離である。
前輪摩擦円算出部３３からの前輪摩擦円ＦＦＲ、前輪横力算出部３２からの前輪横力ＦＣＦ、前輪要求横力算出部３５からの前輪要求横力ＦＣＦＴは前輪駆動力低下量算出部３６に入力され、当該前輪駆動力低下量算出部３６では、前輪摩擦円ＦＦＲを前提として要求横力ＦＣＦＴ相当分だけ前輪４の横力ＦＣＦを増加させるために必要な前輪４の駆動力低下量ＦＸＴが次式(4)に従って算出される（駆動力低下量算出手段）。 FCFT = YAWM / LF (3)
Here, LF is the distance from the center of gravity to the front axis.
The front wheel friction circle FFR from the front wheel friction circle calculation unit 33, the front wheel lateral force FCF from the front wheel lateral force calculation unit 32, and the front wheel requested lateral force FCFT from the front wheel requested lateral force calculation unit 35 are supplied to the front wheel driving force decrease amount calculation unit 36. The front wheel driving force reduction amount calculation unit 36 receives the front wheel 4 driving force reduction amount FXT necessary to increase the lateral force FCF of the front wheel 4 by an amount corresponding to the required lateral force FCFT on the assumption of the front wheel friction circle FFR. It is calculated according to the following equation (4) (driving force reduction amount calculating means).

ＦＸＴ＝｜ＦＸ｜−√（ＦＦＲ２−（ＦＣＦ＋ＦＣＦＴ）２）………(4)
算出された前輪４の駆動力低下量ＦＸＴは制御量算出部３７に入力され、制御量算出部３７では駆動力低下量ＦＸＴに対応する駆動力分配に対する補正量としてヨーレイト対応制御量Ｔy（旋回対応制御量）が次式(5)に従って算出される（制御量算出手段）。
Ｔy＝ＦＸＴ×Ｒ/ＦＨＧ………(5)
ここに、Ｒは前輪４のタイヤ半径、ＦＨＧはリングギヤ２とピニオンギヤ７のギア比である。 FXT = | FX | −√ (FFR 2 − (FCF + FCFT) 2 ) (4)
The calculated driving force decrease amount FXT of the front wheel 4 is input to the control amount calculation unit 37, and the control amount calculation unit 37 uses the yaw rate corresponding control amount Ty (turning correspondence) as a correction amount for the driving force distribution corresponding to the driving force decrease amount FXT. Control amount) is calculated according to the following equation (5) (control amount calculation means).
Ty = FXT × R / FHG ……… (5)
Here, R is a tire radius of the front wheel 4 and FHG is a gear ratio of the ring gear 2 and the pinion gear 7.

一方、ベース制御量算出部３８では、ヨーレイト対応制御量Ｔy以外のベース制御量Ｔbaseが算出される。例えば車両旋回時には前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveとの差に基づいて差回転対応制御量が算出され、アクセル操作に伴う車両加速時にはアクセル操作量などに基づいて初期スリップを抑制するための加速対応制御量が算出され、ブレーキ操作に伴う車両減速時には車両減速度などに基づいて車両姿勢を安定化するための減速対応制御量が算出され、これらの制御量を加算した総和がベース制御量Ｔbaseとして設定される。また、車輪速判定部３９では車輪速ＮFR,ＮFL,ＮRR,ＮRから前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveとが算出され、これらの前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveの大小関係が判定される。   On the other hand, the base control amount calculation unit 38 calculates a base control amount Tbase other than the yaw rate corresponding control amount Ty. For example, a differential rotation control amount is calculated based on the difference between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave when the vehicle is turning, and the initial slip is suppressed based on the accelerator operation amount during acceleration of the vehicle accompanying the accelerator operation. The acceleration-related control amount is calculated, and when the vehicle decelerates due to the braking operation, the deceleration-related control amount for stabilizing the vehicle posture is calculated based on the vehicle deceleration, etc., and the sum total of these control amounts is the base Set as control amount Tbase. The wheel speed determination unit 39 calculates the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave from the wheel speeds NFR, NFL, NRR, and NR, and the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave are calculated. A magnitude relationship is determined.

以上の制御量算出部３７からのヨーレイト対応制御量Ｔy、ベース制御量算出部３８からのベース制御量Ｔbase、車輪速判定部３９からの前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveとの大小関係は最終制御量算出部４０に入力され、最終制御量算出部４０ではこれらの情報に基づき図２中に示す条件に従って最終制御量Ｔが算出される。そして、このようにして設定された最終制御量Ｔに基づいて前後輪４，１４間の実際の駆動力分配が制御される。即ち、最終制御量Ｔに対応するデューティ率が図示しないマップから設定され、そのデューティ率に基づく電子制御カップリング８の電磁クラッチの励磁により係合状態が調整され、その結果、前後輪４，１４間の駆動力分配が上記最終制御量Ｔに対応する値に調整される（駆動力分配制御手段）。   The magnitude of the yaw rate corresponding control amount Ty from the control amount calculation unit 37, the base control amount Tbase from the base control amount calculation unit 38, and the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave from the wheel speed determination unit 39. The relationship is input to the final control amount calculation unit 40, and the final control amount calculation unit 40 calculates the final control amount T according to the conditions shown in FIG. The actual driving force distribution between the front and rear wheels 4 and 14 is controlled based on the final control amount T set in this way. That is, the duty ratio corresponding to the final control amount T is set from a map (not shown), and the engagement state is adjusted by the excitation of the electromagnetic clutch of the electronic control coupling 8 based on the duty ratio. The driving force distribution is adjusted to a value corresponding to the final control amount T (driving force distribution control means).

前後輪４，１４間の駆動力分配によるトルク移動は車輪速の高い側から低い側へと行われるため、図３に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い走行状況（ＮFave＞ＮRave）では電子制御カップリング８を介して前輪４から後輪１４へとトルクが移動している。即ち、前輪４の駆動力の一部が後輪１４に分配されることにより、トルク移動相当分だけ後輪１４が駆動力を発生すると共に前輪４の駆動力が低下している。図２に示すように最終制御量算出部４０では最終制御量Ｔがヨーレイト対応制御量Ｔyだけ増加補正されるため、最終制御量Ｔの増加に応じて実際の前後輪４，１４間の駆動力分配も増加する。結果として前輪４から後輪１４へのトルク移動量が増加し、図３に白抜き矢印Ａdrv，Ａcorneringで示すように後輪１４の駆動力が増加する一方、前輪４の駆動力が低下する。このときの前輪４の駆動力は上記前輪駆動力低下量算出部３６で算出された駆動力低下量ＦＸＴ相当分だけ低下し、それに応じて前輪要求横力算出部３５で算出された要求横力ＦＣＦＴ相当分だけ前輪４の横力が増加し、前輪４の横力増加に伴ってヨーモーメント算出部３４で算出された要求ヨーモーメントＹＡＷＭ相当分だけ車両のヨーモーメントが増加し、車両に発生しているアンダステアが抑制される。   Since the torque movement by the driving force distribution between the front and rear wheels 4 and 14 is performed from the high wheel speed side to the low wheel speed side, the front wheel average wheel speed NFave shown in FIG. 3 is higher than the rear wheel average wheel speed NRave (NFave). > N Rave), the torque moves from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8. That is, a part of the driving force of the front wheel 4 is distributed to the rear wheel 14, so that the rear wheel 14 generates a driving force corresponding to the torque movement and the driving force of the front wheel 4 is reduced. As shown in FIG. 2, in the final control amount calculation unit 40, the final control amount T is corrected to increase by the yaw rate corresponding control amount Ty, so that the actual driving force between the front and rear wheels 4 and 14 as the final control amount T increases. Distribution also increases. As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 increases, and the driving force of the rear wheel 14 increases while the driving force of the front wheel 4 decreases as shown by the white arrows Adrv and Acornering in FIG. The driving force of the front wheels 4 at this time decreases by the amount corresponding to the driving force decrease amount FXT calculated by the front wheel driving force decrease amount calculation unit 36, and the required lateral force calculated by the front wheel required lateral force calculation unit 35 accordingly. The lateral force of the front wheel 4 increases by the amount corresponding to FCFT, and the yaw moment of the vehicle increases by the amount corresponding to the requested yaw moment YAWM calculated by the yaw moment calculation unit 34 with the increase of the lateral force of the front wheel 4 and is generated in the vehicle. Understeer is suppressed.

また、図４に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い走行状況（ＮFave＜ＮRave）では電子制御カップリング８を介して後輪１４から前輪４へとトルクが移動している。即ち、前輪４が後輪１４側から逆駆動されると共に、トルク移動相当分だけ後輪１４が制動力（負の駆動力）を発生すると共に前輪４の駆動力が増加している。図２に示すように最終制御量算出部４０では最終制御量Ｔがヨーレイト対応制御量Ｔyだけ減少補正されるため、最終制御量Ｔの低下に応じて実際の前後輪４，１４間の駆動力分配も低下する。結果として後輪１４から前輪４へのトルク移動量が低下し、図４に白抜き矢印Ａdrv，Ａcorneringで示すように後輪１４の制動力が低下する一方、前輪４の駆動力が低下する。従って、上記と同様に前輪４の駆動力の低下に伴って横力が増加し、ヨーモーメントの増加に応じてアンダステアが抑制される。   Further, in the traveling state where the average front wheel speed NFave shown in FIG. 4 is lower than the average rear wheel speed NRave (NFave <NRave), the torque is moved from the rear wheel 14 to the front wheel 4 via the electronic control coupling 8. . That is, the front wheel 4 is reversely driven from the rear wheel 14 side, the rear wheel 14 generates a braking force (negative driving force) corresponding to the torque movement, and the driving force of the front wheel 4 is increased. As shown in FIG. 2, in the final control amount calculation unit 40, the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty, so that the actual driving force between the front and rear wheels 4 and 14 as the final control amount T decreases. Distribution also declines. As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 decreases, and the braking force of the rear wheel 14 decreases as shown by the white arrows Adrv and Acornering in FIG. 4, while the driving force of the front wheel 4 decreases. Accordingly, as described above, the lateral force increases as the driving force of the front wheels 4 decreases, and understeer is suppressed as the yaw moment increases.

なお、図２では示されていないが、車両が旋回中でないとき及び旋回中であってもステア特性がニュートラルステアのときには最終制御量Ｔの算出にヨーレイト制御量Ｔyは反映されず、ベース制御量Ｔbaseがそのまま最終制御量Ｔとして設定されるため、上記のようなアンダステアの抑制のための駆動力分配の制御は実行されない。
一方、旋回中の車両にオーバステアが発生した場合について述べる。図５はオーバステア発生時にＥＣＵ２１により実行される電子制御カップリング８の制御量の設定手順を示すブロック図、図６，７は設定された制御量に基づく駆動力分配の制御状況を示す模式図であり、図６は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い場合を示し、図７は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い場合を示している。 Although not shown in FIG. 2, the yaw rate control amount Ty is not reflected in the calculation of the final control amount T when the steering characteristic is neutral steer even when the vehicle is not turning or is turning, and the base control amount is not reflected. Since Tbase is set as the final control amount T as it is, the driving force distribution control for suppressing the understeer as described above is not executed.
On the other hand, a case where oversteer occurs in a turning vehicle will be described. FIG. 5 is a block diagram showing the procedure for setting the control amount of the electronic control coupling 8 executed by the ECU 21 when oversteer occurs, and FIGS. 6 and 7 are schematic views showing the control state of the driving force distribution based on the set control amount. FIG. 6 shows a case where the front wheel average wheel speed NFave is higher than the rear wheel average wheel speed NRave, and FIG. 7 shows a case where the front wheel average wheel speed NFave is lower than the rear wheel average wheel speed NRave.

車両のオーバステアは後輪１４の横力不足によるスリップに起因する現象であり、このときの後輪１４は自己の摩擦円により規定される駆動力及び横力に対するグリップを限界まで使用しているものと推測でき、換言すれば、後輪１４の駆動力の低下により横力を増加させてオーバステアを抑制できる余地があると解釈できる。一方、後輪１４の駆動力は、電子制御カップリング８を介して前輪４から後輪１４に分配されるトルク、或いは後輪１４から前輪に伝達されるトルクに応じて変化するため、前後輪４，１４間の駆動力分配に応じて調整可能である。   Oversteering of the vehicle is a phenomenon caused by slip due to insufficient lateral force of the rear wheel 14. At this time, the rear wheel 14 uses the driving force and the grip against the lateral force defined by its own friction circle to the limit. In other words, it can be interpreted that there is room for suppressing the oversteer by increasing the lateral force due to the decrease in the driving force of the rear wheel 14. On the other hand, the driving force of the rear wheel 14 changes according to the torque distributed from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8 or the torque transmitted from the rear wheel 14 to the front wheel. 4 and 14 can be adjusted according to the driving force distribution.

以上の観点の下に図５に従ってオーバステア時の電子制御カップリング８の制御量が設定される。まず、後輪駆動力算出部３１'では前後輪４，１４間の駆動力分配に基づき後輪１４が発生している駆動力ＲＸが算出され、後輪横力算出部３２'では横加速度センサ２６により検出された横加速度ＧＹと予め判明している後輪分担質量ＭＲとから次式(6)に従って後輪１４が発生している横力ＲＣＦが算出される。   Under the above viewpoint, the control amount of the electronic control coupling 8 during oversteering is set according to FIG. First, the rear wheel driving force calculation unit 31 ′ calculates the driving force RX generated by the rear wheel 14 based on the driving force distribution between the front and rear wheels 4 and 14, and the rear wheel lateral force calculation unit 32 ′ calculates the lateral acceleration sensor. A lateral force RCF generated by the rear wheel 14 is calculated according to the following equation (6) from the lateral acceleration GY detected by the vehicle 26 and the rear wheel shared mass MR that is known in advance.

ＲＣＦ＝ＭＲ×｜ＧＹ｜………(6)
後輪駆動力算出部３１'からの後輪駆動力ＲＸと後輪横力算出部３２'からの後輪横力ＲＣＦは後輪摩擦円算出部３３'に入力され、これらの情報に基づき後輪摩擦円算出部３３'では次式(7)に従って後輪摩擦円ＲＦＲが当該摩擦円ＲＦＲの半径として算出される（グリップ限界指標推定手段）。 RCF = MR × | GY |… (6)
The rear wheel driving force RX from the rear wheel driving force calculating unit 31 ′ and the rear wheel lateral force RCF from the rear wheel lateral force calculating unit 32 ′ are input to the rear wheel friction circle calculating unit 33 ′, and based on these information, the rear wheel driving force RX In the wheel friction circle calculation unit 33 ′, the rear wheel friction circle RFR is calculated as the radius of the friction circle RFR according to the following equation (7) (grip limit index estimation means).

ＲＦＲ＝√（ＲＸ２＋ＲＣＦ２）………(7)
前輪４と同じく後輪１４についても、グリップ限界に達してオーバステアを生じたときの駆動力ＲＸ及び横力ＲＣＦから摩擦円ＲＦＲが推定されるため、推定された摩擦円ＲＦＲは後輪１４のグリップ力と正確に相関する大きさとなる。
ヨーモーメント算出部３４'では、上記アンダステア時と同様の手順に従ってオーバステアを抑制するために必要な要求ヨーモーメントＹＡＷＭが算出され、この要求ヨーモーメントＹＡＷＭに基づき後輪要求横力算出部３５'では次式(8)に従って要求ヨーモーメントＹＡＷＭを達成するために必要な後輪１４の要求横力ＲＣＦＴが算出される（要求横力算出手段）。 RFR = √ (RX 2 + RCF 2 ) (7)
As with the front wheel 4, the friction circle RFR is also estimated for the rear wheel 14 from the driving force RX and lateral force RCF when the grip limit is reached and oversteer occurs, so the estimated friction circle RFR is the grip of the rear wheel 14. The magnitude correlates accurately with force.
The yaw moment calculation unit 34 ′ calculates a required yaw moment YAWM necessary for suppressing oversteer according to the same procedure as that for the understeer, and the rear wheel required lateral force calculation unit 35 ′ calculates the next required yaw moment YAWM. The required lateral force RCFT of the rear wheel 14 necessary for achieving the required yaw moment YAWM is calculated according to the equation (8) (required lateral force calculating means).

ＲＣＦＴ＝ＹＡＷＭ/ＬＲ………(8)
ここに、ＬＲは重心から後軸までの距離である。
後輪摩擦円算出部３３'からの後輪摩擦円ＲＦＲ、後輪横力算出部３２'からの後輪横力ＲＣＦ、後輪要求横力算出部３５'からの後輪要求横力ＲＣＦＴは後輪駆動力低下量算出部３６'に入力され、当該後輪駆動力低下量算出部３６'では、後輪摩擦円ＲＦＲを前提として要求横力ＲＣＦＴ相当分だけ後輪１４の横力ＲＣＦを増加させるために必要な後輪１４の駆動力低下量ＲＸＴが次式(9)に従って算出される（駆動力低下量算出手段）。 RCFT = YAWM / LR (8)
Here, LR is the distance from the center of gravity to the rear axis.
The rear wheel friction circle RFR from the rear wheel friction circle calculation unit 33 ′, the rear wheel lateral force RCF from the rear wheel lateral force calculation unit 32 ′, and the rear wheel requested lateral force RCFT from the rear wheel requested lateral force calculation unit 35 ′ are The rear wheel driving force decrease amount calculating unit 36 ′ inputs the rear wheel driving force decrease amount calculating unit 36 ′ to calculate the lateral force RCF of the rear wheel 14 corresponding to the required lateral force RCFT on the premise of the rear wheel friction circle RFR. The driving force reduction amount RXT of the rear wheel 14 necessary for the increase is calculated according to the following equation (9) (driving force reduction amount calculating means).

ＲＸＴ＝｜ＲＸ｜−√（ＲＦＲ２−（ＲＣＦ＋ＲＣＦＴ）２）………(9)
算出された後輪１４の駆動力低下量ＲＸＴは制御量算出部３７'に入力され、制御量算出部３７'では駆動力低下量ＲＸＴに対応する駆動力分配に応じた補正量としてヨーレイト対応制御量Ｔy（旋回対応制御量）が次式(10)に従って算出される（制御量算出手段）。 RXT = | RX | −√ (RFR 2 − (RCF + RCFT) 2 ) (9)
The calculated driving force reduction amount RXT of the rear wheel 14 is input to the control amount calculation unit 37 ′, and the control amount calculation unit 37 ′ controls the yaw rate as a correction amount corresponding to the driving force distribution corresponding to the driving force reduction amount RXT. An amount Ty (a turning control amount) is calculated according to the following equation (10) (control amount calculation means).

Ｔy＝ＲＸＴ×Ｒ/ＲＨＧ………(10)
ここに、ＲＨＧはリングギヤ１２とピニオンギヤ１０のギア比である。
一方、ベース制御量算出部３８'及び車輪速判定部３９'の処理は上記アンダステア時と同様であり、ベース制御量算出部３８'ではベース制御量Ｔbaseが算出され、車輪速判定部３９'では前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveとの大小関係が判定される。 Ty = RXT × R / RHG (10)
Here, RHG is a gear ratio between the ring gear 12 and the pinion gear 10.
On the other hand, the processing of the base control amount calculation unit 38 ′ and the wheel speed determination unit 39 ′ is the same as that during the understeer, the base control amount calculation unit 38 ′ calculates the base control amount Tbase, and the wheel speed determination unit 39 ′ The magnitude relationship between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave is determined.

以上の情報に基づき最終制御量算出部４０'では図５中に示す条件に従って最終制御量Ｔが算出され、この最終制御量Ｔに基づいて電子制御カップリング８により前後輪４，１４間の駆動力分配が調整される（駆動力分配制御手段）。
図６に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い走行状況（ＮFave＞ＮRave）では、図３と同じく電子制御カップリング８を介して前輪４から後輪１４へとトルクが移動している。即ち、前輪４の駆動力の一部が後輪１４に分配されることにより、トルク移動相当分だけ後輪１４が駆動力を発生すると共に前輪４の駆動力が低下している。図５に示すように最終制御量算出部４０'では最終制御量Ｔがヨーレイト対応制御量Ｔyだけ減少補正されるため、最終制御量Ｔの低下に応じて実際の前後輪４，１４間の駆動力分配も低下する。結果として前輪４から後輪１４へのトルク移動量が低下し、図６に白抜き矢印Ａdrv，Ａcorneringで示すように後輪１４の駆動力が低下する一方、前輪４の駆動力が増加する。このときの後輪１４の駆動力は上記後輪駆動力低下量算出部３６'で算出された駆動力低下量ＲＸＴ相当分だけ低下し、それに応じて後輪要求横力算出部３５'で算出された要求横力ＲＣＦＴ相当分だけ後輪１４の横力が増加し、後輪１４の横力増加に伴ってヨーモーメント算出部３４'で算出された要求ヨーモーメントＹＡＷＭ相当分だけ車両のヨーモーメントが低下し、車両に発生しているオーバステアが抑制される。 Based on the above information, the final control amount calculation unit 40 ′ calculates the final control amount T according to the conditions shown in FIG. 5, and the electronic control coupling 8 drives the front and rear wheels 4 and 14 based on the final control amount T. The force distribution is adjusted (driving force distribution control means).
In the driving situation (NFave> NRave) where the average front wheel speed NFave is higher than the average rear wheel speed NRave shown in FIG. 6, the torque moves from the front wheel 4 to the rear wheel 14 via the electronically controlled coupling 8 as in FIG. is doing. That is, a part of the driving force of the front wheel 4 is distributed to the rear wheel 14, so that the rear wheel 14 generates a driving force corresponding to the torque movement and the driving force of the front wheel 4 is reduced. As shown in FIG. 5, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty in the final control amount calculation unit 40 ′, the actual driving between the front and rear wheels 4 and 14 according to the decrease in the final control amount T. Power distribution also decreases. As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 is reduced, and the driving force of the rear wheel 14 is reduced while the driving force of the front wheel 4 is increased, as indicated by white arrows Adrv and Acornering in FIG. At this time, the driving force of the rear wheel 14 is reduced by an amount corresponding to the driving force reduction amount RXT calculated by the rear wheel driving force reduction amount calculation unit 36 ′, and is calculated by the rear wheel required lateral force calculation unit 35 ′ accordingly. The lateral force of the rear wheel 14 is increased by the amount corresponding to the requested lateral force RCFT, and the yaw moment of the vehicle is increased by the amount corresponding to the requested yaw moment YAWM calculated by the yaw moment calculating unit 34 ′ as the lateral force of the rear wheel 14 increases. And the oversteer occurring in the vehicle is suppressed.

また、図７に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い走行状況（ＮFave＜ＮRave）では、図４と同じく電子制御カップリング８を介して後輪１４から前輪４へとトルクが移動している。即ち、前輪４が後輪１４側から逆駆動されると共に、トルク移動相当分だけ後輪１４が制動力を発生している。図５に示すように最終制御量算出部４０'では最終制御量Ｔがヨーレイト対応制御量Ｔyだけ減少補正されるため、最終制御量Ｔの低下に応じて実際の前後輪４，１４間の駆動力分配も低下する。結果として後輪１４から前輪４へのトルク移動量が低下し、図７に白抜き矢印Ａdrv，Ａcorneringで示すように後輪１４の制動力が低下する一方、前輪４の駆動力が低下する。従って、上記と同様に後輪１４の駆動力の低下に伴って横力が増加し、ヨーモーメントの増加に応じてオーバステアが抑制される。   Further, in a traveling state where the average front wheel speed NFave shown in FIG. 7 is lower than the average rear wheel speed NRave (NFave <NRave), the torque from the rear wheel 14 to the front wheel 4 via the electronically controlled coupling 8 is the same as in FIG. Is moving. That is, the front wheel 4 is reversely driven from the rear wheel 14 side, and the rear wheel 14 generates a braking force corresponding to the torque movement. As shown in FIG. 5, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty in the final control amount calculation unit 40 ′, the actual driving between the front and rear wheels 4 and 14 according to the decrease in the final control amount T. Power distribution also decreases. As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 decreases, and the braking force of the rear wheel 14 decreases as shown by the white arrows Adrv and Acornering in FIG. 7, while the driving force of the front wheel 4 decreases. Accordingly, as described above, the lateral force increases as the driving force of the rear wheel 14 decreases, and oversteer is suppressed as the yaw moment increases.

以上のように本実施形態の車両の駆動力分配制御装置では、車両の旋回中において前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveとの大小関係のみならず車両のステア特性も反映して統合的に前後輪４，１４間の駆動力分配を制御している。車両のステア特性は車両のヨーモーメントを何れの方向に修正すべきかを表し、前輪平均車輪速ＮFaveと後輪平均車輪速ＮRaveとの大小関係は前後輪４，１４間のトルク移動方向、ひいては駆動力分配の増減によるヨーモーメントの変化方向を表すため、双方の条件の組み合わせに基づき車両の旋回状態に対して最適な前後輪４，１４間の駆動力分配を設定できる。よって、前後輪４，１４間の駆動力分配を適切に制御してアンダステアやオーバステアを確実に抑制でき、もって車両の旋回状態に関わらず常に良好なステア特性を実現することができる。   As described above, in the vehicle driving force distribution control apparatus according to the present embodiment, the vehicle steer characteristics are integrated in addition to the magnitude relationship between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave during the turning of the vehicle. Therefore, the driving force distribution between the front and rear wheels 4 and 14 is controlled. The steer characteristic of the vehicle indicates in which direction the yaw moment of the vehicle should be corrected, and the magnitude relationship between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave is the direction of torque movement between the front and rear wheels 4 and 14, and hence the drive Since the change direction of the yaw moment due to the increase / decrease of the force distribution is expressed, the optimum driving force distribution between the front and rear wheels 4 and 14 can be set for the turning state of the vehicle based on the combination of both conditions. Therefore, understeering and oversteering can be reliably suppressed by appropriately controlling the driving force distribution between the front and rear wheels 4, 14, so that a good steering characteristic can always be realized regardless of the turning state of the vehicle.

また、本実施形態では、具体的な目標ヨーレイトＹＴと実ヨーレイトＹＲに基づいて車両のステア特性を判定した上で、このステア特性に基づいてグリップ限界を越えたスリップ輪が前後輪４，１４の何れであるかを特定し、スリップ輪の駆動力ＦＸ，ＲＸ及び横力ＦＣＦ，ＲＣＦから推定した摩擦円ＦＦＲ，ＲＦＲを前提とし、アンダステアやオーバステアを抑制するための要求ヨーモーメントＹＡＷＭ、要求ヨーモーメントＹＡＷＭを達成可能なスリップ輪の要求横力ＦＣＦＴ，ＲＣＦＴ、要求横力ＦＣＦＴ，ＲＣＦＴを達成するためのスリップ輪の駆動力低下量ＦＸＴ，ＲＸＴなどの具体的な算出値に基づいてヨーレイト対応制御量Ｔyを算出している。従って、例えば過去の経験則や実験結果に基づいてヨーレイト対応制御量Ｔyを設定する場合などに比較して、より現実に即したヨーレイト対応制御量Ｔyを算出でき、もって、一層適切に前後輪４，１４間の駆動力分配を制御することができる。   Further, in this embodiment, after determining the vehicle steer characteristic based on the specific target yaw rate YT and the actual yaw rate YR, the slip wheels exceeding the grip limit based on the steer characteristic are the front and rear wheels 4, 14. Based on the friction circles FFR and RFR estimated from the slip wheel driving forces FX and RX and the lateral forces FCF and RCF, the required yaw moment YAWM and the required yaw moment for suppressing understeer and oversteer are specified. Yaw rate control amount based on specific calculated values such as slip wheel driving force reduction amounts FXT, RXT for achieving the required lateral force FCFT, RCFT of the slip wheel that can achieve YAWM, and the required lateral force FCFT, RCFT Ty is calculated. Therefore, compared with the case where the yaw rate corresponding control amount Ty is set based on, for example, past empirical rules and experimental results, the yaw rate corresponding control amount Ty more realistic can be calculated, and thus the front and rear wheels 4 can be more appropriately calculated. , 14 can be controlled.

しかも、駆動力ＦＸ，ＲＸ及び横力ＦＣＦ，ＲＣＦに基づいてスリップ輪のグリップ力と正確に相関する摩擦円ＦＦＲ，ＲＦＲが推定されるため、例えばタイヤの磨耗状態の相違、天候（晴天や降雪）や路面形態（舗装路やダート）に応じた路面摩擦係数の相違などに影響されることなく適切なヨーレイト対応制御量Ｔyを算出できる。換言すれば、これらの外乱要因による影響を排除すべくタイヤ磨耗状態や路面摩擦係数をセンサにより検出して補償処理を実行する必要がなくなるという利点もある。   In addition, since the friction circles FFR and RFR that accurately correlate with the grip force of the slip wheel are estimated based on the driving forces FX and RX and the lateral forces FCF and RCF, for example, a difference in tire wear state, weather (clear weather or snowfall) ) And the road surface form (paved road or dirt), the appropriate yaw rate control amount Ty can be calculated without being affected by the difference in the road surface friction coefficient. In other words, there is an advantage that it is not necessary to detect the tire wear state and the road surface friction coefficient by the sensor and to perform the compensation process in order to eliminate the influence of these disturbance factors.

一方、車両のステア特性の判定処理やヨーモーメント算出部３４，３４'での要求ヨーモーメントＹＡＷＭの算出処理には実ヨーレイトＹＲ及び目標ヨーレイトＹＴが適用されるが、これらのヨーレイトＹＲ,ＹＴは車両の旋回状態を端的に表す指標と見なせる。よって、これらのヨーレイトＹＲ,ＹＴに基づいてステア特性の判定や要求ヨーモーメントＹＡＷＭの算出を適確に実行でき、ひいては前後輪４，１４間の駆動力分配を一層適切に制御することができる。
[第２実施形態]
次に、本発明をＦＲ車ベースの電子制御式オンディマンド４輪駆動車の前後輪４，１４間の駆動力分配を制御する駆動力分配制御装置に具体化した第２実施形態を説明する。 On the other hand, the actual yaw rate YR and the target yaw rate YT are applied to the determination process of the vehicle steering characteristic and the calculation process of the required yaw moment YAWM in the yaw moment calculation units 34 and 34 '. These yaw rates YR and YT are applied to the vehicle. It can be regarded as an index that directly represents the turning state of. Therefore, the determination of the steering characteristic and the calculation of the required yaw moment YAWM can be accurately executed based on these yaw rates YR and YT, and the driving force distribution between the front and rear wheels 4 and 14 can be further appropriately controlled.
[Second Embodiment]
Next, a second embodiment in which the present invention is embodied in a driving force distribution control device that controls the driving force distribution between the front and rear wheels 4 and 14 of the FR vehicle-based electronically controlled on-demand four-wheel drive vehicle will be described.

本実施形態で行われる前後輪４，１４間の駆動力分配の制御は、第１実施形態の制御と同様の着想の下に実行されるものであり、第１実施形態のＦＦ車ベースの４輪駆動車に対して前後輪４，１４間のトルク移動が逆方向になることを考慮して、図２，５に示す最終制御量算出部４０，４０'でのヨーレイト対応制御量Ｔyに基づく補正方向を変更した点が相違する。従って、共通の構成及び処理内容の箇所は重複する説明を省略し、相違点を重点的に説明する。   The control of the driving force distribution between the front and rear wheels 4 and 14 performed in the present embodiment is executed under the same idea as the control in the first embodiment, and is based on the FF vehicle base 4 in the first embodiment. Considering that the torque movement between the front and rear wheels 4 and 14 is in the opposite direction with respect to the wheel drive vehicle, based on the yaw rate corresponding control amount Ty in the final control amount calculation units 40 and 40 ′ shown in FIGS. The difference is that the correction direction is changed. Therefore, the description which overlaps a common structure and the location of a processing content is abbreviate | omitted, and demonstrates a different point mainly.

図８，９はアンダステア発生時における駆動力分配の制御状況を示す模式図であり、図８は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い場合を示し、図９は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い場合を示し、まず、これらの図に従ってアンダステア発生時の駆動力分配の制御状況を説明する。
ＦＲ車ベースの電子制御式オンディマンド４輪駆動車ではエンジンからの駆動力が後輪１４に伝達され、後輪１４の駆動力の一部が前後輪４，１４間に設けられた電子制御カップリング８を介して前輪４側に分配され、電子制御カップリング８の電磁クラッチの係合状態に応じて後輪１４側から前輪４側に分配される駆動力、即ち、前後輪４，１４間の駆動力分配を調整する。 8 and 9 are schematic views showing the control state of driving force distribution when understeer occurs. FIG. 8 shows the case where the average front wheel speed NFave is higher than the average rear wheel speed NRave, and FIG. 9 shows the average front wheel speed. A case where NFave is lower than the rear wheel average wheel speed NRave will be described. First, a control state of driving force distribution when understeer occurs will be described with reference to these drawings.
In an FR vehicle-based electronically controlled on-demand four-wheel drive vehicle, the driving force from the engine is transmitted to the rear wheel 14, and a part of the driving force of the rear wheel 14 is provided between the front and rear wheels 4, 14. 8, the driving force distributed to the front wheel 4 side from the rear wheel 14 side to the front wheel 4 side according to the engagement state of the electromagnetic clutch of the electronic control coupling 8, that is, between the front and rear wheels 4 and 14 Adjust the driving force distribution.

前後輪４，１４間の駆動力分配によるトルク移動は車輪速の高い側から低い側へと行われるため、図８に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い走行状況（ＮFave＞ＮRave）では電子制御カップリング８を介して前輪４から後輪１４へとトルクが移動している。即ち、後輪１４が前輪４側から逆駆動されると共に、トルク移動相当分だけ前輪４が制動力（負の駆動力）を発生すると共に後輪１４の駆動力が増加している。このときには最終制御量Ｔがヨーレイト対応制御量Ｔyだけ減少補正されるため（Ｔ＝Ｔbase−Ｔy）、最終制御量Ｔの低下に応じて実際の前後輪４，１４間の駆動力分配も低下する。結果として前輪４から後輪１４へのトルク移動量が低下し、図８に白抜き矢印Ａdrv，Ａcorneringで示すように前輪４の制動力が低下する一方、後輪１４の駆動力が低下する。従って、前輪４の駆動力の低下に伴って横力が増加し、ヨーモーメントの増加に応じてアンダステアが抑制される。   Since the torque movement by the driving force distribution between the front and rear wheels 4 and 14 is performed from the high wheel speed side to the low wheel speed side, the front wheel average wheel speed NFave shown in FIG. 8 is higher than the rear wheel average wheel speed NRave (NFave). > N Rave), the torque moves from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8. That is, the rear wheel 14 is reversely driven from the front wheel 4 side, the front wheel 4 generates a braking force (negative driving force) corresponding to the torque movement, and the driving force of the rear wheel 14 increases. At this time, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty (T = Tbase−Ty), the actual driving force distribution between the front and rear wheels 4 and 14 decreases as the final control amount T decreases. . As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 decreases, and the braking force of the front wheel 4 decreases as shown by the white arrows Adrv and Acornering in FIG. 8, while the driving force of the rear wheel 14 decreases. Accordingly, the lateral force increases as the driving force of the front wheels 4 decreases, and understeer is suppressed as the yaw moment increases.

また、図９に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い走行状況（ＮFave＜ＮRave）では電子制御カップリング８を介して後輪１４から前輪４へとトルクが移動している。即ち、後輪１４の駆動力の一部が前輪４に分配されることにより、トルク移動相当分だけ前輪４が駆動力を発生すると共に後輪１４の駆動力が低下している。このときには最終制御量Ｔがヨーレイト対応制御量Ｔyだけ減少補正されるため（Ｔ＝Ｔbase−Ｔy）、最終制御量Ｔの低下に応じて実際の前後輪４，１４間の駆動力分配も低下する。結果として後輪１４から前輪４へのトルク移動量が低下し、図９に白抜き矢印Ａdrv，Ａcorneringで示すように後輪１４の駆動力が増加する一方、前輪４の駆動力が低下する。従って、前輪４の駆動力の低下に伴って横力が増加し、ヨーモーメントの増加に応じてアンダステアが抑制される。   Further, in the traveling state (NFave <NRave) where the average front wheel speed NFave shown in FIG. 9 is lower than the average average wheel speed NRave, the torque is moved from the rear wheel 14 to the front wheel 4 via the electronic control coupling 8. . That is, a part of the driving force of the rear wheel 14 is distributed to the front wheel 4, so that the front wheel 4 generates the driving force corresponding to the torque movement and the driving force of the rear wheel 14 is reduced. At this time, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty (T = Tbase−Ty), the actual driving force distribution between the front and rear wheels 4 and 14 decreases as the final control amount T decreases. . As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 decreases, and the driving force of the rear wheel 14 increases while the driving force of the front wheel 4 decreases as shown by the white arrows Adrv and Acornering in FIG. Accordingly, the lateral force increases as the driving force of the front wheels 4 decreases, and understeer is suppressed as the yaw moment increases.

一方、オーバステア発生時の駆動力分配の制御状況を説明すると、図１０，１１はオーバステア発生時における駆動力分配の制御状況を示す模式図であり、図１０は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い場合を示し、図１１は前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い場合を示している。
図１０に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより高い走行状況（ＮFave＞ＮRave）では、図８と同じく電子制御カップリング８を介して前輪４から後輪１４へとトルクが移動している。即ち、後輪１４が前輪４側から逆駆動されると共に、トルク移動相当分だけ前輪４が制動力を発生している。このときには最終制御量Ｔがヨーレイト対応制御量Ｔyだけ減少補正されるため（Ｔ＝Ｔbase−Ｔy）、最終制御量Ｔの低下に応じて実際の前後輪４，１４間の駆動力分配も低下する。結果として前輪４から後輪１４へのトルク移動量が低下し、図１０に白抜き矢印Ａdrv，Ａcorneringで示すように前輪４の制動力が低下する一方、後輪１４の駆動力が低下する。従って、後輪１４の駆動力の低下に伴って横力が増加し、ヨーモーメントの増加に応じてオーバステアが抑制される。 On the other hand, the control situation of the driving force distribution at the time of oversteer will be described. FIGS. 10 and 11 are schematic diagrams showing the control situation of the driving force distribution at the time of oversteer. FIG. 10 shows the average front wheel speed NFave as the average of the rear wheels. FIG. 11 shows a case where the front wheel average wheel speed NFave is lower than the rear wheel average wheel speed NRave.
In the driving situation (NFave> NRave) where the average front wheel speed NFave is higher than the average rear wheel speed NRave shown in FIG. 10, the torque moves from the front wheel 4 to the rear wheel 14 via the electronically controlled coupling 8 as in FIG. is doing. That is, the rear wheel 14 is reversely driven from the front wheel 4 side, and the front wheel 4 generates a braking force corresponding to the torque movement. At this time, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty (T = Tbase−Ty), the actual driving force distribution between the front and rear wheels 4 and 14 decreases as the final control amount T decreases. . As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 decreases, and the braking force of the front wheel 4 decreases while the driving force of the rear wheel 14 decreases as indicated by the white arrows Adrv and Acornering in FIG. Accordingly, the lateral force increases as the driving force of the rear wheel 14 decreases, and oversteer is suppressed as the yaw moment increases.

また、図１１に示す前輪平均車輪速ＮFaveが後輪平均車輪速ＮRaveより低い走行状況（ＮFave＜ＮRave）では、図９と同じく電子制御カップリング８を介して後輪１４から前輪４へとトルクが移動している。即ち、後輪１４の駆動力の一部が前輪４に分配されることにより、トルク移動相当分だけ前輪４が駆動力を発生すると共に後輪１４の駆動力が低下している。このときには最終制御量Ｔがヨーレイト対応制御量Ｔyだけ増加補正されるため（Ｔ＝Ｔbase＋Ｔy）、最終制御量Ｔの増加に応じて実際の前後輪４，１４間の駆動力分配も増加する。結果として後輪１４から前輪４へのトルク移動量が増加し、図１１に白抜き矢印Ａdrv，Ａcorneringで示すように後輪１４の駆動力が低下する一方、前輪４の駆動力が増加する。従って、後輪１４の駆動力の低下に伴って横力が増加し、ヨーモーメントの増加に応じてオーバステアが抑制される。   Further, in the traveling state where the average front wheel speed NFave shown in FIG. 11 is lower than the average rear wheel speed NRave (NFave <NRave), the torque from the rear wheel 14 to the front wheel 4 via the electronically controlled coupling 8 is the same as in FIG. Is moving. That is, a part of the driving force of the rear wheel 14 is distributed to the front wheel 4, so that the front wheel 4 generates the driving force corresponding to the torque movement and the driving force of the rear wheel 14 is reduced. At this time, since the final control amount T is corrected to be increased by the yaw rate corresponding control amount Ty (T = Tbase + Ty), the actual driving force distribution between the front and rear wheels 4 and 14 increases as the final control amount T increases. As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 increases, and the driving force of the rear wheel 14 decreases while the driving force of the front wheel 4 increases as shown by the white arrows Adrv and Acornering in FIG. Accordingly, the lateral force increases as the driving force of the rear wheel 14 decreases, and oversteer is suppressed as the yaw moment increases.

アンダステア及びオーバステア時の前後輪４，１４間の駆動力分配の制御は以上のように実行され、重複する説明はしないが本実施形態の車両の駆動力分配制御装置によれば、ＦＲ車ベースの４輪駆動車において第１実施形態で説明したものと全く同様の作用効果を得ることができる。
以上で実施形態の説明を終えるが、本発明の態様はこの実施形態に限定されるものではない。例えば上記実施形態では、目標旋回状態指標としてヨーレイトＹＲを適用したが、車両の旋回状態と相関する指標であればこれに限ることはなく、例えばヨーレイトに代えて横加速度センサ２６により検出された横加速度ＧＹを適用してもよい。 The control of the driving force distribution between the front and rear wheels 4 and 14 at the time of understeer and oversteer is performed as described above. Although not redundantly described, according to the vehicle driving force distribution control device of the present embodiment, In the four-wheel drive vehicle, exactly the same functions and effects as those described in the first embodiment can be obtained.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the yaw rate YR is applied as the target turning state index. However, the present invention is not limited to this as long as the index correlates with the turning state of the vehicle. For example, the lateral acceleration detected by the lateral acceleration sensor 26 instead of the yaw rate is used. The acceleration GY may be applied.

第１実施形態のＦＦ車ベースの４輪駆動車の駆動力分配制御装置を示す全体構成図である。1 is an overall configuration diagram showing a driving force distribution control device for a four-wheel drive vehicle based on an FF vehicle according to a first embodiment. アンダステア時にＥＣＵにより実行される電子制御カップリングの制御量の設定手順を示すブロック図である。It is a block diagram which shows the setting procedure of the control amount of the electronic control coupling performed by ECU at the time of understeer. アンダステアで前輪平均車輪速が後輪平均車輪速より高いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram which shows the control condition of driving force distribution when front wheel average wheel speed is higher than rear wheel average wheel speed in understeer. アンダステアで前輪平均車輪速が後輪平均車輪速より低いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram which shows the control condition of driving force distribution when a front-wheel average wheel speed is lower than a rear-wheel average wheel speed by understeer. オーバステア時にＥＣＵにより実行される電子制御カップリングの制御量の設定手順を示すブロック図である。It is a block diagram which shows the setting procedure of the control amount of the electronic control coupling performed by ECU at the time of oversteer. オーバステアで前輪平均車輪速が後輪平均車輪速より高いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is higher than the rear wheel average wheel speed in oversteer. オーバステアで前輪平均車輪速が後輪平均車輪速より低いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is lower than the rear wheel average wheel speed in oversteer. 第２実施形態におけるアンダステアで前輪平均車輪速が後輪平均車輪速より高いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram which shows the control condition of driving force distribution when a front-wheel average wheel speed is higher than a rear-wheel average wheel speed by the understeer in 2nd Embodiment. アンダステアで前輪平均車輪速が後輪平均車輪速より低いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram which shows the control condition of driving force distribution when a front-wheel average wheel speed is lower than a rear-wheel average wheel speed by understeer. オーバステアで前輪平均車輪速が後輪平均車輪速より高いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is higher than the rear wheel average wheel speed in oversteer. オーバステアで前輪平均車輪速が後輪平均車輪速より低いときの駆動力分配の制御状況を示す模式図である。It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is lower than the rear wheel average wheel speed in oversteer.

符号の説明Explanation of symbols

４ 前輪
８ 電子制御カップリング（駆動力分配手段）
１４ 後輪
２１ ４ＷＤ用ＥＣＵ（制御量算出手段、ステア特性判定手段、駆動力分配制御手段、
目標旋回状態指標決定手段、グリップ限界指標推定手段、要求横力算出手段、
駆動力低下量算出手段）
２４ ヨーレイトセンサ（実旋回状態指標検出手段）
２５ 車輪速センサ（車輪速検出手段） 4 Front wheel 8 Electronically controlled coupling (drive force distribution means)
14 rear wheel 21 4WD ECU (control amount calculation means, steering characteristic determination means, driving force distribution control means,
Target turning state index determining means, grip limit index estimating means, required lateral force calculating means,
Driving force reduction amount calculation means)
24 Yaw rate sensor (actual turning state index detection means)
25 Wheel speed sensor (wheel speed detection means)

Claims (3)

車両の前後輪間に設けられ、駆動源から上記前輪に伝達された駆動力の一部を上記後輪側に可変分配可能な駆動力分配手段と、
上記車両の旋回状態に基づいて上記後輪側に分配させるべき駆動力分配に対する補正量として旋回対応制御量を算出する制御量算出手段と、
上記車両の現在のステア特性を判定するステア特性判定手段と、
上記前後輪の車輪速をそれぞれ検出する車輪速検出手段と、
上記車輪速検出手段による検出結果に基づき上記前輪の車輪速が後輪の車輪速より高いと判定した場合、上記ステア特性判定手段により判定されたステア特性がアンダステアのときには上記前後輪間の駆動力分配を上記旋回対応制御量に基づき増加補正する一方、該ステア特性がオーバステアのときには上記前後輪間の駆動力分配を上記旋回対応制御量に基づき減少補正し、上記前輪の車輪速が後輪の車輪速より低いと判定した場合、上記ステア特性判定手段により判定されたステア特性に関わらず上記前後輪間の駆動力分配を上記旋回対応制御量に基づき減少補正し、該補正後の駆動力分配に基づいて上記駆動力分配手段を制御する駆動力分配制御手段と
を備えたことを特徴とする車両の駆動力分配制御装置。 Driving force distribution means provided between the front and rear wheels of the vehicle and capable of variably distributing a part of the driving force transmitted from the driving source to the front wheels to the rear wheel side;
Control amount calculation means for calculating a turn corresponding control amount as a correction amount for the driving force distribution to be distributed to the rear wheel side based on the turning state of the vehicle;
Steer characteristic determining means for determining the current steering characteristic of the vehicle;
Wheel speed detecting means for detecting the wheel speeds of the front and rear wheels,
When it is determined that the wheel speed of the front wheel is higher than the wheel speed of the rear wheel based on the detection result by the wheel speed detection means , the driving force between the front and rear wheels is when the steering characteristic determined by the steering characteristic determination means is understeer. While the distribution is increased and corrected based on the turning control amount, when the steering characteristic is oversteer, the driving force distribution between the front and rear wheels is reduced and corrected based on the turning control amount so that the front wheel speed is If it is determined that the vehicle speed is lower than the wheel speed, the driving force distribution between the front and rear wheels is corrected to decrease based on the turning control amount regardless of the steering characteristic determined by the steering characteristic determination unit , and the corrected driving force distribution is obtained. Driving force distribution control means for controlling the driving force distribution means based on
Vehicles of the driving force distribution control device comprising the. 車両の前後輪間に設けられ、駆動源から上記後輪に伝達された駆動力の一部を上記前輪側に可変分配可能な駆動力分配手段と、
上記車両の旋回状態に基づいて上記前輪側に分配させるべき駆動力分配に対する補正量として旋回対応制御量を算出する制御量算出手段と、
上記車両の現在のステア特性を判定するステア特性判定手段と、
上記前後輪の車輪速をそれぞれ検出する車輪速検出手段と、
上記車輪速検出手段による検出結果に基づき上記後輪の車輪速が前輪の車輪速より高いと判定した場合、上記ステア特性判定手段により判定されたステア特性がアンダステアのときには上記前後輪間の駆動力分配を上記旋回対応制御量に基づき減少補正する一方、該ステア特性がオーバステアのときには上記前後輪間の駆動力分配を上記旋回対応制御量に基づき増加補正し、上記後輪の車輪速が前輪の車輪速より低いと判定した場合、上記ステア特性判定手段により判定されたステア特性に関わらず上記前後輪間の駆動力分配を上記旋回対応制御量に基づき減少補正し、該補正後の駆動力分配に基づいて上記駆動力分配手段を制御する駆動力分配制御手段と
を備えたことを特徴とする車両の駆動力分配制御装置。 Driving force distribution means provided between the front and rear wheels of the vehicle and capable of variably distributing a part of the driving force transmitted from the driving source to the rear wheel to the front wheel side;
Control amount calculation means for calculating a turn corresponding control amount as a correction amount for the driving force distribution to be distributed to the front wheel side based on the turning state of the vehicle;
Steer characteristic determining means for determining the current steering characteristic of the vehicle;
Wheel speed detecting means for detecting the wheel speeds of the front and rear wheels,
When it is determined that the wheel speed of the rear wheel is higher than the wheel speed of the front wheel based on the detection result by the wheel speed detecting means , the driving force between the front and rear wheels is when the steer characteristic determined by the steer characteristic determining means is understeer. While the distribution is reduced and corrected based on the turning control amount, when the steering characteristic is oversteer, the driving force distribution between the front and rear wheels is increased and corrected based on the turning control amount, and the wheel speed of the rear wheel is adjusted to that of the front wheel. If it is determined that the vehicle speed is lower than the wheel speed, the driving force distribution between the front and rear wheels is corrected to decrease based on the turning control amount regardless of the steering characteristic determined by the steering characteristic determination unit , and the corrected driving force distribution is obtained. Driving force distribution control means for controlling the driving force distribution means based on
Vehicles of the driving force distribution control device comprising the. 上記ステア特性判定手段は、
上記車両の走行状態に基づいて目標旋回状態指標を決定する目標旋回状態指標決定手段と、
上記車両の実際の旋回状態指標を検出する実旋回状態指標検出手段とを備え、
上記目標旋回状態指標と上記実旋回状態指標とに基づき現在の車両のステア特性を判定すると共に、
上記制御量算出手段は、
上記ステア特性判定手段によりステア特性として判定されたアンダステア及びオーバステアに基づき上記前後輪のスリップ輪を特定し、該スリップ輪の駆動力及び横力からグリップ限界と相関するグリップ限界指標を推定するグリップ限界指標推定手段と、
上記車両の旋回状態に基づいて上記アンダステアまたはオーバステアを抑制するための要求ヨーモーメントを算出し、該要求ヨーモーメントを達成可能な上記スリップ輪の要求横力を算出する要求横力算出手段と、
上記グリップ限界指標算出手段により算出されたグリップ限界指標を前提として、上記要求横力算出手段により算出された要求横力を達成するために必要なスリップ輪の駆動力低下量を算出する駆動力低下量算出手段とを備え、
上記駆動力低下量算出手段により算出されたスリップ輪の駆動力低下量に応じて上記旋回対応制御量を算出することを特徴とする請求項１または２記載の車両の駆動力分配制御装置。 The steer characteristic determining means includes
Target turning state index determining means for determining a target turning state index based on the running state of the vehicle;
An actual turning state index detecting means for detecting an actual turning state index of the vehicle,
A steering characteristic of the current vehicle is determined based on the target turning state index and the actual turning state index,
The control amount calculation means is
The grip limit for identifying the slip wheel of the front and rear wheels based on the understeer and oversteer determined as the steer characteristic by the steer characteristic determination means, and estimating a grip limit index correlated with the grip limit from the driving force and lateral force of the slip wheel Index estimation means;
A required lateral force calculating means for calculating a required yaw moment for suppressing the understeer or oversteer based on the turning state of the vehicle, and calculating a required lateral force of the slip wheel capable of achieving the required yaw moment;
Based on the grip limit index calculated by the grip limit index calculating means, the driving force decrease that calculates the slip wheel driving force reduction amount required to achieve the required lateral force calculated by the required lateral force calculating means. A quantity calculating means,
Driving force distribution control device for a vehicle according to claim 1 or 2, wherein in response to the driving force reduction amount of the slip ring which is calculated by the above SL driving force reduction amount calculating means, and calculates the turning corresponding control amount.
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JP2004106649A (en) * 2002-09-17 2004-04-08 Fuji Heavy Ind Ltd Power distribution controller of four-wheel drive vehicle
JP2005162097A (en) * 2003-12-04 2005-06-23 Mitsubishi Motors Corp Transmission system for four-wheel drive vehicle

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JPH07117509A (en) * 1993-10-20 1995-05-09 Nissan Motor Co Ltd Yawing movement amount controller of vehicle
JP2004106649A (en) * 2002-09-17 2004-04-08 Fuji Heavy Ind Ltd Power distribution controller of four-wheel drive vehicle
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