JP2005007933A

JP2005007933A - Straight running state determination device for vehicle

Info

Publication number: JP2005007933A
Application number: JP2003171174A
Authority: JP
Inventors: Keiyu Kin; 圭勇金; Osamu Yano; 修矢野
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2003-06-16
Filing date: 2003-06-16
Publication date: 2005-01-13

Abstract

【課題】車輪速センサを用いて車輌の直進走行を判定するとき、タイヤ径のばらつきを補正して正確な直進走行状態の判定が可能な車輌の直進走行状態判定装置を提供する。
【解決手段】車輌の走行時に学習スイッチ信号ＧＳが定常走行状態判定手段１２及び学習値演算手段１３へ入力されて学習が開始すると、定常走行状態判定手段１２は、車輌が直進状態で定常走行していると判定するとき、学習値演算手段１３により前輪左右車輪回転速度差及び後輪左右車輪回転速度差を所定の時間に亘って取得し、これにより前輪左右車輪学習値と後輪左右車輪学習値を求め、これらを学習値記憶手段１４に記憶する。直進走行状態判定手段１５が車輌の直進走行状態の判定を行うとき、前輪左右車輪回転速度差及び後輪左右車輪回転速度差をこれらの学習値で補正して、その補正した値により直進走行状態の判定を行う。
【選択図】図２There is provided a vehicle straight traveling state determination device capable of accurately determining a straight traveling state by correcting variations in tire diameters when determining straight traveling of a vehicle using a wheel speed sensor.
When a learning switch signal GS is input to a steady running state determining means 12 and a learned value calculating means 13 during learning of a vehicle and learning is started, the steady running state judging means 12 makes steady running with the vehicle running straight. When it is determined that the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference are acquired over a predetermined time by the learning value calculation means 13, the front wheel left and right wheel learning value and the rear wheel left and right wheel learning are acquired. Values are obtained and stored in the learned value storage means 14. When the straight traveling state determination means 15 determines the straight traveling state of the vehicle, the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference are corrected by these learning values, and the straight traveling state is determined by the corrected values. Judgment is made.
[Selection] Figure 2

Description

【０００１】
【発明の属する技術分野】
本発明は、四輪車輌の各車輪回転速度を検出して直進走行状態判定を行う車輌の直進走行状態判定装置に関し、特に、タイヤ径のばらつきによって生ずる各車輪回転速度のばらつきを補正して直進走行状態判定を行う車輌の直進走行状態判定装置に関する。
【０００２】
【従来の技術】
従来から、四輪車輌における左右車輪の回転速度の差から車輌の直進走行状態を判定する車輌の直進走行状態判定装置が知られている。その直進走行状態判定の原理は、車輌が旋回すると左右の車輪間でその回転速度に差が生じるが、直進しているときにはその差が生じないという簡単な現象に基づく。
この直進走行状態判定技術は、車輌が直進走行状態にあるときに限り、タイヤの空気圧低下を検知する技術に応用することができる。車輌が直進走行状態にあるとき左右の車輪間に回転速度に差が生じるときは、タイヤの空気圧が低下して車輪の径が実効的に小さくなったと判断するのである。例えば、特許文献１では、この考えの基づきタイヤの空気圧低下を検知する。そして、車両が旋回するとき、すなわち、左右車輪の車輪回転速度の差から求められる横加速度に所定の閾値以上の値を検出したときは、空気圧低下の検知を禁止するようにしている。
【０００３】
【特許文献１】
特開平１０−１００６２２号公報（段落番号［０００９］〜［００３５］、図１〜図６参照）
【０００４】
【発明が解決しようとする課題】
しかしながら、従来の直進走行状態判定装置においては、製造時のタイヤ径の初期ばらつきやタイヤ空気圧調整のばらつき、タイヤの経時磨耗などによって生じるタイヤ径の差によって、実際には直進走行していても旋回状態にあると判断してしまうことがある。このような直進走行状態判定の誤判断が行われると、タイヤの空気圧低下を正しく検知をすることができなくなる。
【０００５】
本発明は、このような事情に鑑みてなされたものであり、その目的とするところは、車輪速センサを用いて車輌の直進走行状態を判定するとき、製造時のタイヤ径の初期ばらつきやタイヤ空気圧調整のばらつき、タイヤの経時磨耗などによって生じるタイヤ径の誤差を補正して、正確に直進走行状態判定を行うことができる車輌の直進走行状態判定装置を提供することにある。
【０００６】
【課題を解決するための手段】
前記の目的を達成するため、請求項１の発明における車輌の直進走行状態判定装置は、四輪車輌における各車輪の回転速度に基づいて車輌の直進走行状態を判定する車輌の直進走行状態判定装置であって、タイヤ径のばらつきによって生ずる各車輪の回転速度の速度差をあらかじめ学習によって求め、その学習によって求められた各車輪の回転速度の速度差を補正のための学習値とし、車輌が走行するときに得られる各車輪の回転速度の速度差をその学習値によって補正し、その補正された各車輪の回転速度差によって当該車輌の直進走行状態を判定することを特徴とする。
【０００７】
すなわち、請求項１の発明における車輌の直進走行状態判定装置によれば、ユーザが、あらかじめ、各車輪のタイヤ空気圧が調整されている状態で前輪側の左右車輪回転速度差と後輪側の左右車輪回転速度差とに基づいてタイヤ径のばらつきによって生じるばらつき回転速度差を求めておく。そして、実際に直進走行状態判定を行うときに測定される前輪側の左右車輪回転速度差と後輪側の左右車輪回転速度差を、先に求めたばらつき回転速度差によって補正する。これによって、タイヤ径のばらつきに関係なく、補正後の前輪側の左右車輪回転速度差と後輪側の左右車輪回転速度差に基づいて正確に車輌の直進走行状態判定を行うことができる。
【０００８】
また、請求項２の発明における車輌の直進走行状態判定装置は、四輪車輌における各車輪の回転速度に基づいて車輌の直進走行状態を判定する車輌の直進走行状態判定装置であって、各車輪の回転速度を演算して前輪左右車輪回転速度差及び後輪左右車輪回転速度差を求める左右車輪回転速度差演算手段と、その前輪左右車輪回転速度差及び後輪左右車輪回転速度差を補正するための補正値の学習を指示するスイッチ手段と、そのスイッチ手段が導通しているときに、前輪左右車輪回転速度差及び後輪左右車輪回転速度差を所定の時間に亘って取得し、その前輪左右車輪回転速度差及び後輪左右車輪回転速度差を演算して前輪左右車輪回転速度差比学習値及び後輪左右車輪回転速度差比学習値を求める学習値演算手段と、その前輪左右車輪回転速度差比学習値及び後輪左右車輪回転速度差比学習値を記憶する学習値記憶手段と、前記スイッチ手段が遮断しているときに、前記の前輪左右車輪回転速度差及び後輪左右車輪回転速度差をその学習値記憶手段に記憶されている前輪左右車輪回転速度差比学習値及び後輪左右車輪回転速度差比学習値で補正し、その補正によって得られた補正後前輪左右車輪回転速度差及び補正後後輪左右車輪回転速度差に基づいて車両の直進走行状態の判定を行う直進走行状態判定手段とを備えることを特徴とする。
【０００９】
すなわち、請求項２の発明における車輌の直進走行状態判定装置によれば、ドライバが、車輌の走行時に初期学習を行うために学習スイッチをオンすると、学習スイッチ信号が定常走行状態判定手段と学習値演算手段へ入力されて学習が開始される。そして、その学習値演算手段が、前輪左右車輪回転速度差及び後輪左右車輪回転速度差を所定の時間に亘って学習し、各車輪におけるタイヤ径のばらつきを補正するための前輪左右車輪回転速度差比学習値及び後輪左右車輪回転速度差比学習値を演算する。そして、その前輪左右車輪回転速度差比学習値及び後輪左右車輪回転速度差比学習値を学習値記憶手段に記憶する。
なお、ここで、スイッチ手段が導通しているとは、人手又は自動の操作により電気的なスイッチ回路が導通している状態をいうだけでなく、スイッチ回路の導通状態への遷移又はその他の事象により、ハードウエア又はソフトウエア上のフラグがセットされかつそのフラグがセットされたままの状態をもいう。また、スイッチ手段が遮断しているとは、人手又は自動の操作により電気的なスイッチ回路が遮断している状態をいうだけでなく、スイッチ回路の遮断状態への遷移又はその他の事象により、ハードウエア又はソフトウエア上のフラグがクリアされかつそのフラグがクリアされたままの状態をもいう。以下、本明細書において同じ意味で使用する。
【００１０】
そして、ドライバが実際に車輌の直進走行状態判定を行うときに学習スイッチをオフすると、スイッチ手段は遮断され、定常走行状態判定手段と学習値演算手段の学習機能は停止される。このとき、直進走行状態判定手段が、左右車輪回転速度差演算手段から前輪左右車輪回転速度差及び後輪左右車輪回転速度差を取得し、学習値記憶手段から前輪左右車輪回転速度差比学習値及び後輪左右車輪回転速度差比学習値を取得し、前輪左右車輪回転速度差から前輪左右車輪回転速度差比学習値に車輌速度を乗じた値を減算して補正後前輪左右車輪回転速度差を求め、後輪左右車輪回転速度差から後輪左右車輪回転速度差比学習値に車輌速度を乗じた値を減算して補正後後輪左右車輪回転速度差を求める。これによって、直進走行状態判定手段は、補正後前輪左右車輪回転速度差及び補正後後輪左右車輪回転速度差によって車輌の直進走行状態判定を行うことができるので、タイヤ経のばらつきが補正された状態で正確に直進走行状態判定を行うことができる。
【００１１】
また、請求項３の発明における車輌の直進走行状態判定装置においては、その学習値演算手段が、前輪左右車輪回転速度差及び後輪左右車輪回転速度差を車輌の車輌速度で除算することによって前輪左右車輪回転速度差比及び後輪左右車輪回転速度差比を算出し、そのそれぞれ算出された前輪左右車輪回転速度差比及び後輪左右車輪回転速度差比を所定の時間に亘ってそれぞれ移動平均することによって前記前輪左右車輪回転速度差比学習値及び前記後輪左右車輪回転速度差比学習値を算出することを特徴とする。
【００１２】
例えば、１０ｍｓごとに検出された各車輪の回転速度に基づいて演算された前輪左右車輪回転速度差及び後輪左右車輪回転速度差は瞬時のデータであるので、過度的には直進部分もあれば旋回部分も存在している。そこで、請求項４の発明における車輌の直進走行状態判定装置は、所定の時間に亘ってサンプリングして演算された前輪左右車輪回転速度差比及び後輪左右車輪回転速度差比を移動平均して、直進走行時の補正データとして前輪左右車輪学習値及び後輪左右車輪学習値を求めている。これによって、学習時における車輌の定常走行状態を特定して、タイヤ経のばらつきを補正するための前輪左右車輪学習値及び後輪左右車輪学習値を求めることができる。
【００１３】
また、請求項４の発明における車輌の直進走行状態判定装置は、前輪左右車輪回転速度差をΔＶＦ、後輪左右車輪回転速度差をΔＶＲ、車輌速度をＶＶ、前輪左右車輪学習値をΔＶＦｒＧ、及び後輪左右車輪学習値をΔＶＲｒＧとしたとき、補正後前輪左右車輪回転速度差ΔＶＦ’は、ΔＶＦ’＝ΔＶＦ−ΔＶＦｒＧ×ＶＶによって演算され、補正後後輪左右車輪回転速度差ΔＶＲ’は、ΔＶＲ’＝ΔＶＲ−ΔＶＲｒＧ×ＶＶによって演算されることを特徴とする。
【００１４】
すなわち、請求項４の発明における車輌の直進走行状態判定装置によれば、四輪車輌における各車輪の回転速度が検出されれば、前輪左右車輪回転速度差ΔＶＦ、後輪左右車輪回転速度差ΔＶＲ、車輌速度ＶＶ、前輪左右車輪学習値ΔＶＦｒＧ、及び後輪左右車輪学習値ΔＶＲｒＧは簡単に求められる。なお、車輌速度は、後輪右車輪回転速度と後輪左車輪回転速度の平均値によって求められた速度である。したがって、補正後前輪左右車輪回転速度差ΔＶＦ’、及び補正後後輪左右車輪回転速度差ΔＶＲ’は前記の式によって簡単な演算で求めることができる。
【００１５】
また、請求項５の発明における車輌の直進走行状態判定装置においては、各車輪の回転速度はＡＢＳに備えられている車輪速センサによって検出されることを特徴とする。
【００１６】
すなわち、請求項５の発明における車輌の直進走行状態判定装置によれば、ＡＢＳに用いられている車輪速センサを利用して各車輪の車輪回転速度を検出しているので、新たに車輪速センサを設けなくても車輌の直進走行状態判定を行うことができる。このようにしてＡＢＳ用の既存の車輪速センサのみによって車輌の直進走行状態判定を行うことができるので、結果的には、直進走行状態判定装置を装備した車輌のコストダウンを図ることができる。
【００１７】
【発明の実施の形態】
まず、本実施の形態における車輌の直進走行状態判定装置の概要について説明する。ＡＢＳは車輪速センサの車輪速信号を検出してブレーキ圧制御を行うシステムであり、本実施の形態における車輌の直進走行状態判定装置は、このＡＢＳに用いられている車輪速センサが検出した車輪回転速度を利用して直進走行状態判定を行うシステムになっている。そして、直進走行状態判定装置が左右車輪の回転速度差に基づいて直進走行状態の判定を行う前に、あらかじめ、車輌の定常走行を特定してタイヤ径のばらつきを補正するための学習を行い、このときの左右車輪の回転速度差を学習値として記憶しておく。そして、実際の直進走行状態の判定時に検出された左右車輪の回転速度差を、記憶されている学習値によって補正する。これによって、タイヤ径のばらつきに関係なく正確な直進走行状態の判定を行うことができる。
【００１８】
以下、図面を用いて、本実施の形態における車輌の直進走行状態判定装置の実施の形態を詳細に説明する。図１は、本実施の形態における車輌の直進走行状態判定装置を搭載した車両のシステム構成図である。図１に示すように、車両Ｃは、ＦＲＯＮＴ（前）を下部にして、前輪右車輪ＦＲ、前輪左車輪ＦＬ、後輪右車輪ＲＲ、及び後輪左車輪ＲＬの４つの車輪を有する四輪車両である。また、各車輪にはそれぞれ対応した車輪速センサＳ（ＳＦＲ，ＳＦＬ，ＳＲＲ，ＳＲＬ）が備えられている。これらの４個の車輪速センサＳはＡＢＳ用に設けられたセンサであるが、ＡＢＳは周知の技術であるのでその説明は省略する。
【００１９】
各車輪速センサＳ（ＳＦＲ，ＳＦＬ，ＳＲＲ，ＳＲＬ）は、例えば、ホール素子等を用いて車輪速パルスを生成する一般的なセンサであり、それぞれ対応する車輪の車輪速パルスを、前輪右車輪回転速度ＶＦＲ、前輪左車輪回転速度ＶＦＬ、後輪右車輪回転速度ＶＲＲ、及び後輪左車輪回転速度ＶＲＬとして検出して直進走行状態判定装置１へ送信している。各車輪速センサＳが生成して直進走行状態判定装置１へ送信する車輪速パルスは、車輪回転速度が早くなるほど単位時間当たりのパルス数が多くなり、車輪回転速度が遅くなるほど単位時間当たりのパルス数が少なくなる。本実施の形態においては、この車輪速パルスに基づいて車輪回転速度や車輌速度を測定する。また、一般的には、車輌Ｃが直進するときには左右の車輪の回転速度はほぼ同じであり、車輌Ｃが旋回するとき内輪側の車輪の回転速度は外輪側の車輪の回転速度よりも遅くなる。
【００２０】
さらに、車輌Ｃの運転席の近傍には学習スイッチＳＷが備えられ、ドライバが学習スイッチＳＷをオンすると、学習スイッチ信号ＧＳが直進走行状態判定装置１へ入力されてタイヤ径のばらつきを補正するための学習が開始される。つまり、学習を開始する前に四輪の全てを規定の空気圧に設定してから、直進走行状態において学習スイッチＳＷをオンすると直進走行状態判定装置１へ学習スイッチ信号ＧＳが入力され、直進走行状態判定装置１において学習が開始される。この学習は、タイヤの製造ばらつきなどによる初期ばらつきや、走行過程におけるタイヤの磨耗ばらつきや空気圧調整ばらつきなどの経時ばらつきによって生じるタイヤ径のばらつきを補正するために行うものである。従って、学習スイッチＳＷは搭乗者の不注意や無意識な操作によって不用意にオンされないように、所定の時間（例えば３秒間）継続してオンするとか、２つ以上の条件によってオンするとか、２段スイッチ機構でオンするというようなセーフティスイッチシーケンスになっている。
【００２１】
このようにして学習スイッチＳＷがオンされると直進走行状態判定装置１に備えられた図示しないＣＰＵが学習開始を認識する。そして、車輌Ｃの走行状態において、ヨーレートや横加速度などのパラメータに基づいて直進状態で定常走行しているか否かの判定が行われる。なお、ヨーレートとは車輌Ｃが左右に向きを変える動きの速度であるが、ここでは、前輪ヨーレートは前輪の左右車輪の速度差に基づいて求めた値、後輪ヨーレートは後輪の左右車輪の速度差に基づいて求めた値とする。さらに、前輪ヨーレートを微分することにより前輪横加速度が求められ、後輪ヨーレートを微分することにより後輪横加速度が求められる。
【００２２】
このようにして求められたヨーレートや横加速度が所定の閾値以下であれば車輌Ｃは直進状態で定常走行しているものと判定し、このときの四輪における各車輪回転速度（ＶＦＲ、ＶＦＬ、ＶＲＲ、ＶＲＬ）の速度差を学習スイッチＳＷがオンしている間に学習する。そして、その学習の結果得られる速度差をタイヤ径のばらつきによる補正値として、直進走行状態判定装置１の図示しないメモリに記憶する。こうすることによって、直進走行状態判定装置１は、実際の直進走行状態判定を行うときに、そのメモリに記憶されている速度差の補正値によって実際に測定される速度差を補正することができる。すなわち、直進走行状態判定装置１は、実際に直進走行状態判定を行うときに各車輪回転速度（ＶＦＲ、ＶＦＬ、ＶＲＲ、ＶＲＬ）から算出した速度差に対して前記の補正値を減算または加算して補正後の速度差を求める。そして、直進走行状態判定装置１は補正後の速度差に基づいて車輌Ｃの直進走行状態判定を行う。これによってタイヤ径のばらつきが補正された状態で直進走行状態判定を行うことができる。
【００２３】
なお、前記の例では、ヨーレート及び横加速度のパラメータを用いて学習時における定常走行を判定する場合について述べたが、これに限ることはなく、各車輪の車輪回転速度から、車輌速度条件、車輪回転速度の変動条件、スリップ率の変動条件、ヨーレート条件、ヨーレート変動条件、横加速度条件、横加速度の変動条件、前後加速度条件、前後加速度の変動条件、悪路条件、ブレーキ条件、ＡＢＳ制御中条件、Ｆ／Ｓ条件、及び駆動輪トルク条件などの各種パラメータを求めて、それぞれの閾値と比較して定常走行の判定を行うこともできる。
【００２４】
図２は、本実施の形態における車輌の直進走行状態判定装置の構成を示すブロック図である。図２に示すように、直進走行状態判定装置１は、左右車輪回転速度差演算手段１１、定常走行状態判定手段１２、学習値演算手段１３、学習値記憶手段１４、及び直進走行状態判定手段１５を備えた構成となっている。そして、ＡＢＳの車輪速センサによって得られる前輪右車輪回転速度ＶＦＲ、前輪左車輪回転速度ＶＦＬ、後輪右車輪回転速度ＶＲＲ、及び後輪左車輪回転速度ＶＲＬが左右車輪回転速度差演算手段１１へ入力され、学習スイッチ信号ＧＳが定常走行状態判定手段１２と学習値演算手段１３へ入力されるシステム構成となっている。
【００２５】
左右車輪回転速度差演算手段１１は、前輪右車輪回転速度ＶＦＲと前輪左車輪回転速度ＶＦＬとの差分によって前輪左右車輪回転速度差ΔＶＦを算出し、後輪右車輪回転速度ＶＲＲと後輪左車輪回転速度ＶＲＬとの差分によって後輪左右車輪回転速度差ΔＶＲを算出する。
定常走行状態判定手段１２は、学習開始を指示する学習スイッチ信号ＧＳが入力されたとき、左右車輪回転速度差演算手段１１が演算した前輪左右車輪回転速度差ΔＶＦ及び後輪左右車輪回転速度差ΔＶＲから得られたヨーレートや横加速度に基づいて、学習時において車輌Ｃが直進状態で定常走行しているか否かの判定を行う機能を備えている。
【００２６】
学習値演算手段１３は、学習開始を指示する学習スイッチ信号ＧＳが入力され、かつ車輌Ｃが直進状態で定常走行していると判定されたとき、左右車輪回転速度差演算手段１１から入力される前輪左右車輪回転速度差ΔＶＦ及び後輪左右車輪回転速度差ΔＶＲを所定の時間に亘って学習し、各車輪におけるタイヤ径のばらつきを補正するための前輪左右車輪回転速度差比学習値ΔＶＦｒＧと後輪左右車輪回転速度差比学習値ΔＶＲｒＧを演算する機能を備えている。
【００２７】
学習値記憶手段１４は、学習値演算手段１３から取得した前輪左右車輪回転速度差比学習値ΔＶＦｒＧと後輪左右車輪回転速度差比学習値ΔＶＲｒＧを記憶する機能を備えている。
【００２８】
直進走行状態判定手段１５は、学習スイッチ信号ＧＳが遮断されているときに、左右車輪回転速度差演算手段１１から取得した前輪左右車輪回転速度差ΔＶＦ及び後輪左右車輪回転速度差ΔＶＲと、学習値記憶手段１４から取得した前輪左右車輪回転速度差比学習値ΔＶＦｒＧと後輪左右車輪回転速度差比学習値ΔＶＲｒＧとに基づいて、補正後前輪左右車輪回転速度差ΔＶＦＲ’及び補正後後輪左右車輪回転速度差ΔＶＲ’を算出し、その値に基づき車輌Ｃの直進走行状態の判定を行う。
【００２９】
次に、図２における車輌Ｃの直進走行状態判定装置の動作について説明する。車輌Ｃの走行時に初期学習を行うために学習スイッチ（図１のＳＷ）をオンすると、学習スイッチ信号ＧＳが定常走行状態判定手段１２及び学習値演算手段１３へ入力されて学習が開始される。そして、定常走行状態判定手段１２のヨーレートや横加速度によって車輌は直進状態で定常走行していると判定されると、学習値演算手段１３が、前輪左右車輪回転速度差ΔＶＦ及び後輪左右車輪回転速度差ΔＶＲを所定の時間に亘って学習し、各車輪におけるタイヤ径のばらつきを補正するための学習値（つまり、前輪左右車輪回転速度差比学習値ΔＶＦｒＧと後輪左右車輪回転速度差比学習値ΔＶＲｒＧ）を演算する。このようにして演算された前輪左右車輪回転速度差比学習値ΔＶＦｒＧと後輪左右車輪回転速度差比学習値ΔＶＲｒＧは学習記憶手段１４に記憶される。
【００３０】
次に、実際に車輌Ｃの直進走行状態判定を行うときには学習スイッチ（図１のＳＷ）がオフされて学習スイッチ信号ＧＳが遮断されるので、定常走行状態判定手段１２と学習値演算手段１３の学習機能は停止される。そして、直進走行状態判定手段１５が、左右車輪回転速度差演算手段１１から前輪左右車輪回転速度差ΔＶＦ及び後輪左右車輪回転速度差ΔＶＲを取得し、学習値記憶手段１４から前輪左右車輪回転速度差比学習値ΔＶＦｒＧと後輪左右車輪回転速度差比学習値ΔＶＲｒＧを取得する。さらに、直進走行状態判定手段１５は、補正後前輪左右車輪回転速度差ΔＶＦＲ’及び補正後後輪左右車輪回転速度差ΔＶＲ’を算出し、直進走行状態判定手段１５は、車輌Ｃの直進走行状態判定を行う。これによって、タイヤ径のばらつきが補正された状態で正確に直進走行状態判定を行うことができる。
なお、学習スイッチＳＷのオフは、人手でも可能であるが、ここでは一定時間の経過の後に自動的にオフされるものとする。
【００３１】
次に、本発明の直進走行状態判定装置における学習値演算ロジックと直進走行状態判定ロジックについて説明する。図３は、本発明の直進走行状態判定装置における学習値演算ロジックと直進走行状態判定ロジックの流れを示すフロー図である。直進走行状態判定装置１は、学習値演算部２と学習値記憶部３と直進走行状態判定演算部４を備えた構成となっている。なお、図３の構成を図２と対比すると、図３の学習値演算部２が図２の左右車輪回転速度差演算手段１１と学習値演算手段１３を構成し、図３の学習値記憶部３が図２の学習値記憶手段１４を構成し、図３の直進走行状態判定の演算部４が図２の直進走行状態判定手段を構成している。なお、図２における定常走行状態判定手段１２は、図３の学習値演算部３が行う演算ロジックには直接的には関係しないので、図３では省略されている。
【００３２】
また、図３における直進走行状態判定装置１は、図示しない車輪速センサによって検出された前輪右車輪回転速度ＶＦＲ、前輪左車輪回転速度ＶＦＬ、後輪右車輪回転速度ＶＲＲ、後輪左車輪回転速度ＶＲＬ、及び車輌速度ＶＶを入力し、かつ、タイヤの初期ばらつきを補正するための学習を開始する学習スイッチ信号ＧＳを入力するシステム構成となっている。なお、学習スイッチ信号ＧＳは、ドライバの判断により図示しない学習スイッチ（つまり、図１における学習スイッチＳＷ）がオンされたときに入力される。
【００３３】
次に、図３における演算ロジックの流れを説明する。最初に、四輪のタイヤ空気圧が規定値に設定されてから、走行状態において学習スイッチ信号ＳＷが入力される。これによって、直進走行状態判定装置１においてタイヤ径のばらつきを補正するための初期学習が開始される。そして、演算１のブロックにおいて、前輪右車輪回転速度ＶＦＲと前輪左車輪回転速度ＶＦＬの差分から前輪左右車輪回転速度差ΔＶＦが求められる。すなわち、ΔＶＦ＝ＶＦＲ−ＶＦＬが演算される。同様にして、後輪右車輪回転速度ＶＲＲと後輪左車輪回転速度ＶＲＬの差分から後輪左右車輪回転速度差ΔＶＲが求められる。すなわち、ΔＶＲ＝ＶＲＲ−ＶＲＬが演算される。
【００３４】
さらに、演算２のブロックにおいて、前輪左右車輪回転速度差ΔＶＦを車輌速度ＶＶで除算して前輪左右車輪回転速度差比ΔＶＦｒが求められる。すなわち、ΔＶＦｒ＝ΔＶＦ／ＶＶが演算される。同様にして、後輪左右車輪回転速度差ΔＶＲを車輌速度ＶＶで除算して後輪左右車輪回転速度差比ΔＶＲｒが求められる。すなわち、ΔＶＲｒ＝ΔＶＲ／ＶＶが演算される。なお、車輌速度ＶＶの算出式は、場合により各種使い分けられているが、ここではその一例として、ＶＶ＝（ＶＲＲ＋ＶＲＬ）／２によって算出されるものとする。すなわち、この場合、車輌速度ＶＶは、後輪右車輪回転速度ＶＲＲと後輪左車輪回転速度ＶＲＬの平均値である。
【００３５】
演算２のブロックで求められた前輪左右車輪回転速度差比ΔＶＦｒ及び後輪左右車輪回転速度差比ΔＶＲｒは、例えば、１０ｍｓごとに検出された各車輪回転速度（ＶＦＲ、ＶＦＬ、ＶＲＲ、ＶＲＬ）に基づいて算出された瞬時のデータであるので、過度的には直進部分もあれば旋回部分もある。そのため、所定の時間に亘って算出されたデータを移動平均して直進走行時のデータと見なす必要がある。具体的には、２〜３分間に亘ってサンプリングして演算した値を移動平均することによって直進走行時のデータと判断している。
【００３６】
そのため、演算３のブロックにおいて、所定時間Ｔに亘ってサンプリングして演算された前輪左右車輪回転速度差比ΔＶＦｒを積算して前輪左右車輪回転速度差比積算値ΣΔＶＦｒを求める。同様にして、所定時間Ｔに亘ってサンプリングして演算された後輪左右車輪回転速度差比ΔＶＲｒを積算して後輪左右車輪回転速度差比積算値ΣΔＶＲｒを求める。そして、演算４のブロックにおいて、前輪左右車輪回転速度差比積算値ΣΔＶＦｒを所定時間Ｔで除算して前輪左右車輪回転速度差比平均値ΔＶＦｒＡＶを求める。すなわち、ΔＶＦｒＡＶ＝ΣΔＶＦｒ／Ｔが演算される。同様にして、後輪左右車輪回転速度差比積算値ΣΔＶＲｒを所定時間Ｔで除算して後輪左右車輪回転速度差比平均値ΔＶＲｒＡＶを求める。すなわち、ΔＶＲｒＡＶ＝ΣΔＶＲｒ／Ｔが演算される。
【００３７】
さらに、演算５のブロックにおいて、前輪左右車輪回転速度差比平均値ΔＶＦｒＡＶに所定の係数を掛けて前輪左右車輪回転速度差比学習値ΔＶＦｒＧを求め、後輪左右車輪回転速度差比平均値ΔＶＲｒＡＶに所定の係数を掛けて後輪左右車輪回転速度差比学習値ΔＶＲｒＧを求め、これらの学習値（前輪左右車輪回転速度差比学習値ΔＶＦｒＧ、後輪左右車輪回転速度差比学習値ΔＶＲｒＧ）を学習値記憶部３に記録しておく。これによって直進走行状態判定における初期学習が終わるので、ドライバが図示しない学習スイッチＳＷ（図１参照）をオフすることによって学習スイッチ信号ＧＳが遮断され、学習演算部２における演算処理が終了する。すなわち、学習値記憶部３に記録された前輪左右車輪回転速度差比学習値ΔＶＦｒＧが前輪側の補正データとして用いられる前輪左右車輪学習値であり、学習値記憶部３に記録された後輪左右車輪回転速度差比学習値ΔＶＲｒＧが後輪側の補正データとして用いられる後輪左右車輪学習値である。
【００３８】
次に、学習スイッチＳＷ（図１参照）がオフされている状態で車輌Ｃの走行時に直進走行状態判定が行われると、直進走行状態判定演算部４は、前輪右車輪回転速度ＶＦＲと前輪左車輪回転速度ＶＦＬの差分から求めた前輪左右車輪回転速度差ΔＶＦ、及び後輪右車輪回転速度ＶＲＲと後輪左車輪回転速度ＶＲＬの差分から求めた後輪左右車輪回転速度差ΔＶＲを入力する。さらに、直進走行状態判定演算部４は、学習値記憶部３から前輪左右車輪回転速度差比学習値（前輪左右車輪学習値）ΔＶＦｒＧ及び後輪左右車輪回転速度差比学習値（後輪左右車輪学習値）ΔＶＲｒＧを取得する。そして、前輪左右車輪回転速度差ΔＶＦを前輪左右車輪回転速度差比学習値（前輪左右車輪学習値）ΔＶＦｒＧによって補正して補正後前輪左右車輪回転速度差ΔＶＦ’を求める。同様にして、後輪左右車輪回転速度差ΔＶＲを後輪左右車輪回転速度差比学習値（後輪左右車輪学習値）ΔＶＲｒＧによって補正して補正後後輪左右車輪回転速度差ΔＶＲ’を求める。
【００３９】
すなわち、補正後前輪左右車輪回転速度差ΔＶＦ’は、式（１）によって求められ、また、補正後後輪左右車輪回転速度差ΔＶＲ’は、式（２）によって求められる。
ΔＶＦ’＝ΔＶＦ−ΔＶＦｒＧ×ＶＶ（１）
ΔＶＲ’＝ΔＶＲ−ΔＶＲｒＧ×ＶＶ（２）
【００４０】
このようにして、実際に直進走行状態判定を行うときに、前輪左右車輪回転速度差ΔＶＦ及び後輪左右車輪回転速度差ΔＶＲをあらかじめ学習しておいた学習値によって補正することにより、タイヤ径の初期ばらつきや経時ばらつきを補正して正確な直進走行状態判定を行うことができる。したがって、タイヤの空気圧低下検知などを高精度に行うことができる。
【００４１】
次に、フローチャートを用いて、学習によって得られた学習値による補正に基づいて直進走行状態判定の処理の流れを説明する。
図４は、本実施の形態の直進走行状態判定装置１における学習処理と直進走行状態判定処理の流れを示すフローチャートである。まず、学習スイッチＳＷがオンされると、定常走行状態判定手段１２は、車輌Ｃの直進走行状態の安定性を判別する。そのために、前輪右車輪回転速度ＶＦＲ、前輪左車輪回転速度ＶＦＬ、後輪右車輪回転速度ＶＲＲ、及び後輪左車輪回転速度ＶＲＬが左右車輪回転速度差演算手段１１を介して定常走行状態判定手段１２へ入力され、定常走行状態判定装置１２は、この入力された各車輪回転速度（ＶＦＲ、ＶＦＬ、ＶＲＲ、ＶＲＬ）に基づいて車両の直進走行状態を示すパラメータを演算して求める（ステップＳ１）。そして、そのパラメータに基づいて安定した直進走行状態にあるか否かを判定する。ここで、パラメータの例としては、前輪左右車輪回転速度差ΔＶＦに基づいて求めた前輪ヨーレートや後輪左右車輪回転速度差ΔＶＲに基づいて求めた後輪ヨーレートなどがある。ここでは、これらの値を所定の閾値と比較することによって、車輌Ｃが定常走行状態にあるか否かを判断する（ステップＳ２）。
【００４２】
ここで、車輌Ｃが定常走行状態にない場合、つまり、車輌Ｃが旋回等している場合は（ステップＳ２でＮｏの場合）、補正値の学習処理を行わず、直進走行の安定時間をカウントするカウンタをクリアして終了する（ステップＳ３）。
一方、車輌Ｃが定常走行状態にある場合は（ステップＳ２でＹｅｓの場合）、補正値の学習処理を開始する。まず、例えば、１０ｍｓごとに各車輪の回転速度（ＶＦＲ、ＶＦＬ、ＶＲＲ、ＶＲＬ）をサンプリングし（ステップＳ４）、これらを左右車輪回転速度差演算手段１１に入力し、前輪左右車輪回転速度差ΔＶＦを得る（ステップＳ５）。次に、この前輪左右車輪回転速度差ΔＶＦを車輌速度ＶＶで除算し（ステップＳ５）、前輪左右車輪回転速度差比ΔＶＦｒを算出する（ステップＳ６）。続けて、前輪左右車輪回転速度差比ΔＶＦｒについて加算演算（ΣΔＶＦｒ）を実行する（ステップＳ７）。また、後輪左右車輪についても同様の処理をし、同様の加算演算（ΣΔＶＲｒ）を実行する（ステップＳ４〜Ｓ７）。
【００４３】
次に、移動平均処理を行うために、前記和演算の回数が規定の回数に達したか否かを判定する（ステップＳ８）。ここで、加算演算回数が規定の回数に達していないときは（ステップＳ８でＮｏの場合）、カウンタを１カウントアップして（ステップＳ９）、この処理フローをいったん終了する。ただし、図４の処理フローは１０ｍｓごとに実行されるので、前記ステップＳ４〜ステップＳ７の処理は、加算回数が規定の回数に達するまで繰り返えされる。そして、加算演算回数が規定の回数に達し場合は（ステップＳ８でＹｅｓの場合）、規定回数の演算で求められた前輪左右車輪回転速度差ΔＶＦｒの加算値（ΣΔＶＦｒ）を規定回数で割って前輪左右車輪回転速度差平均値ΔＶＦｒＡｖを算出する（ステップＳ１０）。同様にして、後輪左右車輪回転速度差ΔＶＲｒの加算値（ΣΔＶＲｒ）を規定回数で割って後輪左右車輪回転速度差平均値ΔＶＲｒＡｖを算出する（ステップＳ１０）。
【００４４】
次に、学習スイッチＳＷがオフされているか否かによって補正値の学習処理の終了を判定する（ステップＳ１１）。ここで、補正値の学習処理が終了していない場合は（ステップＳ１１でＮｏの場合）、前輪左右車輪回転速度差比平均値ΔＶＦｒＡｖ及び後輪左右車輪回転速度差比平均値ΔＶＲｒＡｖを補正のためのオフセット学習値としてメモリに記憶させ（ステップＳ１２）、補正値の学習処理を終了する。
一方、ステップＳ１１で補正値の学習処理がすでに終了している場合は（ステップＳ１１でＹｅｓの場合）、前記オフセット学習値ΔＶＦｒＡｖ及びΔＶＲｒＡｖを前記式（１）及び式（２）において用いることにより、補正後前輪左右車輪回転速度差ΔＶＦ’及び補正後後輪左右車輪回転速度差ΔＶＲ’を算出することができる（ステップＳ１３）。
【００４５】
この補正後前輪左右車輪回転速度差ΔＶＦ’及び補正後後輪左右車輪回転速度差ΔＶＲ’の値から車輌Ｃが直進状態であるか否かを判定する。すなわち、補正後前輪左右車輪回転速度差ΔＶＦ’及び補正後後輪左右車輪回転速度差ΔＶＲ’が所定値以下であれば直進状態であると判定し、補正後前輪左右車輪回転速度差ΔＶＦ’及び補正後後輪左右車輪回転速度差ΔＶＲ’が所定値以上であれば旋回状態であると判定する（ステップＳ１４）。そして、直進走行状態であると判定された場合は（ステップＳ１４でＹｅｓの場合）、直進フラグをセットする（ステップＳ１５）。また、直進走行状態ではないと判定された場合は（ステップＳ１５でＮｏの場合）、直進フラグをリセットする（ステップＳ１６）。これによって、直進フラグが立っていれば車輌Ｃが直進走行状態にあると判定できるので、例えば、タイヤの空気圧低下検知を直ちに行うことができる。
【００４６】
以上述べた実施の形態は本発明を説明するための一例であり、本発明は、前記の実施の形態に限定されるものではなく、発明の要旨の範囲で種々の変形が可能である。前記の実施の形態では、ＡＢＳ用の車輪速センサを用いて各車輪回転速度を検出してＣの直進走行状態判定を行う場合について説明したが、これに限定されるものではない。例えば、ＡＢＳ用とは別の車輪速センサを用いてもよいし、ヨーレートセンサや加速度センサなど他のセンサと併用して直進走行状態判定を行ってもよいことはいうまでもない。
【００４７】
【発明の効果】
以上説明したように、本発明における車輌の直進走行状態判定装置によれば、タイヤ製造時の初期のタイヤ径ばらつきやタイヤの磨耗や空気圧調整ずれなどによるタイヤ径のばらつきに起因する左右車輪の回転速度差を、車輌の実際の走行の初期の期間に学習によって求める。そして、その後、車輌が実際に走行し、直進走行状態判定を行うときに、各車輪の速度差をこの学習値によって補正する。これによって、タイヤ径のばらつきが補償されて正確な直進走行状態判定を行うことができる。また、このようにして補正された各車輪の速度差を用いることによって、ヨーレートや横加速度の精度をさらに向上させることができる。
【図面の簡単な説明】
【図１】本発明における車輌の直進走行状態判定装置を搭載した車輌のシステム構成図である。
【図２】本発明における車輌の直進走行状態判定装置の構成を示すブロック図である。
【図３】本発明の直進走行状態判定装置における学習値演算ロジックと直進走行状態判定ロジックの流れを示すフロー図である。
【図４】本発明の直進走行状態判定装置における学習処理と直進走行状態判定処理の流れを示すフローチャートである。
【符号の説明】
１直進走行状態判定装置
２学習値演算部
３学習値記憶部
４直進走行状態判定演算部
１１左右車輪回転速度差演算手段
１２定常走行状態判定手段
１３学習値演算手段
１４学習値記憶手段
１５直進走行状態判定手段
ＳＷ学習スイッチ
ＶＦＲ前輪右車輪回転速度
ＶＦＬ前輪左車輪回転速度
ＶＲＲ後輪右車輪回転速度
ＶＲＬ後輪左車輪回転速度
ＶＶ車輌速度
ΔＶＦ前輪左右車輪回転速度差
ΔＶＲ後輪左右車輪回転速度差
ΔＶＦ’ 補正後前輪左右車輪回転速度差
ΔＶＲ’ 補正後後輪左右車輪回転速度差
ＧＳ学習スイッチ信号
ΔＶＦｒＧ前輪左右車輪回転速度差比学習値（前輪左右車輪学習値）
ΔＶＲｒＧ後輪左右車輪回転速度差比学習値（後輪左右車輪学習値）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle straight traveling state determination device that detects a straight traveling state by detecting the rotational speed of each wheel of a four-wheel vehicle, and more particularly to a straight traveling by correcting variations in rotational speeds of wheels caused by variations in tire diameter. The present invention relates to a straight traveling state determination device for a vehicle that performs traveling state determination.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a straight traveling state determination device for a vehicle that determines a straight traveling state of a vehicle from a difference in rotational speed between left and right wheels in a four-wheel vehicle is known. The principle of the straight running state determination is based on a simple phenomenon that a difference in rotational speed occurs between the left and right wheels when the vehicle turns, but no difference occurs when the vehicle is traveling straight.
This straight traveling state determination technique can be applied to a technique for detecting a decrease in tire air pressure only when the vehicle is in a straight traveling state. When there is a difference in rotational speed between the left and right wheels when the vehicle is running straight, it is determined that the tire air pressure has decreased and the wheel diameter has effectively decreased. For example, in Patent Document 1, a decrease in tire air pressure is detected based on this idea. When the vehicle turns, that is, when a value equal to or greater than a predetermined threshold is detected in the lateral acceleration obtained from the difference between the wheel rotational speeds of the left and right wheels, detection of a decrease in air pressure is prohibited.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-100522 (see paragraph numbers [0009] to [0035], FIGS. 1 to 6)
[0004]
[Problems to be solved by the invention]
However, in the conventional straight running state judging device, the actual turning due to the difference in the tire diameter caused by the initial variation of the tire diameter at the time of manufacture, the variation of the tire pressure adjustment, the wear of the tire over time, etc. It may be judged that it is in a state. If such a straight traveling state determination is erroneously determined, a decrease in tire air pressure cannot be detected correctly.
[0005]
The present invention has been made in view of such circumstances, and the object of the present invention is to determine the initial variation in tire diameter during manufacturing and tires when determining the straight running state of a vehicle using a wheel speed sensor. It is an object of the present invention to provide a straight running state determination device for a vehicle that can accurately determine a straight running state by correcting a tire diameter error caused by variations in air pressure adjustment, tire wear over time, and the like.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a straight traveling state determination device for a vehicle according to the first aspect of the present invention is a straight traveling state determination device for a vehicle that determines the straight traveling state of the vehicle based on the rotational speed of each wheel in the four-wheel vehicle. The speed difference between the rotational speeds of the wheels caused by the variation in the tire diameter is obtained by learning in advance, and the speed difference between the rotational speeds of the wheels obtained by the learning is used as a learning value for correction. The speed difference between the rotational speeds of the wheels obtained at the time is corrected by the learned value, and the straight traveling state of the vehicle is determined by the corrected rotational speed difference of the wheels.
[0007]
That is, according to the straight running state determination apparatus for a vehicle according to the first aspect of the present invention, the user can adjust the difference between the rotational speeds of the left and right wheels on the front wheel side and the left and right sides on the rear wheel side in a state where the tire air pressure of each wheel is adjusted in advance. Based on the wheel rotational speed difference, a variation rotational speed difference caused by a variation in tire diameter is obtained. Then, the front-wheel-side left-right wheel rotational speed difference and the rear-wheel-side left-right wheel rotational speed difference, which are measured when actually determining the straight running state, are corrected by the previously obtained variation rotational speed difference. Accordingly, it is possible to accurately determine the straight traveling state of the vehicle based on the corrected difference between the left and right wheel rotational speeds on the front wheel side and the left and right wheel rotational speed differences on the rear wheel side, regardless of variations in the tire diameter.
[0008]
According to a second aspect of the present invention, there is provided a straight traveling state determination device for a vehicle that determines a straight traveling state of a vehicle based on a rotational speed of each wheel in a four-wheel vehicle. Left and right wheel rotation speed difference calculating means for calculating the difference between the front wheel left and right wheel rotation speed difference and the rear wheel left and right wheel rotation speed difference, and correcting the front wheel left and right wheel rotation speed difference and the rear wheel left and right wheel rotation speed difference. A switch means for instructing learning of a correction value for the front wheel, and when the switch means is conductive, the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference are acquired over a predetermined time, and the front wheel Learning value calculating means for calculating a front wheel left / right wheel rotation speed difference ratio learning value and a rear wheel left / right wheel rotation speed difference ratio learning value by calculating a left / right wheel rotation speed difference and a rear wheel left / right wheel rotation speed difference, and a front wheel left / right wheel rotation Learning value storage means for storing a speed difference ratio learned value and a rear wheel left and right wheel rotational speed difference ratio learned value; and when the switch means is shut off, the front wheel left and right wheel rotational speed difference and rear wheel left and right wheel rotation The corrected front wheel left and right wheel rotational speeds obtained by correcting the speed difference with the front wheel left and right wheel rotational speed difference ratio learned value and the rear wheel left and right wheel rotational speed difference ratio learned value stored in the learned value storage means. The vehicle further includes a straight traveling state determination unit that determines a straight traveling state of the vehicle based on the difference and the difference between the corrected rear wheel left and right wheel rotational speeds.
[0009]
That is, according to the vehicle straight running state determination device in the invention of claim 2, when the driver turns on the learning switch to perform initial learning when the vehicle is traveling, the learning switch signal is transmitted to the steady traveling state determination unit and the learning value. Learning is started upon input to the computing means. And the learning value calculation means learns the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference over a predetermined time, and corrects the variation in the tire diameter in each wheel. The difference ratio learning value and the rear wheel left and right wheel rotation speed difference ratio learning value are calculated. Then, the front wheel left and right wheel rotational speed difference ratio learned value and the rear wheel left and right wheel rotational speed difference ratio learned value are stored in the learned value storage means.
Here, the switch means being conductive does not only mean a state where the electrical switch circuit is conductive by manual or automatic operation, but also a transition to the conductive state of the switch circuit or other events. This means that the flag on the hardware or software is set and the flag remains set. In addition, the switch means is not only in a state where the electrical switch circuit is interrupted by manual or automatic operation, but also by a transition to the cutoff state of the switch circuit or other events. The state where the flag on the hardware or software is cleared and the flag remains cleared. Hereinafter, the same meaning is used in this specification.
[0010]
If the learning switch is turned off when the driver actually determines the straight traveling state of the vehicle, the switch means is cut off, and the learning functions of the steady traveling state determination means and the learning value calculation means are stopped. At this time, the straight traveling state determination means acquires the front wheel left and right wheel rotation speed difference and the rear wheel left and right wheel rotation speed difference from the left and right wheel rotation speed difference calculation means, and the front wheel left and right wheel rotation speed difference ratio learning value from the learning value storage means. And the rear wheel left and right wheel rotational speed difference ratio learning value is obtained, and the corrected front wheel left and right wheel rotational speed difference is subtracted from the front wheel left and right wheel rotational speed difference ratio learned value multiplied by the vehicle speed. Subtract the value obtained by multiplying the rear wheel left and right wheel rotation speed difference ratio learning value by the vehicle speed from the rear wheel left and right wheel rotation speed difference to obtain the corrected rear wheel left and right wheel rotation speed difference. Thus, the straight traveling state determination means can determine the straight traveling state of the vehicle based on the corrected front wheel left and right wheel rotational speed difference and the corrected rear wheel left and right wheel rotational speed difference, so that the variation in tire travel is corrected. It is possible to accurately determine the straight traveling state according to the state.
[0011]
Further, in the vehicle straight running state judging device according to the invention of claim 3, the learning value calculating means divides the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference by the vehicle speed of the vehicle. The left and right wheel rotation speed difference ratio and the rear wheel left and right wheel rotation speed difference ratio are calculated, and the calculated front wheel left and right wheel rotation speed difference ratio and rear wheel left and right wheel rotation speed difference ratio are respectively calculated as moving averages over a predetermined time. In this way, the front wheel left and right wheel rotational speed difference ratio learned value and the rear wheel left and right wheel rotational speed difference ratio learned value are calculated.
[0012]
For example, the front wheel left / right wheel rotation speed difference and the rear wheel left / right wheel rotation speed difference calculated based on the rotation speed of each wheel detected every 10 ms are instantaneous data. There is also a swivel part. In view of this, the straight traveling state determination device for a vehicle in the invention of claim 4 averages the front wheel left and right wheel rotational speed difference ratio and the rear wheel left and right wheel rotational speed difference ratio which are sampled and calculated over a predetermined time. The front wheel left and right wheel learning values and the rear wheel left and right wheel learning values are obtained as correction data during straight traveling. Thereby, the steady running state of the vehicle at the time of learning can be specified, and the front wheel left / right wheel learning value and the rear wheel left / right wheel learning value for correcting the variation in tire diameter can be obtained.
[0013]
According to a fourth aspect of the present invention, there is provided a vehicle straight traveling state determination device in which a front wheel left / right wheel rotational speed difference is ΔVF, a rear wheel left / right wheel rotational speed difference is ΔVR, a vehicle speed is VV, a front wheel left / right wheel learning value is ΔVFrG, and When the rear wheel left / right wheel learning value is ΔVRrG, the corrected front wheel left / right wheel rotation speed difference ΔVF ′ is calculated by ΔVF ′ = ΔVF−ΔVFrG × VV, and the corrected rear wheel left / right wheel rotation speed difference ΔVR ′ is ΔVRr. It is calculated by '= ΔVR-ΔVRrG × VV.
[0014]
That is, according to the straight running state determination apparatus for a vehicle in the fourth aspect of the invention, if the rotational speed of each wheel in the four-wheel vehicle is detected, the front wheel left-right wheel rotational speed difference ΔVF and the rear wheel left-right wheel rotational speed difference ΔVR are detected. The vehicle speed VV, the front wheel left / right wheel learning value ΔVFrG, and the rear wheel left / right wheel learning value ΔVRrG can be easily obtained. The vehicle speed is a speed obtained by an average value of the rear wheel right wheel rotation speed and the rear wheel left wheel rotation speed. Therefore, the corrected front wheel left and right wheel rotational speed difference ΔVF ′ and the corrected rear wheel left and right wheel rotational speed difference ΔVR ′ can be obtained by a simple calculation using the above formula.
[0015]
According to a fifth aspect of the present invention, there is provided the vehicle straight running state determination device, wherein the rotational speed of each wheel is detected by a wheel speed sensor provided in the ABS.
[0016]
That is, according to the vehicle straight running state determination device in the invention of claim 5, since the wheel rotational speed of each wheel is detected using the wheel speed sensor used in the ABS, a new wheel speed sensor Even if the vehicle is not provided, it is possible to determine the straight running state of the vehicle. In this way, it is possible to determine the straight traveling state of the vehicle using only the existing wheel speed sensor for ABS. As a result, it is possible to reduce the cost of the vehicle equipped with the straight traveling state determination device.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
First, an outline of a straight traveling state determination device for a vehicle in the present embodiment will be described. The ABS is a system that detects a wheel speed signal of a wheel speed sensor and performs brake pressure control. The straight traveling state determination device for a vehicle in the present embodiment is a wheel detected by a wheel speed sensor used in the ABS. It is a system that makes a straight running state determination using the rotational speed. Then, before the straight travel state determination device determines the straight travel state based on the difference between the rotational speeds of the left and right wheels, it learns in advance to identify the steady travel of the vehicle and correct the tire diameter variation, The rotational speed difference between the left and right wheels at this time is stored as a learning value. Then, the rotational speed difference between the left and right wheels detected at the time of determining the actual straight traveling state is corrected by the stored learning value. As a result, it is possible to accurately determine the straight running state regardless of variations in the tire diameter.
[0018]
Hereinafter, embodiments of a straight traveling state determination device for a vehicle in the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram of a vehicle equipped with a vehicle straight traveling state determination device according to the present embodiment. As shown in FIG. 1, the vehicle C is a four-wheeled vehicle having four wheels: a front wheel right wheel FR, a front wheel left wheel FL, a rear wheel right wheel RR, and a rear wheel left wheel RL with FRONT (front) as a lower portion. It is a vehicle. Each wheel is provided with a corresponding wheel speed sensor S (SFR, SFL, SRR, SRL). These four wheel speed sensors S are sensors provided for ABS, but since ABS is a well-known technique, its description is omitted.
[0019]
Each wheel speed sensor S (SFR, SFL, SRR, SRL) is a general sensor that generates a wheel speed pulse by using, for example, a Hall element, and the wheel speed pulse of the corresponding wheel is transmitted to the front right wheel. The rotation speed VFR, the front wheel left wheel rotation speed VFL, the rear wheel right wheel rotation speed VRR, and the rear wheel left wheel rotation speed VRL are detected and transmitted to the straight traveling state determination device 1. The wheel speed pulse generated by each wheel speed sensor S and transmitted to the straight traveling state determination device 1 increases the number of pulses per unit time as the wheel rotation speed increases, and the pulse per unit time as the wheel rotation speed decreases. The number decreases. In the present embodiment, the wheel rotation speed and the vehicle speed are measured based on the wheel speed pulse. In general, when the vehicle C goes straight, the rotation speeds of the left and right wheels are substantially the same, and when the vehicle C turns, the rotation speed of the inner wheel is slower than the rotation speed of the outer wheel. .
[0020]
Further, a learning switch SW is provided in the vicinity of the driver's seat of the vehicle C, and when the driver turns on the learning switch SW, the learning switch signal GS is input to the straight traveling state determination device 1 to correct the tire diameter variation. Learning begins. In other words, when all of the four wheels are set to the prescribed air pressure before learning is started and the learning switch SW is turned on in the straight traveling state, the learning switch signal GS is input to the straight traveling state determination device 1, and the straight traveling state Learning is started in the determination apparatus 1. This learning is performed in order to correct variations in tire diameter caused by initial variations due to tire manufacturing variations, and variations over time such as tire wear variations and air pressure adjustment variations in the running process. Accordingly, the learning switch SW may be continuously turned on for a predetermined time (for example, 3 seconds), or may be turned on by two or more conditions so that the learning switch SW is not turned on carelessly or unintentionally by the passenger. The safety switch sequence is such that it is turned on by a step switch mechanism.
[0021]
When the learning switch SW is turned on in this way, a CPU (not shown) provided in the straight traveling state determination device 1 recognizes the start of learning. Then, in the traveling state of the vehicle C, it is determined whether or not the vehicle C is traveling in a straight line based on parameters such as the yaw rate and the lateral acceleration. The yaw rate is the speed at which the vehicle C changes its direction to the left and right. Here, the front wheel yaw rate is a value obtained based on the speed difference between the left and right wheels of the front wheel, and the rear wheel yaw rate is the value of the left and right wheels of the rear wheel. The value obtained based on the speed difference. Further, the front wheel lateral acceleration is obtained by differentiating the front wheel yaw rate, and the rear wheel lateral acceleration is obtained by differentiating the rear wheel yaw rate.
[0022]
If the yaw rate or lateral acceleration obtained in this way is below a predetermined threshold value, it is determined that the vehicle C is traveling in a straight line and steady running, and the wheel rotation speeds (VFR, VFL, (VRR, VRL) is learned while the learning switch SW is on. Then, the speed difference obtained as a result of the learning is stored in a memory (not shown) of the straight traveling state determination device 1 as a correction value due to variations in tire diameter. By doing so, the straight traveling state determination device 1 can correct the actually measured speed difference by the correction value of the speed difference stored in the memory when performing the actual straight traveling state determination. . That is, the straight traveling state determination device 1 subtracts or adds the correction value to the speed difference calculated from each wheel rotational speed (VFR, VFL, VRR, VRL) when actually determining the straight traveling state. To find the corrected speed difference. Then, the straight traveling state determination device 1 determines the straight traveling state of the vehicle C based on the corrected speed difference. Accordingly, it is possible to determine the straight traveling state in a state where the variation in the tire diameter is corrected.
[0023]
In the above example, the case where the steady running at the time of learning is determined using the parameters of the yaw rate and the lateral acceleration has been described. However, the present invention is not limited to this, and the vehicle speed condition, wheel Rotational speed fluctuation conditions, slip ratio fluctuation conditions, yaw rate conditions, yaw rate fluctuation conditions, lateral acceleration conditions, lateral acceleration fluctuation conditions, longitudinal acceleration conditions, longitudinal acceleration fluctuation conditions, rough road conditions, braking conditions, ABS control conditions Various parameters such as the F / S condition and the drive wheel torque condition can be obtained and compared with the respective threshold values to determine the steady running.
[0024]
FIG. 2 is a block diagram showing a configuration of the vehicle straight traveling state determination device in the present embodiment. As shown in FIG. 2, the straight travel state determination device 1 includes a left and right wheel rotational speed difference calculation unit 11, a steady travel state determination unit 12, a learned value calculation unit 13, a learned value storage unit 14, and a straight travel state determination unit 15. It is the composition provided with. Then, the front wheel right wheel rotation speed VFR, the front wheel left wheel rotation speed VFL, the rear wheel right wheel rotation speed VRR, and the rear wheel left wheel rotation speed VRL obtained by the ABS wheel speed sensor are supplied to the left and right wheel rotation speed difference calculation means 11. The system configuration is such that the learning switch signal GS is input to the steady running state determination means 12 and the learning value calculation means 13.
[0025]
The left and right wheel rotational speed difference calculating means 11 calculates the front wheel left and right wheel rotational speed difference ΔVF from the difference between the front wheel right wheel rotational speed VFR and the front wheel left wheel rotational speed VFL, and the rear wheel right wheel rotational speed VRR and the rear wheel left wheel. A rear wheel left / right wheel rotation speed difference ΔVR is calculated based on a difference from the rotation speed VRL.
When the learning switch signal GS instructing the start of learning is input, the steady running state determination means 12 has a front wheel left / right wheel rotation speed difference ΔVF and a rear wheel left / right wheel rotation speed difference ΔVR calculated by the left / right wheel rotation speed difference calculation means 11. Based on the yaw rate and lateral acceleration obtained from the above, the vehicle C has a function of determining whether or not the vehicle C is traveling in a straight line in a straight traveling state.
[0026]
The learning value calculation means 13 is input from the left and right wheel rotational speed difference calculation means 11 when the learning switch signal GS instructing the start of learning is input and when it is determined that the vehicle C is traveling in a straight line state. The front wheel left and right wheel rotation speed difference ΔVF and the rear wheel left and right wheel rotation speed difference ΔVR are learned over a predetermined time, and the front wheel left and right wheel rotation speed difference ratio learning value ΔVFrG for correcting the variation in tire diameter in each wheel and the rear A function of calculating a wheel left / right wheel rotation speed difference ratio learning value ΔVRrG is provided.
[0027]
The learning value storage unit 14 has a function of storing the front wheel left and right wheel rotation speed difference ratio learning value ΔVFrG and the rear wheel left and right wheel rotation speed difference ratio learning value ΔVRrG acquired from the learning value calculation unit 13.
[0028]
When the learning switch signal GS is interrupted, the straight traveling state determination means 15 learns the front wheel left / right wheel rotation speed difference ΔVF and the rear wheel left / right wheel rotation speed difference ΔVR acquired from the left / right wheel rotation speed difference calculation means 11 and learning. Based on the front wheel left and right wheel rotational speed difference ratio learned value ΔVFrG and the rear wheel left and right wheel rotational speed difference ratio learned value ΔVRrG acquired from the value storage means 14, the corrected front wheel left and right wheel rotational speed difference ΔVFR ′ and the corrected rear wheel left and right The wheel rotational speed difference ΔVR ′ is calculated, and the straight running state of the vehicle C is determined based on the calculated value.
[0029]
Next, the operation of the straight traveling state determination device for vehicle C in FIG. 2 will be described. When the learning switch (SW in FIG. 1) is turned on to perform initial learning when the vehicle C is traveling, the learning switch signal GS is input to the steady traveling state determination means 12 and the learning value calculation means 13 to start learning. When it is determined by the yaw rate or lateral acceleration of the steady running state judging means 12 that the vehicle is running straight in the straight running state, the learning value computing means 13 causes the front wheel left and right wheel rotational speed difference ΔVF and the rear wheel left and right wheel rotation. A learning value for learning the speed difference ΔVR over a predetermined time and correcting a variation in tire diameter in each wheel (that is, a front wheel left / right wheel rotation speed difference ratio learning value ΔVFrG and a rear wheel left / right wheel rotation speed difference ratio learning) The value ΔVRrG) is calculated. The front wheel left and right wheel rotational speed difference ratio learned value ΔVFrG and the rear wheel left and right wheel rotational speed difference ratio learned value ΔVRrG calculated in this way are stored in the learning storage means 14.
[0030]
Next, when actually determining the straight traveling state of the vehicle C, the learning switch (SW in FIG. 1) is turned off and the learning switch signal GS is cut off, so that the steady traveling state determination means 12 and the learning value calculation means 13 The learning function is stopped. Then, the straight traveling state determination means 15 acquires the front wheel left and right wheel rotation speed difference ΔVF and the rear wheel left and right wheel rotation speed difference ΔVR from the left and right wheel rotation speed difference calculation means 11, and the front wheel left and right wheel rotation speed from the learning value storage means 14. A difference ratio learning value ΔVFrG and a rear wheel left / right wheel rotation speed difference ratio learning value ΔVRrG are acquired. Further, the straight traveling state determining means 15 calculates the corrected front wheel left and right wheel rotational speed difference ΔVFR ′ and the corrected rear wheel left and right wheel rotational speed difference ΔVR ′, and the straight traveling state determining means 15 calculates the straight traveling state of the vehicle C. Make a decision. Accordingly, it is possible to accurately determine the straight traveling state with the tire diameter variation corrected.
The learning switch SW can be turned off manually, but here, it is assumed that the learning switch SW is automatically turned off after a predetermined time has elapsed.
[0031]
Next, the learning value calculation logic and the straight traveling state determination logic in the straight traveling state determination device of the present invention will be described. FIG. 3 is a flowchart showing the flow of the learning value calculation logic and the straight traveling state determination logic in the straight traveling state determination device of the present invention. The straight traveling state determination device 1 includes a learning value calculation unit 2, a learning value storage unit 3, and a straight traveling state determination calculation unit 4. 3 is compared with FIG. 2, the learning value calculation unit 2 of FIG. 3 forms the left and right wheel rotational speed difference calculation unit 11 and the learning value calculation unit 13 of FIG. 2, and the learning value storage unit of FIG. 3 constitutes the learning value storage means 14 of FIG. 2, and the straight traveling state determination calculation section 4 of FIG. 3 constitutes the straight traveling state determination means of FIG. 2 is omitted in FIG. 3 because it is not directly related to the calculation logic performed by the learning value calculation unit 3 in FIG.
[0032]
Further, the straight traveling state determination device 1 in FIG. 3 includes a front wheel right wheel rotation speed VFR, a front wheel left wheel rotation speed VFL, a rear wheel right wheel rotation speed VRR, and a rear wheel left wheel rotation speed detected by a wheel speed sensor (not shown). The system configuration is such that a VRL and a vehicle speed VV are input and a learning switch signal GS for starting learning for correcting initial variations in tires is input. The learning switch signal GS is input when a learning switch (not shown) (that is, the learning switch SW in FIG. 1) is turned on by the driver's judgment.
[0033]
Next, the flow of arithmetic logic in FIG. 3 will be described. First, after the tire pressures of the four wheels are set to the prescribed values, the learning switch signal SW is input in the running state. Thereby, the initial learning for correcting the variation in the tire diameter in the straight traveling state determination device 1 is started. Then, in the calculation 1 block, a front wheel left / right wheel rotation speed difference ΔVF is obtained from the difference between the front wheel right wheel rotation speed VFR and the front wheel left wheel rotation speed VFL. That is, ΔVF = VFR−VFL is calculated. Similarly, a rear wheel left / right wheel rotation speed difference ΔVR is obtained from the difference between the rear wheel right wheel rotation speed VRR and the rear wheel left wheel rotation speed VRL. That is, ΔVR = VRR−VRL is calculated.
[0034]
Further, in the calculation 2 block, the front wheel left / right wheel rotation speed difference ΔVF is divided by the vehicle speed VV to obtain the front wheel left / right wheel rotation speed difference ratio ΔVFr. That is, ΔVFr = ΔVF / VV is calculated. Similarly, the rear wheel left and right wheel rotational speed difference ratio ΔVRr is obtained by dividing the rear wheel left and right wheel rotational speed difference ΔVR by the vehicle speed VV. That is, ΔVRr = ΔVR / VV is calculated. Various formulas for calculating the vehicle speed VV are used depending on the case. Here, VV = (VRR + VRL) / 2 is calculated as an example. That is, in this case, the vehicle speed VV is an average value of the rear wheel right wheel rotation speed VRR and the rear wheel left wheel rotation speed VRL.
[0035]
The front wheel left / right wheel rotation speed difference ratio ΔVFr and the rear wheel left / right wheel rotation speed difference ratio ΔVRr obtained in the block of calculation 2 are, for example, the respective wheel rotation speeds detected every 10 ms (VFR, VFL, VRR, VRL). Since it is instantaneous data calculated based on the data, there are excessively straight parts and turning parts. For this reason, it is necessary to consider the data calculated over a predetermined time as moving average and to regard the data as traveling straight. Specifically, it is determined as data for straight running by moving and averaging values sampled and calculated over a period of 2 to 3 minutes.
[0036]
Therefore, in the block of calculation 3, the front wheel left and right wheel rotational speed difference ratio ΔVFr sampled and calculated over a predetermined time T is integrated to obtain a front wheel left and right wheel rotational speed difference ratio integrated value ΣΔVFr. Similarly, the rear wheel left and right wheel rotational speed difference ratio ΔVRr calculated by sampling over a predetermined time T is integrated to obtain a rear wheel left and right wheel rotational speed difference ratio integrated value ΣΔVRr. Then, in the block of calculation 4, the front wheel left and right wheel rotational speed difference ratio integrated value ΣΔVFr is divided by the predetermined time T to obtain the front wheel left and right wheel rotational speed difference ratio average value ΔVFrAV. That is, ΔVFrAV = ΣΔVFr / T is calculated. Similarly, the rear wheel left and right wheel rotational speed difference ratio integrated value ΣΔVRr is divided by a predetermined time T to obtain the rear wheel left and right wheel rotational speed difference ratio average value ΔVRrAV. That is, ΔVRrAV = ΣΔVRr / T is calculated.
[0037]
Further, in the block of calculation 5, the front wheel left and right wheel rotation speed difference ratio average value ΔVFrAV is multiplied by a predetermined coefficient to obtain a front wheel left and right wheel rotation speed difference ratio learning value ΔVFrG, and the rear wheel left and right wheel rotation speed difference ratio average value ΔVRrAV is obtained. Multiply a predetermined coefficient to obtain a rear wheel left and right wheel rotational speed difference ratio learned value ΔVRrG, and learn these learning values (front wheel left and right wheel rotational speed difference ratio learned value ΔVFrG, rear wheel left and right wheel rotational speed difference ratio learned value ΔVRrG). It is recorded in the value storage unit 3. As a result, the initial learning in the straight traveling state determination is finished, so that the learning switch signal GS is cut off when the driver turns off the learning switch SW (see FIG. 1) (not shown), and the calculation processing in the learning calculation unit 2 ends. In other words, the front wheel left and right wheel rotational speed difference ratio learning value ΔVFrG recorded in the learning value storage unit 3 is a front wheel left and right wheel learning value used as correction data on the front wheel side, and the rear wheel left and right wheel learning values recorded in the learning value storage unit 3 The wheel rotational speed difference ratio learning value ΔVRrG is a rear wheel left / right wheel learning value used as rear wheel correction data.
[0038]
Next, when the straight traveling state determination is performed while the vehicle C is traveling with the learning switch SW (see FIG. 1) turned off, the straight traveling state determination calculating unit 4 determines that the front wheel right wheel rotational speed VFR and the front wheel left The front wheel right / left wheel rotation speed difference ΔVF obtained from the difference between the wheel rotation speeds VFL and the rear wheel left / right wheel rotation speed difference ΔVR obtained from the difference between the rear wheel right wheel rotation speed VRR and the rear wheel left wheel rotation speed VRL are input. Further, the straight traveling state determination calculation unit 4 receives the front wheel left and right wheel rotation speed difference ratio learning value (front wheel left and right wheel learning value) ΔVFrG and the rear wheel left and right wheel rotation speed difference ratio learning value (rear wheel left and right wheels) from the learning value storage unit 3. Learning value) ΔVRrG is acquired. Then, the corrected front wheel left and right wheel rotational speed difference ΔVF ′ is obtained by correcting the front wheel left and right wheel rotational speed difference ΔVF by the front wheel left and right wheel rotational speed difference ratio learned value (front wheel left and right wheel learned value) ΔVFrG. Similarly, the corrected rear wheel left and right wheel rotational speed difference ΔVR ′ is obtained by correcting the rear wheel left and right wheel rotational speed difference ΔVR by the rear wheel left and right wheel rotational speed difference ratio learned value (rear wheel left and right wheel learned value) ΔVRrG.
[0039]
That is, the corrected front wheel left and right wheel rotational speed difference ΔVF ′ is obtained by the equation (1), and the corrected rear wheel left and right wheel rotational speed difference ΔVR ′ is obtained by the equation (2).
ΔVF ′ = ΔVF−ΔVFrG × VV (1)
ΔVR ′ = ΔVR−ΔVRrG × VV (2)
[0040]
In this way, when actually determining the straight traveling state, the front wheel left and right wheel rotational speed difference ΔVF and the rear wheel left and right wheel rotational speed difference ΔVR are corrected by the learned value that has been learned in advance. Accurate straight running state determination can be performed by correcting initial variation and temporal variation. Accordingly, it is possible to detect a decrease in tire air pressure with high accuracy.
[0041]
Next, the flow of the straight traveling state determination process will be described based on the correction by the learning value obtained by learning using the flowchart.
FIG. 4 is a flowchart showing the flow of the learning process and the straight traveling state determination process in the straight traveling state determination device 1 of the present embodiment. First, when the learning switch SW is turned on, the steady running state determination means 12 determines the stability of the vehicle C in the straight running state. For this purpose, the front wheel right wheel rotation speed VFR, the front wheel left wheel rotation speed VFL, the rear wheel right wheel rotation speed VRR, and the rear wheel left wheel rotation speed VRL are converted into the steady running state determination means via the left and right wheel rotation speed difference calculation means 11. The steady running state determination device 12 calculates the parameter indicating the straight running state of the vehicle based on the inputted wheel rotational speeds (VFR, VFL, VRR, VRL) (step S1). . Then, based on the parameter, it is determined whether or not the vehicle is in a stable straight traveling state. Here, examples of parameters include a front wheel yaw rate obtained based on the front wheel left and right wheel rotational speed difference ΔVF and a rear wheel yaw rate obtained based on the rear wheel left and right wheel rotational speed difference ΔVR. Here, it is determined whether or not the vehicle C is in a steady running state by comparing these values with a predetermined threshold (step S2).
[0042]
Here, when the vehicle C is not in a steady running state, that is, when the vehicle C is turning (No in step S2), the correction value learning process is not performed and the straight running stability time is counted. The counter to be cleared is cleared (step S3).
On the other hand, when the vehicle C is in the steady running state (Yes in step S2), the correction value learning process is started. First, for example, the rotational speeds (VFR, VFL, VRR, VRL) of each wheel are sampled every 10 ms (step S4), and these are input to the left and right wheel rotational speed difference calculating means 11 and the front wheel left and right wheel rotational speed difference ΔVF. Is obtained (step S5). Next, the front wheel left and right wheel rotation speed difference ΔVF is divided by the vehicle speed VV (step S5), and the front wheel left and right wheel rotation speed difference ratio ΔVFr is calculated (step S6). Subsequently, an addition operation (ΣΔVFr) is executed for the front wheel left and right wheel rotational speed difference ratio ΔVFr (step S7). The same processing is performed for the left and right rear wheels, and the same addition operation (ΣΔVRr) is executed (steps S4 to S7).
[0043]
Next, in order to perform moving average processing, it is determined whether or not the number of times of the sum operation has reached a specified number (step S8). Here, when the number of addition operations has not reached the prescribed number (in the case of No in step S8), the counter is incremented by 1 (step S9), and this processing flow is once ended. However, since the processing flow of FIG. 4 is executed every 10 ms, the processing of step S4 to step S7 is repeated until the number of additions reaches a specified number. When the number of addition calculations reaches a specified number (Yes in step S8), the added value (ΣΔVFr) of the front wheel right and left wheel rotational speed difference ΔVFr obtained by the specified number of calculations is divided by the specified number of times. The left and right wheel rotational speed difference average value ΔVFrAv is calculated (step S10). Similarly, the rear wheel left and right wheel rotational speed difference average value ΔVRrAv is calculated by dividing the added value (ΣΔVRr) of the rear wheel left and right wheel rotational speed difference ΔVRr by the specified number of times (step S10).
[0044]
Next, the end of the correction value learning process is determined based on whether or not the learning switch SW is turned off (step S11). If the correction value learning process has not been completed (No in step S11), the front wheel left and right wheel rotational speed difference ratio average value ΔVFrAv and the rear wheel left and right wheel rotational speed difference ratio average value ΔVRrAv are corrected. The offset learning value is stored in the memory (step S12), and the correction value learning process is terminated.
On the other hand, when the correction value learning process has already been completed in step S11 (Yes in step S11), the offset learned values ΔVFrAv and ΔVRrAv are used in the equations (1) and (2), The corrected front wheel left / right wheel rotational speed difference ΔVF ′ and the corrected rear wheel left / right wheel rotational speed difference ΔVR ′ can be calculated (step S13).
[0045]
It is determined whether or not the vehicle C is traveling straight from the corrected front wheel left and right wheel rotational speed difference ΔVF ′ and the corrected rear wheel left and right wheel rotational speed difference ΔVR ′. That is, if the corrected front wheel left / right wheel rotational speed difference ΔVF ′ and the corrected rear wheel left / right wheel rotational speed difference ΔVR ′ are equal to or less than a predetermined value, it is determined that the vehicle is traveling straight, and the corrected front wheel left / right wheel rotational speed difference ΔVF ′ If the corrected rear wheel left and right wheel rotational speed difference ΔVR ′ is equal to or greater than a predetermined value, it is determined that the vehicle is turning (step S14). If it is determined that the vehicle is traveling straight ahead (Yes in step S14), a straight traveling flag is set (step S15). If it is determined that the vehicle is not in the straight traveling state (No in step S15), the straight traveling flag is reset (step S16). Accordingly, if the straight traveling flag is set, it can be determined that the vehicle C is in the straight traveling state, and therefore, for example, a decrease in tire air pressure can be immediately detected.
[0046]
The embodiment described above is an example for explaining the present invention, and the present invention is not limited to the embodiment described above, and various modifications can be made within the scope of the gist of the invention. In the above-described embodiment, the case has been described in which each wheel rotation speed is detected using the ABS wheel speed sensor to determine the straight traveling state of C. However, the present invention is not limited to this. For example, a wheel speed sensor different from that for ABS may be used, and it goes without saying that the straight traveling state determination may be performed in combination with another sensor such as a yaw rate sensor or an acceleration sensor.
[0047]
【The invention's effect】
As described above, according to the vehicle straight traveling state determination device of the present invention, the rotation of the left and right wheels caused by the initial tire diameter variation at the time of tire manufacture, tire diameter variation due to tire wear, air pressure adjustment deviation, etc. The speed difference is determined by learning during the initial period of actual driving of the vehicle. After that, when the vehicle actually travels and makes a straight traveling state determination, the speed difference between the wheels is corrected by the learned value. As a result, variations in the tire diameter are compensated, and an accurate straight running state determination can be performed. Further, by using the speed difference between the wheels corrected in this way, the accuracy of the yaw rate and the lateral acceleration can be further improved.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a vehicle equipped with a vehicle straight traveling state determination device according to the present invention.
FIG. 2 is a block diagram illustrating a configuration of a straight traveling state determination device for a vehicle according to the present invention.
FIG. 3 is a flowchart showing the flow of learning value calculation logic and straight traveling state determination logic in the straight traveling state determination device of the present invention.
FIG. 4 is a flowchart showing a flow of learning processing and straight traveling state determination processing in the straight traveling state determination device of the present invention.
[Explanation of symbols]
1 Straight running state determination device
2 Learning value calculator
3 Learning value storage
4 Straight running state determination calculation unit
11 Left and right wheel rotation speed difference calculation means
12 Steady running state determination means
13 Learning value calculation means
14 Learning value storage means
15 Straight running state determination means
SW learning switch
VFR Front wheel right wheel rotation speed
VFL Front wheel left wheel rotation speed
VRR Rear wheel right wheel rotation speed
VRL Rear wheel left wheel rotation speed
VV vehicle speed
ΔVF Front wheel left and right wheel rotation speed difference
ΔVR Rear wheel left and right wheel rotation speed difference
ΔVF 'Corrected front wheel left and right wheel rotation speed difference
ΔVR 'Corrected rear wheel left and right wheel rotational speed difference
GS learning switch signal
ΔVFrG Front wheel left and right wheel rotational speed difference ratio learning value (front wheel left and right wheel learning value)
ΔVRrG Rear wheel left and right wheel rotational speed difference ratio learning value (rear wheel left and right wheel learning value)

Claims

A vehicle straight traveling state determination device for determining a straight traveling state of a vehicle based on a rotational speed of each wheel in a four-wheel vehicle,
The speed difference of the rotational speed of each wheel caused by the variation in the tire diameter is obtained by learning in advance, and the speed difference of the rotational speed of each wheel obtained by the learning is used as a learning value for correction,
The speed difference between the rotational speeds of the wheels obtained when the vehicle travels is corrected by the learning value,
A straight traveling state determination device for a vehicle, wherein the straight traveling state of the vehicle is determined based on the corrected rotational speed difference of each wheel.

A vehicle straight traveling state determination device for determining a straight traveling state of a vehicle based on a rotational speed of each wheel in a four-wheel vehicle,
Left and right wheel rotation speed difference calculating means for calculating the rotation speed of each wheel to obtain a front wheel left and right wheel rotation speed difference and a rear wheel left and right wheel rotation speed difference;
Switch means for instructing learning of a correction value for correcting the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference;
When the switch means is conducting, the front wheel left and right wheel rotation speed difference and the rear wheel left and right wheel rotation speed difference are acquired over a predetermined time, and the front wheel left and right wheel rotation speed difference and the rear wheel left and right wheel rotation are obtained. Learning value calculation means for calculating a speed difference to obtain a front wheel left and right wheel rotation speed difference ratio learning value and a rear wheel left and right wheel rotation speed difference ratio learning value;
Learning value storage means for storing the front wheel left and right wheel rotation speed difference ratio learning value and the rear wheel left and right wheel rotation speed difference ratio learning value;
When the switch means is shut off, the front wheel left and right wheel rotational speed difference and the rear wheel left and right wheel rotational speed difference are stored in the learned value storage means and the front wheel left and right wheel rotational speed difference ratio learned value and the rear wheel are stored. Straight running that corrects with the left and right wheel rotational speed difference ratio learning value and determines the straight running state of the vehicle based on the corrected front wheel left and right wheel rotational speed difference and the corrected rear wheel left and right wheel rotational speed difference obtained by the correction State determination means;
A straight running state determination device for a vehicle, comprising:

The learning value calculation means includes
Dividing the front wheel left and right wheel rotation speed difference and the rear wheel left and right wheel rotation speed difference by the vehicle speed of the vehicle to calculate the front wheel left and right wheel rotation speed difference ratio and the rear wheel left and right wheel rotation speed difference ratio;
The front wheel left and right wheel rotational speed difference ratio ratio and the rear wheel left and right wheel rotational speed difference ratio that are calculated are averaged over a predetermined time, respectively, to learn the front wheel left and right wheel rotational speed difference ratio learning value and the rear wheel. 3. The straight traveling state determination device for a vehicle according to claim 2, wherein a learning value for a difference between left and right wheel rotational speeds is calculated.

The front wheel left and right wheel rotational speed difference is ΔVF, the rear wheel left and right wheel rotational speed difference is ΔVR, the vehicle speed is VV, the front wheel left and right wheel rotational speed difference ratio learning value is ΔVFrG, and the rear wheel left and right wheel rotational speed difference. When the learning value ΔVRrG is used,
The corrected front wheel left and right wheel rotational speed difference ΔVF ′ is:
ΔVF ′ = ΔVF−ΔVFrG × VV
The corrected rear wheel left and right wheel rotational speed difference ΔVR ′ is:
The straight traveling state determination device for a vehicle according to claim 4, wherein ΔVR ′ = ΔVR−ΔVRrG × VV.

5. The vehicle according to claim 1, wherein the rotational speed of each of the wheels is measured by a wheel speed sensor provided in an ABS (Anti-lock Break System). Straight running state determination device.