ROAD SURFACE STATE DETECTION DEVICE AND POWER STEERING APPARATUS INCLUDING THE ROAD SURFACE STATE DETECTION DEVICE

To make it possible to determine road surface conditions corresponding to various operations and driving conditions with higher accuracy.SOLUTION: A road surface state detection device 80 includes: a steering angle detection section 51A for detecting a steering angle θs of a steering wheel 21; a steering speed detection section 52 for detecting a steering speed; an axial force detection section 58 for detecting axial force fr of a turning shaft 41 of a turning section 24 for turning wheels 23 and 23; a yaw rate detection section 63 for detecting a yaw rate Yr generated in a vehicle 10; a G detection section 62A for detecting lateral G and longitudinal G generated in the vehicle; a first road surface condition determination section 81 for determining the road surface condition of a road surface Rd with which the wheels 23 and 23 are in contact, on the basis of the value of the axial force fr with respect to the steering angle θs (and preferably a vehicle speed Vs); and a second road surface condition determination section 82A for determining the road surface condition of the road surface Rd with which the wheels 23 and 23 are in contact, on the basis of the value of the yaw rate Yr with respect to the steering angle θs, steering speed, lateral G, and longitudinal G.SELECTED DRAWING: Figure 9 【課題】多様な操作や運転状況に対応した路面状況を、より高精度に判断することができること。【解決手段】路面状態検出装置８０は、ステアリングホイール２１の操舵角θｓを検出する操舵角検出部５１Ａと、操舵速度を検出する操舵速検出部５２と、車輪２３，２３を転舵する転舵部２４の転舵軸４１の軸力ｆｒを検出する軸力検出部５８と、車両１０に発生したヨーレートＹｒを検出するヨーレート検出部６３と、車両に発生した横Ｇ及び前後Ｇを検出するＧ検出部６２Ａと、前記操舵角θｓ（及び好ましくは車速Ｖｓ）に対する前記軸力ｆｒの値に基づいて、前記車輪２３，２３が接している路面Ｒｄの路面状況を判断する第１の路面状況判断部８１と、前記操舵角θｓ、操舵速度、横Ｇ及び前後Ｇに対する前記ヨーレートＹｒの値に基づいて、前記車輪２３，２３が接している前記路面Ｒｄの路面状況を判断する第２の路面状況判断部８２Ａと、を備えている。【選択図】図９