Patent ID: 7487028

Claim:
A low-μ road evaluation device for controlling the distribution of power between the front and rear wheels of a four wheel drive vehicle comprising: slip rate calculating means for calculating a slip rate between a wheel of a vehicle and a road surface; low-μ information magnitude calculating means for calculating a low-μ information magnitude associated with a friction coefficient of said road surface, based on both of said slip rate and an acceleration operation magnitude derived from a throttle setting sensor in said vehicle; comparison evaluating means for comparing between said calculated low-μ information magnitude and a first preset threshold value; adding means for adding a value based on said low-μ information magnitude to a counter when said comparison evaluating means determines that said low-μ information magnitude exceeds said first preset threshold value; subtracting means for subtracting a predetermined value from the counter added to by said adding means when said comparison evaluating means determines that said low-μ information magnitude does not exceed said first preset threshold value; and low-μ road evaluating means for determining that there is a low-μ road when the counter calculated by said adding means or said subtracting means exceeds a second preset threshold value.