To allow an oil droplet detection device to correctly detect oil droplets even when a light receiving quantity is reduced and when lubricating oils with different transparency are used.
A background measuring part 13 calculates the average value of signals output from an oil droplet sensor 11, and a threshold setting part 14 sets a threshold used for the judgement of the passing of oil droplets based on the average value. A first comparing circuit 15 compares output signal from the oil droplet sensor 11 with the threshold, and a threshold-exceeding duration time measuring part 16 measures the time for which the output signal exceeds the threshold, thus detecting droplets. When a light receiving part 11b in the oil droplet sensor 11 is stained, and when lubricating oils with different transparency are used, the average value of the output signals from the oil droplet sensor 11 varies, so that the threshold used for the determination of the passing of droplets is rationalized, and droplets can be correctly detected.
Katsumi Taguchi
Shinichi Mizuta
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