Patent ID: 7481500

Claim:
An operation-characteristic obtaining apparatus, comprising: an operation-characteristic obtaining portion which obtains, as an operation characteristic of an electromagnetic control valve which includes a coil and which is opened and closed according to at least a relationship between (a) an acting force corresponding to a difference of respective pressures of a working liquid on either side of the electromagnetic control valve and (b) an electromagnetic drive force corresponding to an electric current supplied to the coil, a relationship between (c) a valve switching current as an electric current that is supplied to the coil of the electromagnetic control valve at a time when the electromagnetic control valve is switched between a closed state thereof and an opened state thereof and (d) a difference at said time of the respective pressures on either side of the electromagnetic control valve; and a leakage detecting portion which detects, when the operation-characteristic obtaining portion obtains the operation characteristic of the electromagnetic control valve, whether the electromagnetic control valve has a leakage of the working liquid.