| 摘要 |
PURPOSE:To enable easily to judge the internal leakage of a hydraulic cylinder by detecting the pressure at the head-side chamber and that at the rod-side chamber of a hydraulic cylinder so as to output an internal leakage signal when the pressure difference between the pressure at the head-side chamber and that at the rod-side chamber is a prescribed value or less. CONSTITUTION:Each of the pressures at the head-side chamber 2h and that at the rod-side chamber 2r of a hydraulic cylinder 2 is detected by pressure detectors 5h and 5r respectively. And the detected pressure signals are input into an input part 6, and, after they have been converted into a digital signal, the difference of both pressure signals is calculated in an arithmetic part 7 and the difference value thus obtained is compared with a prescribed value. In this case, if any abnormality exists in the piston packing of the hydraulic cylinder 2, the oil pressure in both chambers 2h and 2r becomes equal since oil in the head-side chamber 2h leaks into the rod-side chamber 2r. Accordingly, when the remainder after the detected value of pressure detector 5r is subtracted from that of pressure detector 5h is a prescribed value or less, an internal leakage signal is output from the arithmetic part 7 to an indicating part 8. |
