SEIZURE PREVENTION DEVICE FOR SLIDING PART BETWEEN CYLINDER BLOCK AND VALVE PLATE OF PISTON PUMP/MOTOR

PURPOSE:To make it possible to lubricate a sliding part between a valve plate and a cylinder block by communicating oil grooves formed near a port on the front face of the valve plate to a high pressure port through a valve subjected to switching control. CONSTITUTION:Oil grooves 12 are formed above and below the first port 8 on the front face 7a, facing a cylinder block 3, of a valve plate 7. And, a valve 15 is switched from its communication position 1 to its communication position II by means of a signal outputted from a controller 16 for the purpose of exciting a solenoid 15a so that the oil grooves 12 are communicated to a high pressure port 10 via the valve 15. Thus, high pressure oil is supplied in the oil grooves 12 so as to lubricate the sliding part between the valve plate 7 and the cylinder block 3. Accordingly, the maximum allowable number of revolution or the maximum allowable pressure can exceed those values assigned depending upon the materials of the cylinder block 3 and the valve plate 7.