The detailed working process of a hydraulic motor

The specific principle of a marine hydraulic motor:

Taking a small radial piston-type marine hydraulic motor as an example, let's explain how the motor converts hydraulic energy from a four-column hydraulic press into rotational mechanical energy for output. The basic principle of a Kawasaki marine hydraulic motor with a radial piston pump design is illustrated in Figure 4.23 (anime-style depiction for illustrative purposes). The swashplate 1 and the oil distribution plate 4 are fixed in position, while the hydraulic pistons 3 can move within the bores of the cylinder block 2. The centerline of the swashplate intersects the axis of the cylinder block at an angle δ. When high-pressure oil enters the piston bores of the cylinder block through the oil distribution plate's inlet windows, the pistons in the high-pressure chambers are forced out and press against the swashplate. The reaction force f exerted by the swashplate on the pistons is resolved into an axial force fx and a perpendicular force fy. The axial force fx balances the hydraulic force acting on the pistons, while the perpendicular force fy generates a torque that causes the cylinder block to rotate, driving the shaft 5. The total torque generated by the hydraulic motor's coupling is the sum of the torques produced by all the pistons in the high-pressure chambers, where r is the distribution radius of the pistons in the cylinder block, and θ is the angle between the i-th piston and the vertical axis of the cylinder block.

It can be seen that as the angle θ changes, the torque generated by each piston varies, resulting in a pulsating overall output torque from the hydraulic motor.

In principle, hydraulic pumps and hydraulic motors of the same design can be interchangeable. However, in general, an unmodified hydraulic pump cannot serve as a hydraulic motor. This is because, considering factors such as pressure balance and automatic compensation for gap sealing, the structures of the suction and discharge chambers in hydraulic pumps are mostly irregular and designed for unidirectional rotation only. In contrast, hydraulic motors typically require bidirectional rotation capabilities and, therefore, demand a symmetrical structure.