Swash-plate type piston pump

A swash-plate type piston pump, comprising:

• a cylinder block configured to be rotated with rotation of a driving shaft;
• a plurality of pistons accommodated in a plurality of cylinders provided in the cylinder block;
• a swash plate configured to reciprocate each of the plurality of pistons so that a volume chamber of each cylinder of the plurality of cylinders is expanded and/or contracted with the rotation of the cylinder block;
• a biasing-spring mechanism configured to bias the swash plate in a direction where a tilting angle of the swash plate becomes larger;
• a control pin including a first control pin and a second control pin that are arranged in series, the second control pin having a first end that engages the swash plate and a second end at which the first control pin is disposed, the control pin being configured to receive a load pressure of a pressure chamber, to drive the swash plate by pushing the swash plate by the first end of the second control pin so that the tilting angle of the swash plate becomes smaller;
• a discharge channel disposed in the casing and being configured to discharge the load pressure of the pressure chamber;
• a casing having an inside that is configured to accommodate the cylinder block, the plurality of pistons, the swash plate, the biasing-spring mechanism, and the first and second control pins;
• and
• a pin cylinder including a first pin cylinder and a second pin cylinder, each provided in the casing, wherein
• the first and second control pins are respectively slidably inserted into the first and second pin cylinders,
• the discharge channel has one end that directly opens to the inside of the casing and an other end that opens at all times in-a sliding gap defined between an outer peripheral surface of the first control pin and an inner peripheral surface of the first pin cylinder so that the load pressure of the pressure chamber is discharged from the discharge channel at all times.