Plunger, hydraulic end and plunger pump

A hydraulic end of a plunger pump, comprising:

• a valve box, comprising a third end portion and a fourth end portion,
• wherein the valve box comprises a plunger chamber inside the valve box, the plunger chamber comprises a low pressure chamber, an alternating chamber and a high pressure chamber which are sequentially arranged, the low pressure chamber comprises a second opening at a position where the third end portion is located, the alternating chamber is communicated with the low pressure chamber, the high pressure chamber is communicated with the alternating chamber and located at a side of the alternating chamber away from the low pressure chamber, and the high pressure chamber comprises a third opening at a position where the fourth end portion is located;
• the valve box further comprises a second liquid inlet hole and a liquid outlet hole, the second liquid inlet hole passes through a sidewall of the valve box and is communicated with the low pressure chamber, the liquid outlet hole passes through a sidewall of the valve box and is communicated with the high pressure chamber;
• wherein the low pressure chamber, the alternating chamber and the high pressure chamber are sequentially arranged in a first direction;
• and
• wherein the hydraulic end further comprising:
• a first nut fixed at the second opening and comprising a second intermediate hole;
• and
• a plunger extending into the plunger chamber from the second intermediate hole and configured to reciprocate in the first direction,
• wherein the plunger comprises a plunger body, the plunger body comprises a flow channel inside the plunger body;
• a first liquid inlet hole on the plunger body and passing through a sidewall of the plunger body;
• and a first valve assembly, the plunger body comprises a first end portion and a second end portion, the flow channel extends from the first end portion to the second end portion, a part of the flow channel close to the first end portion is closed, a part of the flow channel close to the second end portion comprises a first opening, the first liquid inlet hole is communicated with the flow channel, and the first valve assembly is at the first opening, and is configured to allow fluid to flow out from the flow channel at the second end portion and prevent fluid from flowing back to the flow channel from outside, and
• the first liquid inlet hole is always in the low pressure chamber during the movement of the plunger.