Unloading valve and combined valve type buffer cylinder

An unloading valve, comprising a valve body, a valve trim, a return spring, and a damping hole, wherein

• a valve orifice is formed in the valve body;
• the valve trim is fit and provided in the valve orifice;
• a driving chamber of the valve trim and a spring chamber of the valve trim are respectively formed at two ends of the valve orifice;
• the return spring is provided in the spring chamber and comprises a first end compressed to abut against a bottom of the spring chamber and a second end compressed to abut against a first end of the valve trim;
• under a pushing force of the return spring, a second end of the valve trim abuts against a bottom of the driving chamber;
• an unloading groove is formed in the valve trim;
• a first oil passage and a second oil passage communicate through the unloading groove and are arranged on the valve body;
• a third oil passage communicating with the driving chamber is formed in the valve body;
• the second oil passage communicates with the spring chamber;
• and in a non-unloading state, the unloading groove communicates with the first oil passage, and does not communicate with the second oil passage, the spring chamber and the driving chamber;
• the damping hole is formed in the valve trim, a guide sleeve, a cylinder bottom, or an oil conduit;
• and the driving chamber and the spring chamber communicate through the damping hole;
• the unloading valve is assembled on the guide sleeve, the cylinder bottom, or the oil conduit;
• and
• the unloading valve is a cartridge valve;
• the unloading valve further comprises a valve sleeve;
• the valve trim is fit and provided in the valve sleeve, and inserted into the valve body through the valve sleeve;
• a fifth oil passage is formed in the valve sleeve;
• and the fifth oil passage is configured to cooperate with the unloading groove to realize an unloading function of the unloading valve.