The backpressure device comprises a backpressure
assembly and a hydraulic
assembly, the backpressure
assembly comprises an upper working table, an oil accumulator, an oil cylinder, a base plate, a guide column, a
piston and a force bearing plate, gaps exist between the two sides of the guide column and the upper working table, and the hydraulic assembly is arranged on the upper working table. The gap is communicated with the oil accumulator and the oil cavity, the lower portion of the guide column extends into the oil cavity and is connected with the
piston, the
piston is located in the oil cavity, and a force bearing plate is arranged below the piston. According to the technical scheme, an
oil film can be formed in the gap, once the piston is subjected to unbalance loading, the thickness of the
oil film changes, and pressure differences in opposite directions are formed on the two sides of the guide column, so that unbalance loading resisting torque is formed, unbalance loading of the piston is corrected, normal movement of the piston is guaranteed, and the unbalance loading resisting capacity of the backpressure device is improved. In addition, due to the fact that an
oil film is formed in the gap between the guide column and the upper
workbench, actual abrasion between the guide column and the upper
workbench is avoided under the action of the oil film, the service life of the backpressure device is prolonged, and the backpressure device is prevented from being damaged.