A pump body assembly, comprising: an upper flange ; a lower flange ; a cylinder , arranged between the upper flange and the lower flange ; a sliding block structure , rotatably arranged inside the cylinder , the sliding block structure comprising a connecting portion and two sliding sub-blocks arranged on the connecting portion , and the two sliding sub-blocks and an inner wall surface of the cylinder forming a first sliding hole ; a piston , slidably arranged inside the first sliding hole , a variable volume cavity being formed between the piston and an inner wall of the cylinder , and the piston having a second sliding hole ; and a rotation shaft , wherein at least a portion of the rotation shaft is slidably arranged inside the second sliding hole , and a slide included angle is formed between a first sliding direction, in which the piston slides relative to the first sliding hole , and a second sliding direction, in which the rotation shaft slides relative to the second sliding hole ; at least one connecting portion , wherein the at least one connecting portion is provided with a first through hole and the rotation shaft passes through the first through hole ; a first connecting portion is arranged on the connecting portion ; a second connecting portion is arranged on the lower flange ; and the first connecting portion and the second connecting portion are nested and fit to connect the sliding block structure with the lower flange ; characterized in that the first connecting portion is the first through hole ; the second connecting portion is a position-limiting protrusion ; the position-limiting protrusion extends into the first through hole to enable the sliding block structure to pivot relative to the lower flange ; the position-limiting protrusion has a second through hole ; and the rotation shaft passes through the second through hole . an upper flange ; a lower flange ; a cylinder , arranged between the upper flange and the lower flange ; a sliding block structure , rotatably arranged inside the cylinder , the sliding block structure comprising a connecting portion and two sliding sub-blocks arranged on the connecting portion , and the two sliding sub-blocks and an inner wall surface of the cylinder forming a first sliding hole ; a piston , slidably arranged inside the first sliding hole , a variable volume cavity being formed between the piston and an inner wall of the cylinder , and the piston having a second sliding hole ; and a rotation shaft , wherein at least a portion of the rotation shaft is slidably arranged inside the second sliding hole , and a slide included angle is formed between a first sliding direction, in which the piston slides relative to the first sliding hole , and a second sliding direction, in which the rotation shaft slides relative to the second sliding hole ; at least one connecting portion , wherein the at least one connecting portion is provided with a first through hole and the rotation shaft passes through the first through hole ; a first connecting portion is arranged on the connecting portion ; a second connecting portion is arranged on the lower flange ; and the first connecting portion and the second connecting portion are nested and fit to connect the sliding block structure with the lower flange ; characterized in that the first connecting portion is the first through hole ; the second connecting portion is a position-limiting protrusion ; the position-limiting protrusion extends into the first through hole to enable the sliding block structure to pivot relative to the lower flange ; the position-limiting protrusion has a second through hole ; and the rotation shaft passes through the second through hole . <EOS>