Hydraulic pump, hydraulic pump unit, and hydraulic driving unit

Abstract

A hydraulic pump can prevent breakage at a high pressure without providing a separate relief valve. A housing has a body side and a lid side that are divided by a surface perpendicular to a rotational axis of a hydraulic pump shaft. The lid-side housing is brought into oil-tight contact with the body-side housing by a spring. Contact between the body-side housing and the lid-side housing is maintained at a predetermined pressure corresponding to a maximum allowable pump hydraulic pressure.

1 . A hydraulic pump used in a hydraulic pump unit with a construction that at least a hydraulic pump and a hydraulic oil tank are integrated and a housing of said hydraulic pump is contained in the hydraulic oil tank, 
 wherein said housing is provided with a body side and a lid side divided by a surface perpendicular to a rotary shaft of the hydraulic pump, and this lid-side housing is brought into oil-tight contact with the body-side housing with a predetermined pressure corresponding to an allowable pump hydraulic pressure.    
   
   
       2 . The hydraulic pump according to  claim 1 , wherein said oil-tight contact with said predetermined pressure is realized by a spacer fitted between a mounting hole of said lid-side housing and a fastening bolt so as to achieve fastening and fixing of the fastening bolt to said body-side housing and a spring interposed between an underside of a head of the fastening bolt which has been fastened and fixed and said lid-side housing for generating said predetermined pressure.  
   
   
       3 . The hydraulic pump according to  claim 1 , wherein said oil-tight contact with said predetermined pressure is realized by a frame body fixed to said body-side housing and containing said lid-side housing, wherein said lid-side housing is capable of sliding in a direction perpendicular to said divided surface to allow oil leakage, and a spring interposed between the frame body and said lid-side housing for generating said predetermined pressure.  
   
   
       4 . The hydraulic pump according to  claim 1 , wherein said oil-tight contact with said predetermined pressure is realized by a lid-side housing constituted so that it is fixed to said body-side housing with a fastening bolt and comprised of an elastic body, a part of which is elastically deformed when said allowable hydraulic pressure is applied to said elastically deformable part.  
   
   
       5 . A hydraulic pump unit provided with the hydraulic pump in any one of  claims 1  to  4 .  
   
   
       6 . A hydraulic driving unit in which at least an electric motor for driving said hydraulic pump and a hydraulic actuator driven by hydraulic oil from said hydraulic pump are further integrated to the hydraulic pump unit in  claim 5.