Ball screw device

Abstract

To provide a ball screw device which suppresses a variation of a no-resistance load value, and in which a piston hardly comes off therefrom.SOLUTION: A ball screw device of the present disclosure comprises a screw shaft, a nut, a plurality of balls, and a cylindrical body being a component for constituting a piston which is provided at one side with respect to the nut in an axial direction. The nut has an end face oriented to one side in the axial direction, an insertion part inserted into the cylindrical part, and a recessed face formed at an external peripheral face of the insertion part. The cylindrical body has a fitting part inserted with the insertion part, and fit to the insertion part, and a caulking part protruding to the inside of a radial direction rather than the fitting part, and intruding into the recessed face. The recessed face has a small diameter face smaller than the external peripheral face of the insertion part in a diameter, and extending in the axial direction at a cross section shape which is cut in the axial direction, and an inclined face extending to one side in the axial direction while being expanded in a diameter from one end part of the small diameter face in the axial direction, and the caulking part has an inclined wall part extending along the inclined face, and a linear wall part extending along the small diameter face.SELECTED DRAWING: Figure 4

Claims

1. Screw shaft and A nut that passes through the aforementioned screw shaft, A plurality of balls are arranged between the screw shaft and the nut, A component of the piston, comprising a cylindrical body extending in an axial direction parallel to the screw shaft and positioned relative to the nut in one of the axial directions, Equipped with, The aforementioned nut is The end face facing one direction in the axial direction, An insertion portion that protrudes from the end face in one direction in the axial direction and is inserted into the interior of the cylindrical body, A concave surface is provided on the outer circumferential surface of the insertion portion, which is recessed radially inward, It has, The cylindrical body is The insertion portion is inserted into the interior, and the fitting portion fits into the insertion portion, A crimping portion that protrudes radially inward from the aforementioned fitting portion and fits into the concave surface, It has, The aforementioned concave surface is The diameter is smaller than the outer circumferential surface of the insertion portion, and the cross-sectional shape when cut in the axial direction is a small-diameter surface that extends in the axial direction, An inclined surface extending in one direction in the axial direction from one end of the small diameter surface in the axial direction while increasing in diameter, It has, The crimping portion is, An inclined wall portion extending along the aforementioned inclined surface, A straight wall portion extending along the aforementioned small diameter surface, It has, The insertion portion is composed of a plurality of protrusions arranged circumferentially apart from each other, each having a concave surface on its outer surface. A notch is provided between two adjacent protrusions in the circumferential direction. The aforementioned fitting portion is, Multiple large-diameter wall portions are arranged spaced apart from each other in the circumferential direction, covering the outer periphery of the projection, and the crimping portion is provided on each of them. A plurality of small-diameter wall portions are arranged in the aforementioned notch and have a smaller diameter than the large-diameter wall portion, A plurality of radial wall portions extend radially inward from the circumferential end of the large-diameter wall portion, and the radially inward end connects to the circumferential end of the small-diameter wall portion, It has, The radial wall portion abuts against the projection portion from the circumferential direction, The crimping portion is located in the central part of the circumferential direction of the large-diameter wall portion. The circumferential length of the concave surface is longer than the circumferential length of the crimping portion. Ball screw device.

2. Screw shaft and A nut that passes through the aforementioned screw shaft, A plurality of balls are arranged between the screw shaft and the nut, A component of the piston, comprising a cylindrical body extending in an axial direction parallel to the screw shaft and positioned relative to the nut in one of the axial directions, Equipped with, The aforementioned nut is The end face facing one direction in the axial direction, An insertion portion that protrudes from the end face in one direction in the axial direction and is inserted into the interior of the cylindrical body, A concave surface is provided on the outer circumferential surface of the insertion portion, which is recessed radially inward, It has, The cylindrical body is The insertion portion is inserted into the interior, and the fitting portion fits into the insertion portion, A crimping portion that protrudes radially inward from the aforementioned fitting portion and fits into the concave surface, It has, The aforementioned concave surface is The diameter is smaller than the outer circumferential surface of the insertion portion, and the cross-sectional shape when cut in the axial direction is a small-diameter surface that extends in the axial direction, An inclined surface extending in one direction in the axial direction from one end of the small diameter surface in the axial direction while increasing in diameter, It has, The crimping portion is, An inclined wall portion extending along the aforementioned inclined surface, A straight wall portion extending along the aforementioned small diameter surface, It has, The insertion portion is composed of a plurality of protrusions arranged circumferentially apart from each other, each having a concave surface on its outer surface. A notch is provided between two adjacent protrusions in the circumferential direction. The aforementioned fitting portion is, Multiple large-diameter wall portions are arranged spaced apart from each other in the circumferential direction, covering the outer periphery of the projection, and the crimping portion is provided on each of them. A plurality of small-diameter wall portions are arranged in the aforementioned notch and have a smaller diameter than the large-diameter wall portion, A plurality of radial wall portions extend radially inward from the circumferential end of the large-diameter wall portion, and the radially inward end connects to the circumferential end of the small-diameter wall portion, It has, The radial wall portion abuts against the projection portion from the circumferential direction, The cylindrical body is positioned on one side in the axial direction from the fitting portion and has a cylindrical body whose outer surface faces the inner surface of the housing. Before forming the crimping portion on the cylindrical body, the cross-sectional shape of the cylindrical body and the cross-sectional shape of the fitting portion are the same. The cylindrical body is surrounded by the small-diameter wall portion and two radial wall portions connected to the circumferential ends of the small-diameter wall portion, and has a sliding groove that opens outward in the front radial direction. A guide protruding from the inner circumferential surface of the housing is inserted into the sliding groove. Ball screw device.

3. The cylindrical body is positioned on one side in the axial direction from the fitting portion and has a cylindrical body whose outer surface faces the inner surface of the housing. Before forming the crimping portion on the cylindrical body, the cross-sectional shape of the cylindrical body and the cross-sectional shape of the fitting portion are the same. The cylindrical body is surrounded by the small-diameter wall portion and two radial wall portions connected to the circumferential ends of the small-diameter wall portion, and has a sliding groove that opens outward in the front radial direction. A guide protruding from the inner circumferential surface of the housing is inserted into the sliding groove. The ball screw device according to claim 1.

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