To provide a ball screw device in which an inner peripheral rolling groove formed on an inner peripheral face of a nut is hardened without melting a corner portion, by inexpensive heat treatment, a manufacturing method of the ball screw device, and a steering device including the ball screw device.SOLUTION: In a ball screw device 40, an inner peripheral rolling groove 21a of a nut 21 includes a pitch circle diameter constant region Coa in which a pitch circle diameter is constant in a range between opening portions 41a, 42a of mounting holes 41, 42, and a pitch circle diameter gradual change region ChA in which the pitch circle diameter is gradually increased between both end portions of the pitch circle diameter constant region to each of the opening portions. At least the pitch circle diameter constant region in the pitch circle diameter constant region and the pitch circle diameter gradual change region excluding corner portions 41b, 42b at boundaries of the opening portions and the inner peripheral rolling groove, has surface hardness of a prescribed value or more, and each part of the boundary of each opening portion and the inner peripheral rolling groove has surface hardness less than the prescribed value.SELECTED DRAWING: Figure 8
【課題】ナットの内周面に形成された内周転動溝が、安価な熱処理によって角部を溶融させることなく硬化されたボールねじ装置、ボールねじ装置の製造方法及びボールねじ装置を備えたステアリング装置を提供する。【解決手段】ボールねじ装置40において、ナット21の内周転動溝21aは、取付孔41,42の開口部41a,42a間の範囲において、ピッチ円径が一定となるピッチ円径一定領域CoAと、ピッチ円径一定領域の両端部から各開口部までの間において、徐々にピッチ円径が大きくなるピッチ円径徐変領域ChAと、を備える。各開口部と内周転動溝との境界の角部41b,42bを除く、ピッチ円径一定領域及びピッチ円径徐変領域のうち、少なくともピッチ円径一定領域が所定値以上の表面硬度を備え、各開口部と内周転動溝との境界の各部は所定値未満の表面硬度を備える。【選択図】図8
BALL SCREW DEVICE, MANUFACTURING METHOD OF BALL SCREW DEVICE, AND STEERING DEVICE INCLUDING BALL SCREW DEVICE
ボールねじ装置、ボールねじ装置の製造方法及びボールねじ装置を備えたステアリング装置
2019-03-14
Patent
Electronic Resource
Japanese
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