US 6,317,287 B1Granted

Motor with output shaft having lead screw portion and pre-load generating mechanism

AssigneeCopal Company Limited

InventorsTetsushi Yano, Ryuta Yamawaki, Toshio Sadamitsu, Yukinori Arai

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Abstract

A motor with a lead screw is provided with a pre-load generating member for canceling backlash in the axial direction, and the lead screw formed with a feed screw groove portion serves as the output shaft of the motor. The pre-load generating mechanism is constituted by a blind hole, a biasing member, and a movable member. The blind hole is formed concentrically in one end of the lead screw. The biasing member is inserted in the blind hole and has a stroke sufficient to generate a biasing force. The movable member is inserted in the blind hole next to the biasing member to receive the biasing force, and is held to be movable in the axial direction in the blind hole. Hence, the motor with a lead screw can be made short in the axial direction. The biasing member is set to have a sufficiently long stroke so that the stability of the pre-load generating member is maintained high, thereby eliminating backlash in the axial direction.

Claims11

Dependent claims

A motor, comprising:

a base portion,
an output shaft with integral lead screw wherein backlash is cancelled in an axial direction and wherein said lead screw is formed with a feed screw groove portion, said lead screw having a first end rotationally and axially supported by a first bearing which is supported by said base portion and an intermediate portion rotationally axially supported by a second bearing which is supported by said base portion,
an annular coil for generating a rotating magnetic field, said annular coil having a first end surface portion fixed to said base portion,
a permanent magnet located in an inner hole portion of said coil and magnetized to have multiple poles and fixed to said lead screw, and
pre-load generating means including:
a blind hole formed concentrically in a second end of said lead screw,
a coil spring inserted in said blind hole and having a stroke sufficient to generate a biasing force,
a rod-shaped member, formed with a spherical end face, is inserted in said blind hole abutted to said coil spring to be held and movable in the axial direction in said blind hole by said coil spring with the spherical end face partly projecting from said second end of said lead screw, and
a substantially flat lid member fixed to a second end surface portion of said annular coil so as to abut against said spherical end face.

6 more elements

A motor, comprising:

a base portion,
an output shaft with integral lead screw wherein backlash is cancelled in an axial direction and wherein said lead screw is formed with a feed screw groove portion, said lead screw having first and second ends,
means, supported by said base portion, for rotationally and axially supporting said first end of said lead screw,
a coil having a first end surface portion fixed to said base portion,
a permanent magnet located in an inner hole portion of said coil and fixed to said lead screw,
pre-load generating means including:
a blind hole formed concentrically in a second end of said lead screw,
a biasing member inserted in said blind hole and having a stroke sufficient to generate a biasing force,
a rod-shaped member, formed with a spherical end face, is inserted in said blind hole abutted said biasing member to receive the biasing force, said rod-shape member held to be movable in the axial direction in said blind hole, by the biasing member with the spherical end face partly projecting from said second end of said lead screw, and
a lid member which abuts against said spherical end face and is fixed to a second end surface portion of said coil, and
a bearing, supported by said lid member, for rotationally and axially supporting said second end of said lead screw.

8 more elements

Dependencies are inferred from the claim text.