US 6,464,034 B1Granted

Electrically powered steering device

AssigneeNtn Corporation

InventorsMasaaki Toda, Koji Tateishi, Isamu Yoshida, Kiyoshige Yamauchi, Morihisa Yoshioka

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Abstract

An electrically powered steering device comprises a ball screw mechanism for transmitting a steering force from a steering wheel to steerable vehicle wheels. The ball screw mechanism includes a rotary nut 11 having a nut body 11a in which a circulating passage 15 is formed so as to extend axially thereof, and end caps 14a and 14b secured respectively to opposite ends of the nut body 11a. Each of the end caps 14a and 14b has defined therein respective guideways 17a and 17b for balls 13 that communicate opposite ends of the circulating tunnel 14 with a ball rolling passage 12. The end caps 14a and 14b and the nut body 11a are made of a sintered alloy. The nut body 11a has an outer periphery of one end thereof that is axially progressively reduced in diameter to define a tapered surface.

Claims14

Dependent claims

An electrically powered steering device which comprises:

a housing;
a steering shaft drivingly connected with a steering mechanism for steering wheels and extending completely through the housing;
a motion translating mechanism for translating a rotary force exerted by a steering wheel into a force required to move the steering shaft in a direction axially of the steering shaft;
a ball screw mechanism including a ball screw shaft constituting a portion of the steering shaft, and a rotary nut;
and
an electric drive motor mounted at one end on an outer periphery of the rotary nut of the ball screw mechanism:
wherein said ball screw mechanism comprises the ball screw shaft having a spiral outer groove formed there around;
the rotary nut formed with a spiral inner groove confronting to and aligned with the spiral outer groove on the ball screw shaft;
a plurality of torque transmitting balls disposed in a series within a ball rolling guideway defined between the spiral outer groove on the ball screw shaft and the spiral inner groove in the rotary nut and for transmitting a force between the rotary nut and the steering shaft;
and
a rolling bearing mounted on an outer periphery of the rotary nut for rotatably supporting the rotary nut relative to the housing, and wherein the outer periphery of the rotary nut is formed integrally with a radially outwardly protruding positioning flange for positioning the rolling bearing mounted thereon;
and
wherein a ball circulating passage communicating with the ball rolling guideway at its respective opposite ends is formed in part in a nut body of the rotary nut and in part in at least one end cap secured to respective opposite ends of the nut body.

10 more elements

An electrically powered steering device which comprises:

a housing;
a steering shaft drivingly connected with a steering mechanism for steering wheels and extending completely through the housing;
a motion translating mechanism for translating a rotary force exerted by a steering wheel into a force required to move the steering shaft in a direction axially of the steering shaft;
a ball screw mechanism including a ball screw shaft constituting a portion of the steering shaft, and a rotary nut;
and
an electric drive motor mounted at one end on an outer periphery of the rotary nut of the ball screw mechanism:
wherein said ball screw mechanism comprises the ball screw shaft having a spiral outer groove formed there around;
the rotary nut formed with a spiral inner groove confronting to and aligned with the spiral outer groove on the ball screw shaft;
and
a plurality of torque transmitting balls disposed in a series within a ball rolling guideway defined between the spiral outer groove on the ball screw shaft and the spiral inner groove in the rotary nut and for transmitting a force between the rotary nut and the steering shaft;
wherein a ball circulating passage communicating with the ball rolling guideway at its respective opposite ends is formed in part in a nut body of the rotary nut and in part in at least one end cap secured to an end of the nut body;
and
wherein an outer periphery of one of opposite ends of the nut body forming a part of the rotary nut and having the spiral inner groove confronting to and aligned with the spiral outer groove around the ball screw shaft, and a circulating tunnel for the balls is formed as a tapered surface tapering axially inwardly, and
wherein a portion of an outer peripheral surface of the nut body that is continued from the tapered surface is formed into a cylindrical surface and wherein a knurled surface region for avoiding an arbitrary rotation is formed on the cylindrical surface and a portion of the tapered surface adjacent the cylindrical surface.

11 more elements

Dependencies are inferred from the claim text.