JP2004009882A5 - - Google Patents

Claims (11)

A ball nut having a female screw groove formed on an inner peripheral surface thereof, a rack shaft disposed at an axial center of the ball nut and having a male screw groove opposed to the female screw groove formed on the outer peripheral surface; the female screw groove and the male screw; A ball screw mechanism comprising a plurality of circulating balls interposed between the grooves,
A steering gear case that houses the ball screw mechanism;
An electric motor disposed on a separate axis from the rack shaft and used for driving the ball nut mechanism;
In a rack assist type electric power steering apparatus having power transmission means for transmitting the rotational driving force of the electric motor to the ball nut,
An electric power steering apparatus, wherein the power transmission means includes a power transmission element arranged coaxially and in series with the ball nut and engaged with the ball nut.   The electric power according to claim 1, wherein the ball nut is supported by the steering gear case via a first bearing, and the power transmission element is supported by the steering gear case via a second bearing. Steering device.   3. The electric power steering apparatus according to claim 1, wherein the ball nut and the power transmission element are connected via a misalignment absorbing means.   The electric power steering apparatus according to claim 3, wherein the misalignment absorbing means is an elastic joint.   The electric power steering apparatus according to claim 3, wherein the misalignment absorbing means is an Oldham coupling.   The electric power steering apparatus according to any one of claims 1 to 5, wherein the ball nut and the power transmission element are connected via a torque limiter.   The electric power steering according to claim 6, wherein the torque limiter is a spring ring having a plurality of protrusions on a peripheral surface thereof, and is press-fitted between the ball nut and the power transmission element. apparatus.   3. The electric power steering apparatus according to claim 1, wherein the ball nut and the power transmission element are connected via a connecting means that is slidable in the axial direction.   The electric power steering apparatus according to claim 8, wherein the connecting means is a spline, a serration, or a key.   The electric power steering device according to any one of claims 1 to 9, wherein an elastic body is interposed between the ball nut and the steering gear case. A ball nut in which an internal thread groove is formed on an inner peripheral surface; a rack shaft that is disposed on an axial center of the ball nut and has an external thread groove facing the internal thread groove on the outer peripheral surface; and the internal thread groove and the external thread A ball screw mechanism comprising a plurality of circulating balls interposed between the grooves,
A steering gear case that houses the ball screw mechanism;
An electric motor that is arranged on a separate axis from the rack shaft and is used to drive the ball nut mechanism. And
Power transmission means for transmitting the rotational driving force of the electric motor to the ball nut;
In a rack assist type electric power steering device having
The power transmission means includes a drive element coupled to an electric motor and a driven element that transmits power from the drive element to the ball nut.
The electric power steering device according to claim 1, wherein the ball nut and the driven element are configured as separate parts.