# US 8,540,258 B2 · Rack assist type electric power steering apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,540,258 B2 - Document ID: US8540258B2 - Status: Granted - Kind: B2 - Application number: 12/956,837 - Filed: 2010-11-30 - Published: 2011-06-02 - Granted: 2013-09-24 - Earliest claimed: 2009-11-30 - Assignees: Mando Corporation - Applicants: Hong Yong Bae; Joo Namgung; Hee Kwon Jo - Inventors: Hong Yong Bae; Joo Namgung; Hee Kwon Jo - Web page: https://patentgrep.com/patent/US8540258B2 ## CPC - B62D 7/226: {acting on the steering gear} - B62D 5/0448: {Ball nuts} - F16C 27/066: {Ball or roller bearings} - F16H 25/24: Elements essential to such mechanisms, e.g. screws, nuts (F16H25/22 takes precedence) - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) - F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS - F16H: GEARING ## Abstract A rack-assist type electric power steering apparatus, in which when a ball nut slides a rack bar while rotating, a vibration and a noise in the axis direction and the radial direction, generated from the rack bar and a rack housing, are absorbed. This facilitates the operation of the ball nut and the rack bar, and reduces the vibration and the noise, thereby resulting in an effect for providing a comfortable steering feeling to a driver. ## Claims ### Claim 1 A rack-assist type electric power steering apparatus comprising: a ball nut which is rotated while being combined with a rack bar through a ball, thereby sliding the rack bar; a bearing which is mounted on an outer circumferential surface of the ball nut to support rotation; a connecting ring combined between an outer wheel of the bearing and a rack housing; and an axial damper which is combined at both sides of the connecting ring and is provided with lateral side projections protruding in a direction of a central axis of the rack bar, wherein the lateral side projections comprise a number of first side projections, and a number of second side projections, and wherein the connecting ring has a radial projection, and the axial damper is combined at both sides of the projection. ### Claim 2 (depends on 1) The rack-assist type electric power steering apparatus as claimed in claim 1, wherein between an outer circumferential surface of a projection of the connecting ring, and the rack housing, a radial damper is combined. ### Claim 3 (depends on 1) The rack-assist type electric power steering apparatus as claimed in claim 1, wherein the first side projections have outer lateral surfaces tightly fitted in the rack housing, and the second side projections have outer lateral surfaces spaced apart from the rack housing, wherein the first side projections and the second side projections are formed with a height difference therebetween in an axis direction. ### Claim 4 (depends on 3) The rack-assist type electric power steering apparatus as claimed in claim 3, wherein the first side projections and the second side projections are alternately formed. ### Claim 5 A rack-assist type electric power steering apparatus comprising: a ball nut which is rotated while being combined with a rack bar through a ball, thereby sliding the rack bar; a bearing which is mounted on an outer circumferential surface of the ball nut to support rotation; a connecting ring combined between an outer wheel of the bearing and a rack housing; and an axial damper which is combined at both sides of the connecting ring and is provided with lateral side projections protruding in a direction of a central axis of the rack bar, wherein the lateral side projections comprise a number of first side projections, and a number of second side projections, wherein between an outer circumferential surface of a projection of the connecting ring, and the rack housing, a radial damper is combined, and wherein an inner circumferential surface of the radial damper is provided with a number of inner side projections which are spaced apart from each other. ### Claim 6 (depends on 2, 5) The rack-assist type electric power steering apparatus as claimed in claim 2 or 5, wherein an outer circumferential surface of the radial damper is provided with a number of outer side projections which are spaced apart from each other.