Motor-driven power steering device

• US 20020112555A1
• Filed: 02/14/2002
• Published: 08/22/2002
• Est. Priority Date: 06/19/2000
• Status: Active Grant

• Current Assignee: NKS Company Limited
• Original Assignee: NKS Company Limited
• Inventors: Ohshima, Masamichi, Chikaraishi, Kazuo
• Granted Patent: US 6,805,017 B2
• Time in Patent Office: Days
• US Class Current: 74/388PS
• CPC Class Codes: B62D 5/0409 Electric motor acting on the steering column
• CPC Class Codes: B62D 5/043 characterised by clutch means between driving element, e.g. motor, and driven element, e.g. steering column or steering gear
• CPC Class Codes: F16D 1/0835 due to the elasticity of the ring or sleeve
• CPC Class Codes: F16D 7/021 with radially applied torque-limiting friction surfaces F16D7/022 takes precedence
• CPC Class Codes: F16H 1/16 comprising worm and worm-wheel
• CPC Class Codes: F16H 55/06 Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties coatings for lubrication F16H57/041; producing gear wheels from plastics or substances in a plastic state B29D15/00; heat treatment C21D9/32; electrolytic surface treatment C25D; heating by electromagnetic field H05B6/00
• CPC Class Codes: Y10T 74/19828 Worm

Abstract

An electric power steering apparatus can correspond to high output ability, and has a power transmission mechanism of an electric driving section capable of achieving predetermined slip torque in spite of change of operating temperature. Also, a resin gear for power transmission is formed by joining a core metal and a resin with strong bonding force, and has preferable heat-dissipation property. This joining is performed by way of chemical bond according to composite molding technique or adhesive.

Claims

1. An electrically power assisting steering apparatus provided with a torque limiter having a ring member for applying elastic force mounted between a worm wheel and an output shaft, being characterized in that said output shaft is made of iron material, a gear portion of said worm wheel is made of synthetic resin material, and a core metal portion of said worm wheel is made of metallic material whose specific gravity is small and coefficient of linear expansion is large with respect to said iron material, whereby limit torque of said torque limiter is set low under high temperature and high under low temperature.

2. An electrically power assisting steering apparatus provided with a worm wheel for transmitting driving force of a motor as auxiliary steering force together with a worm gear, being characterized in that said worm wheel is formed by joining a thin synthetic resin to an entire outer peripheral surface of a teeth portion of a gear-shaped core metal by way of chemical bond according to composite molding technique or adhesive.

3. An electrically power assisting steering apparatus according to claim 2, wherein said core metal is made of aluminum alloy or copper alloy.