Cellulose-containing gear

Patent metadata

Field	Value
Publication number	US-11242913-B2
Application number	US-201917049910-A
Country	US
Kind code	B2
Filing date	Apr 22, 2019
Priority date	Apr 23, 2018
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

A gear is provided that has excellent continuous moldability for practical use, and both high slidability and high durability. The provided gear is a molded resin constructed of a resin composition comprising a thermoplastic resin (A) and cellulose nanofibers (B) with an average fiber diameter of 1000 nm or smaller, and having a number average molecular weight of the thermoplastic resin (A) in the range of 10,000 to 150,000, wherein a sliding surface of the gear with another gear teeth has an arithmetic mean surface roughness Sa of 3.0 μm or lower.

First claim

The invention claimed is:

1. A gear which is a molded resin constructed of a resin composition comprising a thermoplastic resin (A) and cellulose nanofibers (B) with an average fiber diameter of 1000 nm or smaller, wherein:
the gear has a roundness of 400 μm or smaller,
the thermoplastic resin (A) includes a polyamide resin, and
the resin composition has a thixotropic index of 2 to 10 at a temperature of 25° C. higher than the melting point of the thermoplastic resin (A).

2. The gear according to claim 1 , which is an EPS (electric power steering) gear.

3. The gear according to claim 1 , which is an injection molded article.

4. The gear according to claim 1 , which is a machined article.

5. The gear according to claim 4 , which is an article cut from a molded round bar.

6. A gear system comprising:
a gear mechanism constructed of a driven gear and a driving gear that engages with the driven gear, and
a driving source that drives the driving gear,

wherein the driven gear and/or the driving gear are gears according to claim 1 .

7. The gear system according to claim 6 , which is an EPS (electric power steering) gear system.

8. The gear system according to claim 6 , wherein:
the gear mechanism is a rack and pinion mechanism constructed of a rack and pinion, or a worm gear mechanism constructed of a worm and worm wheel, and
the pinion or worm wheel is a gear according to claim 1 .

9. The gear system according to claim 8 , wherein the pinion or worm wheel has a gear tooth total tooth depth/circular pitch ratio of 1.0 to 20.

10. The gear system according to claim 8 , wherein the pinion or worm wheel has a gear tooth total tooth depth/tooth width ratio of 1.0 to 3.0.

11. The gear system according to claim 6 , wherein:
the driven gear and the driving gear engage each other via grease, where the grease comprises:
a base oil containing 80 mass % or greater of at least one selected from the group consisting of mineral oils, poly α-olefin oils and alkylpolyphenyl ethers,
a thickener, and
3 to 10 mass % of a hydrocarbon-based wax with a melting point or softening point in the range of 70 to 130° C.

12. A gear system comprising:
a gear mechanism constructed of a driven gear and a driving gear that engages with the driven gear, and
a driving source that drives the driving gear, wherein:
the gear mechanism is a worm gear mechanism constructed of a worm and worm wheel,
the worm wheel is a gear which is an injection molded compact of a resin composition comprising a thermoplastic resin (A) and cellulose nanofibers (B) with an average fiber diameter of 1000 nm or smaller,
the worm wheel has a roundness of 400 μm or smaller,
the thermoplastic resin (A) includes a polyamide resin, and
the resin composition has a thixotropic index of 2 to 10 at a temperature of 25° C. higher than the melting point of the thermoplastic resin (A).

13. The gear system according to claim 12 , which is an EPS (electric power steering) gear system.

Assignees

• Asahi Chemical Ind

Inventors

• Tsuzuki Junichi
• Kusumoto Sara

Classifications

• C08L77/02 Primary

  Polyamides derived from omega-amino carboxylic acids or from lactams thereof (C08L77/10 takes precedence) · CPC title

• C08L2205/16

  Fibres; Fibrils · CPC title

• C08L59/00

  Compositions of polyacetals; Compositions of derivatives of polyacetals (of polyvinyl acetals C08L29/14) · CPC title

• F16H55/06

  Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties · CPC title

• B62D5/0424

  the axes of motor and final driven element of steering gear, e.g. rack, being parallel · CPC title