Assist mechanism and electric power steering device

Patent metadata

Field	Value
Publication number	US-11702127-B2
Application number	US-201816957961-A
Country	US
Kind code	B2
Filing date	Dec 18, 2018
Priority date	Dec 28, 2017
Publication date	Jul 18, 2023
Grant date	Jul 18, 2023

Abstract

An assist mechanism includes: an electric motor in which a rotor has a magnet and a stator has a winding; a shaft-shaped member in which a worm engaged with a worm wheel is formed; and a coupling that couples an output shaft of the electric motor and the shaft-shaped member to each other. The smallest rotation order among rotation orders of the electric motor and a rotation order of the worm are prime to each other.

First claim

The invention claimed is:

1. An electric power steering device comprising an assist mechanism, wherein
the assist mechanism comprises:
an electric motor;
a shaft-shaped member in which a worm engaged with a worm wheel is formed; and
a coupling that couples an output shaft of the electric motor and the shaft-shaped member to each other,

a rotation order of the worm and a rotation order of the coupling are prime to each other,
the rotation order of the worm is the number of teeth of the worm wheel that advance in response to one rotation of the shaft-shaped member,
the coupling comprises:
a first transmission member fixed to the output shaft;
a second transmission member fixed to the shaft-shaped member; and
a third transmission member engaged with a predetermined number of projections of each of the first transmission member and the second transmission member to couple the first transmission member and the second transmission member to each other,

the worm wheel is provided to an output shaft of a steering wheel,
the electric power steering device is a column assist power steering device,
the first transmission member and the second transmission member have the same number of projections,
the rotation order of the coupling is equal to the number of the projections,
a first elastic member is provided between the first transmission member and the third transmission member,
a second elastic member is provided between the second transmission member and the third transmission member, and
the third transmission member has higher rigidity than the first elastic member and the second elastic member.

2. The electric power steering device according to claim 1 , wherein
a smallest rotation order among rotation orders of the electric motor and a rotation order of the worm are prime to each other, and the smallest rotation order among the rotation orders of the electric motor and a rotation order of the coupling are prime to each other.

3. The electric power steering device according to claim 1 , wherein
the rotation order of the electric motor is n times a larger natural number of two natural numbers other than 1 when a multiplication of the two natural numbers expresses the number of poles of a magnet in the rotor, and
n is a natural number of 1 or greater.

4. The electric power steering device according to claim 1 , wherein the rotation order of the coupling is 5 or 7.

5. The electric power steering device according to claim 1 , wherein
the smallest rotation order among the rotation orders of the electric motor is 3,
the rotation order of the worm is 2, and
the rotation order of the coupling is 5 or 7.

6. The electric power steering device according to claim 1 , wherein
the smallest rotation order among the rotation orders of the electric motor is 4,
the rotation order of the worm is 3, and
the rotation order of the coupling is 5 or 7.

7. The electric power steering device according to claim 1 , wherein
the smallest rotation orders among the rotation orders of the electric motor is 5,
the rotation order of the worm is 2, and
the rotation order of the coupling is 7.

8. The electric power steering device according to claim 1 , wherein
the smallest rotation order among the rotation orders of the electric motor is 5,
the rotation order of the worm is 3, and
the rotation order of the coupling is 4.

9. The electric power steering device according to claim 1 , wherein
at least two rotation orders of a smallest rotation order among rotation orders of the electric motor, a rotation order of the worm, and a rotation order of the coupling are different from each other.

10. The electric power steering device according to claim 1 , wherein
the smallest rotation order among the rotation orders of the electric motor, the rotation order of the worm, and the rotation order of the coupling are different from one another.

11. The electric power steering device according to claim 1 , wherein
the rotation order of the electric motor is n times a larger natural number of two natural numbers other than 1 when a multiplication of the two natural numbers expresses the number of poles of a magnet or a commutator in the rotor, and
n is a natural number of 1 or greater.

12. An electric power steering device comprising an assist mechanism, wherein
the assist mechanism comprises:
an electric motor in which a rotor has a magnet and a stator has a winding;
a shaft-shaped member in which a worm engaged with a worm wheel is formed; and
a coupling that couples an output shaft of the electric motor and the shaft-shaped member to each other,

a smallest rotation order among rotation orders of the electric motor and a rotation order of the worm are prime to each other,
the rotation order of the electric motor is n times a larger natural number of two natural numbers other than 1 when a multiplication of the two natural numbers expresses the number of poles of a magnet in the rotor,
n is a natural number of 1 or greater,
the rotation order of the worm is the number of teeth of the worm wheel that advance in response to one rotation of the shaft-shaped member,
the worm wheel is provided to an output shaft of a steering wheel,
the electric power steering device is a column assist power steering device,
the first transmission member and the second transmission member have the same number of projections,
the rotation order of the coupling is equal to the number of the projections,
a first elastic member is provided between the first transmission member and the third transmission member,
a second elastic member is provided between the second transmission member and the third transmission member, and
the third transmission member has higher rigidity than the first elastic member and the second elastic member.

13. The electric power steering device according to claim 12 , wherein
the rotation order of the coupling is 5 or 7.

14. An electric power steering device comprising an assist mechanism, wherein:
the assist mechanism comprises:
an electric motor;
a shaft-shaped member in which a worm engaged with a worm wheel is formed; and
a coupling that couples an output shaft of the electric motor and the shaft-shaped member to each other, wherein

a smallest rotation order among rotation orders of the electric motor and a rotation order of the coupling are prime to each other,
the rotation order of the electric motor is n times a larger natural number of two natural numbers other than 1 when a multiplication of the two natural numbers expresses the number of poles of a magnet or a commutator in a rotor,
n is a natural number of 1 or greater,
the coupling includes
a first transmission member fixed to the output shaft;
a second transmission member fixed to the shaft-shaped member; and
a third transmission member engaged with a predetermined number of projections of each of the first transmission member and the second transmission member to couple the first transmission member and the second transmission member to each other,

the worm wheel is provided to an output shaft of a steering wheel,
the electric power steering device is a column assist power steering device,
the first transmission member and the second transmission member have the same number of projections,
the rotation order of the coupling is equal to the number of the projections,
a first elastic member is provided between the first transmission member and the third transmission member,
a second elastic member is provided between the second transmission member and the third transmission member, and
the third transmissio

Assignees

• Nsk Ltd

Inventors

• Honda Yasushi

Classifications

• B62D5/0454 Primary

  Worm gears · CPC title

• F16D3/74

  the intermediate member or members being made of rubber or other {rubber-like} flexible material · CPC title

• F16H1/16

  comprising worm and worm-wheel · CPC title

• H02K5/24

  specially adapted for suppression or reduction of noise or vibrations · CPC title

• H02K7/003

  Couplings; Details of shafts (means for mounting rotors on shafts H02K1/28) · CPC title