Vibration damping apparatus for pulse motor

• US 4,938,325 A
• Filed: 09/20/1988
• Issued: 07/03/1990
• Est. Priority Date: 01/09/1986
• Status: Expired due to Fees

• Current Assignee: Shinko Electric Industries Company Limited (Fujitsu Limited)
• Original Assignee: Shinko Electric Industries Company Limited (Fujitsu Limited)
• Inventors: Nakagawa, Hiroshi
• Primary Examiner(s): Kashnikow, Andres
• Assistant Examiner(s): Le, Mark T.
• Application Number:
  US07/247,067
• Time in Patent Office: 651 Days
• Field of Search: 188/378, 188/379, 188/268, 188/380, 188/267, 188/266, 267/136, 267/137, 318/696, 318/685, 318/38, 310/51, 310/74, 310/49 R, 310/103, 310/105, 181/202, 403/291, 403/220
• US Class Current: 188/378
• CPC Class Codes: G11B 21/08 Track changing or selecting G11B21/12 takes precedenceduring transducing operation
• CPC Class Codes: H02K 37/22 Damping units

Abstract

A vibration damping apparatus for a pulse motor having a movable member. The apparatus has a back plate fitted to the movable member of the pulse motor for serving as a base part of the apparatus, a first permanent magnet mounted on a flat plate portion of the back plate for transmitting movement of the motor to later stages of the vibration damping apparatus, and an inertia member disposed in opposed relation to the first permanent magnet and movable relative to the first permanent magnet in a plane parallel to the flat plate portion and having a second permanent magnet thereon magnetically coupled with the first permanent magnet, the inertia member having a natural frequency substantially equal to the natural frequency of the pulse motor without the inertia member.

Claims

1. A vibration damping apparatus for a pulse motor having a movable member, comprising:

a back plate secured to said movable member of said pulse motor for serving as a base part of said apparatus;

a first permanent magnet mounted on a flat plate portion of said back plate for transmitting movement of the motor to later stages of said vibration damping apparatus; and

an inertia member disposed in opposed relation to said first permanent magnet and movable relative to said first permanent magnet in a plane parallel to said flat plate portion and having a second permanent magnet thereon magnetically couplable with said first permanent magnet, said inertia member having a natural frequency substantially equal to the natural frequency of said pulse motor without said inertia member, whereby when said back plate is being moved, said inertia member will tend to lag behind said back plate, and upon cessation of movement of said back plate, said inertia member will be moved to bring the poles of said second magnet into alignment with the opposite poles of said first magnet.

2. A vibration damping apparatus as claimed in claim 1 in which said pulse motor is a rotary motor having a shaft and said back plate is mounted on said shaft.

3. A vibration damping apparatus as claimed in claim 1 in which said inertia member includes a second back plate to which said second permanent magnet is secured.

4. A vibration damping apparatus as claimed in claim 1 in which said first permanent magnet and said second permanent magnet each have two poles of opposite polarity, and the opposite polarity poles on the respective magnets are opposed to each other.

5. A vibration damping apparatus as claimed in claim 1 in which said first permanent magnet and said second permanent magnet each have a plurality of poles of different polarity and the opposite polarity poles on the respective magnets are opposed to each other.

6. A vibration damping apparatus as claimed in claim 1 further comprising a spacer between said permanent magnets for reducing the magnetic coupling therebetween.

7. A vibration damping apparatus as claimed in claim 1 wherein the outer circumferential edges of said permanent magnets on the opposing faces thereof are circular arc-shaped in cross sectional profile.

8. A vibration damping apparatus as claimed in claim 1 in which said inertia member has a frequency of vibration according to the expression:

##EQU4## where K is an equivalent spring constant of the inertia member and J is the inertia of said inertia member for cancelling out the vibration of the pulse motor which occurs without said inertia member.