Speaker with magnetic structure for damping coil displacement
US5909499A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 28, 1997 |
| Grant date | Jun 1, 1999 |
| Priority date | — |
| Expiry date | Jul 28, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R9/043
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A speaker including a magnetic circuit formed by an annular yoke and an annular magnet which are concentric around a central axis and face each other across a gap. The magnet includes an N pole region and an S pole region successively arranged along the central axis direction and divided by an imaginary boundary line. At rest, a first coil is positioned in the gap in the N pole region, and a second coil is positioned in the gap in the S pole region. When the coils are driven by an excessively large current, a portion of the first coil moves beyond the boundary line to enter the S pole region, thereby causing a gentle first damping force on the first coil to prevent an excessive displacement. Likewise, the excessive current causes the second coil to move beyond the boundary line to enter the N pole region, thereby causing a second damping force which is opposite in direction to the first damping force. The damping forces limit a displacement range of the coils such that a damper does not collide with the magnet and similarly, the lower end of a bobbin does not collide with a frame of the speaker, thereby preventing collision sounds. The damping forces also prevent excessive stretchi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.