JPS58166897A - Receiver - Google Patents

Abstract

PURPOSE:To prevent the deterioration of sensitivity at a low range which is due to the variance of a diaphragm, by setting a sum of a synthetic stiffness of back air chamber and a stiffness of an acoustic load at >=3 times value as high as the equivalent stiffness of the diaphragm. CONSTITUTION:The synthetic stiffness of the 1st and 2nd back air chambers II and III is referred to as S2; and the synthetic stiffness of an acoustic load and an air chamberIis S1 respectively. Then (S1+S2)/S0 is set at >=3 so as to suppress the deviation of sensitivity for (S1+S2)/S0 i.e., the variance of sensitivity to a change of 50% of the S0 of a prescribed (S1+S2)/S0. Within 1dB where S0 is the equivalent stiffness of a diaphragm. Some effect may be given to the sensitivity if the volume is reduced for the chambersIIand III respectively in order to increase the S2. However, the variation of sensitivity can be suppressed down to about 0.2dB even with an estimated allowable dimension at 1/10mm.. As a result, the deterioration of sensitivity can be avoided despite the variance of size of the diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a handset used in a portable radio device, etc., and provides a handset that can prevent a decrease in sensitivity due to dimensional variations in the diaphragm of a converter constituting the handset. .

In general, the sensitivity of the handset is controlled by stiffness control, and the sensitivity depends on variations in the dimensions of the diaphragm, and the variations in the dimensions of the diaphragm significantly reduce the low-frequency sensitivity in particular.

In view of the above points, the present invention provides a telephone receiver in which low frequency sensitivity does not decrease due to variations in the dimensions of the diaphragm.

In general, this type of handset must secure a frequency band of 300 to 3400 Hz, which is defined by the telephone transmission standards, and thus a three-degree-of-freedom design has been commonly used to cover this band.

The basic equivalent circuit in this case is as shown in FIG.

In FIG. 1, γ-1. m-1 is the acoustic resistance and mass of the earpiece, mo, So are the mass and stiffness of the diaphragm, F
is the driving force, γ+1. m+1 is the acoustic resistance and mass of the braking element, S-2 is the stiffness of the acoustic load, S-1 is the stiffness of the front air chamber, S+1 is the stiffness of the first back air chamber, S+
2 is the stiffness of the second back air chamber.

Here, to cover the upper limit frequency of 3400 Hz, set the resonance frequency f5 of the vibration system to So = diaphragm equivalent stiffness SL: acoustic load, composite stiffness of front air chamber S2: back air chamber composite stiffness mo: approximately the mass of diaphragm do.

Here, when focusing on the low frequency that operates as stiffness control, the sound pressure P inside the coupler is given by the following equation.

ΔV: Volumetric displacement of the diaphragm V: Coupler volume (including the first oil chamber) γ: Air specific fuel ratio Po: Static pressure of the air inside the coupler From formula (2), in order to increase the sensitivity, (S0+81+8
2) needs to be reduced. Here So is Sl and S
If it is larger than 2, the sensitivity at low frequencies is greatly influenced by the magnitude of the diaphragm stiffness S0, and the stiffness io
Since it is proportional to the cube of the thickness of the diaphragm, manufacturing control becomes strict.

Therefore, the present invention aims to reduce So as much as possible so that it becomes 52) So...(3) to reduce the influence of the diaphragm stiffness on the sensitivity, and at the same time to control the low frequency sensitivity with the back air chamber. That is.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, reference numeral 1 denotes a magnet in which an annular groove 2 is formed, and this magnet 1 is fixed within an inner cylindrical body 3. 4 is a braking element, and this braking element 4 is constructed by, for example, forming a hole in the bottom surface of the inner cylindrical body 3 and storing a nonwoven fabric or the like in the hole. 6 is a diaphragm, and the edge portion of this diaphragm 6 is supported on the upper surface of the inner casing. A bobbin 6 is connected to the diaphragm 5, and a voice coil 7 is wound around the bobbin 6. The inner cylindrical body 3 is fixed within the outer casing 8. Reference numeral 9 denotes an earpiece provided in the opening of the outer housing 8, and this earpiece 9 has a hole 1o formed therein. In Fig. 2, ■ is the front air chamber, U is the first air chamber partitioned by the diaphragm 6 and the inner cylinder 3,
The first back air chamber (2) and the second back air chamber (2) are in communication via the braking element 4.

In this embodiment, in order to reduce So, an electrodynamic converter is used, and the first . 2nd dorsal air chamber ■.

In order to increase the synthetic stiffness S2 of ■, the back air chamber l,
(2) The volume of (2) is reduced.

Figure 3 is 1. Synthetic stiffness S2 of the second back air chamber ■, ■
, the acoustic load, the sum of the composite stiffness S1 of the front air chamber I, and the diaphragm equivalent stiffness S. Ratio (S1,082)/S
The sensitivity deviation with respect to 0, i.e. the given (S, 182)
/S0 ±60 of diaphragm equivalent stiffness S0
It shows the variation in sensitivity to % change. In addition,
The sensitivity variation is ±1d for a ±60% change in So.
If it is B, there is no practical problem.

As shown in FIG.
82)/S0 is set to 3 or more.

There is a concern that if the volume of the back air chamber is reduced in order to increase the stiffness of the back air chamber, it will affect the sensitivity. The change can be suppressed to 0.2 dB.

The present invention has the above-described configuration, and has the advantage of being able to prevent a decrease in sensitivity even if there are variations in the dimensions of the diaphragm.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of a handset, FIG. 2 is a sectional view of the handset in an embodiment of the present invention, and FIG. 3 is a diagram showing sensitivity deviation of the handset. 1...Magnet, 2...Groove, 3...
・Inner cylinder body, 4... Braking element, 5... Vibration plate, 6... Bobbin, 7... Voice coil, 8...・Outer housing, 9... Earpiece, 10... Hole, ■... Front air chamber, ■...
...First back air chamber, ■T...Second back air chamber. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 (d91 (31+s2)/s0

Claims (1)

[Claims] A telephone receiver characterized in that the sum of the combined stiffness of a back air chamber formed at the back of a diaphragm of a transducer and the stiffness of an acoustic load is three times or more greater than the equivalent stiffness of the diaphragm of the transducer.