JPS5928118B2 - Electromagnetic cartridge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pickup cartridge used for record reproduction, particularly an electromagnetic type cartridge.

Generally, electromagnetic cartridges are classified into three types: moving magnet type, moving coil type, and moving iron type.

The movable magnet type has been widely used in the past, but when attempting to reduce the equivalent mass of the vibrating system, there have been problems such as a drop in output voltage and deterioration of electrical characteristics due to large electrical impedance.

The moving coil type has problems in use and cost, such as the method of drawing out the coil lead wire, other manufacturing difficulties, difficulty in replacing the needle, and the need for a step-up transformer due to the small output voltage. Ta.

The movable iron type also has problems such as a drop in output voltage due to poor conversion efficiency, and deterioration of the linearity of the output signal with respect to vibration of the vibrator due to magnetic saturation of the magnetic circuit.

The present invention is an improvement on the conventional electromagnetic cartridge, and its first purpose is to reduce the equivalent mass of the vibration system by using a soft magnetic material for the vibrator.

The second objective is to reduce electrical impedance and improve electrical characteristics.

The third objective is to improve the linearity of magnetic flux changes due to needle tip displacement and to prevent magnetostriction.

Fourthly, the amount of change in magnetic flux with respect to needle tip displacement is increased to increase the output voltage.

Fifth, it is necessary to obtain a sufficient induction S/N ratio.

The sixth purpose is to simplify the component parts, make the manufacturing process easier, and improve the accuracy of processing and assembly.

Hereinafter, the present invention will be described in detail with reference to figures showing examples.

FIG. 1 shows a structural diagram of an electromagnetic car (IJ) according to the present invention.

FIG. 2 shows a diagram of the operating principle of the electromagnetic cartridge according to the present invention.
C represents the operating state with respect to the displacement of the vibrator when the positioning needle is displaced upward.

FIG. 3 shows the relationship between the electromagnetic force according to the present invention, the amount of change in magnetic flux in each pole piece and the amount of change in the combined magnetic flux with respect to the displacement of the tip of the cartridge. First, the configuration of the electromagnetic cartridge according to the present invention is shown. will be explained in detail with reference to FIG.

In Fig. 1, reference numeral 2 denotes a cantilever with a positioning needle 1 fixed at its tip, and a vibrator 3 made of a flat soft magnetic material or the like having a vibration fulcrum position 4 approximately at its rear end is fitted and fixed. There is.

Reference numeral 8 denotes a viscoelastic body made of rubber or synthetic resin, which is press-bonded to the rear end surface of the vibrator 3, and is compressed and deformed by the holder 9, thereby imparting appropriate braking resistance and equivalent stiffness to the vibrating system.

Permanent magnets 5a and 5b are made of a hard magnetic material having the same shape, size, and magnetic properties, and one end of a pole piece 6b made of a soft magnetic material is held between the opposing surfaces of the magnetic poles of the permanent magnets 5a and 5b. They are pressed together.

The other end of the pole piece 6b is on a line that is perpendicular to the axial direction of the cantilever 2 and passes through the vibration fulcrum position 4, and is located on a line that passes through the vibration fulcrum position 4.
It is located adjacent to.

Permanent magnets 5a, 5 with which the pole piece 6b is sandwiched and pressed together
Pole pieces 6 made of soft magnetic material etc. are attached to the magnetic poles at both ends of b.
One end of a+6c is pressed, and the other end is arranged at a symmetrical position in the figure with the pole piece 6b as the center, and 6a is attached to one end of the vibrator 3 on the position needle 1 side, and 60 is attached to the rear end of the vibrator 3. are placed adjacent to each other.

Moreover, the pole pieces 6a, 6b, 6c are the cantilever 2.
It is located at the upper position in the figure with respect to the central axis of the.

Coils 7a, 7b, and 7c are respectively wound around the pole pieces 5a, (ib, and 6c), and are connected to each other so as to effectively generate power in response to the displacement of the vibrator 3.

Next, the operation of the electromagnetic cartridge according to the present invention will be explained in detail with reference to FIG.

In FIG. 2B, when the vibrator 3 approaches the pole piece 6b, the magnetic resistance in the gap between pole pieces 6a and 6b and the magnetic resistance in the gap between pole pieces 6b and 6c become equal, and the pole piece 6a is separated from the permanent magnet 5a. In the figure, the downward direct current magnetic flux Φ and the pole piece 6c are the permanent magnets 5
Only the DC magnetic fluxes Φ upward in the figure from b are flowing, and there is no change in magnetic flux.On the other hand, inside the pole piece 6b, the DC magnetic fluxes Φ from the permanent magnets 5a and 5b cancel each other out, so there is no magnetic flux. does not flow.

Therefore, no power is generated in any of the coils 7a, 7b, and 7c.

When the vibrator 3 approaches the gap between the pole pieces 6a and 6b in FIG.
The magnetic flux increase amount +△Φ flows downward in the figure, and the oscillator 3
The upward magnetic flux increase amount +ΔΦ also flows through the pole piece 6b.

At this time, the magnetic resistance in the gap between the pole pieces 6b and 6c increases, and the DC magnetic flux from the permanent magnet 5b decreases, so that a downward magnetic flux decrease -△Φ flows relatively to the pole piece 6C. , an upward magnetic flux decrease of 1° C. also flows to the pole piece 6b through the gap.

Therefore, a downward magnetic flux variation ΔΦ in the figure flows through the pole pieces 6a and 6c, and an upward magnetic flux variation 2ΔΦ flows through the pole piece 6b, so that the coils γa, 7b
, 7c generate electricity.

When the vibrator 3 approaches the gap between the pole pieces 6b and 6C in FIG.
The downward magnetic flux increase +△Φ in the figure flows to b, and the upward magnetic flux increase + also flows through the vibrator 3 to the pole piece 6c.
△Φ flows.

On the other hand, since the magnetic resistance in the gap between pole pieces 6a and 6b increases, as in the case of FIG.
A downward magnetic flux decrease amount -△Φ flows relatively to each other.

Therefore, an upward magnetic flux variation ΔΦ in the figure flows through the pole pieces 6a and 6c, and an upward magnetic flux variation 2ΔΦ still flows through the pole piece 6b.
In cases b and 7c, power is generated in the opposite direction to that in case A.

That is, according to the present invention, firstly, a soft magnetic material can be used for the vibrator, the equivalent mass of the vibrating system can be reduced, and the characteristics can be improved.

Second, the electrical impedance can be kept low due to the structure, and the electrical transmission characteristics can be improved.

Third, the amount of change in the composite magnetic flux is the amount of change in pole pieces 6a and 6c.
The magnetic flux change amount is four times the magnetic flux change amount of the pole piece 6b, and the magnetic flux change amount is twice the magnetic flux change amount of the pole piece 6b, so that the linearity of the magnetic flux change amount with respect to the needle tip displacement can be improved, and the magnetostriction can be reduced.

Fourth, since the amount of change in magnetic flux with respect to needle tip displacement can be increased, the output voltage can be increased.

Fifth, when externally induced magnetic flux changes act in the vertical direction in Figure 1, the output voltages of coils 7a, 7b, and 7c are mutually canceled in response to magnetic flux changes, so the induction is not affected by externally induced magnetic flux changes. S/N ratio can be improved.

Sixth, because the magnetic circuit structure is placed on the top of the vibration system, it is possible to create a large gap between the record surface and the cartridge body containing the magnetic circuit during playback, making it easier for vibrations to match the recording angle of the record. Distortion can be prevented by providing a vertical tracking angle for the system.

Seventh, the pole piece permanent magnet can be simplified, and improvements in processing, precision, assembly, etc. can be expected.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of an electromagnetic cartridge according to the present invention, and FIG. 2 is a diagram of the operating principle of the electromagnetic cartridge according to the present invention.
FIG. 3 is an explanatory diagram showing the relationship between the amount of magnetic flux change in each pole piece and the amount of combined magnetic flux change with respect to the needle tip displacement of the electromagnetic cartridge according to the present invention. 1...Original needle, 2...Cantilever, 3
... Vibrator, 4 ... Vibration fulcrum position, 5
a, 5b...Permanent magnet, 6 a? 6b,
6 c""" pole piece, ?a. 7b, 7c... Coil, 8... Viscoelastic body, 9... Holder.

Claims (1)

[Scope of Claims] 1. A cantilever 2 having a tone needle fixed to one end and a vibrator 3 made of a soft magnetic material having a vibration fulcrum position 4 approximately at its center end fixedly fitted to the other end, and the vibrator. A viscoelastic body 8 made of rubber or synthetic resin is crimped to the rear end surface of 3;
It has a vibration system composed of a holder 9 that compresses and changes the viscoelastic body 8 from its rear part, and includes two permanent magnets 5a,
5b and the permanent magnets 5a and 5b, respectively, are in pressure contact with different magnetic pole surfaces, and their ends are perpendicular to the axial direction of the cantilever 2 and are on a line passing through the vibration fulcrum position 4, and are arranged adjacent to the vibrator 3. The first pole piece 6b made of a soft magnetic material, etc., and the far apart magnetic poles of the pole piece 6b of the permanent magnets 5a and 5b are symmetrical in the longitudinal direction with respect to the pole piece 6b and in the axial direction of the vibrator 3. The second and third parts are made of a soft magnetic material, etc., and are arranged adjacent to each other at both ends.
pole pieces 6a and 6c, and the first, second, and third pole pieces 6a and 6c.
Three coils 7at7b are wound around the pole pieces 6b, 6a, and 6c so that the winding directions are different between the pole pieces, and are connected in series. 7c, and only when the vibrator 3 is displaced, magnetic flux changes are produced in the first, second, and third pole pieces 6b, 6a, and 6c. , γb, and 7c.