JPS5888B2 - pick up arm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup arm, and an object of the present invention is to significantly improve frequency characteristics in the bass range with a simple configuration.

First, let us explain the prior art to which the present invention is directed.

FIG. 1 is an explanatory diagram for explaining the vibration form of a conventional standard pickup arm. This pickup arm has a cartridge part 1 at its tip that converts mechanical vibration into an electric signal, and a rotation fulcrum 2. The structure has a structure in which a connecting rod part 3 made of pipe material or the like connects the two parts, and a weight 4 for balancing is provided on the opposite side of the cartridge part 1 with the fulcrum 2 in between.

In the figure, the needle tip 5 of the cartridge part 10 has a compliance Cs and a viscous resistance Rs, and the fulcrum 2 has a viscous resistance R.
p, this pickup arm has a resonance point at a certain frequency, and its resonance sharpness is Q0=(2π・fo・Ma)/(Rp+
It is known that it is represented by Rs.

Here, Ma is the equivalent image mass of this pickup arm system at the needle tip 5.

FIG. 2 shows the low frequency response characteristics of this pickup arm.

In this type of pickup arm, the viscous resistance Rs of the needle tip 5 is given by a minute rubber gunpa, etc., and the viscous resistance Rp of the fulcrum is given by a sensitive pivot bearing, etc., so it is small and can be ignored. value and the second
As is clear from the figure, Q0 eventually becomes a large value, causing the cartridge portion 1 to swing significantly at the resonance frequency f0, resulting in disadvantages such as the stylus tip 5 floating or coming loose from the record groove.

In order to eliminate such drawbacks of the conventional pickup arm shown in FIG. 1, a pickup arm called an oil dump arm was developed in which two parts of the fulcrum are provided with large viscous resistance using viscous oil or the like.

A schematic structure of this pickup arm is shown in FIG.

The pickup arm shown in FIG. 3 has a cartridge part 6 at its tip 5, which is connected to a rotating fulcrum 7 by a connecting rod part 8 made of a pipe, etc. This configuration has a weight 9 on the opposite side for balance.

On the other hand, a hemispherical portion 10 centered on the fulcrum 7 is immersed in a viscous oil 11 such as silicone oil 9 to be braked.

In FIG. 3, the needle tip 12 of the cartridge portion 60 has a compliance Cs and a viscous resistance Rs, and there are also five viscous resistances Rp due to the viscous oil 11 around the fulcrum.

FIG. 4 is a diagram showing the low frequency response characteristics of the oil dump arm shown in FIG. 3. The resonance of this pick-up arm system exists at a frequency of Ma)/(Rp+Rs).

Compared to the one shown in FIG. 1, this type of pick-up arm has a larger viscous resistance Rp due to the viscous oil 11 providing viscous resistance to the rotation of the arm at the fulcrum 7, and a lower resonance sharpness Q0. Since the value is small, there is no drawback that the cartridge section 6 swings greatly at the resonance frequency f0 as in the arm system shown in FIG.

However, even if the pickup arm tries to follow the warpage or eccentricity that exists on the record, the cartridge section 6 cannot follow the warpage or eccentricity due to the viscous resistance Rp given to the fulcrum 7, and only the stylus tip 12 can move. will follow.

As a result, the vibration system inside the cartridge part 6,
Warpage and eccentricity give a large mechanical bias,
Occurrence of distortion or stylus tip 12 in local recesses of the record
This caused problems such as separation of the disc from the record groove.

The present invention aims to eliminate these drawbacks of conventional pickup arms, and examples thereof will be described below.

FIG. 5 is an explanatory diagram illustrating the vibration form of the pickup arm of the present invention.

In the figure, reference numeral 13 denotes a connecting rod, at one end of which a cartridge 15 having a needle tip 14 and converting mechanical vibrations into electrical signals is disposed, and at the other end a balance weight 16 is connected, forming the arm body. are doing.

Next, reference numeral 17 is a bearing that supports the pedestal 18 rotatably in the horizontal and vertical directions, and the hole 19 indicates its fulcrum.

The pedestal 18 and the center of gravity of the arm body are connected by an elastic body 20 and a viscous resistance body 21.

Here, the needle tip 14 of the cartridge 15 has a compliance Cs and a viscous resistance Rs, the elastic body 20 has a compliance Ca, the viscous resistance body 21 has a viscous resistance Ra, and the fulcrum 19 has a viscosity that is almost negligible. Assuming that it has a resistor Rp, this pickup arm has two resonance frequencies near the lower limit of the reproduction frequency band, as shown in FIG.

That is, fo = and And Ru.

Further, the resonance sharpness at each frequency of fo and f1 is blurred.

Here, Ma is the equivalent mass of the pickup arm at the needle tip 19, and Mb is the equivalent mass of the arm body applied to the elastic body 17.

As shown by the dotted line in FIG. 6, it is indicated by the resonance sharpness at the resonance frequency f0, but if another resonance frequency f1 exists near the resonance frequency f0, its resonance sharpness Q.

Q shows a tendency to decrease as shown by the solid line in FIG. 6 due to the influence of the anti-resonance valley between the two resonances.

If the resonance sharpness Q1 is a relatively large value that cannot be ignored,
In order not to affect the reproduction frequency characteristics, the resonance frequency f1 is selected to be below the lower limit of the audible band, that is, below 20 Hz.

Since the pickup arm configured in this way has a lower resonance sharpness Q'o than the conventional one, the resonance frequency f.

The deflection of the cartridge portion 13 at 1 is reduced.

Furthermore, at the resonance sharpness Q1=(2π・f1・Mb)/Ra, if the viscous resistor 18 is configured to have a braking effect using viscous oil such as silicone oil or the viscosity of air passing through the pores, The viscous resistance Ra can be made relatively large, and the value of the resonance sharpness Q1 can be made small, and as shown in FIG. 7, the low frequency characteristic appears to be only Q'0.

This type of pickup arm does not have a large resonance sharpness Q0 like the conventional pickup arm shown in Fig. 1, and does not have unnecessary increase in viscous resistance of the support part like the oil dump arm shown in Fig. 3. You can get the ideal pickup arm without looking.

Next, specific embodiments of the pickup arm of the present invention will be described with reference to FIGS. 8 to 10.

In the above diagram, the same components as in FIG. 5 are given the same numbers.

In the figure, 13 is a connecting rod, 15 is a cartridge attached to one end of the connecting rod 13, 22 is a support member whose one end is connected to the other end of the connecting rod 13, and 16 is connected to the other end of the supporting member 22. This is a weight for balance, and the above constitutes the main body of the pickup arm.

Next, reference numeral 18 denotes a frame, which includes a frame-shaped outer frame 25 whose shaft portion 25a is fitted into a radial bearing 24 provided at the upper end of the cylindrical column 23 and is rotatable in the left-right direction; It is comprised of an inner pedestal 27 located inside and rotatable in the vertical direction with respect to the outer pedestal 25 by means of a pivot shaft 26a and a pivot bearing 26b.

The inner frame 27 is integrally provided with a spring fixing portion 27a, and the spring fixing portion 27a is inserted into the recess 22a of the support member 22 coupled to the connecting rod 13.

28 is a wire spring inserted into the center hole of the spring fixing portion 27a, and both ends of the wire spring 28 are inserted into the recess 2 of the support member 22.
By being fixed to the inner wall of the support member 2a,
2 and the inner frame 27 are connected.

Further, the recess 22a of the support member 22 is filled with viscous oil such as silicone oil.

In the above embodiment, the elastic body 20 shown in FIG. 5 corresponds to the wire spring 28, and the fulcrum 19 corresponds to the pivot shaft 26a, the pivot bearing 26b, the radial bearing 24, and the shaft portion 25a of the external frame 25.

In addition, the viscous resistance body 21 includes a spring fixing portion 27a and a support member 22.
It is formed by putting viscous oil into the space formed between the support member 22, that is, the recess 22a provided in the support member 22.

Note that instead of filling the above-mentioned viscous oil, the recess 2 of the support member 22 is
The space inside the recess 22a is separated from the outside by a rubber membrane or the like, and pores are provided in the rubber membrane, and the pores connect the space inside the recess 22a with the outside air to reduce the viscous resistance of the air passing through the pores. The viscous resistor 21 may be formed using the same.

As explained above, according to the pickup arm of the present invention, the frequency characteristics, especially the characteristics in the low frequency range, are significantly improved, and a pickup arm can be provided that has excellent trackability of record grooves.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram illustrating the vibration form of a conventional pickup arm, Fig. 2 is a low frequency response characteristic diagram of the same pickup arm, and Fig. 3 is an explanatory diagram illustrating the vibration form of a conventional oil dump type pickup arm. 4 is a low frequency response characteristic diagram of the pickup arm, and FIG. 5 is an explanatory diagram illustrating the vibration form of the pickup arm of the present invention.
Figures 6 and 7 are low frequency response characteristic diagrams of the pickup arm, Figure 8 is a perspective view showing a specific example of the pickup arm, and Figure 9 shows the pivot point of the pickup arm. A front sectional view, and FIG. 10 is a sectional view of the same side. 13... Linking rod, 15... Cartridge, 16... Balance weight, 17... Bearing, 18... Frame, 20...
Elastic body, 21... Viscous resistance body, 22... Support member, 23
...Strut, 24...Radial bearing, 25...Outer frame, 26a...Pivot shaft, 26b...Pivot bearing, 27...Inner frame, 27a...Spring fixing part, 28...
...wire spring.

Claims (1)

[Claims] 1. A pedestal that supports the arm body, a bearing that holds the pedestal rotatably in vertical and horizontal directions, an elastic body that connects the pedestal and the arm body, and a viscous resistance body that applies braking to the elastic body. A pickup arm.