JPS6211401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pick-up tone arm for a record player, and more particularly to a pick-up tone arm having a vibration absorber and a gap portion of the mass portion of the vibration absorber that generates a repulsive magnetic field. . The low resonant frequency f ₀ , which is determined by the compliance of the pick-up cartridge stylus tip and the effective mass seen from the stylus position of the tone arm containing the cartridge, is approximately 10 mm ² , taking into account warping of records, etc. It is preferable to set Also, low resonant frequency o
In general, a resonance peak with a high Q occurs at a point of 10 to 15 dB.
This results in a slight increase in response, and due to record warping and external vibrations, needle skipping is likely to occur, and tracking to the sound groove becomes extremely unstable. In order to reduce these instability, a pickup tone arm constructed as shown in FIG. 1 is conventionally known. In FIG. 1, a cartridge 1 is fitted to the tip of a tone arm 2, a counterweight 4 is provided at the rear, and an oil cup 5 is mounted on an arm stand 6 at a bearing fulcrum 3 of the tone arm. The equivalent circuit of an oil dump type pick-up tone arm is rotatably connected by an upright pivot holder, and a viscous fluid 7 is interposed between the tone arm's bearing fulcrum 3 and an oil cup. can be expressed as shown in Figure 2. In the equivalent circuit, Mt is the pick-up cartridge (including the shell) seen from the needle tip of cartridge 1.
is the equivalent mass of the tone arm 2 and counterweight 4, V is the velocity amplitude of the stylus given by the record surface, Cp, Rp are the equivalent compliance and equivalent resistance of the armature part of the cartridge 1, and Rt is the equivalent mass of the tone arm 2 and counterweight 4. The equivalent resistance of the viscous fluid 7 interposed between the bearing part 3 and the oil cup 5 is shown. The frequency characteristic in this case generally has one arm resonance, and the low resonance frequency ₀ has a sharp resonance point. On the other hand, as shown in Fig. 3, a tone arm has a damping structure in which a coupling having an elasticity Cd and an equivalent resistance Rd is provided between the arm 2 and the counterweight 4, and a vibration absorber is installed in combination with the mass Md. Therefore, the equivalent circuit can be expressed as shown in FIG. According to the braking method shown in Figures 1 and 2, as the amount of braking is increased, the response below the low-frequency resonance frequency o increases, which causes cross-modulation distortion to occur because the extremely low frequency range is reproduced. . Further, it has the disadvantage that it is extremely inconvenient to handle due to problems such as outflow of viscous fluid.
In addition, in the cases shown in Figures 3 and 4, the relationship between the resonance frequency of the vibration absorber and _{the zero} point of the low-frequency resonance frequency is very critical, but it is important to note that if these values are set appropriately, a great effect can be obtained. I have it. However, if the compliance of the cartridge increases and the low-frequency resonance frequency ₀ decreases, it becomes necessary to set the resonance frequency of the vibration absorber lower in proportion to this. In this case, lowering the resonance frequency of the vibration absorber means increasing the equivalent mass Md of the vibration absorber, or
Since the elastic component Cd is increased, the counterweight is structurally sagged, resulting in the drawback that it is difficult to obtain a tone arm with such a configuration. In order to eliminate such drawbacks of the tone arm shown in FIG. 3, a solution as shown in FIG. 5 can be considered.
That is, a coupling member 8 that does not come into direct contact with the tone arm 2 is arranged in correspondence with the equivalent mass Md in the equivalent circuit shown in FIG. Cd
A coupling ring 9 having a diameter is interposed so that the equivalent mass Md is supported at one point on the rotation center axis of the tone arm. The coupling member 8 and the coupling member 9 operate as vibration absorbers, but in terms of direct current, they operate together with the tone arm. , it may not follow its behavior and has elements that are functionally unstable. Another problem was that the tone arm was likely to come into contact with the hole 8a between the tone arm 2 and the coupling member 8.

It is an object of the present invention to provide a pickup tone arm that eliminates the above-mentioned drawbacks of the present invention, and its purpose is to reduce the equivalent mass of the coupling member 8.
This allows the Md to follow the rapid movement of the tone arm body, and also prevents the coupling member from coming into contact with the tone arm. For this purpose, in the present invention, the coupling part 8 and the tone arm 2 are Magnets that repel each other are provided at points that are likely to come into contact, and by using this repulsive force to avoid contact, the equivalent mass Md smoothly follows the movement of the tone arm. Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 6a, b to 9. In FIG. 6a, the ring-shaped magnet 10 is fitted onto the tone arm 2. The ring-shaped magnet is magnetized to N and S poles as shown. On the other hand, in the coupling member 8, a ring-shaped magnet 11 having a larger outer diameter than the ring-shaped magnet 10 is disposed opposite to the ring-shaped magnet 10, and is similarly magnetized in the thickness direction. That is, the ring-shaped magnet 10 and the outer ring-shaped magnet 11 are arranged so that the same polarity faces each other. Therefore, even when the tone arm 2 moves in the direction of the arrow, the tone arm 2 and the coupling member 8 follow the movement of the tone arm without coming into contact with each other due to the repulsive force of the mutual magnets.

In contrast to the one shown in FIG. 6b, in which two magnets are arranged facing each other in FIG. 6a, the magnetized poles magnetized in the thickness direction are opposite, and magnet 10
This is an example of placing it outside or inside. FIG. 7 is a side sectional view showing the arrangement of the magnets according to the present invention, and FIG. 8 is a perspective view of the rotary support portion.

Figure 7 shows the tone arm 2 attached to the coupling member 8.
A ring-shaped magnet 11 is fitted into the front hole 8a through which the tone arm 2 is inserted, and a ring-shaped magnet 10 is fitted into the tone arm 2 so that repulsive forces move with each other. They may be interposed between the tone arms, or may be provided at two locations as necessary. The repulsive force generated by such two ring-shaped magnets can be used as a kind of elastic effect.

The one shown in FIG.
A coupling member 8 has a structure that prevents viscous fluid from flowing out, and is supported at one point on its vertical central axis.
A viscous fluid 7 is interposed between the cup-shaped support portion and the equivalent resistance Rd (see FIG. 4), and the elasticity Cd is provided by two magnets 10 and 11. Since the elastic component Cd can be increased in this way, it is possible to lower the resonance frequency of the vibration absorber.

As described above, according to the present invention, the features of the method shown in FIG. 5 for damping the resonance peak at the low resonance frequency of ₀ can be further utilized. That is, the equivalent mass Md has a good ability to follow the rapid movement of the tone arm main body, and also operates stably without contact. Furthermore, the two repulsion magnets can be used as elastic components, and the compliance can be easily varied by adjusting the mutual gap, which is particularly easy when setting a vibration absorber with a low resonance frequency. Conventionally, it was very difficult to set up a vibration absorber with a low resonant frequency, but the present invention has the feature of providing a pickup tone arm that is highly stable and can achieve the desired performance.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the structure of a conventional oil damping tone arm, Fig. 2 is its equivalent circuit, Fig. 3 is a schematic diagram of a conventional tone arm with a vibration absorber, Fig. 4 is its equivalent circuit, and Fig. 5 is: Figure 3 shows the improved tone arm, Figure 6 shows the principle of the present invention, and Figures 7 to 9 show the improved tone arm.
The figures are a side cross-sectional view and an inclined view showing a specific example of the tone arm according to the present invention. In the figure, 1 is the tip of the tone arm including the pick-up cartridge, 2 is the tone arm, 3 is the bearing fulcrum, 4 is the counterweight, 5 is the oil cup,
6 is an arm stand, 7 is a viscous fluid, 8 is a coupling portion, 9 is a coupling, 10 and 11 are magnets, and 12 is a cup.

Claims (1)

[Claims] 1. In a pickup tone arm that holds a cartridge and is rotatably supported, the tone arm is equipped with a vibration absorber that uses anti-resonance due to a compliance component and a mass component, and a repulsive magnetic field generating means is provided between the tone arm and the vibration absorber. A pick-up tone arm characterized by attenuating low-frequency resonance of the provided tone arm.