JPS6338763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup tone arm, and more particularly to an improvement in a tone arm having a structure in which a second mass is supported on a bearing fulcrum via a viscoelastic body.

Generally, in a pick-up tone arm used in a record player, the low resonant frequency (hereinafter referred to as _p )
stipulates. That is, as shown in FIG. 1, _the resonance peak of _p often reaches 10 to 16 dB. _p mentioned above
Therefore, it is excited by disturbances and warping of the record board,
The pick-up tone arm changed significantly with _{the p} period, which significantly affected the playback quality. In order to damp such resonance, an oil damping method as represented by the equivalent circuit shown in FIG. 2 and a dynamic damping method represented by the equivalent circuit as shown in FIG. 3 have been used. The equivalent circuits for the oil dipping method and dynamic damping method above only look at the low range, and the high range is omitted. Zm is the mechanical impedance seen from the stylus tip, Vr is the velocity amplitude of the record sound groove,
Cp and Rp are the equivalent compliance and equivalent resistance of the cartridge resonator. (below,
Written as Cp and Rp. ) Also, Mt is the equivalent weight seen from the tip of the tone arm, including the weight of the cartridge, and Rt is the equivalent resistance at the bearing fulcrum, which is the viscous resistance due to the oil damping effect. (Hereinafter referred to as Rt.) Mt ₁ and Mt ₂ in FIG. 3 are the equivalent mass of the main body of the tone arm and the equivalent mass of the vibration absorption part, respectively. (Hereinafter referred to as Mt ₁ and Mt _2. )
Cd ₁ Rd is the equivalent compliance and equivalent resistance of the damper joining Mt ₁ and Mt ₂ . (below,
Written as Cd and Rd. ) In this case, Rt is so small that it can be almost ignored. Of the equivalent circuits shown in Figures 2 and 3 above, in the oil damping method, as shown in Figure 4, as the damping effect increases, the response in the ultra-low range below 0 points increases, and rather , it is not practical in combination with recent high compliance type cartridges. Furthermore, in the dynamic damping method, the effect is difficult to be seen unless the mass of Mt ₂ is increased relative to Mt ₁ in FIG. 3, and there is a problem in that it is easily affected by external vibrations and the like. In order to solve these problems, a device is known in which a second mass 6 is supported on a bearing fulcrum via a viscoelastic body 4, as shown in FIG. Equivalently, this structure has a mass 6 of Mt ₂ and a viscoelastic body 4 that represents an equivalent compliance Cd and an equivalent resistance Rd, and can be represented in an equivalent circuit similar to that shown in FIG.

The present invention provides a pickup tone arm having a structure shown in FIG. 5 with improved damping characteristics, and is characterized by interposing a viscoelastic material between the second mass and the fixed part. This is what I did. Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 6 to 8.

The equivalent circuit of the present invention is as shown in FIG. 6, which is the equivalent circuit of the dynamic damping method shown in FIG. 3 with Rt added.
Mt ₁ , Mt ₂ , and Cd, Rd constants,
FIG. 7 shows changes in the reduced resonance characteristics when Rt is changed. However, a shows the reduction characteristic of a general tone arm in which no damping is applied at all, and b shows the case where the dynamic damping shown in FIG. 3 is appropriately applied. In this case, if the constant of Rd is not appropriate, a single resonance type pattern like b will not be obtained, but a two-resonance type peculiar to a dynamic damping pattern will be obtained. In the present invention, it has been found that by appropriately setting the value of Rd as described above and adding Rt, it is possible to create a pattern with a suppressed resonance peak, such as C.

Next, a specific structural example according to the present invention is shown in FIG. 2 is the cartridge body provided at the tip of the tone arm, and 1 is its cantilever.
3 is an arm pipe that connects the cartridge 2 and the bearing main body 7, and further has a weight 5 behind it.
is inserted. Reference numeral 9 denotes a bearing rotating portion of the tone arm main body, and the tone arm is supported by the base of 8.
On the vertical axis of the bearing main body 7 of the tone arm 3, there is a second mass, that is, a stabilizer 6, supported at one point via a viscous body or a viscoelastic body 4, and this mass constitutes Mt ₂ in FIG. The above viscous body or viscoelastic body 4 has an equivalent compliance Cd and an equivalent resistance Rd.
It consists of The second mass 6 is statically balanced, and a part of the second mass 6 is grounded through the viscous fluid, and in this case, the viscous body 1
1 corresponds to the equivalent circuit Rt in FIG. 10 is a cup for storing viscous fluid 11, which is fixed to the arm board side. In this example, cup 10
is constructed so as to surround the outer periphery of the second mass 6, but if the value of Rt or the structure is restricted, this is not the case, for example, the second mass 6
A structure may be considered in which only a portion of the ground is connected to the ground via viscous fluid.

Since the present invention is configured and operates as described above, a greater damping effect can be obtained compared to conventional damping methods, and since the vibration of the tone arm at point _p can be reduced, stable operation can be expected. The increase in response below point _P is only slightly greater than with the oil damping method, so it is excellent in tracking warping of records. Furthermore, in the present invention, by adding Rt, it is also possible to set the mass of Mt ₂ small, increasing the degree of freedom in design.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram showing a typical frequency characteristic example of the bass range of a pickup, Fig. 2 is an equivalent circuit of a conventional oil damping tone arm, Fig. 3 is an equivalent circuit of a conventional dynamic damping tone arm, Fig. 4 is a characteristic diagram near _p to explain the damping effect due to bearing resistance Rt, Fig. 5 is a schematic diagram of a dynamic damping type tone arm to explain the present invention, and Fig. 6 is a diagram of the present invention. FIG. 7 is a characteristic diagram near _p showing the damping characteristics of the present invention, and FIG. 8 is a plan and side view of an embodiment of the pickup tone arm of the present invention. In the figure, 1 is a cantilever, 2 is a cartridge body, 3 is an arm pipe, 4 is a viscoelastic body, 5 is a weight, 6 is a second mass, 7 is a bearing body, 8 is a base, 10 is a cup, and 11 is a It is a viscous body.

Claims (1)

[Claims] 1. An arm support for rotatably supporting the arm is provided on the substrate, and a stabilizer for damping the arm is provided on the arm at a position corresponding to the support portion on the arm via a viscoelastic body. 1. A pickup tone arm on which a tone arm is mounted, characterized in that a container containing a viscous fluid is provided on the substrate, and an end of the stabilizer is inserted into the viscous fluid.