JPH0132561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turntable for a record carrier such as a record disc (hereinafter abbreviated as turntable).

Conventional turntables are generally press-formed from steel plates or aluminum plates, or die-cast from aluminum alloys or zinc alloys.

For turntables manufactured using the press molding method,
Since the rolling direction is not radial, there are disadvantages such as weight and acoustic characteristics not being symmetrical with respect to the center of rotation.

Further, in turntables manufactured by die-casting, there is a difference in the timing of contraction as the molten metal cools and solidifies, causing deviations in the internal composition due to distortion and the formation of thin cavities. As a result, the weight balance of the turntable becomes uneven, requiring time and effort to adjust the balance. Furthermore, it is known that a turntable made of magnesium alloy has a higher internal loss than one made of aluminum and has a greater damping ability against external mechanical vibrations (Japanese Patent Application Laid-Open No. 131805/1983).
If this is manufactured by die-casting, the vibration damping will have an asymmetrical waveform. Also, no echo effect can be expected.

The present invention aims to provide a turntable that eliminates the conventional drawbacks as described above.

The material used for the turntable of the present invention is a magnesium alloy or a magnesium hot forging material.

Next, an example of a method for manufacturing a turntable according to an embodiment of the present invention will be explained based on illustrations. FIGS. 1 to 4 are cross-sectional views of an apparatus showing the manufacturing process. A material billet 2 of magnesium alloy (ZK60A) heated to 400°C to give it plasticity is placed in the center of the forging mold 1 which has been preheated to about 380°C in a hot air circulation furnace, and then Press molding machine (1000t) as shown in Figure 2
Position the punch 3 at the top, pressurize the billet 2 with the punch 3 as shown in Figure 3, and press the billet 2.
The central flat part 4 and peripheral thick part 5 of the turntable are finally formed by backward extrusion, and finally the punch 3 is raised and tightened by the punch 3 to shrink due to temperature drop. Place the molded part 6 of the turntable into the release ring 7.
The forging process was completed in just 1 minute and 30 seconds in this example.

The forging temperature is not limited to the above,
Any temperature within the range of 200-510°C can be selected.

Further, in FIG. 1, it is preferable that the crystal grains of the material billet 2 placed on the forging die 1 extend in the vertical direction.

Then, the turntable molded product 6 is subjected to heat treatment of T5 and T6 depending on the application, or after being left to cool naturally, the outside, inside, and top and bottom surfaces are finished by cutting, and a hole 8 for inserting the rotating shaft is formed in the center. Perforations are made and the finished product is finished as shown in FIGS. 5 and 6.

If you need to increase the moment of inertia,
The thickness and height of the peripheral thick wall portion 5 may be increased as appropriate.

The turntable formed as described above is finished by forging, so that the flow lines are arranged radially from the center to the outer periphery, the metal crystal particles are densely structured, and defects such as blowholes etc. Since there is no weight and the weight is uniform around the center of rotation,
The conductivity of the acoustic frequency becomes uniform and the rotation becomes stable.

In order to investigate the effect of the present invention on the acoustic characteristics of a turntable, the following three samples were manufactured using different materials and manufacturing methods, and tests were conducted to measure the vibration damping characteristics of each sample. However, the shape of each sample was a disk with a diameter of 150 mm and a thickness of 8 mm.

Sample A (Example) Material: Magnesium alloy ZK60A (Zn...5.5%,
Zr......0.45%, the balance is Mg. ) Production method: ZK60A casting billet with a diameter of approx.
It is heated to 380℃ and stretched to a diameter of 200mm using a hydraulic press, then cut to the final shape described above.

Sample B (Comparative Example 1) Material: Same as sample A.

Manufacturing method: A ZK60A cast billet with a diameter of 150 mm is cut to the final shape described above.

Sunpil C (Comparative Example 2) Material: Aluminum alloy A6063 Manufacturing method: Same as sample A.

In sample A according to the example of the present invention, grain flow lines are observed radially from the center of the disk.

FIG. 7 shows the measurement results of the vibration damping characteristics of sample A according to the example of the present invention. Figures 8 and 9
The figure shows the measurement results of Sample B and Sample C, which are comparative examples, respectively. In this test, a mechanical shock was applied to the center of each sample using an impulse hammer, and the vibrations measured at the periphery were converted into electrical signals, which were then observed using an oscilloscope. Several tests were performed on each sample, and the results were nearly identical to those shown in each figure for each sample.

In sample A of FIG. 7, the vibration is rapidly attenuated after the impact is applied. Furthermore, the vibration waveforms during this period are extremely symmetrical. Also, 200mS after impact is applied.
Even after this period, extremely stable microvibration remains. In sample B of FIG. 8, the vibrations are asymmetrically damped. The time from shock application to vibration disappearance is the shortest for sample B, approximately 40mS.
It is. In sample C of FIG. 9, while the vibration damping is slow, the residual time of minute vibrations is short.

In general, it is said that for turntables used in audio equipment, the higher the vibration damping ability, the better; in this respect, sample A is better than sample B.
It is slightly inferior. However, the turntable according to the present invention having radial grain flow lines performs regular attenuation and transmits sound with less distortion. Moreover, the long minute vibrations described above produce an echo effect. Therefore, by using the turntable according to the present invention, it is possible to create a good feeling that cannot be expressed numerically.

It should be noted that the above-mentioned turntable is not limited to one for use in record players, and of course includes turntables for use in various types of record carriers.

[Brief explanation of drawings]

1 to 4 are central sectional views of an apparatus showing a manufacturing process for explaining a method for manufacturing a turntable for a record carrier according to the present invention, and FIG. 6 is a sectional view of the center of the embodiment of FIG. 5, and FIG. 7 is a waveform showing the measurement results of the vibration damping characteristics of the turntable according to the embodiment of the present invention. 8 and 9 are similar waveform diagrams of a comparative example. In the diagram, 1...forging die, 2...billet, 3...
Punch, 4...Central flat part, 5...Peripheral thick wall part,
6... Molded product, 7... Release ring, 8... Hole.

Claims (1)

[Claims] 1. A turntable for a record carrier, characterized in that the material is a magnesium alloy or magnesium, and the grain flow lines are arranged radially from the center to the outer periphery.