JPH099567A - Resin lead screw shaft - Google Patents

Abstract

PURPOSE: To obtain an inexpensive, low vibration lead screw shaft by partially removing the starting part of ridge at the forward end part of screw and gradually increasing the minor diameter of groove at the end part of screw and composing the lead screw shaft of polyphenylene sulfide resin principally admixed with zinc oxide whiskers. CONSTITUTION: In a resin lead screw shaft being employed in the head driver for floppy disc, for example, the starting part 1a of ridge of screw part 1 is partially removed and the minor diameter 1b of groove at the end of ridge is increased in a section of length L gradually toward the straight outside diameter section 1c. The lead screw shaft is composed of polyphenylene sulfide resin principally admixed with zinc oxide whiskers in order to ensure a target dimensional accuracy. An inexpensive and excellent resin lead screw shaft can be obtained in the form of a single resin molding in which transmission of vibration to a driven system is retarded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead screw shaft used in a head drive device such as a floppy disk device.

[0002]

2. Description of the Related Art In recent years, lead screw shafts have come to be widely used as head drive devices for floppy disk devices because of their advantages in that they have a simple structure and can be made compact. Further, along with the price reduction of equipment and the reduction of vibration and noise, there is a growing demand for low price and low noise.

Metals, particularly stainless steel, have been often used as the material of the lead screw shafts. Stainless steel lead screw shafts are highly reliable and widely used due to their corrosion resistance and wear resistance. Another metal material is brass, which has good workability and can be processed with high precision.

A conventional mainstream metal lead screw shaft will be described below with reference to the drawings.

FIG. 2 is a front view and a side view of a conventional lead screw shaft used in a head drive device of a floppy disk device. The screw part 1 has an outer diameter of 3 mm, a root diameter of 2 mm, and a lead angle of 12 ° 55'4.
1 ″, lead pitch is 1.875 mm, and stainless steel (SUS303) is used as material. A small hole for connecting to a stepping motor (not shown) at one end 2
Is provided.

[0006]

However, the above-mentioned conventional lead screw shaft is highly reliable because it is made of metal, but it has the following three problems.

The first point is that there are many processing steps such as (material)-(primary cutting)-(screw cutting or grinding)-(centerless polishing)-(barrel polishing)-(cleaning). It becomes an expensive part. Secondly, since the elasticity is very small, it is easy to directly transmit the vibration generated from the stepping motor to the head of the floppy disk device which is the driven system. The third point is that the surface roughness of the flank 1d, which is a contact portion with the driven system, is limited in processing, and the roughness of the surface of the flank 1d is transmitted as vibration to the driven system. .

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a low-cost and low-vibration lead screw shaft.

[0009]

In order to achieve this object, the lead screw shaft of the present invention has a structure in which the beginning of the thread is partially removed at the beginning of the thread at the tip or the thread on the side opposite the tip is removed. The terminal end has a shape in which the root diameter of the thread groove is gradually increased, and the material is mainly composed of polyphenylene sulfide resin mixed with zinc oxide whiskers.

[0010]

With this structure, since the lead screw shaft can be manufactured by a single resin molded product, the process is simple and the cost can be reduced. Also, because the material is mainly polyphenylene sulfide resin mixed with zinc oxide whiskers, it is a resin lead screw that has a vibration suppressing effect, has a small shrinkage ratio and no directionality, and has excellent creep characteristics with environmental changes. The shaft becomes feasible.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a front view and a side view of a resin lead screw shaft used in a head driving device of a floppy disk device. The screw part 1 has an outer diameter of 3 mm, a root diameter of 2 mm, and a lead angle of 12 ° 55'4.
1 "and lead pitch is 1.875mm, which is the same as the conventional metal lead screw shaft. One end has a small hole 2 for connecting to a stepping motor (not shown) and gold Screw part 1 from the mold
There is provided a hexagonal part 3 for rotating and removing and a collar 4 for a gate.

FIG. 1 (b) is an enlarged view of the portion a in FIG. 1 (a). In FIG. 1 (b), the starting portion 1a of the screw thread is partially removed. Conventional thread method beginning part 1a
Had a sharp shape as shown in FIG. If the starting portion 1a of the screw thread has a sharp shape, there are various problems such as deformation and burrs occurring during resin molding, and an insufficient thread flow of the resin to form an accurate thread shape. According to the present invention, as shown in FIG.
The above-mentioned inconvenience is solved by adopting a shape with a part removed.

FIG. 1 (c) is an enlarged view of the portion B of FIG. 1 (a). In FIG. 1 (c), at the end of the thread, the root diameter 1b of the thread groove is gradually increased toward the straight outer shape portion 1c within an L dimension of 1.5 mm. The reason for gradually increasing the temperature is that the flow of the molten resin during molding is in the direction of the arrow 5 and if the root diameter 1b of the thread groove suddenly ends, for example, at L = 0.2 mm, the molten resin flow is disturbed and dimensional accuracy deteriorates. . Considering that the larger the L dimension, the longer the total length of the screw shaft and the narrower the range of usable equipment, the L dimension is preferably in the range of 0.5 to 2 mm.

Next, as the material of the lead screw shaft shown in FIG. 1 (a), a polyphenylene sulfide resin mainly containing zinc oxide whiskers was used in order to achieve a lead pitch cumulative tolerance of 10 μm. Zinc oxide whiskers have a tetrapot shape, which reduces the anisotropy of molded products.
Known as a vibration absorber. In addition, as a measure against strength, as a result of various investigations by mixing glass fiber, carbon fiber and the like, as a first material of the present invention, zinc oxide whiskers are 15% by weight and glass fiber is 2% by weight ratio.
It was discovered that a polyphenylene sulfide resin containing 0%, 10% carbon fiber and 20% calcium carbonate is a suitable material. Also, the individual compounding ratio is ±
Even if the amount was changed by 5%, a large difference in characteristics did not occur, but the compounding ratio at which the total amount of compounding is increased is not appropriate because the moldability deteriorates. As the second material, it was discovered that a polyphenylene sulfide resin containing about 60% by weight of zinc oxide whiskers, about 10% of carbon fibers and about 1% of fluorine is a suitable material. However, although the mold transferability was slightly worse than that of the first material, the target dimensions were achieved.

[0016]

As described above, in the lead screw shaft of the present invention, at the beginning of the thread at the tip, the beginning of the thread is partially removed or the end of the screw opposite to the tip is in the lead pitch direction. The lead screw shaft is made of a single resin molded product because the root diameter of the thread groove is gradually increased between 5 and 2 mm or less and the material is mainly composed of polyphenylene sulfide resin mixed with zinc oxide whiskers. Since it can be manufactured, it is possible to realize an excellent resin lead screw shaft that is inexpensive and is less likely to transmit vibration to the driven system.

[Brief description of drawings]

1A is an external view of a lead screw shaft according to an embodiment of the present invention, FIG. 1B is an enlarged view of a portion of FIG. 1A, and FIG. 1C is an enlarged view of a portion of FIG. 1A.

FIG. 2 is an external view of a conventional lead screw shaft.

FIG. 3 is an enlarged view of a starting portion of a thread at the tip of a conventional lead screw shaft.

[Explanation of symbols]

1 Lead screw part 1a Beginning of screw thread at the tip of the lead screw shaft 1b Valley diameter of the thread groove of the lead screw shaft 1c Partial straight outline of the lead screw shaft 1d Lead flank of the lead screw shaft

Claims (4)

[Claims] 1. A resin lead screw shaft comprising a lead screw shaft made of a resin, wherein the beginning of the thread is partially removed at the beginning of the thread. 2. A lead screw shaft made of a resin having a partially straight outer shape continuous with a threaded portion, wherein the threaded portion extending toward the straight outer shape has a thread groove in a lead pitch direction of 0.5 mm or more and 2 mm or less. Resin lead screw shaft characterized by gradually increasing the valley bottom diameter. 3. A compounding ratio of materials is 10 to 20% by weight of zinc oxide whiskers and 15 to 25 of glass fibers by weight.
%, Carbon fiber 5 to 15%, calcium carbonate 15 to 25%, and the remainder being polyphenylene sulfide resin. 3. The resin lead screw shaft according to claim 1 or 2. 4. The resin lead according to claim 1, wherein the compounding ratio of the materials is 60% of zinc oxide whiskers, 10% of carbon fiber, 1% of fluorine, and the rest is polyphenylene sulfide resin. Screw shaft.