JPH08212635A - Vtr lower cylinder - Google Patents

Abstract

PURPOSE: To easily secure vacuum on a lead surface where a tape travels and to reduce the cost of a VTR lower cylinder by providing a gate in a position between the tip part of a lower bearing hole in the direction of inserting a lower bearing of the VTR lower cylinder into this hole and a plane including the lower end part of a cylinder bottom part. CONSTITUTION: This VTR lower cylinder is molded by injection molding using a thermoplastic resin. The gate for filling the resin is set in the position (a gate setting range 6) between the tip part 4 of the lower bearing hole 3 in the direction of inserting the lower bearing into the hole 3 and the plane including the lower end part 9 of the cylinder bottom part 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VTR lower cylinder manufactured by injection molding.

[0002]

2. Description of the Related Art A conventional VTR lower cylinder uses aluminum, which is a non-ferrous metal.

In the manufacturing process, a blank is manufactured in advance by casting or die-casting in a size that allows for a finishing allowance, and a hole processing and an outer diameter necessary for mounting and evaluation are processed by a precise processing device. . For this reason, many processes are required to complete the VTR lower cylinder as a part, the cost is high, and a large space and a large amount of capital investment are often required when constructing an integrated processing line. There has been a need for a cost and easy method of manufacturing a VTR lower cylinder.

In recent years, in order to solve these problems, a method of manufacturing by injection molding using a thermoplastic resin as a material has been devised. It is expected that the required shape can be obtained by molding once, and equipment investment can be suppressed.

[0005]

Various methods have been tried for molding the VTR lower cylinder by injection molding. The resin to be applied is polyphenylene sulfide (PP) from the viewpoint of fluidity and dimensional stability.
S) is used. From the specifications of parts, it is necessary to add carbon fiber and a substance that improves slidability to a resin, and it is generally considered that the addition amount of about 70% by weight is good.

The roundness of the outer peripheral portion on which the tape runs is required to the required accuracy of a typical VTR lower cylinder, and the roundness is 20μ.
m or less is required.

However, it is difficult to achieve this precision by injection molding. Therefore, the present invention uses injection molding using a thermoplastic resin to achieve 20μ
An object is to provide a VTR lower cylinder that can achieve a roundness of m or less.

[0008]

The VTR lower cylinder of the present invention is formed by injection molding using a thermoplastic resin, and the resin-filled gate has a tip end portion in the insertion direction of the lower bearing of the cylinder. It is characterized in that it is installed between the flat surface of the cylinder bottom.

The VTR lower cylinder of the present invention is made of polyphenylene sulfide (PPS), liquid crystal polymer (L).
CP) and the like are used, and at least one kind of thermoplastic resin is used.

Further, the VTR lower cylinder of the present invention has a disk shape in which the gate filled with the resin is spread in all radial directions from the center at the installation position, and the gate thickness is the circularity of the cylinder outer circumference on which the tape runs. It is characterized in that it is set in a stabilizing region.

[0011]

In the VTR lower cylinder of the present invention, the gate is installed so as to be positioned between the front end of the cylinder in which the lower bearing is inserted and the plane of the bottom of the cylinder. It has become possible to increase the roundness of. Further, by using a thermoplastic resin composed of at least one of PPS and LCP, it is possible to perform injection molding with good fluidity and dimensional stability.

Further, by setting the thickness of the gate in the optimum region where the roundness is stable, it is possible to secure the stable roundness.

[0013]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows a VTR lower cylinder according to an embodiment of the present invention. For example, the VTR lower cylinder for VHS is
Bearings are press-fitted into the upper bearing hole 2 and the lower bearing hole 3, respectively, and the shaft is passed through the centers thereof. The structure is such that the VTR tape is wound around the lead surface 5 of φ62 and runs.

In this VTR lower cylinder, a 1.2 mm-thick gate center 7 is installed at a position 2.7 mm from the lower end 9 of the cylinder bottom 1, and a uniform center is spread in all radial directions from the center at the installation point. Provide a gate with thickness,
Injection molding was performed using a thermoplastic resin obtained by adding carbon fibers and a substance that improves slidability to polyphenylene sulfide (PPS). For gate position 7,
A good result that the roundness of the lead surface 5 was 17.3 μm was obtained, and it was confirmed that the condition of the roundness of 20 μm or less required for the lead surface 5 was satisfied.

In order to compare the roundness depending on the gate position, a thickness of 1.2 mm on the surface including the lower end 9 of the cylinder bottom 1.
The gate center 8 was set, and injection molding was performed using the same material as in the above-mentioned example. This gate position 8
In the case of, the roundness of the lead surface 5 is 44.7 μm, which is much lower than that at the gate position 7, and the roundness condition required for the lead surface 5 is not satisfied.

The roundness as a result of performing the same injection molding by setting the gate position in a range up to the position of the tip portion 4 in the insertion direction of the lower bearing hole 3 in addition to 8 and 7 shown in the figure is shown. Then, the distribution as shown in FIG. 2 was obtained, and it was confirmed that the gate position 7 achieved the best roundness of 17.3 μm.

In view of these experimental results, the position of the gate needs to be between the front end portion 4 of the lower bearing hole 3 into which the lower bearing is inserted and the plane including the lower end portion 9 of the cylinder bottom portion 1. The most desirable position can be said to be in the vicinity of a position that is located 2.7 mm below the plane including the lower end 9. This gate installation area is 6 in Figure 1.
It becomes as shown by. At this time, the inner diameter of 6 must be smaller than the inner diameters of the upper and lower bearing holes 2 and 3 and larger than the shaft.

The gate thickness is 0.4 mm to 2.0 mm.
The distribution of roundness when changed over the above is as shown in FIG. Based on this experimental result, the gate thickness is 1 m
It can be said that it may be m or more and 2 mm or less.

In the above embodiments, polyphenylene sulfide (PPC) was used as the thermoplastic resin, but the invention is not limited to this, and liquid crystal polymer (LCP) or the like may be applied. Is obtained.

[0021]

As described above in detail, according to the present invention, in the VTR lower cylinder formed by injection molding using a thermoplastic resin, the tip end portion of the cylinder in the insertion direction of the lower bearing and the cylinder bottom portion. By installing the gate located between the plane of
It becomes easy to secure the roundness of the outer circumference where the tape runs, and V
It greatly contributes to the cost reduction of the TR lower cylinder.

Further, by using a thermoplastic resin composed of at least one of PPS and LCP, it is possible to perform injection molding with good fluidity and dimensional stability.

Further, by setting the gate thickness in the optimum region where the roundness is stable, it is possible to ensure the stable roundness.

[Brief description of drawings]

FIG. 1 is a sectional view showing a VTR lower cylinder according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between gate position and roundness.

FIG. 3 is a graph showing the relationship between gate thickness and roundness.

[Explanation of symbols]

 1 ... Cylinder bottom 2 ... Upper bearing hole 3 ... Lower bearing hole 4 ... Lower bearing hole insertion direction tip 5 ... Lead surface 6 ... Gate installation range 7 ... Gate position 8 ... Gate position 9 ... Lower end of cylinder bottom

Claims (3)

[Claims] 1. A VTR lower cylinder formed of a thermoplastic resin, wherein a resin-filled gate is installed between a front end of the cylinder in the insertion direction and a plane of the cylinder bottom. Characteristic V
TR lower cylinder. 2. The VTR lower cylinder according to claim 1, wherein the cylinder is made of a thermoplastic resin made of at least one of polyphenylene sulfide (PPS) and liquid crystal polymer (LCP). 3. The gate has a disk shape extending in all radial directions from the center at the installation position, and the gate thickness is set in a region where the circularity of the outer circumference of the cylinder on which the tape runs is stabilized. The VTR according to claim 1,
Lower cylinder.