JPH0548132U - High impedance interface cable - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] The present invention mainly relates to a high impedance interface cable 1 for connecting a small computer defined by the SCSI standard and a peripheral device such as a hard disk device to each other. A high-impedance interface cable 1 having a characteristic impedance of 90Ω and a small diameter and a small size is provided. [Structure] Firstly, a plurality of twisted pairs of foam insulating core wires in which a center conductor is covered with a foam cross-linked insulator are assembled and twisted together, and a polyethylene raw yarn screen /
Wrap the mesh tape in a spiral shape, and then A
After the 1-polyester tape was spirally wound, a double shield was applied with a braided wire to provide a sheath. Secondly, a PTFE (tetrafluoroethylene) resin tape was used in place of the polyester thread screen mesh tape.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention mainly relates to a high-impedance interface cable for interconnecting a small computer defined by the SCSI (Small Computer System Interface) standard and a peripheral device such as a hard disk device.

[0002]

[Prior Art]

 As a standard interface standard for small computers and peripheral devices such as hard disk drives, SCSI is established by ANSI (American National Standards Institute), ISO 9316 internationally, and JIS X6051 domestically. . Along with the recent increase in information processing volume, peripheral devices conforming to the SCSI standard have rapidly spread, and interface cables used for connecting devices have been required to have small diameters, small sizes, and high impedance. Conventionally, PVC has been widely used as an insulator for interface cables, but the dielectric constant of PVC is as high as about 3 to 7, and if the outside diameter of the insulator is reduced to reduce the diameter and size, the impedance will be reversed. However, there was a certain limit to high impedance. Further, from the viewpoint of preventing generation of radiation noise from the interface cable or noise immunity (capability of eliminating interference against interference waves), a double shield structure using an Al foil tape and a braided wire is preferable. However, when the double shield structure is used, the capacitance between the core wire pair increases, and thus the impedance decreases, which is a conflicting factor. Therefore, in order to reduce the diameter and size and to increase the impedance, an insulator with a lower dielectric constant than PVC is used. To reduce the impedance due to the double shield structure, it is conceivable to provide an intervening material between the core wire pair and the shield to provide a gap.

[0003]

[Means for Solving the Problems]

The present invention has conducted extensive studies in order to make a conventional interface cable high impedance, small diameter, and downsizing. As a result, the characteristic impedance (Single Ended, hereinafter) is taken into consideration in consideration of the contents of 4.2 in JIS X6051. , S.E.) of 90 Ω and high impedance of small diameter and miniaturization. ・ The purpose is to provide the interface cable 1. The main point is to reduce impedance by applying double shield. Focusing on the factor of, the characteristic impedance will be increased by creating a gap by providing some kind of inclusion between the double-shield and the twisted pair of twisted wires. That is. The conditions for inclusions in this case are: ○ Low dielectric constant. ○ It must be thick to some extent and a distance between them can be secured. ○ It is difficult to grow. ○ Being inexpensive. ○ A material that does not impair flexibility such as bendability as a cable. A high-impedance interface cable characterized by using polyethylene raw thread screen mesh tape or porous PTFE (tetrafluoroethylene) resin tape to meet these conditions. That is, the first is to gather and twist a plurality of twisted pairs of foamed insulation core wires in which the center conductor is coated with foamed cross-linked insulation, and twist the polyethylene raw thread screen mesh tape on top of it. To wind. Furthermore, a high-impedance interface cable is characterized in that an Al-polyester tape is spirally wound on top of it, then double shielded with a braided wire, and a sheath is provided. The second is a high-impedance interface cable characterized in that a PTFE (tetrafluoroethylene) resin tape is used in place of the polyester thread screen mesh tape.

[0004]

【Example】

Hereinafter, an embodiment of the high impedance interface cable 1 of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 (a) is a perspective view of the high impedance interface cable 1 of the present invention seen from the side. FIG. 1B is a sectional view thereof. As is clear from the figure, the high impedance interface cable 1 of the present invention comprises a plurality of twisted pair wires 4 of a foam cross-linked insulation core wire in which a center conductor 2 is covered with a foam cross-linked insulation material 3 (usually 19 pairs, 25 pairs). Pair) Assembled and twisted, spirally winding a screen mesh tape 5 knitted with polyethylene raw yarn on it, and further spirally winding an Al-polyester tape 6a on it, and then a braided wire It is a structure in which a double shield is applied at 6b, a Washi tape 7 is vertically attached, and finally a sheath 8 is applied. As the foamed cross-linked insulator 3, foamed cross-linked polyethylene was used, and HDPE (high density polyethylene) was expanded by 40% or more, and further cross-linked by electron beam irradiation to improve mechanical strength and heat resistance. The polyethylene raw thread screen mesh tape 5 used had 20 to 300 stitches. Although it is desirable that the interposing tape have a lower dielectric constant, the use of the screen mesh tape 5 creates an air gap, and since a part of the air layer can be taken in, a large number of air gaps can be provided. A porous PTFE (tetrafluoroethylene) resin tape may be used instead of the screen mesh tape. In each case, a dielectric material having a low dielectric constant ε of 2 is used. Next, as a noise countermeasure, a double shield structure of an Al-polyester tape 6a and a braided wire 6b was adopted. The Washi tape 7 is not always necessary, but it is better to have it.

Table 1 shows the structure and characteristic impedance (SE) test results of the high impedance interface cable 1 of the present invention.

[0006]

[Table 1]

As is clear from Table 1, there are two types of type A, which has an insulator outer diameter of 0.83 mm and a sheath outer diameter of 9.0 mm and B type which has an insulator outer diameter of 0.87 mm and a sheath outer diameter of 9.5 mm. Conducted with different cable constructions. Table 1 shows the result of the characteristic impedance (SE) test of the present invention, that is, the TDR method (Time Domain Reflectometry) (see FIG. 2). As is clear from Table 1, regarding the characteristic impedance (SE), it was possible to clear 90Ω for both types, and good results were obtained.

Although a typical cable structure has been described so far, various modifications are included within the scope of the present invention in terms of design, such as a double shield structure, material changes, and slight process changes. Needless to say.

[0009]

[Effect of the device]

As described above, according to the high impedance interface cable 1 of the present invention, not only does it conform to the SCSI standard, but it also has a small diameter and a small size, and it is perfect for noise suppression and is ideal for high quality data transfer. We believe that its industrial value is very large because it has the excellent effect of providing a high impedance interface cable.

[Brief description of drawings]

FIG. 1A is a perspective view of a high impedance interface cable of the present invention seen from the side. (B) is
Sectional drawing of the high impedance interface cable of this invention.

FIG. 2 is an explanatory view of the characteristic impedance (SE) test of the present invention (measurement vs. pattern).

[Explanation of symbols] 1 high impedance interface cable 2 center conductor 3 foam cross-linked insulation 4 twisted pair of foam insulation core wire 5 polyethylene raw thread screen mesh tape or porous PTFE (tetrafluoroethylene) resin tape 6a Al-polyester tape 6b Braided wire 7 Washi tape 8 Sheath

Claims (2)

[Scope of utility model registration request] 1. A plurality of twisted pairs of a foam insulating core wire in which a center conductor is covered with a foam cross-linked insulator are gathered and twisted together, and a polyethylene raw thread screen mesh tape is spirally wound on the twisted wire. A high-impedance interface cable characterized in that an Al-polyester tape is spirally wound on it, and then double-shielded with a braided wire to provide a sheath. 2. A high impedance interface cable characterized in that a porous PTFE (tetrafluoroethylene) resin tape is used in place of the polyester thread screen mesh tape of claim 1.