JPH08185909A - Watertight insulation connector - Google Patents

Abstract

PURPOSE: To prevent the occurrence of a crack at low temperature by using a material with a good low temperature characteristic for the inner layer of a thermally contracting double insulation tube for a connector used for a wire cord connected section with the caulking connection method. CONSTITUTION: A metallic sleeve 3 is capped with a thermally contracting double insulation tube having an outer layer 1 of high density polyethylene, as well as an inner layer 2 as a bonding layer containing resin with a good low temperature embrittlement characteristic such as ethylene and alkyl (metha) acrylate.carbon monoxide copolymer. For the bonding layer, a material having a low embrittlement temperature equal to or below -25 deg.C and free from a crack at low temperature is used, thereby providing a connector of high reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a watertight insulating connector used for connecting electric wires by crimping while ensuring waterproofness and dustproofness.

[0002]

2. Description of the Related Art A connecting method for connecting electric wires by crimping is widely used for intermediate connection of electric wires or for attaching a connecting terminal to an end of an electric wire cord because the connecting work is simple and easy. ing. When this caulking connection method is used, for example, in the intermediate connection part of an electric wire and this connection part requires protection from the external environment such as waterproofness, in general, a copper sleeve is put on the end of the electric wire cord and caulking is performed. After making the connection, the tape was wrapped around the outside to ensure waterproofness.

On the other hand, a connector in which the connecting end of the electric wire is covered with a metal sleeve and caulked, and the outside of the electric wire is covered with a heat-shrinkable synthetic resin tube so as to ensure waterproofness and insulation, is fair. It is known from Japanese Patent No. 8379. The connector of this publication is a heat-shrinkable double tube in which a heat-meltable resin layer is adhered to the inside of the tube, which is provided on the outside of the metal sleeve, and after caulking with a tool from the outside of the double tube, It is said that the tube is heated and shrunk, and the heat-melting adhesive applied to the inside is fluidized to fill the gaps from the pores, so that the waterproof property can be reliably ensured.

In addition to this, the connector has the same basic idea as the connector according to the above publication, but as connectors having different shapes and connection methods, it is disclosed in Japanese Utility Model Publication No. 3-34059 and Japanese Utility Model Publication No. 6-502.
Various items such as Japanese Patent No. 53 are also known. In any case, the heat shrinkable double tube is used.

[0005]

By the way, in the method of winding the tape around the connecting portion by crimping as described above, the reliability of the waterproof property changes depending on the skill of the operator, and the rabbit angle and the reliability are used in the case of emergency use. This method cannot be used for finished products that require cost.

However, when the heat-shrinkable double tube used in the connector according to the above-mentioned various publications is used as the insulating tube, the variation in waterproof reliability due to the skill of the operator can be eliminated, but on the other hand, Problem arises. That is, in the hot-melt resin used for the inner layer of the insulating tube, the coating of the electric wire inserted in the connection portion is mainly PVC.
Since it is (polyvinyl chloride), high adhesiveness is required for it, and an amide resin which can obtain strong adhesiveness to PVC is used.

However, when such a resin is used, the low temperature bendability required for an electric wire harness for an automobile may be insufficient. In particular, when the amide resin is bent at a low temperature (-40 ° C), the low temperature flexibility of the amide-based resin may be insufficient to cause cracking, which causes cracking of the outer layer portion. In the worst case, it may develop into a complete break of the insulating tube.

The present invention takes into consideration the problem of the connector due to the conventional caulking connection described above, and the heat-shrinkable double layer even in an environment where the temperature difference between the low temperature and the high temperature due to the engine is large in a cold region. An object of the present invention is to provide a watertight insulating connector capable of preventing cracking at low temperature and obtaining highly reliable waterproof property by selecting an adhesive having good low temperature characteristics for the inner layer of the insulating tube.

[0009]

As a means for solving the above problems, the present invention provides a metal sleeve and a heat-shrinkable double insulating tube on the outside thereof, and the outer layer of the insulating tube is a heat-shrinkable resin, The inner layer has a low temperature embrittlement temperature of -25 ° C or lower,
Melt flow index 5 to 3 at measurement temperature of 150 ° C
It is a heat-meltable resin having an adhesive strength to the vinyl chloride resin composition of 00 g / 10 minutes and a width of 0.1 kg / 20 mm or more,
Watertight insulating connector consisting of an adhesive layer containing either ethylene / alkyl (meth) acrylate / carbon monoxide copolymer, ethylene / vinyl acetate copolymer having maleic anhydride in the side chain, or copolymerized fluororesin It was.

[0010]

The characteristics required for the heat-meltable resin applied to the inside of the heat-shrinkable double tube used in the water-tight insulating connector of the present invention having the above-mentioned structure are determined by the melting point of the outer heat-shrinkable layer. Melt sufficiently at low temperature to focus on the gap, melt flow index is 5g / 10min-3
When it is between 00 g / 10 minutes, it exhibits sufficient fluidity when heated, and has an adhesive force to polyvinyl chloride (PVC) of 0.1 kg / 20 mm width or more, preferably 0.3
It has a width of at least 20 mm and has a low temperature embrittlement temperature of -2.
It is required to be 5 ° C or lower.

The condition (1) is basically necessary as an adhesive for a heat-shrinkable double tube, and if it deviates from this range, the reliability of waterproofness is lowered. That is, if it is too small, the gap cannot be sufficiently filled, and if it is too large, the amount of it staying inside due to the flow out decreases. With regard to (2), if it is smaller than this, it will come off the surface of the wire with a small force, and water will enter inside due to the capillary phenomenon. About JISK72
It is essential that the embrittlement temperature measured in 16 be equal to or lower than this temperature, and if it is higher than this temperature, it will be broken by low temperature bending at -40 ° C.

In order to achieve the above characteristics, a part of ethylene / vinyl acetate copolymer (EVA), ethylene / ethyl acrylate copolymer (EEA) or ethylene / alkyl (meth) acrylate copolymer is modified. Obtained resin and EV with high VA content and high EA content
An adhesive containing either A, EEA resin, or fluorocopolymer resin can be used.

Various additives used as hot melt adhesives, such as tackifiers and antioxidants, may be added in appropriate amounts.

Further, the amide resin known as a hot melt adhesive for PVC may be added with the above resin in the range of 30 to 90 parts. When the amide resin content is higher than this range, the low temperature property is deteriorated and the embrittlement temperature is -4.
It rises above 0 ° C.

The resin of the outer layer is required to have a hardness such that it will not be shaken or largely deformed when a force is applied by a crimping jig for crimping the copper sleeve. Then, as a result of evaluating various resins, the Shore D hardness is in the range of 45 to 71, and the range of 56 to 71 is particularly preferable. The types of resin include high density polyethylene, medium density polyethylene,
It is selected from low density polyethylene, EVA, EEA, ionomer resin, vinylidene fluoride, ethylene / tetrafluoroethylene copolymer resin, etc., or a mixture thereof.

Of these, high-density polyethylene alone, a mixture with EVA or low-density polyethylene, or an ionomer resin and a mixture is preferable. As the cross-linking method, widely known methods such as ionizing radiation irradiation and chemical cross-linking methods using a peroxide or a silane compound can be used. Further, an antioxidant such as a hindered phenol type may be added to improve heat resistance. As the method for manufacturing the double insulating tube made of the above resin, a method including the widely-used steps of simultaneous extrusion, crosslinking and expansion can be used.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an external perspective view and a main sectional view of a watertight insulating connection cord A of an embodiment. 1 is an outer layer tube,
2 is an adhesive layer and 3 is a metal sleeve. Outer layer tube 1
For example, a heat-shrinkable resin such as high-density polyethylene, which will be shown in the examples later, is used. The adhesive layer 2 is various types of hot-melt (heat-melting) adhesives which will be shown in Examples later. The metal sleeve 3 is a copper crimping sleeve. C is an electric wire cord and d is a bare wire.

FIG. 1 (b) shows an electric wire insertion state before caulking connection, and FIG. 1 (c) shows a state in which the double heat-shrinkable tube on the right side half after the caulking connection is heat-shrinked. Also, FIG. 2 shows (a)
The caulking connection work and (b) heat shrinking work are shown.

The outer layer tube 1 of the connector A of the above embodiment,
Examples of applying various polymer materials to the adhesive layer 2 will be specifically shown later, but before describing the connectors thereof, a characteristic evaluation method thereof will be described in advance.

There are various items for evaluating the characteristics of the waterproof connector, but the following are the items that are considered to be important centering on the evaluation test method for low temperature properties that can be particularly improved by the present invention, and the pass / fail judgment thereof. The standard is also shown.

A) Waterproofness: Leakage current is 0.25 microampere or less when AC 50V is applied between the electric wire and the electrode placed in water in the water tank. b) Heat cycle resistance 130 ° C x 0.5 hours → room temperature x 10 minutes → -25
After 5 cycles of 30 minutes at ℃, keep the waterproof property shown in a). c) Low temperature resistance Under the atmosphere of -20 ° C, the waterproof connector and the jig should be heated to this temperature and then crimped to show no abnormality such as cracks or tears in the insulating tube. Then, after heating and shrinking the tube, it is cooled to -40 ° C, and the electric wire on one side is bent by 90 ° while holding the copper sleeve portion, and no abnormality such as cracks is found.

FIG. 3 shows a leakage current measuring device used for carrying out the above-mentioned evaluation method for evaluating waterproofness. 10 is a water tank, 11 is an electrode, 12 is a holding means, 13 is an ammeter, 14 is a DC power supply device, A is a connector that has been subjected to heat shrinkage treatment after caulking connection, C is an inserted wire cord,
W is 5% saline.

In the following examples, the results evaluated by the above evaluation method are shown in each example.

Example 1 High density polyethylene (density 0.945) in the outer layer, 100 parts ethylene / alkyl (meth) acrylate-CO copolymer resin in the inner layer, 2 parts of partially saponified EVA, tackifier 5 such as hydrogenated terpene Part, 3 parts of an anti-aging agent such as Irganox 1010, and 2 parts of a hydroquinone-type cross-linking inhibitor, a double-insulated tube provided with a hot-melt adhesive was prepared based on a conventional method for producing a heat-shrinkable tube. After cutting the heat-shrinkable tube to an appropriate length, a copper sleeve was inserted, and the tube was heat-shrinked only at a portion corresponding to the length of the copper sleeve, to make a watertight connector.

The physical properties measured with the hot-melt adhesive sheet are: MFR 20 g / 10 min, adhesive strength to PVC 4.8.
The width was kg / 20 mm and the low temperature embrittlement temperature was −45 ° C. The melting point of the high-density polyethylene used for the outer layer was 121 ° C., and the Shore D hardness was 69. This was crimped and heat-shrinked on a 0.5 sq electric wire, and abnormal appearance such as cracks in this portion and waterproofness were confirmed. Finally, the results of the characteristic evaluation are summarized in Table 1 including the other examples.

Example 2 High density polyethylene (density 0.945) in the outer layer, 100 parts of EVA resin having maleic anhydride as a side chain in the inner layer, 20 parts of a tackifier such as hydrogenated terpene, and Irganox 10
A double insulating tube provided with a hot melt adhesive consisting of 3 parts of an antioxidant such as 10 parts and 1 part of a hydroquinone type cross-linking inhibitor was prepared based on a usual method for producing a heat-shrinkable tube. After cutting the heat-shrinkable tube to an appropriate length, a copper sleeve was inserted, and the tube was heat-shrinked only at a portion corresponding to the length of the copper sleeve, to make a watertight connector.

The physical properties measured with the hot-melt adhesive sheet are: MFR 210 g / 10 min, adhesive strength to PVC 8.
The width was 2 kg / 20 mm and the low temperature embrittlement temperature was -35 ° C.
The melting point of the high-density polyethylene used for the outer layer was 123 ° C and Shore D hardness was 69. This was crimped and heat-shrinked on a 0.5 sq electric wire, and abnormal appearance such as cracks in this portion and waterproofness were confirmed.

Example 3 A waterproof connector was prepared by using a resin known as a zinc ion type ionomer for the outer layer and the same one as used in Example 1 for the inner layer. The ionomer used had a melting point of 91 ° C. and a Shore D hardness of 62. This was also evaluated in the same manner.

Example 4 PVdF resin was used for the outer layer and Vdf65-72 / hexafluoropropylene 18-23 / tetrafluoroethylene 7-for the inner layer.
An insulating tube using a copolymerized fluororesin having a composition of 15 was prepared. As the PVdF resin for the outer layer, a mixture of a homopolymer having a melting point of 160 ° C. and a copolymer having a melting point of 140 ° C. in a ratio of 5: 5 was used. Shore D of this
The hardness was 71. One inner layer has a melting point of 90 ° C, MFR
It was 180.

Comparative Example 1 EVA (VA content 15%) was used for the outer layer and ethylene was used for the inner layer.
Alkyl (meth) acrylate-CO copolymer resin 100
Parts, 40 parts of tackifier such as hydrogenated terpene, 4 parts of anti-aging agent such as Irganox 1010, 1 part of hydroquinone type cross-linking inhibitor. made.

The physical properties measured with the hot-melt adhesive sheet were MFR of 500 g / 10 minutes or more, adhesive strength to PVC of 1.8 kg / 20 mm width, and low temperature embrittlement temperature of -20 ° C. EVA used for the outer layer has a melting point of Shore D at 90 ° C.
The hardness was 41. This was crimped and heat-shrinked on a 0.5 sq electric wire, and abnormal appearance such as cracks in this portion and waterproofness were confirmed.

Comparative Example 2 The same outer layer as in Example 1 was used, and the inner layer had a VA content of 5
%, EVA resin having a melting point of 103 ° C. was used to make a double insulating tube. The adhesive strength of the resin used for the inner layer to PVC was only 0.05 kg / 20 mm width.

Comparative Example 3 The same as in Comparative Example 1 was used for the outer layer, 100 parts of the polyamide resin for the inner layer, 50 parts of the partially saponified EVA resin, and 4 parts of the crosslinking inhibitor.
A double-insulated tube was prepared by using the one with added parts (low temperature embrittlement temperature −15 ° C.).

[0034]

[Table 1]

[0035]

As described in detail above, the present invention provides a water-tight insulating connector using a heat-shrinkable resin as the outer layer of the double insulation tube and a hot-melt resin adhesive having excellent low-temperature brittleness characteristics as the inner layer. Since it maintains its flexibility and does not crack even in an environment where the temperature difference between the cold and the high temperature due to the engine is severe in cold regions, etc., a highly reliable water-tight insulation connector can be obtained for automobile harnesses. It is effective when used as a crimp connector.

[Brief description of drawings]

FIG. 1 is an external perspective view and main cross-sectional view of a watertight insulating connector according to an embodiment.

FIG. 2 is a diagram for explaining the processing work of the above connector.

FIG. 3 is a schematic diagram of a leak current measuring device for evaluating waterproofness.

[Explanation of symbols]

 1 Outer layer tube 2 Adhesive layer 3 Metal sleeve A Watertight insulation connector C Wire cord d Line of sight

Claims (1)

[Claims] 1. A metal sleeve and a heat-shrinkable double insulating tube provided on the outside thereof, wherein the outer layer of the insulating tube is a heat-shrinkable resin, the inner layer is a low temperature embrittlement temperature of -25 ° C. or less, and the measurement temperature is 150 ° C. Melt flow index 5-300g /
10 minutes, adhesion to vinyl chloride resin composition 0.1k
A heat-meltable resin having a width of g / 20 mm or more, which is an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer, an ethylene / vinyl acetate copolymer having maleic anhydride as a side chain, or a copolymerized fluororesin. A watertight insulating connector comprising an adhesive layer containing any of the above.