JPH05159632A - Flat cable - Google Patents

Abstract

PURPOSE:To make the generation of kink and discontinuity hard even in the case where the flat cable is made thin, and improve the durability by setting the surface condition of a polyester film of a flat cable at a specified roughness or more. CONSTITUTION:In a flat cable 10, multiple conductors 12 are arranged in parallel with each other, and are sandwiched by two polyester films 14, and they are fixed by an adhesive layer 16. The surface roughness of this film 14 is set so that a three dimensional center line mean roughness SRa, which is specified by JIS-B-0601, is set at 0.034mum. Durability of the flat cable is thereby improved, and even in the case where the winding and rewinding are repeated with the rotation of a steering wheel of an automobile, kink and disconnection or the like are hard to be generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor cable arranged at a steering wheel (hereinafter referred to as a handle) of an automobile and having one end thereof rotated integrally with the handle, and more specifically, a plurality of conductors sandwiched by a polyester film. The present invention relates to a flat cable that is sandwiched in a shape.

For example, in a vehicle equipped with an airbag, when an impact is applied to the vehicle, the impact captured by the sensor is converted into a signal and transmitted to the ignition device for the airbag arranged on the handle, so that the signal is transmitted to the handle. It has been practiced to arrange the conductor cable for the wound state.

FIG. 5 shows an example of the cable unit. In the figure, reference numeral 100 denotes a hollow cylindrical case, which is composed of a first member 102 and a second member 104 which are rotatable relative to each other.

A flat cable 106 is housed in a coiled state inside the case 100, and one end on the outer side is fixed to the second member 104 and extends from the second member 104. It is connected to 108. One end on the inner side is fixed to the first member 102 and is connected to a connecting cable 110 extending from the first member 102.

Here, in the flat cable 106, as shown in FIG. 6, a plurality of conductors 112 made of pure copper, for example, in the form of thin strips, which are arranged in parallel at a predetermined interval from each other, are made of a urethane adhesive layer with a polyester film 114. 1
It is sandwiched through 16 and thermocompression bonded, and is housed inside the case 100 in a state where the surfaces of the polyester film 114 are in contact with each other.
Here, the material of the polyester film 114 is selected depending on the electrical insulation, cost, and the like.

The flat cable 106 is wound in a coil inside the case 100 in order to transmit a signal to a rotating handle, specifically, an ignition device of an airbag arranged on the handle portion and other switches. It is a thing. That is, even when the handle is rotated, one end of the handle rotates together with the handle to transmit a signal.

More specifically, when the handle rotates in one direction, one end of the flat cable 106 rotates together with the handle and is wound into the inner cylinder portion of the case 100, and when rotated in the opposite direction, the flat cable 106 is wound into the inner cylinder side. The flat cable 106 is rewound and pressed against the outer cylinder side.

Here, the flat cable 106 is wound a large number of times with a sufficient margin so that the flat cable 106 does not extend even when the handle rotates to the maximum allowable amount (approximately two rotations on one side). ..

By the way, the flat cable 106 is
When the handle is operated, the polyester films 114 that are in contact with each other are wound and unwound while maintaining contact with each other. At that time, involvement with the operation of the handle
It is necessary that the unwinding force spreads over the entire flat cable 106 so that the cable 106 can be uniformly wound and unwound.

Otherwise, stress concentrates on a portion of the flat cable 106, and a kink occurs at a specific stress concentration portion while the handle is repeatedly rotated right and left, resulting in a disconnection. This is the cause.

At the same time, the handle operation becomes heavy, which causes a problem that a sound is generated due to friction between the flat cables 106 during the handle operation.

Here, in order for the flat cable 106 to have a winding / unwinding force due to the operation of the handle, and the flat cable 106 as a whole can be smoothly wound / unwound, a thin film flat cable is required. 106 has a predetermined bending rigidity, and the cable 106 for each turn.
Good slippage between them is required.

[0013]

By the way, in recent years, there has been a demand for a compact case 100 for accommodating the flat cable 106, and accordingly, it has become necessary to thin the flat cable 106. ..

However, the flat cable 106 is originally a thin one having a half thickness (strictly speaking, the thickness between the conductors 112 and 112) of about 110 μm (of which the thickness of the polyester film 114 is about 60 μm). When the thickness is further reduced, for example, when the thickness of the polyester film 114 is set to about 30 μm, the bending rigidity of the flat cable 106 becomes low, and the winding / unwinding force associated with the handle operation is less likely to spread to the entire flat cable 106. The problems such as the above-described kink or disconnection due to the kink easily occur.

[0015]

The present invention has been made in order to solve such a problem, and its gist is to sandwich a plurality of conductors arranged in parallel with a polyester film via an adhesive layer. It has a flat shape that is sandwiched in a circular shape, and is housed in a state in which the movable side is integrally rotated with the steering wheel of the automobile and is wound in a plurality of windings, and the steering wheel is rotated. According to JIS B 0601, the flatness of one or both of the front and back surfaces of a flat cable that is wound / unwound within the case is regulated according to JIS B 0601.
This is because the dimensional centerline average roughness SRa is 0.034 μm or more.

[0016]

FUNCTION AND EFFECT OF THE INVENTION The present inventor initially constructed a flat cable by simply using a thin polyester film, and evaluated its performance. It has been found that problems such as easy occurrence of kinks due to the decrease in the bending rigidity of the flat cable due to the increase in the number of products and the defective rate of the product become extremely high.

Therefore, the present inventor has focused on the surface roughness of the polyester film in view of the unavoidable decrease in bending rigidity due to the thinning of the polyester film, and made it a predetermined roughness. It turned out to be possible.

That is, the surface roughness of the polyester film, that is, the surface roughness of the flat cable is measured according to JIS B 0601.
The three-dimensional centerline average roughness specified in paragraph 0.034 μm
By the above, it has been found that the durability of the flat cable can be improved to a certain level or more, and the rotating torque at the time of operating the handle can be suppressed to be small.

The centerline average roughness means the value of the centerline drawn so that the areas of the peaks and valleys of the roughness curve are exactly equal, and the three-dimensional centerline average roughness (SRa) is , The measurement values of the entire surface of the polyester film. Since the center line average roughness is specified in detail in JIS B 0601, further detailed description of the content is omitted here.

The characteristics such as durability are improved by setting SRa to be equal to or more than the above-mentioned constant value because the minute and minute unevenness in the polyester film is increased, and as a result, the substantial contact area between the flat cables is reduced. It is considered that the mutual sliding resistance has decreased.

In the present invention, the SRa value is 0.034 μm.
When the value is increased beyond m, the steering resistance of the steering wheel, that is, the steering wheel torque, decreases substantially along with this, and the durability life characteristic is stabilized within a certain SRa value range. It was found during ongoing research that there is a fact that the durability life characteristics tend to deteriorate from a certain point when the value is increased.

That is, when SRa is 0.2 to 0.45 μm, the durable life characteristics are stabilized, and when SRa is further increased, the durable life characteristics tend to deteriorate.

Here, the stabilization of the durable life characteristics means that the variation in the measured values is reduced. For example, when the repeated durability test is performed for the surface roughness SRa of 0.2 to 0.45 μm, the average value of the measured values is smaller than 0.2 μm (however, 0.0
The difference in measured values is smaller than that of 0.2 μm or less.

This is because, when SRa is increased to 0.2 to 0.45 μm, it is more difficult for the unevenness to be filled with dirt or the like when the dirt or the like is attached to the uneven surface, as compared with those having a smaller surface roughness. It is presumed that this is due to an incident.

On the other hand, when SRa is further increased, the reason why the durability life characteristic tends to deteriorate from some point is presumably due to the following reasons.

Generally, when SRa is increased, SRz (three-dimensional ten-point average roughness) is also increased accordingly.

Here, the ten-point average roughness is the difference between the average value of the altitudes of the mountains from the highest mountain to the fifth mountain of the roughness curve and the average value of the altitudes of the valleys from the deepest valley to the fifth. The three-dimensional roughness (SRz) is a measured value of the entire surface of the polyester film (this ten-point average roughness is also defined in detail in JIS B 0601).

That is, as SRa is increased, the thickness of the locally thin film portion of the film having the predetermined film thickness becomes smaller, and as a result, the bending rigidity locally decreases at the same portion. It is considered that this portion becomes a weak point in strength and durability is lowered.

According to the experiments conducted by the present inventor, SRz is 5.5.
It has been found that the durability life characteristic is deteriorated when the thickness exceeds 0 μm. That is, according to the initial experiment of the inventor, S
Good results were obtained at Rz = 0.86 μm or less, but during further research it was found that good results could be obtained if SRz = 5.50 μm or less even in the region where SRz is larger than this. did.

By the way, as means for imparting unevenness to the polyester film, (a) a method of sandblasting the film surface, (b) solid fine particles (filler) such as silica, talc, barium sulfate are dispersed in the film in advance, Various methods such as a method of forming irregularities on the surface by these fillers (hereinafter referred to as filler kneading) and other methods are known.

In the present invention, it is desirable to use the one obtained by kneading the filler of (ii).

When a polyester film having irregularities formed by kneading a filler is used, SRa can be made smaller under the same SRz, or SRz can be made smaller under the same SRa, as compared with the case where irregularities are formed by another method. be able to. In other words, the durability life characteristics of the flat cable can be improved under the same SRa.

This is because the unevenness of the uneven surface is higher in the case of (b) in which the filler is kneaded and the shape of the unevenness is, for example, in the case of the sand blasting process in (a), as shown in FIG. In contrast to the projection 120 having a sharp shape as shown in Fig. 3, in the case of the method (b), the projection 120 has a relatively round shape as shown in (b) in the figure. It is considered that this is due to

It has been confirmed that the usefulness of this filler kneading method is particularly great for a thin polyester film having a film thickness of 25 to 35 μm.

It is speculated that this is because as the film thickness becomes thinner, the influence of the unevenness of the surface becomes relatively larger than the influence of the bending rigidity on the durability.

The present invention can be preferably applied to a flat cable in which the thickness of the polyester film is about 0.1 to 0.5 with respect to the thickness 1 of the conductor.

[0037]

Embodiments of the present invention will now be described in detail with reference to the drawings. In FIG. 1, reference numeral 10 denotes a flat cable, in which a plurality of conductors 12 are arranged in parallel in a state of being separated from each other in the width direction,
It is sandwiched by 14 and fixed by an adhesive layer 16.

When the surface state of the polyester film 14 was variously changed as shown in Table 1 by the above-described filler kneading method, the handle torque and the rotation and durability test of the handle were repeated, and the results shown in Table 1 were obtained. It was

Here, in the rotation repetition durability test, the handle is rotated at a speed of 5 rps for two and a half rotations in both the right and left directions, and this is repeated, and the number of times until the disconnection is reached is obtained.

The results shown in Table 1 are for the polyester film 1
4 has a thickness of 30 μm, eight conductors 12 are arranged in parallel, and the flat cable 10 having a width of 25 mm and between the conductors 12 and 12 has a thickness of about 150 μm (the thickness of the adhesive layer 16 is 45 μm × 2 = 90 μm) shows a result of a test performed on a flat cable.

[0041]

[Table 1]

As can be seen from the results of Table 1, good results can be obtained when the surface of the polyester film 14 is made uneven according to the present invention.

Next, a flat cable 10 of a different type from that used in the above test, specifically, six conductors 12 are arranged in parallel and has a width of 20 mm and a thickness between the conductors 12 and 12 is about. In the flat cable 10 of 150 μm,
The surface roughness was variously changed by the filler kneading method, and the handle torque, the rotation repetition durability test, and the rubbing noise measurement based on the rubbing of the flat cable 10 during the handle operation were performed. The results are shown in Table 2.

For comparison, the same test was carried out for a sandblasted product having the surface roughness of the polyester film 14 changed. The results are also shown in Table 2 together.

[0045]

[Table 2]

In the results of Table 2, SRa ≧ 0.034
At μm, the handle torque becomes smaller than a predetermined value,
In addition, when SRa ≧ 0.034 μm and SRz ≦ 5.50 μm, good durability is obtained, particularly when the thickness of the polyester film 14 is 25 μm and 30 μm,
It can be seen that the result obtained by providing the unevenness by the filler kneading method is better than that obtained by the sandblasting process.

As described above, SRa = 0.2 to 0.4
When the thickness is 5 μm, the durability is more stable as compared with SRa <0.2 μm.

This can be confirmed from the results shown in FIGS. The results shown in these figures are the same as No. 1 in Table 2 above. 3 and No. A number of samples were tested for 4 and 4 and the degree of variability of each measured value of each sample is shown.

SRa is 0.2 μm as shown in the figure.
It can be seen that, with respect to the above-mentioned ones, the variation in the measurement result is smaller than that of the one having SRa of less than 0.2 μm, and a stable value is obtained.

The embodiment of the present invention has been described in detail above, but this is merely an example, and the present invention has a half thickness of 110 μm.
The present invention can be applied to a flat cable having a thickness that has been conventionally used, and various modifications can be made based on the knowledge of those skilled in the art without departing from the spirit of the invention.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of main parts of a flat cable that is an embodiment of the present invention.

FIG. 2 is a diagram showing the degree of variation in measured values in a durability test conducted on an example product of the present invention.

FIG. 3 is a diagram showing the degree of variation in the measured values of the durability test performed on the products of other examples of the present invention.

FIG. 4 is a model view showing the difference in the uneven shape due to the difference in the method of giving unevenness to the surface of the polyester film.

FIG. 5 is a view showing a state in which a flat cable is stored in a case.

FIG. 6 is a diagram showing a cross-sectional structure of a flat cable together with an example of a manufacturing method.

[Explanation of symbols]

 10 flat cable 12 conductor 14 polyester film 16 adhesive layer

Claims (1)

[Claims] 1. A flat form in which a plurality of conductors arranged in parallel are sandwiched by a polyester film with an adhesive layer sandwiched between the conductors, and the movable side is provided so as to rotate integrally with a steering wheel of an automobile. It is stored in the inside of the case that is wound in multiple turns,
In a flat cable that is wound / unwound within the case as the steering wheel rotates, the surface roughness of one or both of the front and back surfaces can be determined according to JIS B 0601.
Three-dimensional centerline average roughness SRa specified in 0.03
A flat cable characterized by having a thickness of 4 μm or more.