JP2014104691A - Fuel tube, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel tube heating time and cooling time of which, when the fuel tube is bent, are shortened.SOLUTION: The fuel tube 10 has an inner layer for forming a fuel passage and an outer layer layered on the outer peripheral side of the inner layer. The outer layer is formed from a first polyamide-based resin material selected from PA11, PA12 or PA1012 and the inner layer is formed from a second polyamide-based resin material of PA612. When the melting point of the first polyamide-based resin material and that of the second polyamide-based resin material are defined respectively as Tm1 and Tm2 and the glass transition temperature of the first polyamide-based resin material and that of the second polyamide-based resin material are defined respectively as Tg1 and Tg2, Tm2-Tm1 is 10-30°C and Tg2-Tg1 is 10°C or higher.

Description

  The present invention relates to a fuel tube and a manufacturing method thereof.

  Conventionally, a fuel tube is used in a fuel supply system that connects a fuel tank and an engine of an automobile, for example. The fuel tube is brazed along a predetermined curved path. Such a resin tube is formed by extruding a polyamide-based resin material such as PA11 to form a tube intermediate, bending the tube intermediate while being heated to a predetermined temperature or more, and further cooling and taking out the tube. It is manufactured by.

  Moreover, the resin tube concerning another technique has a bellows part in the part, and respond | corresponds to the bending path | route in the location of a bellows part (patent document 1).

JP 2000-2376 A

  However, the former resin tube according to the conventional technique has a long heating and cooling time at the time of bending, and has poor productivity. Moreover, the resin tube concerning the latter prior art had the subject that not only the manufacturing process for forming a bellows part became complicated, but flow resistance became large in the location of a bellows part.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a fuel tube is provided. The fuel tube has an inner layer forming a fuel passage and an outer layer laminated on the outer peripheral side of the inner layer. In the bent fuel tube, the outer layer is a polyamide selected from PA11, PA12 or PA1012 The inner layer is formed of a polyamide-based second resin material of PA612, the melting point of the first resin material is Tm1, the melting point of the second resin material is Tm2, and the first layer is made of the first resin material. When the glass transition point of one resin material is Tg1 and the glass transition point of the second resin material is Tg2, Tm2-Tm1 is 10-30 ° C. and Tg2-Tg1 is 10-30 ° C. It is a fuel tube.
Since the outer layer of the fuel tube is made of a polyamide-based first resin material selected from PA11, PA12, or PA1012, it satisfies the specifications as a fuel tube such as calcium chloride resistance and assembly property. Further, since the inner layer is formed of the second resin material having a melting point Tm2 higher than the melting point Tm1 of the first resin material of the outer layer, the inner layer is heated to a set temperature close to the melting point Tm1 of the first resin material during the bending heating. Even so, it retains the shape of the tube intermediate. Therefore, the tube intermediate can be bent without buckling. The heating set temperature at the time of bending the fuel tube can be increased, and the heating time can be shortened.

  In the manufacture of the fuel tube, if the temperature is slightly lower than the glass transition point Tg2 of the second resin material of the inner layer during the cooling of the bending process, even if the outer layer formed from the first resin material is somewhat soft, an early stage Since the cooling process can be completed at, the cooling time can be shortened.

(2) In the fuel tube of the above aspect, when the inner diameter of the fuel passage is set to 5.8 to 6.2 mm and the wall thickness of the fuel tube is set to 0.8 to 1.2 mm, respectively, The thickness may be set to 0.3 to 0.7 mm, and the thickness of the outer layer may be set to 0.5 to 0.7 mm.

(3) Another embodiment is a method of manufacturing a fuel tube, and by extruding the first and second resin materials, a tube intermediate body in which the inner layer and the outer layer are laminated is formed. A fuel characterized in that after being heated by a heater set at a temperature close to Tm1 and not exceeding Tm1, bending is performed, and then the tube intermediate is taken out in a temperature range of Tg2-10 ° C. It is a manufacturing method of a tube.

It is the perspective view which fractured | ruptured the fuel tube concerning one embodiment of this invention partially. It is sectional drawing of a fuel tube. It is explanatory drawing explaining the resin material of an outer layer and an inner layer. It is explanatory drawing explaining the heat processing and cooling processing at the time of performing a bending process to a fuel tube. It is explanatory drawing explaining structures, such as the thickness of a fuel tube.

(1) Overview of Fuel Tube 10 FIG. 1 is a perspective view in which the fuel tube 10 according to an embodiment of the present invention is partially broken, and FIG. 2 is a cross-sectional view of the fuel tube 10. The fuel tube 10 is routed in the engine room and used in a piping path between a fuel pump arranged in the fuel tank and a fuel injection valve of the engine. The fuel tube 10 has an inner layer 12 that forms a fuel passage 10P and an outer layer 14 that is laminated on the outer peripheral side of the inner layer 12, and is bent into a predetermined bent shape by being bent. .

  The specifications for connecting the fuel tube 10 between the fuel pump and the engine include heat resistance (maximum temperature: 100 ° C.), pressure resistance (maximum pressure: 0.5 MPa), bending elasticity, calcium chloride resistance, and the like. In addition to satisfying the conditions, bending is performed along a predetermined path to route the engine room. These specifications are appropriately changed according to the engine performance of each vehicle and the location of the vehicle.

  The fuel tube 10 is manufactured by performing an extrusion process and a bending process. In order to manufacture the fuel tube 10, first, the molten second resin material and the first resin material for forming the inner layer 12 and the outer layer 14 are extruded on the same axis and laminated using a general-purpose tube extrusion device. Thus, the tube intermediate is manufactured. Next, the tube intermediate is bent. In the bending process, after heating to a predetermined first temperature, the tube intermediate is cooled to a predetermined second temperature or less by bending along a path defined by a jig and flowing air or the like through the tube intermediate. It is done by. Thereby, the fuel tube 10 is obtained.

(2) Configuration of Fuel Tube 10 The fuel tube 10 has the following configuration with respect to the resin material and shape in order to satisfy the above-described specifications and efficiently realize the manufacture. FIG. 3 is an explanatory diagram for explaining the resin material of the outer layer and the inner layer, and shows a comparative example corresponding to the conventional technique together with an example.

  As shown in FIG. 3, the resin material of the fuel tube 10 is selected based on factors such as melting point, glass transition point, flexural elasticity, and calcium chloride resistance. Here, the melting point refers to a temperature at which the crystalline part is broken by heating and heating of the crystalline polymer and exhibits fluidity. The glass transition point is a temperature at which a non-crystalline portion transitions from a glass state having low molecular mobility to a rubber state in which the mobility is increased. The bending elasticity represents the hardness of the fuel tube and is an index of a load necessary for bending. The calcium chloride resistance refers to resistance to calcium chloride contained in a snow melting agent or the like.

(3) Selection of Resin Material for Fuel Tube 10 In FIG. 3, in the comparative example corresponding to the prior art, PA 11 (or PA 12) is formed as a single layer, whereas in the embodiment, the outer layer 14 and Different resin materials are used for the inner layer 12.
For the outer layer 14, a resin material similar to that of the above-described comparative example, that is, a polyamide-based first resin material selected from PA11, PA12, or PA1012 can be used. The outer layer 14 is selected as a resin material that mainly satisfies the specifications of the fuel tube 10 such as calcium chloride resistance and assemblability.

  For the inner layer, a polyamide-based second resin material of PA612 is used. PA612 is selected as a resin material having fuel resistance against the fuel flowing through the fuel passage. PA 612 is selected as a resin material that satisfies the temperature conditions during the bending process and can shorten the heating and cooling time.

FIGS. 4A and 4B are explanatory diagrams for explaining the heat treatment when the fuel tube is subjected to a bending process, in which FIG. 4A shows the temperature raising process and FIG. 4B shows the cooling process. In FIG. 4, a solid line shows an Example and a broken line shows a comparative example. In the temperature on the vertical axis, Tm1 in FIG. 4A represents the melting point of the outer layer resin material, and Tm2 represents the melting point of the inner layer resin material. In FIG. 4B, Tg1 represents the glass transition point of the resin material of the outer layer, and Tg2 represents the glass transition point of the resin material of the inner layer.
In the bending process shown in FIG. 4A, the tube intermediate is heated from the time th0 when heating is started to a temperature close to the melting point Tm1 of the resin material of the outer layer (first temperature). Thereby, the tube intermediate body obtains the flexibility that can be bent. Then, the heated tube intermediate is bent along a predetermined path. Thereafter, as shown in FIG. 4B, the tube intermediate is cooled to a temperature (second temperature) that is not higher than the glass transition point Tg2 of the inner layer. Thereby, a fuel tube is obtained.

Here, in the horizontal axis of FIG. 4A, among the heating time until the tube intermediate reaches the bending temperature, the heating time of the example is th (a), and the heating time of the comparative example is th (b). Then, th (a) <th (b). Thus, the reason why the heating time th (a) of the example can be made shorter than the heating time th (b) of the comparative example by Δth is as follows.
In this example, the melting point Tm2 of the inner layer resin material (PA612) is 198 ° C., which is higher than the melting point Tm1 (180 ° C., 185 ° C.) of the outer layer resin material (PA11, PA1012). For this reason, even when the tube intermediate is heated to near the melting point Tm1 of PA11 and the outer layer is softened, the shape retaining function of the inner layer is great. In other words, the inner layer adds a characteristic that does not break its shape even when it is bent at a temperature close to the melting point Tm1 (first temperature). By utilizing this characteristic, the temperature rise rate of the tube intermediate is increased by increasing the set temperature of the heater for heating the tube intermediate as described above.
On the other hand, since the tube intermediate of the comparative example is formed only from the same resin material (PA11) as the outer layer of the example, the tube intermediate is liable to be crushed when being close to the melting point Tm1. For this reason, the set temperature of the heater has to be set to a temperature lower than that of the embodiment, and the temperature rise rate becomes small.
Therefore, when the tube intermediate is heated by the heater, the heater set temperature [Tm1-TΔ (actual)] in the example is equal to the heater set temperature [Tm1-ΔT in the comparative example. (Ratio)] By setting the temperature higher, the rate of temperature rise increases, and the heating time to the bending temperature can be greatly shortened.
Moreover, since the heater for heating the tube intermediate can use a simple device such as a thermostatic chamber with a constant temperature, the equipment can be simplified.

Here, Tm2−Tm1 is preferably 10 to 30 ° C. This is because when the temperature is lower than 10 ° C., the shape retaining function of the inner layer described above cannot be obtained. When the temperature exceeds 30 ° C., the difference in melting point between the inner layer and the outer layer becomes large, and even if the resin in the outer layer becomes sufficiently soft at a temperature near Tm1, the resin in the inner layer is at a very low temperature from the melting point. This is because the bending is performed at a temperature not suitable for bending, and a problem such as failure to obtain a desired bending dimension or bending occurs.
The heater temperature is preferably set to a temperature close to Tm1 of the tube intermediate and not exceeding Tm1. This is because if the temperature is significantly lower than Tm1, it does not contribute to shortening the heating time, and if it exceeds Tm1, the resin in the outer layer melts and the fuel tube does not form.

In the horizontal axis of FIG. 4B, if the cooling time of the example is tc (a) and the cooling time tc (b) of the comparative example among the time required to cool the tube intermediate, tc (a) <Tc (b). In the cooling process of FIG. 4B, the time point tc0 at which the cooling is started is illustrated from the time point when the same bending process is completed in the example and the comparative example. Therefore, when viewed from the start time th0 of the processing step in FIG. 4A, the example starts earlier than the heating time th0 in FIG. 4A than the comparative example.
Hereinafter, the reason why the cooling time tc (a) of the embodiment can be made shorter than the cooling time tc (b) of the comparative example by Δtc will be described.
In an Example, the glass transition point Tg2 of the resin material (PA612) of an inner layer is 62 degreeC, and is higher than the glass transition point Tg1 (46 degreeC, 50 degreeC) of the resin material (PA11, PA1012) of an outer layer. For this reason, when the tube intermediate is cooled to a temperature lower than the glass transition point Tg2 of the inner layer, the inner layer has already enhanced the shape maintaining function even if the outer layer is still soft. That is, the tube intermediate body has a characteristic that the inner layer does not lose its shape even if it is removed from the state after the bending process. By utilizing this characteristic, the fuel tube 10 can be taken out if it falls below the glass transition point Tg2 (62 ° C.) of the resin material of the inner layer.
On the other hand, since the tube intermediate of the comparative example is formed only of the same resin material (PA11) as the outer layer of the example, the tube intermediate cannot be taken out unless it falls below the glass transition point Tg1 (46 ° C.). .
Therefore, since the glass transition point Tg2 of the resin material used for the inner layer of the example is higher than the glass transition point Tg1 of the resin material of the comparative example, the fuel tube of the example has a shorter cooling time than the comparative example. However, it can be taken out, that is, the cooling time can be shortened from 70 seconds to 30 seconds.

Here, it is preferable that Tg2-Tg1 is 10-30 degreeC. This is because if the temperature is lower than 10 ° C., the shape retaining function of the inner layer described above cannot be obtained, and if it exceeds 30 ° C., the resin of the outer layer is still too soft and is used as a jig in the bending process. This is because the surface is deformed or a defect such as a scratch occurs due to contact.
Moreover, it is preferable to set the temperature which takes out a tube intermediate body to 10-30 degreeC temperature lower than Tg2 of a tube intermediate body. This is because if the temperature is less than 10 ° C., the inner layer does not sufficiently exhibit the shape retention function, and if it exceeds 30 ° C., it does not contribute to shortening the cooling time.

(4) Shape of Fuel Tube 10 FIG. 5 is an explanatory diagram for explaining the structure of the fuel tube 10 such as the wall thickness. As shown in Sample 1 to Sample 6 in FIG. 5, the fuel tube 10 has a fuel passage 10 </ b> P having an inner diameter of 5.8 to 6.2 mm and a wall thickness of 0.8 to 1.2 mm. The thickness of the inner layer 12 can be set to 0.3 to 0.7 mm, and the thickness of the outer layer 14 can be set to 0.5 to 0.7 mm.

The reason why each thickness is set as described above is as follows. The fuel tube 10 is determined in consideration of its bending elasticity because the inner layer 12 needs to fulfill the function of shape retention during bending as described above. Further, when the fuel tube 10 is connected to the engine, if the bending elasticity of the fuel tube 10 is small and too soft, the fuel tube 10 vibrates by driving the engine, and the connection is easily loosened. Further, if the bending elasticity of the fuel tube 10 is too large and too hard, stress is applied to a part and the fuel tube 10 is easily broken. In consideration of these factors, the lower limit value and the upper limit value of the flexural elasticity can be determined.
The value of bending elasticity can be obtained by the following experiment. When both ends of a sample formed with the same outer diameter as the inner layer of the straight fuel tube are supported by a jig and a load is applied to the center of the sample, the load can be obtained when a predetermined displacement is reached. . For example, the bending elasticity is preferably set in the range of 18N to 30N. Therefore, as shown in FIG. 5, the thickness of the fuel tube 10 is determined as described above.

(5) According to the configuration of the above embodiment, the following actions and effects can be obtained.
(5) -1 The outer layer 14 of the fuel tube 10 is formed of a polyamide-based resin material selected from PA11, PA12, or PA1012, so that the specifications as the fuel tube 10 such as calcium chloride resistance and assembling property are satisfied. Fulfill.

(5) -2 The inner layer 12 of the fuel tube 10 has a large shape maintaining function even when the heater set temperature during bending heating is higher than that of the conventional technique, so that the fuel tube 10 does not buckle, Bending can be performed. Therefore, the heating setting temperature at the time of bending of the fuel tube 10 can be increased, and the heating time can be shortened.

(5) -3 The inner layer 12 of the fuel tube 10 can obtain the function of maintaining the shape by the inner layer 12 at a temperature higher than that of the prior art when cooling the bending process. Therefore, the fuel tube 10 can be removed from the bending jig from an early stage, and the cooling time can be shortened.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof.

10 ... Fuel tube 10P ... Fuel passage 12 ... Inner layer 14 ... Outer layer

Claims (3)

In a fuel tube having an inner layer that forms a fuel passage and an outer layer that is laminated on the outer peripheral side of the inner layer,
The outer layer is formed of a polyamide-based first resin material selected from PA11, PA12, or PA1012.
The inner layer is formed from a polyamide-based second resin material of PA612,
The melting point of the first resin material is Tm1, the melting point of the second resin material is Tm2, the glass transition point of the first resin material is Tg1, and the glass transition point of the second resin material is Tg2.
Tm2-Tm1 is 10-30 ° C, Tg2-Tg1 is 10-30 ° C,
A fuel tube characterized by The fuel tube of claim 1, wherein
In the fuel tube, when the inner diameter of the fuel passage is set to 5.8 to 6.2 mm and the thickness of the fuel tube is set to 0.8 to 1.2 mm, the inner layer has a thickness of 0.3 mm. A fuel tube in which the thickness of the outer layer is set to 0.5 to 0.7 mm. A method of manufacturing a fuel tube according to claim 1 or claim 2,
By extruding the first and second resin materials, a tube intermediate in which the inner layer and the outer layer are laminated is formed,
Bending the tube intermediate after heating it with a heater set at a temperature close to Tm1 and not exceeding Tm1, and then taking out the tube intermediate in a temperature range of Tg2-10 ° C .;
A fuel tube manufacturing method characterized by the above.

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