JP5947491B2 - Fuel injection rail - Google Patents

Description

  The present invention relates to a fuel injection rail for use in an automobile engine, and more particularly to a fuel injection rail designed to improve the performance of absorbing fuel pressure fluctuations accompanying opening and closing of an injector and the durability against high pressure.

  In a fuel supply system in an automobile engine, fuel in a fuel tank is sent to a fuel injection rail by a pump, and an appropriate amount of fuel is injected into an intake manifold of the engine by an injector attached to the fuel injection rail.

In such fuel injection rails, there are problems such as fuel pulsation, vibration, and abnormal noise generated by the opening and closing operation of the valve due to the injection action of the injector.
Conventionally, in order to cope with such pulsations and vibrations, an external damper has been provided or a damper means has been built in the fuel injection rail. However, the structure becomes complicated. Recently, the fuel injection rail itself tends to absorb the pulsation and vibration because the weight is increased and the cost is increased.

  In order to absorb the pulsation, it is necessary to make the fuel injection rail itself deformable and to increase the deformation amount (damping amount). In order to increase the amount of damping, the plate thickness of the fuel injection rail is uniformly reduced, or the cross-sectional shape and dimensions are easily deformed to reduce the surface rigidity of the damping part.

As such, for example, by forming the cross-sectional shape of the fuel delivery pipe into an unequal side triangle with a constant thickness, and making the longest side part of this unequal side triangle a flexible absorber surface to cause a damping action In order to absorb the pulsation and vibration, there has been proposed (Patent Document 1).
In this case, when the surface rigidity is lowered and the cross-sectional area (internal volume) is increased, the stress applied to the fuel injection rail also increases.

JP 2002-295338 A

In order for the main body of the fuel injection rail itself to absorb the above pulsation and vibration, the fuel injection rail main body is deformed (damped) with fluctuations in pressure to absorb the pulsation and vibration, and is applied at the time of deformation. It is effective to apply the stress as small as possible and on average.
As mentioned above, in order to make it easier to absorb pulsation and vibration by damping, it is an effective means to reduce the thickness of the main body of the fuel injection rail, but it is easy to reduce the thickness and perform damping. It has also been found that if this is facilitated, the stress on the main body of the fuel injection rail may increase, leading to fatigue failure.

  The present invention eliminates such problems and makes it easier to absorb pulsation and vibration, reduces the generation of stress on the main body of the fuel injection rail, and improves the strength against high pressure. It is intended to provide a fuel injection rail.

The present invention relates to a pipe-shaped fuel injection rail having a fuel flow passage formed therein, the cross-sectional shape of which is a polygonal shape, and at least one of the sides forming the cross-sectional multi-sided shape is a longitudinal direction of the pipe A thin-walled portion having a small thickness and a thick-walled portion having a large thickness.
And in at least one side of the side forming the multi-sided cross-sectional shape of the pipe, the thin portion is formed on both sides of the side, and the thick portion is formed in a central portion sandwiched between the thin portions. Like that.

Such a thin part and a thick part are formed toward the inner surface side of the pipe, or are formed toward the outer surface side of the pipe.
When the cross section of the pipe is formed in a multi-sided shape, the thin wall portion and the thick wall portion are formed on the two sides facing each other.

  The above pipes include casting, cutting, drawing, press fitting, extrusion molding, injection molding (including gas assist injection molding, water assist injection molding, projectile injection molding, etc.), blow molding, cast molding, etc. It may be formed by any method, and the pipe material may be formed of a heat-resistant material such as a metal, a thermoplastic resin, or a thermosetting resin.

  According to the present invention, it is possible to effectively absorb fuel pulsation, vibration, and the like that are generated by opening and closing operations of the valve due to the injection action of the injector, and to reduce the generation of stress on the main body of the fuel injection rail. In addition, the fuel injection rail can function stably over a long period of time.

It is a partially-omission perspective view of the fuel injection rail which shows the Example of this invention. It is sectional drawing which shows the other example of this invention. It is sectional drawing which shows the other example of this invention. It is sectional drawing which shows the other example of this invention. It is sectional drawing which shows the further another example of this invention. It is explanatory drawing which displayed the dimension when what was shown in FIG. 1 was used for a test. It is explanatory drawing which showed the cross section of the comparative example used for the test, and displayed the dimension. It is a graph which shows the result of a stress distribution test. It is a scatter chart that categorizes the relationship between the wall thickness ratio (thick part / thin part) and the change in cross-sectional area (ΔS) according to the stress ratio between the maximum internal stress and the maximum external stress on the inner and outer surfaces. .

The fuel injection rail (1) in the present invention is formed in a pipe shape, and the inside of the pipe is a fuel flow path (2). The pipe of this fuel injection rail has a cross-sectional shape of a triangle, a quadrilateral, a pentagon, and other multi-sided shapes. In this case, even if one or more sides of the multi-sided shape draw an arc, it is included in the multi-sided shape of the present invention.
Each side forming the multi-sided shape has a thickness (3) for forming a pipe, and at least at one side, the thin-walled portion (4) having a small thickness and the thickness is large. A thick part (5) is formed, which is continuous along the longitudinal direction of the pipe.

The fuel injection rail (1) shown in FIG. 1 is formed in a rectangular shape having a four-sided cross section, and a thin part (4) and a thick part (5) are formed on two opposing long sides (6). Is formed.
The said thin part (4) is formed in the both sides of a long side (6), and the thick part (5) is formed in the center part pinched | interposed into the said both thin part (4).

The thin-walled portion (4) and the thick-walled portion (5) are provided so as to form irregularities toward the flow path (2) side of the inner surface of the pipe, and the inner surface of the pipe has one thin-walled portion ( It is formed so as to draw a gentle curve from 4) through the thick part (5) to the other thin part (4).
Two opposing short sides (7) of the rectangular cross section of the pipe are formed to have a uniform wall thickness, and are formed to be thicker than the long side (6).

The inner surface (8) of the corner of the pipe where the long side (6) and the short side (7) intersect is preferably formed so as to draw an arc, and the radius of the arc may be 1 or more. Then, the radius is set to about 5.
The ratio of the thickness of the thick part and the thickness of the thin part is preferably (thick part / thin part), preferably 1.25 or more, more preferably 1.5 or more. . The thickness ratio is preferably less than 2.5, more preferably less than 2.0.

Such fuel injection rails (1) are steel, stainless steel, aluminum and other metals, polyamide 11 (PA11), polyamide 12 (PA12), polyamide 66 (PA66), polyamide 6T (PA6T), polyamide 9T (PA9T), It can be produced using resins such as polyphenylene sulfide (PPS) and other thermoplastic resins, urea resins, polyester resins and other thermosetting resins.
Such materials preferably have appropriate strength, heat resistance, and imperviousness of fuel entering the flow path in the pipe, and if necessary, can be reinforced with glass fiber, carbon fiber, etc. The effect and the like can be improved.

  This fuel injection rail (1) can be formed by various methods using the above-mentioned various materials. In the case of metal, it is formed by, for example, fitting of cast, cut, drawn, or press-worked parts. In the case of resin, for example, it is convenient to form by extrusion molding, injection molding (including gas assist injection molding, water assist injection molding, projectile injection molding, etc.), blow molding, cast molding, etc. There are many cases.

  When fuel flows into the flow path (2) of the fuel injection rail (1) and fuel pulsation occurs as the valve opens and closes due to the injection action of the injector, this reaches the fuel injection rail. The pulsation mainly acts on the thin part (4) where the long side (6) of the pipe is thin and the thick part (5) of the central part of the long side (6), and the thickness of the central part of the long side (6). Starting from the thin part (4) on both sides of the meat part (5), the thick part (5) at the center of the long side is pushed outward to increase the cross-sectional area in the flow path (2), At the same time, the volume of the flow path (2) is increased and then returned to the original, so that a large damping effect can be obtained.

2 shows that the thin wall portion (4) and the thick wall portion (5) provided on the long side (6) of the fuel injection rail (1) are formed toward the outer surface (9) side of the pipe. 3 , the thin portion (4) and the thick portion (5) provided on the long side (6) are formed facing the outside of the pipe, and the entire long side (6) is formed outside the pipe. It is made to curve toward the direction.

The thing of FIG. 4 makes the bottom part (21) uniform thickness of the fuel injection rail (1) which formed the external shape of the cross section in the shape of a triangle, and is the center part of the inner surface side of two sides (22) which oppose in an inclined state The thick wall portion (5) is left and the thin wall portions (4) are formed on both sides.

In the case of FIG. 5 , the section is formed in a rectangular shape in the same manner as shown in FIG. 1, but the central part is placed on the long side (23) of one of the two long sides facing (right side in the figure). On the thick part (5), both sides are formed into a thin part (4), and on the other side (left side in the figure), the lower part of the long side (24) has a large protruding part (25) toward the outside. The upper corner portion is formed into a thin portion (4) and the other is formed into a thick portion (5) so as to be continuous with the uniform bottom portion (27).

[CAE analysis evaluation]
In order to see the performance of the fuel injection rail of the above example, the following evaluation model shapes were prepared, CAE (Computer Aided Engineering) analysis was performed, and the following evaluation was performed.

(Evaluation model shape)
The following models were prepared as evaluation model shapes.
1. Example 1 is the fuel injection rail shown in FIG. 1, and as shown in FIG. 6 , the dimensions of the respective sections are as follows.
H1 = 34.4mm, H2 = 25.4mm, W1 = 22.4mm
t1, t2 = 4.5mm, t3 = 2.1mm, t4 = 3.5mm
R1 = 5mm, W2 = 13.5mm
R2 is an arc drawn with R being 17 mm around the point where W2 = 13.5 mm and the center line of H1 intersect.
2. The comparative example 1 is a fuel injection rail shown in FIG. 7, and the dimensions of the cross-section parts are as follows.
H11 = 34.4mm, H12 = 26.3mm, W11 = 22.4mm
t11, t12, t13, t14 = 4.05mm,
R11 = 0.95mm, R12 = 5mm

[Stress distribution evaluation]
Example in which the length factor of the pipe of the fuel injection rail of Example 1 and Comparative Example 1 is deleted, and the cross-sectional area (S) is increased by 0.8 mm ² by applying an internal pressure of 350 kPa to the pipe. The maximum principal stress applied to the inner surface and the outer surface of the long side in each portion from the lower end to the upper end of the long side (6) of 1 and the long side (16) of Comparative Example 1 was measured.

(result)
The results of the stress distribution evaluation are shown in FIG. FIG. 8 shows the value of the higher stress applied to the inner surface and the outer surface. The stress on the inner surface is high on both sides of the long side, and the stress on the outer surface is high in the center.

[Wall thickness ratio evaluation]
When the pipe length factor of the fuel injection rail of Example 1 was deleted and the thickness of the thick part t4 and the thin part t3 was changed and a pressure of 350 kPa was applied to the pipe (thick part t4 / thin part). For the relationship between the wall thickness ratio of part t3) and the cross-sectional area variation (ΔS), create a scatter diagram by categorizing it according to the stress ratio between the maximum inner surface main stress and the maximum outer surface main stress generated on the inner and outer surfaces. evaluated. The stress ratio is in the range of 0-1.

(result)
The results of scatter diagram shown in Fig. In FIG. 9,
1. The symbol A indicates that the stress ratio of each maximum principal stress between the inner surface and the outer surface is less than 0.85 to 0.90.
2. Symbols b to h indicate those in which the stress ratio of each maximum principal stress between the inner surface and the outer surface is 0.90 to less than 1.0,
b has a thickness ratio (thick portion t4 / thin portion t3) of less than 1.00 to 1.25,
c is less than 1.25 to 1.50,
d is less than 1.50 to less than 1.75,
e is less than 1.75 to 2.00
f is less than 2.00 to less than 2.25,
g is less than 2.25 to 2.50,
h shows the thing below 2.50-2.75.

[Evaluation of increase in cross-sectional area]
When the pipe length factor of the fuel injection rail of Example 1 was deleted, and the dimensions t3, t4, R1, R2, and W2 were changed and a pressure of 350 kPa was applied to the pipe, the long side H2 t3 (thin wall) Part) and t4 (thick wall part), the stress generated in the pipe cross section, and the increase in the pipe cross sectional area were evaluated by a statistical method using a correlation matrix.

(result)
Table 1 shows the correlation matrix results of the cross-sectional area increase evaluation in terms of ratios.

[Discussion]
According to the above stress distribution evaluation, as shown in FIG. 8 , in the case of the uniform-thickness quadrilateral shape of Comparative Example 1, the maximum stress of 14 MPa is applied to the inner R located at both end portions of the long side, and the stress concentration The stress is reduced to about 1 MPa slightly inside, and then the stress is unevenly distributed such that the stress of 8 MPa is concentrated toward the center of the long side.
On the other hand, in Example 1, a stress of 8 MPa or more is applied to both end portions of the long side, the stress is reduced to about 2 MPa slightly inside, and then the average value of 8 MPa is averaged over a wide range in the central portion of the long side. It can be seen that weak stress is applied, the stress is small as a whole, and the stress is dispersed on the entire long side on average. Therefore, when the stress requirements are the same as in Comparative Example 1, the change in cross-sectional area (ΔS) is larger in Example 1 in which the stress ratio between the inner surface maximum principal stress on the inner and outer surfaces and the outer surface maximum principal stress is close to 1. Can do.
Further, as shown in FIG. 8 , a uniform thickness shape having a thickness ratio of 1 as in Comparative Example 1 has a high stress value, so it cannot be an optimal solution for cross-sectional area change (ΔS). . According to the wall thickness ratio evaluation, as shown in FIG. 9 , the optimum solution (10) is such that the stress ratio of each maximum principal stress between the inner surface and the outer surface is 0.90 or more, and the wall thickness ratio is 1.5 to 1. In order to approximate this optimum solution, the stress ratio of the maximum principal stresses of the inner surface and the outer surface should be 0.85 or more and the wall thickness ratio should be 1.25 or more, preferably It can be seen that the stress ratio of each maximum principal stress between the inner surface and the outer surface should be 0.90 or more and the wall thickness ratio should be 1.50 or more.
Further, in the evaluation of the increase in the cross-sectional area, as shown in Table 1, in Example 1, the stress and ΔS have the same correlation in the dimensional change of the thin part, but in the dimensional change of the thick part. Has a relatively large change in ΔS with respect to the stress, and has less influence on the stress than the change in ΔS. Therefore, by forming the thin wall portion and the thick wall portion in the cross section, ΔS can be increased when the same stress is applied, so that the cross sectional area in the pipe is increased in the place where the same stress is applied. It was found that a good damping effect can be obtained.

1: Fuel Injection rail 2: the flow path 3: thickness 4: the thin portion 5: thick-walled portion 6: long side 7: short side 8: corner inner surface 9: optimum solution in Figure 9: the outer surface 10

Claims (7)

A pipe-like fuel injection rail having a polygonal cross-sectional shape and a fuel flow passage formed therein, wherein at least one side of the pipe forming the cross-sectional polygonal shape is along a longitudinal direction of the pipe A thin portion having a thin thickness on both sides of the side and a thick portion having a thick thickness at the center portion sandwiched between the thin portions, and a thickness ratio of the thin portion and the thick portion (thick portion / (Thin wall portion) is 1.5 or more and less than 1.75, and when the pipe is subjected to internal pressure, the stress ratio of the inner surface maximum principal stress and the outer surface maximum principal stress is 0.90 or more and less than 1.0. A fuel injection rail characterized in that a change in cross-sectional area (ΔS) when an internal pressure of 350 kPa is applied exceeds about 1.3 .   The fuel injection rail according to claim 1, wherein the thin portion and the thick portion are formed toward the inner surface side of the pipe.   The fuel injection rail according to claim 1, wherein the thin portion and the thick portion are formed toward the outer surface side of the pipe.   The fuel injection rail according to any one of claims 1 to 3, wherein the pipe is formed in a multi-sided cross-section, and the thin portion and the thick portion are formed on two opposite sides, respectively.   The fuel injection rail according to any one of claims 1 to 3, wherein the pipe is formed in a multi-sided cross-sectional shape, and the thin-walled portion and the thick-walled portion are formed on all of the constituent sides.   The fuel injection according to any one of claims 1 to 5, wherein the pipe is formed in a multi-sided cross section, the inner surface of the pipe where each side intersects is formed in an arc shape, and R of the arc is formed in one or more. rail.   The fuel injection rail according to any one of claims 1 to 6, wherein the pipe is formed of any one of heat-resistant materials selected from metals, thermoplastic resins, and thermosetting resins.

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