The present invention relates to a fuel rail for supplying a high-pressure fuel to an injector.
In a gasoline engine in which gasoline is used as a fuel, a fuel pressure to be supplied to a fuel injection valve is recently highly pressurized. Conventionally, a fuel rail described in JP 2013-199943 A (PTL 1) is known as a fuel rail in which a fuel injection valve is mounted and which supplies fuel to the fuel injection valve. The fuel rail described in PTL 1 includes an injector holder assembly including an injector cup to assemble a fuel injection valve. The injector cup includes a housing in which an inner space is included, and one end is opened (refer to paragraph 0025). This injector cup is made of a member different from the fuel rail (refer to
On the other hand, a common rail to be used in a diesel engine is described in JP 2007-146725 A (PTL 2). An outer dimension of the common rail described in PTL 2 is same as a conventional dimension. An inner dimension or an accumulator hole is divided into a small diameter portion and a large diameter portion, and a cross hole opened on an inner peripheral surface of the accumulator hole is provided in the small diameter portion (refer to Abstract). In the common rail, a minimum thickness of the cross hole portion can be increased by which a cross hole is opened in the small diameter portion, and a rail damage can be avoided (refer to Abstract). On the other hand, an accumulation volume decreased in the small diameter portion is covered by the large diameter portion. Therefore, a total volume of the accumulator hole is not decreased (refer to Abstract). Further, in the common rail in PTL 2, a rail body, a piping joint, and a stay 22 are integrally molded by forging. The piping joint connects a high pressure pump piping and an injector piping. The stay 22 mounts the rail body to a fixing member of such as engine (refer to paragraph 0035). In the common rail in PTL 2, a high pressure pump piping or an injector piping is connected to one end portion of an inside/outside communication hole formed at a center of the piping joint, and another end portion of the inside/outside communication hole is communicated to a cross hole.
PTL 1: JP 2013-199943 A
PTL 2: JP 2007-146775 A
In a fuel rail described in PTL 1, an injector cup is made of a material different from the fuel rail and joined to the rail by such as brazing. A large stress is generated by a fuel pressure at a joint between the injector cup and the fuel rail. As a fuel pressure is highly pressurized, a stress generated at the joint is increased, and the joint does not have a sufficient strength to withstand the stress. Therefore, in fuel rail is which an injector cup is joined, a high pressurization is limited at a relatively low fuel pressure. On the other hand, in the common rail in PTL 2, a rail body and a piping joint are integrally molded by forging, and therefore the common rail is advantageous to increase a fuel pressure. Especially, in the common rail in PTL 2, a minimum thickness of a cross hole portion is increased by which a cross hole is opened in a small diameter portion in which a wall thickness is increased by reducing an inner diameter of an accumulator hole. As a result, the common rail in PTL 2 prevents that a rail is damaged from a cross hole portion even if stress concentration is generated at the cross hole portion by accumulation of an ultra high pressure fuel. However, the common rail in PTL 2 has an issue that the weight of a rail body is increased since a wail thickness of the railbody is increased. In PTL 2, is issue is not sufficiently considered.
An object of the present invention is to provide a fuel rail for an internal combustion engine, which can increase the strength of a cross-hole portion and realize weight reduction.
To achieve the above-described object, in a fuel rail for an internal combustion engine according to the present invention, a fuel rail body and an injector mounting portion (injector cup) in which an injector is mounted are integrally molded, and the thickness of a root portion of the injector cup with respect to the fuel rail body is set to be thicker than the thickness of a fuel rail body portion in which the injector cup is formed.
According to the present invention, the wall thickness of a root portion of the injector mounting portion is set to be thicker than the wall thickness of a fuel rail body portion in which an injector cup is formed. Accordingly, while increasing the strength of a portion where a hole formed in an injector mounting portion and a hole formed in a fuel rail body are crossed, weight reduction of a fuel rail for an internal combustion engine can be realized.
An issue, a configuration, and an effect other than the above are clarified descriptions of the following embodiment.
An embodiment of the present invention will be described below.
First, a fuel supply system of a direct-injection internal combustion engine in which a fuel rail for an internal combustion engine according to the present invention (hereinafter called a fuel rail) will be described with reference to
A spark plug 23 starts fuel combustion in a combustion chamber 26 and drives a piston 25 reciprocably mounted to a cylinder 27 in the engine block 24. Combustion products by fuel combustion is discharged from an exhaust manifold.
A direct injection injector (fuel injection valve) 28 is provided in each combustion chamber 26. Each fuel injection valve 28 is mounted to a passage (through hole) 30 formed to the engine block 24, and a nozzle tip portion in which a fuel injection hole is formed faces the combustion chamber 26.
The injector 28 is fluidally connected to a fuel rail 32. The fuel rail 32 is fluidally connected to a high-pressure fuel pump 36 via a fuel pipe 34. The high-pressure fuel pump 36 generally includes a cam pump including a cam 38 rotated by an engine. Further, the fuel rail 32 is fixed to the engine block 24 via a bracket (not illustrated).
Next, a fuel rail will be described with reference to
The fuel rail 32 includes the fuel rail body 1, the injector cup (injector receiving portion) 2, and an inlet 8. The injector cup 2 is disposed so as to project in a vertical direction from the fuel rail body 1 to the center line 1cl. The inlet 8 is connected to the pipe 34 extending from the high-pressure fuel pump 36.
In the fuel rail body 1, a plurality of injector cups 2 is formed in the center line 1cl direction of the fuel rail body 1 with intervals between adjacent injector cups. In the embodiment, four injector cups 2 are disposed, and the injector cups 2 are disposed at equal intervals. A center hole 1a having a circular cross-section surface is formed at a center portion of the fuel rail body 1 from one end portion along the center line 1cl direction. In the fuel rail body 1, outer peripheral surfaces of a middle portion and both end portions of two adjacent injector cups 2 have a circular shape and are formed as a substantially cylindrical member by forming the center hole 1a. The center hole is included in an accumulator for storing high-pressure fuel sent from the high-pressure fuel pump 36 and distributes the fuel stored in the accumulator to a plurality of the injectors 28 (four injectors in the embodiment).
The center hole 1a is formed along, the center line 1cl direction from one end portion of the fuel rail body 1. However, the center hole 1a does not penetrate to another end portion. The inlet 8 is formed at the end portion on a side where the center hole 1a of the fuel rail body 1 does not penetrate. In the inlet 8, a fuel introduction hole 8a is formed by which a high-pressure fuel sent from the high-pressure fuel pump 36 is introduced into the accumulator 1a.
A pressure sensor (not illustrated) is provided at an end portion on a side where the center hole 1a of the fuel rail body 1 opens.
The injector cup 2 is a receiving portion of the injector 28 in which the injector 28 is mounted. An opening portion 2b to insert the injector 28 is formed on a tip surface 2a of the injector cup 2. On an inner side of the opening portion 2b, a receiving groove 2c which receives a locking portion disposed on the injector 28 side is formed. On an inner side of the receiving groove 2c, an inside/outside communication holes 2d are formed which communicates with the center hole (accumulator) 1a of the fuel rail body via the opening portion 2b and the receiving groove 2c.
The inside/outside communication hole 2d is formed as a hole having a circular cross-section surface and is formed in a direction vertical to the center hole 1a and the center line 1cl. The inside/outside communication hole 2d vertically crosses the center hole 1a and therefore may be called a cross hole 2d. An extension line of a center line of the inside/outside communication hole 2d (same as the center line 2cl of the injector cup 2) preferably crosses the center line 1cl of the center hole 1a. However, the extension line may not cross the center line 1cl. However, in the ease where the extension line of the center line of the inside/outside communication hole 2d is too apart from the center line 1cl of the center hole 1a, a strength of the fuel rail 32 might be reduced. Therefore, the extension line is preferably brought close to the center line 1cl within a half of the difference between a diameter of the fuel rail body 1 and a diameter of a root portion of the injector cup 2 or closer.
The inlet 8 and the injector cup 2 will be described later in detail.
As illustrated in
The fitting fixing surface 6 is formed such that parallel surfaces are formed on both sides across the center line 1cl. Further, the fitting fixing surface 6 is formed at two portions in a direction along the center line 1cl and totally formed at four portions in the fuel rail body 1. In the embodiment, the fitting fixing surface 6 is formed in parallel with the center lines 1cl and 2cl. However, according to a mounting angle of the injector 28 with respect to an engine block, the fitting fixing surface 6 may be displaced from an angle parallel to the center line 2cl.
A thickness of the fuel rail body 1 is reduced by forming the fitting fixing surface 6. A stress is generated by receiving a pressure of a high pressure fuel in the fuel rail 32. As to be described later, this stress is concentrated at a joint between the fuel rail body 1 and the injector cup 2. Thicknesses of middle portions of two adjacent injector cups 2 are reduced when the fitting fixing surface 6 is formed. Therefore, an issue of a decrease in the strength of the fuel rail body 1 by the thickness reduction does not become apparent.
A plane portion 1b is formed from one end to another end along the center line 1cl in an upper portion (a side opposite to the side where the injector cup 2 is formed) of the fuel rail body 1. The plane portion 1b becomes a reference surface for processing the center hole the tip surface 2a of the injector cup 2, the opening portion 2b, the receiving groove 2c, the inside/outside communication note 2d, and the fitting fixing surface 6.
A structure of the injector cup 2 will be described in detail with reference to
A screw portion 1c is formed at an end portion on a side where the center hole 1a of the fuel rail body 1 is opened. A pressure sensor is mounted to the screw portion 1c.
The opening portion 2b formed on the tip surface 2a of the injector cup 2 includes an inner peripheral surface in which three arc portions 2b1 and three straight line portions 2b2 are formed by alternately connecting. This inner peripheral surface has a shape in which the straight portions 2b2 form an inner angle of 60° each other, and both ends of each straight portion 2b2 are connected at the arc portion 2b1 In other words, a round shape is formed by the arc portion 2b1 at three peak portions of an equilateral triangle formed by three straight line portions 2b2.
In the receiving groove 2c formed on an inner side of the opening portion 2b, a peripheral surface which is a bottom surface of the groove has a circular shape in which the center line 2cl is a center. A radius r1 of the peripheral surface is larger than a radius r2 of the arc portion 2b1 of the opening portion 2b as illustrated in
In the embodiment, the injector locking portion 2e is provided on an inner surface of the injector cup 2. However, the injector locking portion 2e may provided on an outer peripheral surface of the injector cup 2. In this case, a clip holder 66 and a clip plate 70 described in JP 2013-199943 A described in Background Art may be used. Both of reference signs of the clip holder 66 and the clip plate 70 are signs described in JP 2013-199943 A.
The fuel supply port 28b of the injector 28 is inserted into the inside/outside communication hole 2d of the injector cup 2 and receives supply of high pressure fuel from the inside/outside communication hole 2d.
A stress generated by a pressure received from a high pressure fuel is concentrated in a portion 2f (refer to
In the embodiment, with respect to the stress concentration, a necessary strength is secured by increasing the thickness d2 of a root portion of the injector cup 2 in comparison with the thickness d1 or the fuel rail body 1. In the embodiment, as to be described later, the injector cup 2 and the fuel rail body 1 are integrally molded by forging. Therefore, a round portion 2g is formed at a connection portion between the injector cup 2 and the fuel rail body 1. The thickness d2 of the root portion of the injector cup 2 is defined based on a cross point (a root portion of the injector cup 2) 2j between a segment 2i and a segment 1e. In the segment 2i, the center line 2cl direction is extended on the fuel rail body 1 side along an outer peripheral surface 2h of the injector cup 2. In the segment 1e, the center line 1cl direction is extended on the injector cup 2 side along an outer peripheral surface of the fuel rail body 1. That is, the thickness is defined by a thickness formed between the cross point 2j and the cross hole 2d. (a distance between the cross point 2j and the cross hole 2d). In this case, the outer peripheral surface of the injector cup 2 and the outer peripheral surface of the fuel rail body 1 are a portion viewed on a plane including the center lines 1cl and 2cl, and the segment 1e, the segment 2i, and the cross point 21 are viewed on the plane including the center lines 1cl and 2cl.
To increase the thickness d2 of the root portion of the injector cup 2, the diameter d3 of the root portion of the injector cup 2 is set to be larger than a longitudinal dimension (height) d4 of the fuel rail body 1 and a width direction dimension d5 of the fuel 1 body I (refer to
An inlet 8 will be described with reference to
The inlet 8 is formed by machining (cutting) at an end portion on a side where the center hole 1a of the fuel rail body 1 is not penetrated. An outer diameter of the inlet 8 is smaller than an outer diameter of the fuel rail body 1. In the inlet 8, a fuel introduction hole 8a is formed along the center line 1cl. The fuel introduction hole 8a introduces a high pressure fuel sent from the high-pressure fuel pump 36 into the accumulator (center hole) 1a. A throttle 8b is formed in a portion connected to the accumulator 1a of the fuel introduction hole 8a. The fuel introduction hole 8a and the throttle 8b are formed by machining (cutting). The throttle 8b reduces a pressure pulsation of the high pressure fuel sent from the high-pressure fuel pump 36.
As described above, the fuel 34 extending from the high-pressure fuel pump 36 is connected via the fuel reservoir 90 or connected directly to the inlet 8.
Next, a processing method for the fuel rail 32 will be described with reference to
The fuel rail material 32′ according to the embodiment is made of a metal material. Specifically, a stainless material is used as the metal material. However, it is not limited to stainless. A block of a metal material is molded by forging in the shapes illustrated in
The plane 1b being a reference for the fuel rail body 1′ of the fuel rail material 32′ is machined (cut).
Then, the center hole 1a, the screw portion 1c, the injector cup 2, and the fitting fixing, surface 6 are machined on the fuel rail material 32′. The center hole 1a is formed by cutting by a drill. In the injector cup 2, a tip surface 2a is cut by lathe, and then the opening portion 2b, the receiving groove 2c, and the inside/outside communication hole 2d are cut by lathe. The fitting fixing surface 6 is formed by cutting an outer peripheral surface of the fuel rail body 1 by lathe. Therefore, in the fitting fixing surface 6, a thickness of the fuel rail body 1 is reduced when a vertical direction dimension is excessively increased with respect to the center line 1cl. Therefore, the fitting, fixing surface is set to a size needed to fix a fitting.
In the embodiment, the fuel rail body 1 and the injector cup 2 are integrally molded by forging. Therefore, a bearing force against a fuel pressure of the fuel rail 32 can be increased. Further, by reducing an outer diameter of the fuel rail body 1 and increasing the thickness d2 of a root portion of the injector cup 2, the strength of a connection portion (a root portion of the injector cup 2) between the fuel rail body 1 and the injector cup 2, in which stress concentration generates, can be increased, and a volume of the fuel rail 32 can be reduced. In addition, by tapering the injector cup 2, the volume of the fuel rail 32 can be further reduced.
A mounting structure of the fuel rail 32 will be described with reference to
The fitting 7 is fixed by welding on the fitting fixing surface 6 of the fuel rail body 1. The fittings 7 are fixed on the fitting fixing surfaces 6 disposed at four positions. A length W1 in the center line 1cl direction of the fitting fixing surface 6 is set to be longer than a length W2 in the center line 1cl direction of the fitting 7.
As a result, a mounting position of the fitting 7 can be adjusted in the center line 1cl direction. For example, the fuel rail 32 having same specification is made for two-type engines in which an interval between the injectors 28 is same, and a fixing position of the fuel rail 32 with respect to the engine block 24 is different. Then, the fuel rail 32 having the same specification can be used by adjusting a mounting position of the fitting 7 with respect to the fuel rail body 1. Specifically, the fitting fixing surface 6 includes an adjusting margin of a mounting position of the fitting 7 in a longitudinal direction of the fuel it body 1.
The present invention is not limited to the above-described embodiment and includes various variations. For example, the above-described embodiment describes the present invention in detail for clarification, and every configurations may not be necessarily included. Further, a part of a configuration of the embodiment can be added to, deleted from, and replaced from other configurations.
Number | Date | Country | Kind |
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2014-188603 | Sep 2014 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2015/069817 | 7/10/2015 | WO | 00 |