fuel injection device

Abstract

To provide a fuel injection device that can reduce the occurrence of corrosion or the like and the risk of erosion even when a combustion gas contains a large amount of sulfur compound.SOLUTION: A fuel injection device has an injector housing (2), a nozzle body (3, 3') provided with a fuel injection hole (12), a first nut member (6) that fastens the nozzle body (3, 3') to an end of the injector housing (2), and a second nut member (11, 11') provided between the first nut member (6) and the fuel injection hole (12).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel injection device that injects fuel into a combustion chamber of an engine. [Background technology]

[0002] Patent Document 1 discloses a fuel injection device that injects and supplies high-pressure fuel into the combustion chamber of an internal combustion engine such as a diesel engine, and that has a structure in which a nozzle body and a holder body (injector housing) are fastened together with a retaining nut. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-147310 Summary of the Invention [Problem to be solved by the invention]

[0004] Fig. 6 is a schematic diagram showing a conventional fuel injection device 201 attached to a cylinder head 300 of an internal combustion engine. Only the nozzle side of the fuel injection device 201 is shown. Fig. 7 is an enlarged view of part C in Fig. 6. The fuel injection device 201 includes an injector housing 202, a nozzle body 203, a nozzle needle 204, a retaining nut 206, etc.

[0005] A fuel injection hole 212 that is opened and closed by a nozzle needle 204 is formed at the tip of the nozzle body 203. That is, when the fuel injection hole 212 is opened, high-pressure fuel is injected from the fuel injection hole 212 into a combustion chamber 302 of an internal combustion engine, and when the fuel injection hole 212 is closed, fuel injection is stopped. This high-pressure fuel is sent to the tip side of the nozzle body 203 via first fuel passages 215, 216 formed in the injector housing 202 and the nozzle body 203.

[0006] The nozzle body 203 is fastened to the end of the injector housing 202 by a retaining nut 206. When fastening the nozzle body 203, a receiving surface 206a of the retaining nut 206 is brought into contact with a shoulder surface 203a of the nozzle body 203, and the nozzle body 203 is fastened while being sandwiched between the retaining nut 206 and the injector housing 202. At this time, an axial tensile stress σ is applied to a corner 203b on the inside of the shoulder surface 203a. c occurs.

[0007] A mounting hole 304, into which the fuel injection device 201 is inserted, is formed in the cylinder head 300 so as to penetrate the combustion chamber 302 and the cylinder head upper part 301. The mounting hole 304 has, from the combustion chamber 302 side, a small diameter portion 304b and a large diameter portion 304a having a diameter larger than the small diameter portion 304b, in that order, and an annular stepped portion 304c is formed between the large diameter portion 304a and the small diameter portion 304b. An end face 206b of the retaining nut 206 on the fuel injection hole 212 side is disposed on the annular end face of this stepped portion 304c via an annular gasket 306. The fuel injection device 201 is pressed and fixed to the cylinder head 300 by a clamp (not shown) that presses the fuel injection device 201 toward the cylinder head 300. At this time, the pressing force of the clamp causes an axial tensile stress σ d That is, the corner 203b is subjected to an axial tensile stress σ c In addition, the axial tensile stress σ due to the clamp pressure d (σ in Figure 7) c、 σ d (See

[0008] Some of the combustion gas generated in the combustion chamber 302 passes through the small-diameter portion 304b and reaches the gasket 306 (see g in FIG. 7 ), but a small amount of the combustion gas may pass through this and reach the corner 203b of the nozzle body 203 (see g' in FIG. 7 ). Depending on the country in which the fuel injection device 201 is used, the combustion gas may contain a large amount of sulfur compounds due to the use of fuel that has not been sufficiently desulfurized. This combustion gas containing a large amount of sulfur compounds may cause corrosion of the surface of the nozzle body 203, etc. In particular, at the corner 203b where tensile stress is generated, the synergistic effect of the combustion gas containing a large amount of sulfur compounds may accelerate erosion due to corrosion.

[0009] An object of the present invention is to provide a fuel injection device that can reduce the risk of corrosion and erosion even when combustion gas contains a large amount of sulfur compounds. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a fuel injection device comprising: an injector housing; a nozzle body having a fuel injection hole formed therein; a first nut member fastening the nozzle body to an end of the injector housing; and a second nut member provided between the first nut member and the fuel injection hole. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a fuel injection device that can reduce the risk of corrosion and erosion even when the combustion gas contains a large amount of sulfur compounds. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a fuel injection device according to an embodiment of the present invention. [Figure 2] 2 is a schematic diagram showing a state in which the fuel injection device of FIG. 1 is attached to a cylinder head of an internal combustion engine. [Figure 3]FIG. 3 is an enlarged view of part A in FIG. 2. [Figure 4] FIG. 10 is a schematic diagram showing a state in which a fuel injection device according to a modified example of the present invention is attached to a cylinder head of an internal combustion engine. [Figure 5] FIG. 5 is an enlarged view of part B in FIG. [Figure 6] 1 is a schematic diagram showing a state in which a conventional fuel injection device is attached to a cylinder head of an internal combustion engine. [Figure 7] FIG. 7 is an enlarged view of part C in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] A specific example of an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described. However, the present embodiment shows one aspect of the present invention, does not limit the present invention, and can be arbitrarily modified within the scope of the present invention.

[0014] The following describes a fuel injection device 1 to which the present invention is applied. Specifically, as shown in Figure 1, the fuel injection device 1 includes an injector housing 2, a nozzle body 3, a nozzle needle 4, a nozzle spring 5, a retaining nut 6, a valve piston 7, a valve body 8, an electromagnetic actuator 9, an inlet portion 10, a nozzle nut 11, etc.

[0015] The nozzle body 3 is fastened to the tip end (the lower tip end in FIG. 1 ) of the injector housing 2 with a retaining nut (first nut member) 6. The injector housing 2 and the nozzle body 3 are each formed with first fuel passages 15, 16 that send high-pressure fuel introduced from an inlet portion 10 to a fuel reservoir chamber 17 formed inside the nozzle body 3. The inlet portion 10 is connected to a common rail (not shown), and high-pressure fuel is introduced into the inlet portion 10 from the common rail.

[0016] A fuel injection hole 12 is formed at the tip of the nozzle body 3. The tip of the nozzle needle 4 seats (seats) on a seat portion 13 connected to this fuel injection hole 12, thereby closing the fuel injection hole 12, while the tip of the nozzle needle 4 lifts (lifts) away from the seat portion 13, thereby opening the fuel injection hole 12. This allows fuel injection to start and stop. In addition, a nozzle nut (second nut member) 11 is attached to the nozzle body 3 between the retaining nut (first nut member) 6 and the fuel injection hole 12, and this point will be described later.

[0017] A spring chamber 18 is formed in the injector housing 2, with its center axis at its center, and a nozzle spring 5 is disposed in the spring chamber 18. The nozzle spring 5 biases the nozzle needle 4 toward the seat portion 13.

[0018] The valve piston 7 is inserted into a hole 30 formed in the injector housing 2. The valve piston 7 is arranged so that a lower part 31 on the fuel injection hole 12 side is positioned above the nozzle needle 4, and an upper part 32 on the other side is slidably inserted into a slide hole 34 formed in the valve body 8.

[0019] A pressure control chamber 20 is formed in the valve body 8 at a location where the top 33 of the valve piston 7 is located. That is, the pressure control chamber 20 is formed so that the top 33 of the valve piston 7 faces upward from the lower side (the fuel injection hole 12 side). The pressure control chamber 20 also communicates with an introduction orifice passage 24 formed in the valve body 8. This introduction orifice passage 24 communicates with the second fuel passage 22 via a pressure introduction chamber 23 formed annularly in the circumferential direction of the valve body 8 between the valve body 8 and the injector housing 2. That is, high-pressure fuel introduced into the inlet portion 10 flows sequentially through the second fuel passage 22, the pressure introduction chamber 23, and the introduction orifice passage 24, and is supplied to the pressure control chamber 20.

[0020] The pressure in the pressure control chamber 20 is configured to push the nozzle needle 4 downward via the valve piston 7, and the pressure in the fuel reservoir chamber 17 is configured to push the nozzle needle 4 upward.

[0021] The pressure control chamber 20 also communicates with an opening / closing orifice passage 25 for discharging high-pressure fuel to the low-pressure side. The opening / closing orifice passage 25 is opened and closed by an electromagnetic actuator 9. The electromagnetic actuator 9 is an electromagnetic actuator that opens and closes the opening / closing orifice passage 25 by switching between energized and de-energized states. The electromagnetic actuator 9 in this embodiment opens the opening / closing orifice passage 25 when energized, and closes the opening / closing orifice passage 25 when de-energized.

[0022] When the opening / closing orifice passage 25 is closed, the pressure inside the pressure control chamber 20 becomes the pressure of the high-pressure fuel introduced into the inlet portion 10. On the other hand, when the opening / closing orifice passage 25 is opened, the high-pressure fuel inside the pressure control chamber 20 flows through the opening / closing orifice passage 25 to the electromagnetic actuator 9 side, which is the low-pressure side, and the pressure inside the pressure control chamber 20 drops compared to before the opening. This is because the flow path cross-sectional area of ​​the opening / closing orifice passage 25 is larger than the flow path cross-sectional area of ​​the introduction side orifice passage 24, so when the opening / closing orifice passage 25 is opened, the amount of fuel flowing into the pressure control chamber 20 through the introduction side orifice passage 24 is less than the fuel flowing out of the pressure control chamber 20 through the opening / closing orifice passage 25. The fuel that has flowed out to the electromagnetic actuator 9 side then flows back through the fuel return path 86 to a fuel tank (not shown).

[0023] When the opening / closing orifice passage 25 is closed, the downward force acting on the nozzle needle 4 due to the pressure in the pressure control chamber 20 plus the biasing force of the nozzle spring 5 becomes greater than the upward force acting on the nozzle needle 4 due to the pressure in the fuel sump chamber 17, etc., and the nozzle needle 4 is pushed downward, closing the fuel injection hole 12. This puts the fuel injection device 1 into a state where fuel is not injected.

[0024] On the other hand, when the opening / closing orifice passage 25 is opened, the downward force acting on the nozzle needle 4 due to the pressure in the pressure control chamber 20 plus the biasing force of the nozzle spring 5 becomes smaller than the upward force acting on the nozzle needle 4 due to the pressure in the fuel sump chamber 17, etc., so that the nozzle needle 4 is pushed upward and the fuel injection hole 12 is opened. This enables the fuel injection device 1 to inject fuel.

[0025] To summarize the above, in the fuel injection device 1, when the electromagnetic actuator 9 is energized, the opening / closing orifice passage 25 is opened, the pressure in the pressure control chamber 20 drops, the nozzle needle 4 that had been blocking the fuel injection hole 12 rises, and fuel is injected from the fuel injection hole 12. On the other hand, when the electromagnetic actuator 9 is de-energized, the opening / closing orifice passage 25 is closed, the pressure in the pressure control chamber 20 rises, the nozzle needle 4 drops and blocks the fuel injection hole 12, and fuel injection is stopped.

[0026] Fig. 2 is a schematic diagram showing a state in which the fuel injection device 1 of Fig. 1 is attached to a cylinder head 100 of an internal combustion engine. Only the nozzle side of the fuel injection device 1 is shown. Fig. 3 is an enlarged view of part A of Fig. 2.

[0027] The lower end surface of the injector housing 2 is formed with a lower end surface 2c that forms a high-pressure seal with the upper end surface 3e of the nozzle body 3, and the lower cylindrical side surface of the injector housing 2 is formed with a male thread portion 2b for tightening and fixing a retaining nut 6.

[0028] The retaining nut 6 is formed in a cylindrical shape and has a cylindrical portion 6c provided with a female thread portion 6b that screws onto the male thread portion 2b of the injector housing 2, and a holding portion 6d that is positioned closer to the fuel injection hole 12 than the cylindrical portion 6c. In the fuel injection device 1 according to this embodiment, the retaining nut 6 is a first nut member.

[0029] The nozzle body 3 has an upper end surface 3e, which forms a high-pressure seal with the lower end surface 2c of the injector housing 2, and an annular shoulder surface 3a, which is parallel to the upper end surface 3e, located closer to the fuel injection hole 12 than the upper end surface 3e. A stopper 3c and a male thread portion 3d, which extend radially outward from the cylindrical portion, are formed in this order from the shoulder surface 3a side, along a cylindrical portion extending from the inner circular portion of the annular shoulder surface 3a toward the fuel injection hole 12 side. The shoulder surface 3a and the cylindrical portion intersect perpendicularly at a corner 3b.

[0030] The holding portion 6d of the retaining nut 6 has an annular receiving surface 6a that is arranged opposite to the shoulder surface 3a of the nozzle body 3. By tightening the female thread portion 6b of the retaining nut 6 onto the male thread portion 2b of the injector housing 2, the nozzle body 3 is tightened and fixed to the tip portion of the injector housing 2. At this time, the shoulder surface 3a is pressed by the receiving surface 6a, and the corner portion 3b is subjected to an axial tensile stress σ a occurs (see Figure 3).

[0031] The nozzle nut 11 has an end face 11b on the fuel injection hole 12 side, an end face 11a on the opposite side, and a female thread portion 11c that is provided on the inner circumferential side between end face 11b and end face 11a and that screws into the male thread portion 3d of the nozzle body 3. When the nozzle nut 11 is tightened onto the male thread portion 3d, the end face 11a comes into contact with the stopper 3c, and the nozzle nut 11 is tightened and fixed to the nozzle body 3. In this way, in the fuel injection device 1 according to this embodiment, the nozzle nut 11 is provided between the retaining nut 6 and the fuel injection hole 12. Note that in the fuel injection device 1 according to this embodiment, the nozzle nut 11 is a second nut member.

[0032] The cylinder head 100 is formed with a mounting hole 104, into which the fuel injection device 1 is inserted, penetrating the combustion chamber 102 and the cylinder head upper part 101. The mounting hole 104 has, from the combustion chamber 102 side, a small diameter portion 104b and a large diameter portion 104a having a diameter larger than the small diameter portion 104b, in that order, and has an annular stepped portion 104c between the large diameter portion 104a and the small diameter portion 104b. An end face 11b of the nozzle nut 11 on the fuel injection hole 12 side is disposed on the annular end face of this stepped portion 104c via an annular gasket 106. The fuel injection device 1 is pressed and fixed to the cylinder head 100 by a clamp (not shown) that presses the fuel injection device 1 toward the cylinder head 100. At this time, the pressing force of the clamp generates an axial compressive stress σ b occurs (see Figure 3).

[0033] In this way, the tightening of the retaining nut 6 causes the corner portion 3b to undergo the axial tensile stress σ a On the other hand, the pressing force of the clamp generates an axial compressive stress σ b As a result, the corner 3b is subjected to these tensile stresses σ a and compressive stress σ b As a result, only the difference occurs between the corner portion 3b and the nozzle body 3. In this way, the fuel injection device 1 of this embodiment can reduce the stress generated at the corner portion 3b compared to conventional products. Therefore, the fuel injection device 1 of this embodiment can reduce the risk of corrosion and erosion at the corner portion 3b of the nozzle body 3 even when the combustion gas contains a large amount of sulfur compounds.

[0034] In addition, in order for the combustion gas that has passed through the gasket 106 to reach the corner 3b, it must pass through the threaded portion between the female thread portion 11c of the nozzle nut 11 and the male thread portion 3d of the nozzle body 3. Therefore, the fuel injection device 1 of this embodiment can reduce the amount of combustion gas that reaches the corner 3b compared to conventional products. Therefore, with the fuel injection device 1 of this embodiment, even when the combustion gas contains a large amount of sulfur compounds, the risk of corrosion and erosion at the corner 3b of the nozzle body 3 can be reduced.

[0035] <Modification> Fig. 4 is a schematic diagram showing a fuel injection device 1' according to a modified example attached to the cylinder head of an internal combustion engine. Only the nozzle side of the fuel injection device 1' is shown. Fig. 5 is an enlarged view of part B in Fig. 4.

[0036] The fuel injection device 1' differs from the fuel injection device 1 in a nozzle body 3' and a nozzle nut 11'.

[0037] The upper end of the nozzle body 3' is formed with an upper end surface 3'e that forms a high-pressure seal with the lower end surface 2c of the injector housing 2, and a shoulder surface 3'a, which is an annular surface parallel to the upper end surface 3'e, located closer to the fuel injection hole 12 than the upper end surface 3'e. A male thread portion 3'd is formed midway on a cylindrical portion extending from the circular portion inside the shoulder surface 3'a toward the fuel injection hole 12. The shoulder surface 3'a and the cylindrical portion intersect perpendicularly at a corner 3'b. As such, the nozzle body 3' does not have a stopper.

[0038] The nozzle nut 11' has an end face 11'b on the fuel injection hole 12 side, an end face 11'a on the opposite side, and a female thread portion 11'c that is provided on the inner circumferential side between end faces 11'b and 11'a and that threadably engages with the male thread portion 3'd of the nozzle body 3'. When the nozzle nut 11' is tightened onto the male thread portion 3'd, the end face 11'a abuts against the lower end face 6e, which is the lower end face of the retaining nut 6, and the nozzle nut 11' is tightened and fixed to the nozzle body 3. In this way, in the fuel injection device 1' according to the modified example, the nozzle nut 11' is provided between the retaining nut 6 and the fuel injection hole 12. In the fuel injection device 1' according to the modified example, the retaining nut 6 is a first nut member, and the nozzle nut 11' is a second nut member.

[0039] In the fuel injection device 1' according to the modified example, there is no need to provide a stopper on the nozzle body 3', so the cost can be kept lower than in the embodiment shown in FIG.

[0040] 2, in order for the combustion gas that has passed through the gasket 106 to reach the corner 3'b, it must pass through the threaded portion between the female thread portion 11'c of the nozzle nut 11' and the male thread portion 3'd of the nozzle body 3'. Therefore, the fuel injection device 1' according to the modified example can reduce the amount of combustion gas that reaches the corner 3'b compared to the conventional product. Therefore, with the fuel injection device 1' of this embodiment, even when the combustion gas contains a large amount of sulfur compounds, the risk of corrosion and erosion at the corner 3'b of the nozzle body 3' can be reduced.

[0041] As described above, the fuel injection device 1 of this embodiment and the fuel injection device 1' according to the modified example can reduce the risk of corrosion and erosion even when the combustion gas contains a large amount of sulfur compounds. [Explanation of symbols]

[0042] 1 1' fuel injection device, 2 injector housing, 2b male thread portion, 2c lower end surface, 3 3' nozzle body, 3a 3'a one side, 3b 3'b corner portion, 3c stopper, 3d 3'd male thread portion, 3e 3'e upper end surface, 4 nozzle needle, 5 nozzle spring, 6 retaining nut (first nut member), 6a receiving surface, 6b female thread portion, 6c cylindrical portion, 6d holding portion, 7 valve piston, 8 valve body, 9 electromagnetic actuator, 10 inlet portion, 11 11' nozzle nut (second nut member), 11a 11'a end surface, 11b 11'b end surface, 11c 11'c female thread portion, 12 fuel injection hole, 13 seat portion, 15 16 first fuel passage, 17 fuel reservoir chamber, 18 Spring chamber, 20, pressure control chamber, 22 second fuel passage, 23 pressure introduction chamber, 24 introduction side orifice passage, 25 opening / closing orifice passage, 86 fuel return passage, 100 cylinder head, 101 upper part of cylinder head, 102 combustion chamber, 104 mounting hole, 104a large diameter portion, 104b small diameter portion, 104c step portion, 106 gasket, 201 fuel injection device, 202 injector housing, 203 nozzle body, 203a shoulder surface, 203b corner portion, 204 nozzle needle, 206 retaining nut, 206a receiving surface, 212 fuel injection hole, 215, 216 first fuel passage, 300 cylinder head, 302 combustion chamber, 304 mounting hole, 304a large diameter portion, 304b small diameter portion, 304c step portion, 306 Gaskets,

Claims

1. an injector housing (2); a nozzle body (3, 3') in which a fuel injection hole (12) is formed; a first nut member (6) for fastening the nozzle body (3, 3') to the end of the injector housing (2); a second nut member (11, 11') provided between the first nut member (6) and the fuel injection hole (12); Equipped with a female screw (11c, 11'c) formed on the second nut member (11, 11') is threadedly engaged with a male screw (3d, 3'd) formed on the nozzle body (3, 3'); When the female thread (11c) is threadedly engaged with the male thread (3d), the end surface of the second nut member (11) abuts against a stopper (3c) provided on the nozzle body (3). Fuel injection device.

2. An injector housing (2), a nozzle body (3, 3') in which a fuel injection hole (12) is formed; a first nut member (6) for fastening the nozzle body (3, 3') to the end of the injector housing (2); a second nut member (11, 11') provided between the first nut member (6) and the fuel injection hole (12); Equipped with a female screw (11c, 11'c) formed on the second nut member (11, 11') is threadedly engaged with a male screw (3d, 3'd) formed on the nozzle body (3, 3'); When the female thread (11'c) is threadedly engaged with the male thread (3'd), the end surface of the second nut member (11') abuts against the first nut member (6). Fuel injection device.

Images