Fuel injection device

Abstract

This fuel injection device comprises: a needle valve for opening and closing an injection port, the needle valve being inserted into an injector center hole of an injector body and a nozzle center hole of a nozzle body; a retaining nut which holds the nozzle body from the injection port side in the axial direction in which a nozzle axis line of the nozzle body extends, and is screwed into a screw portion formed on an injector outer peripheral surface which is an outer peripheral surface of the injector body; and a sleeve including a sleeve inner peripheral surface which fits onto a nozzle outer peripheral surface which is an outer peripheral surface of the nozzle body and the injector outer peripheral surface, the sleeve being positioned inward in the radial direction with respect to the nozzle axis line relative to the retaining nut and positioned on the injection port side in the axial direction with respect to the screw portion.

Description

fuel injector

[0001] This disclosure relates to a fuel injection device for injecting high-pressure fuel stored in a common rail into a combustion chamber of a diesel engine. This application claims priority to Japanese Patent Application No. 2024-088565, filed with the Japan Patent Office on May 31, 2024, the contents of which are incorporated herein by reference.

[0002] The fuel injection device disclosed in Patent Document 1 includes a nozzle body in which a fuel injection port is formed, an injector body arranged coaxially with the nozzle body, and a needle valve inserted into holes formed in the nozzle body and the injector body. The needle valve opens and closes the injection port by sliding relative to the two holes.

[0003] A knock pin structure is used to connect the injector body and the nozzle body. More specifically, one end face of the injector body and the other end face of the nozzle body face each other, and fitting holes are formed in each of these two end faces. One pin fits into each of the two fitting holes, thereby aligning the injector body and the nozzle body.

[0004] Japanese Patent Application Laid-Open No. 2006-299911

[0005] Generally, the manufacturing process for a fuel injection device includes a heat hardening process in which the injector body and the nozzle body are heat treated to obtain high hardness sufficient to withstand the injection of high-pressure fuel, and a connecting process in which the heat-treated injector body and the nozzle body are connected together.

[0006] When the knock pin structure disclosed in the above-mentioned patent document is adopted, drilling processes for forming mating holes in the end surfaces of the injector body and the nozzle body must be performed before the heat curing process. However, these mating holes may be slightly deformed during the heat curing process, which may prevent accurate alignment between the injector body and the nozzle body during the connecting process. If a fuel injection device is manufactured without accurate alignment, problems such as fuel leakage from the injection port closed by the needle valve or the needle valve getting caught in the hole and preventing smooth movement may occur.

[0007] An object of the present disclosure is to provide a fuel injection device with high alignment accuracy between the injector body and the nozzle body.

[0008] A fuel injection device according to at least one embodiment of the present disclosure is a fuel injection device for injecting fuel stored under pressure in a common rail into a combustion chamber of a diesel engine, the fuel injection device comprising: a nozzle body including one end where an injection port for injecting the fuel is formed and another end opposite to the one end, the nozzle body having a nozzle center hole extending from the injection port to the other end; an injector body abutting the other end of the nozzle body, the injector body having an injector center hole coaxial with the nozzle center hole; a needle valve for opening and closing the injector center hole and the injection port inserted into the injector center hole; a retaining nut that holds the nozzle body from the injection port side in the axial direction along which a nozzle axis of the nozzle body extends, and that screws into a threaded portion formed on an injector outer peripheral surface, which is the outer peripheral surface of the injector body; a sleeve including an inner peripheral surface that fits into a nozzle outer peripheral surface, which is the outer peripheral surface of the nozzle body, and an outer peripheral surface of the injector, the sleeve being located radially inward of the retaining nut relative to the nozzle axis and on the injection port side in the axial direction relative to the threaded portion.

[0009] According to the present disclosure, it is possible to provide a fuel injection device with high centering accuracy between the injector body and the nozzle body.

[0010] 2 is a schematic cross-sectional view of a fuel injection device according to an embodiment; FIG. 3 is a schematic diagram of an injector body and a nozzle body according to an embodiment; FIG. 4 is a schematic enlarged view of a portion of FIG.

[0011] Several embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure and are merely illustrative examples. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is achieved. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is achieved. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is achieved. On the other hand, the expressions "comprise," "include," or "have" one component are not exclusive expressions that exclude the existence of other components. Note that similar components may be assigned the same reference numerals and descriptions thereof may be omitted.

[0012] 1 is a schematic cross-sectional view of a fuel injection device 1 according to an embodiment of the present disclosure. The fuel injection device 1 is configured to inject high-pressure fuel stored in a common rail into a combustion chamber of a diesel engine.

[0013] The fuel injection device 1 includes an injector body 20 having a fuel inlet 81 formed therein for introducing fuel from a common rail, and a nozzle body 10 having an injection port 13 formed therein for injecting fuel into a combustion chamber. The injector body 20 and the nozzle body 10 form linearly extending, generally columnar or cylindrical members.

[0014] In the following description, the axis of the nozzle body 10 will be referred to as the "nozzle axis C," and the axial direction of the nozzle axis C will sometimes be simply referred to as the "axial direction." The injection port 13 is formed at one end 14, which is the end of the nozzle body 10 on one side in the axial direction, and the other end 19, which is the end of the nozzle body 10 on the other side in the axial direction, abuts against the injector body 20. The nozzle axis C is an imaginary straight line that substantially coincides with the center line of the nozzle body 10.

[0015] Furthermore, in the following description, the circumferential direction and the radial direction based on the nozzle axis C may be simply referred to as the "circumferential direction" and the "radial direction," respectively. The radially inner direction is the direction approaching the nozzle axis C, and the radially outer direction is the direction moving away from the nozzle axis C.

[0016] An injector fuel flow passage 91 extending along the axial direction is formed inside the injector body 20. Fuel introduced through the fuel inlet 81 flows through the injector fuel flow passage 91 and into the injector central hole 20C. The fuel then flows into a nozzle chamber 93 that can communicate with the injection port 13.

[0017] An injector center hole 20C is formed in the center of the injector body 20, and a nozzle center hole 10C is formed in the center of the nozzle body 10. The injector center hole 20C and the nozzle center hole 10C are holes that extend in the axial direction and are coaxial with each other. The nozzle center hole 10C includes the nozzle chamber 93 and the injection port 13 described above as components.

[0018] The fuel injection device 1 includes a needle valve 5 that is inserted into the injector central hole 20C and the nozzle central hole 10C. The needle valve 5 opens and closes the injection port 13 by moving axially while sliding relative to the injector central hole 20C and the nozzle central hole 10C.

[0019] The following describes the configuration for moving the needle valve 5. The fuel injection device 1 includes a spring 122 that biases the needle valve 5 toward one side in the axial direction, a control chamber 4 that forms the other side of the injector central bore 20C, a communication passage 94 that connects the control chamber 4 with an injector fuel flow passage 91, a recovery passage 95 that recovers fuel from the control chamber 4, and a solenoid valve 6 that opens and closes the flow passage between the control chamber 4 and the recovery passage 95.

[0020] When the solenoid valve 6 is in the OFF state, the flow path between the control chamber 4 and the recovery path 95 is closed. The control chamber 4 is filled with high-pressure fuel supplied from the communication path 94, and the pressure in the control chamber 4 is maintained at high pressure. At this time, the needle valve 5 is pressed toward the injection port 13 by the biasing force of the spring 122 and the force caused by the pressure difference between the control chamber 4 and the combustion chamber. Therefore, when the solenoid valve 6 is in the OFF state, the needle valve 5 closes the injection port 13.

[0021] On the other hand, when the solenoid valve 6 is in the ON state, the flow path between the control chamber 4 and the recovery path 95 is opened. The fuel in the control chamber 4 flows out into the recovery path 95, and the pressure in the control chamber 4 decreases. At this time, the needle valve 5 moves axially to the other side against the biasing force of the spring 122. Therefore, when the solenoid valve 6 is in the ON state, the needle valve 5 opens the injection port 13.

[0022] FIG. 2 is a schematic enlarged view of the injector body 20 and the nozzle body 10 according to one embodiment of the present disclosure.

[0023] The injector outer peripheral surface 22 of the injector body 20 includes a first outer peripheral surface 221, a second outer peripheral surface 222 located on one axial side of the first outer peripheral surface 221, and an injector tapered outer peripheral surface 223 located between the first outer peripheral surface 221 and the second outer peripheral surface 222. The outer diameter of the first outer peripheral surface 221 is larger than the outer diameter of the second outer peripheral surface 222, and the first outer peripheral surface 221 is formed with a thread portion 9 that extends helically with respect to the nozzle axis C. The diameter of the injector tapered outer peripheral surface 223 decreases as it approaches one axial side.

[0024] The nozzle body 10 includes a large diameter portion 109, a small diameter portion 101 located on one axial side of the large diameter portion 109, and a step portion 103 connected to the large diameter portion 109 and the small diameter portion 101. The outer diameter of the large diameter portion 109 is larger than the outer diameter of the small diameter portion 101. The large diameter portion 109 has a nozzle outer peripheral surface 11 that is axially continuous with a second outer peripheral surface 222 of the injector body 20. The outer diameter of the nozzle outer peripheral surface 11 and the outer diameter of the second outer peripheral surface 222 are substantially the same.

[0025] The connection structure between the injector body 20 and the nozzle body 10 will be described with reference to Figure 2. The fuel injection device 1 includes a retaining nut 30 that threads onto the threaded portion 9 of the injector body 20. The retaining nut 30 is cylindrical and extends in the axial direction. The retaining nut 30 holds the nozzle body 10 from one axial side. More specifically, the retaining nut 30 includes a circumferentially extending portion 37 that extends in the circumferential direction to surround the small-diameter portion 101 of the nozzle body 10, and a nut abutment portion 38 is formed at the other end of the circumferentially extending portion 37. The nut abutment portion 38 abuts against the step portion 103 from one axial side, thereby holding the nozzle body 10.

[0026] The fuel injection device 1 further includes a sleeve 70 disposed radially inward of the retaining nut 30. The sleeve 70 includes a sleeve inner peripheral surface 71 that fits into the second outer peripheral surface 222 of the injector body 20 and the nozzle outer peripheral surface 11 of the nozzle body 10. By way of example only, the sleeve inner peripheral surface 71 fits into the second outer peripheral surface 222 and the nozzle outer peripheral surface 11 in a clearance fit. The sleeve 70 may also fit into these outer peripheral surfaces in an intermediate fit or an interference fit.

[0027] During the manufacturing stage of the fuel injection device 1, the nozzle central hole 10C and the injector central hole 20C can be coaxially arranged by fitting the sleeve inner peripheral surface 71 onto the nozzle outer peripheral surface 11 and the second outer peripheral surface 222. Thereafter, by threading the retaining nut 30 onto the threaded portion 9, the nut abutment portion 38 abuts against the step portion 103 and the other end 19 of the nozzle body 10 presses against the injector body 20. This holds the nozzle body 10 in place.

[0028] According to the above-described configuration, centering between the nozzle body 10 and the injector body 20 is achieved by fitting the sleeve 70 between the nozzle outer peripheral surface 11 and the second outer peripheral surface 222. Because the fit dimensions of the sleeve inner peripheral surface 71, the nozzle outer peripheral surface 11, and the second outer peripheral surface 222 of the injector body 20 can be finished after heat treatment, centering can be achieved with higher precision than in a conventional structure that connects the nozzle body 10 and the injector body 20 using a knock pin structure. While merely an example, with a conventional knock pin structure, the amount of misalignment between the actual positions of the fitting holes formed in the injector body 20 and the nozzle body 10 and the intended positions during the design stage can be limited to 50 μm, which can result in an axial misalignment of 100 μm. In contrast, with the fit dimension management according to this embodiment, the axial misalignment can be reduced to approximately one-fourth of the conventional misalignment.

[0029] Figure 3 is a partially enlarged view of Figure 2. The inner peripheral surface 31 of the retaining nut 30 has a nut extended inner peripheral surface 32 extending in the axial direction and a nut tapered inner peripheral surface 33 connected to the other axial end of the nut extended inner peripheral surface 32. The diameter of the nut tapered inner peripheral surface 33 increases as it approaches the other axial end.

[0030] The sleeve 70 includes a sleeve outer peripheral surface 77 that faces the nut extending inner peripheral surface 32 across a first gap G1 in the radial direction. According to the above configuration, when the retaining nut 30 is fastened to the threaded portion 9 (see FIG. 2 ), the sleeve outer peripheral surface 77 does not receive force from the nut extending inner peripheral surface 32. Therefore, when the retaining nut 30 is fastened, no radial force acts on the nozzle body 10 and the injector body 20, thereby preventing misalignment of the axes between them. Note that in FIG. 3 , the other end of the sleeve 70 is located axially on the other side of the other end of the nut extending inner peripheral surface 32. The present disclosure is not limited to this, and the other end of the sleeve 70 may be located axially on one side of the other end of the nut extending inner peripheral surface 32.

[0031] Furthermore, with the configuration in which the nut abutment portion 38 abuts against the step portion 103 of the nozzle body 10 from one axial side (i.e., the injection port 13 side), when the retaining nut 30 is fastened, the nut abutment portion 38 abuts against the step portion 103, pressing the nozzle body 10 against the injector body 20. At this time, the sleeve outer peripheral surface 77 is spaced apart from the nut extending inner peripheral surface 32, so that misalignment of the axes between the nozzle body 10 and the injector body 20 can be suppressed.

[0032] The nut tapered inner peripheral surface 33 faces the injector tapered outer peripheral surface 223 of the injector body 20 across a second gap G2 in the axial direction. With this configuration, the nut tapered inner peripheral surface 33 and the injector tapered outer peripheral surface 223 do not come into contact with each other when the retaining nut 30 is tightened, allowing the nut abutment portion 38 to actively abut against the step portion 103 of the nozzle body 10. Therefore, the nozzle body 10 can be effectively pressed against the injector body 20 when the retaining nut 30 is tightened. The above technical advantage is more reliably achieved in an embodiment in which the second dimension L2, which is the axial dimension of the second gap G2, is longer than the first dimension L1, which is the radial dimension of the first gap G1. The second dimension L2 may be two or more times longer than the first dimension L1.

[0033] <Summary> The contents described in the above-described embodiments can be understood, for example, as follows.

[0034] 1) A fuel injection device (1) according to at least one embodiment of the present disclosure is a fuel injection device for injecting fuel stored under pressure in a common rail into a combustion chamber of a diesel engine, the fuel injection device comprising: a nozzle body (10) including one end (14) at which an injection port (13) for injecting the fuel is formed and another end (19) opposite to the one end, the nozzle body (10) having a nozzle center hole (10C) extending from the injection port to the other end; an injector body (20) abutting the other end of the nozzle body, the injector body (20) having an injector center hole (20C) coaxial with the nozzle center hole; and a needle valve (5) inserted into the injector center hole and the nozzle center hole for opening and closing the injection port. a retaining nut (30) that holds the nozzle body from the injection port side (one side) in the axial direction along which the nozzle axis of the nozzle body extends, and that screws onto a threaded portion (9) formed on an injector outer peripheral surface (22) that is the outer peripheral surface of the injector body; and a sleeve (70) that includes a sleeve inner peripheral surface (71) that fits between a nozzle outer peripheral surface (11) that is the outer peripheral surface of the nozzle body and the injector outer peripheral surface, on an inner side of the retaining nut in a radial direction based on the nozzle axis and on the injection port side of the threaded portion in the axial direction.

[0035] According to the configuration 1) above, during the manufacturing stage of the fuel injection device, the inner peripheral surface of the sleeve is fitted onto the outer peripheral surface of the nozzle and the outer peripheral surface of the injector, thereby aligning the nozzle center hole and the injector center hole coaxially. Since the fitting dimensions of the inner peripheral surface of the sleeve, the outer peripheral surface of the nozzle, and the outer peripheral surface of the injector can be controlled, centering can be performed with higher accuracy than with the conventional structure in which the nozzle body and the injector body are connected by a knock pin structure.

[0036] 2) In some embodiments, in the fuel injection device described in 1) above, the sleeve includes a sleeve outer peripheral surface (77) that faces a nut inner peripheral surface (31) of the retaining nut with a first gap (G1) in the radial direction.

[0037] According to the configuration of 2) above, when the retaining nut is fastened to the threaded portion on the outer periphery of the injector, the outer periphery of the sleeve is not subjected to force from the inner periphery of the nut, which prevents misalignment of the axes between the nozzle body and the injector body when the retaining nut is fastened.

[0038] 3) In some embodiments, in the fuel injection device described in 2) above, the nozzle body includes a large diameter portion (109), a small diameter portion (101) located on the injection port side of the large diameter portion in the axial direction, and a step portion (103) connected to the large diameter portion and the small diameter portion, and the retaining nut includes a nut abutment portion (38) abutting against the step portion from the injection port side in the axial direction.

[0039] According to the configuration of 3), when the retaining nut is fastened to the threaded portion on the outer peripheral surface of the injector, the nut abutment portion abuts against the step portion of the nozzle body, pressing the nozzle body against the injector body. At this time, the outer peripheral surface of the sleeve (77) is spaced from the inner peripheral surface of the nut, thereby preventing misalignment of the axes between the nozzle body and the injector body when they are pressed against each other.

[0040] 4) In some embodiments, in the fuel injection device described in 3) above, the injector outer peripheral surface is an injector tapered outer peripheral surface located on the opposite side (other side) of the sleeve from the injection port side in the axial direction, and has an injector tapered outer peripheral surface (223) that narrows in diameter toward the injection port side in the axial direction, and the nut inner peripheral surface has a nut tapered inner peripheral surface (33) that faces the injector tapered outer peripheral surface with a second gap (G2) in the axial direction.

[0041] According to the configuration of 4) above, when the retaining nut is tightened onto the threaded portion on the outer peripheral surface of the injector, the tapered inner peripheral surface of the nut does not come into contact with the tapered outer peripheral surface of the injector, so the nut abutment portion can actively abut against the step portion of the nozzle body, thereby enabling the nozzle body to be pressed effectively against the injector body when the retaining nut is tightened.

[0042] 5) In some embodiments, in the fuel injection device described in 4) above, a second dimension (L2) of the second gap in the axial direction is longer than a first dimension (L1) of the first gap in the radial direction.

[0043] According to the configuration of 5) above, the second dimension of the second gap can be increased, so that when the retaining nut is fastened to the threaded portion on the outer peripheral surface of the injector, it is possible to more reliably prevent the tapered inner peripheral surface and the tapered outer peripheral surface of the sleeve from coming into contact with each other.

[0044] 1: Fuel injection device 4: Control chamber 5: Needle valve 6: Solenoid valve 9: Threaded portion 10: Nozzle body 10C: Nozzle central hole 11: Nozzle outer peripheral surface 13: Injection port 14: One end portion 19: Other end portion 20: Injector body 20C: Injector central hole 22: Injector outer peripheral surface 30: Retaining nut 31: Nut inner peripheral surface 32: Nut extended inner peripheral surface 33: Nut tapered inner peripheral surface 37: Circumferentially extending portion 38: Nut abutment portion 70: Sleeve 71: Sleeve inner peripheral surface 77: Sleeve outer peripheral surface 81: Fuel inlet 91: Injector fuel flow path 93: Nozzle chamber 94: Communication passage 95: Recovery passage 101: Small diameter portion 103: Step portion 109: Large diameter portion 122: Spring 221: First outer peripheral surface 222: Second outer peripheral surface 223: Injector tapered outer peripheral surface C: Nozzle axis G1: First gap G2: Second gap L1: First dimension L2: Second dimension

Claims

1. A fuel injection device for injecting fuel stored under pressure in a common rail into a combustion chamber of a diesel engine, comprising: a nozzle body having one end where an injection port for injecting the fuel is formed, and another end opposite the one end, the nozzle body having a nozzle center hole extending from the injection port to the other end; an injector body abutting the other end of the nozzle body, the injector body having an injector center hole coaxial with the nozzle center hole; a needle valve for opening and closing the injector center hole and the injection port inserted into the nozzle center hole; a retaining nut that holds the nozzle body from the injection port side in the axial direction along which a nozzle axis of the nozzle body extends, and that screws into a threaded portion formed on an injector outer peripheral surface that is the outer peripheral surface of the injector body; and a sleeve that includes an inner peripheral surface that fits between the nozzle outer peripheral surface that is the outer peripheral surface of the nozzle body and the injector outer peripheral surface, on an inner side in the radial direction based on the nozzle axis of the retaining nut and on the injection port side in the axial direction of the threaded portion. Fuel injection device.

2. The fuel injection device according to claim 1, wherein the sleeve includes an outer circumferential surface that faces the inner circumferential surface of the retaining nut with a first gap in the radial direction.

3. A fuel injection device as set forth in claim 2, wherein the nozzle body includes a large diameter portion, a small diameter portion located on the injection port side of the large diameter portion in the axial direction, and a step portion connected to the large diameter portion and the small diameter portion, and the retaining nut includes a nut abutment portion abutting against the step portion from the injection port side in the axial direction.

4. A fuel injection device as described in claim 3, wherein the injector outer peripheral surface is a tapered injector outer peripheral surface located on the opposite side of the sleeve from the injection port side in the axial direction, and the injector outer peripheral surface has a tapered injector outer peripheral surface that tapers in diameter toward the injection port side in the axial direction, and the nut inner peripheral surface has a tapered nut inner peripheral surface that faces the injector tapered outer peripheral surface with a second gap in the axial direction.

5. A second dimension, which is the dimension of the second gap in the axial direction, is longer than a first dimension, which is the dimension of the first gap in the radial direction.

5. The fuel injection system of claim 4.

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