Fuel injector

Abstract

Fuel injector (100, 100c), comprising: a housing (20, 20c) having a cylindrical shape, wherein the housing has an injection hole (31) for injecting fuel at one end of the housing in a longitudinal direction (Z); a solid core (60) which is fixed in the housing; a movable core (50) which is arranged between one end and the fixed core in such a way that the latter is movable along the longitudinal direction in the housing; a needle (40) that opens or closes the injection hole by moving along the longitudinal direction in the housing, just as the movable core moves; and a coil (70) configured to generate a magnetic field for moving the movable core, wherein the housing has a first inner side surface (121), a second inner side surface (122, 122c) and a third inner side surface (123) arranged in a sequence starting from one side of one end, the needle slides along the longitudinal direction on the first inner side surface (121), the movable core slides along the longitudinal direction on the second inner side surface (122, 122c), the second inner side surface (122, 122c) is located in a radial direction which intersects the longitudinal direction on an outer side of the first inner side surface (121), the solid core is fixed on the third inner side surface (123), a stepped surface (124, 126) is provided between the first inner side surface and the second inner side surface in the housing, a damping chamber (25, 25c) that stores the fuel, defined by the second inner side surface, the step surface, the needle and the movable core, and The second inner side surface is located in the radial direction on an inner side of the third inner side surface.

Description

Technical area

[0001] The present disclosure relates to a fuel injector. background

[0002] JP 2018-189 002 A describes a fuel injection valve with a damper chamber surrounded by a housing and a movable core. In the fuel injection valve, the pressure of a fuel in the damper chamber is changed by the movement of the movable core. Because the change in pressure decelerates the movable core, the impact due to collision between the movable core and the fixed core is reduced when the valve is open. Furthermore, the impact caused by collision between the needle and the valve seat is reduced when the valve is closed.

[0003] JP 2016 - 196 891 A is cited as further prior art. Summary

[0004] For example, when fuel is supplied to a fuel injection valve from the outside, or when the fuel injection valve is mounted on an engine or the like, an axial force along the longitudinal direction may act on a portion of the housing to which the fixed core is fixed. In this case, strain may occur in the portion of the housing on which the movable core slides, and the size of the gap between the portion of the housing and the movable core may change. The impact reduction effect of the damper chamber may be reduced if the movable core cannot be decelerated by the intended pressure change of the fuel in the damper chamber.

[0005] The present disclosure may be implemented as the following embodiments.

[0006] According to a first aspect of the present disclosure, a fuel injection valve includes: a housing having a cylindrical shape, the housing having an injection hole for injecting fuel at one end of the housing in a longitudinal direction of the housing; a fixed core fixed in the housing; a movable core arranged between the one end and the fixed core so as to be movable along the longitudinal direction in the housing; a needle that opens or closes the injection hole by moving along the longitudinal direction in the housing as the movable core moves; and a coil configured to generate a magnetic field for moving the movable core. The housing has a first inner side surface, a second inner side surface, and a third inner side surface arranged in order from one end side of the one end.The needle slides on the first inner side surface along the longitudinal direction. The movable core slides on the second inner side surface along the longitudinal direction. The second inner side surface is located on an outer side of the first inner side surface in a radial direction intersecting the longitudinal direction. The fixed core is fixed on the third inner side surface. A step surface is provided between the first inner side surface and the second inner side surface in the housing. A damper chamber that stores the fuel is defined by the second inner side surface, the step surface, the needle, and the movable core. The second inner side surface is located on an inner side of the third inner side surface in the radial direction.

[0007] Accordingly, the housing has the second inner side surface, on which the movable core slides, radially inside the third inner side surface to which the fixed core is fixed. Therefore, it is possible to restrict the size of the gap between the second inner side surface and the movable core from changing when an axial force along the longitudinal direction acts on the third inner surface. Thus, it is possible to achieve the impact reduction effect of the damper chamber.

[0008] According to a second aspect of the present disclosure, a fuel injection valve includes: the housing having an injection hole for injecting fuel at one end of the housing in a longitudinal direction; a fixed core fixed in the housing; a movable core arranged between the one end and the fixed core so as to be movable along the longitudinal direction in the housing; a needle that opens or closes the injection hole by moving along the longitudinal direction in the housing as the movable core moves; and a coil configured to generate a magnetic field for moving the movable core.The needle includes, in order from a side of one end, a shaft portion provided along the longitudinal direction, an enlarged diameter portion having an outer diameter larger than an outer diameter of the shaft portion, and an extension portion having an outer diameter smaller than the outer diameter of the enlarged diameter portion along the longitudinal direction. The fixed core has a first core inner surface on which the enlarged diameter portion slides, a second core inner surface on which the extension portion slides, and a core step surface provided between the first core inner surface and the second core inner surface in the fixed core. The second core inner surface has an inner diameter smaller than an inner diameter of the first core inner surface.A damper chamber for storing the fuel is defined by the enlarged diameter portion, the extension portion, the first core inner surface, and the core step surface.

[0009] Accordingly, the damper chamber is provided on the inner side of the fixed core. Therefore, it is possible to suppress changes in the size of the gap between the enlarged diameter portion of the needle and the first core inner surface of the fixed core, as well as in the size of the gap between the extended portion of the needle and the second core inner surface of the fixed core when the axial force acts on the housing along the longitudinal direction. Therefore, it is possible to limit the impact reduction effect of the damper chamber from decreasing. Short description of the drawings

[0010] It shows / it shows: Fig. 1 is a first explanatory diagram showing a schematic configuration of a fuel injection valve according to a first embodiment in a valve closing state; Fig. 2 an enlarged view of an area A in Fig. 1; Fig. 3 is a second explanatory diagram showing a schematic configuration of the fuel injection valve of the first embodiment in a valve opening state; Fig. 4 is an explanatory diagram showing a schematic configuration of a fuel injection valve according to a second embodiment in a valve closing state; Fig. 5 an enlarged view of a surface B in Fig. 4; Fig. 6 is an explanatory diagram showing a schematic configuration of a fuel injection valve according to a third embodiment in a valve closing state; Fig. 7 an enlarged view of a surface C in Fig. 6; Description of the embodimentFirst embodiment

[0011] As in Fig. 1, a fuel injection valve 100 according to a first embodiment includes a housing 20, a needle 40, a movable core 50, a fixed core 60, a coil 70, a first biasing member 81 and a second biasing member 82. In Fig. 1 shows arrows along the X, Y, and Z directions that are orthogonal to each other. In other figures, the arrows along the X, Y, and Z directions are also appropriately depicted. The X, Y, and Z directions in Fig. 1 and the X, Y, and Z directions in other figures each represent the same direction. The fuel injector 100 injects fuel. In this embodiment, the fuel injector 100 injects hydrogen gas, which is a gaseous fuel. The fuel injector 100 may inject a gaseous fuel such as coal gas, acetylene gas, propane gas, or natural gas instead of hydrogen gas. The fuel injector 100 may inject a liquid fuel such as gasoline or light oil instead of the gaseous fuel.

[0012] The housing 20 has a longitudinal direction along the Z direction. The housing 20 includes an injector 30, a first tubular member 21, a second tubular member 22, a third tubular member 23, and a fourth tubular member 24, which are connected in this order toward the +Z side in the Z direction. Both the injector 30 and the tubular members 21 to 24 have a cylindrical shape with the central axis CL along the Z direction. An injection hole 31 for injecting fuel is provided at the end of the injector 30 on the -Z side in the Z direction. A valve seat 32 is provided around the peripheral edge of the injection hole 31 of the injector 30. A valve portion 42 of the needle 40 is to be in contact with the valve seat 32. In the present embodiment, the injection nozzle 30 and the first tubular member 21 are fixed to each other by welding, press fitting or the like.The first tubular member 21 and the second tubular member 22 are fixed to each other by welding, press fitting, or the like. The second tubular member 22 and the third tubular member 23 are fixed to each other by welding, press fitting, or the like. The third tubular member 23 and the fourth tubular member 24 are fixed to each other by welding, press fitting, or the like. The injection nozzle 30 and the first tubular member 21 are made of martensitic stainless steel, which is a metallic material, and are age-hardened to a predetermined hardness. The second tubular member 22 and the fourth tubular member 24 are made of ferritic stainless steel, which is a magnetic material. The third tubular member 23 is made of austenitic stainless steel, which is a non-magnetic material.

[0013] A fuel introduction pipe 12 is connected to the fourth tubular member 24. In the present embodiment, the fourth tubular member 24 and the fuel introduction pipe 12 are fixed to each other by welding. The fuel introduction pipe 12 has a cylindrical shape with the central axis CL. An introduction port 14 for introducing fuel is provided at the end of the fuel introduction pipe 12 on the +Z side in the Z direction. A supply pipe for supplying fuel to the fuel injection valve 100 is connected to the fuel introduction pipe 12. A backup ring 91 is provided on the outer peripheral portion of the fuel introduction pipe 12. The fuel introduction pipe 12 and the supply pipe are sealed by an O-ring 92 provided on the surface of the backup ring 91 on a +Z side in the Z direction. A filter 13 is provided in the fuel inlet pipe 12.The filter 13 collects foreign matter in the fuel flowing from the introduction port 14 and prevents foreign matter from flowing into the housing 20.

[0014] The needle 40 is arranged in the housing 20 so as to be movable along the central axis CL. The needle 40 includes a shaft portion 41, the valve portion 42, and an enlarged diameter portion 43. The shaft portion 41 has a cylindrical shape with the central axis CL. The valve portion 42 is provided at the end of the shaft portion 41 on the -Z side in the Z direction. The injection hole 31 is closed by the valve portion 42 coming into contact with the valve seat 32, and the injection hole 31 is opened by the valve portion 42 being separated from the valve seat 32. In the present embodiment, the enlarged diameter portion 43 is provided at the end of the shaft portion 41 on the +Z side in the Z direction. The outer diameter of the enlarged diameter portion 43 is larger than the outer diameter of the shaft portion 41.The enlarged diameter portion 43 contacts an end surface of the movable core 50 on the +Z side in the Z direction. A fuel passage 44 through which fuel flows along the center axis CL is provided within the shaft portion 41 and the enlarged diameter portion 43. The fuel passage 44 has an opening on the end surface of the enlarged diameter portion 43 on the +Z side in the Z direction. A communication hole 45 communicating with the fuel passage 44 is provided in a side surface of the shaft portion 41.

[0015] The movable core 50 is arranged in the housing 20 so as to be movable along the central axis CL. The movable core 50 has a cylindrical shape with the central axis CL. The shaft portion 41 penetrates the inside of the movable core 50, and the shaft portion 41 slides on the inner wall surface of the movable core 50 along the Z direction. Sliding not only means that one object slides on the surface of the other object while the two objects are in contact with each other, but also means that one object slides over the surface of the other object while fluid exists between one object and the other object that are arranged adjacent to each other. The movable core 50 has a large-diameter portion 56 and a small-diameter portion 57. The outer diameter of the large-diameter portion 56 is larger than the outer diameter of the small-diameter portion 57.The small-diameter portion 57 is provided to protrude from the large-diameter portion 56 toward the -Z side in the Z direction. The enlarged-diameter portion 43 contacts the end surface of the large-diameter portion 56 on the +Z side in the Z direction.

[0016] In the present embodiment, the movable core 50 includes a first movable core member 51 made of a magnetic material and a second movable core member 52 having a hardness higher than that of the first movable core member 51. The hardness of the first movable core member 51 and the hardness of the second movable core member 52 are determined by a Vickers hardness test (JIS Z 2244). The main body of the movable core 50 is composed of the first movable core member 51. A part of the second movable core member 52 of the movable core 50 contacts or slides with the housing 20. A part of the second movable core member 52 of the movable core 50 contacts or slides with the needle 40. A part of the second movable core member 52 of the movable core 50 contacts the fixed core 60.In the present embodiment, the first movable core member 51 is made of ferritic stainless steel, which is a magnetic material. The second movable core member 52 is made of martensitic stainless steel, which is a metallic material, and is quenched to have a predetermined hardness. The first movable core member 51 and the second movable core member 52 are fixed to each other by press fitting, welding, or the like.

[0017] The fixed core 60 is fixed to the +Z side of the movable core 50 in the housing 20. In the present embodiment, the fixed core 60 is fixed to the fourth tubular member 24 by welding or the like. The fixed core 60 has a cylindrical shape with the central axis CL. The enlarged diameter portion 43 of the needle 40 slides on the inner wall surface of the fixed core 60. The movable core 50, moving along the central axis CL, contacts the end surface of the fixed core 60 on the -Z side. An adjusting tube 11 having a cylindrical shape with the central axis CL is press-fitted to an inner portion of the fixed core 60 on the +Z side.

[0018] In the present embodiment, the fixed core 60 includes a first fixed core member 61 made of a magnetic material and a second fixed core member 62 having a hardness higher than that of the first fixed core member 61. The hardness of the first fixed core member 61 and the hardness of the second fixed core member 62 are determined by a Vickers hardness test (JIS Z 2244). The main body of the fixed core 60, which faces the first movable core member 51, is configured by the first fixed core member 61. A portion of the fixed core 60 on which the enlarged diameter portion 43 slides is configured by the second fixed core member 62. In the present embodiment, the first fixed core member 61 is made of ferritic stainless steel, which is a magnetic material.The second fixed core member 62 is made of martensitic stainless steel, which is a metallic material, and is quenched to have a predetermined degree of hardness. The first fixed core member 61 and the second fixed core member 62 are fixed to each other by press fitting.

[0019] The first biasing member 81 is arranged between the adjusting tube 11 and the enlarged diameter portion 43 within the fixed core 60. The first biasing member 81 biases the needle 40 toward the -Z side. In the present embodiment, the first biasing member 81 is composed of a coil spring that expands or contracts along the Z direction. One end of the first biasing member 81 on the +Z side is in contact with the adjusting tube 11, and one end of the first biasing member 81 on the -Z side is in contact with the enlarged diameter portion 43. The force with which the first biasing member 81 biases the needle 40 can be adjusted by adjusting the position of the adjusting tube 11 in the Z direction. In the present embodiment, the position of the adjusting tube 11 is adjusted in such a way.adapted that the force of the first biasing member 81 for biasing the needle 40 is greater than the force of the second biasing member 82, which will be described later, for biasing the movable core 50.

[0020] The second biasing member 82 is arranged between the first tubular member 21 and the large-diameter portion 56. The second biasing member 82 biases the movable core 50 toward the +Z side. In the present embodiment, the second biasing member 82 is composed of a coil spring that expands or contracts along the Z direction. One end of the second biasing member 82 on the -Z side is in contact with the first tubular member 21, and one end of the second biasing member 82 on the +Z side is in contact with the large-diameter portion 56.

[0021] A coil bobbin 71, around which the coil 70 is wound, is arranged on the outer wall surface of the housing 20. In the present embodiment, the coil bobbin 71 is arranged over the outer wall surface of the third tubular member 23 and the outer wall surface of the fourth tubular member 24. A portion of the outer wall surface of the fourth tubular member 24, on which the coil bobbin 71 is not arranged, and a portion of the outer wall surface of the fuel introduction pipe 12 are covered with a resin material. A connector 15 is provided on the fourth tubular member 24 side so as to protrude from the outer wall surface of the fourth tubular member 24. The connector 15 has a terminal 16 that is electrically connected to the coil 70.In this embodiment, the connector 15, made of resin, is provided with the terminal 16, which is made of metal by insert molding. A power source such as a battery is electrically connected to the terminal 16 via a switching element or the like.

[0022] The coil 70 generates a magnetic field by supplying it with an electric current from a power source. The magnetic field generated by the coil 70 forms a magnetic circuit that passes through the second tubular member 22, the first fixed core member 61, the first movable core member 51, and the fourth tubular member 24. Therefore, a magnetic attraction force is generated between the movable core 50 and the fixed core 60. A cylindrical holder 17 is provided on the outer periphery of the coil 70 so as to cover the coil 70. An annular cover 18 is provided between the fourth tubular member 24 and the holder 17. Both the holder 17 and the cover 18 are made of a magnetic material and form part of the magnetic circuit described above.

[0023] As in Fig. 2, the housing 20 has, in this order from the -Z side, a first inner side surface 121, a second inner side surface 122, and a third inner side surface 123. In the present embodiment, the first inner side surface 121 and the second inner side surface 122 are provided on the first tubular member 21. The third inner side surface 123 is provided over the first tubular member 21, the second tubular member 22, the third tubular member 23, and the fourth tubular member 24. The shaft portion 41 of the needle 40 slides on the first inner side surface 121 along the Z direction. The small diameter portion 57 of the movable core 50 slides on the second inner side surface 122 along the Z direction. The fixed core 60 is fixed to the third inner side surface 123.The large-diameter portion 56 of the movable core 50 is movably arranged in a surface on the -Z side of the fixed core 60 within the third inner side surface 123. Each of the first inner side surface 121, the second inner side surface 122, and the third inner side surface 123 has a cylindrical shape with the central axis CL. The inner diameter of the second inner side surface 122 is larger than the inner diameter of the first inner side surface 121. The inner diameter of the third inner side surface 123 is larger than the inner diameter of the second inner side surface 122. A first step surface 124 connecting the first inner side surface 121 and the second inner side surface 122 is provided between the first inner side surface 121 and the second inner side surface 122 in the housing 20.A second step surface 125 connecting the second inner side surface 122 and the third inner side surface 123 is provided between the second inner side surface 122 and the third inner side surface 123 in the housing 20. The first step surface 124 and the second step surface 125 have an annular shape with the center axis CL. A state in which the fuel injection valve 100 is attached to a target object OB such as an engine is called an attachment state. The fuel injection valve 100 has a support surface 90 supported by the target object OB from the -Z side in the attachment state. In the present embodiment, the support surface 90 is provided on an outer surface of the holder 17. The first inner side surface 121 and the second inner side surface 122 are provided on the -Z side of the support surface 90.

[0024] A damper chamber 25 is defined by the second inner side surface 122, the first step surface 124, the shaft portion 41, and the small-diameter portion 57 within the housing 20. Fuel is stored in the damper chamber 25. The fuel is not completely sealed within the damper chamber 25, but the flow of fuel is restricted to such an extent that the fuel cannot freely flow into or out of the damper chamber 25. The damper chamber 25 communicates with the outside of the damper chamber 25 through a gap between the first inner side surface 121 and the shaft portion 41, a gap between the second inner side surface 122 and the small-diameter portion 57, and a gap between the shaft portion 41 and the inner wall surface of the movable core 50.In the present embodiment, the housing 20, the movable core 50, and the needle 40 are provided such that the gap between the first inner side surface 121 and the shaft portion 41, the gap between the second inner side surface 122 and the small-diameter portion 57, and the gap between the shaft portion 41 and the inner wall surface of the movable core 50 all have a dimension ranging from several micrometers to several tens of micrometers. Thus, the free entry and exit of fuel is restricted.

[0025] In the present embodiment, the housing 20 and the movable core 50 are arranged such that the gap between the third inner side surface 123 and the large-diameter portion 56 is larger than the gap between the second inner side surface 122 and the small-diameter portion 57. Therefore, the housing 20 and the movable core 50 can be easily manufactured, so that the large-diameter portion 56 slides on the third inner side surface 123, compared to a case where the gap between the third inner side surface 123 and the large-diameter portion 56 is the same size as the gap between the second inner side surface 122 and the small-diameter portion 57.

[0026] A valve opening operation for switching the fuel injection valve 100 from the valve closing state shown in Fig. 1, to the valve opening state shown in Fig. 3. As shown in Fig. 1, the injection hole 31 is closed in the valve-closing state because the valve portion 42 is in contact with the valve seat 32. In the valve-closing state, no current is supplied to the coil 70. The needle 40 is biased toward the -Z side by the first biasing member 81, and the movable core 50 is biased toward the +Z side by the second biasing member 82. Therefore, the needle 40 and the movable core 50 are stationary, while the enlarged diameter portion 43 and the large diameter portion 56 are in contact with each other. A gap is provided between the movable core 50 and the fixed core 60 so that the movable core 50 can move during the valve-opening operation.The fuel flowing in from the introduction port 14 flows in the order of the fuel introduction pipe 12, the inside of the fixed core 60, the fuel passage 44, and the connecting hole 45, and is guided to the injection hole 31. Part of the fuel flowing in from the introduction port 14 flows into the damper chamber 25 through the gap between the second inner side surface 122 and the small-diameter portion 57, the gap between the first inner side surface 121 and the shaft portion 41, and the gap between the shaft portion 41 and the inner wall surface of the movable core 50. Therefore, the damper chamber 25 is filled with fuel.

[0027] When the current supply to the coil 70 is started, a magnetic attraction force is generated between the fixed core 60 and the movable core 50, and the movable core 50 moves toward the +Z side toward the fixed core 60. The needle 40 moves together with the movable core 50 because the enlarged diameter portion 43 is pressed by the large diameter portion 56. The movement of the needle 40 causes the valve portion 42 to separate from the valve seat 32, and fuel injection from the injection hole 31 is started.

[0028] The pressure of the fuel in the damper chamber 25 decreases as the volume of the damper chamber 25 is increased or expanded by the movable core 50 moving toward the +Z side in the Z direction. Therefore, a force that decelerates the movable core 50 and the needle 40 acts on the movable core 50. When the movable core 50 collides with the fixed core 60, the movement of the movable core 50 is stopped. In other words, the fixed core 60 restricts the movement of the movable core 50 in the +Z direction. Since the movable core 50 is decelerated by the damper chamber 25, the impact force when the movable core 50 collides with the fixed core 60 is reduced.

[0029] After the movable core 50 collides with the fixed core 60, the needle 40 continues to move in the +Z direction by inertia independently of the movable core 50. Elastic energy is stored in the first biasing member 81 because the first biasing member 81 is pressed by the enlarged diameter portion 43 to contract in accordance with the movement of the needle 40. Thereafter, the needle 40 is pushed back toward the movable core 50 in the -Z direction by the elastic energy stored in the first biasing member 81. When the enlarged diameter portion 43 collides with the large diameter portion 56, the movement of the needle 40 is stopped. Since the needle 40 is decelerated by the damper chamber 25 when it moves together with the movable core 50, the elastic energy stored in the first biasing member 81 is reduced.Therefore, the impact force when the enlarged-diameter portion 43 collides with the large-diameter portion 56 is reduced. After the movement of the movable core 50 is stopped, the fuel flows into the damper chamber 25 through the gap between the second inner side surface 122 and the small-diameter portion 57 or the like. Through the series of operations described above, the fuel injection valve 100 is brought into the valve-opening state shown in FIG. Fig. 3. In the valve-opening state, a predetermined amount of fuel is injected from the injection hole 31. The fuel injection valve 100 is kept open while the current supply to the coil 70 continues.

[0030] A valve closing operation for switching the fuel injection valve 100 from the valve opening state shown in Fig. 3, to the valve closing state shown in Fig. 1. By stopping the supply of electric current to the coil 70, the magnetic attraction force between the fixed core 60 and the movable core 50 disappears. Therefore, the needle 40 is pushed by the first biasing member 81 and moves in the -Z direction. When the large-diameter portion 56 is pushed by the enlarged-diameter portion 43, the movable core 50 moves together with the needle 40 in the -Z direction.

[0031] The volume of the damper chamber 25 is reduced in accordance with the movement of the movable core 50 in the -Z direction, so that the pressure of the fuel in the damper chamber 25 increases. Therefore, a force that decelerates the movable core 50 and the needle 40 acts on the movable core 50. As the pressure of the fuel in the damper chamber 25 increases, the fuel in the damper chamber 25 gradually flows out of the damper chamber 25 through the gap between the second inner side surface 122 and the small-diameter portion 57 or the like. When the valve portion 42 collides with the valve seat 32, the movement of the needle 40 is stopped. In other words, the valve seat 32 restricts the movement of the needle 40 in the -Z direction. Since the needle 40 is decelerated by the damper chamber 25, the impact force when the valve portion 42 collides with the valve seat 32 is reduced.Since the injection hole 31 is closed by the valve portion 42 coming into contact with the valve seat 32, the injection of fuel from the injection hole 31 is stopped.

[0032] After the needle 40 collides with the valve seat 32, the movable core 50 continues to move in the -Z direction by inertia independently of the needle 40. Since the volume of the damper chamber 25 is further reduced by the movement of the movable core 50, a force for decelerating the movable core 50 acts on the movable core 50. As the second biasing member 82 is pressed by the movable core 50 to contract in accordance with the movement of the movable core 50, elastic energy is stored in the second biasing member 82. Thereafter, the movable core 50 is pushed back in the +Z direction by the elastic energy stored in the second biasing member 82. The movement of the movable core 50 is stopped by the large-diameter portion 56 contacting the enlarged-diameter portion 43.Since the movable core 50 is decelerated by the damper chamber 25, the elastic energy stored in the second biasing member 82 is reduced. Therefore, the impact when the large-diameter portion 56 contacts the enlarged-diameter portion 43 is reduced. Through the series of operations described above, the fuel injection valve 100 is placed in the valve-closing state shown in FIG. Fig. 1. In the valve closing state, fuel injection from the injection hole 31 is stopped.

[0033] According to the fuel injection valve 100 of the present embodiment, the shock generated when the valve opens / closes is reduced by the damper chamber 25, as the fuel flows into and out of the damper chamber 25 through the gap between the first inner side surface 121 of the housing 20 and the shaft portion 41 of the needle 40, the gap between the second inner side surface 122 of the housing 20 and the small-diameter portion 57 of the movable core 50, and the gap between the shaft portion 41 and the inner wall surface of the movable core 50. Various expansions may occur in the housing 20. The backup ring 91 receives pressure from the fuel via the O-ring 92, for example, when fuel is supplied to the fuel injection valve 100 from the supply pipe.At this time, an axial force along the Z direction may act on a portion of the housing 20 where the third inner side surface 123 is provided to cause elastic strain in the housing 20. In addition, when the fuel injection valve 100 is mounted on the target object OB such as an engine, the holder 17 is held by an operator or the like, and the support surface 90 is pressed against the target object OB. At this time, an axial force along the Z direction may act on a portion of the housing 20 where the third inner side surface 123 is provided, so that plastic strain may occur in the housing 20. In the present embodiment, the housing 20 is provided with the first inner side surface 121 and the second inner side surface 122 located in the radial direction inside the third inner side surface 123.Even if the above-mentioned axial force acts on the portion of the housing 20 where the third inner side surface 123 is provided, the size of the gap between the first inner side surface 121 and the shaft portion 41 and the size of the gap between the second inner side surface 122 and the small-diameter portion 57 can be restrained from changing. Therefore, it is possible to restrain the impact reduction effect of the damper chamber 25 from decreasing. In the present embodiment, the fuel injection valve 100 injects hydrogen gas, which is a gaseous fuel. Since the viscosity of the gaseous fuel is lower than that of the liquid fuel, the impact at the time the valve is opened / closed is likely to be large.Therefore, it is possible to effectively suppress the wear and failure of the movable core 50 and the like by suppressing the reduction of the impact reducing effect of the damper chamber 25.

[0034] Furthermore, in the present embodiment, since the first inner side surface 121 and the second inner side surface 122 of the housing 20 are provided on the -Z side of the support surface 90 that receives the above-described axial force, it is possible to more effectively suppress the occurrence of strain in a portion of the housing 20 provided with the first inner side surface 121 and the second inner side surface 122. Thus, it is possible to more effectively suppress the change in the size of the gap between the first inner side surface 121 and the shaft portion 41 and the size of the gap between the second inner side surface 122 and the small-diameter portion 57.

[0035] Therefore, since the gap between the third inner side surface 123 and the large-diameter portion 56 of the movable core 50 is not a gap for ensuring the impact reduction effect of the damper chamber 25, the impact reduction effect of the damper chamber 25 is hardly affected if the size of the gap between the third inner side surface 123 and the large-diameter portion 56 changes. The gap between the third inner side surface 123 and the large-diameter portion 56 is larger than the gap between the second inner side surface 122 and the small-diameter portion 57. Therefore, the large-diameter portion 56 is restricted from interfering with the third inner side surface 123 to restrict the movable core 50 from being unable to move along the Z direction.Furthermore, it is possible to restrict the large-diameter portion 56 and the third inner side surface 123 from rubbing against each other. Since the above-mentioned axial force is not transmitted to the needle 40 or the movable core 50, the size of the gap between the shaft portion 41 and the inner wall surface of the movable core 50 is unlikely to change. Second embodiment

[0036] As in Fig. As shown in Figure 4, a fuel injection valve 100b of a second embodiment differs from the first embodiment in the shape of the needle 40b, the shape of the fixed core 60b, and the arrangement of the damper chamber 25b. Other configurations and valve opening / closing operations are the same as those of the first embodiment unless otherwise specified.

[0037] The needle 40b has an extension portion 46 that protrudes from the shaft portion 41 in the +Z direction from the enlarged diameter portion 43. The extension portion 46 has a columnar shape with the central axis CL. The outer diameter of the extension portion 46 is smaller than the outer diameter of the enlarged diameter portion 43. The fuel passage 44b has an opening on the end surface of the extension portion 46 on the +Z side in the Z direction.

[0038] As in Fig. 5, the fixed core 60b includes, in order from the -Z side in the Z direction, a first core inner surface 161 and a second core inner surface 162. The enlarged diameter portion 43 slides on the first core inner surface 161 along the Z direction. The extension portion 46 slides on the second core inner surface 162 along the Z direction. Each of the first core inner surface 161 and the second core inner surface 162 has a cylindrical shape with the central axis CL. The inner diameter of the first core inner surface 161 is larger than the inner diameter of the second core inner surface 162. The fixed core 60b has a core step surface 163 connecting the first core inner surface 161 and the second core inner surface 162. The core step surface 163 has an annular shape with the central axis CL.In the present embodiment, the first core inner surface 161, the second core inner surface 162 and the core step surface 163 are provided on the second fixed core member 62.

[0039] The damper chamber 25b is divided by the enlarged diameter portion 43, the first core inner surface 161, the core step surface 163, and the extension portion 46. The inside of the damper chamber 25b communicates with the outside of the damper chamber 25b through a gap between the first core inner surface 161 and the enlarged diameter portion 43, and a gap between the second core inner surface 162 and the extension portion 46.

[0040] In the present embodiment, the gap between the second inner side surface 122b of the first tubular member 21b of the housing 20b and the small-diameter portion 57 of the movable core 50 is set larger than the gap between the second inner side surface 122 of the first tubular member 21b of the housing 20b and the small-diameter portion 57 of the movable core 50 in the first embodiment. Therefore, the space defined by the second inner side surface 122b, the first step surface 124, the shaft portion 41, and the small-diameter portion 57 does not function as a damper chamber. In the present embodiment, the second biasing member 82 is arranged in this space. The housing 20b may have the same configuration as that in the first embodiment.That is, the space enclosed by the second inner side surface 122b, the first step surface 124, the shaft portion 41, and the small-diameter portion 57 can function as a damper chamber, as in the first embodiment. The second biasing member 82 can be provided at the same position as in the first embodiment.

[0041] During the valve opening operation of the fuel injection valve 100b, the volume of the damper chamber 25b is reduced as the movable core 50 and the needle 40b move in the +Z direction, so that the movable core 50 and the needle 40b are decelerated by the damper chamber 25b. Therefore, the impact when the movable core 50 collides with the fixed core 60b is reduced. After the movable core 50 collides with the fixed core 60b, when the needle 40b moves independently of the movable core 50, the volume of the damper chamber 25b is further reduced, and the needle 40b is further decelerated. Therefore, the elastic energy stored in the first biasing member 81 is reduced. Further, when the needle 40b is pushed back to the -Z side in the Z direction by the first biasing member 81, the volume of the damper chamber 25b is expanded, so that the needle 40b is decelerated.Therefore, the impact when the enlarged diameter portion 43 collides with the large diameter portion 56 of the movable core 50 is reduced.

[0042] During the valve closing operation of the fuel injection valve 100b, the volume of the damper chamber 25b expands as the needle 40b and the movable core 50 move in the -Z direction, so the damper chamber 25b causes the needle 40b and the movable core 50 to decelerate. Since the needle 40b is decelerated, the impact when the valve portion 42 collides with the valve seat 32 is reduced. Since the movable core 50 is decelerated, the elastic energy stored in the second biasing member 82 is reduced. The impact when the large-diameter portion 56 contacts the enlarged-diameter portion 43 is reduced as the movable core 50 is pushed back to the +Z side in the Z direction by the second biasing member 82.

[0043] According to the fuel injection valve 100b, the shock at the time the valve is opened and closed is reduced by the damper chamber 25b, while the fuel flows into or out of the damper chamber 25b through the gap between the first core inner surface 161 of the fixed core 60b and the enlarged diameter portion 43 of the needle 40b, and the gap between the second core inner surface 162 of the fixed core 60b and the extended portion 46 of the needle 40b. Even if the housing 20b is distorted, the needle 40b and the fixed core 60b are hardly distorted. Therefore, the size of the gap between the first core inner surface 161 and the enlarged diameter portion 43, and the gap between the second core inner surface 162 and the extended portion 46 are restricted from changing even if the housing 20b is distorted.It is possible to restrict that the impact reducing effect of the damper chamber 25b decreases. Third embodiment

[0044] As in Fig. As shown in Fig. 6, a fuel injection valve 100c of the third embodiment includes a shim ring 26 provided in the housing 20c. The damper chamber 25c is defined by an end surface 126 of the shim ring 26 in this embodiment, rather than the first step surface 124c of the housing 20c as in the first embodiment. Other configurations and valve opening / closing operations are the same as those in the first embodiment unless otherwise specified.

[0045] As in Fig.As shown in Fig. 7, the spacer ring 26 is provided between the second inner side surface 122c of the first tubular member 21c of the housing 20c and the shaft portion 41 of the needle 40. The spacer ring 26 has a cylindrical shape with the central axis CL. The shaft portion 41 penetrates the inside of the spacer ring 26, and the shaft portion 41 slides on the inner wall surface of the spacer ring 26. In the present embodiment, the spacer ring 26 is fixed to the second inner side surface 122c by press fitting. The end surface 126 of the spacer ring 26 on the +Z side in the Z direction is arranged to face the end surface of the small diameter portion 57 of the movable core 50 on the -Z side in the Z direction.The end surface 126 is provided in the radial direction of the housing 20c between the first inner side surface 121 and the second inner side surface 122c in the housing 20c. The end surface 126 is provided to connect a step formed between the second inner side surface 122c of the housing 20c and the inner wall surface of the shim ring 26. Therefore, the end surface 126 is referred to as the third step surface 126 in the following description.

[0046] The damper chamber 25c is divided by the second inner side surface 122c, the third step surface 126, the shaft portion 41, and the small-diameter portion 57. The inside of the damper chamber 25c communicates with the outside of the damper chamber 25c through the gap between the second inner side surface 122c and the small-diameter portion 57, the gap between the shaft portion 41 and the inner wall surface of the movable core 50, and a gap between the inner wall surface of the spacer ring 26 and the shaft portion 41.

[0047] According to the fuel injection valve 100c, the volume of the damper chamber 25c can be easily adjusted by adjusting the position of the shim ring 26 in the Z direction. Therefore, the impact reduction effect of the damper chamber 25c can be easily adjusted. Other embodiment

[0048] In the embodiments, the fuel injection valve 100 to 100c includes the first inner side surface 121 and the second inner side surface 122 to 122c located on the -Z side of the support surface 90 in the Z direction. Alternatively, the second inner side surface 122 to 122c may be provided at a position intersecting the support surface 90, and the first inner side surface 121 may be provided on the -Z side of the support surface 90 in the Z direction. The second inner side surface 122 to 122c may be provided on the +Z side of the support surface 90 in the Z direction, and the first inner side surface 121 may be provided on the -Z side of the support surface 90 in the Z direction.The second inner side surface 122 to 122c may be provided on the +Z side of the support surface 90 in the Z direction, and the first inner side surface 121 may be provided at a position intersecting the support surface 90. The first inner side surface 121 and the second inner side surface 122 to 122c may be provided on the +Z side of the support surface 90 in the Z direction.

[0049] In the fuel injection valve 100 of the first embodiment and the fuel injection valve 100c of the third embodiment, the second biasing member 82 is arranged outside the damper chamber 25, 25c. However, the second biasing member 82 may be arranged inside the damper chamber 25, 25c.

[0050] In the embodiments, the first tubular member 21 to 21c of the housing 20 to 20c and the injection nozzle 30 are formed by different members in the fuel injection valve 100 to 100c. However, the first tubular member 21 to 21c and the injection nozzle 30 may be configured by a single member. In this case, the injection hole 31 and the valve seat 32 may be provided at one end of the first tubular member 21 to 21c on the -Z side in the Z direction.

[0051] In the fuel injection valve 100 to 100c, the movable core 50 includes the large-diameter portion 56 and the small-diameter portion 57, which have different outer diameters. However, the movable core 50 does not need to have portions with different outer diameters. That is, the outer diameter of the movable core 50 may be constant.

[0052] In the fuel injection valve 100 to 100c, the movable core 50 is composed of the first movable core member 51 and the second movable core member 52. However, the movable core 50 may also be composed of only the first movable core member 51.

[0053] In the fuel injection valve 100 to 100c, the fixed core 60, 60b is composed of the first fixed core member 61 and the second fixed core member 62. However, the fixed core 60, 60b may also be configured by only the first fixed core member 61.

[0054] The present disclosure should not be limited to the embodiments described above, but various other embodiments may be implemented without departing from the scope of the present disclosure. For example, the technical features in the embodiments are appropriately replaced or combined to solve some or all of the above problems or achieve some or all of the above effects. Furthermore, if the technical features are not described as essential in the present description, they may be omitted where appropriate.

Claims

[1] Fuel injection valve (100, 100c), comprising: a housing (20, 20c) having a cylindrical shape, the housing having an injection hole (31) for injecting fuel at one end of the housing in a longitudinal direction (Z); a fixed core (60) fixed in the housing; a movable core (50) arranged between said one end and said fixed core so as to be movable along the longitudinal direction in said housing; a needle (40) which opens or closes the injection hole by moving along the longitudinal direction in the housing as the movable core moves; and a coil (70) configured to generate a magnetic field for moving the movable core, wherein the housing has a first inner side surface (121), a second inner side surface (122, 122c) and a third inner side surface (123) arranged in an order starting from one side of the one end, the needle slides on the first inner side surface (121) along the longitudinal direction, the movable core slides on the second inner side surface (122, 122c) along the longitudinal direction, the second inner side surface (122, 122c) is located on an outer side of the first inner side surface (121) in a radial direction intersecting the longitudinal direction, the fixed core is fixed on the third inner side surface (123), a step surface (124, 126) is provided between the first inner side surface and the second inner side surface in the housing, a damper chamber (25, 25c) storing the fuel is defined by the second inner side surface, the step surface, the needle and the movable core, and the second inner side surface is located on an inner side of the third inner side surface in the radial direction. [2] Fuel injection valve according to claim 1, comprising a support surface (90), which is supported by a target object (OB) in a state in which the fuel injection valve is mounted on the target object (OB), starting from one side of the one end, wherein the second inner side surface is provided between the support surface and the injection hole in the longitudinal direction. [3] The fuel injection valve (100) according to claim 1 or claim 2, further comprising: a cylindrical shim ring (26) fixed between the second inner side surface and the movable core, the step surface being provided on the shim ring. [4] Fuel injection valve according to one of claims 1 to 3, wherein the fuel is a gaseous fuel. [5] Fuel injection valve according to one of claims 1 to 4, wherein the fuel is a hydrogen fuel. [6] Fuel injection valve (100b), comprising: a housing (20b) having a cylindrical shape, the housing having an injection hole (31) for injecting fuel at one end of the housing in a longitudinal direction (Z); a fixed core (60b) fixed in the housing; a movable core (50) arranged between said one end and said fixed core so as to be movable along the longitudinal direction in said housing; a needle (40b) which opens or closes the injection hole by moving along the longitudinal direction in the housing as the movable core moves; and a coil (70) configured to generate a magnetic field for moving the movable core, wherein the needle includes a shaft portion (41) provided along the longitudinal direction, an enlarged diameter portion (43) having an outer diameter larger than an outer diameter of the shaft portion, and an extension portion (46) having an outer diameter smaller than the outer diameter of the enlarged diameter portion along the longitudinal direction, the shaft section, the enlarged diameter section and the extension section are arranged in a sequence starting from one side of the one end, the fixed core has a first core inner surface (161) on which the enlarged diameter portion slides, a second core inner surface (162) on which the extension portion slides, and a core step surface (163) provided between the first core inner surface and the second core inner surface in the fixed core, the second core inner surface has an inner diameter that is smaller than an inner diameter of the first core inner surface, and a damper chamber (25b) storing the fuel is defined by the enlarged diameter portion, the extension portion, the first core inner surface and the core step surface.

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