Fuel injection device

A fuel injection device comprising:

• a nozzle that includes an injection hole, through which fuel is injected, and a valve seat, which is formed around the injection hole and is shaped into a ring form;
• a housing that is shaped into a tubular form and has one end connected to the nozzle, wherein the housing has a fuel passage, which is formed in an inside of the housing and is communicated with the injection hole;
• a needle that has:
• a needle main body, which is shaped into a rod form;
• a seal portion, which is formed at one end of the needle main body such that the seal portion is contactable with the valve seat;
• and
• a flange, which is formed on a radially outer side of the needle main body at another end of the needle main body or around the another end of the needle main body, wherein the needle is installed such that the needle is reciprocatable in the fuel passage, and when the seal portion is lifted away from or is seated against the valve seat, the needle opens or closes the injection hole;
• a movable core that is installed such that the movable core is movable relative to the needle main body and has a surface, which is opposite from the valve seat and is contactable with a surface of the flange located on the valve seat side;
• a stationary core that is installed on an opposite side of the movable core, which is opposite from the valve seat, in the inside of the housing;
• a gap forming member that has:
• a plate portion that is placed on the opposite side of the needle, which is opposite from the valve seat, such that one end surface of the plate portion is contactable with the needle;
• and
• an extending portion that is formed to extend from the plate portion toward the valve seat, while an opposite end part of the extending portion, which is opposite from the plate portion, is contactable with the surface of the movable core located on the stationary core side, wherein the gap forming member is configured to form an axial gap, which is a gap defined in an axial direction between the flange and the movable core, when the plate portion and the extending portion are in contact with the needle and the movable core, respectively;
• and
• a valve seat side spring that is placed on the opposite side of the gap forming member, which is opposite from the valve seat, wherein the valve seat side spring is operable to urge the needle and the movable core toward the valve seat through the gap forming member;
• a coil that is operable to attract the movable core toward the stationary core side such that the movable core contacts the flange and drives the needle toward the opposite side, which is opposite from the valve seat, when the coil is energized;
• and
• a guide that is placed on the valve seat side of the movable core in the inside of the housing and wherein an outer wall of the needle main body is slidable relative to the guide to guide reciprocation of the needle, wherein:
• the gap forming member is formed such that a first wall surface of the gap forming member, which is a wall surface opposed to an outer wall of the flange, forms a radial gap, which is a gap defined in a radial direction, between the first wall surface and the outer wall of the flange, and a second wall surface of the gap forming member, which is a wall surface opposed to an inner wall of the stationary core, is slidable relative to the inner wall of the stationary core.

A fuel injection device comprising:

• a nozzle that includes an injection hole, through which fuel is injected, and a valve seat, which is formed around the injection hole and is shaped into a ring form;
• a housing that is shaped into a tubular form and has one end connected to the nozzle, wherein the housing has a fuel passage, which is formed in an inside of the housing and is communicated with the injection hole;
• a needle that has:
• a needle main body, which is shaped into a rod form;
• a seal portion, which is formed at one end of the needle main body such that the seal portion is contactable with the valve seat;
• and
• a flange, which is formed on a radially outer side of the needle main body at another end of the needle main body or around the another end of the needle main body, wherein the needle is installed such that the needle is reciprocatable in the fuel passage, and when the seal portion is lifted away from or is seated against the valve seat, the needle opens or closes the injection hole;
• a movable core that is installed such that the movable core is movable relative to the needle main body and has a surface, which is opposite from the valve seat and is contactable with a surface of the flange located on the valve seat side;
• a stationary core that is installed on an opposite side of the movable core, which is opposite from the valve seat, in the inside of the housing;
• a gap forming member that has:
• a plate portion that is placed on the opposite side of the needle, which is opposite from the valve seat, such that one end surface of the plate portion is contactable with the needle;
• and
• an extending portion that is formed to extend from the plate portion toward the valve seat, while an opposite end part of the extending portion, which is opposite from the plate portion, is contactable with the surface of the movable core located on the stationary core side, wherein the gap forming member is configured to form an axial gap, which is a gap defined in an axial direction between the flange and the movable core, when the plate portion and the extending portion are in contact with the needle and the movable core, respectively;
• and
• a valve seat side spring that is placed on the opposite side of the gap forming member, which is opposite from the valve seat, wherein the valve seat side spring is operable to urge the needle and the movable core toward the valve seat side through the gap forming member;
• and
• a coil that is operable to attract the movable core toward the stationary core such that the movable core contacts the flange and drives the needle toward the opposite side, which is opposite from the valve seat, when the coil is energized, wherein:
• the gap forming member is formed such that a first wall surface of the gap forming member, which is a wall surface opposed to an outer wall of the flange, is slidable relative to the outer wall of the flange, and a second wall surface of the gap forming member, which is a wall surface opposed to an inner wall of the stationary core, is slidable relative to the inner wall of the stationary core;
• and
• all of the first wall surface, the second wall surface, the outer wall of the flange and the inner wall of the stationary core are surface processed through a slide resistance reducing process, which reduces a slide resistance relative to another member, or a hardening process.