JP2010025066A - Fuel injection valve and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a hardly separable oil repellent coating film layer in the vicinity of an injection hole, in a fuel injection valve. <P>SOLUTION: In a method for manufacturing the fuel injection valve having the injection hole for injecting fuel, a silicone oxide layer is formed on a member surface of the injection side opening end of the injection hole (Step S14). Next, the oil repellent coating film layer is formed on a surface of the silicone oxide layer (Step S16). The coating film layer is uniformly and densely brought into close contact with an OH group possessed by silicone oxide of the member surface. The hardly separable oil repellent coating film layer is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection valve in which an oil-repellent coating layer is formed on an injection hole and a member in the vicinity thereof, and a manufacturing method thereof.

In the fuel injection valve, deposits may be formed in the injection hole and in the vicinity thereof due to unburned components returning from the combustion chamber and fuel returning including carbon. The deposit may block the injection hole, and the injection flow rate of the fuel injection valve may decrease.
To solve the above problem, for example, Patent Document 1 discloses a technique for forming a film layer having oil repellency in the vicinity of an injection hole to reduce the above-described deposit formation.

JP-A-9-112392

When a coating layer is formed on the injection hole and the member in the vicinity thereof, even if the coating layer is simply formed on the surface of the member, sufficient bonding between the member and the coating layer cannot be obtained, and the fuel injection valve is being used. There is a possibility that the coating layer may be peeled off.
The present invention solves the above problems. The present invention provides a technique for forming an oil-repellent coating layer excellent in binding properties with members around the injection hole of a fuel injection valve.

  In order to solve the above problems, the fuel injection valve of the present invention has an injection hole for injecting fuel, and a silicon oxide layer is formed on the surface of a member constituting the injection side opening end of the injection hole. Furthermore, a coating layer having oil repellency is formed on the surface of the silicone oxide layer.

  Some oil-repellent coating layers are rich in reactivity with OH groups. Therefore, the fuel injection valve of the present invention has a silicone oxide layer between the member and the coating layer. In addition to chemical bonding with the metal member surface, the silicon oxide is also physically bonded by an anchor effect or the like, so that adhesion to the member surface is higher than that of the oil-repellent coating layer. In addition, there are many OH groups on the surface of the silicon oxide (the surface in contact with the atmosphere). Therefore, the silicon oxide layer functions as an adhesive layer that firmly bonds the metal member and the oil-repellent coating. By interposing the silicone oxide layer, an oil-repellent coating layer that is difficult to peel can be obtained.

  The member that forms the silicone oxide layer and the oil-repellent coating layer may be only the orifice plate that forms the injection side opening end of the injection hole. The orifice plate may be made of stainless steel, for example. When forming the coating layer on the silicon oxide layer, it is preferable to form the coating layer before the orifice plate is assembled to the fuel injection valve. However, the coating layer is formed after the orifice plate is assembled to the fuel injection valve. May be.

  The coating layer having the oil-repellent property described above is preferably a monomolecular fluorine compound of 50 nm or less having a silane group at the end. In particular, a silane-modified perfluoropolyether compound (silane-modified PFPE) is preferable. The silane group is changed to a silanol group by a demethanol reaction with moisture in the atmosphere. The silanol group is particularly reactive with the OH group and has a strong bond with the silicon oxide layer that forms a dense OH group on the surface. In addition, both the silanol group and the silicone oxide have good compatibility because they have a partial molecular structure in which silicone and OH are connected. Specifically, the OH group of silicone oxide densely present on the surface of the member and the OH group of the terminal group of silane-modified PFPE (OH group formed by demethanol reaction) undergo a dehydration reaction to form a strong siloxane bond. . At this time, the silane group side of the silane-modified PFPE is positioned on the member side, and the PFPE group side having oil repellency is positioned on the outer surface side. Such a bond forms a strong and dense coating layer.

  In the coating layer containing the PFPE compound, fluorine molecules are arranged in a standing state with respect to the surface of the member. In this configuration, the molecular chain of the fluorine molecule easily rotates at the ether bond (C—O—C) portion. Moreover, since the coupling | bond part with a member is flexible, the molecular chain itself can be easily rotated with respect to a member. Therefore, it is difficult to prevent the oil droplets formed on the surface of the coating layer from moving, and the oil droplets easily fall off from the surface of the coating layer.

  The present invention also provides a method for manufacturing the above-described fuel injection valve. The fuel injection valve manufacturing method includes a step of forming a silicone oxide layer on the surface of a member constituting the injection side opening end of the injection hole, and a step of forming a coating layer having oil repellency on the surface of the silicone oxide layer. Contains. According to this manufacturing method, it is possible to form an oil-repellent coating layer having excellent bonding properties with a member.

  According to the present invention, it is possible to provide a fuel injection valve in which a coating layer that reduces the formation of deposits is difficult to peel off.

The main technical features of the fuel injection valve of the embodiment are listed.
(Mode 1) The surface roughness of the silicone oxide layer is smaller than the surface roughness of the member. By doing so, the surface roughness of the coating layer can be reduced compared to the case where the coating layer is formed directly on the member surface. By reducing the surface roughness of the coating layer, it is possible to improve the slidability of oil droplets on the surface of the coating layer.
(Mode 2) The silicone oxide layer is colored. It is convenient if the presence or absence of a silicon oxide layer and a coating layer can be visually confirmed in a factory. Silicone oxide can be colored at a lower cost than the oil repellent film without impairing the oil repellency. By coloring the silicone oxide layer, coloring for visual confirmation can be performed at low cost.
(Mode 3) The fuel injection valve includes a main body and a valve body accommodated in the main body. The main body includes a body, a core fixed in the body, and a valve seat fixed to one end of the body and having a fuel injection hole. The valve body accommodated in the main body is located between the core and the valve seat. The valve body moves between a first position where one end abuts the valve seat and closes the fuel injection hole, and a second position where one end is separated from the valve seat and the other end abuts the core.
(Mode 4) An orifice plate having a fuel injection hole is provided at one end of the valve seat.
(Mode 5) The actuator includes a solenoid. The core and the valve body are formed using a magnetic material, and when the solenoid is energized, the core and the valve body are magnetized.

  A preferred fuel injection valve embodying the present invention will be described with reference to the drawings. FIG. 1 shows a longitudinal sectional view of a fuel injection valve 10 of the embodiment. FIG. 2 is an enlarged view of the vicinity of the injection hole 42 of the fuel injection valve 10. As shown in FIG. 1, the fuel injection valve 10 includes a main body 12, a valve body 30, a compression spring 24, and a solenoid 26.

A fuel flow path 20 through which fuel passes is formed inside the main body 12. An arrow A in FIG. 1 indicates the fuel passing direction. A fuel injection hole 42 is formed at the downstream end 12 d of the main body 12. A fuel pipe (not shown) extending from a fuel tank (not shown) is connected to the upstream end 12 c of the main body 12. The fuel flow path 20 communicates from the upstream end 12 c of the main body 12 to the fuel injection hole 42.
In this specification, the expressions “upstream” and “downstream” mean “upstream with respect to the fuel passage direction A” and “downstream with respect to the fuel passage direction A”, respectively. That is, the expressions “upstream” and “downstream” correspond to “upper” and “lower” in FIG. 1, respectively.

  The configuration of the main body 12 will be described in more detail. As shown in FIG. 1, the main body 12 includes a body 14, a core 16, a spring pin 22, a valve seat holder 32, and a valve seat 34.

  The body 14 is a cylindrical member that constitutes the outline of the main body 12. The body 14 is made of resin. A connector 48 connected to an external control unit (not shown) is formed on the outer peripheral surface of the body 14. The connector 48 is provided with a plurality of terminal pins 49 that are electrically connected to the solenoid 26.

  The core 16 is a hollow cylindrical member formed of a magnetic material, and is fixed to the through hole 14 a of the body 14. A part of the core 16 protrudes upstream from the through hole 14 a of the body 14. The downstream end 16 d of the core 16 is located in the through hole 14 a of the body 14. The through hole 16 a of the core 16 constitutes a part of the fuel flow path 20. A filter 18 for removing foreign matter from the fuel is provided in the through hole 16a of the core 16. The core 16 is located on the upstream side of the valve body 30.

  The spring pin 22 is press-fitted into the through hole 16 a of the core 16. The spring pin 22 is located on the upstream side of the compression spring 24 and is in contact with the upstream end 24 c of the compression spring 24. The spring pin 22 is a member for adjusting the compression amount of the compression spring 24 by adjusting the press-fitting position. The spring pin 22 is a hollow cylindrical member, and the through hole 22 a constitutes a part of the fuel flow path 20.

  The valve seat holder 32 is a cylindrical member and is fixed to the through hole 14 a of the body 14. The valve seat holder 32 is located on the downstream side of the core 16, and a part of the valve seat holder 32 projects downstream from the through hole 14 a of the body 14. The valve body 30 is accommodated in the through hole 32 a of the valve seat holder 32. Between the through hole 32 a of the valve seat holder 32 and the valve body 30, a gap constituting a part of the fuel flow path 20 is formed. At the upstream end of the valve seat holder 32, a cylindrical sleeve 28 formed of a nonmagnetic material is provided. A downstream end 16 d of the core 16 and an upstream end 30 c of the valve body 30 are located in the through hole 28 a of the sleeve 28. The valve body 30 is slidable with respect to the through hole 28 a of the sleeve 28.

  The valve seat 34 is a bottomed cylindrical member, and is fixed to the through hole 32 a of the valve seat holder 32. The downstream portion of the valve body 30 is located in the inner hole 34 b of the valve seat 34. A gap that constitutes a part of the fuel flow path 20 is formed between the inner hole 34 b of the valve seat 34 and the valve body 30. An orifice plate 38 is provided on the downstream end face of the valve seat 34. The valve seat 34 and the orifice plate 38 are located at the downstream end 12 d of the main body 12. Each of the valve seat 34 and the orifice plate 38 is formed with through holes 34 a and 38 a constituting the fuel injection hole 42. Here, although only one through hole 38a is shown in FIGS. 1 and 2, a plurality of through holes 38a may be formed in a region corresponding to the through hole 34a. The orifice plate 38 is fixed to the downstream end face of the valve seat 34 by a plate folder 39. A silicone oxide layer 43 and a coating layer 44 are formed on the downstream end face of the orifice plate 38 and the inner surface of the through hole 38a (see FIG. 4). The orifice plate 38, the silicon oxide layer 43, and the coating layer 44 will be described in detail later.

  Next, the configuration of the valve body 30 will be described. The valve body 30 is a bottomed cylindrical member and is made of a magnetic material. The valve body 30 is accommodated in the through hole 32a of the valve seat holder 32, and is supported so as to be slidable in a direction parallel to the fuel passing direction A. The downstream end 24 d of the compression spring 24 is in contact with the valve body 30.

  The upstream end 30 c of the valve body 30 faces the downstream end 16 d of the core 16 that is a part of the main body 12. A closing portion 36 for closing the fuel injection hole 42 is provided at the downstream end of the valve body 30. The inner hole 30 a of the valve body 30 communicates with the through hole 16 a of the core 16 and constitutes a part of the fuel flow path 20. A plurality of through holes 30 b are formed in the side wall of the valve body 30, and the inner hole 30 a of the valve body 30 communicates with the gap between the inner hole 34 b of the valve seat 34 and the valve body 30.

  As shown in FIG. 2, the valve body 30 is movable between a first position where the fuel injection hole 42 is closed and a second position where the fuel injection hole 42 is opened. The first position is a movement limit on the downstream side (fuel injection hole 42 side) of the valve body 30, and the second position is a movement limit on the upstream side of the valve body 30. When the valve body 30 is in the first position, the closing portion 36 that is the downstream end of the valve body 30 comes into contact with the valve seat 34 and the fuel injection hole 42 is closed. At this time, the upstream end 30 c of the valve body 30 is separated from the downstream end 16 d of the core 16. On the other hand, when the valve body 30 is in the second position, the closing portion 36 that is the downstream end of the valve body 30 is separated from the valve seat 34 and the fuel injection hole 42 is opened. At this time, the upstream end 30 c of the valve body 30 is in contact with the downstream end 16 d of the core 16.

  Next, the compression spring 24 and the solenoid 26 will be described. The compression spring 24 is accommodated in the through hole 16 a of the core 16. The compression spring 24 is positioned between the spring pin 22 and the valve body 30 in a compressed state. An upstream end 24 c of the compression spring 24 is in contact with the spring pin 22, and a downstream end 24 d of the compression spring 24 is in contact with the valve body 30. The compression spring 24 urges the valve body 30 to the first position, which is the movement limit on the downstream side, by its elastic force.

  The solenoid 26 is fixed in the through hole 14 a of the body 14. The solenoid 26 surrounds a part including the downstream end 16 c of the core 16. The solenoid 26 is energized by an external control unit (not shown) through the terminal pin 49 of the connector 48. A current is passed through the solenoid 26 at a timing at which fuel should be injected. The solenoid 26 generates a magnetic field when a current is applied.

  Next, the operation of the fuel injection valve 10 will be described. Fuel flows into the main body 12 of the fuel injection valve 10 from a fuel pipe (not shown) connected to the upstream end 12c. The inflowing fuel passes through the fuel flow path 20 and reaches the fuel injection hole 42 formed at the downstream end 12d in the main body 12. When no current is supplied to the solenoid 26, the valve body 30 is maintained at the first position by the urging force of the compression spring 24 (see FIG. 2). In this case, since the fuel injection hole 42 is closed by the closing part 36 of the valve body 30, fuel is not injected from the fuel injection hole 42.

  On the other hand, when a current is passed through the solenoid 26 and the solenoid 26 generates a magnetic field, the core 16 and the valve body 30 become magnetized. The core 16 and the valve body 30 attract each other, and the valve body 30 moves to the second position on the upstream side against the urging force of the compression spring 24. The closing portion 36 of the valve body 30 is separated from the valve seat 34, and the fuel injection hole 42 is opened. At this time, fuel is injected from the fuel injection hole 42. Normally, current is intermittently supplied to the solenoid 26 and fuel is intermittently injected from the fuel injection hole 42.

The overall structure and operation of the fuel injection valve 10 of this embodiment have been described above. Next, a method for manufacturing the orifice plate 38 will be described in detail.
FIG. 3 is a flowchart showing a procedure for manufacturing the orifice plate 38. First, in the machining process of step S10, a metal (for example, stainless steel) base material is processed to produce a disk-shaped plate. A through hole 38a is formed near the center of the plate. Next, ultrasonic cleaning is performed with the prepared plate immersed in a cleaning solution such as acetone (step S12). This cleaning step is performed, for example, at room temperature for 3 minutes. Next, a silicon oxide layer is deposited on one surface of the cleaned plate (step S14). For the formation of the silicon oxide layer, a well-known method such as vacuum deposition or dipping may be used. The thickness of the silicone oxide layer is 1.0 μm or less, preferably 0.5 μm or less. This thickness is determined to be a value that is negligible compared to the diameter of the injection hole 42 (about 0.2 mm) so as not to hinder fuel ejection.
Further, a slight amount of colorant is mixed in the deposited silicon oxide. That is, a colored silicone oxide layer is formed by step S14.

Next, a film having oil repellency is formed on the surface of the silicone oxide layer (step S16). The plate on which the silicon oxide layer is formed is immersed in a solution adjusted to the components of the coating layer to form a coating layer. As this liquid agent, for example, silane-modified perfluoropolyether (silane-modified PFPE) in which a silane group is bonded to perfluoropolyether (PFPE) that is an oil-repellent component (including an oil-repellent group) is used as a main agent. In this liquid agent, perfluorohexane is mixed as a solvent.
The OH group of the silicone oxide layer and the OH group of the silane-modified PFPE are bonded together by a dehydration reaction to form a PFPE coating layer (oil repellent coating layer). The OH group of the silicone oxide layer is formed on the surface of the layer by the reaction of the silicon oxide (SiO ₂ ) with moisture in the air prior to the reaction with the silane-modified PFPE.

  Next, the plate is dried (step S18), and the orifice plate 38 is completed. As shown in FIG. 4, a silicon oxide layer 43 is formed on the inner surface of the through hole 38a extending from the opening end 38b on the injection side of the through hole 38a and the surface 38c of the orifice plate 38, and a coating layer 44 is formed thereon. The The coating layer 44 is formed with a substantially constant film thickness, and the thickness is about 5 nm.

5 to 8 schematically show a process in which the silicone oxide layer 43 on the surface of the orifice plate 38 and the silane-modified PFPE are bonded to form a coating layer. The reaction proceeds in the order of FIG. 5 to FIG.
FIG. 5 shows the orifice plate 38 before the coating layer is deposited. Silicone oxide has good adhesion to the metal and is densely and uniformly formed on the entire surface of the orifice plate 38. In the orifice plate 38 before forming the coating layer, moisture in the air is adsorbed, and OH groups are formed on the surface of the silicone oxide layer 43. OH groups are densely distributed over the entire surface of the silicone oxide layer 43.
FIG. 6 shows the orifice plate 38 (orifice plate 38 before the reaction with the silane-modified PFPE) immersed in the liquid agent. Reference numeral 62 represents silane-modified PFPE. The letter “R” in the molecular structure of silane-modified PFPE represents a CH ₃ group.
FIG. 7 shows the demethanol reaction of silane-modified PFPE. Silane-modified PFPE undergoes demethanol reaction with moisture in the atmosphere. As a result, the CH ₃ group (letter “R” in FIG. 6) is replaced with hydrogen, and an OH group is generated.
FIG. 8 shows a dehydration reaction by the OH group of the silane-modified PFPE and the OH group of the silicone oxide layer 43. As a result of the dehydration reaction, the silane-modified PFPE and the silicone oxide layer are bonded to each other through a siloxane bond, and a PFPE coating layer 44 is formed. The silane group side of the silane-modified PFPE is aligned with the orifice plate 38 side, and the PFPE group side is aligned with the outside. A coating layer 44 in which PFPE groups are closely arranged on the surface is formed.

  FIG. 9 is a schematic cross-sectional view of the orifice plate 38 on which the silicone oxide layer 43 and the coating layer 44 are formed. The symbol Ra1 represents the surface roughness of the metal surface of the orifice plate 38. Reference numeral Ra <b> 2 represents the surface roughness of the silicone oxide layer 43. The symbol Ra3 represents the surface roughness of the coating layer 44. The surface roughness Ra2 of the silicon oxide layer 43 is smaller than the surface roughness Ra1 of the metal surface of the orifice plate 38. The surface roughness Ra3 of the coating layer 44 is substantially equal to the surface roughness Ra2 of the silicone oxide layer 43. In the fuel injection valve of the present embodiment, the surface roughness Ra3 of the coating layer 44 is small as compared with the case where the coating layer is formed directly on the metal surface of the orifice plate 38. This is due to the following reason. The coating layer 44 is formed of a single molecule of several nm having a relatively uniform molecular weight. Therefore, when the coating layer is formed directly on the metal surface of the orifice plate 38, a coating layer having a surface roughness equivalent to the surface roughness of the metal surface is formed.

  The orifice plate 38 on which the coating layer 44 is formed is fixed to the downstream end face of the valve seat 34 by a plate folder 39. The orifice plate 38 may be fixed to the downstream end face of the valve seat 34 in advance, and the coating layer 44 may be formed on the fixed orifice plate 38 and the valve seat 34.

The fuel injection valve 10 of the present embodiment has the following advantages.
(1) The silicone oxide layer 43 enhances the adhesion of the oil-repellent coating layer 44 containing silane-modified PFPE. In other words, the silicon oxide layer 43 reduces peeling of the coating layer 44. This advantage is obtained by uniformly and densely depositing the silicone oxide layer 43 on the metal surface of the orifice plate 38 prior to the formation of the coating layer 44. This method is more effective than immersing the orifice plate in a solvent in which an oil repellent component (for example, a PFPE compound) and an OH group supply component (for example, silicone oxide) are mixed. This is because when a mixed solution is used, a layer in which PFPE and silicone oxide are mixed is formed. Moreover, when a mixed solution is used, PFPE and silicone will be mixed on the surface of the coating layer. The coating layer of the present example is not only difficult to peel off but also excellent in oil repellency as compared with a coating layer formed using a mixed solution.
In addition, the adhesiveness between the coating layer and the metal surface can also be improved by using an inorganic oxide comprising an OH group-containing inorganic oxide, inorganic halide, or a composite thereof instead of silicone oxide. . Examples of such inorganic materials include inorganic oxides such as ZrO ₂ , Al ₂ O ₃ , Y ₂ O ₃ , and TiO ₂ , MgF ₂ , BaF ₂ , CaF ₂ , LaF ₂ , LiF, NaF, and SrF ₂ . There are inorganic halides. However, a silicone oxide layer is preferred for enhancing the adhesion between the coating layer containing the silane-modified PFPE and the metal surface. This is due to the following two reasons. First, since both the silicon oxide and the silanol group changed from the silane group of the silane-modified PFPE have a partial molecular structure in which silicone and OH are connected, they are compatible. Second, the density of OH groups in silicone oxide is higher than the density of OH groups formed by other inorganic compounds and inorganic halides.

(2) By interposing the silicon oxide layer 43, the surface roughness of the coating layer 44 can be reduced. As a result, it is possible to improve the slipping property of oil droplets on the coating surface.
(3) In the fuel injection valve 10 of this embodiment, the silicone oxide layer is colored. Therefore, it is possible to easily visually check whether or not the coating has been performed at the factory. PFPE, which is the main component of the coating layer, has a transparent molecular structure of several nanometers and cannot be confirmed visually. Also, PFPE is very difficult to color. On the other hand, silicone oxide can be easily colored at low cost. “Coloring” in the present specification includes not only coloring with a fluorescent material or a dye, but also enhancing the gloss of the film by, for example, mixing iron ions or aluminum ions into silicone oxide.

  In the embodiment described above, the coating layer 44 is formed on the orifice plate 38 alone and then fixed to the valve seat 34. However, the coating layer 44 may be formed after the orifice plate 38 is assembled to the valve seat 34 in advance. In this case, stratification is performed by dipping in the liquid agent in a state where the orifice plate 38 is fixed to the valve seat 34. Thereafter, the coating layer 44 is formed by drying. This method is particularly useful for fuel injectors that do not have an orifice plate 38.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The longitudinal cross-sectional view of a fuel injection valve. The figure which shows the state which has a valve body in a 1st position. The flowchart which shows the manufacture procedure of an orifice plate. The longitudinal cross-sectional view of an orifice plate. The schematic diagram (1) which shows the process in which a silicon oxide layer and a silane modified PFPE are bonded together. The schematic diagram (2) which shows the process in which a silicon oxide layer and a silane modification PFPE couple | bond together. The schematic diagram (3) which shows the process in which a silicon oxide layer and a silane modification PFPE couple | bond together. The schematic diagram (4) which shows the process in which a silicon oxide layer and a silane modification PFPE couple | bond together. The typical sectional view of a silicon oxide layer and a coating layer.

Explanation of symbols

10: Fuel injection valve 12: Body 14: Body 16: Core 18: Filter 20: Fuel flow path 22: Spring pin 24: Compression spring 26: Solenoid 28: Sleeve 30: Valve body 32: Valve seat holder 34: Valve seat 36 : Blocking part 38: Orifice plate 39: Plate folder 42: Injection hole 43: Silicon oxide layer 44: Coating layer 102: Coating layer 104: Bonding layer

Claims (4)

  A silicon oxide layer is formed on the surface of the member that has an injection hole for injecting fuel, and forms the injection side opening end of the injection hole, and a film layer having oil repellency is formed on the surface of the silicone oxide layer The fuel injection valve characterized by the above-mentioned.   The fuel injection valve according to claim 1, wherein the member is an orifice plate that forms an injection side opening end of the injection hole.   The fuel injection valve according to claim 1 or 2, wherein the coating layer contains a silane-modified perfluoropolyether compound. A method of manufacturing a fuel injection valve having an injection hole for injecting fuel,
A step of stratifying a silicon oxide layer on the surface of the member constituting the injection side opening end of the injection hole;
Forming a film layer having oil repellency on the surface of the silicone oxide layer;
A fuel injection valve manufacturing method comprising:

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