JP5003509B2 - Manufacturing method of solenoid valve - Google Patents

Description

The present invention relates to a method of manufacturing a solenoid valve for controlling the flow rate of a fluid. For example, in a high-pressure pump used in a common rail system for a diesel engine, a method for manufacturing a solenoid valve for adjusting the fuel discharge flow rate of the pump. It is suitable for use.

  In an electromagnetic valve using a cylindrical stator in which a thin portion is formed in the middle in the axial direction, no magnetic flux flows through the movable core and no attractive force is generated until the thin portion is magnetically saturated. Further, the attractive force is reduced by the amount of magnetic flux flowing through the thin wall portion.

  In view of this, the electromagnetic valve disclosed in Patent Document 1 is designed to increase the magnetic resistance of the thin portion by subjecting the stator to soft nitriding in order to avoid a decrease in attractive force. That is, when soft nitriding is performed, a hardened layer and a diffusion layer are formed, but the hardened layer and the diffusion layer have low permeability and less magnetic flux flows. The flowing magnetic flux can be reduced.

In addition, in the electromagnetic valve shown in Patent Document 2, a permanent magnet is disposed on the outer peripheral side of the thin portion so as to magnetically saturate the thin portion in order to avoid a decrease in attractive force. Furthermore, in order to avoid a reduction in attractive force, the electromagnetic valve disclosed in Patent Document 3 is formed with a plurality of holes in the thin portion to increase the magnetic resistance of the thin portion.
JP 2002-106740 A JP 2001-68335 A JP 2002-243057 A

  However, the electromagnetic valve disclosed in Patent Document 1 has a problem that since the entire stator is subjected to soft nitriding, the magnetic resistance of the surface other than the thin portion is increased uniformly and the attractive force is reduced.

  Moreover, since the solenoid valve shown in Patent Document 2 requires a permanent magnet, the cost is correspondingly high, and the permanent magnet may be damaged due to vibration or the like.

  Furthermore, since the solenoid valve shown in Patent Document 3 needs to be drilled, the cost is increased by that amount, and if it is a through hole, liquid enters the coil side and cannot be made into a dry coil. . Moreover, the mechanical strength of a thin-walled part will also fall by opening a hole.

  In view of the above points, an object of the present invention is to increase the attractive force in an electromagnetic valve using a cylindrical stator in which a thin portion is formed.

In order to achieve the above object, according to the first aspect of the present invention, a cylindrical stator (1) in which a magnetic path is formed and a thin portion (13) is formed in an axially intermediate portion, and a stator (1) A coil (3) arranged on the outer peripheral side and forming a magnetic field when energized, and a movable core (2) arranged on the inner peripheral side of the stator (1) and attracted in one direction by energizing the coil (3) A first step of processing the stator (1) into a final finished shape, and an outer peripheral surface and an inner surface of the thin portion (13) in the stator (1) after the first step . A second step of masking a portion other than the peripheral surface with a jig (6a to 6d) with a gap of 2 mm or less, and a third step of performing glow discharge between the masked stator (1). A thin portion (1) of the stator (1) ) Only and performing plasma nitriding process.

  According to this, nitriding treatment of only the thin portion (13) can be easily performed. The magnetic permeability of the thin wall portion (13) is reduced, and the magnetic permeability of the stator (1) in the thick portion other than the thin wall portion (13) is not lowered, so that the attractive force can be increased. For this reason, it is possible to obtain a solenoid valve having a sufficiently increased attractive force without increasing the attractive force by using a permanent magnet or by forming a hole in the thin wall portion (13) without magnetic saturation at a low current. Can do.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. Of the first to fourth embodiments described below, the embodiments of the invention described in the claims are the first and fourth embodiments, and the second and third embodiments are reference examples.
(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of a solenoid valve according to the first embodiment.

  As shown in FIG. 1, the electromagnetic valve includes a stator 1, a movable core 2, a coil 3, and a housing 4 as main components.

  The stator 1 forms a magnetic path, and is made of a soft magnetic material such as electromagnetic stainless steel (such as ferritic stainless steel SUS13) or low carbon steel (such as S10C). The stator 1 has a bottomed cylindrical shape. More specifically, a cylindrical cylinder hole 11 into which the movable core 2 is slidably inserted is formed in the stator 1 so as to extend in the stator axial direction. One end of the cylinder hole 11 is closed by the bottom 12, and the other end of the cylinder hole 11 is an opening.

  In the stator 1, two stator portions 14 and 15 are formed by a thin portion 13 formed at an intermediate portion in the stator axial direction. Hereinafter, the stator portion 14 positioned on the bottom 12 side of the thin portion 13 is referred to as a first stator portion, and the stator portion 15 positioned on the side opposite to the bottom portion of the thin portion 13 (that is, the opening side of the cylinder hole 11). It is called a second stator part.

  A flange portion 16 is formed on the outer peripheral side of the second stator portion 15. The second stator portion 15 has a stator communication hole 17 that communicates the outer peripheral side of the second stator portion 15 and the cylinder hole 11 on the opposite bottom side of the flange portion 16 (that is, the opening side of the cylinder hole 11). Is formed.

  The movable core 2 forms a magnetic path and is made of a soft magnetic material such as pure iron or low carbon steel. The movable core 2 is cylindrical. More specifically, the movable core 2 is formed with a vertical hole 21 penetrating from one end to the other end in the movable core axial direction. A movable core communication hole 22 that communicates with the outer peripheral surface is formed.

  The movable core 2 is inserted into the cylinder hole 11 of the stator 1, the spring 5 is accommodated in the space between the movable core 2 and the bottom portion 12, and a stopper for preventing the movable core 2 from coming off at the opening of the cylinder hole 11. 18 is press-fitted and fixed. The movable core 2 is urged by the spring 5 so as to contact the stopper 18.

  The coil 3 is formed in a cylindrical shape by winding a coil wire around a bobbin, and is disposed on the outer peripheral side of the stator 1 to form a magnetic field when energized. The housing 4 forms a magnetic path, is made of a magnetic metal material, is formed in a substantially cylindrical shape, and is disposed so as to surround the coil 3.

  The stator 1 is subjected to a surface treatment for reducing the magnetic permeability only in the thin portion 13 of the stator 1. Carburizing, nitriding, soft nitriding, and the like are effective as treatments for reducing the permeability. In particular, nitride is formed on the material surface by generating plasma by glow discharge in a nitriding atmosphere. Plasma nitriding is desirable.

  Here, a method of performing the plasma nitriding process only on the thin portion 13 of the stator 1 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the main part showing a process (masking process) during the plasma nitriding process.

  As shown in FIG. 2, after the stator 1 is processed into a final finished shape, portions other than the thin portion 13 in the stator 1 are masked with jigs 6a to 6d such as metal. At this time, since glow discharge does not occur in a gap of 2 mm or less, masking is performed so that a gap between a portion that is not to be nitrided (that is, a portion other than the thin portion 13 in the stator 1) and the jigs 6a to 6d is 2 mm or less. To do.

  Then, the masked stator 1 as shown in FIG. 2 is put in a case of a nitriding atmosphere, and glow discharge is performed between the stator 1 serving as a cathode and the anode. By the plasma generated by this glow discharge, only the thin portion 13 in the stator 1 is subjected to nitriding treatment.

  When the coil 3 is not energized, the solenoid valve configured as described above is biased to the position where the movable core 2 abuts against the stopper 18 by the spring 5 as shown in FIG. The communication with the communication hole 22 is blocked (ie, the valve is closed).

  On the other hand, when the coil 3 is energized, a magnetic path is formed with the housing 4, the first stator portion 14, the movable core 2, the second stator portion 15, and the flange portion 16 as paths, and an attractive force is generated to move the coil 3. The core 2 is sucked toward the bottom 12 side. That is, when the coil 3 is energized, the movable core 2 is attracted toward the bottom portion 12 against the urging force of the spring 5, and the stator communication hole 17 and the movable core communication hole 22 communicate with each other. At this time, the movable core 2 stops at a point where the suction force and the biasing force of the spring 5 are balanced. The stop position of the movable core 2 is determined by the amount of current supplied to the coil 3, and when the amount of current is increased, the communication area (that is, the flow path area) between the stator communication hole 17 and the movable core communication hole 22 increases.

  Here, since the stator 1 is subjected to surface treatment for reducing the magnetic permeability only in the thin portion 13 of the stator 1, the magnetic permeability of the thin portion 13 is lowered. For this reason, even if the current is low, the thin portion 13 is magnetically saturated, and the magnetic flux flowing through the thin portion 13 is reduced. Further, since the magnetic permeability of the thick portion other than the thin portion 13 in the stator 1 is not lowered, the magnetic flux flowing outside the thin portion 13 does not decrease. As described above, the magnetic flux flowing through the thin portion 13 (magnetic flux that does not contribute to the generation of the attractive force) is reduced, and the magnetic flux flowing other than the thin portion 13 (magnetic flux that can contribute to the generation of the attractive force) is not reduced. .

  FIG. 3 is a characteristic diagram showing the attractive force of the electromagnetic valve of this embodiment and the attractive force of a conventional electromagnetic valve. The electromagnetic valve of the present embodiment is such that only the thin portion 13 of the stator 1 is subjected to a surface treatment for reducing the magnetic permeability, and the conventional electromagnetic valve is subjected to a surface treatment for reducing the magnetic permeability of the entire stator 1. It is a thing. Then, the current value was set in four stages (1A, 1.5A, 2A, 2.5A), and the suction force was measured. In FIG. 3, the solid line is the measurement result of the attractive force of the electromagnetic valve of the present embodiment, and the broken line is the measurement result of the attractive force of the conventional electromagnetic valve.

  As can be seen from FIG. 3, it was confirmed that the electromagnetic valve of the present embodiment has an increased attractive force as compared with the conventional electromagnetic valve. For example, when the current value is 1 A, the attractive force of the electromagnetic valve of this embodiment is increased by 14% compared to the conventional electromagnetic valve.

  In addition, unlike the conventional solenoid valve, the solenoid valve of the present embodiment does not use a permanent magnet or form a hole in the thin-walled portion 13, so that it can be a low-cost and highly reliable solenoid valve. .

  Further, in the plasma nitriding process using glow discharge, the nitriding process of only the thin portion 13 can be easily performed by masking the portion other than the thin portion 13 with a jig such as metal. Further, since glow discharge does not occur in a gap of 2 mm or less, masking may be performed so that a portion that is not to be processed becomes a gap of 2 mm or less. That is, since a gap of 2 mm at maximum is allowed, the accuracy of the masking jigs 6a to 6d may be rough and can be easily implemented.

  In the electromagnetic valve according to the present embodiment, the movable core 2 and the stator 1 are directly slid. Therefore, after the surface treatment for reducing the magnetic permeability of the thin portion 13 is performed, the inner peripheral surface of the stator 1 ( That is, it is desirable to subject the cylinder hole 11) to surface hardening treatment such as hard Cr plating or electroless Ni plating in order to improve wear resistance.

  Further, in the present embodiment, the plasma nitriding treatment is adopted as the surface treatment for reducing the magnetic permeability of only the thin portion 13 of the stator 1, but the portion where the nitriding treatment is not desired (that is, the portion other than the thin portion 13 in the stator 1). If the gap between the jigs 6a to 6d is set to several microns, it becomes difficult for the processing liquid or gas to enter or leave the gap, so the gap between the parts that are not to be nitrided and the jigs 6a to 6d is set to several microns. Further, salt bath soft nitriding or gas soft nitriding can be used.

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 4 is a cross-sectional view showing a method for manufacturing the stator 1 in the electromagnetic valve according to the second embodiment. In the present embodiment, the method of performing the surface treatment for reducing the magnetic permeability only on the thin portion 13 of the stator 1 is changed, and the other points are the same as the first embodiment.

  As shown in FIG. 4, after processing the stator 1 into a final finished shape, the portions other than the thin portion 13 (broken line portion in FIG. 4) in the stator 1 are masked with Ni plating or the like to expose only the thin portion 13. (I.e., only the thin-walled portion 13 is not masked). In this state, the surface treatment is performed only on the thin portion 13 by performing a surface treatment (for example, gas soft nitriding) to reduce the magnetic permeability.

  Therefore, the permeability of only the thin portion 13 of the stator 1 is reduced, and the magnetic permeability of portions other than the thin portion 13 of the stator 1 is not reduced. Therefore, the magnetic flux flowing through the thin portion 13 is reduced, and the thin portion 13 The magnetic flux flowing through the other is not decreased, and the attractive force is increased.

  Note that the Ni plating for masking may be left as it is, or may be peeled off after the surface treatment is performed.

(Third embodiment)
A third embodiment of the present invention will be described. FIG. 5 is a cross-sectional view showing a method for manufacturing the stator 1 in the electromagnetic valve according to the third embodiment. In the present embodiment, the method of performing the surface treatment for reducing the magnetic permeability only on the thin portion 13 of the stator 1 is changed, and the other points are the same as the first embodiment.

  As shown in FIG. 5, first, the stator 1 is processed into a shape in which portions other than the thin portion 13 in the stator 1 are thickened. Specifically, the final finished shape of the stator 1 indicated by a chain line in FIG. 5 is provisionally cut with an extra thickness of, for example, 0.3 mm except for the thin portion 13. Next, a surface treatment (for example, gas soft nitriding) for reducing the magnetic permeability is performed on the thickened stator 1. Thereafter, the portion that has been fleshed is cut to finish the stator 1 to the final finished dimensions. In this way, by cutting the thickened portion, the hardened layer and the diffusion layer by the surface treatment of the portion are removed, and the stator 1 is in a state in which the hardened layer and the diffusion layer by the surface treatment remain only in the thin portion 13. .

  Therefore, the permeability of only the thin portion 13 of the stator 1 is reduced, and the magnetic permeability of portions other than the thin portion 13 of the stator 1 is not reduced. Therefore, the magnetic flux flowing through the thin portion 13 is reduced, and the thin portion 13 The magnetic flux flowing through the other is not decreased, and the attractive force is increased.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. FIG. 6 is a cross-sectional view of a solenoid valve according to the fourth embodiment. In the first embodiment, the movable core 2 and the stator 1 are slid directly. However, in the present embodiment, the movable core 2 and the stator 1 are not directly slid. In addition, the same code | symbol is attached | subjected to the same or equivalent part as 1st Embodiment, and the description is abbreviate | omitted.

  In the solenoid valve of the present embodiment, as shown in FIG. 6, a rod 23 is fixed to the movable core 2 by press-fitting or the like. A first bearing 71 is disposed inside the first stator portion 14 of the stator 1. A metal valve body 81 formed in a cylindrical shape is disposed inside the second stator portion 15 of the stator 1, and a second bearing 72 is disposed in the valve body 81 and has a bottom. A metal valve element 82 formed in a cylindrical shape is slidably inserted. The rod 23 is slidably held by the first bearing 71 and the second bearing 72 so that the movable core 2 and the stator 1 do not slide. The rod 23 is in contact with the valve body 82, and the valve body 82 moves following the movement of the movable core 2 and the rod 23.

  In the solenoid valve of this embodiment, since the movable core 2 and the stator 1 do not slide, it is not necessary to consider the wear resistance of the inner peripheral surface of the stator 1 (that is, the cylinder hole 11). It is not necessary to subject the peripheral surface to a surface hardening treatment such as hard Cr plating or electroless Ni plating.

It is sectional drawing of the solenoid valve which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the stator 1 in the solenoid valve of FIG. It is a characteristic view which shows the attraction force of the solenoid valve of 1st Embodiment and the conventional solenoid valve. It is sectional drawing which shows the manufacturing method of the stator 1 in the solenoid valve which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the stator 1 in the solenoid valve which concerns on 3rd Embodiment of this invention. It is sectional drawing of the solenoid valve which concerns on 4th Embodiment of this invention.

Explanation of symbols

1 Stator 2 Movable Core 3 Coil 13 Thin Wall

Claims (1)

A cylindrical stator (1) that forms a magnetic path and has a thin-walled portion (13) formed in an intermediate portion in the axial direction;
A coil (3) disposed on the outer peripheral side of the stator (1) to form a magnetic field when energized;
A method of manufacturing an electromagnetic valve comprising a movable core (2) disposed on the inner peripheral side of the stator (1) and attracted in one direction by energization of the coil (3),
A first step of processing the stator (1) into a final finished shape;
After this first step, a second portion of the stator (1) other than the outer peripheral surface and inner peripheral surface of the thin portion (13) is masked with a jig (6a-6d) in a state where the gap is 2 mm or less. Process,
A third step of performing glow discharge with the stator (1) in a masked state,
A method for manufacturing an electromagnetic valve, wherein plasma nitriding is performed only on the thin portion (13) of the stator (1).

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