electromagnet

Abstract

This invention provides an electromagnet that eliminates the need for a coil bobbin around which the magnet wire is wound, thereby suppressing the need for increased size. [Solution] The electromagnet is constructed by fitting a coil block 13, which is equipped with a coil 9, onto a cylindrical block 12. The cylindrical block 12 has a movable iron core 10 fitted inside that is axially slidable, and is positioned opposite a cylindrical fixed iron core 8 made of magnetic material. The coil block 13 is equipped with a plurality of thin printed circuit boards, each with a coil pattern printed on its surface and the back surface opposite the surface. The printed circuit boards are arranged in an axial direction and each coil pattern is electrically connected to form the coil 9.

Description

Technical Field

[0001] The present invention relates to an electromagnet that attracts a movable iron core to a fixed iron core by an attractive force generated by energizing a coil, and particularly to an electromagnet suitable for use in a solenoid valve.

Background Art

[0002] This type of electromagnet is provided with a movable iron core disposed opposite to a fixed iron core, and attracts the movable iron core to the fixed iron core by an attractive force generated by energizing the coil to operate the valve body of the solenoid valve. The coil is formed by winding a linear magnet wire around a cylindrical coil bobbin made of a resin material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in such a conventional electromagnet, the coil requires a coil bobbin around which the magnet wire is wound, and the coil bobbin must have flange portions at both axial ends in order to hold the wound magnet wire, resulting in a problem that the axial length increases and the whole becomes large-sized.

[0005] An object of the present invention is to provide an electromagnet that eliminates the need for a coil bobbin around which the magnet wire is wound and can suppress the increase in size.

Means for Solving the Problems

[0006] To achieve such problems, the present invention takes the following means. That is, In an electromagnet that attracts a movable iron core to a fixed iron core by the attractive force generated by energizing a coil, the electromagnet is constructed by fitting a coil block equipped with a coil onto a cylindrical block, the cylindrical block has a movable iron core that is fitted inside so as to be axially slidable and is positioned opposite a cylindrical fixed iron core made of magnetic material, and the coil block has a plurality of thin plate-shaped printed circuit boards on the surface and the back surface opposite the surface, each of which has a coil pattern printed on it, and the printed circuit boards are arranged in an axial direction and each coil pattern is electrically connected to form a coil.

[0007] In this case, the coil pattern is formed in a spiral shape, the second coil pattern printed on the back surface of the opposing first printed circuit board and the third coil pattern printed on the front surface of the second printed circuit board are formed with a radial offset from each other, the third coil pattern is positioned radially between the second coil patterns, the second coil pattern is electrically connected to the fourth coil pattern printed on the back surface of the second printed circuit board without being electrically connected to the third coil pattern, the fourth coil pattern is electrically connected to the third coil pattern, the third coil pattern is electrically connected to the fifth coil pattern printed on the front surface of the third printed circuit board which is opposite the second and first printed circuit boards, and the electrical connections of each coil pattern may be repeated in accordance with the increase in the number of printed circuit boards. [Effects of the Invention]

[0008] As described in detail above, the invention described in claim 1 comprises a plurality of thin printed circuit boards, each having a coil pattern printed on its surface and the back surface opposite to the surface, and the coils are formed by superimposing the printed circuit boards in the axial direction and electrically connecting the coil patterns. Therefore, since the coil is formed by superimposing a plurality of thin printed circuit boards, a coil bobbin for winding the magnet wire is unnecessary compared to conventional electromagnets, and the size can be suppressed.

[0009] Furthermore, in the invention described in claim 2, the coil pattern is formed in a spiral shape, and the second coil pattern printed on the back surface of the opposing first printed circuit board and the third coil pattern printed on the front surface of the second printed circuit board are formed with a radial offset from each other, and the third coil pattern is positioned between the radial lengths of the second coil pattern. Therefore, even when printed circuit boards are superimposed, the coil patterns printed on the front and back surfaces of opposing printed circuit boards do not come into contact with each other, thus further shortening the axial dimension of the coil and further suppressing its size increase. The second coil pattern is electrically connected to the fourth coil pattern printed on the back surface of the second printed circuit board without being electrically connected to the third coil pattern, the fourth coil pattern is electrically connected to the third coil pattern, and the third coil pattern is electrically connected to the fifth coil pattern printed on the front surface of the third printed circuit board that is opposite the second and first printed circuit boards, and the electrical connections of each coil pattern are repeated in accordance with the increase in the number of printed circuit boards. Therefore, since each coil pattern printed on the front and back surfaces of each printed circuit board can be electrically connected so that the current flows in the same direction, it is possible to suppress the increase in size without reducing the attractive force that attracts the movable iron core to the fixed iron core. [Brief explanation of the drawing]

[0010] [Figure 1] This is a longitudinal cross-sectional view showing an electromagnet, representing one embodiment of the present invention, applied to a solenoid valve. [Figure 2] This diagram shows one embodiment, with each printed circuit board forming the coil separated. [Figure 3] This is a schematic diagram showing one embodiment, in which the second coil pattern and the third coil pattern are represented on the same plane. [Figure 4] This is an enlarged view of the main part C in Figure 1. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows an electromagnet of one embodiment of the present invention applied to a solenoid valve. Electromagnet 1 is attached to one axial end of the valve body 3 of the solenoid valve 2. Another electromagnet 4, identical in configuration to electromagnet 1, is attached to the other axial end of the valve body 3, opposite to the axial end of the valve body 3. A terminal box T is mounted on the upper part of the valve body 3.

[0012] A fitting hole 5 is formed in the valve body 3, penetrating it axially. A spool-shaped valve body 6 is housed in the fitting hole 5 so as to be slidable in the axial direction. On the inner circumferential surface of the fitting hole 5, a supply passage P is connected approximately in the axial center, load passages A and B are spaced apart on both sides of the supply passage P in the axial direction, and a discharge passage R is spaced apart axially outward from the load passages A and B. The supply passage P is connected to a fluid pressure source, load passages A and B are connected to actuators (not shown), and the discharge passage R is connected to the low-pressure side. The valve body 6 protrudes in an annular shape, forming two lands 6A and 6B. By moving in the axial direction, the lands 6A and 6B open and close the respective passages P, A, B, and R, switching communication between each passage P, A, B, and R. Springs 7A and 7B are placed at both ends of the valve body 6 in the axial direction, and the force of the springs 7A and 7B holds the valve body 6 in a neutral position that blocks the passages P, A, B, and R.

[0013] A cylindrical fixed core 8 of the electromagnet 1 is screwed into the opening of the fitting hole 5, which is located at one axial end of the valve body 3, and the electromagnet 1 is attached and fixed to the axial end of the valve body 3 as described above. An electromagnet 4, which has the same configuration as the electromagnet 1, is attached and fixed to the opening of the fitting hole 5, which is located at the other axial end of the valve body 3, as described above. Hereafter, the explanation will be based on the electromagnet 1 as a representative example.

[0014] The electromagnet 1 operates by using the attractive force generated by energizing the coil 9 to attract the movable iron core 10 to the fixed iron core 8, thereby pressing the valve body 6 via the rod member 11. It is constructed by fitting a coil block 13, which has the coil 9, onto a cylindrical block 12, and the coil block 13 is fixed between the valve body 3 and the coil block 13 by a lock nut 14 that is screwed onto the protruding end of the cylindrical block 12.

[0015] The cylindrical block 12 is made of a magnetic material and has a cylindrical fixed core 8 that screws into the valve body 3. A cylindrical cylindrical member 15 made of a non-magnetic material is welded and fixed to the fixed core 8, and a bottomed, cylindrical yoke member 16 made of a magnetic material is further welded and fixed to the cylindrical member 15. The movable core 10 is made of a magnetic material and has a cylindrical shape. It is fitted axially slidably inside the cylindrical member 15 and the yoke member 16 and is positioned opposite the fixed core 8. The rod member 11 is fitted axially slidably at the radial center of the fixed core 8, and both axial ends abut the valve body 6 and the movable core 10, respectively. As the movable core 10 is attracted to the fixed core 8, the rod member 11 presses against the valve body 6.

[0016] The coil block 13 houses a cylindrical coil 9 with a through-hole 9A formed axially through its radial center, in a roughly cup-shaped cover member 17 made of magnetic material with a closed bottom and a through-hole 17A formed axially through its radial center, and is integrally molded with molding resin 18. 19 is a pair of connecting pins, electrically connected to the lead wires of the coil 9 and integrally molded with molding resin 18, protruding toward the terminal box T. The connecting pins 19 are inserted through the through-hole 9A and through-hole 17A into the cylindrical block 12, and the coil block 13 is fitted onto it, thereby inserting into the terminal box T and electrically connecting the coil 9 to an external power source (not shown).

[0017] The magnetic circuit that generates an attractive force to pull the movable core 10 towards the fixed core 8 by energizing the coil 9 is formed by the movable core 10, the fixed core 8, the yoke member 16, and the cover member 17.

[0018] As shown in Figure 2, the coil 9 is constructed by overlapping approximately 100 thin, disc-shaped printed circuit boards 20, 21, 22, and 23 in the axial direction. The number of printed circuit boards 20-23 can be appropriately selected from several tens to several hundred depending on the application. Below, the first printed circuit board 20, the second printed circuit board 21, the third printed circuit board 22, and the fourth printed circuit board 23 will be used as representative examples. The first to fourth printed circuit boards 20-23 each have through-holes 20A, 21A, 22A, and 23A formed at their radial centers, and these four through-holes 20A-23A constitute the insertion hole 9A for the coil 9.

[0019] The first to fourth printed circuit boards 20 to 23 are printed by forming coil patterns 20D, 21D, 22D, 23D and 20E, 21E, 22E, 23E in a spiral shape on surfaces 20B, 21B, 22B, 23B and back surfaces 20C, 21C, 22C, 23C opposite to the surfaces 20B to 23B, respectively. Hereinafter, the spiral directions of the respective coil patterns 20D, 21D, 22D, 23D and 20E, 21E, 22E, 23E shall all refer to those visually recognized from the side of the surfaces 20B to 23B.

[0020] The first coil pattern 20D printed on the surface 20B of the first printed circuit board 20 is formed in a counterclockwise spiral shape from a starting point a on the outer side in the radial direction toward an ending point b on the inner side in the radial direction. The starting point a of the first coil pattern 20D is electrically connected to one of a pair of connection pins 19 (shown in FIG. 1), and the ending point b of the first coil pattern 20D is electrically connected to a starting point c on the inner side in the radial direction of a second coil pattern 20E printed on the back surface 20C of the first printed circuit board 20.

[0021] The second coil pattern 20E is formed in a counterclockwise spiral shape from a starting point c on the inner side in the radial direction toward an ending point d on the outer side in the radial direction. The ending point d of the second coil pattern 20E is electrically connected to a starting point e on the outer side in the radial direction of a fourth coil pattern 21E printed on the back surface 21C of the second printed circuit board 21 without being electrically connected to a third coil pattern 21D printed on the surface 21B of the second printed circuit board 21 facing the first printed circuit board 20.

[0022] The fourth coil pattern 21E is formed in a counterclockwise spiral shape from a starting point e on the outer side in the radial direction toward an ending point f on the inner side in the radial direction. The ending point f of the fourth coil pattern 21E is electrically connected to a starting point g on the inner side in the radial direction of a third coil pattern 21D printed on the surface 21B through the second printed circuit board 21. The third coil pattern 21D is formed in a counterclockwise spiral shape from a starting point g on the inner side in the radial direction toward an ending point h on the outer side in the radial direction.

[0023] The endpoint h of the third coil pattern 21D is electrically connected to the radially outward starting point i of the fifth coil pattern 22D, which is printed on the surface 22B of the third printed circuit board 22, opposite the second printed circuit board 21 and the first printed circuit board 20, through the second printed circuit board 21. The fifth coil pattern 22D is formed in a counterclockwise spiral shape from the radially outward starting point i to the radially inward endpoint j. The endpoint j of the fifth coil pattern 22D is electrically connected to the radially inward starting point k of the sixth coil pattern 22E, which is printed on the back surface 22C, through the third printed circuit board 22.

[0024] The sixth coil pattern 22E is formed in a counterclockwise spiral shape from a radially inward starting point k to a radially outward ending point l. The ending point l of the sixth coil pattern 22E is electrically connected to the radially outward starting point m of the eighth coil pattern 23E, which is printed on the back surface 23C of the fourth printed circuit board 23, without being electrically connected to the seventh coil pattern 23D printed on the surface 23B of the fourth printed circuit board 23, which is opposite the third printed circuit board 22 and the second printed circuit board 21.

[0025] The eighth coil pattern 23E is formed in a counterclockwise spiral shape from a radially outward starting point m to a radially inward ending point n. The ending point n of the eighth coil pattern 23E is electrically connected to the radially inward starting point o of the seventh coil pattern 23D, which penetrates the fourth printed circuit board 23 and is printed on the surface 23B. The seventh coil pattern 23D is formed in a counterclockwise spiral shape from a radially inward starting point o to a radially outward ending point p. The ending point p of the seventh coil pattern 23D is electrically connected to the other of a pair of connection pins 19 (shown in Figure 1). In this way, since each coil pattern 20D, 20E, 21D, 21E, 22D, 22E, 23D, and 23E is formed in a counterclockwise spiral shape, current can flow in the same direction, and this can be done without reducing the attractive force that attracts the movable iron core 10 to the fixed iron core 8. Then, as the number of printed circuit boards increases, the electrical connections of each coil pattern 20D to 23E are repeated in accordance with this increase in number.

[0026] As shown in Figure 3, the second coil pattern 20E (formed on the back surface 20C of the first printed circuit board 20) and the third coil pattern 21D (formed on the front surface 21B of the second printed circuit board 21) are formed with a radial offset from each other, and the third coil pattern 21D is positioned between the second coil pattern 20E so that they do not come into contact with each other.

[0027] Similarly, as shown in Figure 2, the fourth coil pattern 21E and the fifth coil pattern 22D are formed with a radial offset from each other, with the fifth coil pattern 22D positioned between the fourth coil pattern 21E so that they do not come into contact with each other. In addition, the sixth coil pattern 22E and the seventh coil pattern 23D are formed with a radial offset from each other, with the seventh coil pattern 23D positioned between the sixth coil pattern 22E so that they do not come into contact with each other.

[0028] As shown in Figure 4, the third coil pattern 21D is positioned between the second coil patterns 20E. Therefore, even when the first printed circuit board 20 and the second printed circuit board 21 are superimposed, the second coil pattern 20E and the third coil pattern 21D do not come into contact with each other. Similarly, the fifth coil pattern 22D is positioned between the fourth coil patterns 21E, and the seventh coil pattern 23D is positioned between the sixth coil patterns 22E. Therefore, even when the second printed circuit board 21 and the third printed circuit board 22 are superimposed, the fourth coil pattern 21E and the fifth coil pattern 22D do not come into contact with each other, and even when the third printed circuit board 22 and the fourth printed circuit board 23 are superimposed, the sixth coil pattern 22E and the seventh coil pattern 23D do not come into contact with each other. As a result, the axial dimension of the coil 9 can be made even shorter. Z1, Z2, and Z3 are insulating layers that insulate against electricity. Insulating layer Z1 is interposed between the second coil pattern 20E and the third coil pattern 21D, insulating layer Z2 is interposed between the fourth coil pattern 21E and the fifth coil pattern 22D, and insulating layer Z3 is interposed between the sixth coil pattern 22E and the seventh coil pattern 23D.

[0029] Next, we will explain how this configuration works. Figure 1 shows the state where the coil 9 is not energized, and the movable core 10 is stopped at a position axially separated to the right from the fixed core 8. The valve body 6 is in the neutral position, blocking the passages P, A, B, and R.

[0030] In this state, when current is applied to the coil 9, an attractive force is generated that draws the movable core 10 to the fixed core 8. The movable core 10 slides to the left in the diagram and is attracted to the fixed core 8, and the rod member 11 presses the valve body 6 to the left in the diagram. The valve body 6 slides to the left in the diagram, switching the load passage A to the supply passage P and switching the load passage B to the discharge passage R.

[0031] In this state, when the coil 9 is de-energized, the attractive force that draws the movable core 10 to the fixed core 8 is eliminated, and the valve body 6 slides to the right in the diagram due to the force of the spring 7B, returning to the position shown, and blocking the passages P, A, B, and R. The movable core 10 is pressed to the right in the diagram by the rod member 11, separating from the fixed core 8 and returning to the position shown.

[0032] Furthermore, in the state shown in Figure 1, when the other electromagnet 4 is energized, the valve body 6 slides to the right in the diagram, switching the load passage A to the discharge passage R and switching the load passage B to the supply passage P. Then, when the electromagnet 4 is de-energized, the valve body 6 slides to the left in the diagram due to the force of the spring 7A and returns to the position shown, blocking the passages P, A, B, and R.

[0033] In this operation, the coil block 13 comprises multiple thin printed circuit boards 20-23, each with coil patterns 20D-23D and 20E-23E printed on its front surface 20B-23B and back surface 20C-23C, respectively. The printed circuit boards 20-23 are superimposed in the axial direction, and the coil patterns 20D-23D and 20E-23E are electrically connected to form the coil 9. Therefore, since the coil 9 is formed by superimposing multiple thin printed circuit boards 20-23, a coil bobbin for winding the magnet wire is unnecessary compared to conventional electromagnets, thus suppressing the need for increased size.

[0034] Furthermore, the coil patterns 20D~23D and 20E~23E are formed in a spiral shape, and the second coil pattern 20E printed on the back surface 20C of the opposing first printed circuit board 20 and the third coil pattern 21D printed on the front surface 21B of the second printed circuit board 21 are formed with a radial offset from each other, with the third coil pattern 21D positioned between the radially aligned second coil patterns 20E. Therefore, even when the printed circuit boards 20~23 are superimposed, the coil patterns 20E, 21D or 21E, 22D or 22E, 23D printed on the front and back surfaces 20C, 21B or 21C, 22B or 22C, 23B of the opposing printed circuit boards 20, 21 or 21, 22 or 22, 23 do not come into contact with each other, thus further shortening the axial dimension of the coil 9 and further suppressing its size increase. Then, the second coil pattern 20E is electrically connected to the fourth coil pattern 21E printed on the back surface 21C of the second printed circuit board 21 without being electrically connected to the third coil pattern 21D, the fourth coil pattern 21E is electrically connected to the third coil pattern 21D, and the third coil pattern 21D is electrically connected to the fifth coil pattern 22D printed on the front surface 22B of the third printed circuit board 22, which is opposite the second printed circuit board 21 and the first printed circuit board 20. The electrical connections of each coil pattern 20D~23D, 20E~23E are repeated in accordance with the increase in the number of printed circuit boards 20~23. Therefore, the coil patterns 20D, 20E, 21D, 21E, 22D, 22E, 23D, and 23E printed on the front and back surfaces 20B, 20C, 21B, 21C, 22B, 22C, 23B, and 23C of each printed circuit board 20-23 can be electrically connected so that the current flows in the same direction. This allows for a reduction in size while maintaining the attractive force that draws the movable iron core 10 to the fixed iron core 8.

[0035] In the embodiment described above, the coil block 13 was clamped between the valve body 3 and the lock nut 14, but a C-shaped retaining ring may also be attached to the yoke member 16 of the cylindrical block 12 to clamp the coil block 13 between the valve body 3 and the lock nut 14. Also, although the solenoid valve 2 is equipped with two electromagnets 1 and 4 to actuate the valve body 6, it is of course possible to equip it with only one electromagnet 1. [Explanation of Symbols]

[0036] 1, 4: Electromagnet 8: Fixed iron core 9: Coil 10: Movable core 12: Cylindrical block 13: Coil Block 20, 21, 22, 23: Printed circuit board 20B, 21B, 22B, 23B: Surface 20C, 21C, 22C, 23C: Back side 20D, 20E, 21D, 21E, 22D, 22E, 23D, 23E: Coil Pattern

Claims

1. An electromagnet that attracts a movable iron core to a fixed iron core by an attractive force generated by energizing a coil, wherein the electromagnet is constructed by fitting a coil block equipped with a coil onto a cylindrical block, the cylindrical block is provided with a movable iron core that is axially slidable inside and is positioned opposite a cylindrical fixed iron core made of magnetic material, and the coil block is provided with a plurality of thin plate-shaped printed circuit boards on the front surface and the back surface opposite the front surface, respectively, and the printed circuit boards are arranged in an axial direction to superimpose each other and electrically connect each coil pattern to form a coil.

2. The electromagnet according to claim 1, characterized in that the coil pattern is formed in a spiral shape, the second coil pattern printed on the back surface of the opposing first printed circuit board and the third coil pattern printed on the front surface of the second printed circuit board are formed with a radial offset from each other, the third coil pattern is positioned radially between the second coil patterns, the second coil pattern is electrically connected to the fourth coil pattern printed on the back surface of the second printed circuit board without being electrically connected to the third coil pattern, the fourth coil pattern is electrically connected to the third coil pattern, the third coil pattern is electrically connected to the fifth coil pattern printed on the front surface of the third printed circuit board which is opposite the second printed circuit board and the first printed circuit board, and the electrical connection of each coil pattern is repeated in accordance with the increase in the number of printed circuit boards.

Images