Electromagnetic solenoid

Abstract

To provide an electromagnetic solenoid that can reduce the magnetic flux generated between the convex and concave portions in a direction different from the operating direction of the movable iron core, even when the current supplied to the coil during adsorption and holding is reduced, compared to conventional designs. [Solution] The electromagnetic solenoid 100 comprises a bobbin 2 made of a non-magnetic material, a fixed core 3, a movable core 4, a biasing member 7, a coil 8, a drive circuit, and a yoke 1 made of a magnetic material. The end of the movable core 4 facing the fixed core 3 has a protrusion 4b that projects toward the fixed core 3, and a groove 4g that extends around the entire circumference of the base portion 4f of the protrusion 4b. The fixed core 3 has a recess 3b that opens toward the end of the fixed core 3 facing the movable core 4. When the movable core 4 is attracted to the fixed core 3, the protrusion 4b is positioned in the recess 3b, and a first gap 15a is formed between the outer surface of the protrusion 4b and the inner surface of the recess 3b by the groove 4g.

Description

Technical Field

[0001] The present disclosure relates to an electromagnetic solenoid including a fixed iron core and a movable iron core.

Background Art

[0002] Conventionally, an electromagnetic solenoid including a fixed iron core and a movable iron core arranged to face each other in the axial direction is known. As this type of electromagnetic solenoid, for example, the techniques disclosed in Patent Documents 1 and 2 are known.

[0003] Patent Document 1 discloses a technique in which, in order to increase the attracting force during an attracting operation in which a movable iron core is attracted toward a fixed iron core, a convex portion is provided at the central portion in the radial direction of the movable iron core, and a concave portion is provided at the central portion in the radial direction of the fixed iron core, and the convex portion is arranged in the concave portion during the attracting operation.

[0004] During the attracting and holding operation for holding the state in which the movable iron core is attracted to the fixed iron core, since the attracting force is greater than that during the attracting operation, even if the ampere-turns of the electromagnetic solenoid are reduced, the state in which the movable iron core is attracted to the fixed iron core can be maintained. Therefore, Patent Document 2 discloses a technique in which, during the attracting and holding operation, the current flowing through the coil is reduced compared to the attracting operation to reduce the heat generation of the electromagnetic solenoid.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As disclosed in Patent Document 1, providing a convex portion on the movable core and a concave portion on the fixed core is effective in increasing the suction force during the suction operation. However, in the technology disclosed in Patent Document 1, as in the technology disclosed in Patent Document 2, if the current supplied to the coil during suction and holding is reduced, a large amount of magnetic flux tends to be generated between the convex portion and the concave portion in a direction different from the direction of movement of the movable core. This leads to a problem in that the suction force that holds the movable core to the fixed core decreases.

[0007] This disclosure has been made in view of the above, and aims to provide an electromagnetic solenoid that can reduce the magnetic flux generated between the convex portion and the concave portion in a direction different from the operating direction of the movable iron core, even when the current supplied to the coil during adsorption and holding is reduced, compared to conventional methods. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the electromagnetic solenoid according to this disclosure comprises a cylindrical bobbin made of a non-magnetic material, a fixed core disposed on the inner circumference of the bobbin, a movable core disposed on the inner circumference of the bobbin so as to be axially movable and facing the fixed core in the axial direction, and a biasing member that biases the movable core away from the fixed core. The electromagnetic solenoid according to this disclosure also comprises a coil that generates a magnetic force that causes the movable core to be attracted toward the fixed core against the biasing force of the biasing member, a drive circuit that reduces the current flowing through the coil when the movable core is attracted toward the fixed core compared to when it is being attracted, and a yoke made of a magnetic material that houses the bobbin, the fixed core, the movable core, the biasing member, and the coil. The end of the movable core facing toward the fixed core has a convex portion that protrudes toward the fixed core and a groove that extends around the entire circumference of the base of the convex portion. The fixed core has a recess formed at the end of the fixed core facing the movable core. When the movable core is held in place by the fixed core, a protrusion is positioned within the recess, and a groove forms a first gap between the outer surface of the protrusion and the inner surface of the recess. [Effects of the Invention]

[0009] The electromagnetic solenoid according to this disclosure has the effect of reducing the magnetic flux generated between the convex and concave portions in a direction different from the operating direction of the movable iron core, even when the current supplied to the coil during adsorption and holding is reduced, compared to conventional designs. [Brief explanation of the drawing]

[0010] [Figure 1] Cross-sectional view showing the state of the electromagnetic solenoid during adsorption and holding according to Embodiment 1. [Figure 2] Perspective view showing the fixed iron core in Embodiment 1 [Figure 3] Perspective view showing the movable iron core in Embodiment 1 [Figure 4] This figure shows an example of the configuration of a control circuit for driving an electromagnetic solenoid according to Embodiment 1. [Figure 5] Cross-sectional view showing the state of the electromagnetic solenoid according to Embodiment 1 when it is not energized. [Figure 6] This is an explanatory diagram of the operation of the drive circuit in Embodiment 1, showing the relationship between the voltage across the coil and time. [Figure 7] This is an explanatory diagram of the operation of the drive circuit in Embodiment 1, showing the relationship between the current flowing through the coil and time. [Figure 8] Cross-sectional view showing the flow of magnetic flux during the attraction and holding of a conventional electromagnetic solenoid. [Figure 9] Cross-sectional view showing the flow of magnetic flux during the adsorption and holding of the electromagnetic solenoid according to Embodiment 1. [Figure 10] Cross-sectional view showing the magnetic flux flow at the start of the attraction operation of a conventional electromagnetic solenoid. [Figure 11] Cross-sectional view showing the magnetic flux flow at the start of the magnetic attraction operation of the electromagnetic solenoid according to Embodiment 1. [Figure 12] Cross-sectional view showing the state of the electromagnetic solenoid at the start of its attraction operation according to Embodiment 2. [Figure 13] Perspective view showing the cylindrical member in Embodiment 2 [Figure 14]Cross-sectional view showing the flow of magnetic flux at the start of the attracting operation of a conventional electromagnetic solenoid [Figure 15] Cross-sectional view showing the flow of magnetic flux at the start of the attracting operation of the electromagnetic solenoid according to Embodiment 2 [Figure 16] Cross-sectional view showing the state at the start of the attracting operation of the electromagnetic solenoid according to Embodiment 3 [Figure 17] Cross-sectional view showing the flow of magnetic flux at the start of the attracting operation of the electromagnetic solenoid according to Embodiment 3, showing the case where the third gap is small [Figure 18] Cross-sectional view showing the flow of magnetic flux at the start of the attracting operation of the electromagnetic solenoid according to Embodiment 3, showing the case where the third gap is large

Mode for Carrying Out the Invention

[0011] Hereinafter, the electromagnetic solenoid according to the embodiment will be described in detail based on the drawings.

[0012] Embodiment 1. FIG. 1 is a cross-sectional view showing the state at the time of attracting and holding of the electromagnetic solenoid 100 according to Embodiment 1. The electromagnetic solenoid 100 includes a yoke 1, a bobbin 2, a fixed core 3, a movable core 4, a shaft 5, a cylindrical member 6, a biasing member 7, a coil 8, and a drive circuit 9 (see FIG. 4). The fixed core 3 is formed in a cylindrical shape having a central axis C. Hereinafter, when explaining the direction of each component of the electromagnetic solenoid 100, the direction parallel to the central axis C is the axial direction, the direction orthogonal to the central axis C is the radial direction, and the rotational direction centered on the central axis C is the circumferential direction.

[0013] The yoke 1 is a member made of a magnetic material that houses the bobbin 2, the fixed core 3, the movable core 4, a part of the shaft 5, the cylindrical member 6, the biasing member 7, and the coil 8. The magnetic material is, for example, a magnetic metal material. The yoke 1 constitutes the outer shell of the electromagnetic solenoid 100. The yoke 1 has a bottomed cylindrical base 1a whose one axial end is open, and a lid portion 1b that closes the opening at one axial end of the base 1a.

[0014] The base portion 1a includes a bottom wall 1c and a peripheral wall 1d. The bottom wall 1c is a disc-shaped portion extending in the radial direction. A through hole 1e for passing the shaft 5 is formed in the radial center of the bottom wall 1c. The through hole 1e penetrates the bottom wall 1c in the axial direction. The peripheral wall 1d is a cylindrical portion extending in the axial direction from the outer edge of the bottom wall 1c. The end of the peripheral wall 1d opposite to the bottom wall 1c is an open end. The lid portion 1b is fixed to the open end of the base portion 1a. The lid portion 1b is a disc-shaped portion extending in the radial direction. A through hole 1f for passing the movable iron core 4 is formed in the radial center of the lid portion 1b.

[0015] The bobbin 2 is a cylindrical member made of a non-magnetic material. The non-magnetic material is, for example, a resin material. The shape of the bobbin 2 is a cylindrical shape extending in the axial direction. Flanges 2a are formed at both ends of the bobbin 2 in the axial direction, projecting radially outward. An annular step portion 2b is formed on the inner circumferential surface of the bobbin 2 in the middle of the axial direction, projecting radially inward (towards the inner circumference).

[0016] The fixed core 3 is a cylindrical member positioned on the inner circumference of the bobbin 2. The fixed core 3 has a cylindrical shape that extends in the axial direction. The fixed core 3 is positioned sandwiched between the annular step portion 2b and the bottom wall 1c in the axial direction. The outer surface of the fixed core 3 is in contact with the inner surface of the bobbin 2. The fixed core 3 is fixed to the bottom wall 1c of the yoke 1. One end of the fixed core 3 in the axial direction is the end of the fixed core 3 that faces the movable core 4. The other end of the fixed core 3 in the axial direction is the end of the fixed core 3 that is located on the opposite side from the movable core 4 and faces the bottom wall 1c of the yoke 1. An annular fixed-side contact surface 3a parallel to the radial direction is formed at one end of the fixed core 3 in the axial direction. The fixed contact surface 3a contacts the annular step portion 2b from the other axial direction, and the movable core 4 contacts the movable contact surface 4a of the movable core 4, described below, while the movable core 4 is attracted to the fixed core 3. Hereinafter, the state in which the movable core 4 is attracted to the fixed core 3 may be referred to as the state of attraction and holding.

[0017] A recess 3b is formed in the radial center of the fixed core 3, opening to one end of the fixed core 3 in the axial direction. The recess 3b is radially inward from the fixed-side contact surface 3a and opens to one end of the fixed core 3 in the axial direction. When the movable core 4 is attracted to the fixed core 3, a protrusion 4b is positioned within the recess 3b. The inner wall surface of the recess 3b includes a first tapered portion 3c and a first straight portion 3d. The first tapered portion 3c and the first straight portion 3d constitute the inner circumferential surface of the recess 3b. Figure 2 is a perspective view showing the fixed core 3 in Embodiment 1. As shown in Figure 2, the first tapered portion 3c is a tapered surface that gradually decreases in diameter from one end to the other in the axial direction of the fixed core 3. The first straight portion 3d is a surface formed with a constant inner diameter along the axial direction, continuous with the first tapered portion 3c.

[0018] As shown in Figure 1, the inner wall surface of the recess 3b further includes the recess bottom surface 3e. The recess bottom surface 3e is an annular surface that is continuous with the first straight portion 3d and extends radially inward from the first straight portion 3d. The recess bottom surface 3e is continuous with the end of the first straight portion 3d that is on the opposite side from the first tapered portion 3c. The fixed core 3 has a through hole 3f formed therein for inserting a part of the shaft 5. The through hole 3f penetrates from the radial center of the recess bottom surface 3e to the other axial end of the fixed core 3. The through hole 3f communicates with the recess 3b and the through hole 1e. The through hole 3f has a smaller inner diameter than the recess 3b and is formed with a constant inner diameter along the axial direction.

[0019] The movable core 4 is a member that is axially movable on the inner circumference of the bobbin 2 and faces the fixed core 3 in the axial direction. The movable core 4 is axially movable along the bobbin 2 and the cylindrical member 6. One axial end of the movable core 4 is the end of the movable core 4 that faces the fixed core 3. The other axial end of the movable core 4 is the end of the movable core 4 that is located on the opposite side of the fixed core 3 and is the end that retracts in and out of the yoke 1 through the through hole 1f. An annular movable-side contact surface 4a parallel to the radial direction is formed on one axial end of the movable core 4. The movable-side contact surface 4a contacts the fixed-side contact surface 3a of the fixed core 3 when adsorbing and holding.

[0020] A convex portion 4b is formed at the radial center of one axial end of the movable core 4, projecting toward the fixed core 3. The convex portion 4b is radially inward from the movable side contact surface 4a and protrudes toward the fixed core 3 toward the movable side contact surface 4a. The outer circumferential surface of the convex portion 4b includes a second straight portion 4c and a second tapered portion 4d. Figure 3 is a perspective view showing the movable core 4 in Embodiment 1. As shown in Figure 3, the second straight portion 4c is a surface formed with a constant outer diameter along the axial direction from the base portion 4f of the convex portion 4b toward the tip 4e. The second tapered portion 4d is a tapered surface that is continuous with the second straight portion 4c and gradually decreases in diameter toward the tip 4e of the convex portion 4b.

[0021] As shown in Figure 1, the tip 4e of the protrusion 4b extends radially inward from the second tapered portion 4d, continuing from the second tapered portion 4d. The tip 4e of the protrusion 4b is continuous with the end of the second tapered portion 4d that is on the opposite side from the second straight portion 4c. The tip 4e of the protrusion 4b is in contact with the annular stopper portion 5a of the shaft 5, which will be described later, from one axial direction.

[0022] The protrusion 4b has a first portion 4h and a second portion 4i. The first portion 4h is a cylindrical portion formed with a constant outer diameter along the axial direction. The first portion 4h includes a base portion 4f and a second straight portion 4c. The second portion 4i is a frustoconical portion that is continuous with the first portion 4h and tapers from the first portion 4h toward the bottom surface 3e of the recess. The second portion 4i includes a second tapered portion 4d and a tip portion 4e.

[0023] An annular groove 4g is formed at one axial end of the movable core 4, extending around the entire circumference of the base portion 4f of the protrusion 4b. Specifically, in the radial direction, a groove 4g is formed between the protrusion 4b and the movable side contact surface 4a, recessed in a direction away from the fixed core 3. The protrusion 4b and the movable side contact surface 4a are positioned radially apart from each other via the groove 4g.

[0024] The movable core 4 has a mounting hole 4j into which a part of the shaft 5 is attached. The mounting hole 4j opens at the tip 4e of the protrusion 4b. The mounting hole 4j extends a predetermined length from the radial center of the tip 4e of the protrusion 4b toward the other end of the movable core 4 in the axial direction.

[0025] The shaft 5 is a cylindrical member that moves axially together with the movable iron core 4. An annular stopper portion 5a is formed on the outer circumference of the shaft 5 at a point midway along the axial direction, projecting radially outward. One portion of the shaft 5 along the axial direction, with the annular stopper portion 5a in between, is inserted into the mounting hole 4j. The other portion of the shaft 5 along the axial direction, with the annular stopper portion 5a in between, is positioned in the recess 3b, the insertion hole 3f, and the through hole 1e, and protrudes to the outside of the yoke 1 through the through hole 1e.

[0026] The cylindrical member 6 is a cylindrical member positioned inside the yoke 1 between the bobbin 2 and the movable core 4 and fixed to the inner circumferential surface of the bobbin 2. The cylindrical member 6 has a cylindrical shape that extends in the axial direction. The cylindrical member 6 plays a role in increasing the magnetic flux generated between the movable core 4 and the fixed core 3 during the attraction operation in which the movable core 4 is attracted toward the fixed core 3. The cylindrical member 6 is sandwiched in the axial direction between the lid portion 1b and the annular step portion 2b. The outer circumferential surface of the cylindrical member 6 is in contact with the inner circumferential surface of the bobbin 2. The cylindrical member 6 is fixed to the lid portion 1b of the yoke 1. In this embodiment, the end portion 6a of the cylindrical member 6 facing the fixed core 3 and the annular step portion 2b are in contact with each other. The end portion 6a of the cylindrical member 6 facing the fixed core 3 is in contact with the annular step portion 2b from one axial direction.

[0027] The biasing member 7 is a member that biases the movable core 4 away from the fixed core 3. The biasing member 7 is, for example, an elastic body such as a spring. The biasing member 7 is mounted on the outer circumferential surface of the shaft 5. The biasing member 7 is positioned in the axial direction between the annular stopper portion 5a and the bottom wall 1c of the yoke 1.

[0028] The coil 8 generates a magnetic force that causes the movable core 4 to be attracted toward the fixed core 3 against the biasing force of the biasing member 7. The coil 8 is wound around the bobbin 2. The coil 8 is positioned radially between the peripheral wall 1d of the yoke 1 and the bobbin 2.

[0029] Figure 4 shows an example configuration of a control circuit 10 for driving an electromagnetic solenoid 100 according to Embodiment 1. As shown in Figure 4, the control circuit 10 includes a rectifier circuit 11, a coil 8, a switch 12, and a coil control circuit 13. The rectifier circuit 11 is connected to an AC power supply 14 and converts AC power to DC power. One end of the coil 8 is connected to the positive output side of the rectifier circuit 11. One end of the switch 12 is connected to the other end of the coil 8. The other end of the switch 12 is connected to the negative output side of the rectifier circuit 11. The coil control circuit 13 controls the switch 12 to be in an ON state or an OFF state. The switch 12 and the coil control circuit 13 constitute a drive circuit 9. The drive circuit 9 reduces the current flowing through the coil 8 when the movable iron core 4 is attracted to the fixed iron core 3 compared to when it is attracted.

[0030] Next, we will explain in more detail the configuration of the fixed core 3 and the movable core 4.

[0031] As shown in Figure 1, with the movable core 4 attached to the fixed core 3, a radial gap 15 is formed between the outer circumferential surface of the protrusion 4b of the movable core 4 and the inner circumferential surface of the recess 3b of the fixed core 3. The gap 15 includes a first gap 15a and a second gap 15b.

[0032] The first gap 15a is formed by being surrounded by a part of the second straight portion 4c of the convex portion 4b, the inner wall of the groove portion 4g, and the first tapered portion 3c of the concave portion 3b. With the movable core 4 in contact with the fixed core 3, the first gap 15a is formed between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b by the groove portion 4g, a part of the second straight portion 4c, and the first tapered portion 3c.

[0033] The second gap 15b is formed between the remaining portion of the second straight portion 4c and the second tapered portion 4d of the convex portion 4b and the first straight portion 3d of the concave portion 3b. When the movable core 4 is attracted to the fixed core 3, the second gap 15b is formed between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b. The second gap 15b is formed closer to the tip 4e of the convex portion 4b than the first gap 15a. The first gap 15a and the second gap 15b are in communication with each other and are connected in the axial direction.

[0034] Next, the operation of the electromagnetic solenoid 100 according to Embodiment 1 will be described.

[0035] Figure 5 is a cross-sectional view showing the state of the electromagnetic solenoid 100 according to Embodiment 1 when it is not energized. As shown in Figure 5, when the electromagnetic solenoid 100 is not energized, no magnetic force is generated in the coil 8. Therefore, the movable core 4 is pressed away from the fixed core 3 by the biasing force (elastic force) of the biasing member 7. In other words, the movable core 4 is not attracted to the fixed core 3. In this state, the fixed-side contact surface 3a and the movable-side contact surface 4a are separated from each other in the axial direction.

[0036] As shown in Figure 1, when the electromagnetic solenoid 100 is energized, that is, when current is passed through the coil 8 by the coil control circuit 13 (see Figure 4), a magnetic force is generated in the coil 8 that is proportional to the current flowing through it. As a result, the movable core 4 is attracted (drawn in) towards the fixed core 3 along the bobbin 2 and cylindrical member 6, against the biasing force of the biasing member 7. The movable core 4 then stops at the position where it contacts the fixed-side contact surface 3a of the fixed core 3, and the movable core 4 is attracted to the fixed core 3.

[0037] In other words, the movement of the movable core 4 due to the excitation action of the electromagnetic solenoid 100 is transmitted to the shaft 5, and the shaft 5 moves toward the bottom wall 1c of the yoke 1 against the biasing force of the biasing member 7. At this time, an attractive force is generated between the movable side contact surface 4a and the fixed side contact surface 3a, causing the movable core 4 to be attracted to the fixed core 3.

[0038] Here, the operation of the drive circuit 9 when the electromagnetic solenoid 100 is energized will be explained with reference to Figures 1, 4, 6, and 7. Figure 6 is an explanatory diagram of the operation of the drive circuit 9 in Embodiment 1, showing the relationship between the voltage across the coil 8 and time. Figure 7 is an explanatory diagram of the operation of the drive circuit 9 in Embodiment 1, showing the relationship between the current flowing through the coil 8 and time. The horizontal axis in both Figures 6 and 7 represents time. The vertical axis in Figure 6 represents voltage, and the vertical axis in Figure 7 represents current.

[0039] When power is turned on from a non-powered state, the coil control circuit 13 turns on the switch 12 at timing t1 shown in Figure 6, applying voltage to the coil 8. As a result, current flows through the coil 8 at timing t1 shown in Figure 7. At this time, as shown in Figure 1, the movable iron core 4 is attracted towards the fixed iron core 3 along the bobbin 2 and cylindrical member 6, against the biasing force of the biasing member 7.

[0040] At timing t2 shown in Figure 7, after the movable core 4 has been attracted to the fixed core 3 against the biasing force of the biasing member 7, the coil control circuit 13 starts a switching operation to turn the switch 12 on and off, as shown in Figure 6. As a result of the switching operation of the switch 12, as shown in Figure 7, the current flowing through the coil 8 is reduced to a value that can maintain the attraction of the movable core 4.

[0041] The switching operation of switch 12 is performed with the aim of reducing the heat generated by coil 8 and reducing the load and heat generated by drive circuit 9. Because the load on drive circuit 9 is reduced, it becomes possible to use low-load and small components in the drive circuit 9, thereby making the entire drive circuit 9 smaller.

[0042] Next, the effects of the electromagnetic solenoid 100 according to Embodiment 1 will be explained while comparing it with the conventional electromagnetic solenoid 200. Figure 8 is a cross-sectional view showing the flow of magnetic fluxes N1 and N2 during the attraction and holding of the conventional electromagnetic solenoid 200. Figure 9 is a cross-sectional view showing the flow of magnetic fluxes M1 and M2 during the attraction and holding of the electromagnetic solenoid 100 according to Embodiment 1. Figure 10 is a cross-sectional view showing the flow of magnetic flux N3 at the start of the attraction operation of the conventional electromagnetic solenoid 200. Figure 11 is a cross-sectional view showing the flow of magnetic flux M3 at the start of the attraction operation of the electromagnetic solenoid 100 according to Embodiment 1. Note that the start of the attraction operation refers to the point in time when current is supplied during the attraction operation.

[0043] First, with reference to Figure 8, the flow of magnetic flux N1 generated between the movable core 220 and the fixed core 210 during the attraction and holding of a conventional electromagnetic solenoid 200 will be explained. The convex portion 220b of the movable core 220 is formed in the shape of a frustoconical that gradually decreases in diameter as it approaches the fixed core 210. The concave portion 210b of the fixed core 210 is formed in the shape of a frustoconical into which the convex portion 220b fits. During attraction and holding, the outer circumferential surface of the convex portion 220b and the inner circumferential surface of the concave portion 210b are in contact with each other. In other words, during attraction and holding, there is no gap between the outer circumferential surface of the convex portion 220b and the inner circumferential surface of the concave portion 210b.

[0044] In the conventional electromagnetic solenoid 200, when attracting and holding, there is no gap between the outer surface of the convex portion 220b and the inner surface of the concave portion 210b. As a result, the magnetic resistance between the outer surface of the convex portion 220b and the inner surface of the concave portion 210b is low, and a large amount of magnetic flux N2 flows to the convex portion 220b of the movable core 220. This generates not only magnetic flux N1 in the same direction as the operating direction Y of the movable core 220, but also a large amount of magnetic flux N2 in a different direction from the operating direction Y of the movable core 220, causing a decrease in the attracting force between the movable side contact surface 220a and the fixed side contact surface 210a.

[0045] In contrast, in this embodiment, as shown in Figure 9, a groove 4g is formed on the end of the movable core 4 that faces the fixed core 3, extending around the entire circumference of the base portion 4f of the protrusion 4b. Furthermore, in this embodiment, when the movable core 4 is attracted to the fixed core 3, a first gap 15a is formed between the outer circumferential surface of the protrusion 4b and the inner circumferential surface of the recess 3b by the groove 4g, a part of the second straight portion 4c, and the first tapered portion 3c. With these configurations, the magnetic resistance between the outer circumferential surface of the protrusion 4b and the inner circumferential surface of the recess 3b increases when the movable core is attracted and held, thereby reducing the magnetic flux M2 flowing through the protrusion 4b of the movable core 4. This reduces the magnetic flux M2 in a direction different from the operating direction Y of the movable core 4. Therefore, the magnetic flux M1 in the same direction as the operating direction Y of the movable core 4, that is, the magnetic flux M1 passing through the movable contact surface 4a and the fixed contact surface 3a, can be increased, and the attractive force generated between the movable contact surface 4a and the fixed contact surface 3a can be increased. For this reason, even if the coil control circuit 13 (see Figure 4) performs a switching operation and reduces the current flowing through the coil 8, the magnetic flux M1 necessary for the attraction of the movable core 4 to the fixed core 3 can be secured.

[0046] Furthermore, in this embodiment, as shown in Figure 9, a second gap 15b is formed between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b, at a position closer to the tip 4e of the convex portion 4b than the first gap 15a. With this configuration, the magnetic resistance between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b is further increased during suction and holding, thereby further reducing the magnetic flux M2 flowing through the convex portion 4b of the movable core 4. This further reduces the magnetic flux M2 in a direction different from the operating direction Y of the movable core 4. Therefore, the magnetic flux M1 passing through the movable side contact surface 4a and the fixed side contact surface 3a can be further increased, and the suction force generated between the movable side contact surface 4a and the fixed side contact surface 3a can be further increased.

[0047] Next, with reference to Figures 10 and 11, the flow of magnetic flux N3 generated between the movable core 220 and the fixed core 210 of a conventional electromagnetic solenoid 200 at the start of the attraction operation, and the flow of magnetic flux M3 generated between the movable core 4 and the fixed core 3 of an electromagnetic solenoid 100 according to Embodiment 1 at the start of the attraction operation will be described.

[0048] At the start of the suction operation, the gap G1 formed between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b in Embodiment 1 and the gap G2 formed between the outer circumferential surface of the convex portion 220b and the inner circumferential surface of the concave portion 210b in the conventional example are approximately the same in size. Therefore, at the start of the suction operation, the magnetic resistance between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b in Embodiment 1 is approximately the same as the magnetic resistance between the outer circumferential surface of the convex portion 220b and the inner circumferential surface of the concave portion 210b in the conventional example.

[0049] In this embodiment, a first gap 15a and a second gap 15b are provided between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b during suction and holding, resulting in a smaller volume of the convex portion 4b compared to the convex portion 220b in the conventional example. However, in this embodiment, at the start of the suction operation, the magnetic resistance between the outer circumferential surface of the convex portion 4b and the inner circumferential surface of the concave portion 3b can be made approximately the same as the magnetic resistance between the outer circumferential surface of the convex portion 220b and the inner circumferential surface of the concave portion 210b in the conventional example, and the convex portion 4b can be given sufficient volume to allow the magnetic flux M3 at the start of the suction operation to flow. Therefore, the suction force of the electromagnetic solenoid 100 according to Embodiment 1 at the start of the suction operation can be made equivalent to the suction amount of the electromagnetic solenoid 200 in the conventional example.

[0050] Next, a modified example of Embodiment 1 will be described.

[0051] In this embodiment, as shown in Figure 1, the inner circumferential surface of the recess 3b is composed of a first tapered portion 3c and a first straight portion 3d, but it may also be composed of only the first straight portion 3d. That is, the first tapered portion 3c may be omitted, and the first straight portion 3d may be formed from one end of the fixed core 3 in the axial direction to the bottom surface 3e of the recess.

[0052] Embodiment 2. Next, with reference to Figures 12 to 15, an electromagnetic solenoid 100A according to Embodiment 2 will be described. In this embodiment, the configuration of the cylindrical member 6 differs from that of Embodiment 1 described above. In Embodiment 2, parts that overlap with those of Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted.

[0053] Figure 12 is a cross-sectional view showing the state of the electromagnetic solenoid 100A according to Embodiment 2 at the start of its attraction operation. Figure 13 is a perspective view showing the cylindrical member 6 in Embodiment 2. As shown in Figures 12 and 13, a cylindrical member side tapered portion 6b is formed on the outer circumferential surface of the end portion 6a of the cylindrical member 6 that faces the fixed core 3. The cylindrical member side tapered portion 6b decreases in diameter as it moves axially toward the annular step portion 2b and the fixed core 3. A third gap 16 is formed between the cylindrical member side tapered portion 6b and the annular step portion 2b. The third gap 16 is formed around the entire circumference in the circumferential direction between the cylindrical member side tapered portion 6b and the annular step portion 2b.

[0054] Next, the effects of the electromagnetic solenoid 100A according to Embodiment 2 will be explained while comparing it with the conventional electromagnetic solenoid 200. Figure 14 is a cross-sectional view showing the flow of magnetic fluxes N4 and N5 at the start of the attraction operation of the conventional electromagnetic solenoid 200. Figure 15 is a cross-sectional view showing the flow of magnetic flux M4 at the start of the attraction operation of the electromagnetic solenoid 100A according to Embodiment 2.

[0055] First, with reference to Figure 14, the flow of magnetic fluxes N4 and N5 generated at the start of the attraction operation between the cylindrical member 230 and the fixed iron core 210 of a conventional electromagnetic solenoid 200 will be explained. The inner and outer diameters of the cylindrical member 230 are constant along its entire axial length. The end portion 230a of the cylindrical member 230 facing the fixed iron core 210 and the annular stepped portion 240a are in contact with each other. In other words, there is no gap between the cylindrical member 230 and the annular stepped portion 240a.

[0056] In the conventional electromagnetic solenoid 200, the outer surface of the end 230a of the cylindrical member 230 facing the fixed core 210 does not have a tapered portion, and there is no gap between the cylindrical member 230 and the annular step portion 240a. As a result, magnetic flux N4 flows from the cylindrical member 230 through the bobbin 240 to the fixed core 210. This reduces the magnetic flux N5 flowing to the movable core 220, causing a decrease in the attractive force generated between the movable contact surface 220a and the fixed contact surface 210a.

[0057] In contrast, in this embodiment, as shown in Figure 15, a tapered portion 6b is formed on the outer circumferential surface of the end portion 6a of the cylindrical member 6 facing the fixed core 3, which decreases in diameter as it approaches the fixed core 3 along the axial direction. Furthermore, a third gap 16 is formed between the tapered portion 6b and the annular step portion 2b. These configurations increase the magnetic resistance between the cylindrical member 6 and the bobbin 2 in the axial direction, thereby increasing the magnetic resistance between the cylindrical member 6 and the fixed core 3 in the axial direction. In this embodiment, by making the area of ​​the portion where the cylindrical member 6 and the movable core 4 face each other in the radial direction the same as that of the conventional electromagnetic solenoid 200, the magnetic flux N4 that flowed from the cylindrical member 230 to the fixed core 210 in the conventional electromagnetic solenoid 200 can be changed to a magnetic flux M4 that flows from the cylindrical member 6 to the movable core 4. Therefore, at the start of the adsorption operation, the magnetic flux M4 flowing from the cylindrical member 6 to the movable iron core 4 can be increased, and the adsorption force generated between the movable side contact surface 4a and the fixed side contact surface 3a can be increased. For this reason, by providing the first gap 15a and the second gap 15b, even if the volume of the protrusion 4b is reduced, the adsorption force of the electromagnetic solenoid 100A at the start of the adsorption operation can be made equal to or greater than the adsorption force of the conventional electromagnetic solenoid 200. In other words, the decrease in the adsorption force at the start of the adsorption operation due to the reduction in the volume of the protrusion 4b can be suppressed.

[0058] Embodiment 3. Next, with reference to Figures 16 to 18, the electromagnetic solenoid 100B according to Embodiment 3 will be described. In this embodiment, the configuration of the cylindrical member 6 differs from that of Embodiments 1 and 2 described above. In Embodiment 3, parts that overlap with Embodiments 1 and 2 are denoted by the same reference numerals and their descriptions are omitted.

[0059] Figure 16 is a cross-sectional view showing the state of the electromagnetic solenoid 100B according to Embodiment 3 at the start of its attraction operation. As shown in Figure 16, a magnetoresistive portion 17 is formed between the end 6a of the cylindrical member 6 facing the fixed iron core 3 and the annular step portion 2b, which obstructs the flow of magnetic flux M5 (see Figure 17) from the cylindrical member 6 to the annular step portion 2b. In this embodiment, the magnetoresistive portion 17 is a gap. Hereinafter, this gap will be referred to as the third gap 16.

[0060] In this embodiment, by making the axial dimension L1 of the cylindrical member 6 shorter than the axial dimension L2 from the lid portion 1b to the annular step portion 2b, a third gap 16 is formed between the end portion 6a of the cylindrical member 6 facing the fixed core 3 and the annular step portion 2b. By adjusting the axial dimension L1 of the cylindrical member 6, the axial dimension L3 of the third gap 16 can be adjusted, thereby adjusting the magnetic resistance between the cylindrical member 6 and the fixed core 3 in the axial direction. The magnetic resistance portion 17 may be a non-magnetic material formed from a non-magnetic material such as a resin material. That is, a non-magnetic material may be placed between the end portion 6a of the cylindrical member 6 facing the fixed core 3 and the annular step portion 2b instead of the third gap 16.

[0061] Next, the effects of the electromagnetic solenoid 100B according to Embodiment 3 will be described.

[0062] In this embodiment, as shown in Figure 16, a third gap 16, which is a magnetic resistance portion 17 that obstructs the flow of magnetic flux M5 (see Figure 17) from the cylindrical member 6 to the annular step portion 2b, is formed between the end portion 6a of the cylindrical member 6 facing the fixed core 3 and the annular step portion 2b. This configuration increases the magnetic resistance between the cylindrical member 6 and the bobbin 2 in the axial direction, thereby increasing the magnetic resistance between the cylindrical member 6 and the fixed core 3 in the axial direction. Furthermore, in this embodiment, by making the area of ​​the portion where the cylindrical member 6 and the movable core 4 face each other in the radial direction the same as that of the conventional electromagnetic solenoid 200 (see Figure 14), the magnetic flux N4 that flowed from the cylindrical member 230 to the fixed core 210 in the conventional electromagnetic solenoid 200 can be changed to a magnetic flux M4 (see Figure 18) that flows from the cylindrical member 6 to the movable core 4. Therefore, at the start of the adsorption operation, the magnetic flux M4 flowing from the cylindrical member 6 to the movable iron core 4 can be increased, and the adsorption force generated between the movable side contact surface 4a and the fixed side contact surface 3a can be increased. For this reason, by providing the first gap 15a and the second gap 15b, even if the volume of the protrusion 4b is reduced, the adsorption force of the electromagnetic solenoid 100B at the start of the adsorption operation can be made equal to or greater than the adsorption force of the conventional electromagnetic solenoid 200. In other words, the decrease in the adsorption force at the start of the adsorption operation due to the reduction in the volume of the protrusion 4b can be suppressed.

[0063] In particular, in this embodiment, the axial dimension L3 of the third gap 16 can be adjusted by adjusting the axial dimension L1 of the cylindrical member 6, so the magnetic resistance between the cylindrical member 6 and the fixed core 3 in the axial direction can be easily adjusted. The larger the axial dimension L3 of the third gap 16, the higher the magnetic resistance between the cylindrical member 6 and the fixed core 3 in the axial direction, so the magnetic flux M4 (see Figure 18) flowing from the cylindrical member 6 to the movable core 4 at the start of the attraction operation can be increased.

[0064] Figure 17 is a cross-sectional view showing the flow of magnetic fluxes M4 and M5 at the start of the attraction operation of the electromagnetic solenoid 100B according to Embodiment 3, and shows the case when the third gap 16 is small. Figure 18 is a cross-sectional view showing the flow of magnetic fluxes M4 and M5 at the start of the attraction operation of the electromagnetic solenoid 100B according to Embodiment 3, and shows the case when the third gap 16 is large. For example, as shown in Figure 17, when the axial dimension L3 of the third gap 16 is small, the magnetic flux M5 that flows from the cylindrical member 6 to the fixed iron core 3 can be changed to magnetic flux M4 that flows from the cylindrical member 6 to the movable iron core 4 by increasing the axial dimension L3 of the third gap 16, as shown in Figure 18.

[0065] The effect of the third gap 16 (magnetic resistance portion 17) is to increase the magnetic resistance between the cylindrical member 6 and the fixed iron core 3 in the axial direction, thereby increasing the magnetic flux M4 flowing from the cylindrical member 6 to the movable iron core 4 at the start of the attraction operation. This effect is achieved not by the size of the third gap 16, but by the presence of the third gap 16 between the cylindrical member 6 and the annular step portion 2b in the axial direction. In other words, although the effect of the third gap 16 differs depending on its size, it has considerable technical significance compared to the conventional electromagnetic solenoid 200 (see Figure 14) which does not have a third gap 16.

[0066] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0067] 1 Yoke, 1a Base, 1b Cover, 1c Bottom wall, 1d Peripheral wall, 1e, 1f Through hole, 2,240 Bobbin, 2a Flange, 2b, 240a Annular step, 3,210 Fixed core, 3a, 210a Fixed side contact surface, 3b, 210b Recess, 3c First tapered section, 3d First straight section, 3e Bottom surface of recess, 3f Through hole, 4,220 Movable core, 4a, 220a Movable side contact surface, 4b, 220b Protrusion, 4c Second straight section, 4d Second tapered section, 4e Tip, 4f Root section, 4g Groove, 4h First section, 4i Second section, 4j Mounting hole, 5 Shaft, 5a Annular stopper section, 6,230 Cylindrical member, 6a, 230a End portion, 6b Tapered portion on the cylindrical member side, 7 Biasing member, 8 Coil, 9 Drive circuit, 10 Control circuit, 11 Rectifier circuit, 12 Switch, 13 Coil control circuit, 14 AC power supply, 15 Gap, 15a First gap, 15b Second gap, 16 Third gap, 17 Magnetic resistance section, 100, 100A, 100B, 200 Electromagnetic solenoid, C Central axis, G1, G2 Gap.

Claims

1. A cylindrical bobbin made of a non-magnetic material, A fixed iron core positioned on the inner circumference of the bobbin, A movable core is arranged on the inner circumference of the bobbin so as to be movable in the axial direction and facing the fixed core in the axial direction, A biasing member that biases the movable core away from the fixed core, A coil that generates a magnetic force that causes the movable core to be attracted toward the fixed core against the biasing force of the biasing member, A drive circuit that reduces the current flowing through the coil compared to the current during the attraction operation when the movable iron core is attracted to the fixed iron core, The bobbin, the fixed core, the movable core, the biasing member, and the coil are housed in a yoke made of a magnetic material, Equipped with, The end of the movable core facing the fixed core has a protrusion that projects toward the fixed core and a groove that extends around the entire circumference of the base of the protrusion. The fixed core has a recess formed at the end of the fixed core that faces the movable core, An electromagnetic solenoid characterized in that, with the movable core attached to the fixed core, the protrusion is positioned within the recess, and a first gap is formed between the outer circumferential surface of the protrusion and the inner circumferential surface of the recess by the groove.

2. The electromagnetic solenoid according to claim 1, characterized in that a second gap is formed between the outer circumferential surface of the protrusion and the inner circumferential surface of the recess, at a position closer to the tip of the protrusion than the first gap.

3. The yoke further comprises a cylindrical member positioned between the bobbin and the movable core and fixed to the inner circumferential surface of the bobbin, The inner surface of the bobbin has an annular step portion that protrudes toward the inner circumference. The outer circumferential surface of the end of the cylindrical member facing the fixed iron core has a cylindrical member side tapered portion that decreases in diameter as it approaches the fixed iron core along the axial direction. The electromagnetic solenoid according to claim 1 or 2, characterized in that a third gap is formed between the tapered portion on the cylindrical member side and the annular stepped portion.

4. The yoke further comprises a cylindrical member positioned between the bobbin and the movable core and fixed to the inner circumferential surface of the bobbin, The inner surface of the bobbin has an annular step portion that protrudes toward the inner circumference. The electromagnetic solenoid according to claim 1 or 2, characterized in that a magnetoresistive portion is formed between the end of the cylindrical member facing the fixed iron core and the annular step portion, which obstructs the flow of magnetic flux from the cylindrical member toward the annular step portion.

5. The electromagnetic solenoid according to claim 4, characterized in that the magnetic resistance portion is a gap formed between the end of the cylindrical member facing the fixed iron core and the annular step portion, or a non-magnetic material disposed between the end of the cylindrical member facing the fixed iron core and the annular step portion and formed from a non-magnetic material.

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