Solenoid

Abstract

To provide a solenoid in a low cost, in which a foreign material is not sucked into an internal part of a housing, and a holing power is not deteriorated even it is used at a high temperature environment.SOLUTION: A solenoid 100 comprises: a shaft 102 that is projected from a housing 104; a coil 110; a movable iron core 112; an inclination surface 114 that is formed to an inner peripheral surface 116 of the movable iron core, and is inclined so as to be separated from the shaft as directed to a shaft projection direction; a rotational body 118 that is arranged to between the shaft and the inclination surface; a holding device 120 that is fixed to the housing and holds the rotational body; a first spring 122 that energizes the movable iron core to the shaft projection direction; and a second spring 124 that energizes the shaft to the shaft projection direction. An energization force F1 of the first spring is transmitted to the shaft via the rotational body with a wedge formed by the rotational body and the inclination surface when the coil is in a non-excitation, and the movable iron core is sucked by a suction force F3 that is larger than the excitation force of the first spring when the coil is excited to move them to a direction opposite to the shaft projection direction, and thus, an engagement of the wedge is cancelled.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a solenoid that holds a shaft.

Background Art

[0002] As an example, a solenoid includes a shaft protruding from a housing, a movable iron core, a permanent magnet, and a coil. The movable iron core is disposed inside the coil and the shaft is inserted therethrough. The coil attracts the movable iron core when excited.

[0003] Patent Document 1 describes a solenoid in which a permanent magnet and a coil are both built in a cylindrical case (housing), and a movable iron core is biased by a spring in the direction in which the shaft protrudes.

[0004] In this solenoid, when the coil is non-energized (non-excited), the shaft is held in a protruding state by the biasing force of the spring and the magnetic flux of the permanent magnet. On the other hand, when the coil is energized (excited), the magnetic path of the permanent magnet is switched by the magnetic flux of the coil, and the magnetic flux of the permanent magnet passing through the movable iron core decreases, thereby reducing the holding force of the shaft. Then, the movable iron core is attracted by the magnetic flux of the coil to pull in the solenoid.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since the solenoid of Patent Document 1 uses a permanent magnet, foreign matter (iron powder) may be sucked into the interior of the housing, which may cause the function of the solenoid to deteriorate. In addition, since the permanent magnet demagnetizes at high temperatures, when the solenoid is used in a high-temperature environment, the holding force of the shaft may decrease. Furthermore, using a permanent magnet increases the cost.

[0007] In view of such problems, an object of the present invention is to provide an inexpensive solenoid in which foreign matter is not sucked into the interior of the housing and the holding force does not decrease even when used in a high-temperature environment.

Means for Solving the Problems

[0008] To solve the above problems, a typical configuration of the solenoid according to the present invention is a solenoid that holds a shaft, comprising a housing made of a magnetic material, a shaft protruding from the housing, a coil housed in the housing, a movable iron core disposed inside the coil and through which the shaft passes, an inclined surface formed on the inner peripheral surface of the movable iron core and inclined so as to be away from the shaft in the direction of shaft protrusion, a rolling element disposed between the shaft and the inclined surface, a retainer fixed to the housing and rotatably holding the rolling element, a first spring that biases the movable iron core in the direction of shaft protrusion, and a second spring that biases the shaft in the direction of shaft protrusion. When the coil is non-excited, the biasing force of the first spring is transmitted to the shaft via the rolling element by the wedge formed by the rolling element and the inclined surface. When the coil is excited, the movable iron core is attracted by an attractive force greater than the biasing force of the first spring and moved in the direction opposite to the direction of shaft protrusion, thereby releasing the engagement of the wedge.

[0009] In the above configuration, the shaft is biased in the direction of shaft protrusion by the biasing force of the second spring. Also, when the coil is non-excited, the biasing force of the first spring is transmitted to the shaft via the rolling element by the wedge formed by the rolling element and the inclined surface. Therefore, the shaft is biased and held in the direction of shaft protrusion by the resultant force of the biasing force of the first spring and the biasing force of the second spring when the coil is non-excited.

[0010] Also, the attractive force that attracts the movable iron core when the coil is excited is greater than the biasing force of the first spring. As a result, when the coil is excited, the movable iron core is attracted and moved by the attractive force against the biasing force of the first spring, thereby releasing the engagement of the wedge. For this reason, when the coil is excited, the biasing force of the first spring is not transmitted to the shaft, and the shaft is biased only by the biasing force of the second spring in the shaft protruding direction and is held with a smaller holding force than when the coil is not excited.

[0011] As described above, with the above configuration, it is possible to switch the magnitude of the holding force without using a permanent magnet. In addition, since a permanent magnet that demagnetizes when used in a high-temperature environment is not used, the holding force does not decrease even when used in a high-temperature environment. Further, by not using a permanent magnet, foreign matter is not sucked into the housing, and the solenoid can be made inexpensive.

[0012] In the above configuration, if the attractive force by the coil is greater than the biasing force of the first spring, the magnitude of the holding force of the shaft can be switched. For this reason, the magnitude relationship between the biasing force F1 of the first spring 122 and the biasing force F2 of the second spring 124 is not particularly limited.

Effects of the Invention

[0013] According to the present invention, it is possible to provide an inexpensive solenoid in which foreign matter is not sucked into the housing and the holding force does not decrease even when used in a high-temperature environment.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0015] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. The dimensions, materials, and other specific numerical values shown in such embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to omit redundant description, and elements not directly related to the present invention are not shown.

[0016] FIG. 1 is an overall configuration diagram of a solenoid 100 in an embodiment of the present invention. Note that FIG. 1 shows the state of the solenoid 100 when it is not energized. The solenoid 100 is an actuator that holds a shaft 102 and switches the holding force of the shaft 102 without using a permanent magnet.

[0017] The shaft 102 protrudes from a housing 104 made of a magnetic material, and one end portion 102a thereof is pressed against a predetermined object (not shown). The shaft 102 is supported via a bearing 108 by a cylindrical sleeve 106 which is a member separate from the housing 104 as shown in the figure. Hereinafter, the direction in which the shaft 102 protrudes from the housing 104 (upward in the figure) is referred to as the "shaft protruding direction".

[0018] The solenoid 100 includes a cylindrical coil 110 housed in the housing 104 and a movable iron core 112. The movable iron core 112 is disposed inside the coil 110 and the shaft 102 is inserted therethrough. The movable iron core 112 has an inclined surface 114. The inclined surface 114 is a tapered portion formed on the inner peripheral surface 116 of the movable iron core 112, faces the shaft 102, and is inclined so as to be farther from the shaft 102 as it goes in the shaft protruding direction. Note that the inner peripheral surface 116 of the movable iron core 112 may be subjected to a hardening treatment using high-frequency quenching or nitriding treatment.

[0019] The solenoid 100 also includes rolling elements (balls or rollers) 118, a cage 120, a first spring 122, and a second spring 124. The rolling elements 118 are disposed between the shaft 102 and the inclined surface 114 of the movable iron core 112, and are rotatably held by the cage 120.

[0020] The cage 120 is a non-magnetic material such as a stainless steel member having a flange 126 and a boss 128, and holds the rolling elements 118 in a plurality of holes 130 provided in the boss 128. Also, the flange 126 of the cage 120 and the flange 106a of the sleeve 106 are caulked and fixed at the end 104a of the housing 104. In this way, the cage 120 is fixed to the housing 104. Here, as an example, the cage 120 is sandwiched and fixed between the housing 104 and the sleeve 106. Further, a gap 132 is provided between the flange 126 and the movable iron core 112.

[0021] The movable iron core 112 also has a boss 134 and a stepped portion 136. One end 122a of the first spring 122 abuts against the stepped portion 136 of the movable iron core 112. The other end 122b of the first spring 122 abuts against the end face 140 of the fixed core (fixed iron core) 138. In this way, the first spring 122 biases the movable iron core 122 in the shaft protruding direction with, for example, a biasing force F1. The fixed iron core 138 is continuous with the housing 104 as shown in the figure and the shaft 102 is inserted therethrough.

[0022] Furthermore, in the movable iron core 112 shown in FIG. 1, the boss end face portion 134a of the boss 134 faces the attracting portion 142 of the fixed iron core 138. The attracting portion 142 of the fixed iron core 138 is located inside the first spring 122 and is a cylindrical portion protruding in the shaft protruding direction.

[0023] Inside the shaft 102, there is a bottomed hole 144 extending in the axial direction. One end 124a of the second spring 124 abuts against the bottom 146 of the hole 144 of the shaft 102, and the other end 124b abuts against the end face 148 of the fixed iron core 138. In this way, the second spring 124 biases the shaft 102 in the shaft protruding direction with a biasing force F2. The biasing force F2 of the second spring 124 is set smaller than the biasing force F1 of the first spring 122.

[0024] Hereinafter, the states of the solenoid 100 when non-energized (non-excited) and when energized (excited) will be described. When the coil 110 of the solenoid 100 is non-excited, as shown in FIG. 1, the inclined surface 114 of the movable iron core 112 biased in the shaft protruding direction by the first spring 122 abuts against the rolling element 118. For this reason, the rolling element 118 is sandwiched between the shaft 102 and the inclined surface 114 and functions as a wedge.

[0025] Therefore, when the coil 110 of the solenoid 100 is non-excited, the biasing force F1 of the first spring 122 is transmitted to the shaft 102 via the rolling element 118 by the wedge composed of the rolling element 118 and the inclined surface 114 as shown by the arrow A. Further, the shaft 102 is biased in the shaft protruding direction by the biasing force F2 of the second spring 124.

[0026] For this reason, the shaft 102 is biased and held in the shaft protruding direction by the resultant force (F1 + F2) of the biasing force F1 of the first spring 122 and the biasing force F2 of the second spring 124 when the coil 110 is non-excited.

[0027] FIG. 2 is a diagram for explaining the state of the solenoid 100 in FIG. 1 when energized. When the coil 110 is energized, an attractive force F3 for attracting the movable iron core 112 is generated. The attractive force F3 by the coil 110 is larger than the biasing force F1 of the first spring 122 (F3 - F1 > 0).

[0028] Therefore, when the coil 110 of the solenoid 100 is excited, the movable iron core 112 is attracted by the attracting force F3 against the biasing force F1 of the first spring 122 and moves in the direction opposite to the shaft protruding direction. On the other hand, since the cage 120 is sandwiched and fixed between the housing 104 and the sleeve 106, the rolling elements 118 held by the cage 120 do not move in the direction opposite to the shaft protruding direction.

[0029] Furthermore, when the movable iron core 112 is attracted by the attracting force F3, it moves until the boss end face portion 134a of the boss 134 abuts against the attracting portion 142 of the fixed iron core 138. For this reason, as shown in FIG. 2, the gap 132 between the flange 126 of the cage 120 and the movable iron core 112 also becomes larger than the state shown in FIG. 1.

[0030] In this way, in the solenoid 100, when the movable iron core 112 moves in the direction opposite to the shaft protruding direction, the inclined surface 114 of the movable iron core 112 separates from the rolling element 118, and the engagement of the wedge composed of the rolling element 118 and the inclined surface 114 is released.

[0031] For this reason, when the coil 110 is excited, the biasing force F1 of the first spring 122 is not transmitted to the shaft 102, and the shaft 102 is biased in the shaft protruding direction only by the biasing force F2 of the second spring 124. As a result, the solenoid 100 is held with a smaller holding force, that is, the biasing force F2, as compared with when the coil 110 is not excited. Thereby, for example, the smaller the biasing force F2 of the second spring 124 is, the smaller the holding force of the shaft 102 when the coil 110 is excited can be made.

[0032] Therefore, according to the solenoid 100, the holding force of the shaft 102 can be switched without using a permanent magnet. Also, since a permanent magnet that would demagnetize when used in a high-temperature environment is not used, the holding force does not decrease even when used in a high-temperature environment. Further, by not using a permanent magnet, foreign matter is not sucked into the housing 104, and furthermore, the solenoid 100 can be made inexpensive. Note that the solenoid 100 switches between a high holding force and a low holding force and does not actively pull in the shaft 102.

[0033] In the above solenoid 100, if the attractive force F3 by the coil 110 is greater than the biasing force F1 of the first spring 122, the magnitude of the holding force of the shaft 102 can be switched. On the other hand, the magnitude relationship between the biasing force F1 of the first spring 122 and the biasing force F2 of the second spring 124 is not particularly limited, and the biasing force F1 of the first spring 122 may be smaller than the biasing force F2 of the second spring 124, or they may be of the same magnitude.

[0034] As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings. Needless to say, the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

Industrial Applicability

[0035] The present invention can be used as a solenoid for holding a shaft.

Explanation of Reference Numerals

[0036] 100…Solenoid, 102…Shaft, 102a…One end of the shaft, 104…Housing, 104a…End of the housing, 106…Sleeve, 106a…Flange of the sleeve, 108…Bearing, 110…Coil, 112…Movable iron core, 114…Inclined surface, 116…Inner peripheral surface of the movable iron core, 118…Rolling element, 120…Cage, 122…First spring, 122a…One end of the first spring, 122b…The other end of the first spring, 124…Second spring, 124a…One end of the second spring, 124b…The other end of the second spring, 126…Flange of the cage, 128…Boss of the cage, 130…Hole in the cage, 132…Clearance, 134…Boss of the movable iron core, 134a…Boss end face of the boss, 136…Step portion of the movable iron core, 138…Fixed iron core, 140, 148…End faces of the fixed iron core, 142…Suction portion of the fixed iron core, 144…Hole in the shaft, 146…Bottom of the hole in the shaft

Claims

【Claim 1】 A solenoid that holds a shaft, comprising: a housing made of a magnetic material; the shaft protruding from the housing; a coil housed in the housing; a movable iron core disposed inside the coil and through which the shaft is inserted; an inclined surface formed on the inner peripheral surface of the movable iron core and inclined so as to be away from the shaft in the direction of shaft protrusion; a rolling element disposed between the shaft and the inclined surface; a cage fixed to the housing and rotatably holding the rolling element; a first spring that biases the movable iron core in the shaft protrusion direction; a second spring that biases the shaft in the shaft protrusion direction, when the coil is not energized, the biasing force of the first spring is transmitted to the shaft via the rolling element by the wedge formed by the rolling element and the inclined surface, when the coil is energized, the movable iron core is attracted by an attractive force greater than the biasing force of the first spring and moved in the direction opposite to the shaft protrusion direction, thereby releasing the engagement of the wedge. A solenoid characterized by this.

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