Patent Application
20150145505
This application is based on reference Japanese Patent Application No. 2013-241677 filed on Nov. 22, 2013, the disclosure of which is incorporated herein by reference.
The present disclosure relates to a detection device configured to detect movement of a detected object.
Conventionally, a known detection device may be configured to detect movement of a detected object, which is formed of a nonmagnetic material or a magnetic material, while being noncontact with the detected object.
Patent Document 1 discloses a detection device to detect revolution of a gear, which is a detected object formed of a magnetic material. Specifically, the detection device exerts a magnetic field on a gear through a core, which is equipped to a magnet on a gear side. In the present state, an amount of magnetic flux flowing through the core, when a projected portion of a gear faces the core, is greater than an amount of magnetic flux flowing through the core, when a recessed portion of the gear faces the core. A coil is wound around the outer circumferential periphery of the core. The coil generates an induced electromotive force according to change in the magnetic flux generated by the core. The detection device detects the induced electromotive force thereby to detect the revolution of the gear. In the detection device, the core has a thin end facing the gear. The thin end is to converge the magnetic flux generated by the magnet onto the projected portion of the gear. The thin end is to enable the detection device to detect the revolution of the gear with high accuracy.
(Patent Document 1)
Publication of unexamined patent application No. H8-160059
In a case where a detected object is formed of a nonmagnetic material, a detection device may detect movement of a detected object in a subsequent way. Specifically, the detection device may exert a magnetic field on the detected object through a core, which is equipped to a magnet on a detected object side. The detected object may cause an electromotive force, which generates a magnetic field in a direction to cancel change in the magnetic field, which passes through the detected object. Thus, the detected object may cause an eddy current. The eddy current may cause a magnetic field, which causes change in a magnetic flux flowing through the core. The change in the magnetic flux may cause an induced electromotive in the coil. The detection device may detect the change in the magnetic flux thereby to detect movement of the detected object. The detection device may employ the thin end in the core on the detected object side, as disclosed in Patent Document 1. In this case, in a case where the detected object is formed of a nonmagnetic material, the thin end may reduce the influence exerted on the core and caused by the magnetic field, which is generated by the eddy current in the detected object. Consequently, it may be concerned about reduction in the induced electromotive force, which is generated in the coil.
It is an object of the present disclosure to produce a detection device configured to detect movement of a detected object with high accuracy and/or with high gain.
According to an aspect of the present disclosure, a detection device is configured to detect a movement of a detected object, which is formed of a nonmagnetic and conductive material. The detection device comprises a magnet configured to generate a magnetic field around a position where the detected object passes. The detection device further comprises a first core being a magnetic object and equipped to a detected object side of the magnet. The detection device further comprises a coil wound around a radially outside of the first core. The detection device further comprises a second core being a magnetic object and connected to a detected object side of the first core. The second core is greater than an outer diameter of the first core.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
As follows, embodiments according to the disclosure will be described with reference to drawings.
A first embodiment of the present disclosure will be described with reference to
The detection device 1 includes a magnet 10, a first core 11, a second core 12, a coil 13, a case 14, and/or the like. The magnet 10 is magnetized to form an S pole on the side of the blade 2. The magnet 10 is further magnetized to form an N pole on the opposite side of the blade 2. The magnet 10 may be magnetized to form the N pole and the S pole in an opposite form. The magnet 10 forms a static magnetic field at a position, where the blade 2 passes, through the first core 11 and the second core 12.
The first core 11 and the second core 12 are integrally formed of, for example a magnetic material, such as a ferrous material. That is, the first core 11 and the second core 12 are each being a magnetic object. The magnet 10 is located on the opposite side of the first core 11 and the second core 12 from the blade 2. The first core 11 is in a column shape. The first core 11 is connected to the magnet 10 at one end in the axial direction. The first core 11 is further connected to the second core 12 at the other end in the axial direction. The second core 12 is in a disc shape. The first core 11 is located on the opposite side of the second core 12 from the blade 2. The outer diameter of the second core 12 is greater than the outer diameter of the first core 11.
A bobbin 15 is located on the radially outside of the first core 11. The bobbin 15 is formed of an insulative material, such as resin. The coil 13 is wound around the bobbin 15. Two wirings 16 and 17 are taken out of both ends of the coil 13. The wirings 16 and 17 are electrically connected with two wire cables 18 and 19, respectively. The two wire cables 18 and 19 are electrically connected with two terminals (not shown) equipped to a connector 20. The case 14 is formed of a nonmagnetic material such as a metallic material, a resin material, and/or the like. The case 14 accommodates the magnet 10, the first core 11, the second core 12, the coil 13, and/or the like.
Subsequently, a configuration of the detection device 1 to detect the revolution of the blade 2 will be described. In
When comparing ranges of the magnetic fields, which are represented by the strengths c and d of the magnetic flux density at the position represented by the solid line T, the range of the detection device 1 according to the present embodiment is wider than the range of the detection device 3 according to the comparative example. In addition, an area of the second core 12 according to the present embodiment, which is opposed to the blade 2, is wider than an area of the core 4 according to the comparative example, which is opposed to the blade 2. That is, the second core 12 according to the present embodiment is opposed to the blade 2 at a wider area than the core 4 according to the comparative example. Therefore, the core 4 according to the comparative example is apt to be exerted with the magnetic field caused by the eddy current generated in the blade 2, compared with the second core 12 according to the present embodiment. Consequently, change in the magnetic flux generated by the first core 11 according to the present embodiment is greater than change in the magnetic flux generated by the core 4 according o the comparative example.
The detection device 1 according to the present embodiment may produce operation effects as follows.
(1) The detection device 1 according to the present embodiment includes the second core 12. The second core 12 is on the blade side of the first core 11, around which the coil 13 is wound. That is, the second core 12 is on the side of the first core 11, which is directed to the blade 2. The outer diameter of the second core 12 is greater than the outer diameter of the first core 11. According to the present configuration, the second core 12 may enable to enlarge the range of the magnetic field B1, which is caused by the magnet 10 and applied on the blade 2. Furthermore, the magnetic field B2, which is caused by the eddy current I generated in the blade 2, may enable the second core 12 to exert a large influence on the first core 11. Therefore, the present configuration may enable to enlarge change in the magnetic flux generated in the first core 11. Consequently, the present configuration may enable to enlarge the induced electromotive force, which is generated in the coil 13. Thus, the detection device 1 is enabled to enhance accuracy of detection of the revolution of the blade 2.
(2) According to the present embodiment, the first core 11 and the second core 12 are integrally formed. The present configuration may enable to reduce a magnetic resistance between the first core 11 and the second core 12. Therefore, the present configuration may enable to enlarge change in the magnetic flux, which is generated by the second core 12 and the first core 11 due to influence of the magnetic field B2, which is caused by the eddy current I in the blade 2.
The above-described embodiment has exemplified the detection device configured to detect the revolution of the blade. According to another embodiment, the detection device may be configured to detect movement of various detected objects formed of a nonmagnetic and conductive material.
According to the present disclosure, the detection device is configured to detect movement of the detected object, which is formed of a nonmagnetic and conductive material. The detection device includes the first core and the second core. The first core is located on the detected object side of the magnet. That is, the first core is located on the side of the magnet, the side of the magnet being closer to the detected object. The first core is wound with the coil. The second core is connected with the detected object side of the first core. That is, the second core is connected to the side of the first core, the side of the first core being closer to the detected object. The outer diameter of the second core is greater than the outer diameter of the first core.
The present configuration may enable the second core to enlarge the range of the magnetic field, which is generated by the magnet and exerted on the detected object. Furthermore, the magnetic field, which is caused by the eddy current generated in the detected object, may enable the second core to exert a large influence on the first core. Therefore, the present configuration may enable to enlarge change in the magnetic flux generated in the first core. Consequently, the present configuration enables to enlarge the induced electromotive force, which is generated in the coil. Thus, the detection device is enabled to enhance accuracy of detection of movement of the detected object.
It should be appreciated that while the processes of the embodiments of the present disclosure have been described herein as including a specific sequence of steps, further alternative embodiments including various other sequences of these steps and/or additional steps not disclosed herein are intended to be within the steps of the present disclosure.
While the present disclosure has been described with reference to preferred embodiments thereof, it is to be understood that the disclosure is not limited to the preferred embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-241677 | Nov 2013 | JP | national |
