JP2015059835A - Magnetic device having contact detection part and contact detection method for magnetic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wear and breakage due to contact between a movable part and a stationary part in a magnetic device having the movable part and the stationary part disposed in a non-contact state and using magnetic interaction.SOLUTION: A metal ring 20 which is a conductive member and is attached to a bobbin 14 which is an insulator is provided on a detection head 4 serving as a stationary part. Voltage is applied between a rod 6 to be detected serving as a movable part and the metal ring 20, and based on current flowing between the rod 6 to be detected and the metal ring 20, contact between the rod 6 to be detected and the metal ring 20 is detected by a contact detection circuit 12.

Description

  The present invention relates to contact detection between a movable part and a fixed part in a magnetic device.

  Patent Document 1 (Patent 4047947) discloses magnetically detecting the position of a rod that moves forward and backward in a bobbin of a detection head. The rod is provided with a magnetic mark made of a magnetic material, and the bobbin is provided with an excitation coil and a detection coil. When a current is passed through the exciting coil, an induced current is generated in the detection coil, and the phase of the induced current changes depending on the positional relationship between the rod and the bobbin. Thus, by obtaining this phase, the relative position between the bobbin and the rod can be detected.

  It is also known to use a permanent magnet instead of a magnetic material as a magnetic mark, and it is also known to use an exciting coil as a detection coil, and to use another magnetic element such as a Hall element instead of the coil. Yes. Furthermore, not only the combination of a rod and a bobbin, it is also known that a magnetic mark is arranged in a flat plate shape, and a coil or a hall element is arranged on a flat plate base.

Patent 4047947

  The detection head and the detection target member such as the rod should be non-contact in nature, but the detection target member may come into contact with the detection head due to the attachment state of these members, thermal deformation, change with time, or the like. Then, the member to be detected or the detection head is worn, and the detection performance is affected. In extreme cases, failure may occur.

  Although the magnetic position detecting device has been described here, the same applies to a linear actuator. The linear actuator includes a permanent magnet and a drive coil, one of which is a fixed part and the other is a movable part, and both are kept in non-contact. Here, when the movable portion and the fixed portion come into contact with each other, wear occurs and affects the operation accuracy of the actuator, and in an extreme case, a failure occurs.

  An object of the present invention is to detect contact between a movable part and a fixed part in a magnetic device.

The present invention is a magnetic device comprising a movable part and a fixed part, and using a magnetic interaction between the movable part and the fixed part,
The movable part and the fixed part are arranged in a non-contact manner,
A contact detection unit that detects contact between the movable unit and the fixed unit is provided.

Further, the present invention provides a magnetic device that includes a movable part and a fixed part, uses a magnetic interaction between the movable part and the fixed part, and the movable part and the fixed part are arranged in a non-contact manner.
In the contact detection method for a magnetic device, the contact detection unit detects contact between the movable part and the fixed part.

  The movable part and the fixed part are not only a combination of a round bar-like member and a cylindrical member as in the embodiment, but also two opposing plate-like members, or a square bar-like member and a square-cylindrical member. Combinations may be used. The contact detection unit may be one that detects electrical contact as in the embodiment, or may be one that detects the capacitance between the movable unit and the fixed unit using a capacitive proximity sensor. However, this will increase the size of the contact detection unit. In the present invention, since the contact between the movable part and the fixed part can be detected, there is no wear, deterioration in accuracy, failure, etc. due to the contact between both. In this specification, the description related to the magnetic device also applies to the contact detection method for the magnetic device as it is.

Magnetic devices are position sensors, linear actuators, etc.
When the head is a detection head that detects the relative position with the rod-shaped member, it becomes a position sensor,
-If the head is provided with a drive coil that moves relative to the rod-shaped member, a linear actuator is obtained.

Preferably, one of the movable part and the fixed part is a head composed of a magnetic element disposed on a nonmagnetic insulator,
The other of the movable part and the fixed part is a rod-shaped member composed of a row of permanent magnets or a row of magnetic and non-magnetic materials,
The contact detector is
A conductive member attached to the insulator;
A contact detection circuit that applies a voltage between the conductive member and the rod-shaped member, and detects contact between the head and the rod-shaped member from a current flowing between the conductive member and the rod-shaped member;
And
The conductive member is electrically insulated from other than the contact detection circuit,
In addition, the clearance between the conductive member and the rod-shaped member is set to the minimum clearance between the head and the rod-shaped member.

  If it does in this way, a contact can be easily detected by the presence or absence of the electric current which flows between an electroconductive member and a rod-shaped member. In addition, since the conductive member is attached to an insulator and is electrically insulated from the parts other than the contact detection circuit, current does not flow through the detection circuit unless the conductive member and the rod-shaped member are in contact with each other. If the clearance between the head and the rod-shaped member at a position other than the conductive member is larger than the clearance between the conductive member and the rod-shaped member, before the head and the rod-shaped member actually contact each other, It can be detected that the rod-shaped member has come into contact. The nonmagnetic insulator is, for example, a synthetic resin.

  More preferably, the insulator is a cylindrical bobbin, the bar-shaped member is a round bar-like shape, inserted into the bobbin, and the conductive member is a pair of metal rings provided at both ends of the bobbin. is there. Contact can be easily detected by providing metal rings at both ends of the bobbin.

  Preferably, the insulator is a cylindrical bobbin, the bar-shaped member is a round bar, is inserted into the bobbin, and the conductive member is a nonmagnetic conductive material provided on the inner surface of the bobbin. It is a membrane. In this case, the conductive film can be easily formed by electroless plating or the like. Further, since the conductive film is non-magnetic, it does not hinder the magnetic interaction between the head coil, Hall element, etc., and the rod-shaped member. Examples of the nonmagnetic conductive film include an Al film and a Cu film. The conductive film may be provided on the entire inner surface of the bobbin, but may be a pattern such as a coil shape or a ring shape.

  Particularly preferably, the contact detection circuit includes a photocoupler that emits light by a current between the conductive member and the rod-shaped member. If it does in this way, a contact can be detected, insulating a conductive member easily from other parts.

  Particularly preferably, air bearings are provided on both outer sides of the bobbin to maintain a clearance between the head and the rod-like member by an air flow. If it does in this way, a head can be made non-contact with respect to a rod-shaped member, and it can support with predetermined clearance.

Sectional drawing of the principal part of the position sensor of an Example Partial enlarged sectional view of FIG. Sectional view of a bobbin with a conductive film for contact detection Sectional view of the linear actuator of the embodiment The figure which shows the Example regarding a flat position sensor typically

  In the following, an optimum embodiment for carrying out the present invention will be shown. The scope of the present invention should be determined in accordance with the understanding of those skilled in the art based on the description of the scope of claims, taking into consideration the specification and well-known techniques in this field.

  1 to 5 show an embodiment and modifications thereof, and the same reference numerals denote the same parts. FIG. 1 shows an embodiment of the position sensor 2, 4 is a detection head, 6 is a rod to be detected and is round, and magnetic marks 7 and 8 are alternately provided at a predetermined pitch. In the embodiment, the movable detection rod 6 (hereinafter referred to as “rod 6”) moves forward and backward in the x direction of FIG. 1 with respect to the fixed detection head 4 (hereinafter referred to as “head 4”). The position of the movable head 4 may be detected. The magnetic marks 7 and 8 are composed of permanent magnets or magnetic and nonmagnetic materials. The drive circuit 10 drives the head 4, and the contact detection circuit 12 detects contact between the head 4 and the rod 6.

  An excitation coil 16 and a detection coil 18 are provided on the outer periphery of a non-magnetic and insulating cylindrical bobbin 14 made of synthetic resin, and metal rings 20 are provided on both ends of the bobbin 14. A pair of air bearings 22 are provided on both outer sides of the bobbin 14, for example, at positions away from the metal ring 20, and support the rod 6 in a non-contact manner with a clearance of, for example, about 5-20 μm. The clearance between the metal ring 20 and the rod 6 is equal to or less than the clearance between the air bearing 22 and the rod 6. Reference numeral 24 denotes a head housing. The air bearing 22 has an inner peripheral portion made of a porous sintered metal, supplies an air flow from an air source 26 such as a compressor, an air pump, a tank, an air pipe, etc., toward the clearance with the rod 6, Air is jetted from the part to support the rod 6.

  The drive circuit 10 applies an alternating current having an angular frequency ω from the excitation circuit 28 to the excitation coil 16, processes the current flowing through the detection coil 18 by the signal processing circuit 30, and uses the magnetic marks 7 and 8 as a reference. The relative position of the rod 6 is detected and output from the output unit 32 to the host controller. These details are described in, for example, Patent Document 1 (Patent 4047947). The detection coil 18 may also be used as the exciting coil 16, and other magnetic elements such as a Hall element and a magnetoresistive element may be used in addition to the coil.

  The pair of metal rings 20 are connected in parallel to the light emitting diode side of the photocoupler 38, 34 may be a direct current power supply, an alternating current power supply, and 36 is a resistor. The contact detection circuit 12 is configured by the power source 34 to the photocoupler 38, and the metal ring 20 is electrically insulated from other than the contact detection circuit. Then, the rod 6 is connected to the other input of the contact detection circuit. Since the metal ring 20 is electrically insulated from other than the contact detection circuit, the current flows through the photocoupler 38 only when one of the metal rings 20 contacts the rod 6. 1, the rod 6 may be grounded, for example, and the negative side of the power supply 34 may be grounded, and there is no need to wire directly between the power supply 34 and the rod 6.

  The clearance between the rod 6 and the bobbin 14 and ring 20 is shown in FIG. C1 is the clearance between the rod 6 and the bobbin 14, and is the minimum value when the clearance is not constant. C2 is the clearance between the rod 6 and the ring 20. By making the clearance C2 less than the clearance C1, preferably less than the clearance C1, the metal ring 20 is surely brought into contact with the rod 6 before the rod 6 comes into contact with the bobbin 14. Can be made.

  FIG. 3 shows an example in which a conductive film 40 is used instead of the metal ring 20. The conductive film 40 is a non-magnetic metal film such as Cu or Al, and is provided on the inner surface of the bobbin 14 by, for example, electroless plating. Similarly, the conductive film 40 is connected to the contact detection circuit 12 to connect the conductive film 40 and the rod. Detect contact.

  FIG. 4 shows a linear actuator 41 of the embodiment, in which permanent magnets 43 and 44 are alternately arranged on the rod 42. Although the conductive film 40 is provided on the inner surface of the bobbin 14, the metal rings 20 may be provided on both ends of the bobbin 14. Reference numeral 45 denotes a drive coil, and 46 denotes a drive circuit, which includes an air source 26 or an air pipe, and these are supported as head 41 by air bearings 22 at both ends of the head 41. The rod 42 is fixed to the columns 48, 48, and the head 47 is supported by the rod 42 without contact by the air bearing 22 and moves, and the contact between the rod 42 and the head 47 is detected by the conductive film 40. A member such as a hand (not shown) is attached to the head 47 and moved to a desired position by the drive coil 45. Other points are the same as those of the embodiments of FIGS.

  FIG. 5 shows a flat position sensor 50, 51 is a flat plate with an insulator base, and a detection coil 18 and an excitation coil 52 are attached thereto. Permanent magnets 56 are arranged in a straight line to form a flat magnet array 54, and the position of the base 51 with respect to the magnet array 54 is detected by the excitation coil 52 and the detection coil 18. The magnet row corresponds to a rod-shaped member, one of the base 51 and the magnet row 54 is movable, and the other is fixed. The contact between the base 51 and the magnet array 54 is detected by the conductive film 40 and the contact detection circuit 12, but instead of the conductive film 40, metal members are provided at both ends of the base 50, etc. Contact may be detected. In this case, the clearance between the metal member and the magnet array 54 is set to be equal to or less than the clearance between the base 51 and the magnet array 54.

The embodiment has the following characteristics.
The contact between the head 4 etc. and the rod 6 etc. can be detected in advance, so that the position sensor 2 can be prevented from being worn, degraded in performance and failure.
-By providing the metal ring 20 or the conductive film 40, the contact between the head 4 and the rod 6 and the like can be detected easily and accurately.
By using the air bearing 22, the head 4 and the rod 6 and the like can be supported in a non-contact manner.
By using the photocoupler 38, the current due to the contact between the head 4 and the rod 6 can be accurately detected.

2 Position sensor 4 Detection head 6 Detected rods 7 and 8 Magnetic mark 10 Drive circuit 12 Contact detection circuit 14 Bobbin 16 Excitation coil 18 Detection coil 20 Metal ring 22 Air bearing 24 Housing 26 Air source 28 Excitation circuit 30 Signal processing circuit 32 Output Unit 34 DC power supply 36 Resistance 38 Photocoupler 40 Conductive film 41 Linear actuator 42 Rod 43, 44 Permanent magnet 45 Drive coil 46 Drive circuit 47 Head 48 Strut 50 Position sensor 51 Base 52 Excitation coil 54 Magnet array 56 Permanent magnet

C1, C2 clearance

Claims (9)

A magnetic device comprising a movable part and a fixed part, and using a magnetic interaction between the movable part and the fixed part,
The movable part and the fixed part are arranged in a non-contact manner,
A magnetic device comprising a contact detection unit that detects contact between the movable unit and the fixed unit. One of the movable part and the fixed part is a head composed of a magnetic element disposed on a nonmagnetic insulator,
The other of the movable part and the fixed part is a rod-shaped member composed of a row of permanent magnets or a row of magnetic and non-magnetic materials,
The contact detector is
A conductive member attached to the insulator;
A contact detection circuit that applies a voltage between the conductive member and the rod-shaped member, and detects contact between the head and the rod-shaped member from a current flowing between the conductive member and the rod-shaped member;
And
The conductive member is electrically insulated from other than the contact detection circuit,
2. The magnetic device according to claim 1, wherein a clearance between the conductive member and the rod-shaped member is set to a minimum value of a clearance between the head and the rod-shaped member. The insulator is a cylindrical bobbin;
The rod-like member is in the shape of a round bar, inserted through the bobbin,
The magnetic device according to claim 2, wherein the conductive member is a metal ring provided at both ends of the bobbin. The insulator is a cylindrical bobbin;
The rod-like member is in the shape of a round bar, inserted through the bobbin,
The magnetic device according to claim 2, wherein the conductive member is a nonmagnetic conductive film provided on an inner surface of the bobbin.   The magnetic device according to claim 2, wherein the contact detection circuit includes a photocoupler that emits light by a current between the conductive member and the rod-shaped member.   6. The magnetic device according to claim 2, wherein air bearings are provided on both outer sides of the bobbin to maintain a clearance between the head and the rod-like member by an air flow. The head is a detection head that detects a position of the head with respect to the rod-shaped member,
The magnetic device according to claim 2, wherein the magnetic device is a position sensor. The head includes a drive coil that relatively moves the head and the rod-shaped member;
The magnetic device according to claim 2, wherein the magnetic device is a linear actuator. For a magnetic device comprising a movable part and a fixed part, using a magnetic interaction between the movable part and the fixed part, and the movable part and the fixed part being arranged in a non-contact manner,
A contact detection method for a magnetic device, wherein a contact detection unit detects contact between the movable part and the fixed part.

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