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Electromagnetic pumpRelated Patent Categories: Pumps, Motor Driven, Electric Or Magnetic MotorElectromagnetic pump description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060239842, Electromagnetic pump. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF TECHNOLOGY [0001] The present invention relates to an electromagnetic pump, more precisely relates to a compact electromagnetic pump used for sending a fluid, e.g., gas, liquid. BACKGROUND TECHNOLOGY [0002] The inventor of the present invention invented a small and thin electromagnetic pump, wherein a moving member made of a magnetic material is reciprocally moved in a cylinder of a stator, pump chambers are respectively formed between both end faces of the cylinder and both side faces of the moving member extended in the moving direction thereof, electromagnetic coils are fitted around periphery of the cylinder, a fluid is introduced into one of the pump chambers from outside via a first valve and discharged outside via a second valve by applying electricity to the electromagnetic coils, and the fluid is introduced into and discharged from the other pump chamber by the same manner (see Patent Document 1). In FIG. 11, magnetic fluxes generated from an N-pole of a magnet 103 of the moving member 101 form a magnetic circuit to an S-pole of the magnet 103 via an inner yoke 104a, an outer yoke 105 and an inner yoke 104b. By applying electricity to electromagnetic coils 106a and 106b, an electromagnetic force is applied to the electromagnetic coils 106a and 106b from the magnetic field, but the electromagnetic coils 106a and 106b are fixed to the stator 101 so that the moving member 102 is moved in the axial direction (in the vertical direction in FIG. 11) as a counteraction. [0003] Patent Document 1: Japanese Patent Application No. 2002-286188 [0004] In the above described electromagnetic pump, a normal or abnormal motion of the moving member 101, which is accommodated in a cylinder section 109 whose both ends are closed by frames 107 and 108, and a normal or abnormal movable range of the moving member 101 are detected by various manners. For example, as shown in FIG. 11, the motion of the moving member 101 is detected by a magnetic sensor (e.g., hall element) 110 provided outside of the lower frame 108. The magnetic sensor 110 detects leakage fluxes generated by the magnet 103 of the moving member 101, so that operating positions of the moving member 101 can be detected. DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0005] In the electromagnetic pump shown in FIG. 11, the moving member 101 is accommodated in the cylinder section 109 closed by the frames 107 and 108, so the magnetic sensor 110 cannot be located close to the moving member 101. Magnetic flux density leaked from the moving member 101 is small; if the magnetic sensor 110 is located at a position separated away from the moving member 101, a size of the pump must be large, further magnetic flux density detected by the magnetic sensor 110 must be further small so that variation of magnetic flux density cannot be detected. For example, if the magnetic sensor 110 is provided to one of the frames 107 and 108, variation of magnetic flux density is always detected in one direction, so polarity reversal caused by the reciprocating motion of the moving member 101 is not detected and sensitivity of the sensor must be limited. [0006] The magnetic sensor 110 is easily influenced by magnetic fields produced by the electromagnetic coils 106a and 106b. Namely, a cycle time of the reciprocating motion of the moving member 101 is equal to that of variation of magnetic flux density leaked from the moving member 101. Further, a magnetizing cycle time of the electromagnetic coils is also equal. Therefore, it is difficult to judge if the variation of magnetic flux density detected by the magnetic sensor is caused by the reciprocating motion of the moving member 101 or magnetization of the electromagnetic coils 106a and 106b. [0007] The present invention has invented to solve the above described problems, and an object is to provide an electromagnetic pump capable of highly precisely detecting operating positions of a moving member without enlarging the pump and minimizing influence of magnetic field produced by supplying electricity to an electromagnetic coil. [0008] To achieve the object, the present invention has following structures. [0009] The electromagnetic pump comprises: a cylinder; a moving member being movably accommodated in the cylinder, the moving member having a permanent magnet; an air-core electromagnetic coil being fitted around the cylinder, the electromagnetic coil reciprocally moving the moving member in the axial direction when electricity is supplied to the coil; and pump chambers for sending a fluid, the pump chambers being formed in the cylinder, said pump is characterized in that an air-core detecting coil for detecting reciprocating motion of the moving member is fitted around the cylinder so as to be coaxial with the electromagnetic coils. [0010] In the electromagnetic pump, a plurality of the electromagnetic coils may be fitted around the periphery of the cylinder, and the detecting coils may be respectively provided close to axial end faces of the electromagnetic coils. [0011] In the electromagnetic pump, yokes made of a magnetic material may be provided to axial end faces of the detecting coil or the axial end faces and an outer circumferential face thereof. [0012] In the electromagnetic pump, frequency of induced voltage of the detecting coil may be twice as high as frequency of the reciprocating motion of the moving member. [0013] In the electromagnetic pump, flow volume of the pump may be detected on the basis of the induced voltage detected by the detecting coil; flow volume of the pump greater than a prescribed value or not may be detected on the basis of a threshold value of the induced voltage detected by the detecting coil; a normal or abnormal reciprocating motion of the moving member may be detected on the basis of a threshold value of the induced voltage detected by the detecting coil; and motion of the moving member may be controlled on the basis of a threshold value of the induced voltage detected by the detecting coil. [0014] Further, the induced voltage detected of the detecting coil may be detected in a detection range, in which variation of the induced voltage caused by magnetization of the electromagnetic coil is small. EFFECTS OF THE INVENTION [0015] In the electromagnetic pump of the present invention, the air-core detecting coil for detecting reciprocating motion of the moving member is fitted around a periphery of the cylinder, in which many magnetic fluxes leak from the moving member, and coaxial with electromagnetic coils, so that the induced voltage of the detecting coil caused by the reciprocating motion of the moving member 101 can be increased, detecting accuracy can be improved and the motion of the moving member can be detected without enlarging the pump. [0016] If the yokes made of the magnetic material are provided to the axial end faces and the outer circumferential face of the detecting coil, number of magnetic fluxes, which are generated from the moving member and which interlink the detecting coil, can be increased, so that the induced voltage of the detecting coil can be increased and detecting sensitivity can be improved. [0017] If the frequency of the induced voltage of the detecting coil is twice as high as that of the reciprocating motion of the moving member, the frequency can be twice as high as that of a magnetic field produced by the electromagnetic coil, whose magnetizing frequency is equal to the frequency of the reciprocating motion of the moving member; the variation of magnetic flux density caused by the reciprocating motion of the moving member and the variation of magnetic flux density caused by the magnetization of the electromagnetic coil can be easily distinguished. [0018] Further, the reciprocating motion of the moving member and the flow volume of the pump can be detected on the basis of the induced voltage of the detecting coil, and the motion of the moving member can be controlled. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading about Electromagnetic pump... Full patent description for Electromagnetic pump Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electromagnetic pump patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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