MXPA00001248A - Flux shaping pole pieces for a magnetic displacement sensor - Google Patents

Abstract

A displacement sensor includes a magnet assembly having a housing for mounting to one of first and second relatively moveable elements. First and second magnets are mounted to the magnet assembly housing so that the north pole of one magnet confronts the south pole of the other magnet, and vice versa. The first and second magnets form a longitudinal space between them. A flux-shaping pole piece on each of the poles have configurations to sculpt fringing magnetic flux in the longitudinal space so that magnetic flux density in the longitudinal space varies substantially linearly along a line in the longitudinal space between the confronting poles of the magnets. A magnetic field sensor assembly has a housing for mounting to the other of the first and second elements. A magnetic flux sensor is mounted to the sensor housing on the linein the longitudinal space between the first and second magnets. In one embodiment, each of the flux-shaping pole pieces has a pentagon shape in a plane of primary flux pattern, forming a narrow face confronting the longitudinal space between the first and second magnets. The narrow face of each flux-shaping pole piece is wider across the primary flux pattern than along the length of the line in the longitudinal space.

Description

POLAR FLOWER FORMATS FOR A POP MAGNETIC DISPLACEMENT DETECTOR BACKGROUND OF THE INVENTION The present invention is a magnetic displacement detector having a magnetic circuit reluctance that is constant with displacement. More specifically, the present invention is a magnetic displacement detector having improved magnetic flux forming pieces to improve performance. Typically, magnetic displacement detectors include a flux generator that provides a constant source of flux. magnetic and a feedback device that measures the flow. Usually, the flow generator is mounted on one element and the pickup device is mounted on another element so that the magnetic flux density detected by the pick-up device is based on the displacement between the elements. Magnetic displacement detectors usually measure linear or rotational displacement and provide a result proportional to the displacement of the absolute linear or rotary position of the elements. Magnetic displacement detectors can use electromagnets or permanent magnets as a source of magnetic flux. A pickup device (eg, a magneto resistor or a magneto diode, or a Hall effect detector) intersects the magnetic flux and detects changes in the magnetic field produced by the magnets. Magnetic displacement sensors are commonly used in cooperation with microprocessors in remote control systems with field devices. For example. Magnetic displacement sensors can be used to check valve positions = Examples of the magnetic displacement sensors of the prior art are found in Prinz et al. Patente Est douni lect No-4,532,810, - Wolf et al 5,497,081 and Riggs et al = United States Patent No, 5r 59,? 88- The useful range of the sensors by magnetic displacement is limited by the expansion of the flow of the magnets = When two permanent magnets are aligned side by side, the mechanical characteristic of each magnet and its proximity to another polar face of magnet determines the distribution of the magnetic flux from the face, polar to the opposite polar face = At the magnetic poles, between the magnets appears the expansion of the flow * The variations in the expansion of the flow are non-linear, and therefore, the magnetic field detected by the sensor by magnetic displacement varies in a non-linear way with the displacement = This non-linearity gives rise to inaccurate readings and errors in the detector, limiting the useful range and effectiveness of magnetic displacement detectors = BRIEF COMPENDIUM OF THE INVENTION The present invention is directed to the polar flow-forming parts for the polar faces of magnets of a magnetic displacement sno = According to one aspect of the invention, a displacement sensor detects the relative displacement between the first and second lem. The displacement detector includes a magnet unit having a housing for mounting to the first or second element = The first and second magnets are mounted to the housing of the magnet unit so that the north pole of a magnet faces the pole south of the other magnet and vice versa. The housing of the magnet unit supports the first and second magnets to form a longitudinal space between the first and second magnets. A polar flow-forming piece is provided at each of the poles of the rim r "and second magnets.The pluriform flow-forming pieces together having configurations to shape the expansion of the magnetic flux in the longitudinal space, so that the Magnetic flux density in the longitudinal space varies substantially linearly throughout the longitudinal space between a point between the north pole and the first magnet and the south pole of the second magnet and a point between the south pole of the first magnet and the pole north of the second magnet A magnetic field detector unit has a housing for mounting to the other of the first or second element A magnetic flux detector is mounted in the detector housing on the line in the longitudinal space between the second and second magnets In one mode of the displacement detector, the polar parts of the flow pharmacies are metallic polar pieces joined to each pole of the first and second magnets. The magnetic force presented by the magnets can be used to keep the opal parts in contact with the magnetic poles. Otherwise, the pole pieces can be attached to the magnetic poles with adhesive. In another embodiment of the displacement detector, polar fluxes are integrated into the first and second respective magnets. In yet another embodiment of the displacement detector, the first and second magnets are permanent magnets. In yet another embodiment of the displacement detector, each of the polar flow-forming parts has a pentagonal shape in a plane of the primary flow pattern, forming a narrow face by confronting the longitudinal space between the first and second magnets.; In one aspect of this displacement detector mode, the narrow face of each polar flow-forming part is wider through the primary flow pattern than along the length of the line in it. longitudinal space. According to another aspect of the invention, there is provided a polar pole-forming piece for a pole of a magnet of a magnetic shift detector that detects relative displacement between the first and second elements. The magnet must be arranged with another magnet so that a north pole of a magnet confronts a south pole of the other magnet and vice versa to form a longitudinal space between the magnets. The pole piece contains an agnatic-shaped material to sculpt the expansion of the magnet. magnetic flux in the longitudinal space, so that the density of the magnetic flux in the longitudinal space varies in a substantially linear manner along a line in the longitudinal space between a point between the north pole of the magnet and the south pole of the other magnet, and a point between the south pole of a magnet and the north pole of the other magnet. In one embodiment of the flow forming pole piece, the polar flow forming piece is a metallic pole piece attached to a pole of the magnet. The magnetic force presented by the magnet can be used to keep the pole piece in contact with the magnetic pole. Otherwise, the pole piece may be attached with adhesive to the magnetic pole.

In another embodiment of the flow forming pole piece, the polar flow forming piece is integrated to the magnet. In another form of. the flow forming pole piece, the polar flow forming piece has a pentagon shape in a plane of the primary flow pattern, forming a narrow face confronting the longitudinal space between the magnets = In one aspect of this invention the forming oval piece of flow, the angled face of the polar piece forming flow is wider through the primary flow pattern than along the length of the line in the longitudinal space.

BRIEF DESCRIPTION OF THE DRAWINGS T. FIG 1 is a perspective view of a magnetic displacement detector with polar flow-forming parts of the present invention.

FIGURE 2 is a perspective view, amplified, with separate portions for the purpose of clarity, of the magnetic shift detector shown in FIGURE 1 FIGURE 3 is a perspective view of a magnetic block unit and a magnetic field detector unit of the magnetic displacement detector generally taken in the direction of arrow 3 in FIGURE 2- FIGURE 4 eS A top view of the units shown in FIGURE 3. FIGURE 5 is an exploded view of the block unit shown in FIGURES 3 and 4. FIGURE 6 is a perspective view, with portions not shown for purposes of clarity, of the magnets of the magnetic block unit with a magnetic field detector between the magnets = FIGURE 7 s a diagram illustrating the unit of the magnetic block shown in FIGURES 3-5 and the associated flow pattern.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES FIGURE 1 a perspective view of a magnetic displacement detector with polar flow forming parts according to the presently preferred embodiment of the present invention. The magnetic displacement detector consists of a moving magnetic unit 10 (shown in greater detail in FIGS. 2-5) and a magnetic field detecting unit 20 = The magnetic field detecting unit 20 is mounted to a stationary housing for instruments 30 and a stationary actuating fork 2 by mounting the rake 34. As shown in FIGURE 2, the magnetic unit 10 is arranged for linear or reciprocal movement of the valve stem 106 in the direction of the arrow 38 = The connector of the rod 102 is connected between the actuator rod and 104 [sic] and the stem of the valve 106. The stem of the actuator 104 transmits linear movement of a valve actuator, such as a pressure-sensitive diaphragm (not shown) to the piston rod. the valve 106, which in turn operates a valve plug. { not shown) in a manner well known in the art for opening and closing the valve under control. As shown in particular in FIGS. 2_, the magnetic unit 10 consists of a housing 50 supporting the permanent bar magnets 5 and 54 in the cavities 64 and 66. As shown particularly in FIGURE 5, the magnets 52 and 54 are arranged so that one of the magnets, like r > can be magnet 52, have its north pole 56 oriented towards the top of the housing 50 and its south pole 58 oriented would make the bottom of the housing 50 not. The other magnet, such as magnet 54, is oriented opposite the magnet 52 with its ot 6 pole? in the lower part of the housing 50 and its south pole 6 n in the upper part of the housing 50 = The housing 50 guides the magnets 52 and 54 so that the confronting surfaces 57 are parallel to each other and to the longitudinal line 81 in the space ngitudinal enters the magnets. Although magnets 52 and -54 can be electromagnets or permanent magnets, a permanent magnet is preferred because it can be easily incorporated into the detector and does not require a separate power source. The magnets 52 and 54 of pref r nci are Alnico V magnets. It will be appreciated that the magnets 52 and 54 are a source of constant magnetic flux. As shown particularly in FIGURE 5, a pole forming part of the flow 70 is connected to each of the poles 56, 58, 60 and 62 of the magnets 52 and 54. The pole pieces 70 can be composed of any suitable magnetic material, such as steel rolled in cold G10100. Because the pole pieces are magnetic, the magnetic force presented around the magnets 52 and 54 keeps the pole pieces 70 in contact with the magnetic poles, and no epoxy substances, adhesives or the like are required. Otherwise, it is possible to use an adhesive to join the pole pieces 70 to the respective magnetic pole. In an alternative embodiment of the present invention, the polar flow-forming parts 70 are not separate components of the magnets 52 and 54, but they are an integrated part of the magnets themselves. So, magnets 5? and 54 can be fused with the pole pieces 70 integrated with or part of the magnets. In such a mode, each magnet (with the pole pieces) is the only component that is placed in the cavities 64 and 66 of the housing 50. The pole pieces 70 provide optimum operation of the magnetic shift detector. Typically, the magnets show flow expansion at the poles, giving rise to non-linear flow variations that cause non-precise or erroneous operation of the magnetic displacement detector. The pole pieces 70"sculpt" the magnetic flux to provide a linear change in the density of the flux. By sculpting the flow expansion, the pole pieces 70 make linear the flow di sobreections over the length of the magnets, thereby drastically increasing the usable range of the magnets and the magnetic displacement detector. As shown particularly in FIGS. 5 and 7, the pole pieces 70 have a pentagon shape, when observed in the plane of the primary flow pattern (FIGURE 7), having two pairs of parallel surfaces normal to each other. The narrow surface 71 of the pentagon forms a narrow face that is significantly wider through the primary flow pattern (in the paper of FIGURE 7 and along the line 83 in FIGURE 5) compared to the direction along of the length of the magnets 52 and 54 = More specifically, we have experimentally determined that the pentagon shape of the pole pieces 7Q optimizes the linear operation over the entire length of the magnets of the magnetic displacement detector. The size of the pentagonal pole pieces 70 is based on the distance of the separation between the magnets 52 and 54, the length of the magnets and the cross-sectional area thereof. Thus, the different sizes of the magnets and the separation requires different size of the pentagon in the pole piece. It is important for the present invention that the face 71 of the respective pentagonal pole pieces 70 be parallel to the surface 5 of the respective bar magnet 52 and 54. If a 53 of a pole of the magnet is not perpendicular to the surface 57 of the respective magnet , it may be necessary to insert a magnetic wedge or other separator (or even an adhesive) between the face 53 of the magnet and the face 55 of the respective pole piece 70 so that the face 71 is parallel to the surface 57 of the magnet. Therefore, if polar car 53 has a notch or is otherwise damaged to provide a face not perpendicular to the length of the magnet, repair by wedge may make the magnet useful. As particularly illustrated in FIGS. 3 and 4, the magnetic field detector unit 20 includes a non-magnetic cylinder 82 that extends between the magnets 52 and 54 in the housing 50. The materials acceptable for the cylinder 82 are aluminum or ceramics. The cylinder 82 contains a magnetic field detector 80, such as a Hall effect detector, placed in proximity to the magnetic unit 10 between the magnets 52 and 54. The magnetic field detector 80 is mounted inside the cylinder 82 by a bushing of acetal plastic 85, keyed for the precise position of the detector 80 inside the cylinder 82 within O.Q02 inches. The cylinder 84 is inserted into the instrument housing 30 (FIGURES 1 and 2) and allows feeding for the wiring of the electronics. In a fox of the invention, the housing 30 is formed of a non-magnetic material, suitable as it can be aluminum or rigid plastic. A nonmagnetic fastener 86 mounts the housing of the detector unit 20 to the housing 30 and the mounting arm 34 mounts the housing 30 to the stationary actuating fork 32 r Co or shown in FIGURE 2, the housing 50 of the magnetic unit 10 it is attached to the console 90 by key bolts 92, sheaves 94 and nuts 96 clamped through the restrictive slots 98 and 100 in the housing 50. In addition, the console 90 is connected to a rod connector 102 which engages a rod. threaded actuator 104 to a valve stem 106 of a valve. Therefore, the magnet unit 10 is rigidly mounted to the valve stem / actuator unit of the valve whose position is being verified by the displacement sensor of the present invention. As the stem of the valve 106 moves in the direction of the arrow 38, the connector of the rod 102 and the console 90 move the magnet unit 10 relative to the magnetic field detector unit 20. The magnetic field detector 80 (FIGURE.6) remains stationary because it is coupled to the stationary actuating fork 32 and to the instrument housing 30. The movement of the magnet unit 10 in the direction of the arrow 38 causes a relative displacement between the magnet unit and the magnetic field detector 80 within the magnetic field detecting unit 20. Thus, the magnetic flux density through the magnetic field detector 80 varies with the displacement of the actuator 104 and the valve stem 106. FIGURE 6 illustrates a perspective of the magnetic field detector 80 located between the magnets 52 and 54 attached to the polar flow-forming parts 70, and FIGURE 7 illustrates the lines of the magnetic flux. 110 between the magnets 52 and 54 = De ^ reference, the magnets 52 and 54 are of equal magnetic intensity, so that the line 81 is centered between and parallel to. the. surface 57 d the magnets 52 and 54, the line 83 is orthogonal to the line 81 in a direction along the width of the surfaces 57 and the line 83 intersects the line 81 at the midpoint 112 centered between the pole pieces and centered between the banks of. magnets 53 and 54 a. along the surface of the surfaces 57 (FIGURES 5 and 7). At point 112, the magnetic flux density is zero (zero) = The detector is c replaced by replacing the detector 80 at the midpoint 112 where the magnetic field strength is zero and calibrating the detector. Along the longitudinal line 81 between the magnets, the flux density increases uniformly from the midpoint of the unit towards the poles, at a maximum flux density directly between the faces of the poles 71 = Because the poles are oriented opposite, the flow directions are opposite in the regions along line 81 on each side of the midpoint. Thus, the flux density varies along the line 81 from a maximum in one direction between a series of polar faces, through zero at the midpoint 112, at a maximum of the opposite direction between the other series of polar faces. polar faces. In use, the magnetic field detector 80 is oriented in between the magnets 52 v 54 on the line 81 so that as the magnet unit reciprocates in the direction of the arrow 38 (FIGURE 2) parallel to the line 81, the detector 80 crosses the flow pattern between the magnets by sliding and produces a voltage proportional to the relative position of the magnetic field detector 80 in relation to the magnet unit 10 = When sculpting the flow expansion, the pole pieces 70 They make linear the flow measurements on the length of the magnets. Thus, the pole pieces 70 drastically increase the useful range and accuracy of the voltage readings produced by the magnetic field detector 80.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that it is possible to make changes in shape and detail without departing from the spirit and scope of the invention.

Claims (1)

1- A displacement test to detect the relative displacement between a first and second elements, consists of: a unit of magnets having a housing of the unit d magnets to the assembly to the first lm nt, the first and second magnets mounted to the housing of the magnet unit so that a north pole of the first magnet confronts a south pole of the second magnet and a south pole of the first magnet confronts a north pole of the second magnet, where the magnet unit housing supports a first magnet and second magnets for forming a longitudinal space between the first and second im- ages, and a polar forming part for flow at each north and south pole of the first and second magnets, the polar flow-forming parts having configurations for sculpting the expansion of the magnetic flux. in the longitudinal space so that the magnetic flux density in the longitudinal space varies substantially imeal along a line in the longitudinal space which e is substantially substantially parallel to the length of at least one of the magnets and between the opposite poles of the first and second; and a magnetic field detecting unit having: a detector housing for mounting to the second magnet, and a magnetic flux detector mounted in the detector housing on the line in the longitudinal space between the first and second images; The displacement detector of claim 1, wherein the first and second magnets are permanent magnets: 3. The displacement detector of claim 1, wherein each of the polar flow-forming parts is a metallic pole piece attached to a respective pole of the first and second magnets - 4. The displacement detector of claim 3, wherein the pole pieces are joined to the respective pole by a magnetic force presented by the respective magnet 5. The displacement detector of claim 1 , wherein each polar flow forming piece is integrated into the first and second respective magnets, 6. The displacement detector of claim 1, in where the first and second magnets are magnets I of practically equal lengths and practically equal widths and having poles at the opposite ends, where the magnets I form surfaces with riss practically parallel to each other to form the longitudinal space, and where the line in the longitudinal space it is practically parallel to both opposite surfaces and extends along the magnets at an intermediate location between the opposing surfaces and in the middle of the widths of the magnets. 7. The displacement detector of claim 1, wherein each of the flow-forming polar pieces has a pentagon shape in a plane of a primary flow pattern through the 1f space. longitudinal, the shape of a pentagon forming a narrow face in front of the longitudinal space between the first and second man n and parallel to the line in the longitudinal space. 8. The displacement detector of claim 1, wherein the narrow face is in a plane parallel to the length of the respective magnet. The displacement detector of claim 8, wherein each of the poles has a pole face substantially perpendicular to the length of the respective magnet, and each of the pole pieces forming the flow is a metal pole piece having a second pole. face appended to a respective polar face, the second face being perpendicular to the narrow face, and the pole piece facing the respective pole so that the narrow face is parallel to the length of the magnet. 10. The displacement detector of claim 9, wherein the angled face of each polar flow-forming part is wider through the primary flow pattern than along the line in the longitudinal space. of displacement of the reiki / mdication 7, where the narrow face of each polar piece forming flow is wider through the primary flow pattern than along the line in the longitudinal space 12 The displacement detector of the vindication?, wherein each of the polar flow forming parts is a metallic pole piece attached to a respective pole of the first and second imane. The displacement detector of claim 12, wherein the narrow face of each polar flow-forming part is wider through the primary flow pattern than along the length of the line in the longitudinal-14 space. The displacement detector of claim 7, wherein the first or second element is a housing of the valve actuator and valve stem and the other of the first or second element is a stationary housing, by means of which the displacement detector detects the linear displacement between the stem of the valve and the stationary housing. 15. The displacement detector of claim 1, wherein the first or second element is a valve actuator housing and valve stem and the other of the first or second element is a stationary housing, by means of which the displacement detector detects linear displacement between the valve stem and the stationary housing. 16. A polar flow-forming piece for a pole of a first magnet of a magnetic shift detector for detecting the linear displacement between the first and second elements, n where the first magnet is arranged with a second magnet, so that a north pole of the first magnet is facing a south pole of the second magnet and a south pole of the first magnet is facing a north pole of the second magnet to form a longitudinal space in the first and second magnets, the pole piece consists of: magnetic material having a joining surface arranged to join the pole of the first magnet, and a configuration so arranged and arranged so that when a pole piece is joined to the poles of the kidney and second to each of the pol rs pieces Sculpts the expansion of the magnetic flux in the longitudinal space so that the density of the magnetic flux in the longitudinal space varies in a substantially linear manner over a period of time. Line in the longitudinal space between the opposite poles of the first and second magnets. 17. The flow forming pole piece of claim 16, wherein the polar flow forming piece is a metal pole piece for attaching to a pole of the aforementioned magnet. 18 = The polar flow-forming part of claim 17, wherein the pole piece is designed to be in contact with the magnetic pole by a magnetic force presented by the aforementioned magnet. 19. The flow-forming pole piece of claim 18, with a pentagon shape in a plane of the primary flow pattern through the longitudinal space arranged to form a narrow gap with the longitudinal space between the magnet mentioned at the beginning and the end. another magnet and parallel to the line in the longitudinal space when the pole piece is attached to the magnetic pole. 20 = The polar flow-forming piece of claim 19, wherein the narrow face is arranged parallel to the length of the magnet when the. Polar piece is attached to the pole of the magnet. The flow forming pole piece of claim 20, wherein the bonding surface is perpendicular to the narrow face, the bonding surface orienting the pole piece over the pole so that the narrow face is parallel to the length of the magnet . 22 = The polar flow-forming part of claim 19, wherein the narrow face of the polar forming part fe flow is wider through the primary flow pattern than along the length of the line in the longitudinal space when the pole piece is attached to the pole of the magnet. SUMMARY OF THE INVENTION A displacement detector includes a magnetic unit having a housing for mounting to a first and second relatively movable elements. The first and second magnets are mounted to the housing of the magnetic unit, so that the north pole of one magnet confronts the south pole of the other magnet, and vice versa. The first and second magnets form a longitudinal space between them. A polar flux forming piece at each of the poles has configurations for sculpting the magnetic flux that forms fringes in the longitudinal space, so that the density of the magnetic flux in the longitudinal space varies in a substantially linear sense along a length of line in the longitudinal space between the opposite poles of the magnets. A magnetic field detector unit has a housing for mounting the other first or second element. A magnetic flux detector is mounted to the sensor housing in the line, in the longitudinal space between the first and second magnets. In one embodiment, each polar flux-forming piece has a pentagon shape in a design plane of the primary flux, forming a narrow face in front of the longitudinal space between the first and second magnets. The narrow face of each flux forming polar piece is wider through the design of the primary flux than along the length of the line in the longitudinal space.