JP2004286637A - Displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized displacement sensor for detecting precisely the displacement amount of a moving body moving linearly. <P>SOLUTION: This displacement sensor is provided with a cylindrical magnetic substance 30 moving together with the moving body, and a magnetic detecting element 40 therein. The magnetic substance 30 stores relatively movably the magnetic detecting element 40 in a cylindrical hole 34 extended with a fixed diameter along a moving direction α of the moving body, and forms magnetic poles N, S different each other in both end parts along the moving direction α. The magnetic substance 30 has a straight part 36 provided in an end part 31a of the magnetic substance 30 where the cylindrical hole 34 is opened, and of which the radial-directional thickness is constant along the moving direction α, and a changing part 38 provided adjacently to the straight part 36, and of which the radial-directional thickness is reduced along the moving direction α in accompaniment to approach to the straight part 36. The displacement amount of the moving body is detected based on magnetic flux density in an inside of the cylindrical hole 34 detected by the magnetic detecting element 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a displacement sensor that detects a displacement of a moving body that moves linearly.
[0002]
[Prior art]
Conventionally, a non-contact type displacement amount sensor that moves one of a permanent magnet and a magnetic detection element that moves linearly with a moving body relative to the other, and detects a displacement amount of the moving body based on a magnetic flux density detected by the magnetic detection element. It has been known.
In the displacement sensor disclosed in Patent Literature 1, a pair of permanent magnets face each other in a direction (orthogonal direction) perpendicular to the axis of the moving direction in which the moving body moves linearly, and a magnetic detection element is provided in an air gap between the permanent magnets. Are placed. The direction of the magnetic flux density formed in the air gap by each of the permanent magnets is set in the orthogonal direction, and the thickness of each of the permanent magnets in the orthogonal direction is made smaller at the center than at both ends in the moving direction. Thus, the magnitude of the magnetic flux density in the air gap is changed from one end in the movement direction to the other end.
[0003]
However, in the displacement amount sensor disclosed in Patent Literature 1, when the magnetic detection element rotates relative to each permanent magnet around the axis in the moving direction, the relative direction of the magnetic flux density with respect to the magnetic detection element changes. For this reason, the detection value of the magnetic flux density detected by the magnetic detection element fluctuates even though the moving body does not move linearly.
[0004]
Therefore, the present inventors have studied the displacement sensor 2 in which the magnetism detecting element 6 is accommodated in the cylindrical permanent magnet 4 as shown in FIG. In the displacement amount sensor 2, by forming different magnetic poles at both ends of the permanent magnet 4 in which the cylindrical hole 5 extends along the moving direction α of the moving body, the direction of the magnetic flux density in the cylindrical hole 5 is changed to the moving direction α. To match. In addition, by reducing the thickness of the permanent magnet 4 in the radial direction from one end to the other end, the magnitude of the magnetic flux density in the cylindrical hole 5 is changed. According to the displacement amount sensor 2, even if the magnetic detection element 6 in the cylindrical hole 5 relatively rotates around the axis in the movement direction α with respect to the permanent magnet 4, magnetic detection is performed in most regions in the cylindrical hole 5. The relative direction of the magnetic flux density with respect to the element 6 is maintained. In FIG. 15A, the direction and the magnitude of the magnetic flux density are schematically shown by the direction and length of the arrow, respectively.
[0005]
[Patent Document 1]
JP 2000-180114 A
[0006]
[Problems to be solved by the invention]
However, in the displacement amount sensor 2, as shown in FIG. 15A, the direction of the magnetic flux density is inclined with respect to the movement direction α in the region inside the cylindrical hole 5 near both ends of the permanent magnet 4. Since the moving direction component of the magnetic flux density detected by the magnetic detecting element 6 is reduced by an amount corresponding to the inclination angle in the magnetic flux density direction, the linearity of the detected value of the magnetic detecting element 6 with respect to the displacement of the moving body is shown in FIG. It collapses as shown in FIG. In particular, when the magnetic detection element 6 is located near the end portion 4a where the radial thickness of the permanent magnet 4 is minimized, the magnetic flux density itself formed by the permanent magnet 4 is small. Induces large disturbances in linearity. When an area where the detection value is non-linear with respect to the displacement is used, the detection accuracy decreases. On the other hand, when such a non-linear area is not used, the displacement sensor 2 is used to secure a detection range of the displacement. It has to be enlarged.
An object of the present invention is to provide a small displacement amount sensor that accurately detects the displacement amount of a moving body that moves linearly.
[0007]
[Means for Solving the Problems]
According to the displacement amount sensor according to the first aspect of the present invention, the cylindrical magnetic body forms different magnetic poles at both ends in the moving direction in which the moving body moves linearly, and extends with a constant diameter along the moving direction. The magnetic detecting element is accommodated in the cylindrical hole so as to be relatively movable. As a result, the direction of the magnetic flux density coincides with the moving direction in most regions in the cylindrical hole. Further, the magnetic body has a change portion in which the thickness in the radial direction decreases in the moving direction. Thus, since the magnetic flux density in the cylinder hole changes in the moving direction, the displacement of the moving body can be detected based on the magnetic flux density in the cylinder hole detected by the magnetic detection element.
[0008]
In addition, the magnetic body has a straight portion provided at an end of the magnetic body where the cylindrical hole is opened and whose radial thickness is constant along the moving direction. The above-mentioned change portion is provided adjacent to the straight portion, and the thickness in the radial direction decreases as approaching the straight portion. That is, a straight portion is provided at the end of the magnetic material on the side with the smaller radial thickness. The direction of the magnetic flux density in the cylindrical hole is inclined with respect to the moving direction near both ends of the magnetic body, but the magnetic flux density in the cylindrical hole near the end of the magnetic body where the straight portion is provided is radially extended to the end. It is larger than if the thickness were reduced. Accordingly, when the magnetic body is located near the end of the magnetic body where the straight portion is provided, the detection sensitivity of the magnetic detection element is increased, and the linearity of the detected magnetic flux density with respect to the displacement amount can be secured. .
As described above, according to the displacement sensor according to the first aspect, the magnetic flux density exhibiting linearity with respect to the displacement of the moving body can be detected in a wide area in the moving direction. Can be reduced in size.
[0009]
According to the displacement amount sensor according to claim 2 of the present invention, the magnetic body is provided with a closing portion that is provided adjacent to the changing portion at an end opposite to the end where the straight portion is provided and closes the cylindrical hole. Have. That is, the magnetic body is closed at the end with the thicker radial thickness by the closing portion. Therefore, the inclination of the magnetic body in the direction of the magnetic flux density in the cylinder hole with respect to the moving direction in the vicinity of the end on the closing portion side becomes smaller than when the magnetic body is not closed. Accordingly, when the magnetic sensing element is located near the end of the magnetic body on the closed portion side, the detection sensitivity of the magnetic sensing element increases, and the linearity of the detected magnetic flux density with respect to the displacement amount can be secured. Therefore, the detection accuracy of the displacement amount is further improved, and the displacement amount sensor can be made smaller.
[0010]
According to the displacement amount sensor according to the third aspect of the present invention, the magnetic detection element moves relative to the magnetic body on the central axis of the cylindrical hole, that is, on one axis in the moving direction. Thereby, even if the magnetic detection element rotates relative to the magnetic body around the movement direction axis, the fluctuation of the magnetic flux density detected by the magnetic detection element can be sufficiently suppressed.
[0011]
According to the displacement sensor according to the fourth aspect of the present invention, when the length of the straight portion in the moving direction is L and the diameter of the cylindrical hole is φ, the dimensional ratio L / φ is 0.20 ≦ L / φ ≦ 0. .27 is satisfied. Accordingly, the linearity between the displacement amount of the moving body and the magnetic flux density detected by the magnetic detection element can be ensured with high accuracy, so that high detection accuracy can be realized.
[0012]
According to the displacement amount sensor according to claim 5 of the present invention, the magnetic body forms different magnetic poles at both ends in the moving direction in which the moving body moves linearly, and the magnetic body moves in the moving direction with respect to the magnetic detecting element moving relatively. The side surfaces extending along the direction are opposed to each other in a direction perpendicular to the axis of the moving direction. As a result, the direction of the magnetic flux density coincides with the moving direction in most regions around the side surface. Further, the magnetic body has a changing portion in which the thickness in the direction perpendicular to the moving direction decreases. Thus, since the magnetic flux density around the side surface changes in the moving direction, the displacement amount of the moving body can be detected based on the magnetic flux density around the side surface detected by the magnetic detection element.
[0013]
In addition, the magnetic body has a straight portion provided at an end of the magnetic body and having a thickness in the orthogonal direction that is constant along the moving direction. The above-described changing portion is provided adjacent to the straight portion, and the thickness in the orthogonal direction decreases as approaching the straight portion. That is, a straight portion is provided at the end of the magnetic material on the side having a smaller thickness in the orthogonal direction. The direction of the magnetic flux density around the side surface is inclined with respect to the moving direction near both ends of the magnetic body, but the magnetic flux density around the side surface near the end of the magnetic body where the straight portion is provided has a thickness in the orthogonal direction up to the end. Becomes larger than when it decreases. Accordingly, when the magnetic body is located near the end of the magnetic body where the straight portion is provided, the detection sensitivity of the magnetic detection element is increased, and the linearity of the detected magnetic flux density with respect to the displacement amount can be secured. .
As described above, according to the displacement amount sensor according to the fifth aspect, the magnetic flux density exhibiting linearity with respect to the displacement amount of the moving body can be detected in a wide area in the moving direction. Can be reduced in size.
[0014]
According to the displacement amount sensor according to claim 6 of the present invention, a plurality of magnetic bodies are arranged around the axis in the moving direction passing through the magnetic detecting element. Since the magnetic flux density around the side surface of the magnetic sensing element is increased by increasing the number of arranged magnetic bodies, the detection sensitivity of the magnetic sensing element is improved.
[0015]
According to the displacement amount sensor according to the seventh aspect of the present invention, the plurality of magnetic bodies are connected to each other by a magnetic material at ends opposite to the end where the straight portion is provided. That is, the plurality of magnetic bodies are connected to each other on the side where the thickness in the orthogonal direction is thicker by the magnetic material. Therefore, the inclination of the magnetic material around the side surface in the direction of movement of the magnetic flux density in the vicinity of the connection side end of each magnetic body is smaller than when the magnetic bodies are not connected. Accordingly, when the magnetic detection element is located near the connection side end of each magnetic body, the detection sensitivity of the magnetic detection element increases, and the linearity of the detected magnetic flux density with respect to the displacement can be ensured. Therefore, the detection accuracy of the displacement amount is further improved, and the displacement amount sensor can be made smaller.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 2 shows a displacement sensor according to the first embodiment of the present invention. The displacement sensor 10 of the first embodiment detects the displacement of the shaft 100 that moves linearly as a moving body by, for example, connecting or contacting the rod portion 22 to the shaft 100 of an EGR (Exhaust Gas Recirculation) valve of an automobile. I do.
The displacement sensor 10 includes a housing 11, a movable member 20, a magnetic body 30, and a Hall IC 40.
[0017]
The housing 11 is formed of a resin material into a bottomed cylindrical shape, and is fixed to the EGR valve. The housing 11 has a columnar protrusion 12 protruding from the bottom toward the inner magnetic body 30. The Hall IC 40 is held at the tip of the columnar protrusion 12, and a terminal 45 for extracting a detection signal of the Hall IC 40 is embedded in the connector 13 of the housing 11.
[0018]
The movable member 20 is formed of a resin material, and has a bottomed cylindrical housing portion 21 and a rod portion 22. The housing portion 21 is housed in the housing hole 15 of the housing 11 and can reciprocate in the linear movement direction α of the shaft 100. A magnetic body 30 is fixed to the bottom inner wall of the housing 21 facing the bottom of the housing 11. The rod portion 22 protrudes from the bottom outer wall of the housing portion 21 toward the shaft 100, and has a protruding end connected to or in contact with the end of the shaft 100. Thereby, the movable member 20 and the magnetic body 30 move linearly together with the shaft 100. The spring 25 serving as an urging member urges the movable member 20 toward the shaft 100.
[0019]
Next, the configuration of the magnetic body 30 will be described in detail with reference to FIGS.
The magnetic body 30 includes a permanent magnet 31 and a closing plate 32 joined to each other with an adhesive or the like, and has a cylindrical shape with a bottom as a whole. The permanent magnet 31 is formed of a ferromagnetic material such as a plastic magnet in a substantially tapered cylindrical shape, and the closing plate 32 is formed of a magnetic material in a thin plate shape. Note that the permanent magnet 31 and the closing plate 32 may be integrally formed of the same ferromagnetic material. The cylindrical hole 34 formed by the permanent magnet 31 with the inner peripheral surface 33 is a so-called cylindrical hole, and extends with a substantially constant diameter along the moving direction α in which the magnetic body 30 moves linearly with the shaft 100. One end of the cylindrical hole 34 is open in the moving direction α, and the other end of the cylindrical hole 34 is closed by a closing plate 32 as a closing portion. The opening side end 31a of the permanent magnet 31 forming one end of the magnetic body 30 and the closing side end 31b and the closing plate 32 of the permanent magnet 31 forming the other end of the magnetic body 30 have different magnetic poles N, S is formed. Thereby, as shown by the arrow in FIG. 1B, an annular magnetic flux passing through the inside of the cylindrical hole 34 of the magnetic body 30 and the permanent magnet 31 is generated. An S-pole may be formed at the end 31a, and an N-pole may be formed at the end 31b and the closing plate 32 to generate a magnetic flux in a direction opposite to that in FIG.
[0020]
The permanent magnet 31 has a straight portion 36 for making the diameter of the outer peripheral surface 35 substantially constant, and a changing portion 38 for changing the diameter of the outer peripheral surface 35. In the permanent magnet 31, the straight portion 36 is provided at the end 31a where the cylindrical hole 34 opens. The outer peripheral surface 35a of the straight portion 36 is a cylindrical surface having substantially no diameter change along the movement direction α. Thereby, the thickness of the straight portion 36 in the radial direction orthogonal to the axis of the movement direction α is kept substantially constant along the movement direction α. On the other hand, in the permanent magnet 31, the changing portion 38 is provided on the end 31b side adjacent to the straight portion 36. The outer peripheral surface 35b of the changing portion 38 is a conical surface whose diameter decreases from the end 31b toward the straight portion 36 in the moving direction α. Thus, the radial thickness of the change portion 38 decreases in the moving direction α as it approaches the straight portion 36. In the present embodiment, the generatrix of the outer peripheral surface 35b of the changing portion 38 extends linearly, and the rate of change in the radial thickness of the changing portion 38 is substantially constant over the entire area in the moving direction α. The radial thickness of the changing portion 38 at the boundary with the straight portion 36, that is, the minimum radial thickness of the changing portion 38 is equal to the radial thickness of the straight portion 36.
[0021]
The columnar projection 12 is coaxially inserted into the cylindrical hole 34 of the permanent magnet 31 from the opening side, and the Hall IC 40 is housed in the cylindrical hole 34. The Hall IC 40 has a Hall element 42 that senses the magnetic flux density in the cylindrical hole 34, and a processing circuit 43 that outputs a detection signal obtained by processing an output signal of the Hall element 42 to the terminal 45. The Hall IC 40 is arranged so that the center axis O of the cylindrical hole 34 passes through the center of the detection surface of the Hall element 42 almost perpendicularly, and moves relative to the magnetic body 30 on the center axis O. The Hall element 42 senses the moving direction component of the magnetic flux density in the cylindrical hole 34 at a position corresponding to the relative displacement of the Hall IC 40 with respect to the magnetic body 30. The voltage value of the detection signal output from the Hall IC 40 is proportional to the magnitude of the moving direction component of the magnetic flux density detected by the Hall element 42. In the present embodiment, the Hall IC 40 having both the Hall element 42 and the processing circuit 43 constitutes a magnetic detection element. Note that the Hall element 42 may be separated from the processing circuit 43 and only the Hall element 42 may be held in the columnar projection 12 as a magnetic detection element, or a magnetoresistive element or a combination of a magnetoresistive element and a processing circuit may be used. The columnar projection 12 may be held as a magnetic detection element.
[0022]
Assuming that the relative displacement of the Hall IC 40, that is, the displacement of the shaft 100, with respect to the end face position of the opening end 31a of the permanent magnet 31 in the moving direction α is X, and the voltage value of the detection signal of the Hall IC 40 is V, the voltage The value V shows a correlation as shown in FIG. However, the two-dot chain line in FIG. 3B is an ideal curve I when the correlation between the displacement X and the voltage value V shows linearity. 3A, the direction and magnitude of the magnetic flux density are schematically indicated by the directions and lengths of arrows, respectively. As shown in FIG. In the vicinity, it is inclined with respect to the movement direction α. However, in the displacement sensor 10, since the straight portion 36 is provided at the end 31a of the magnetic body 30 on the side where the thickness in the radial direction is thinner, the vicinity of the end 31a is larger than that of the conventional example of FIG. A large magnetic flux density can be obtained. Thereby, when the Hall IC 40 is located near the end 31a of the magnetic body 30, the moving direction component of the magnetic flux density sensed by the Hall element 42 increases, and the detection sensitivity of the Hall element 42 improves. Therefore, the voltage value V proportional to the component sensed by the Hall element 42 reduces the deviation from the ideal curve I as shown in FIG.
[0023]
Further, in the displacement sensor 10, since the closing plate 32 is provided at the end of the magnetic body 30 on the thicker side in the radial direction, the moving direction in the magnetic flux density direction near the closing plate side end of the magnetic body 30. The inclination with respect to α becomes small. Thus, when the Hall IC 40 is located near the end of the magnetic body 30 on the closing plate side, the moving direction component of the magnetic flux density sensed by the Hall element 42 increases, and the detection sensitivity of the Hall element 42 improves. Therefore, the deviation of the voltage value V from the ideal curve I is reduced as shown in FIG.
[0024]
Moreover, in the displacement sensor, the IC sensor 40 moves relative to the magnetic body 30 on the central axis O of the cylindrical hole 34, that is, on one axis of the moving direction α. Thereby, even if the IC sensor 40 rotates relative to the magnetic body 30 around the axis in the movement direction α, the fluctuation of the voltage value V can be sufficiently suppressed.
[0025]
As described above, according to the displacement amount sensor 10, the voltage value V showing linearity with respect to the displacement amount X can be detected in a wide use area as shown in FIG. 3, so that the detection accuracy is improved and the sensor 10 is downsized. And can be achieved. Note that the length of the movement direction α of the use area is set to be 0.65M when the length of the movement direction α of the permanent magnet 31 is M, for example.
[0026]
Here, an example of setting the dimensions of the straight portion 36 and the cylindrical hole 34 in the displacement sensor 10 will be described. When the length of the straight portion 36 in the moving direction α is L, the diameter of the cylindrical hole 34 is φ, and the ratio of the deviation of the voltage value V from the ideal curve I is output linearity, the dimensional ratio L / φ The output linearity shows a correlation as shown in FIG. From this correlation, when the dimension ratio L / φ satisfies 0.20 ≦ L / φ ≦ 0.27, the output linearity becomes 2% or less, and high linearity can be maintained between the displacement X and the voltage value V. You can see that. That is, the displacement amount X can be detected with higher accuracy by setting the length L and the diameter φ so as to satisfy 0.20 ≦ L / φ ≦ 0.27.
In addition, the length L of the straight portion 36 and the diameter φ of the cylindrical hole 34 can be appropriately set to a value at which desired characteristics can be obtained in each sensor according to the specifications of the displacement amount sensor, in addition to the above-described setting examples.
[0027]
(Second, third and fourth embodiments)
Main parts of the displacement sensor according to the second, third, and fourth embodiments of the present invention are shown in FIGS. Components substantially the same as those in the first embodiment are denoted by the same reference numerals.
In the displacement sensor of the second embodiment, a magnetic body 50 without the closing plate 32 is used as shown in FIG. 5 instead of the magnetic body 30 of the first embodiment.
[0028]
In the displacement sensor according to the third embodiment shown in FIG. 6, as shown in FIG. 6, the generatrix of the outer peripheral surface 35b of the changing portion 38 extends in a curved shape concave inward in the radial direction. The rate of change of the height decreases as the straight portion 36 is approached. On the other hand, in the displacement sensor according to the fourth embodiment, as shown in FIG. 7, the generatrix of the outer peripheral surface 35b of the changing portion 38 extends in a curved shape bulging outward in the radial direction, and the thickness of the changing portion 38 in the radial direction is reduced. The change rate increases as approaching the straight portion 36.
[0029]
The linearity of the voltage value V with respect to the displacement X by employing any one of the displacement sensors of the second, third, and fourth embodiments and the displacement sensor 10 of the first embodiment described above. The deviation from the ideal curve I can be adjusted.
[0030]
(Fifth embodiment)
8 to 10 show a displacement sensor according to a fifth embodiment of the present invention. Components substantially the same as those in the first embodiment are denoted by the same reference numerals.
In the displacement sensor 60 of the fifth embodiment, a plate-shaped magnetic body 62 is used instead of the cylindrical magnetic body 30 of the first embodiment.
[0031]
The magnetic body 62 is a permanent magnet made of a ferromagnetic material. The magnetic body 62 is fixed to the inner wall at the bottom of the housing 21 and protrudes in a plate shape toward the bottom of the housing 11. The magnetic body 62 has side surfaces 63 and 64 of the magnetic body 62 which are opposite to each other in a direction (orthogonal direction) β orthogonal to the axis of the movement direction α. The side surface 63 facing the columnar convex portion 12 and the Hall IC 40 in the orthogonal direction β is a flat surface extending along the movement direction α. The Hall IC 40 moves relative to the magnetic body 62 on an axis P parallel to the side surface 63. Here, the axis P passes through the center of the detection surface of the Hall element 42 almost perpendicularly. Therefore, the distance in the orthogonal direction β from the center of the detection surface of the Hall element 42 to the side surface 63 is kept substantially constant irrespective of the relative movement of the Hall IC 40. Magnetic poles N and S different from each other are formed at the protruding side distal end portion 62a and the proximal end portion 62b of the magnetic body 62. Accordingly, an annular magnetic flux passing through the magnetic body 62 and the axis P side of the side surface 63 is generated as indicated by an arrow in FIG. 9B. Note that an S pole may be formed at the end 62a and an N pole may be formed at the end 62b to generate a magnetic flux in a direction opposite to that in FIG. 9B. In the present embodiment, the Hall element 42 senses the moving direction component of the magnetic flux density around the side surface 63 at a position corresponding to the relative displacement of the Hall IC 40 with respect to the magnetic body 62.
[0032]
The magnetic body 62 has a straight portion 66 that makes the distance between the side surfaces 63 and 64 substantially constant, and a changing portion 68 that changes the distance between the side surfaces 63 and 64. In the magnetic body 62, the straight part 66 is provided at the tip part 62a. The side surface 64a of the straight portion 66 is a flat surface whose distance in the orthogonal direction β from the side surface 63 does not substantially change along the movement direction α. Thereby, the thickness of the straight portion 66 in the orthogonal direction β is kept substantially constant along the moving direction α. On the other hand, the change portion 68 of the magnetic body 62 is provided on the base end portion 62b side adjacent to the straight portion 66. The side surface 64b of the change portion 68 is a flat surface in which the distance in the orthogonal direction from the side surface 63 decreases from the base end portion 62b toward the straight portion 66 in the movement direction α. As a result, the thickness of the changing portion 68 in the orthogonal direction β decreases as it approaches the straight portion 66 in the moving direction α, and the rate of change of the thickness is substantially constant over the entire area in the moving direction α. Note that the thickness of the changing portion 68 in the orthogonal direction β at the boundary with the straight portion 66, that is, the minimum thickness of the changing portion 68 in the orthogonal direction β, matches the thickness of the straight portion 66 in the orthogonal direction β. As shown in FIG. 10, the thickness of the straight portion 66 and the thickness of the changing portion 68 in the direction γ perpendicular to the axes of the directions α and β are the same as each other and the detection surface width W of the Hall element 42 in the direction γ. Has been thicker than.
[0033]
Assuming that the relative displacement of the Hall IC 40, that is, the displacement of the shaft 100, with respect to the end surface position of the tip end portion 62a of the magnetic body 62 in the moving direction α is X, and the voltage value of the detection signal of the Hall IC 40 is V, the displacement X Has a linearity similar to that of the first embodiment. This is because, since the straight portion 66 is provided at the end 62a of the magnetic body 62 on the side where the thickness in the orthogonal direction β is thin, the moving direction of the magnetic flux density sensed by the Hall element 42 near the end 62a. This is because the components increase and the detection sensitivity of the Hall element 42 improves.
[0034]
(Sixth and seventh embodiments)
FIGS. 11 and 12 show a main part of a displacement sensor according to a sixth embodiment and a seventh embodiment of the present invention, respectively. Components substantially the same as those in the fifth embodiment are denoted by the same reference numerals.
In the displacement sensor according to the sixth embodiment, as shown in FIG. 11, the side surface 64 b of the change portion 68 is a curved surface that is concave toward the side surface 63, and the change rate of the change portion 38 in the orthogonal direction β is It decreases as it approaches. On the other hand, in the displacement amount sensor according to the seventh embodiment, as shown in FIG. 12, the side surface 64b of the changing portion 68 is a curved surface bulging toward the side opposite to the side surface 63, and the rate of change of the changing portion 38 in the orthogonal direction β. Increases as approaching the straight portion 66.
[0035]
By adopting any one of the displacement amount sensors of the sixth and seventh embodiments and the displacement amount sensor 60 of the fifth embodiment described above, the ideal curve I for the linearity of the voltage value V with respect to the displacement amount X is obtained. Can be adjusted.
[0036]
(Eighth and ninth embodiments)
FIGS. 13 and 14 show the main parts of a displacement sensor according to an eighth embodiment and a ninth embodiment of the present invention, respectively. Components substantially the same as those in the fifth embodiment are denoted by the same reference numerals.
In the displacement sensor according to the eighth embodiment, four magnetic bodies 62 according to the fifth embodiment are used as shown in FIG. The magnetic bodies 62 are arranged at equal intervals around an axis P passing through the center of the detection surface of the Hall element 42. As a result, the density of the magnetic flux passing through the Hall element 42 is increased as compared with the case where the number of the magnetic members 62 is one. Therefore, the detection sensitivity of the Hall IC 40 is improved.
[0037]
In the displacement sensor of the ninth embodiment, a connecting plate 70 as shown in FIG. 14 is used in addition to the configuration of the eighth embodiment. The connecting plate 70 is formed of a magnetic material in a thin plate shape, and is joined to the base end 62b of each magnetic body 62 with an adhesive or the like. As a result, the base ends 62b of the magnetic members 62 are connected to each other by the connecting plate 70 and are magnetically connected, and pass through the connecting plate 70, the magnetic members 62, and the side surfaces 63 of the magnetic members 63 along the axis P. Thus, an annular magnetic flux is generated. In such a displacement amount sensor, when the Hall IC 40 is located near the base end portion 62b of the magnetic body 62, the moving direction component of the magnetic flux density sensed by the Hall element 42 is increased by the connecting plate 70, and the voltage value V The deviation from the ideal curve I is reduced. Therefore, the detection accuracy of the displacement amount X is further improved, and the use area of the displacement amount sensor is expanded.
[0038]
In the eighth and ninth embodiments, the four magnetic bodies 62 having the shape of the sixth or seventh embodiment may be used. The number of magnetic bodies 62 arranged around the axis P can be appropriately set to a number other than four. Further, the arrangement interval of each magnetic body 62 may be changed for each magnetic body 62 in addition to the equal interval. Further, the connecting plate 70 of the ninth embodiment may be integrally formed of the same ferromagnetic material as the magnetic body 62.
[0039]
In the embodiments described above, the magnetic bodies 30, 50, and 62 move linearly together with the shaft 100 as the moving body, and the Hall IC 40 as the magnetic detecting element is fixed. On the other hand, the magnetic detection element may be linearly moved together with the moving body to fix the magnetic body.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view illustrating a main part of a displacement sensor according to a first embodiment, and FIG. 1B is a schematic diagram illustrating a magnetic flux generated in the displacement sensor.
FIG. 2 is a sectional view showing a displacement sensor according to the first embodiment.
FIG. 3A is a schematic diagram illustrating the direction and magnitude of a magnetic flux density in the displacement sensor according to the first embodiment, and the displacement of a moving body and the output voltage value of an IC sensor in the displacement sensor according to the first embodiment. FIG. 4B is a characteristic diagram (b) showing a correlation with the above.
FIG. 4 is a characteristic diagram showing a correlation between a dimensional ratio and output linearity of a use area in the displacement sensor according to the first embodiment.
FIG. 5 is a sectional view showing a main part of a displacement sensor according to a second embodiment.
FIG. 6 is a sectional view showing a main part of a displacement sensor according to a third embodiment.
FIG. 7 is a sectional view showing a main part of a displacement sensor according to a fourth embodiment.
FIG. 8 is a sectional view showing a displacement sensor according to a fifth embodiment.
9A is a cross-sectional view illustrating a main part of a displacement sensor according to a fifth embodiment, and FIG. 9B is a schematic diagram illustrating a magnetic flux generated in the displacement sensor.
FIG. 10 is a view in the direction of the arrow X in FIG. 9A.
FIG. 11 is a sectional view showing a main part of a displacement sensor according to a sixth embodiment.
FIG. 12 is a sectional view showing a main part of a displacement sensor according to a seventh embodiment.
13A is a cross-sectional view showing a main part of a displacement sensor according to an eighth embodiment, and FIG.
FIG. 14 is a sectional view showing a main part of a displacement sensor according to a ninth embodiment.
FIG. 15A is a schematic diagram showing the direction and magnitude of a magnetic flux density in a conventional displacement sensor, and FIG. 15A is a graph showing the correlation between the displacement of a moving body and the detection value of a magnetic detection element in the conventional displacement sensor. It is a characteristic view (b) shown.
[Explanation of symbols]
10,60 displacement sensor
11 Housing
12 columnar projection
20 movable members
30,50,62 Magnetic material
31 permanent magnet
31a Open end
31b Closed end
32 Blocking plate (blocking part)
34 cylinder hole
36 straight section
38 Changing part
40 Hall IC (magnetic detection element)
42 Hall element
43 processing circuit
62a Tip
62b proximal end
63 sides
66 straight section
68 Change
70 Connecting plate (magnetic material)
100 shaft (moving body)

Claims (7)

A displacement sensor that includes a magnetic body and a magnetic detection element, and detects a displacement amount of a moving body that linearly moves together with one of the magnetic body and the magnetic detection element,
The cylindrical magnetic body has different magnetic poles formed at both ends in the moving direction in which the moving body moves linearly, and the magnetic detecting element can be relatively moved in a cylindrical hole extending at a constant diameter along the moving direction. And housed in
A straight portion provided at an end of the magnetic body where the cylindrical hole is opened, and a radial portion having a constant thickness in the moving direction is provided adjacent to the straight portion, and the straight portion is provided in the moving direction. The magnetic body has a changing portion in which the thickness in the radial direction decreases as approaching the straight portion,
A displacement sensor for detecting the displacement based on a magnetic flux density in the cylindrical hole detected by the magnetic detection element. 2. The magnetic body according to claim 1, wherein the magnetic body has a closing portion that is provided adjacent to the changing portion at an end opposite to the end where the straight portion is provided, and closes the cylindrical hole. 3. Displacement sensor. The displacement sensor according to claim 1, wherein the magnetic detection element moves relative to the magnetic body on a center axis of the cylindrical hole. When the length of the straight portion in the moving direction is L, and the diameter of the cylindrical hole is φ,
4. The displacement sensor according to claim 3, wherein the dimension ratio L / φ satisfies 0.20 ≦ L / φ ≦ 0.27. A displacement sensor that includes a magnetic body and a magnetic detection element, and detects a displacement amount of a moving body that linearly moves together with one of the magnetic body and the magnetic detection element,
The magnetic body has different magnetic poles at both ends in the moving direction in which the moving body moves linearly, and a side surface extending along the moving direction with respect to the magnetic detecting element moving relatively is orthogonal to the axis in the moving direction. Face each other in the orthogonal direction
A straight portion provided at an end of the magnetic body, the thickness of which in the orthogonal direction is constant along the moving direction, and a straight portion is provided adjacent to the straight portion, as the straight portion approaches the straight portion in the moving direction. The magnetic body has a change portion in which the thickness in the orthogonal direction decreases,
A displacement sensor for detecting the displacement based on a magnetic flux density around the side surface detected by the magnetic detection element. The displacement sensor according to claim 5, wherein a plurality of the magnetic bodies are arranged around an axis in the movement direction passing through the magnetic detection element. 7. The displacement sensor according to claim 6, wherein the plurality of magnetic bodies are connected to each other by a magnetic material at ends opposite to an end where the straight portion is provided.

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