Magnetic sensor device

Abstract

To provide a magnetic sensor device which can highly accurately detect proximate state of a detection-target.SOLUTION: A magnetic sensor device is provided, detecting a proximate state of a magnet 100 which is a detection-target by detecting a change of magnetic flux applied from the magnet 100, the magnetic sensor device comprises: a magnetic sensor element 10; and a bias magnet 20 which is disposed at a position opposed to the magnet 100 with the magnetic sensor element 10 interposed between the bias magnet 20 and the magnet 100. In a magnetic sensor device 1, the magnetic sensor element 10 detects the proximate state of the magnet 100 when magnetic flux applied from the bias magnet 20 to the magnetic sensor element 10 is balanced with magnetic flux applied from the magnet 100 to the magnetic sensor element 10 and an output voltage becomes zero, the bias magnet 20 has the same temperature characteristics as the magnet 100, and a magnetic pole in the bias magnet 20 at the side of the magnetic sensor element 10 is the same magnetic pole as a magnetic pole in the magnet 100 at the side of the magnetic sensor element 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a magnetic sensor device.

Background Art

[0002] Conventionally, a magnetic sensor device that detects the proximity state of a detected object by detecting a change in the magnetic flux (magnetic flux density) applied from the detected object is known.

[0003] For example, Patent Document 1 describes a magnetic sensor device including a bias magnet and a magnetic sensor element that detects a change in the magnetic flux applied from the bias magnet. In Patent Document 1, the detected object is a magnetic material, and by magnetizing the detected object with a bias magnet, a change in the applied magnetic flux generated by the bias magnet is detected by the magnetic sensor element.

[0004] Also, a magnetic sensor device that detects the proximity state of a detected object by using a magnet instead of a magnetic material and detecting a change in the magnetic flux applied from the magnet is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in recent years, there has been a demand for a magnetic sensor device capable of detecting the proximity state of a detected object with high accuracy in the field of magnetic sensor devices.

[0007] However, since the magnetic flux applied to the magnetic sensor element changes depending on the shape, position, temperature characteristics, distance, direction, etc. of the magnet which is the object to be detected, there is a problem that the variation in the "on position" where the magnetic sensor element detects the approach of the object to be detected becomes large, and it is difficult to detect the proximity state of the object to be detected with high accuracy.

[0008] Hereinafter, a specific explanation will be given. FIG. 6 is a graph showing the relationship between the magnetic field (magnetic flux density B) applied to the magnetic sensor element and the output voltage V of the magnetic sensor element. In a conventional magnetic sensor device, in order to generate an output voltage V corresponding to the applied magnetic field H, when the output voltage V is monitored and reaches a predetermined threshold voltage Vth, it is detected that a predetermined magnetic field has been applied, and the proximity state of the object to be detected is detected (see FIG. 6). However, since there are variations in the slopes of the magnetic field H and the output voltage V applied to the magnetic sensor device depending on the temperature (see the broken line and arrow in FIG. 6), in a conventional magnetic sensor device where the output voltage V is the predetermined threshold voltage Vth (with output), there are variations in the applied magnetic field (magnetic flux density B) with respect to the output voltage V, and there is a problem that it is difficult to detect the proximity state of the object to be detected with high accuracy.

[0009] Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to provide a magnetic sensor device capable of detecting the proximity state of an object to be detected with high accuracy.

[0010] As a result of research by the inventors of the present invention on these problems, it has been found that due to the difference in the temperature characteristics of the magnet and the bias magnet, the variation in the "on position" and the variation in the relationship between the output voltage and the applied magnetic field become large. The present invention has been found based on this finding.

Means for Solving the Problems

[0011] The magnetic sensor device of the present invention is a magnetic sensor device that detects the proximity state of a magnet by detecting a change in magnetic flux applied from the magnet as a detection object, and includes a magnetic sensor element and a bias magnet disposed at a position facing the magnet with the magnetic sensor element interposed therebetween. The magnetic sensor element detects the proximity state of the magnet when the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element are balanced and the output voltage becomes zero. The bias magnet has the same temperature characteristics as the magnet, and the pole on the magnetic sensor element side of the bias magnet is the same pole as the pole on the magnetic sensor element side of the magnet.

Effect of the Invention

[0012] According to the magnetic sensor device of the present invention, since the bias magnet has the same temperature characteristics as the magnet, when the temperature rises and the magnetic field of the bias magnet changes, the magnetic field of the magnet also changes with the same characteristics. Therefore, the change amount of the magnetic flux of the magnet due to temperature change and the change amount of the magnetic flux of the bias magnet due to temperature change cancel each other out in the magnetic sensor element, and the output voltage of the magnetic sensor element is hardly affected by temperature change. Therefore, the change in the magnetic flux (magnetic flux density) applied to the magnetic sensor element becomes small, and the variation in the "on position" detected by the magnetic sensor element when the magnet (detection object) approaches becomes small, so that it is possible to detect the proximity state of the magnet (detection object) with high accuracy.

[0013] Further, according to the magnetic sensor device of the present invention, since the magnetic sensor element detects the proximity state of the magnet when the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element are balanced and the output voltage becomes zero, even if there is variation in the slope of the magnetic field H and the output voltage V applied to the magnetic sensor device due to temperature, the change in the threshold value due to differences in the temperature characteristics of the magnet (and the bias magnet) can be reduced (see the vicinity of the origin A in FIG. 6), and it is difficult for variation to occur in the applied magnetic field with respect to the output voltage. Therefore, it is possible to detect the proximity state of the magnet (detection object) with high accuracy.

[0014] Further, according to the magnetic sensor device of the present invention, since the magnetic pole on the magnetic sensor element side of the bias magnet is the same magnetic pole as the magnetic pole on the magnetic sensor element side of the magnet, the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element are balanced, and when the output voltage becomes zero, it is possible to realize a configuration for detecting the proximity state of the magnet.

[0015] By the way, when setting the operating point at the output level of the output voltage, the operating point changes due to the temperature change of the potential gradient of the sensor (magnetic sensor element) and the change in the temperature characteristics of the magnet. On the other hand, according to the magnetic sensor device of the present invention, the magnetic sensor element detects the proximity state of the magnet when the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element are balanced and the output voltage becomes zero (at the operating point at the zero level). Therefore, the operating point does not change even due to the temperature change of the potential gradient of the sensor and the change in the temperature characteristics of the magnet. Accordingly, it is possible to reduce the variation in the slope of the magnetic flux density B applied to the magnetic sensor element and the output voltage V due to temperature. As a result, since it is difficult for variations in the detection of the proximity state of the magnet to occur, it is possible to reliably detect the proximity state of the magnet even when the operating region is set wide. In addition, the operating temperature range can be set wide.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiment for Carrying Out the Invention

[0017] Hereinafter, the magnetic sensor device of the present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below do not limit the invention according to the claims. Also, not all of the various elements and their combinations described in the embodiments are essential for the solution means of the present invention.

[0018] [Embodiment 1] 1. Configuration of the magnetic sensor device 1 according to Embodiment 1 FIG. 1 is a diagram showing the magnetic sensor device 1 according to Embodiment 1. As shown in FIG. 1, the magnetic sensor device 1 according to Embodiment 1 includes a magnetic sensor element 10, a bias magnet 20, a housing 30, and a zero-cross comparator 32, and is a magnetic sensor device that detects the proximity state of the magnet 100 by detecting a change in the magnetic flux applied from the magnet 100, which is the object to be detected.

[0019] The magnet 100, which is the object to be detected, is a permanent magnet made of an appropriate material. Examples of the type of the magnet 100 include a barium ferrite magnet, a neodymium magnet, a samarium cobalt magnet, an alnico magnet, a strontium ferrite magnet, and the like. At the magnetic pole of the magnet 100, the side of the magnetic sensor device 1 is the N pole, and the side opposite to the magnetic sensor device 1 is the S pole. Note that, as the object to be detected, a magnet may be attached to a non-magnetic substance to detect the proximity state of the object to be detected. Also, when the substance to which the magnet is attached is a ferromagnetic material, it is desirable to take measures such as separating the magnet from the substance, inserting a spacer, etc. so as not to be affected by the temperature characteristics of the magnet, or to closely adhere the ferromagnetic material to the magnet and also to the bias magnet to balance the temperature characteristics of the ferromagnetic material.

[0020] In the magnetic sensor device 1, the magnetic sensor element 10 and the bias magnet 20 are arranged inside the housing 30, and the magnetic sensor element 10 is arranged at the tip of the housing 30.

[0021] As the magnetic sensor element 10, a Hall element is used in Embodiment 1, but any appropriate sensor element can be used as long as it is a magnetic flux response type element. For example, appropriate sensor elements such as a TMR sensor element, an AMR sensor element, and a coil excitation type sensor element can be used.

[0022] In the magnetic sensor element 10, the magnetic flux in the direction perpendicular to the detection surfaces 12 and 14 is the detection direction. When the magnetic flux is applied from the detection surface 12 toward the detection surface 14, the output voltage becomes positive, and in the opposite case, it becomes negative. The detection surface 12 is arranged along the surface of the housing 30, and the detection surface 14 is the surface on the opposite side. The magnetic sensor element 10 and the bias magnet 20 are arranged such that the magnetic flux component applied from the bias magnet 20 cancels out the magnetic flux component applied from the magnet 100.

[0023] The magnetic sensor element 10 detects the proximity state of the magnet 100 when the magnetic flux applied from the bias magnet 20 to the magnetic sensor element 10 and the magnetic flux applied from the magnet 100 to the magnetic sensor element 10 are balanced and the output voltage becomes zero. That is, when the output voltage, which is normally output at a predetermined value by the magnetic flux applied by the bias magnet 20 to the magnetic sensor element 10, is canceled and decreased by the magnetic flux applied by the magnet 100 to the magnetic sensor element 10 and becomes zero, it is detected that the magnet 100 has approached.

[0024] The bias magnet 20 is disposed at a position facing the magnet 100, which is the object to be detected, with the magnetic sensor element 10 interposed therebetween. The bias magnet 20 is within the housing 30. The pole of the bias magnet 20 on the side of the magnetic sensor element 10 is the N pole, which is the same pole as the pole of the magnet 100 on the side of the magnetic sensor element 10. That is, the bias magnet 20 and the magnet 100 face each other with their N-pole sides facing each other across the magnetic sensor element 10. In this embodiment, the N poles face each other, but the S poles may face each other instead.

[0025] The bias magnet 20 is made of a material having the same temperature characteristics as the magnet 100. In Embodiment 1, the bias magnet 20 is made of the same material as the material of the magnet 100, but a plurality of types of magnets may be combined so that the bias magnet 20 and the magnet 100 have the same temperature characteristics.

[0026] In FIG. 1, reference sign a indicates the length (clearance) between the bias magnet 20 and the magnetic sensor element 10, and reference sign b indicates the length between the magnetic sensor element 10 and the magnet 100 in the on position. The length a and the length b vary depending on the shapes, magnetization strengths, sizes, etc. of the magnet 100 and the bias magnet 20, but are adjusted so that the magnetic flux applied to the magnetic sensor element 10 by the bias magnet 20 is equal to the magnetic flux applied to the magnetic sensor element 10 by the magnet 100. In Embodiment 1, the bias magnet 20 can be configured to be movable with a special jig.

[0027] Note that the operating point can be changed by changing the length between the bias magnet 20 and the magnetic sensor element 10 and / or the strength of the bias magnet.

[0028] The zero-cross comparator 32 compares the output voltage output from the magnetic sensor element 10 with the reference potential and outputs it to the outside of the magnetic sensor device 1.

[0029] FIG. 2 is a cross-sectional view showing the operating space in Embodiment 1. In Embodiment 1, when plotting the boundary of the operating space around the magnetic sensor device 1, it has a spatially (three-dimensionally) extended shape, and when viewed in a predetermined cross-section (for example, a cross-section along the central axis of the magnetic sensor element 10 and the operating space), it has a shape close to a circle or an ellipse as shown in FIG. 2. The position of the boundary of this operating space is called the on-position. The on-position does not change significantly due to temperature changes because the temperature characteristics of the magnet 100 and the bias magnet 20 are equal to each other.

[0030] Note that the "operating space" refers to a spatial (three-dimensional) region where it is detected that the magnet 100 approaches the magnetic sensor device 1 and comes into a proximity state. Although it is shown two-dimensionally in FIG. 2, actually, it extends spatially like a spherical shape, an oval shape, or a rugby ball shape. Also, the "on-position" refers to the position that becomes the boundary of the "operating space", and in Embodiment 1, it refers to the position when the output voltage of the magnetic sensor element 10 becomes zero.

[0031] FIG. 3 is a schematic graph showing the relationship between the distance b between the magnetic sensor element 10 and the magnet 100, the magnetic flux H applied to the magnetic sensor element 10, and the output voltage Vout in Embodiment 1. In FIG. 3, the case where the magnetic flux is applied in the direction from the detection surface 12 to the detection surface 14 is defined as positive, and the reverse is defined as negative.

[0032] Before the magnet 100 approaches the magnetic sensor device 1, a negative voltage is generated in the magnetic sensor element 10 by the magnetic flux applied by the bias magnet 20 (see the section indicated by reference sign A in FIG. 3). At this time, the output Vout of the zero-cross comparator 32 is Lo (see the lower graph in FIG. 3).

[0033] When a magnet 100 is brought close to the magnetic sensor device 1, the magnetic flux applied by the bias magnet 20 to the magnetic sensor element 10 is canceled out by the magnetic flux applied by the magnet 100 to the magnetic sensor element 10, and the absolute value of the magnetic flux becomes smaller (see the section indicated by reference sign B in FIG. 3). Even at this time, the output Vout of the zero-cross comparator 32 remains Lo (see the graph below FIG. 3).

[0034] When the magnet 100 is brought close to the boundary region (= on-position) of the predetermined operating space, the magnetic flux applied by the bias magnet 20 to the magnetic sensor element 10 is canceled out by the magnetic flux applied by the magnet 100 to the magnetic sensor element 10, and the voltage becomes zero (see the point of reference sign X in FIG. 3). At this time, the magnetic sensor device 1 detects that the magnet 100 is in the approaching state, and sets the output Vout of the zero-cross comparator 32 to Hi (output at the voltage value V1).

[0035] When the magnet 100 approaches within the boundary region of the predetermined operating space, the magnetic flux increases in the positive direction (see the section indicated by reference sign C in FIG. 3). At this time, the magnetic sensor device 1 maintains the state that the magnet 100 is approaching, and the output Vout of the zero-cross comparator 32 remains Hi (output at the voltage value V1).

[0036] 2. Effects of the magnetic sensor device 1 according to Embodiment 1 According to the magnetic sensor device 1 according to Embodiment 1, since the bias magnet 20 has the same temperature characteristics as the magnet 100, when the temperature rises and the magnetic field (magnetic flux density) of the bias magnet 20 changes, the magnetic field of the magnet 100 also changes with the same characteristics. Therefore, the change amount of the magnetic flux (magnetic flux density) of the magnet 100 due to the temperature change and the change amount of the magnetic flux of the bias magnet 20 due to the temperature change cancel each other out in the magnetic sensor element 10, and the output voltage of the magnetic sensor element 10 is hardly affected by the temperature change. Therefore, since the variation in the "on-position" where the magnetic sensor element 10 detects that the magnet 100 (the object to be detected) has approached becomes smaller, it becomes possible to detect the proximity state of the magnet 100 (the object to be detected) with high accuracy.

[0037] Incidentally, as can be seen from FIG. 6, the variation in the slope due to the temperature characteristics of the output voltage V of the magnetic sensor element 10 with respect to the magnetic flux density B applied to the magnetic sensor element 10 (see the arrow in FIG. 6) is smaller when the output of the magnetic flux density B applied to the magnetic sensor element 10 is closer to zero, as compared with the case where there is an output. Therefore, according to the magnetic sensor device 1 according to Embodiment 1, when the magnetic fluxes applied from the bias magnet 20 and the magnet 100 to the magnetic sensor element 10 are balanced and the output voltage becomes zero, the magnetic sensor element 10 detects the proximity state of the magnet 100. Thus, even if variations occur in the magnetic flux density B applied to the magnetic sensor element 10 and the slope of the output voltage V of the magnetic sensor element 10 due to temperature, it is possible to reduce the change in the threshold value due to differences such as the temperature characteristics of the magnet 100 (and the bias magnet 20) (see the vicinity of the origin A in FIG. 6), and it is difficult for variations to occur in the applied magnetic field with respect to the output voltage. Therefore, it is possible to detect the proximity state of the magnet 100 (the object to be detected) with high accuracy.

[0038] Further, according to the magnetic sensor device 1 according to Embodiment 1, since the pole on the magnetic sensor element 10 side of the bias magnet 20 is the same pole (both are N poles) as the pole on the magnetic sensor element 10 side of the magnet 100, the magnetic sensor element 10 can realize a configuration in which it detects the proximity state of the magnet 100 when the magnetic flux amount applied from the bias magnet 20 to the magnetic sensor element 10 and the magnetic flux amount applied from the magnet 100 to the magnetic sensor element 10 are balanced and the output voltage becomes zero.

[0039] By the way, when setting the operating point at the output level of the output voltage, the operating point changes due to the temperature change of the potential gradient of the sensor (magnetic sensor element) or the change in the temperature characteristics of the magnet. On the other hand, according to the magnetic sensor device 1 according to Embodiment 1, the magnetic sensor element 10 detects the proximity state of the magnet 100 when the magnetic flux applied from the bias magnet 20 to the magnetic sensor element 10 and the magnetic flux applied from the magnet 100 to the magnetic sensor element 10 are balanced and the output voltage becomes zero (at the operating point at the zero level). Therefore, the operating point does not change even due to the temperature change of the potential gradient of the sensor (magnetic sensor element) or the change in the temperature characteristics of the magnet 100. Therefore, the variation in the slope of the magnetic flux density B applied to the magnetic sensor element 10 and the output voltage V due to temperature can be reduced. As a result, since it is difficult for variations in the detection of the proximity state of the magnet 100 to occur, the proximity state of the magnet 100 can be reliably detected even when the operating range is set wide. Also, the operating temperature range can be set wide.

[0040] Further, according to the magnetic sensor device 1 according to Embodiment 1, since the bias magnet 20 is made of the same material as the magnet 100, it becomes a magnet having the same temperature characteristics. Therefore, it is difficult for a deviation in the on-position to occur due to a difference in temperature characteristics, and the proximity state of the magnet 100 (object to be detected) can be detected with high accuracy.

[0041] Further, according to the magnetic sensor device 1 according to Embodiment 1, the magnetic sensor element 10 and the bias magnet 20 are arranged in the housing 30, and since the magnetic sensor element 10 is arranged at the tip of the housing 30, the position of the bias magnet 20 can be fixed, and the proximity state of the magnet can be detected with higher accuracy. Also, since the magnetic sensor element 10 is arranged at the tip of the housing 30, it becomes a magnetic sensor device that is easy to handle.

[0042] [Embodiment 2] FIG. 4 is a diagram showing the magnetic sensor device 2 according to Embodiment 2. FIG. 4(a) shows a side view of the magnetic sensor device 2 (only the cross-sectional view of the bias magnet 20a), FIG. 4(b) shows a front view of the magnetic sensor device 2, FIG. 4(c) shows a front view of the bias magnet 20a, FIG. 4(d) shows a side cross-sectional view of the bias magnet 20a, FIG. 4(e) shows a side view showing the relationship between the magnet 102 and the magnetic sensor device 2 (only the cross-sectional view of the magnet 102 and the bias magnet 20a), FIG. 4(f) shows a front view of the magnet 102, and FIG. 4(g) shows a side cross-sectional view of the magnet 102.

[0043] The magnetic sensor device 2 according to Embodiment 2 basically has the same configuration as the magnetic sensor device 1 according to Embodiment 1, but the configuration of the bias magnet is different from that of the magnetic sensor device 1 according to Embodiment 1. The magnetic sensor device 2 according to Embodiment 2 includes, as shown in FIGS. 4(a) and 4(e), a magnetic sensor element 10, a main body portion 40, a bias magnet holding portion 22, and a zero-cross comparator (not shown).

[0044] The main body portion 40 has a cylindrical shape, and a magnetic sensor element 10 is disposed near the tip. A cable 60 extends from the side opposite to the side where the magnetic sensor element 10 is disposed. In addition, a male screw portion (not shown) is formed on the outer periphery of the main body portion 40. The male screw portion may be provided over the entire main body portion 40 or may be provided partially.

[0045] The bias magnet holding portion 22 has a ring shape with a through hole in the center and holds the bias magnet 20a. A female screw portion (not shown) is formed on the inner peripheral surface of the through hole. The female screw portion is connected by screwing with the male screw portion formed on the outer periphery of the main body portion 40. Then, the bias magnet holding portion 22 is attached to be movable along the main body portion 40 in the axial direction of the male screw portion (the direction perpendicular to the detection surface of the magnetic sensor element 10) by rotating the bias magnet holding portion 22.

[0046] The bias magnet holding portion 22 is provided with graduations at predetermined intervals along the circumferential direction of the outer peripheral surface, so that the rotational position can be easily grasped, and thus the distance between the magnetic sensor element 10 and the bias magnet 20a can be set.

[0047] The bias magnet holding portion 22 holds the bias magnet 20a. As shown in FIGS. 4(b) to 4(d), the bias magnet 20a has a ring shape with a diameter slightly larger than that of the main body portion and is disposed within the bias magnet holding portion 22. Similar to the case of Embodiment 1, the magnetic pole on the side of the magnet 102 is the N pole.

[0048] The magnet 102, which is the object to be detected, has a ring shape as shown in FIGS. 4(f) and 4(g), and has the same shape, the same temperature characteristics, and the same size as the bias magnet holding portion 22 (see FIGS. 4(e) and 4(g)). Also, similar to the case of Embodiment 1, the magnetic pole on the side of the magnetic sensor element 10 is the N pole. That is, the bias magnet 20a and the magnet 102 face each other with their N - pole sides sandwiching the magnetic sensor element 10.

[0049] Thus, although the configuration of the bias magnet of the magnetic sensor device 2 according to Embodiment 2 is different from that of the magnetic sensor device 1 according to Embodiment 1, when the temperature rises and the magnetic field (magnetic flux density) of the bias magnet 20a changes, similar to the case of the magnetic sensor device 1 according to Embodiment 1, the magnetic field (magnetic flux density) of the magnet 102 also changes with the same characteristics. Therefore, the change amount of the magnetic flux of the magnet 102 due to temperature change and the change amount of the magnetic flux of the bias magnet 20a due to temperature change cancel each other out in the magnetic sensor element 10, and the output voltage of the magnetic sensor element 10 is hardly affected by temperature change. Therefore, the change in the magnetic flux applied to the magnetic sensor element 10 becomes small, and the variation in the "on - position" where the magnetic sensor element 10 detects that the magnet 102 (object to be detected) has approached becomes small, so that it is possible to detect the proximity state of the magnet 102 (object to be detected) with high accuracy.

[0050] Further, according to the magnetic sensor device 2 according to Embodiment 2, the bias magnet holding portion 22 is attached to the main body portion 40 so as to be movable along the main body portion 40. Since the bias magnet 20a has the same shape as the magnet 102, when the bias magnet holding portion 22 is rotated to bring the bias magnet 20a closer to (or farther from) the magnetic sensor element 10, the "on position" for detecting the proximity of the magnet 102 moves by the same amount of variation according to the amount of variation. Therefore, it becomes a magnetic sensor element for which the position adjustment of the "on position" is easy.

[0051] Further, according to the magnetic sensor device 2 according to Embodiment 2, the main body portion 40 has a columnar portion extending toward the tip portion 42, and a male screw portion is formed on a part of the outer periphery of the portion. The bias magnet holding portion 22 has a ring shape with a through hole in the center, and a female screw portion is formed on the inner peripheral surface of the through hole. By screwing the female screw portion onto the male screw portion, the bias magnet holding portion 22 is connected to the male screw portion and is provided so as to be movable in the axial direction of the male screw portion. Therefore, the position of the bias magnet 20a can be easily changed only by rotating the bias magnet holding portion 22, and can be positioned with high accuracy. Therefore, it becomes a magnetic sensor device capable of setting a desired "operating space".

[0052] Note that the magnetic sensor device 2 according to Embodiment 2 has the same configuration as the magnetic sensor device 1 according to Embodiment 1 except for the configuration of the bias magnet, and thus has the corresponding effects among the effects of the magnetic sensor device 1 according to Embodiment 1.

[0053] [Embodiment 3] FIG. 5 is a diagram showing a magnetic sensor device 3 according to Embodiment 3. FIG. 5(a) shows a side view of the magnetic sensor device 3 (only a cross-sectional view of the bias magnet 20b), FIG. 5(b) shows a front view of the magnetic sensor device 3, FIG. 5(c) shows a front view of the bias magnet 20b, FIG. 4(d) shows a side view showing the relationship between the magnet 104 and the magnetic sensor device 3 (only a cross-sectional view of the magnet 104 and the bias magnet 20b), and FIG. 4(e) shows a front view of the magnet 104.

[0054] The magnetic sensor device 3 according to Embodiment 3 basically has the same configuration as the magnetic sensor device 2 according to Embodiment 2, but the configurations of the bias magnet and the main body part are different from those of the magnetic sensor device 2 according to Embodiment 2. As shown in FIGS. 5(a) and 5(d), the magnetic sensor device 3 according to Embodiment 3 includes a magnetic sensor element 10, a main body part 50, a bias magnet holding part 23, and a zero-cross comparator (not shown).

[0055] The main body part 50 has a cylindrical shape. The magnetic sensor element 10 is disposed near the tip of the main body part 50, and a cable 60 extends from the base end part side (the side opposite to the tip part). On the outer peripheral part of the main body part 50, scales indicating the distance from the magnetic sensor element 10 are provided at predetermined intervals along the axial direction of the main body part 50.

[0056] The bias magnet holding part 23 has a ring shape with a through hole in the center and holds the bias magnet 20b. The bias magnet holding part 23 is configured to be movable by sliding along the main body part 50. As a sliding mechanism, a rail may be provided on the main body part and the bias magnet holding part may be moved along the rail. Alternatively, a gripping part that grips the main body part by a negative force may be provided on the bias magnet holding part, and the bias magnet holding part may be moved along the main body part and gripped by the gripping part at a desired position. Or the bias magnet holding part may be slid along the main body part by other appropriate methods.

[0057] As shown in FIGS. 5(b) and 5(c), the bias magnet 20b has a semi-circular ring shape. The bias magnet 20b has the same shape, the same temperature characteristics, and the same size as the magnet 104.

[0058] The magnet 104 to be detected has a semi-circular ring shape and has the same shape, the same temperature characteristics, and the same size as the bias magnet holding part 23 (see FIGS. 5(d) and 5(e)). Also, similar to the case of Embodiment 1, the magnetic pole on the magnetic sensor element 10 side is the N pole. That is, the bias magnet 20b and the magnet 104 face each other with their N pole sides opposite to each other across the magnetic sensor element 10.

[0059] Thus, although the configurations of the bias magnet and the main body portion of the magnetic sensor device 3 according to Embodiment 3 are different from those of the magnetic sensor device 2 according to Embodiment 2, when the temperature rises and the magnetic field (magnetic flux density) of the bias magnet 20b changes, the magnetic field (magnetic flux density) of the magnet 104 also changes with the same characteristics as in the case of the magnetic sensor device 2 according to Embodiment 2. Therefore, the change amount of the magnetic flux of the magnet 104 due to temperature change and the change amount of the magnetic flux of the bias magnet 20b due to temperature change cancel each other out in the magnetic sensor element 10, and the output voltage of the magnetic sensor element 10 is hardly affected by temperature change. Therefore, the change in the magnetic flux applied to the magnetic sensor element 10 becomes small, and the variation in the "on position" where the magnetic sensor element 10 detects that the magnet 104 (object to be detected) has approached becomes small, so that it is possible to detect the proximity state of the magnet 104 (object to be detected) with high accuracy.

[0060] Further, according to the magnetic sensor device 3 according to Embodiment 3, since the bias magnet holding portion 23 is configured to be movable by sliding along the main body portion 50, the position of the bias magnet 20b can be relatively easily changed and can be positioned with high accuracy. Therefore, it becomes a magnetic sensor device capable of setting a desired on position.

[0061] Note that the magnetic sensor device 3 according to Embodiment 3 has the same configuration as the magnetic sensor device 2 according to Embodiment 2 except for the configurations of the bias magnet and the main body portion, and thus has the corresponding effects among the effects that the magnetic sensor device 2 according to Embodiment 2 has.

[0062] As described above, the present invention has been described based on the above embodiments, but the present invention is not limited to the above embodiments. It can be implemented in various aspects without departing from the gist thereof, and for example, the following modifications are also possible.

[0063] (1) The positions, connections, numbers, etc. described in the above embodiments (including each modification example; the same shall apply hereinafter) are illustrative, and can be changed within a range that does not impair the effects of the present invention.

[0064] (2) In the above embodiment, the proximity state of the magnet (detected object) was detected when the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element were balanced and the output voltage became zero. However, the present invention is not limited thereto. The proximity state of the detected object may be detected based on the output voltage corresponding to the difference between the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element. That is, even when the output voltage is other than zero, the proximity state of the magnet (detected object) may be detected based on the magnitude of the output voltage.

[0065] (3) In the above embodiment 2, a ring-shaped magnet and a bias magnet were used, and in the above embodiment 3, a semi-circular ring-shaped magnet and a bias magnet were used. However, the present invention is not limited thereto. In embodiments 2 and 3, it is sufficient if they have the same shape, temperature characteristics, and size as the magnet. In embodiment 2, a semi-circular ring-shaped magnet and a bias magnet may be used. In embodiment 3, a ring-shaped magnet and a bias magnet may be used. Either a 1 / 4 ring shape may be used, or arc-shaped magnets and bias magnets with other predetermined angles may be used. Also, magnets and bias magnets having a rectangular parallelepiped shape, a spherical shape, or other appropriate shapes may be used instead of the ring shape.

[0066] (4) In the above embodiment 3, a ring-shaped bias magnet holding portion was used. However, the present invention is not limited thereto. The bias magnet holding portion may slide along the main body portion. The bias magnet holding portion may be provided and slid only on one side of the outer periphery of the main body portion, or may be slid with other appropriate configurations.

Explanation of Reference Numerals

[0067] 1, 2… Magnetic sensor device, 10… Magnetic sensor element, 12, 14… Detection surfaces, 20, 20a, 20b… Bias magnets, 22, 23… Bias magnet holders, 30… Housing, 32… Zero-cross comparator, 40, 50… Main body parts, 60… Cable, 100, 102, 104… Magnets (objects to be detected)

Claims

1. A magnetic sensor device for detecting the proximity state of a magnet by detecting a change in magnetic flux applied from the magnet as the object to be detected, comprising: a magnetic sensor element; a bias magnet disposed at a position facing the magnet with the magnetic sensor element interposed therebetween, wherein the magnetic sensor element detects the proximity state of the magnet when the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element are in balance and the output voltage becomes zero, the bias magnet has the same temperature characteristics as the magnet, and a magnetic pole on the magnetic sensor element side of the bias magnet is the same magnetic pole as the magnetic pole on the magnetic sensor element side of the magnet.

2. The magnetic sensor device according to claim 1, wherein the bias magnet is made of the same material as the magnet.

3. The magnetic sensor element and the bias magnet are disposed in a housing, and the magnetic sensor element is disposed at the tip of the housing.

4. The magnetic sensor device further comprises a main body portion and a bias magnet holding portion, the magnetic sensor element is disposed at the tip of the main body portion, the bias magnet holding portion holds the bias magnet and is attached to the main body portion so as to be movable along the main body portion, and the bias magnet has the same shape as the magnet.

5. The main body portion has a columnar portion extending toward the tip, and a male screw portion is formed on a part of the outer periphery of the portion, the bias magnet holding portion has a ring shape with a through hole in the center, and a female screw portion is formed on the inner peripheral surface of the through hole, and by screwing the female screw portion onto the male screw portion, the bias magnet holding portion is connected to the male screw portion and is provided so as to be movable in the axial direction of the male screw portion.

6. The main body portion has a columnar portion extending toward the tip, and the bias magnet holding portion is configured to be movable by sliding along the main body portion.

7. A magnetic sensor device that detects the proximity state of the magnet by detecting a change in magnetic flux applied from the magnet as the object to be detected, a magnetic sensor element, and a bias magnet disposed at a position facing the object to be detected with the magnetic sensor element interposed therebetween, wherein the magnetic sensor element detects the proximity state of the object to be detected based on an output voltage corresponding to a difference between the magnetic flux applied from the bias magnet to the magnetic sensor element and the magnetic flux applied from the magnet to the magnetic sensor element, the bias magnet has the same temperature characteristics as the magnet, and a magnetic pole on the magnetic sensor element side of the bias magnet is the same magnetic pole as a magnetic pole on the magnetic sensor element side of the magnet. A magnetic sensor device characterized by this.

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