JPH0778538A - Hall effect type position sensor - Google Patents

Abstract

PURPOSE:To improve the precision of position detection by specifying the composition of three permanent magnets of a magnetic field generating part of a Hall effect type position sensor composed of the magnetic field generating part and a magnetic field detecting part. CONSTITUTION:A Hall effect type position sensor is composed of a magnetic field generating part and a magnetic field detecting part which slides relatively to the magnetic field generating part and has hole elements to detect the magnetic field from the magnetic field generating part. The magnetic field generating part is composed of a first permanent magnet 6 and a second and a third magnets 7, 8 which are shorter in the length than the first magnet 6 and are set in both sides of the magnet 6 along the sliding direction while being kept from the magnet 6 by the same distance. Further, the polarity of the second and the third permanent magnets 7, 8 are made to be opposite to the polarity of the first permanent magnet 6. Consequently, even in the case the operational distance between the magnetic field generating part and the magnetic field detecting part alters, the difference of detection positions in the sliding direction can be suppressed to low level and moreover operational distance can be set to be wide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generating section composed of a permanent magnet which constitutes an object to be detected, and a Hall element which slides relative to the magnetic field generating section and detects a magnetic field from the magnetic field generating section. Hall effect type position sensor composed of a magnetic field detecting section and a magnetic field generating section.

[0002]

2. Description of the Related Art Recently, a Hall effect type position sensor in which a permanent magnet and a Hall element are combined has been applied to various mechanical devices, electric / electronic devices, automation devices and the like. This Hall-effect type position sensor has a magnetic field generation unit that attaches a permanent magnet to an object whose position is to be detected, and at the same time detects a magnetic field composed of a Hall element so as to slide relative to these magnetic field generation units. When the magnetic field generation unit and the magnetic field detection unit come close to each other, the Hall element of the magnetic field detection unit detects the magnetic field from the magnetic field generation unit by the Hall effect and outputs an electric signal. Thus, the position of the object to be detected is detected.

As is well known for the Hall effect, as shown in FIG. 6, a Hall element composed of a semiconductor thin film 20 such as 1 nSb is used, and a current I is caused to flow in a certain direction of the semiconductor thin film 20. Is a phenomenon in which a Hall voltage Vh is generated in a direction orthogonal to both the current I and the magnetic field H when a magnetic field H is applied in a direction orthogonal to the direction of H. The Hall voltage Vh is proportional to the product of the current I and the magnetic field H. To do. Therefore, by applying a magnetic field deflection to the Hall element, it is possible to output the Hall voltage Vh, that is, an electric signal according to the magnitude of the magnetic field, and thereby detect the position of the object to be detected and detect the position at this position. It is possible to perform necessary control operations such as stopping the body. Hall effect type position sensor configured such a Hall element as a magnetic field detection unit, without having a mechanical contact such as a micro switch,
Since it has an advantage of high reliability because it operates in a non-contact manner with the object to be detected, it is widely applied.

As a conventional example of such a Hall effect type position sensor, for example, the structure disclosed in Japanese Utility Model Laid-Open No. 1-81837 is known. As shown in FIG. 7, this structure has two magnet parts 2 which are partially magnetized in different directions.
The magnetic field generating unit 24 is configured by the magnet 23 composed of 1 and 22, and the magnetic field generating unit 24 and the magnetic field detecting unit 25 including a Hall element are kept at an operating distance h so that the two 24 and 25 are relatively positioned. It is designed to be slid in the magnetic flux direction 26.

Further, as another conventional example, for example, an actual flatbed 1
The structure disclosed in Japanese Patent Laid-Open No. -100348 is known. In this structure, as shown in FIG. 8, a permanent magnet 32 is attached to a piston 31 as an object to be detected whose position is to be detected, and magnetic bodies 33 are attached to both ends of the permanent magnet 32 in the sliding direction. , Magnetic field generator 3
4 is configured. Then, the magnetic field detector 37 including the Hall element 36 is slid relative to the magnetic field generator 34 via the cylinder tube 35. In each of these conventional examples,
The Hall voltage Vh output from the Hall element is amplified by an amplifier and further compared with a reference value by a comparator to perform a switching operation, so that a control signal is output to the detected object. .

[0006]

By the way, the conventional Hall effect type position sensor has a problem that the displacement of the detection position in the sliding direction becomes large when the operating distance between the magnetic field generation unit and the magnetic field detection unit changes. For example, in the conventional example of FIG. 7, since a change in the operating distance h between the magnetic field generator 24 and the magnetic field detector 25 is practically unavoidable, this operating distance h
If the value changes, the detection position in the slide direction 26 shifts, so that the detection accuracy decreases.

The present invention has been made in consideration of the above problems, and is designed to suppress the deviation of the detection position in the sliding direction to be small even when the operating distance between the magnetic field generating section and the magnetic field detecting section changes. An object is to provide a Hall effect type position sensor.

[0008]

In order to achieve the above object, the present invention according to claim 1 provides a magnetic field generating section made of a permanent magnet which constitutes an object to be detected, and a slide relative to the magnetic field generating section. In the Hall-effect type position sensor including a magnetic field detection unit including a Hall element that detects a magnetic field from the magnetic field generation unit, the magnetic field generation unit includes a first permanent magnet and a slide of the first permanent magnet. A second permanent magnet and a third permanent magnet, which are smaller in length dimension than the first permanent magnet and are arranged with equal gaps on both sides along the direction, and are arranged with respect to the polarity of the first permanent magnet. The second and third permanent magnets are magnetized so that the polarities thereof are opposite to each other.

The present invention of claim 2 is based on claim 1 of the present invention.
It is characterized in that the first, second and third permanent magnets are integrally held.

According to a third aspect of the present invention, in any one of the first and second aspects, a predetermined bias voltage is applied to the output voltage of the Hall element which constitutes the magnetic field detecting section, and the output characteristic curve of the Hall element is substantially the same. It is characterized by being made vertical.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the first, second and third permanent magnets are housed in a non-magnetic case and integrally attached to a mounting plate. Is.

The present invention of claim 5 is the same as that of claim 4
The mounting plate is made of a ferromagnetic material.

According to the present invention of claim 6 in claim 4,
It is characterized in that a mark indicating the operating range is provided on the non-magnetic case.

The present invention of claim 7 is the same as that of claim 4
The mounting plate is provided with an elliptical mounting hole.

[0015]

According to the structure of the present invention as set forth in claim 1, the magnetic field generator is arranged with the first permanent magnet and the same gap on both sides along the sliding direction of the first permanent magnet. The second permanent magnet and the third permanent magnet each having a smaller length dimension than the first permanent magnet, and the polarities of the second and third permanent magnets are opposite to the polarities of the first permanent magnet. By magnetizing so that, even if the operating distance between the magnetic field generation unit and the magnetic field detection unit changes, the deviation of the detection position in the sliding direction can be suppressed to a small value.

According to the configuration of the present invention described in claim 2, by holding the first, second and third permanent magnets integrally, the same operation as in claim 1 can be performed.

According to the configuration of the present invention described in claim 3,
By applying a predetermined bias voltage to the output voltage of the Hall element that constitutes the magnetic field detection unit so that the output characteristic curve of the Hall element becomes substantially vertical, the same operation as in claim 1 can be performed. it can

According to the configuration of the present invention described in claim 4,
By accommodating the first, second, and third permanent magnets in the non-magnetic case and integrally mounting them on the mounting plate, the same operation as in claim 1 can be performed.

According to the configuration of the present invention described in claim 5,
Since the mounting plate is made of a ferromagnetic material, the same operation as in claim 1 can be performed.

According to the configuration of the present invention described in claim 6,
By providing the nonmagnetic case with the mark indicating the operating range, the same operation as in claim 1 can be performed.

According to the configuration of the present invention described in claim 7,
By providing the mounting plate with the elliptical mounting hole, the same operation as in claim 1 can be performed.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a Hall effect type position sensor of the present invention. Reference numeral 1 is a magnetic field generating section made of a permanent magnet that constitutes an object to be detected, and 2 is a magnetic flux relative to the magnetic field generating section 1. It is a magnetic field detection unit including a Hall element 5 that slides in the direction 3 and maintains the operating distance h to detect the magnetic field from the magnetic field generation unit 1. 4 is a magnetic field generator 2 as described later.
Is a bias voltage applied to the output voltage of the Hall element 5. As described above, the Hall element 5 that constitutes the magnetic field detection unit 2 uses a semiconductor thin film such as InSb.

2 to 4 show a specific structure of the magnetic field generator 1. FIG. 2 is a plan view, FIG. 3 is a sectional view taken along line AB of FIG. 2, and FIG. 4 is line CD of FIG. FIG. 6 is a first permanent magnet made of, for example, an anisotropic Ba ferrite magnet having a large coercive force, and 7, 8 are equal gaps D (see FIG. 5) on both sides of the first permanent magnet 6 in the sliding direction 3. Second and third permanent magnets, which are arranged apart from each other and have a smaller length dimension than the first permanent magnet and are made of the same material as that of the first permanent magnet 6. The polarities of 7 and 8 are magnetized so as to be opposite to the polarities of the first permanent magnet 6. As shown in FIG. 5, the length dimensions of the first, second, and third permanent magnets 6, 7, and 8 along the sliding direction 3 are L ₁ , L ₂ , and L ₃ , respectively, and the height dimension is Assuming that H is the width dimension in the direction perpendicular to the paper surface, L ₁ = 6 mm, L ₂ = L ₃ = 3 mm, H = 3 mm, W =
6mm and D = 3mm are set. FIG. 5 shows each permanent magnet 6,
Magnetic fluxes generated from 7 and 8 are shown by broken lines B1, B2, B3 ... And the characteristic curves of the Hall output (voltage) experimentally obtained by this magnetic field generation unit 1 are shown by solid lines C1, C2 and C.
3 ... An example is shown in which the magnetic field detection unit 2 is slid at a height position that maintains the operating distance h with respect to each of the permanent magnets 6, 7, and 8. The horizontal axis (x axis) indicates the slide direction, and the vertical axis (y axis) indicates the height direction.

Each of the permanent magnets 6, 7 and 8 is housed in a non-magnetic case 9 such as plastic and is integrally attached to a mounting plate 10 made of a non-magnetic material or a ferromagnetic material. The mounting plate 10 is provided with a positioning hole 11 in advance, and in the state where the projection 12 provided at the bottom of the non-magnetic case 9 is positioned in the hole 11, each permanent magnet 6,
7, 8 are integrated with the non-magnetic case 9 and the mounting plate 10 with an adhesive. Further, a groove 13 is provided on the upper surface of the non-magnetic case 9 as a mark indicating the switching operation range. The mounting plate 10 is preferably made of a ferromagnetic material such as mild steel due to its characteristics as described later. The mounting plate 10 is provided with an elliptical mounting hole 14 along the sliding direction,
The mounting plate 10 is fixed to the object to be detected by screwing the mounting screw 15 into the mounting hole 14. This fixed position can be adjusted by sliding it along the mounting hole 14.

In FIG. 5, solid lines C1, C2, C3 ...
The characteristic curves of the Hall output are 0 V, ± 0.1 V, and ± 0.2 V, and the magnetic fluxes of the broken lines B1, B2, B3 ... Are estimated from the characteristic curve group of the Hall output and plotted. Each characteristic curve and magnetic flux are shown symmetrically with the central portion CL of the first permanent magnet 6 as the center.
Since the Hall element 5 surface of the magnetic field detection unit 2 which is close to and above the permanent magnets 6, 7 and 8 with the operating distance h being held perpendicularly to the y axis, it is proportional to the magnetic flux density B in the vertical direction. The obtained hall output can be obtained. The magnetic flux density B in the vertical direction must be 0 on the characteristic curve of Hall output 0V. The broken lines B1, B2, B3 ... Denoting the magnetic flux are plotted so as to be almost the same. The magnetic flux also exists in the downward direction of the x axis, but is omitted.

When the magnetic field detection unit 2 is slid while keeping the operating distance h, if the magnetic field detection unit 2 is on the far left side of the origin of x = 0, the vertical magnetic flux density B is 0. Becomes 0V. Sliding magnetic field detecting portion 2 to the right, respectively -0.2V at each point _{P 1, P 2, P 3} , P 4, P 5, -0.1V, 0V, 0.1V, 0.2V
Generates the hall output of. Further, by sliding to the right, respectively at each point _{Q 1, Q 2, Q 3} , Q 4, Q 5 0.2
Hall output of V, 0.1V, 0V, -0.1V, -0.2V is generated. A Hall output of 0.2 V or higher is generated between P ₅ and Q ₁ and reaches a maximum of 0.3 V and saturates.

Here, as a practical use method, a method in which the Hall output performs a switching operation at 0 V must be avoided because the operation becomes unstable. This is to prevent the switching operation because the Hall output is 0 even when the magnetic field detection unit 2 is on the far left side of the y-axis, so that the switching operation is prevented. Therefore, in this embodiment, as shown in FIG. 1, when the bias voltage 4 is applied to the Hall element 5 and the sum of the bias voltage and the Hall output becomes 0, the switching operation is performed. Is aimed at. As a specific example, as the bias voltage −
Assuming that 0.05V is applied to the Hall output, the V curves of the solid lines C3 and C6 in FIG. 5 are -0.5V curves, and the -0.1V curves of the solid lines C2 and C7 are -0.15V.
It becomes a curve. In this way, the output of all the curves is shifted by -0.05V. Therefore, the broken lines C10 and C20
The 0.05V curve of is a 0V curve.

The operation with the bias voltage applied is as follows. That is, when the magnetic field detector 2 is on the far left side of the y-axis, the Hall output is 0V.
When a bias voltage of -0.05V is applied to, the total output becomes -0.05V. Next, the magnetic field detector 2
Slides to the point P ₁ , the total output in this case becomes -0.25V by applying -0.05V to -0.2V of C1. Similarly, the total output is -0.15V when the slide at _two points P, the total output when the slide _three points P becomes -0.05 V, by a point of intersection between 0.05V curve of broken line C10 For the first time, the total output becomes 0 V, the switching operation is performed, and the control signal is output. Slide the magnetic field detector 2 to the right side, and pass the points Q ₁ and Q ₂ to the broken line C20.
Until the crossing point of is exceeded, all outputs are positive and the switching operation is maintained. Then slide to the right to Q ₃ ,
When Q _4, Q reached ₅ points, the total output is negative, the switching operation is canceled.

As a result, as long as the magnetic field generator 2 slides within the range of the broken lines C10 and C20, the switching operation is maintained, so that a wide switching operation width can be secured. By thus ensuring a wide switching operation width, a reliable operation as a position sensor can be enabled, and the detected object can be stopped at a predetermined position. In this respect, when the switching operation width is narrow, a fatal inconvenience may occur in that a load having a large inertia causes a jump. Further, since the 0.05V curves of the broken lines C10 and C20 can be made into a shape close to an ideal that is almost vertical, even if the magnetic field detection unit 2 changes in the y-axis direction, that is,
Even when the operating distance h between the magnetic field generation unit 1 and the magnetic field detection unit 2 changes, it is possible to suppress the deviation of the detection position in the slide direction to be small, and thus it is possible to improve the detection accuracy. As a result, the operating distance h can be increased. In this respect, when the permanent magnets forming the magnetic field generating unit are closely adhered to each other without providing a gap as in the conventional case, the 0V curve is largely inclined to the outside, so it is assumed that an appropriate bias voltage is applied. However, since it is difficult to make the 0V curve into an ideal shape close to vertical, the operating distance h cannot be set large.

The reason why the 0V curve can be idealized in this way is that the 0V curve of the solid lines C3 and C6 in FIG. 5 is slightly inclined to the outside. And that the length dimensions L ₂ and L ₃ of the third permanent magnets 7 and 8 are set to be smaller than the length dimension L ₁ of the first permanent magnet 6 and that the gap D is provided. ing. In the present embodiment, when the current directions of the Hall elements 5 of the magnetic field detector 2 are reversed, the signs of the characteristic curves are all reversed. Further, in this case, +0.05 V is applied as the bias voltage. As a result, the total output output in the switching operation range between the solid lines C10 and C20 becomes negative.

By accommodating the permanent magnets 6, 7, and 8 in the non-magnetic case 9 as in the present embodiment, the amount of iron powder adsorbed from the surroundings can be reduced. Even if it is adsorbed, its removal is easy. Also, the mounting plate 1
When a ferromagnetic material such as mild steel is used as 0, the magnetomotive force of the permanent magnet is hardly consumed in the mild steel, and the total magnetomotive force acts on the upper surface of the permanent magnet, so that the working distance h can be increased. . Further, although the mounting plate 10 is often mounted on a steel material, the use of mild steel can reduce the change in the magnetic field due to mounting.

Since there are many methods for applying a bias voltage to the output of the Hall element and there is no need to explain it in particular, description thereof will be omitted.

[0033]

As described above, according to the present invention, the magnetic field generator is arranged with the first permanent magnet and the same gap on both sides along the sliding direction of the first permanent magnet. , And second and third permanent magnets having a smaller length dimension than the first permanent magnet, wherein the polarities of the second and third permanent magnets are opposite to the polarities of the first permanent magnet. Since the magnets are magnetized so that even if the operating distance between the magnetic field generating unit and the magnetic field detecting unit changes, the deviation of the detection position in the sliding direction can be suppressed to a small value, and the operating distance can be increased further. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a Hall effect type position sensor of the present invention.

FIG. 2 is a plan view showing the configuration of a magnetic field generation unit of the Hall effect type position sensor of the present embodiment.

3 is a cross-sectional view taken along the line AB of FIG.

FIG. 4 is a sectional view taken along the line C-D in FIG.

FIG. 5 is a characteristic diagram of Hall output obtained by the Hall effect type position sensor of the present embodiment.

FIG. 6 is a schematic diagram illustrating a Hall effect.

FIG. 7 is a schematic view showing a conventional Hall effect type position sensor.

FIG. 8 is a schematic view showing a conventional Hall effect type position sensor.

[Explanation of symbols]

 1 magnetic field generation unit 2 magnetic field detection unit 3 sliding direction 4 bias voltage 5 Hall element 6 first permanent magnet 7 second permanent magnet 8 third permanent magnet 9 non-magnetic case 10 mounting plate 14 mounting hole

Claims (7)

[Claims] 1. A magnetic field generation unit composed of a permanent magnet that constitutes an object to be detected, and a magnetic field detection unit composed of a Hall element that slides relative to the magnetic field generation unit and detects a magnetic field from the magnetic field generation unit. In the Hall-effect type position sensor having the above structure, the magnetic field generating unit includes a first permanent magnet and a first permanent magnet arranged at equal gaps on both sides along the sliding direction of the first permanent magnet. A second permanent magnet and a third permanent magnet having a length smaller than that of the magnet,
2. A Hall effect type position sensor, wherein the second and third permanent magnets are magnetized so that the polarities thereof are opposite to the polarities of the permanent magnets. 2. The Hall effect type position sensor according to claim 1, wherein the first, second and third permanent magnets are integrally held. 3. The output characteristic curve of the hall element is made substantially vertical by applying a predetermined bias voltage to the output voltage of the hall element which constitutes the magnetic field detecting section. Hall effect type position sensor according to any one of 1. 4. The Hall effect type position sensor according to claim 1, wherein the first, second and third permanent magnets are housed in a non-magnetic case and integrally mounted on a mounting plate. 5. The Hall effect type position sensor according to claim 4, wherein the mounting plate is made of a ferromagnetic material. 6. The Hall effect type position sensor according to claim 4, wherein a mark indicating the operating range is provided on the non-magnetic case. 7. The Hall effect type position sensor according to claim 4, wherein the mounting plate is provided with an elliptical mounting hole.