JP7202321B2 - Mounting structure of magnet for detection of electric actuator for valve and electric actuator for valve - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mounting structure of a detection magnet attached to an output shaft side of an electric valve actuator and to an electric valve actuator in order to detect a rotation state of the output shaft side of the electric valve actuator.

Conventionally, when an electric actuator is mounted on a rotary valve such as a ball valve, it is necessary to detect the rotational state of the output shaft side of the electric actuator in order to accurately control the rotation of the valve. For this reason, contact-type position detectors using microswitches and cams have often been used to detect the output shaft, or a control shaft that is coaxial with or separate from the output shaft. Problems include the need for time-consuming adjustment work, the possibility of contact failures and failures during use due to the contact type, and the increase in size of the actuator as a whole. For this reason, in recent years, non-contact type position detection devices have been used more and more. In this non-contact type, a general-purpose motor is used to ensure overall compactness, and the actuator as a whole is configured to provide a contact sensor. It is possible to control the rotation of the output shaft with high accuracy while solving the problem of the position detecting device of the mold. Among non-contact type position detectors, magnetic detectors using magnets are more popular than optical detectors because they are simpler, more environmentally resistant, more compact, and easier to fine-tune. Used a lot.

The present applicant has applied for Patent Document 1 as a technique related to an actuator using a magnetic position detection device using a magnet. In Document 1, a rotary encoder, which is a position detection device, is provided on the output shaft side, and the rotary encoder includes a permanent magnet magnet and a non-contact magnetic encoder IC for detecting the rotation angle of the magnet. I have. As a result, the rotational state of the output shaft is detected by measuring the rotational state of the magnet attached to the upper portion of the output shaft with the encoder IC.

The magnet is attached to the output shaft by this magnet attachment holder so as to be rotatable integrally with the output shaft. In this case, the holder is provided between the magnet and the output shaft, the magnet is attached to the upper part of the holder, and the upper end of the output shaft is fixed to the lower part of the holder. Mounted. As a result, when the output shaft rotates, the leakage magnetic flux of the magnet is accurately detected by the encoder IC.

At this time, since the encoder IC uses the leaked magnetic flux of the magnet to detect the rotation angle, the holder is made of a non-magnetic material other than a magnetic material that may short-circuit the magnetic flux, and is difficult to be charged. It must be constructed using a conductive material. In addition to these conditions, the holder is required to have high dimensional accuracy for coaxially mounting the output shaft and the magnet.
On the other hand, since the magnet requires a high leakage magnetic flux density, a neodymium magnet, which has a high magnetic flux density and is considered to be the strongest among permanent magnets, is usually used. Since neodymium magnets are very susceptible to rust, they are often nickel-plated to prevent rust.

JP 2019-196799 A

However, in the valve actuator of Patent Document 1, if the holder of the rotary encoder is made of a brass material, there is a demerit that it is expensive and cannot be manufactured easily. In addition, if the magnet is a neodymium magnet, electrical corrosion between different metals may occur between the brass holder and the surface of the magnet depending on the conditions, which may accelerate the oxidative deterioration of the neodymium magnet. be. Although it is conceivable to use a conductive resin material or an antistatic resin material for the magnet holder, it is not readily available and is expensive, which is disadvantageous in terms of cost.

On the other hand, it is considered effective to form the holder using a resin material as a non-magnetic material. In this case, the valve body and stem rotate while the magnet and output shaft are electrically insulated, and the generated electric charge is repeatedly transferred from the output shaft toward the magnet by electrostatic induction. . At this time, if the holder is made of a resin material, there is no way for the charge to escape, and as the number of opening and closing operations of the valve increases, the charge is attracted to the magnet side, and the magnet may be charged to a high potential. As a result, the internal circuit of the encoder IC, which faces the highly charged magnet, is charged due to static electricity, which may cause electrostatic breakdown or malfunction of the encoder IC.

In addition, a bearing called an oil-impregnated bearing is generally used for the bearing of the output shaft. When the output shaft rotates, a lubricating oil film penetrates and electrically insulates. By moving and storing, the bearing and the output shaft come into metallic contact and conduct, and the electric charge accumulated on the output shaft advances to the path of the oil-impregnated bearing and the housing that constitutes the actuator and disappears. For this reason, even if the holder were simply made of a resin material with insulating properties, this would only eliminate the charge on the output shaft (control shaft), and the magnet would still remain charged, causing the encoder IC to become static. It may not be possible to prevent electrical breakdown or malfunction.

Furthermore, if the magnet is surrounded by a holder made of a non-magnetic material such as a resin material, it becomes difficult to form a magnetic circuit around the magnet, resulting in a decrease in magnetic flux due to a decrease in permeance (increase in magnetic resistance). Also, problems such as deterioration of the magnetic flux over time and destabilization of the magnetic flux due to a decrease in the magnetic operating point also occur.
In particular, when a neodymium magnet is used as a magnet, high-temperature irreversible demagnetization is likely to occur when used in a high-temperature environment (for example, 120° C.) such as a steam valve in a low permeance state, which easily leads to deterioration of the function as a magnet.

For the reason described above, even if the holder is provided using a resin material that is excellent in workability as a non-magnetic material, the magnet is prevented from being charged, and the encoder IC is prevented from being electrostatically damaged or malfunctioned. There has been a demand for the development of a non-contact electric valve actuator that accurately detects the rotation state of a detection magnet provided on the output shaft side.

The present invention was developed to solve the conventional problems, and its purpose is to accurately detect the rotational state of the output shaft side of an electric valve actuator using a non-contact sensor, thereby improving workability. To provide an actuator detection magnet mounting structure and an electric actuator for a valve that can be easily manufactured using a non-magnetic material with excellent resistance, can be made compact and can maintain high detection performance while preventing malfunction due to electrification and static electricity. That's what it is.

In order to achieve the above object, the invention according to claim 1 is a magnet mounting structure for detecting a rotation angle of an output shaft of an electric valve actuator that transmits rotation of an electric motor to an output shaft, wherein the magnet is non-magnetic. A detection magnet for an electric actuator for a valve that is fixed coaxially to the output shaft by a magnet holder made of a material, and a part of the magnet is in electrical contact with the output shaft through a communication hole provided in the magnet holder due to different metals. mounting structure.

In the invention according to claim 2, a mounting hole is formed on the bottom side of the magnet holder formed in a substantially cylindrical shape, a mounting hole is formed on the top side of the magnet holder, and communication holes are formed between the mounting holes and the mounting holes. Detection of an electric valve actuator in which the upper end of the output shaft is mounted in the hole and the magnet is mounted in the mounting hole in a positioned state, and the protrusion formed on either the output shaft or the magnet is exposed to the other side through the communication hole. This is the mounting structure of the magnet for

The invention according to claim 3 is a mounting structure of a detection magnet for an electric actuator for a valve, in which the tip surface side of the protrusion protrudes from the mounting hole side or the mounting hole side through the communication hole.

In the invention according to claim 4, a gap is formed between the outer peripheral side of the protrusion and the communicating hole, and the gap is filled with an adhesive to fix the magnet holder and the output shaft or the magnet. is the mounting structure of the detection magnet.

The invention according to claim 5 is a mounting structure of a detection magnet for an electric valve actuator, in which a plurality of notch grooves for air venting are formed at equal intervals on the outer peripheral side of a mounting hole.

The invention according to claim 6 is a mounting structure of a detection magnet for an electric actuator for a valve, in which the rotation angle of an output shaft is detected by a magnetic encoder using a magnet and an encoder IC arranged opposite to the magnet. .

According to a seventh aspect of the invention, there is provided an electric valve actuator in which a detection magnet is attached by a detection magnet attachment structure for an electric valve actuator.

According to the first aspect of the invention, since the magnet is coaxially fixed to the output shaft by the magnet holder, the rotation angle of the output shaft can be detected by the leakage magnetic flux of the magnet while achieving compactness. The holder is made of a non-magnetic material, and part of the magnet is always in contact with the output shaft through the communication part provided in the magnet holder . electrical contact between a part of the magnet and the output shaft due to different metals through the communication hole of the magnet holder, the electrical charge that has accumulated through the output shaft is discharged to prevent the magnet from being charged by static electricity. Accurate detection performance is achieved by detecting the rotation state of the output shaft side with a non-contact sensor while preventing malfunction on the detection side. If the non-magnetic material that constitutes the magnet holder is made of a general-purpose resin material, this material can be easily obtained, and since no cutting work is required, the magnet holder can be easily manufactured. Since there is no risk of electrical corrosion occurring between the magnet holder and the magnet, it is possible to prevent oxidation deterioration of the magnet and maintain an accurate detection function of the rotational state of the output shaft.

According to the second aspect of the invention, the magnet can be mounted on the output shaft by using the magnet holder formed in a substantially cylindrical shape, and space can be saved. By mounting the magnets in a positioned state, they can be firmly integrated while being accurately centered. The projecting portion formed on either the output shaft or the magnet is exposed to the other side through the communicating portion, so that they can be reliably brought into contact with each other to prevent electrification.

According to the third aspect of the invention, when the output shaft and the magnet are combined by the magnet holder, the tip surface side of the projection formed on either the output shaft or the magnet in a state in which they are aligned and positioned. is reliably brought into contact with the other side, it is possible to prevent a decrease in permeance of the magnet and obtain a stable leakage magnetic flux. Therefore, even when high-temperature fluid such as steam flows through the valve connected to the electric actuator main body, irreversible demagnetization of the magnet is prevented. position control accuracy is improved.

According to the fourth aspect of the invention, since the magnet holder is fixed to the output shaft or the magnet using an adhesive, fixing screws are not required, and the simplified mounting structure allows the magnet holder to be positioned. High-precision assembly work becomes easy without adjustment.

According to the fifth aspect of the invention, when the magnet is attached to the magnet holder, the magnet can be accommodated in the attachment hole while the air is removed through the cutout groove. can be detected accurately.

The mounting structure of the detection magnet of the present invention is particularly effective when the rotation angle of the output shaft is detected by a magnetic encoder as in the sixth aspect of the invention.

According to the seventh aspect of the invention, since the magnet is coaxially fixed to the output shaft by the magnet holder, the rotation angle of the output shaft side can be detected by the leakage magnetic flux of the magnet while achieving compactness. The holder is made of non-magnetic material, and part of the magnet is always in contact with the output shaft through the communication part provided in the magnet holder. It is possible to provide an electric valve actuator that exhibits accurate detection performance by detecting the rotation state of the output shaft side with a non-contact sensor while preventing operation. If the non-magnetic material that constitutes the magnet holder is made of a general-purpose resin material, this material can be easily obtained, and since no cutting work is required, the magnet holder can be easily manufactured. Since there is no risk of electrical corrosion occurring between the magnet holder and the magnet, it is possible to prevent oxidation deterioration of the magnet and maintain an accurate detection function of the rotational state of the output shaft.

1 is a longitudinal sectional view of an electric valve actuator; FIG. (a) is a cross-sectional view taken along the line AA of FIG. 1; (b) is an enlarged view of part B of (a). FIG. 4 is an exploded perspective view showing a detached state of the magnet; It is a perspective view which shows the attachment part vicinity of a magnet.

A mounting structure of a detection magnet for an electric valve actuator and an embodiment of an electric valve actuator according to the present invention will be described below in detail with reference to the drawings.
1 shows a longitudinal sectional view of an electric valve actuator, FIG. 2(a) is a sectional view taken along line AA in FIG. 1, and FIG. 2(b) is an enlarged view of part B in FIG. 2(a). showing.

The present invention relates to a mounting structure for a magnet provided on the output shaft side of an electric actuator, and the magnet can detect the rotation angle of the output shaft.
1 and 2, an electric valve actuator (hereinafter referred to as an actuator body 1) includes an electric motor 2, a reduction gear train 3, an output shaft 4, a magnet 5, a magnet holder 6, and an encoder control board 7. Each part is housed between a lower base 9 and a cover 10 covering the upper side, which form a housing 8 of the actuator body 1 .

The base 9 is formed in the shape of a circular frame, and the reduction gear train 3 is arranged within the frame of the base 9 . An electric motor 2 is provided on the input side of the reduction gear train 3, and an output shaft 4 is provided on the output side. The rotation of the electric motor 2 is decelerated by the reduction gear train 3 and output from the output shaft 4, which rotates the valve body through the stem.

In this example, a control shaft 4a is coaxially formed above the output shaft 4, and the output shaft 4 and the control shaft 4a are attached to a base 9 by bearings 20 and 20a so as to rotate together. . At the upper end of the control shaft 4a (output shaft 4), a columnar protrusion 21 having a smaller diameter than the outer diameter of the control shaft 4a is projected, and the magnet 5 is attached to the upper end of the protrusion 21, The magnet 5 is arranged between the control shaft 4a and the substrate 7 by the magnet holder 6. As shown in FIG. At this time, an appropriate space is provided between the magnet 5 and the substrate 7 .

The bearings 20 and 20a are oil-impregnated bearings made of metal such as copper or iron, and are filled with lubricating oil. When the output shaft 4 rotates, the lubricating oil film penetrates into the gaps between the output shaft 4 and the bearings 20 and 20a, thereby enabling electrical insulation.

The lower side of the output shaft 4 is provided so as to protrude from the bottom surface of the base 9, and a recessed groove 22 is formed in the lower end thereof. A parallel two-sided portion (not shown) formed on the upper end of the stem of the valve is engageable with the concave groove 22, and the stem is connected to the output shaft 4 by engagement between the concave groove 22 and the parallel two-sided portion.

A disk-shaped partition plate 23 is mounted above the reduction gear train 3, and column-shaped spacers 24 are mounted on the upper surface of this partition plate 23 so as to stand at a plurality of locations at appropriate intervals. A substrate 7 is fixed on top. Thereby, the substrate 7 is arranged at an appropriate distance from the partition plate 23 .

A magnetic encoder (for) IC 25 for measuring the rotation angle is mounted on the substrate 7 at a position facing the upper end surface side of the control shaft 4a (output shaft 4). The encoder IC 25 records information for detecting the rotation angle of the magnet 5, which is an object to be detected. Detecting angles.

In FIGS. 3 and 4, the magnet 5 is made of a substantially cylindrical permanent magnet, and is formed into a flat disc shape using a magnet such as a neodymium magnet having a large permeance and a large maximum energy product. In this example, for example, it is provided in a disk shape with an outer diameter of about φ8 mm to φ10 mm, and the N pole and S pole are magnetized in the thickness direction so as to be divided into two from the central portion. The surface of the magnet 5 is plated with nickel for rust prevention, and the magnet 5 is mounted on the upper end side of the control shaft 4a by a magnet holder 6. As shown in FIG.

The magnet holder 6 is molded into a substantially cylindrical shape from a general-purpose resin material that is a non-magnetic material. The bottom surface of the magnet holder 6 is formed with a mounting hole 30 having a diameter that allows the upper end of the control shaft 4a to be fitted therein. A mounting hole 31 is formed with an appropriate depth so that it can be mounted in any state. Further, a communication hole 32 is formed between the mounting hole 30 and the mounting hole portion 31, and the communication hole 32 is provided with a diameter slightly larger than the outer diameter of the protrusion 21 of the control shaft 4a.

A plurality of notch grooves 33 for air venting are formed at predetermined intervals on the outer peripheral side of the mounting hole portion 31. In this example, three notch grooves 33 are formed at equal intervals so as to penetrate to the outer peripheral side of the magnet holder 6. It is On the other hand, on the outer peripheral side of the mounting hole 32, a plurality of notch grooves 34 are formed at equal intervals along the axial direction. has become easier.

The magnet holder 6 is fitted with the magnet 5 in a positioned state in the mounting hole 31 on the top side, and the upper end portion of the output shaft 4a is fitted and fixed in the mounting hole 30 on the bottom side in a positioned state. At this time, the projecting portion 21 formed on the output shaft 4 is exposed from the mounting hole 30, which is the other side of the mounting hole portion 31, through the communication hole 32, and a portion of the magnet 5 and the output shaft 4 come into contact with each other. are electrically connected. Moreover, by partially contacting these to form a magnetic circuit, a magnetic circuit is secured around the magnet 5 to prevent a decrease in the permeance coefficient. In this case, a stable leakage magnetic flux is ensured that is distributed from the upper surface side of the magnet 5 to the back surface through the side surface, or in the opposite direction.

The magnet 5 faces the magnet holder 6 from the encoder IC 25 with a gap of about several millimeters, and is attached at an arbitrary angle to the control shaft 4a regardless of the magnetization angle. When the control shaft 4a rotates, the magnet 5 rotates together with the magnet holder 6 integrally with the control shaft 4a.

When the magnet holder 6 is attached to the output shaft 4a, the tip surface 21a side of the protrusion 21 of the output shaft 4a protrudes upward through the communication hole 32 from the mounting hole 30 side, and the magnet 5 is placed on the protrusion tip surface 21. As a result, the magnet 5 is reliably in contact with the output shaft 4 . At this time, the center position of the magnet 5 is aligned with the center position of the encoder IC 25 .

In this case, since the inner diameter of the communication hole 32 is slightly larger than the outer diameter of the protrusion 21 , a gap S is formed between the outer peripheral side of the protrusion 21 and the communication hole 32 . By filling the gap S with an adhesive 35 , the magnet holder 6 and the output shaft 4 are fixed together by the adhesive 35 . The adhesive 35 is also applied between the magnet 5 and the mounting hole 31 and between the output shaft 4 and the mounting hole 30 .

When the output shaft 4 rotates, the magnetic flux leaked from the N and S poles of the magnet 5 is interlinked with the encoder IC 25, and the output voltage from the hall element (not shown) arranged inside the encoder IC 25 continuously generates a vector. After calculating and obtaining an angle analog signal, the rotation angle is detected by converting the angle analog signal into a digital signal.

In this case, since the angle analog signal of the encoder IC 25 is transmitted to a digital signal through the copper foil pattern on the substrate 7 by high-speed serial communication, accurate rotation angle data of the output shaft 4 can be obtained.

In this way, the rotation of the magnet 5 of the control shaft 4a is taken in as a signal by the encoder IC 25, whereby the absolute value of the output opening of the actuator body 1 is obtained as a digital value, and the rotation state of the control shaft 4a is measured. . The rotation of the magnet 5 is measured by the non-contact encoder IC 25, and this electronic non-contact state prevents contact failure.
Therefore, the control shaft 4a (magnet 5) can be measured with high precision by the encoder IC 25 regardless of the rotating state.

In this case, when the output shaft 4 stops at the fully closed position or the fully opened position of the valve, the direction of leakage magnetic flux generated from the magnet 5 stops changing, and the angle data value output from the encoder IC 25 stops changing. The duration of no change in the angle data is preliminarily recognized as the fully closed or fully open state and recorded as fully closed or fully open position data. During the opening/closing operation of the valve, the fully closed or fully opened state of the valve can be detected by comparing the fully closed or fully opened position data with the rotational state of the output shaft 4 caused by the magnet 5 .

In FIG. 1, the electric motor 2 is a DC (direct current) brushless motor with a general structure and is fixed to the upper surface of the partition plate 23 . When the electric motor 2 is a DC brushless motor, there is no mechanically sliding contact part, which avoids the generation of sparks and arc discharges during commutation, suppresses the generation of insulators, and prevents dead points during operation. Become. Therefore, it is possible to provide a highly reliable electric valve that can rotate the output shaft 4 whose opening/closing position is adjusted with high accuracy. In addition, deterioration of insulation is prevented, and high-precision operation is maintained over a long period of time. A cable 36 is connectable to the electric motor 2 from the outside of the actuator main body 1 , and a voltage is supplied from an external power source (not shown) through the cable 36 and the control board 7 to rotate the electric motor 2 .

The reduction gear train 3 has an input shaft (not shown), an output shaft 4, and a plurality of reduction gears 3a. can be output from.

In the above-described embodiment, the protrusion 21 is provided on the output shaft 4 side and is exposed from the communication hole 32 to the magnet 5 side. 32 may be exposed on the output shaft 4 side. In this case, the tip end surface 21 a of the protrusion 21 protrudes toward the mounting hole 31 through the communication hole 32 , so that the tip end surface 21 a of the protrusion 21 can come into contact with the output shaft 4 . Furthermore, by filling the gap S between the outer peripheral side of the protrusion 21 and the communication hole 32 with an adhesive 35, the magnet holder 6 and the magnet 5 can be fixed together.

Further, the control shaft 4a is integrated with the upper portion of the output shaft 4, and the magnet 5 is attached to the upper end of the control shaft 4a by the magnet holder 6 to detect the rotation angle of the output shaft 4. The control shaft 4a need not be provided integrally with the output shaft 4, and the control shaft 4a may be provided in the middle of the reduction gear train 3 separately from the output shaft 4, and the rotation angle of the control shaft 4a may be detected. In this case, the control shaft 4a shall be regarded as an output shaft.

It is not always necessary to provide the reduction gear train 3 between the electric motor 2 and the output shaft 4. Any structure may be used as long as the rotation of the electric motor 2 is transmitted to the output shaft 4 by an appropriate means. The magnet mounting structure described above can also be applied to the actuator of .

The valve connected to the actuator main body 1 may be a valve other than a ball valve. For example, even when various valves such as a butterfly valve are connected, high-precision rotation control using the magnet 5 is possible. .

Next, the attachment structure of the detection magnet of the electric valve actuator of the present invention and the operation of the electric valve actuator of the above embodiment will be described.
In the actuator body 1, the magnet 5 is coaxially fixed to the output shaft 4 (control shaft 4a) by the magnet holder 6, and a part of the magnet 5 is brought into contact with the output shaft 4 through the communication hole 32 of the magnet holder 6. Therefore, they are electrically connected at all times. Therefore, even if the magnet 5 is charged with the electric charge on the valve body through the output shaft 4 during the operation, the electric charge on the output shaft 4 is removed by the electrical connection between the output shaft 4 and the bearing 20 when the operation is stopped. It discharges and reliably prevents the encoder IC 25 from electrostatic damage, malfunction, and the like. As a result, even if the magnet 5 is temporarily charged, it can be discharged periodically.

In this case, the electric charge on the valve body is temporarily transferred from the output shaft 4 to the magnet 5. and the output shaft 4 are in direct contact and electrically connected without intervening lubricating oil, and the electric charge accumulated in the magnet 5 is discharged efficiently.

The upper end of the output shaft 4 (control shaft 4a) is mounted in the mounting hole 30 on the bottom side of the magnet holder 6, and the magnet 5 is mounted in the mounting hole 31 on the top side of the magnet holder 6 in a positioned state. Since the surfaces 21a are in contact with each other, a stable leakage magnetic flux can be obtained without reducing the permeance of the magnet 5. FIG. In particular, even when a high-temperature fluid such as high-pressure steam flows through the valve, the magnet 5 is prevented from being irreversibly demagnetized, and the magnet 5 maintains highly accurate position control.

The positional relationship between the output shaft 4 (control shaft 4a) and the two-pole magnetized magnet 5 is not restricted by digital control. can be attached in any direction, and the magnet 5 can be fixed while simplifying the shape of these parts.

Moreover, the magnet holder 6 is molded from a general-purpose resin material, and through this resin magnet holder 6, the upper surface side of the output shaft 4 and the bottom surface side of the magnet 5 are brought into contact with each other over a minimum necessary area. It is possible to provide a highly reliable actuator body 1 by minimizing electrical corrosion due to contact of different metals of the magnet 5, and preventing charging for a long time even in a poor environment where charging is likely to occur. .
Furthermore, since the magnet holder 6 is made of a resin material, cutting work can be omitted, and the man-hours for processing can be reduced, making it possible to manufacture easily.

The gap S between the outer peripheral side of the projection 21 and the communication hole 32 is filled with an adhesive 35, and the magnet holder 6 and the output shaft 4 are fixed with this adhesive 35 in an arbitrary rotational state, thereby forming a fixing screw. The structure can be simplified without using external parts such as the magnet 5, and a stable leakage magnetic flux can be ensured without requiring the positioning adjustment of the magnet 5.

Since the encoder IC 25 and the magnet 5 are not in contact with each other, even when the actuator body 1 is placed in an environment where vibrations and shocks are likely to occur, such as in a vehicle, damage, contact failure, and malfunction are prevented to extend the life of the actuator. can be achieved. Since no lateral pressure is applied to the control shaft 4a for detecting its rotation, the backlash of the control shaft 4a is suppressed even after long-term use, and the rotation angle of the output shaft 4 does not change.

The distribution of leakage magnetic flux from the N pole to the S pole of the magnet 5 is always constant, and the rotation of the output shaft 4 also rotates the magnetic flux distribution. Accurate angle data of the output shaft 4 can be obtained by performing vector operations on the respective Hall voltages.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the description of the above embodiments, and is within the spirit of the invention described in the claims of the present invention. and can be modified in various ways.

REFERENCE SIGNS LIST 1 Actuator body 2 Electric motor 3 Reduction gear train 4 Output shaft 5 Magnet 6 Magnet holder 21 Projection 21a Tip surface 30 Mounting hole 31 Mounting hole 32 Communication hole 33 Notch groove 35 Adhesive S Gap

Claims (7)

A magnet mounting structure for detecting a rotation angle of an output shaft of an electric valve actuator that transmits rotation of an electric motor to an output shaft, wherein the magnet is coaxially fixed to the output shaft by a magnet holder made of a non-magnetic material. and a part of the magnet and the output shaft are electrically contacted by different metals through a communication hole provided in the magnet holder. A mounting hole is formed on the bottom side of the magnet holder formed in a substantially cylindrical shape, a mounting hole portion is formed on the top side of the magnet holder, and the communication holes are formed between the mounting holes and the mounting hole portions. 2. The magnet according to claim 1, wherein the magnets are mounted in the upper end portion and the mounting hole of the magnet in a positioned state, and a protrusion formed on either the output shaft or the magnet is exposed to the other side through the communication hole. Mounting structure of magnet for detection of electric actuator for valve. 3. The attachment structure of a detection magnet for an electric valve actuator according to claim 2, wherein the tip end surface side of the protrusion protrudes from the mounting hole side or the mounting hole side through the communication hole. 4. The magnet holder and the output shaft or the magnet according to claim 2, wherein a gap is formed between the outer peripheral side of the protrusion and the communication hole, and the gap is filled with an adhesive to fix the magnet holder to the output shaft or the magnet. Mounting structure of magnet for detection of electric actuator for valve. 5. The attachment structure of a detection magnet for an electric valve actuator according to any one of claims 2 to 4, wherein a plurality of notch grooves for air release are formed at equal intervals on the outer peripheral side of the mounting hole. 6. Detection of the electric valve actuator according to any one of claims 1 to 5, wherein the rotation angle of the output shaft is detected by a magnetic encoder using the magnet and an encoder IC disposed facing the magnet. Mounting structure of the magnet for An electric valve actuator having a detection magnet mounted thereon by the mounting structure for a detection magnet for an electric valve actuator according to any one of claims 1 to 6.

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