JP6801170B2 - Manufacturing method of rotation angle detection magnet, rotation angle detection device and rotation angle detection magnet - Google Patents

Description

The present invention includes a magnet for detecting a rotation angle used when magnetically detecting the rotation angle of a rotating object to be detected, and a magnet for detecting the angle of rotation, and detecting the angle of rotation of the object to be detected. The present invention relates to an apparatus and a method for manufacturing a magnet for detecting an angle of rotation, which manufactures the magnet for detecting the angle of rotation.

The shape of the magnet used in the detection device that magnetically detects the rotation angle of the rotating object to be detected is generally a substantially disk shape. The substantially disc-shaped magnets are classified into two types according to the difference in the magnetizing direction.

One type is a type in which the north pole and the south pole are magnetized one by one in each region of a semicircle, and the magnetizing direction is the radial direction orthogonal to the rotation axis. It is called a magnet. The other type is a magnet in which a different pole is magnetized along the rotation axis direction so that the magnetizing direction is parallel to the rotation axis direction, and is called a surface two-pole magnetizing type magnet. Patent Document 1 discloses a rotation angle detector using such a diameter 2-pole magnetizing magnet or a surface 2-pole magnetizing magnet.

Japanese Unexamined Patent Publication No. 2010-160036

Regardless of the magnetizing direction of the magnet, the sensor element for magnetic detection detects the leakage magnetic flux component in the direction orthogonal to the rotation axis, and which magnetizing type magnet is used depends on the magnet. It is determined in consideration of the distance between the magnet and the sensor element, the sensitivity of the sensor element, the strength of the magnetic force of the magnet, and the like.

In the case of a surface two-pole magnetizing type magnet, the leakage magnetic flux easily reaches far from the magnet surface, so that the distance between the magnet and the sensor element can be increased. On the other hand, in the case of a magnetized magnet having two poles in diameter, the leakage magnetic flux is less likely to reach farther than the surface of the magnet, so that the sensor element must be arranged in the vicinity of the magnet. If the distance between the magnet and the sensor element can be increased, for example, the mold resin for fixing the sensor element to the control board or the like can be thickened, or it can be covered with a cover such as non-magnetic stainless steel. The reliability of the magnet is improved, and the degree of freedom in structural design is also increased. Therefore, the larger the distance between the magnet and the sensor element, the more advantageous points there are.

On the other hand, the workability of magnetizing is significantly different between the surface 2-pole magnetizing type magnet and the diameter 2-pole magnetizing type magnet. When magnetizing on two planes, it is common to magnetize magnets one by one using a dedicated magnetizing yoke (combined magnetizing coil and iron yoke) that matches the dimensions of the magnet. Is. This is because the magnetic field strength required for magnetizing is as large as 2 tesla or more, and it is difficult to construct a magnetic circuit for magnetizing a plurality of magnets at one time. On the other hand, when magnetizing to two poles in diameter, a magnetic field strength of 2 tesla or more can be easily generated in a relatively large space by using an air-core coil, so a large number of magnets can be magnetized to two poles in diameter at once. it can. That is, it can be said that 2-pole magnetizing with a diameter is a low-cost magnetizing method suitable for mass production.

As described above, the two-pole magnetizing type magnet has an advantage that the magnetizing workability is good, but has a drawback that it is difficult to obtain a large distance from the sensor element.

As a measure to increase the distance between the magnet and the sensor element, the two-pole magnetized magnet having a diameter in Patent Document 1 has a substantially disk-shaped magnet having a shape in which the surface facing the sensor element is recessed from the surroundings. However, in Patent Document 1, only the surface of the magnet facing the sensor element (the central portion of the magnet) is recessed, and the edge portion of the magnet not facing the sensor element remains as it is. Therefore, the distance from the control board to which the sensor element is fixed is still short, and the structural reliability is not improved. Further, if the size of the magnet is to be maintained in order to obtain the required detection sensitivity, the diameter of the magnet must be increased, and the size of the magnet and the size of the detector using this magnet become large. There is.

The present invention has been made in view of such circumstances, and is a two-pole magnetized magnet having a diameter that is good in magnetizing workability even if it has a small shape and can increase the distance to the sensor element. An object of the present invention is to provide a rotation angle detection magnet, a rotation angle detection device capable of reducing the size, and a method for manufacturing a rotation angle detection magnet capable of manufacturing a small rotation angle detection magnet.

The rotation angle detection magnet according to the present invention is a rotation angle detection magnet used when magnetically detecting a rotation angle, and has a substantially disk shape magnetized in the radial direction and is formed in the rotation direction. One N pole and one S pole are magnetized in each region divided into two equal parts by 180 degrees, and the central part is a convex part, and the convex part is opposed to the magnetizing direction and is in the center. A strip having a pair of inclined portions inclined toward the portion side and a flat portion connected to the pair of inclined portions, the flat portion having a magnetizing direction as a short dimension and a direction orthogonal to the magnetizing direction as a longitudinal dimension. It has a flat surface having a shape, the longitudinal dimension is substantially equal to the diameter, the pair of inclined portions are magnetized to different magnetic poles, and a flat portion extending from the end of the convex portion to the peripheral edge is formed. It is characterized by having.

The rotation angle detection magnet of the present invention has a substantially disk shape as a whole, is magnetized in the radial direction thereof, and has a pair of inclined portions that face the magnetizing direction and are inclined toward the central portion. A convex portion formed by a flat portion connected to the pair of inclined portions is provided in the central portion. Further, the longitudinal dimension of the flat portion is substantially equal to the diameter. Even if it is small, the distance from the sensor element can be increased because such a convex portion is provided in the central portion facing the sensor element, and magnetization can be easily performed because the diameter is two poles.

In the rotation angle detection magnet according to the present invention, the lateral dimension of the flat portion is 1/4 or more and 1/2 or less of the diameter, and the angle formed by its own rotating surface and the inclined portion is 30 degrees or more and 60 degrees. It is characterized by being less than or equal to the degree.

In the rotation angle detection magnet of the present invention, the longitudinal dimension of the flat portion having a substantially rectangular shape is substantially equal to the diameter, the lateral dimension is 1/4 or more and 1/2 or less of the diameter, and the inclination angle of the inclined portion (self). The angle formed by the rotating surface and the inclined portion, that is, the angle formed by the rotating surface perpendicular to the rotation axis and the inclined portion when incorporated in the rotation angle detecting device) is 30 degrees or more and 60 degrees or less. Therefore, even if the shape is relatively small, the leakage magnetic flux can reach a long distance, and the sensor element can be arranged at a far away position.

The rotation angle detecting device according to the present invention is a rotation angle detecting device that detects the rotation angle of a rotating object to be detected, and is attached to the object to be detected and rotates integrally with the rotating shaft. It is characterized by including the above-mentioned rotation angle detection magnet and a sensor element that detects a leakage magnetic flux component in a direction orthogonal to the rotation axis due to rotation of the rotation angle detection magnet.

In the rotation angle detection device of the present invention, the sensor element detects the leakage magnetic flux component in the direction orthogonal to the rotation axis due to the rotation of the rotation angle detection magnet, and based on this detection result, the rotation angle of the object to be detected is determined. Ask.

The rotation angle detection device according to the present invention is characterized in that the sensor element is arranged so as to face the flat portion of the rotation angle detection magnet.

In the rotation angle detection device of the present invention, the sensor elements are arranged to face each other on the flat portion of the rotation angle detection magnet. Therefore, the detection accuracy is not impaired even if the rotation angle detection magnet and the sensor element are displaced from each other.

The rotation angle detection device according to the present invention is further provided with a metal fixing jig having a claw portion for fixing the rotation angle detection magnet.

In the rotation angle detection device of the present invention, the rotation angle detection magnet is fixed by the claw portion of the metal fixing jig. Therefore, since the rotation angle detection magnet rotates reliably and integrally with the rotation axis, the rotation angle detection accuracy becomes high.

The method for manufacturing a magnet for detecting the angle of rotation according to the present invention is a method for manufacturing a magnet for detecting the angle of rotation used when magnetically detecting the angle of rotation, in which a mixture of magnetic powder and a thermosetting resin is compressed. It is characterized in that the magnet for detecting the rotation angle described above is manufactured by molding.

In the method for manufacturing a magnet for detecting the rotation angle of the present invention, the magnet for detecting the rotation angle is manufactured by compression molding. Therefore, the ratio of magnetic powder to the material can be increased as compared with injection molding, and a magnet for detecting the rotation angle, which is small but has a necessary and sufficient magnetic force, can be manufactured.

According to the present invention, it is possible to provide a two-pole magnetizing type magnet for detecting the angle of rotation, which has good magnetizing workability even in a small shape and can increase the distance to the sensor element. It is possible to provide a rotation angle detection device using this rotation angle detection magnet and having high detection accuracy. Further, it is possible to manufacture this small magnet for detecting the rotation angle having a necessary and sufficient magnetic force.

It is a perspective view which shows the rotation angle detection magnet which concerns on this invention. It is a perspective view which shows the whole structure of the rotation angle detection apparatus which concerns on this invention. It is sectional drawing, side view and top view which show the rotation angle detection apparatus which concerns on this invention. It is a top view and a side view showing each dimension in the rotation angle detection magnet which concerns on this invention. It is a figure which shows each dimension of the rotation angle detection magnet in each Example, and the distance between sensor elements. It is a figure which shows the diameter of the magnet, the magnetizing method, and the distance between sensor elements in a prior art example, a comparative example, and an Example. It is the schematic which shows the shape of a magnet and the magnetic field direction distribution in a comparative example and an Example.

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments thereof. FIG. 1 is a perspective view showing a magnet for detecting a rotation angle according to the present invention.

The rotation angle detection magnet 1 (hereinafter, simply referred to as magnet 1) according to the present invention is, for example, an Nd-Fe-B-based bond magnet, and has a substantially disk shape as a whole. The magnet 1 is a two-pole type magnetizing magnet having an N pole and an S pole magnetized in each region divided into two equal parts by 180 degrees in the rotation direction.

The central portion of the magnet 1 is a convex portion 11 that projects upward (toward the side facing the sensor element 4 described later). The convex portion 11 includes a pair of inclined portions 12 and 12 that face the magnetizing direction (direction of the arrow in FIG. 1) and are inclined toward the central portion, and a flat portion 13 that is continuous with the pair of inclined portions 12 and 12. have. In other words, in this convex portion 11, the contour seen from the magnetizing direction has a rectangular shape with no inclination, and the contour seen from the direction rotated 90 degrees from the magnetizing direction is a pair of symmetrical upwards. Has slopes at both ends, and has a flatness connected to this pair of slopes at the center.

The flat surface, which is the upper surface of the flat portion 13, has a strip shape with the magnetizing direction as the short dimension and the direction orthogonal to the magnetizing direction as the longitudinal dimension. The strip-shaped longitudinal dimension is substantially equal to the diameter of the magnet 1, and the lateral dimension is 1/4 or more and 1/2 or less of the diameter of the magnet 1. The upper surface of the inclined portions 12 and 12 is an inclined surface, and the inclined angle of the inclined portions 12 and 12 is 30 degrees or more and 60 degrees or less. This inclination angle is an angle formed by the rotating surface of the magnet 1 and the inclined portions 12, 12.

FIG. 2 is a perspective view showing the overall configuration of the rotation angle detection device according to the present invention. Further, FIG. 3 is a cross-sectional view, a side view, and a top view showing the rotation angle detecting device according to the present invention. The rotation angle detection device 10 includes the above-mentioned magnet 1 whose configuration is shown in FIG. 1, a rotation shaft 2 which is attached to a rotating object to be detected (not shown) by, for example, fastening and rotates around the axis, and a magnet 1. It includes a fixing jig 3 for supporting and fixing, a sensor element 4 for detecting the leakage magnetic flux from the magnet 1, and a calculation unit 5 connected to the sensor element 4.

The fixing jig 3 is made of iron, for example, and has a thin plate shape. The fixing jig 3 covers the lower surface and the side surface of the magnet 1, and the magnet 1 is fixed by the claws 3a and 3a provided on both sides in the magnetizing direction. The upper surface of the magnet 1 is not covered with the fixing jig 3, and the inclined surfaces of the inclined portions 12 and 12 and the strip-shaped flat surface of the flat portion 13 are open.

The rotating shaft 2 has a long columnar shape, and is made of low carbon steel such as stainless steel so as to withstand press fitting. One end of the rotating shaft 2 is caulked and fixed to the center of the fixing jig 3. At the time of detecting the rotation angle, the other end of the rotating shaft 2 is attached to the object to be detected, and the rotating shaft 2, the fixing jig 3 and the magnet 1 are integrally rotated according to the rotation of the object to be detected. ing.

The sensor element 4 is provided above the flat portion 13 of the magnet 1 by an appropriate long distance (d) (see FIG. 3). The sensor element 4 is a magnetic detection element such as an AMR element or a GMR element whose output changes according to a change in the direction of a magnetic field. The distance d from the magnet 1 to the sensor element 4 may be appropriately set in consideration of the sensitivity of the sensor element 4, the strength of the magnetic force of the magnet 1, and the like.

The sensor element 4 detects the leakage magnetic flux from the magnet 1 in the direction orthogonal to the rotation axis 2 and outputs it to the calculation unit 5. The calculation unit 5 calculates the rotation angle of the object to be detected based on the output result from the sensor element 4.

Since the flat portion 13 is provided in the central portion of the magnet 1 and the sensor element 4 is provided above the flat portion 13, even if an axis shift occurs between the magnet 1 and the sensor element 4, the detection function can be performed. It becomes hard to be damaged. Therefore, it is preferable that the short width of the flat portion 13 is substantially equal to the design value of the axial deviation.

Next, the method for manufacturing the magnet 1 according to the present invention as described above will be described. The magnet 1 of the present invention is specifically manufactured by the following procedure using a compression molding method.

First, a thermosetting resin (for example, an epoxy resin) is added and mixed with the anisotropic Nd-Fe-B-based magnetic powder to obtain a material. If a large amount of thermosetting resin is contained, the magnetic properties of the magnet are deteriorated. Therefore, it is preferable to add 1% by mass or more and 8% by mass or less.

Next, the obtained material is filled in a press die at a predetermined temperature in the molding machine, and a magnetic field perpendicular to the rolling direction is applied by an air core coil while applying molding pressure in the molding machine to shape the shape into a predetermined shape. By magnetizing, a magnet 1 as shown in FIG. 1, which is magnetized with two poles in diameter, is manufactured. When an isotropic magnetic powder is used, it is not necessary to apply a magnetic field for molding.

The magnetic powder used includes hard ferrite powder, Sm-Fe-N magnetic powder, and Sm-Co magnetic powder in addition to the anisotropic Nd-Fe-B magnetic powder. Further, in addition to the thermosetting resin, a lubricant may be added to the anisotropic Nd-Fe-B based magnetic powder. Examples of lubricants include calcium stearate. The addition amount is preferably 0.1% by mass or more and 2% by mass or less.

Since the compression molding method does not require a large fluidity of the material as compared with the injection molding method, the filling rate (ratio) of the magnetic powder in the material can be increased. Therefore, in the present invention, since the magnet 1 is manufactured by the compression molding method, it is possible to manufacture the magnet 1 having the above-mentioned shape and having good magnetic characteristics as compared with injection molding.

Next, a specific example of the magnet 1 according to the present invention as described above will be described. FIG. 4 is a top view and a side view showing each dimension of the rotation angle detection magnet according to the present invention, and FIG. 5 shows each dimension of the rotation angle detection magnet in each Example (Example 1-3). It is a chart showing the distance between sensor elements.

In FIGS. 4 and 5, Φ (mm) represents the diameter of the magnet 1, h (mm) represents the height of the magnet 1 (the distance from the lower surface to the upper surface of the flat portion 13), and w (mm). Represents the width of the short dimension in the flat portion 13, θ (degree) represents the inclination angle of the inclined portion 12, and is formed by the rotating surface of the magnet 1 orthogonal to the rotating axis 2 and the inclined portion 12 of the magnet 1. It represents 12 inclination angles of the inclined portion which is an angle. Further, d (mm) shown in FIG. 5 represents the distance between the magnet 1 and the sensor element 4 as described above, and when Φ, h, w, and θ are changed in each embodiment, It represents the distance when the sensitivity of the sensor element 4 is 50 mT.

Since the rotation angle detection device is generally extremely small compared to the object to be detected, the diameter (Φ) of the magnet used is preferably about 5 to 30 mm, more preferably about 10 to 20 mm. Therefore, as an example, as shown in FIG. 5, three types of Examples 1-3 having diameters (Φ) of 10 mm, 15 mm, and 20 mm are presented.

In the magnet 1 of the present invention, the flat portion 13 has a strip shape, the longitudinal dimension of the flat portion 13 is substantially equal to the diameter (Φ), and the lateral dimension (w) of the flat portion 13 is 1 of the diameter (Φ). It is preferable that the inclination angle (θ) of the inclined portion 12 is 30 degrees or more and 60 degrees or less. The preferred reasons are as follows.

If the short dimension (w) of the flat portion 13 of the magnet 1 is less than 1/4 of the diameter (Φ) and is too small, the uniform region of the magnetic field becomes narrow, so that the sensor element 4 and the magnet 1 It becomes necessary to improve the assembly accuracy and the usability deteriorates. On the other hand, when the short dimension (w) exceeds 1/2 of the diameter (Φ) and is too large, it becomes difficult for the magnetic flux to flow to the upper surface side, and a large distance (d) from the sensor element 4 can be obtained. It disappears. Further, when the inclination angle (θ) is less than 30 degrees and is too small, it becomes difficult for the magnetic flux to flow to the upper surface side, and the distance (d) from the sensor element 4 cannot be increased. On the other hand, when the inclination angle (θ) exceeds 60 degrees and is too large, the height (h) of the magnet 1 becomes large, which hinders miniaturization.

Next, an example in the present invention, a comparative example for making a comparison with the present invention, and a relationship with a conventional example disclosed in Patent Document 1 will be described. In each of the examples, comparative examples, and conventional examples, 2% by mass of epoxy resin, which is a thermosetting resin, was added and mixed with anisotropic Nd-Fe-B-based magnetic powder, and molded at 1 × 10 ³ MPa. After that, it was produced by heating to 200 ° C.

FIG. 6 is a chart showing the diameter of the magnet, the magnetizing method, and the distance between the sensor elements in the conventional example, the comparative example, and the embodiment. The distance between the sensor elements is the distance when the sensitivity of the sensor elements is 50 mT. Further, FIG. 7 is a schematic view showing the shape and magnetic field direction distribution of the magnets in the comparative example and the embodiment.

Conventional Example 1 in FIG. 6 is a magnet having a recessed surface facing the sensor element in the example disclosed in Patent Document 1, and uses a surface two-pole magnetizing magnet having a diameter of 10 mm. Further, Conventional Example 2 in FIG. 6 is a magnet having a recessed surface facing the sensor element in the example disclosed in Patent Document 1, and uses a two-pole magnetizing magnet having a diameter of 20 mm. There is. Comparative Example 1 in FIGS. 6 and 7 uses a surface 2-pole magnetizing magnet having a diameter of 10 mm. Comparative Example 2 in FIGS. 6 and 7 has a completely disk shape as a whole, and uses a two-pole magnetizing magnet having a diameter of 10 mm. Comparative Example 3 in FIGS. 6 and 7 has a configuration in which an inclined surface is formed over the entire circumferential direction, unlike the configuration of the present invention in which an inclined surface is provided only in a part of the circumferential direction, and the diameter is large. A 2-pole magnetized magnet with a diameter of 10 mm is used. Example 1 in FIGS. 6 and 7 uses a magnet according to the present invention having the shape shown in FIG.

In the surface 2-pole magnetizing type magnet, a yoke is usually attached to the main surface of the magnet, which is the back surface of the surface facing the sensor element and is in contact with the rotation axis, in order to suppress magnetic flux leakage. In the above-mentioned Example 1, Comparative Example 1-3, and Conventional Examples 1 and 2, the height is aligned at 5 mm, but in Conventional Example 1 and Comparative Example 1, the height of the magnet and the height of the yoke are matched. It is set to 5 mm.

When a surface 2-pole magnetizing magnet as in Conventional Example 1 and Comparative Example 1 is used, a diameter 2-pole magnetizing magnet as in Conventional Example 2, Comparative Example 2 and Comparative Example 3 is used. It can be seen that the distance to the sensor element can be increased as compared with the case where the magnet element is used. On the other hand, in the first embodiment, although a magnet having a diameter of two poles is used, the distance to the sensor element is about the same as when a magnet having a two-pole magnetizing surface is used. It has been realized.

When Comparative Example 2 and Comparative Example 3 are compared, in Comparative Example 3 in which the inclined surface is formed over the entire circumferential direction, the distance to the sensor element is larger than that in Comparative Example 2 due to the presence of the inclined surface. Can be done. However, in Comparative Example 3, it is not possible to achieve a large separation distance as in the example (Conventional Example 1 and Comparative Example 1) in which magnets having two poles of the same diameter are used.

When Comparative Example 3 and Example 1 are compared, in Comparative Example 3 in which the inclined surface is formed over the entire circumferential direction, a drop in magnetic flux is observed near the central portion, whereas the distance to the sensor element is small. Therefore, in the first embodiment in which the inclined surface is formed only in the direction opposite to the magnetizing direction, such a drop in magnetic flux is not observed and the distance to the sensor element can be increased. Moreover, in the first embodiment, a large distance comparable to that of the example (conventional example 1 and comparative example 1) in which magnets having two poles of the same diameter are used can be achieved.

From the above, in the present invention, by using the magnet 1 having a 2-pole magnetism having the above-mentioned shape, the good workability of magnetism originally possessed by the 2-pole magnetizing magnet can be maintained. However, it is possible to realize the distance to the sensor element, which is the same as in the case of the surface two-pole magnetizing type magnet. That is, in the present invention, it is possible to achieve both good workability of magnetization (in other words, mass productivity at low cost) and a large distance to the sensor element (in other words, improvement of structural reliability and design freedom). It is possible.

In the above-described embodiment, the magnet 1, the fixing jig 3, and the rotating shaft 2 are integrated, but the magnet 1 and the rotating shaft 2 are integrated without using the fixing jig 3. It may be configured. Further, the magnet 1 can be directly attached to the object to be detected without using the fixing jig 3 and the rotating shaft 2, and the rotation angle of the object to be detected can be detected.

It should be noted that the disclosed embodiments are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Magnet (Magnet for detecting rotation angle)
2 Rotating shaft 3 Fixing jig 3a Claw part 4 Sensor element 5 Calculation part 11 Convex shape part 12 Inclined part 13 Flat part

Claims (6)

In the rotation angle detection magnet used when magnetically detecting the rotation angle,
It has a substantially disk-like shape magnetized in the radial direction, and one north pole and one south pole are magnetized in each region that divides into two equal parts by 180 degrees in the rotation direction, and the central part is a convex part. The convex-shaped portion has a pair of inclined portions that face the magnetizing direction and are inclined toward the central portion, and a flat portion that is continuous with the pair of inclined portions, and the flat portion is magnetized. It has a strip-shaped flat surface whose direction is the short dimension and the direction orthogonal to the magnetizing direction is the longitudinal dimension, the longitudinal dimension is substantially equal to the diameter, and the pair of inclined portions are magnetized to different magnetic poles. A magnet for detecting a rotation angle, which is characterized by having a flat portion extending from the end of the convex portion to the peripheral edge . The claim is characterized in that the lateral dimension of the flat portion is 1/4 or more and 1/2 or less of the diameter, and the angle formed by its own rotating surface and the inclined portion is 30 degrees or more and 60 degrees or less. The magnet for detecting the rotation angle according to 1. In a rotation angle detection device that detects the rotation angle of a rotating object to be detected,
A rotating shaft attached to the object to be detected and rotating,
The rotation angle detection magnet according to claim 1 or 2, which rotates integrally with the rotation shaft.
A rotation angle detection device including a sensor element that detects a leakage magnetic flux component in a direction orthogonal to the rotation axis due to rotation of the rotation angle detection magnet. The rotation angle detection device according to claim 3, wherein the sensor element is arranged so as to face the flat portion of the rotation angle detection magnet. The rotation angle detection device according to claim 3 or 4, further comprising a metal fixing jig having a claw portion for fixing the rotation angle detection magnet. In the method of manufacturing a magnet for detecting the angle of rotation used when magnetically detecting the angle of rotation.
A method for manufacturing a magnet for detecting an angle of rotation, which comprises molding a mixture of a magnetic powder and a thermosetting resin by compression molding to manufacture the magnet for detecting the angle of rotation according to claim 1 or 2.

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