JP2003130685A - Encoder testing method and magnetizing device for test - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the position of a welded point of a permanent magnet encoder formed by the injection molding and the degree of lowering in the flux density at the welded point. SOLUTION: An injection-molded encoder is magnetized uniformly in the circumferential direction as it is shown in Fig. (A). The flux density is lowered at the welding point as it is shown in Fig. (B). The position where the flux density is lowered represents the welded point, and the degree of lowering in the flux density in comparison to other parts represents the degree of lowering in the flux density at this welded point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in combination with a sensor while being incorporated in a rolling bearing unit for rotatably supporting an automobile wheel with respect to a suspension device, and the wheel supported by the rolling bearing unit. The present invention relates to a method of inspecting an encoder made of a permanent magnet for detecting the rotation speed of a magnet and a magnetizing device for inspection. Specifically, it is used to obtain data for manufacturing a higher performance encoder by measuring the density of the magnetic flux emitted from such an encoder.

[0002]

2. Description of the Related Art An automobile wheel is rotatably supported by a suspension system, and an antilock brake system (ABS) and a traction control system (TC) are provided.
In order to detect the rotational speed of the wheel in order to control S), rolling bearing units with an encoder of various structures have been known in the past. When the wheel rotation speed is detected magnetically, the encoder whose magnetic characteristics alternate (generally at equal intervals) in the circumferential direction is used as the encoder. An encoder using permanent magnets in which S poles and N poles are alternately arranged in the circumferential direction as an encoder in which magnetic characteristics alternately change in the circumferential direction in this manner has a simple structure on the sensor side and has a low speed. In recent years, the number of cases of use is increasing from the viewpoint of ensuring the detection accuracy of time.

An encoder made of a permanent magnet used for the above-mentioned applications is formed in an annular shape (including an annular shape, a cylindrical shape, etc.) by a magnetic metal plate of carbon steel, stainless steel, etc. This is the same throughout the specification.)
A permanent magnet such as a rubber magnet or a plastic magnet is adhered to a part of the mandrel formed on the entire circumference (including a case where the rubber magnet is baked on the mandrel with a primer interposed therebetween. The same)). That is, a permanent magnet such as a rubber magnet or a plastic magnet in which a ferromagnetic powder (magnetic material) such as ferrite is mixed in a polymer material such as rubber or synthetic resin is bonded and fixed to a part of the annular mandrel. is doing. Then, S poles and N poles are alternately arranged in the circumferential direction on the surface of the permanent magnet. Because of this,
The magnetizing direction of this permanent magnet is alternately changed in the circumferential direction.

FIG. 4 shows an example of a conventional structure of a rolling bearing unit 1 for supporting a wheel in which such an encoder is incorporated. In the case of this rolling bearing unit 1, a pair of inner rings is provided at the axially intermediate portion or inner end portion of the hub 2 (the inner side in the axial direction is the width direction center side of the vehicle, the right side in FIGS. 4 and 5). A rotating wheel is formed by externally fitting 3,3. Of these hubs, a hub 4 is provided with a flange 4 for supporting and fixing a wheel on an outer end portion of an outer peripheral surface (outer in the axial direction is an outer side in the width direction of the vehicle, the left side in FIGS. The inner ring raceways 6 are provided on the outer peripheral surfaces of the inner races 3 and 3, respectively. The spline hole 5 has a spline shaft 8 provided in the constant velocity joint 7.
Have been inserted. The nut 10 is screwed onto the male screw portion 9 provided on the outer end portion of the spline shaft 8 and further tightened, so that the inner end portion of the housing portion 11 provided on the inner end portion of the spline shaft 8 is The inner end surface of the inner ring 3 is suppressed, and the pair of inner rings 3 and 3 are fixed to the hub 2.

On the other hand, an outer ring 12, which is a stationary wheel, is arranged around the rotating ring composed of the hub 2 and the inner rings 3 and 3. The outer ring 12 is internally fitted and fixed in a cylindrical bearing case 13, and the bearing case 13 can be supported and fixed to a suspension device (not shown). Further, the inner ring raceway 6 provided on the outer peripheral surface of each of the inner rings 3, 3 on the inner peripheral surface of the outer ring 12,
Outer ring raceways 14, 14 are provided at the portions facing 6 respectively. Then, between the outer ring raceways 14 and 14 and the inner ring raceways 6 and 6, a plurality of rolling elements 15 and 15 are respectively held by cages 16 and 16 so that they can roll freely. It is provided. Also, the outer ring 12
Sealing devices 17 and 17a are respectively installed between the inner peripheral surfaces of both ends of the inner ring 3 and the outer peripheral surfaces of the end portions of the inner rings 3 and 3 to shut off the internal space where the rolling elements 15 are installed from the outside. ,
Leakage of grease existing in the internal space is prevented and foreign matter is prevented from entering the internal space.

Each of the sealing devices 17 and 17a has a slinger 18 and a seal ring 19 as shown in FIG.
It uses a combination seal ring that is a combination of and. The slinger 18 is a magnetic metal plate such as a carbon steel plate such as SPCC having an L-shaped cross section and an annular shape. The slinger 18 is externally fitted and fixed to the end portions of the inner rings 3 and 3 by interference fitting. There is. The seal ring 19 is made by attaching an elastic material 21 to a mandrel 20 formed by forming a metal plate into an annular shape with an L-shaped cross section, and supporting the elastic member 21 over the entire circumference. The outer ring 12 is internally fitted to both ends of the outer ring 12 by an interference fit so as to be internally fitted and fixed to both ends of the outer ring 12. In this state, the tip edges of the plurality of seal lips 22, 22 provided on the elastic member 21 are attached to the slinger 18,
Each is slid over the entire circumference.

Of the sealing devices 17 and 17a as described above, an encoder 23 is attached to the inner side surface of the slinger 18 which constitutes the inner sealing device 17a over the entire circumference.
Therefore, this slinger 18 corresponds to the cored bar described in claims 2 and 3. The encoder 23 is a permanent magnet such as a rubber magnet or a plastic magnet in which a ferromagnetic material such as ferrite is mixed in a polymer material such as rubber or synthetic resin, and is magnetized in the axial direction. is doing. The magnetizing directions are alternately changed at equal intervals in the circumferential direction. Therefore, the S poles and the N poles are alternately arranged in the circumferential direction on the inner surface, which is the detected surface of the encoder 23. Such an encoder 23 is supported and fixed to the inner surface of the circular ring portion 24 provided on the slinger 18 by adhesion.

On the other hand, the mounting hole 2 is formed in a part of the bearing case 13 that projects inward from the inner end surface of the outer ring 12.
5 is formed so as to penetrate the bearing case 13 in the radial direction. A sensor (not shown) for detecting the rotational speed can be freely attached to the mounting hole 25. And
The detection surface provided at the tip of this sensor can be opposed to the encoder 23 in the axial direction via a minute gap.

The rolling bearing unit 1 in which the encoder 23 is incorporated, which is constructed as described above, is the bearing case 13 described above.
The outer ring 12 is coupled and fixed to the suspension device by
A wheel is supported and fixed to the hub 2 by the flange 4. In this state, the wheel is rotatably supported by the suspension device. When the wheel rotates, the S near the detection surface of the sensor is present on the outer peripheral surface of the encoder 23.
The poles and the N poles pass alternately, and the output signal of the sensor changes. Since the frequency at which the output signal of the sensor changes is proportional to the rotation speed of the wheel, if this output signal is sent to a controller (not shown), the rotation speed of this wheel is obtained and the ABS and TCS are controlled appropriately. it can.

Encoder 23 constructed and operative as described above
In order to ensure the reliability of wheel rotation speed detection by the rolling bearing unit 1 incorporating the above, the encoder 2
It is necessary that the density of the magnetic flux emitted from the surface 3 to be detected is sufficiently high and does not significantly change other than the original change based on the change in the magnetization direction. On the other hand, the encoder 23, which is a rubber magnet or a plastic magnet, is partially called a weld because it is manufactured by injection molding in which a polymer material containing a magnetic material is injected into a cavity provided inside a mold. It is unavoidable that a seam of polymer materials occurs.

That is, at the time of injection molding, a polymer material containing the magnetic material is injected into the cavity through an injection port called a gate. The polymer material fed into the annular cavity to injection-mold the annular encoder 23 flows as indicated by an arrow in FIG. 6, and flows on the side opposite to the injection port in the circumferential direction. Butt each other. Then, the seam is generated at this abutting portion. The properties of such a joint are often different from those of other portions, and, for example, the ratio of the magnetic substance contained in the polymer material is reduced, or the orientation direction of the magnetic substance is likely to be different from the desired state. When the ratio of the magnetic substance decreases or the orientation direction becomes incorrect, the density of the magnetic flux emitted from the side surface of the seam portion after magnetization becomes low. This point will be described with reference to FIG.

FIG. 7 shows the distribution of the density of the magnetic flux emitted from the inner surface (detected surface) of the encoder 23 in the circumferential direction. Such (A) in FIG. 7 shows the distribution state of the portion in which the amount of the magnetic substance contained in the polymer material is sufficient and uniform and the orientation direction is proper.
If the distribution state of the magnetic flux density in the portion where the detection portions of the sensor face each other is as shown in FIG. 7A, the reliability of the rotation speed detection by the sensor can be sufficiently ensured. On the other hand, FIG. 7B corresponds to the weld,
It shows the distribution of magnetic flux density in the part where the properties are non-uniform in the circumferential direction due to the partial lack of the magnetic substance contained in the polymer material and the incorrect orientation direction. . If the distribution state of the magnetic flux density at the portion where the detection portion of the sensor faces is such a state as shown in FIG. 7B, the reliability of the rotation speed detection by the sensor may decrease.

That is, when the change (magnitude) of the magnetic flux density is small and the output change of the sensor corresponding to the change of the magnetic flux density does not exceed a predetermined threshold value, the control that accepts the output signal of this sensor is performed. Cannot detect the rotation of the encoder 23. Therefore, at the seam part, the above-mentioned FIG.
When the decrease in magnetic flux density occurs as shown in, the structure of the mold for injection molding is devised and the injection speed of the polymer material is adjusted in order to suppress (reduce) the degree of decrease. , Adjust the mixing ratio of the magnetic material in the polymer material,
It is necessary to devise the orientation state of this magnetic material. In order to take such a measure, it is necessary to know in which part the seam is generated and how much the magnetic flux density in this seam part is lower than in other parts. For this reason, conventionally, the position of the joint is confirmed by visually observing the encoder 23 after injection molding, and magnetized alternately in the circumferential direction (S poles and N poles are alternately arranged on the detected surface). )
After that, the change in the magnetic flux density on the surface to be detected of the encoder 23 is measured to measure the position of the seam and the extent to which the magnetic flux density decreases at the seam portion.

[0014]

The seam does not always appear clearly, and visual confirmation of the seam portion cannot always be performed accurately.
Even if the position of the seam can be accurately known, it cannot be known to the extent that the magnetic flux density is reduced at that position.
Also, when the change of the magnetic flux density of this detected surface is measured after S poles and N poles are alternately arranged on the detected surface of the encoder 23, the position of the seam portion cannot be accurately grasped. Moreover, it is not possible to accurately know the extent to which the magnetic flux density decreases at this joint. The reason for this is S
This is because the detected surface of the encoder 23, in which the poles and the N poles are alternately arranged, has a very low magnetic flux density, including a non-magnetized portion.

Considering, for example, the case where the distribution of the magnetic flux density on the surface to be detected becomes as shown in FIG. 7B based on the existence of the seam, the seam shown in FIG.
It can be seen that it exists within the range indicated by W in (B). However, it is not possible to specify at which position within the range W the seam is based only on the change in the magnetic flux density. Accordingly, it is not possible to grasp how much the magnetic flux density is reduced at the seam. The reason for this is that it is not clear whether the above-mentioned joint exists in the portion where the magnetic flux density should be high and the magnetic flux density in that portion is lower than the original value, or whether it is originally in the portion where it should be low. Therefore, even if a portion where the magnetic flux density is low corresponding to a predetermined phase can be confirmed, it is not possible to calculate how low the magnetic flux density is compared to the original magnetic flux density.

As described above, conventionally, it was not possible to accurately know the position of the seam of the polymer material due to the injection molding and the degree of decrease in the magnetic flux density at this seam, so that the seam of this seam was used. There was an inconvenience in taking sufficient measures to suppress the decrease in magnetic flux density. That is, since it is not possible to know the position and degree accurately, the structure of the mold for injection molding, which should be adopted to suppress the decrease in the magnetic flux density,
It is difficult to properly devise or adjust the injection rate of the polymer material, the mixing ratio of the magnetic material in the polymer material, the orientation state of the magnetic material, and the like. The encoder inspection method and the inspection magnetizing device of the present invention were invented in view of such circumstances.

[0017]

Of the encoder inspection method and inspection magnetizing apparatus of the present invention, the encoder inspection method described in claims 1 and 2 is a method in which a polymer material containing a magnetic material is injected and molded. , The magnetic material including the magnetic material is placed in a uniform magnetic field in the circumferential direction before the magnetic material is magnetized by alternately changing the magnetizing direction in the circumferential direction. Magnetize in the same direction with respect to the circumferential direction. Then, the density of the magnetic flux emitted from the polymer material containing the magnetic substance is measured.

In the encoder magnetizing device according to a third aspect of the present invention, the magnetic body is magnetized in order to magnetize the polymer material containing the magnetic body in the axial direction and in the same direction in the circumferential direction. A holder for holding a mandrel to which a polymer material containing the same is held, and a magnetizing yoke that moves perspectively with respect to the holder are provided. Then, this magnetizing yoke is on a plane that faces the polymer material containing the magnetic substance and is orthogonal to the center axis of the polymer material containing the magnetic substance, in the direction of the center axis, The axial end face of the magnetizing coil is installed to create a uniform magnetic field in the same direction with respect to the circumferential direction.

[0019]

According to the encoder inspection method and inspection magnetizing apparatus of the present invention configured as described above, the position of the seam of the polymer material accompanying injection molding and the magnetic flux density at this seam portion decrease. You can know the degree accurately. This point will be described with reference to FIG. By placing the polymer material containing the magnetic substance in a uniform magnetic field in the circumferential direction, the polymer material containing the magnetic substance is magnetized in the same direction in the circumferential direction, and the joint is not included. In the portion where the magnetic material is uniformly distributed in the polymer material, the magnetic flux density on the detected surface of the encoder is as shown in FIG.
As shown in (1), they are evenly distributed in the circumferential direction (left-right direction in FIG. 1).

On the other hand, as shown in FIG. 1B, the magnetic flux density of the surface to be detected including the seam becomes non-uniform as it becomes low at the seam portion. Since the detected surface of the encoder is magnetized by a uniform magnetic field over the entire circumference, if the distribution and orientation state of the magnetic material in the polymer material is uniform, the magnetic flux of the detected surface is The density distribution
It becomes uniform as shown in FIG. Therefore, as shown in FIG. 1B, if there is a portion where the magnetic flux density is low in a part of the surface to be detected, that position can be accurately specified as the position of the seam. Further, the extent to which the magnetic flux density at the portion where the magnetic flux density is low is lower than the magnetic flux density at other portions can be accurately grasped as the extent to which the magnetic flux density is reduced at the seam portion. Incidentally, FIG.
Shows the state in which the magnetic flux density of the portion magnetized to the N pole is measured, but it is not always necessary to measure the magnetic flux density of the N pole portion when implementing the present invention. Similar effects can be obtained by measuring the magnetic flux density of the S pole portion.

[0021]

FIG. 2 shows an example of an embodiment of a magnetizing device for inspecting an encoder according to the present invention. The inspection magnetizing device 26 includes a holder 27 and a magnetizing yoke 28 which are arranged concentrically with each other and can be moved relative to each other. The holder 27 holds the rubber magnet encoder 23 via the mandrel 37. The cylindrical part 29 formed on the inner peripheral edge of the mandrel 37 is a cylindrical part 30 which can be externally fitted and supported. A groove 31 and a flat surface portion 32 are provided around the periphery.
It is provided concentrically with the columnar portion 30. Groove 3 of these
In order to prevent interference between the cylindrical portion 29 and the holder 27, 1 is provided so that the cylindrical portion 29 can enter, and the flat surface portion 32 abuts the circular ring portion 24 of the mandrel 37.
It is formed in a direction orthogonal to the central axis of the holder 27. When magnetizing the encoder 23, the mandrel 2
0, the cylindrical portion 29 is externally fitted to the cylindrical portion 30 with a light interference fit, and the surface opposite to the surface on which the encoder 23 is affixed on both side surfaces of the circular ring portion 24 in the axial direction is flattened. Abut on the face portion 32.

On the other hand, the magnetizing yoke 28 is formed by installing a magnetizing coil 34 on an annular magnetizing block 33. The magnetizing block 33 has a circular hole 35 formed in the center thereof so that the cylindrical portion 30 of the holder 27 can be inserted therein.
A magnetizing plate 36 is provided on the periphery of 5. The magnetizing plate 36 is installed on a plane orthogonal to the central axes of the holder 27 and the magnetizing block 33, and has one surface (see FIG. 2).
Upper surface) of the holder 27 faces the flat surface portion 32 of the holder 27. Further, the magnetizing coil 34 is attached to the middle portion in the radial direction of the other surface (the lower surface in FIG. 2) of the magnetizing plate 36 over the entire circumference (an end surface of the magnetizing coil 34 in the axial direction). This magnetizing coil 34 (abutting (upper surface of FIG. 2))
Is a magnetic field in the direction indicated by the arrow in FIG.
Generates uniformly over the entire circumference.

The inspection magnetizing device 26 including the holder 27 and the magnetizing yoke 28 as described above enables the encoder 2 to be operated.
The operation of magnetizing No. 3 for inspection is performed as follows.
First, the cylindrical portion 29 of the mandrel 37 to which this encoder is attached
Is fitted onto the cylindrical portion 29 of the holder 27, and the circular ring portion 24 of the mandrel 37 is abutted against the flat surface portion 32. Next, the holder 27 is brought close to the magnetizing yoke 28, and one surface of the encoder 23 (lower surface in FIG. 2) to be the surface to be detected is butted against one surface of the magnetizing plate 36. In this state, the magnetizing coil 34 is energized to generate a uniform magnetic field in the circumferential direction around the magnetizing coil 34. In the illustrated example, the magnetizing coil 34 is
Since the encoder 23 faces the radially intermediate portion, the inner diameter portion and the outer diameter portion of the encoder 23 are magnetized in opposite directions, and the radially intermediate portion becomes a non-magnetized region.

Therefore, the holder 27 is separated from the magnetizing yoke 28, and the encoder 23 is separated from the holder 2.
After removing from 7, the magnetic flux density in the inner diameter portion or outer diameter portion of the detected surface of the encoder is continuously measured in the circumferential direction. Incidentally, as the portion for measuring the magnetic flux density in this manner, preferably, the portion facing the detecting portion of the sensor is used in the use state. In this case, the portion of the sensor facing the detecting portion is normally the radial center position. Therefore, preferably, in order to prevent this radial center position from becoming a non-magnetized region, the magnetizing coil 34 is located at the radial center part of the encoder 23, but at a position displaced from the radial center part. To face. FIG. 3 is a diagram showing the distribution of the magnetic flux density on the detected surface of the encoder 23 obtained by such measurement.

As is apparent from FIG. 3, the magnetic flux density on the surface to be detected of the encoder 23 is not completely uniform even if the seam portion is removed, but varies greatly outside the seam portion. There is no. On the other hand, the magnetic flux density at this joint portion drops more rapidly than that at the surrounding portion. Therefore, the position of the seam can be accurately specified by knowing the portion where the magnetic flux density sharply decreases as compared with the surrounding portion. Further, the extent to which the magnetic flux density at the portion where the magnetic flux density is low is lower than the magnetic flux density at other portions can be accurately grasped as the extent to which the magnetic flux density is reduced at the seam portion.

[0026]

As described above, according to the encoder inspection method and the inspection magnetizing apparatus of the present invention, the position of the seam generated by injection molding and the degree to which the magnetic flux density is reduced at this seam portion are determined. Can be accurately requested. Therefore, in order to suppress this decrease in magnetic flux density, the structure of the mold for injection molding, the injection rate of the polymeric material, the mixing ratio of the magnetic material in the polymeric material, the orientation state of this magnetic material, etc. The device or adjustment can be performed relatively easily and appropriately.
In order to know the position of the encoder seam and the extent to which the magnetic flux density decreases at this seam portion, it is only necessary to magnetize the portion of the encoder surface to be measured for this magnetic flux density. Good. Therefore, the same inspection magnetizing device can be used for encoders having slightly different diameters, and the cost required for the inspection does not increase.

[Brief description of drawings]

FIG. 1 is a diagram showing a theoretical distribution state of a magnetic flux density on a detected surface of an encoder for explaining the present invention.

FIG. 2 is a sectional view showing an example of an embodiment of a magnetizing device for inspecting an encoder of the present invention.

FIG. 3 is a diagram showing an example of the distribution state of the magnetic flux density on the surface to be detected of the encoder, which is actually measured when carrying out the present invention.

FIG. 4 is a cross-sectional view showing an example of a conventionally known rolling bearing unit incorporating a permanent magnet encoder.

FIG. 5 is an enlarged view of part A of FIG. 4 with a part omitted.

FIG. 6 is an abbreviated view for explaining the reason why weld occurs when an encoder is injection-molded.

FIG. 7 is a diagram showing a distribution state of magnetic flux density of an encoder after magnetization, (A) shows a distribution state of a portion where the distribution of the magnetic body is uniform, and (B) shows a distribution state of the magnetic body around the circumference. The diagram which shows the distribution state of the part which is non-uniform about a direction, respectively.

[Explanation of symbols]

1 Rolling bearing unit 2 hubs 3 inner ring 4 flange 5 spline holes 6 Inner ring track 7 constant velocity joint 8 spline shaft 9 Male thread 10 nuts 11 Housing part 12 outer ring 13 Bearing case 14 Outer ring track 15 rolling elements 16 cage 17, 17a Sealing device 18 Slinger 19 seal ring 20 Shinkin 21 Elastic material 22 seal lip 23 encoder 24 Circle part 25 mounting holes 26 Magnetizing device for inspection 27 holder 28 Magnetizing yoke 29 Cylindrical part 30 Column 31 groove 32 Flat surface 33 Magnetization block 34 Magnetizing coil 35 circular hole 36 Magnetizing plate 37 Shinkin

Claims (3)

[Claims] 1. A magnetic material-containing polymer material is injection-molded into an annular shape, and then the magnetic material-containing polymer material is magnetized by alternately changing the magnetization direction in the circumferential direction. A method for inspecting an encoder for inspecting the density of magnetic flux emitted from an encoder, which is, after injection molding a polymer material containing the magnetic material, before magnetizing by alternately changing the magnetizing direction in the circumferential direction, By placing the polymer material containing the magnetic material in a uniform magnetic field in the circumferential direction, the polymer material containing the magnetic material is magnetized in the same direction in the circumferential direction, and then the polymer material containing the magnetic material. The inspection method of the encoder that measures the density of the magnetic flux emitted from the. 2. A polymeric material containing a magnetic material injection-molded in an annular shape is attached to one axial surface of a circular ring portion forming a magnetic metal core, and the polymeric material containing the magnetic material is attached. A method for inspecting an encoder for inspecting the density of magnetic flux emitted from an encoder produced by alternately changing the magnetizing direction in the circumferential direction, the method comprising: , The magnetic material including the magnetic material is placed in a uniform magnetic field in the circumferential direction before the magnetic material is magnetized by alternately changing the magnetizing direction in the circumferential direction. A method for inspecting an encoder, which measures the density of magnetic flux emitted in the axial direction from a polymer material containing the magnetic substance after being magnetized in the same direction in the axial direction and in the circumferential direction. 3. When carrying out the encoder inspection method according to claim 2, an encoder inspection dressing in which a polymer material containing a magnetic material is magnetized in the axial direction and in the same direction with respect to the circumferential direction. A magnetic device and a holder for holding a mandrel attached with a polymer material containing a magnetic body, which is formed into an annular shape by injection molding, for forming an encoder, and a magnetizing yoke that moves in a perspective manner with respect to the holder. The magnetizing yoke is provided on a plane that faces the polymer material containing the magnetic substance and is in a direction orthogonal to the center axis of the polymer material containing the magnetic substance, in the direction of the center axis. A magnetizing device for inspecting an encoder, in which an axial end face of a magnetizing coil for creating a uniform magnetic field in the same direction with respect to the circumferential direction is installed.