JP2003042803A - Encoder and rolling bearing unit with encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a structure improving the distribution of the magnetic flux density of the side surface of an encoder 15a and capable of ensuring the reliability of a rotational speed at a low cost. SOLUTION: The thickness in the axial direction of the permanent magnet 17a constituting the encoder 15a is gradually changed in a radial direction so as to be reduced on the outer diameter side of the encoder 15a, and increased in the inner diameter side thereof. By this constitution, the magnetic flux density on the inner diameter side of the encoder 15a can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION An encoder and a rolling bearing unit with an encoder according to the present invention are used, for example, to detect the rotation speed of a wheel of an automobile or the rotation speed and rotation angle of a spindle of a machine tool.

[0002]

Rolling bearing units are used to rotatably support the wheels of an automobile relative to a suspension system.
Further, in order to control the antilock brake system (ABS) and the traction control system (TCS), it is necessary to detect the rotation speed of the wheels. In order to detect the rotation speed of a wheel for such a purpose, conventionally, rolling bearing units with an encoder having various structures are known. When magnetically detecting the rotational speed of the wheel, an encoder whose magnetic characteristics alternate 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 whose magnetic characteristics alternate in the circumferential direction in this way has a simple structure on the sensor side. Moreover, from the viewpoint of ensuring the reliability of the detected value at low speed, the number of cases where it is used in recent years is increasing.

4 to 6 show an example of a conventional structure of an encoder and a rolling bearing unit with an encoder used for the above purpose. The hub 1, which is a rotating wheel, is formed by coupling and fixing a hub body 2 and an inner ring 3. This hub body 2
Of the outer end (the end that is the outer side in the width direction when assembled to an automobile, the left end in FIG. 4) has a flange 4 on the outer peripheral surface for attaching and fixing the wheel, and the hub has the outer peripheral surface on the intermediate portion. The inner ring raceway 5a on the outer side (the left side in FIG. 4) of the double-row inner ring raceways 5a, 5b provided on the outer peripheral surface of 1 is referred to as the inner end (the end that is the center side in the width direction in the state of being assembled to an automobile). A small-diameter step portion 6 is formed at each of the right end portions of the portions 4.

The inner ring 3 is fitted onto the step portion 6 and fixed to the inner end portion of the hub body 2 by a nut 8 screwed to a male screw portion 7 formed on the inner end portion of the hub body 2. is doing. On the outer peripheral surface of the inner ring 3 as described above, the inner ring raceway 5b on the inner side (the right side in FIG. 4) of the double-row inner ring raceways 5a and 5b provided on the outer peripheral surface of the hub 1 is provided. A plurality of rolling elements 11, 11 are respectively held between the inner ring raceways 5a, 5b and the double-row outer ring raceways 10, 10 provided on the inner peripheral surface of the outer ring 9 which is a stationary wheel. Bowl 12, 12
And the hub 1 is rotatably supported inside the outer ring 9 in the radial direction. An outer flange 9 is provided with an outward flange-shaped mounting portion 13 so that the outer ring 9 can be coupled to and supported by a suspension device such as a knuckle. Although balls are used as the rolling elements 11 in the illustrated example, tapered rollers may be used as these rolling elements in the case of rolling bearing units for automobiles that are heavy.

The inner ring raceway 5 is formed at the inner end of the inner ring 3.
An annular encoder 15 is fixed to the shoulder 14 located axially inward (the left-right direction in FIGS. 1, 3 to 6) with respect to b. The encoder 15 includes a core metal 16 and a permanent magnet 17
It consists of and. The core metal 16 is formed by pressing a ferromagnetic metal plate such as a mild steel plate such as SPCC into an annular shape with an L-shaped cross section.
And an annular portion 19 that is bent outward in the radial direction from the axial end (right end in FIGS. 1, 3 to 6) of the cylindrical portion 18. The permanent magnet 17 is made of a polymer elastic material such as rubber mixed with powder of a ferromagnetic material such as ferrite, and is magnetized in the axial direction. The magnetizing directions are alternately changed at equal intervals in the circumferential direction. Therefore, the S poles and the N poles are alternately arranged at equal intervals on the axial side surface of the permanent magnet 17. Encoder 1 like this
5 is fixed to the inner ring 3 by externally fitting the cylindrical portion 18 to the shoulder portion 14 by interference fitting. still,
In the case of the illustrated example, the hook portion 20 formed on the outer peripheral edge portion of the permanent magnet 17 is locked to the outer peripheral edge portion of the circular ring portion 19 to improve the bonding strength between the permanent magnet 17 and the core metal 16. We are trying to improve.

A gap between the outer end (left end in FIG. 4) of the outer ring 9 and the outer peripheral surface of the intermediate portion of the hub 1 is closed by a seal ring 21. On the other hand, the inner end (right end in FIG. 4) opening of the outer ring 9 is closed by a cover 22. This cover 22 is formed by plastically deforming a metal plate such as a stainless steel plate or a mild steel plate by drawing or the like, or by molding a synthetic resin to form a cylindrical shape with a bottom. The inner end opening of the outer ring 9 is closed by fitting the end opening to the inner end of the outer ring 9 by interference fitting. Incidentally, in place of the cover 22, there is a case where a known combination seal ring in which a slinger in which an encoder is assembled and a seal ring are combined is used.
In this case, the seal ring is fitted on the inner peripheral surface of the inner end of the outer ring 9 and the slinger is fitted on the outer peripheral surface of the inner end of the inner ring 3. Then, the seal lip forming the seal ring is slidably contacted with the slinger (core metal) to which the encoder is assembled, thereby closing the inner end opening of the outer ring 9.

In the case of the illustrated example, one side surface of the permanent magnet 17 (a right side surface in FIG. 4) which is a surface to be detected of the encoder 15 is a part of the bottom plate portion 23 constituting the cover 22.
The sensor 25 is provided in the through hole 24 formed in the portion facing the sensor 25.
I support you. When the combination seal ring is used instead of the cover 22, the sensor 2
5 is supported by a knuckle or the like (not shown) that constitutes the suspension device. The sensor 25 has a well-known structure including a magnetic sensing element such as a Hall element or a magnetoresistive element, and an IC incorporating a waveform shaping circuit for shaping an output signal of the magnetic sensing element, and its tip is provided. The surface (the left end surface in FIG. 4) is the detection surface. In such a sensor 25, this detection surface is, for example, 0.5 to 1 mm on the detected surface of the encoder 15.
They are opposed to each other with a small gap. In the sensor 25 as described above, the characteristics of the magnetic sensing element are changed at the moment when the detection surface faces the S pole and the N pole arranged on one side surface of the permanent magnet. Use
Get the output signal.

The encoder and the rolling bearing unit with an encoder configured as described above support the wheel rotatably with respect to the suspension device in the following manner, and the rotational state of the wheel such as the rotational speed and the rotational amount. To detect. That is, at the time of assembling to an automobile, the outer ring 9 is attached and fixed to a knuckle (not shown) constituting the suspension device by the attachment portion 13 fixed to the outer peripheral surface of the outer ring 9. Further, the wheel is fixed to the flange 4 provided on the outer peripheral surface of the outer end portion of the hub 1.

In this state, when the hub 1 rotates together with the wheels and the encoder 15 supported by the hub 1 rotates, the permanent magnet 17 constituting the encoder 15 is located near the detection surface of the sensor 25. The S poles and N poles arranged on one side pass alternately. As a result, the characteristics of the magnetic sensing element change. That is, when the direction of the magnetic flux passing through the magnetic detection element changes, the characteristics of the magnetic detection element change, and the output signal of the sensor 25 incorporating the magnetic detection element also changes. The frequency at which the output signal of the sensor 25 changes is proportional to the rotation speed of the encoder 15. Therefore, if such an output signal of the sensor 25 is sent to a controller (not shown), ABS and TCS can be controlled appropriately.

[0010]

In order to secure the reliability of the rotation speed detection while suppressing the cost increase of the sensor 25,
It is necessary to set the amplitude of the change in the output signal of the magnetic sensing element to a predetermined magnitude or more. For this purpose, it is necessary to increase the change in the magnetic flux in the detected portion of the encoder 15 for changing the output of the magnetic detection element, particularly in the portion facing the detection portion of the sensor 25. In order to increase the change in the magnetic flux, it is necessary to increase the magnetic flux density of the encoder 15 at the portion where the detecting portion of the sensor 25 faces.

On the other hand, the density of the magnetic flux emitted from the side surface of the encoder 15 varies depending on the radial position of the encoder 15, as shown in FIG. That is, the magnetic flux density on the inner diameter side of the encoder 15 is lower than that on the outer diameter side. The reason for this will be described with reference to FIG. The permanent magnet 17 constituting the encoder 15 is, as shown in FIG.
Since the whole is formed in a ring shape and the S poles and the N poles are alternately arranged in the circumferential direction, the shapes of the S poles and the N poles are fan-shaped. Therefore, since the areas of the S pole and the N pole are smaller on the inner diameter side than on the outer diameter side, the magnetic flux density on the inner diameter side of the encoder 15 to which the permanent magnet 17 is attached is lower than on the outer diameter side. Further, in the portion near the outer peripheral edge, the magnetic flux density decreases as it approaches the outer peripheral edge.

As a result, the width of the portion of the side surface of the encoder 15 having a high magnetic flux density in the radial direction becomes small.
The detection portion of the sensor 25 has a width in the radial direction of the encoder 15. Therefore, as shown in FIG. 7, it is not preferable that the distribution of the magnetic flux density of the encoder 15 is non-uniform in the radial direction from the viewpoint of stably detecting the rotation speed. In view of such circumstances, the present invention has been made to widen the range of a portion where the magnetic flux density is high on the side surface of the encoder.

[0013]

Of the encoder and the rolling bearing unit with an encoder according to the present invention, the encoder according to claim 1 is formed into a circular ring shape as in the conventional structure described above, and has a circumferential direction. With respect to, a permanent magnet having S poles and N poles alternately arranged is provided. Particularly, in the encoder of the present invention, the thickness of the permanent magnet in the axial direction is gradually changed in the radial direction so that the thickness becomes thinner on the outer diameter side and thicker on the inner diameter side.

Further, the rolling bearing unit with an encoder according to a fourth aspect of the present invention has a stationary side raceway on the stationary side circumferential surface, which does not rotate during use, and a stationary side circumferential surface, as in the conventional structure. Has a rotation-side orbit on the rotation-side peripheral surface facing
A rotating wheel that rotates during use, a plurality of rolling elements that are rotatably provided between the rotating side raceway and the stationary side raceway, a core metal supported by the rotary wheel, and the core metal. And an encoder configured by supporting a permanent magnet. Particularly, in the rolling bearing unit with an encoder of the present invention, as described above, the encoder has a thickness of the permanent magnet that is thin on the outer diameter side and thick on the inner diameter side.
This thickness is gradually changed in the radial direction.

[0015]

The basic operation for detecting the rotational speed by the encoder and the rolling bearing unit with an encoder of the present invention configured as described above is the same as that of the conventional structure described above. In particular, of the encoder and the rolling bearing unit with an encoder of the present invention, the encoder described in claim 1 is such that the axial thickness of the permanent magnet constituting the encoder is thin on the outer diameter side and thick on the inner diameter side. As described above, since the thickness is gradually changed in the radial direction, the width of the portion having a high magnetic flux density can be widened as compared with the encoder having the conventional structure.
That is, since the magnetic flux density is affected by the thickness as well as the area of the permanent magnet, the magnetic flux density on the inner diameter side can be increased by increasing the thickness of the permanent magnet at the inner diameter side portion having a small area. As a result, it is possible to increase the magnetic flux density in almost the entire width of the portion where the detecting portion of the sensor faces, and to secure the reliability of the rotation speed detection.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first example of an embodiment of the present invention corresponding to claims 1 and 2. The encoder 15a of this example is formed by combining a core metal 16a and a permanent magnet 17a, as in the conventional structure described above. Of these, the core metal 16a is formed by pressing a ferromagnetic metal plate such as a mild steel plate such as SPCC into an annular shape with an L-shaped cross section.
And a circular ring portion 19a bent at a right angle outward in the radial direction from one end edge (right end edge in FIG. 1) in the axial direction (left and right direction in FIG. 1). The permanent magnet 17a is made by mixing powder of a ferromagnetic material such as ferrite in a polymeric elastic material such as rubber and is magnetized in the axial direction. The magnetizing directions are alternately changed at equal intervals in the circumferential direction. Therefore, the S poles and the N poles are alternately arranged at equal intervals on the axial side surface of the permanent magnet 17a. Such an encoder 15a is fixed to the inner ring 3 (see FIG. 4) by fitting the cylindrical portion 18 onto the shoulder portion 14 by interference fitting.
In the case of the illustrated example, the hook 20 formed on the outer peripheral edge of the permanent magnet 17a is locked to the outer peripheral edge of the annular portion 19a to join the permanent magnet 17a and the core metal 16a. We are trying to improve the strength.

In particular, in the case of this example, the permanent magnet 17 is used.
The thickness of a is gradually changed in the radial direction so that the thickness in the axial direction is thin on the outer diameter side and thick on the inner diameter side.
That is, of the axially opposite side surfaces of the permanent magnet 17a, the side surface opposite to the circular ring portion 19a (the right surface in FIG. 1), which is the surface to be detected, is the plane that exists in the direction perpendicular to the central axis. On the other hand, the other side surface (the left surface in FIG. 1), which is the surface attached to the circular ring portion 19a, is a conical convex surface inclined in a direction in which the axial thickness is thin on the outer diameter side and thick on the inner diameter side. The slanted surface 26 has a shape. Further, the axial thickness of the circular ring portion 19a forming the core metal 16a is also gradually changed in the radial direction. That is, a conical concave inclined surface 27 that is inclined at the same angle as the inclined surface 26 is formed on the surface of the circular ring portion 19a to which the permanent magnet 17a is attached.
The axial thickness of 9a is thicker on the outer diameter side and thinner on the inner diameter side.

The encoder 15 of the present example configured as described above
For example, a is incorporated into a rolling bearing unit as shown in FIG. 4 described above to form a rolling bearing unit with an encoder. With such a rolling bearing unit with an encoder, the action for supporting the wheel rotatably with respect to the suspension device and detecting the rotation speed of the wheel is similar to that of the conventional rolling bearing unit with an encoder. .

Particularly, in the encoder 15a of the present invention, the thickness of the permanent magnet 17a constituting the encoder 15a in the radial direction is set so that the thickness of the permanent magnet 17a in the axial direction is thin on the outer diameter side and thick on the inner diameter side. Since the magnetic flux density is gradually changed, the magnetic flux density on the inner diameter side can be increased as compared with the encoder 15 having the conventional structure. FIG. 2 shows the distribution of the magnetic flux density in the radial direction of the encoder 15a. Comparing FIG. 2 with FIG. 7 described above, the encoder 15a of the present example has a higher magnetic flux density on the inner diameter side and the width of the high magnetic flux density portion is wider than that of the encoder 15 of the conventional structure. I understand things. That is,
Since the strength of the magnetic flux density is influenced not only by the area of the permanent magnet 17a but also by the thickness of the permanent magnet 17a, if the thickness of the permanent magnet 17a is increased at the inner diameter side portion having a small area, The magnetic flux density can be increased. As a result, the encoder 15
On the side surface of a, the magnetic flux density of the portion where the detection portion of the sensor 25 (FIG. 4) faces is increased in most of this portion, and the reliability of rotation speed detection can be secured.

Further, in the case of this example, since the inclined surface 27 is formed by recessing the surface of the circular ring portion 19a to which the permanent magnet 17a is attached, the inner diameter side of the permanent magnet 17a is thickened. However, it is possible to prevent the axial direction of the encoder 15a from increasing. Therefore, the sensor 25 (FIG. 4)
Even if the permanent magnet 17a and the sensor 25 are incorporated in a small rolling bearing unit such that the distance between the permanent magnet 17a and the sensor 25 is short, the interference does not occur.

Next, FIG. 3 corresponds to claims 1 and 3,
The 2nd example of embodiment of this invention is shown. In the case of the encoder 15b of this example, the permanent magnet 17a is attached to the core metal 16b.
The circular ring portion 19 is formed so that one side surface (the right side surface in FIG. 2) of the permanent magnet 17a becomes a flat surface orthogonal to the axial direction in the state where the permanent magnet 17a is attached.
b is inclined with respect to this one side surface. That is, in the core metal 16b, the circular ring portion 19b is not bent at a right angle from one end edge of the cylindrical portion 18, but is bent to an angle parallel to the inclined surface 26 constituting the other side surface of the permanent magnet 17a. The permanent magnet 1 is attached to the side surface of the circular ring portion 19b.
The encoder 15b is configured by attaching the inclined surface 26 of 7a. In the case of this example, since it is configured in this way, the structure of the core metal can be made simpler than in the case of the above-described first example, and an increase in manufacturing cost can be suppressed. However, the first
Since the dimension in the axial direction is slightly larger than that of the encoder 15a in the example, it may not be suitable for a small rolling bearing unit in which the distance from the sensor 25 (FIG. 4) becomes short. Other configurations and operations are similar to those in the case of the first example described above.

The first embodiment of the present invention described above,
In order to obtain the axial thickness of each radial portion of the permanent magnet 17a that constitutes the encoders 15a and 15b shown in the two examples,
The optimum thickness can be obtained by using the SNR magnetic flux density calculation program. That is, this program
If the cross-sectional shape of the permanent magnet is obtained so that the magnetic flux density of the portions where the detecting portions of the sensor face each other becomes uniform, it is possible to obtain an encoder that can detect rotation speed without waste and with high reliability.

Further, the encoder of the present invention can be applied to an outer ring rotating type rolling bearing unit in which a rotating wheel is an outer ring. In this case, the circular ring portion of the core metal is bent inward in the radial direction from one axial end of the cylindrical portion. And
Similar to the above-described inner ring rolling bearing unit, a permanent magnet is attached to the side surface of the circular ring portion over the entire circumference, and the cylindrical portion is fitted in the outer ring. Other configurations and operations are similar to those of the above-described first and second examples of the embodiment of the invention.

[0024]

Since the encoder and the rolling bearing unit with an encoder of the present invention are configured and operate as described above, it is possible to improve the reliability of the detection accuracy of the rotation speed while suppressing the cost increase.

[Brief description of drawings]

FIG. 1A in FIG. 5 shows a first example of an embodiment of the present invention.
Sectional drawing corresponded to a part.

FIG. 2 is a diagram showing the distribution of magnetic flux density in the radial direction of the encoder of the present invention.

FIG. 3 is a view similar to FIG. 1, showing a second example of the embodiment of the present invention.

FIG. 4 is a sectional view showing an example of a conventional rolling bearing unit with an encoder.

5 is a partial cross-sectional view showing only the encoder shown in FIG.

FIG. 6 is an enlarged view of part A in FIG.

FIG. 7 is a diagram showing a distribution of magnetic flux density in a radial direction of an encoder having a conventional structure.

FIG. 8 is a view on arrow B of FIG.

[Explanation of symbols]

1 hub 2 hub body 3 inner ring 4 flange 5, 5a, 5b Inner ring raceway 6 steps 7 Male thread 8 nuts 9 outer ring 10 Outer ring track 11 rolling elements 12 cage 13 Mounting part 14 Shoulder 15, 15a, 15b encoder 16, 16a, 16b Core bar 17, 17a Permanent magnet 18 Cylindrical part 19, 19a, 19b Circle part 20 Hook 21 seal ring 22 cover 23 Bottom plate 24 through holes 25 sensors 26 Inclined surface 27 slope

Claims (4)

[Claims] 1. An encoder provided with a permanent magnet, which is formed in a circular ring shape as a whole and in which S poles and N poles are alternately arranged in a circumferential direction, wherein the axial thickness of the permanent magnet is An encoder characterized in that the thickness is gradually changed in the radial direction so that it becomes thinner on the radial side and thicker on the inner diameter side. 2. A permanent magnet, and a cored bar which is formed into an annular shape as a whole and is composed of a cylindrical portion and a circular ring portion bent at a right angle from one end edge of the cylindrical portion. In an encoder which is attached and supported on the side surface of the circular ring portion over the entire circumference, one side surface of the permanent magnet is parallel to an imaginary plane orthogonal to the axial direction with the permanent magnet attached. The encoder according to claim 1, wherein the axial thickness of the circular ring portion is gradually changed in the radial direction. 3. A permanent magnet, and a cored bar which is formed in an annular shape as a whole and has a cylindrical portion and a circular ring portion bent from one end edge of the cylindrical portion. In an encoder that is attached and supported on the side surface of the ring portion, the circular ring portion is attached to the virtual surface such that one side surface of the permanent magnet is parallel to a virtual plane orthogonal to the axial direction with the permanent magnet attached. The encoder of claim 1 tilted with respect to a plane. 4. A stationary wheel having a stationary side track on the stationary side peripheral surface, which does not rotate even during use, and a rotating side track on the rotating side peripheral surface facing the stationary side peripheral surface, which rotates during use. A rotating wheel, a plurality of rolling elements rotatably provided between the rotating side raceway and the stationary side raceway, a core metal supported by the rotary wheel, and a permanent magnet supported on the core metal. A rolling bearing unit with an encoder, comprising: an encoder according to claim 1, wherein the encoder is the encoder according to any one of claims 1 to 3.