JP2006058256A - Rotation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a structure which can ensure the magnitude of the output variation of a sensor 5b, even when the pitch where the magnetic characteristics of the surface to be detected of a tone wheel 4a is varied is shortened. <P>SOLUTION: A magnetic flux convergence element 18, made of a magnetic material for making a magnetic flux supplied from a permanent magnet 15 to a magnetic detection element 17 concentrated, is installed in between the permanent magnet 15 and the magnetic detection element 17 constituting the sensor 5b. According to this constitution, the amount of the magnetic flux passing through the magnetic detection element 17 is increased, and the degree of variations in the magnetic flux, passing through the magnetic detection element 17, corresponding to the variation in the magnetic characteristic of the surface to be detected of the tone wheel 4a, can be enlarged. As a result, the output signal of the sensor 5b is varied by a large amount, and the value of a rotating member, such as rotational speed, rotational angle, or the like related to the rotation of the rotational member can be obtained precisely. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The rotation detection device according to the present invention is incorporated in, for example, a rolling bearing unit for supporting a wheel of an automobile and used for detecting the rotation speed or the rotation amount (rotation angle) of the wheel of the automobile. Further, it is incorporated in a movable part of various machine devices such as a machine tool and used for obtaining the moving speed or moving amount of the movable part.

  A rolling bearing unit is used to rotatably support the wheels of the automobile with respect to the suspension system. Further, in order to control the anti-lock brake system (ABS) and the traction control system (TCS), it is necessary to detect the rotational speed of the wheel. For this reason, in recent years, it has been possible to support the wheel rotatably with respect to the suspension device and to detect the rotational speed of the wheel by a rolling bearing unit with a rotation detection device in which a rotation detection device is incorporated in the rolling bearing unit. It has become widely practiced.

  5-6 shows what was described in patent document 1 as an example of the conventional structure of the rolling bearing unit with a rotation detection apparatus used for such a purpose. This rolling bearing unit with a rotation detection device rotatably supports a hub 2 and an inner ring 3 that are rotating members on an inner diameter side of an outer ring 1 that is a stationary member that does not rotate. The rotational speed of the tone wheel 4 fixed to a part of the hub 2 can be detected by a sensor 5 supported on the outer ring 1.

  That is, double row outer ring raceways 6 and 6 are formed on the inner peripheral surface of the outer ring 1, and a coupling flange 7 is formed on the outer peripheral surface. On the other hand, a mounting flange 8 is formed on a part of the outer peripheral surface of the hub 2 protruding from the outer end opening of the outer ring 1. Inner ring raceways 9 and 9 are formed on the outer peripheral surface of the intermediate portion of the hub 2 and the outer peripheral surface of the inner ring 3 that is fitted and fixed to the inner end portion of the hub 2. A plurality of rolling elements 10 and 10 are provided between the inner ring raceways 9 and 9 and the outer ring raceways 6 and 6, respectively, so as to be freely rollable.

  In order to incorporate the rotation detection device into the rolling bearing unit as described above, the tone wheel 4 is fitted and fixed to the inner end of the inner ring 3. In the case of the illustrated example, the tone wheel 4 is formed in an annular shape with an L-shaped cross section by performing plastic working on a magnetic metal plate such as a mild steel plate. Then, by forming a large number of through holes in the ring portion 12 of the tone wheel 4 at equal intervals in the circumferential direction, the magnetic characteristics of the ring portion are changed alternately and at equal intervals in the circumferential direction. I am letting. A synthetic resin sensor holder 14 that embeds and supports the sensor 5 is supported and fixed to a cover 13 fitted and fixed to the inner end opening of the outer ring 1. In this state, the detection unit of the sensor 5 is opposed to the inner side surface, which is the detection surface, of the circular ring part 12 constituting the tone wheel 4 in the axial direction via a minute gap.

  When the rolling bearing unit with a rotation detecting device configured as described above is used, the coupling flange 7 provided on the outer circumferential surface of the outer ring 1 is coupled and fixed to the suspension device, and the mounting flange 8 provided on the outer circumferential surface of the hub 2. The wheel is supported and fixed. In this state, when the tone wheel 4 rotates together with the wheel, the frequency of the output signal of the sensor 5 changes according to the rotational speed of the tone wheel 4. Therefore, if the output signal of the sensor 5 is sent to a controller (not shown), ABS and TCS can be appropriately controlled.

  In Patent Document 2, as shown in FIGS. 7 to 8, a tone wheel 4 a is fitted and fixed to the outer peripheral surface of the inner ring 3 that is a rotating member, and a sensor 5 a is attached to an axially intermediate portion of the outer ring 1 a that is a stationary member. Is a rolling bearing unit with a rotation detection device, in which the outer ring 1a is supported and fixed in a state of passing through the outer ring 1a in the radial direction. In the case of the second example of this conventional structure, gear-shaped irregularities are formed on the outer peripheral surface which is the detected surface of the tone wheel 4a. And the detection part of the said sensor 5a is made to oppose to this outer peripheral surface in the radial direction through a micro clearance gap.

  For example, conventionally, a passive type and an active type are widely known as the magnetic detection type sensors 5 and 5a constituting the rotation detection device incorporated in the rolling bearing unit as described above. Among these sensors, the passive type sensor induces a voltage in the coil in response to a change in magnetic flux, and obtains this change in voltage as an output signal. In the active type, the characteristics of magnetic detection elements such as a Hall element and a magnetoresistive element are changed in response to a change in magnetic flux, and an output signal corresponding to the change in the characteristics is obtained.

  Of these, the active type sensor can be configured smaller than the passive type sensor, and can obtain a stable output regardless of the rotational speed of the tone wheel. . The active type sensor includes a permanent magnet and a magnetic detection element that allows a magnetic flux supplied from the permanent magnet to pass therethrough and changes its characteristics in accordance with the density of the passing magnetic flux. When the tone wheel rotates with such an active sensor facing the detected surface of the magnetic tone wheel, the distance between the magnetic detecting element and the ferromagnetic portion of the detected surface is as follows. In a shortened state, the density of the magnetic flux passing through this magnetic detection element increases. On the other hand, the density of the magnetic flux passing through the magnetic detection element is lowered in a state where the distance between the magnetic detection element and the ferromagnetic portion of the detected surface is increased. As described above, the characteristics of the magnetic detection element change in accordance with the density of the passing magnetic flux. Therefore, if the change in the characteristic is converted into an electric signal by an appropriate processing circuit such as a bridge circuit, the tone wheel An output signal corresponding to the rotation speed of can be obtained.

  By the way, there are a method for obtaining the rotational speed of the tone wheel based on the output change of the sensor, a method for obtaining it based on the cycle of change, and a method for obtaining it based on the frequency of change. Of these, in order to employ a method that is determined in accordance with the period of change and increase the responsiveness relating to the detection of the rotational speed, it is necessary to shorten the pitch at which the magnetic characteristics of the detected surface of the tone wheel change. In addition, the pitch needs to be shortened when a method for obtaining the frequency is adopted to increase the accuracy (resolution) related to the detection of the rotational speed. In recent years, there has been an increasing demand for higher responsiveness and detection accuracy in response to higher performance of ABS and TCS. In addition, in order to enable feed-forward control of these ABS and TCS, the revolution speed of the rolling element constituting the wheel bearing rolling bearing unit is obtained as the rotation speed of the cage holding the rolling element, and this holding is performed. It is also considered to obtain a load applied to the wheel bearing rolling bearing unit based on the rotational speed of the vessel. In such a case, the amount of change in the rotational speed of the cage corresponding to the load change is small. For this reason, it is particularly necessary to shorten the pitch (increase the number of characteristic changes over the entire circumference of the detected surface) as compared with the case of the conventional rotation detection device in order to increase the resolution related to rotation speed detection. .

  However, if the pitch is shortened while using the same sensor as that of the conventional structure, the degree of change in output of the sensor is reduced, and there is a possibility that the rotational speed cannot be detected accurately. This is because the proportion of the magnetic flux supplied from the permanent magnet built in the active sensor increases without passing through the magnetic detection element. That is, the diameter of the permanent magnet cannot be made too small in order to ensure the amount of magnetic flux. For this reason, when the pitch related to the change in the magnetic characteristics existing on the detection surface of the tone wheel is reduced, as shown in FIG. 9, one end surface in the magnetization direction of the permanent magnet 15 (the lower end surface in FIG. 9) is the tone wheel 4a. It faces the range corresponding to a plurality of pitches of the detected surface. For example, when a large number of convex portions 16 and 16 are arranged on the detected surface at equal intervals in the circumferential direction, one end surface of the permanent magnet 15 in the magnetization direction is a convex portion facing the magnetic detection element 17. It will be in the state which opposed not only 16 but the convex parts 16 and 16 adjacent to the circumferential direction. In this state, a considerable portion of the magnetic flux emitted from one end surface of the permanent magnet 15 in the magnetization direction flows directly to the convex portions 16 and 16 adjacent in the circumferential direction and passes through the magnetic detection element 17. The amount of magnetic flux to be reduced is reduced.

  As a result, regardless of the rotation of the tone wheel 4a, the amount of change in the magnetic flux passing through the magnetic detection element 17 is reduced, and the degree of change in the characteristics of the magnetic detection element 17 is reduced. It becomes difficult to ensure the reliability of rotation speed detection. This tendency becomes significant when the measurement gap, which is the distance between the magnetic detection element 17 and the detection surface of the tone wheel 4a, is large. Incidentally, if the diameter of the permanent magnet 15 is reduced in accordance with the decrease in the characteristic change pitch of the surface to be detected, the amount of magnetic flux that flows without passing through the magnetic detection element 17 can be reduced. However, since the amount of magnetic flux passing through the magnetic detection element 17 itself is reduced, it is difficult to accurately measure the rotational speed of the tone wheel 4a.

Japanese Utility Model Publication No. 7-31539 JP-A-8-94657

  The rolling bearing unit with a rotation detection device of the present invention takes the above-described circumstances into consideration, even when the pitch at which the magnetic characteristics of the detected surface of the tone wheel made of magnetic material changes is shortened, The invention was invented to realize a structure capable of ensuring the magnitude of the output change of the sensor opposed to.

The rotation detection device of the present invention includes a tone wheel and a sensor.
Of these, the tone wheel has a surface to be detected in which the magnetic characteristics are alternately changed in the circumferential direction. And it is supported by the rotating member in a state where the center of the detected surface and the center of rotation coincide.
The sensor is supported by a stationary member that does not rotate adjacent to the rotating member. The output signal is changed as the tone wheel rotates.
The sensor includes a permanent magnet and a magnetic detection element that allows a magnetic flux supplied from the permanent magnet to pass therethrough and changes its characteristics in accordance with the density of the passing magnetic flux.
In particular, in the rotation detection device of the present invention, the permanent magnet is disposed between one end surface of the permanent magnet in the magnetizing direction and one end surface of the both end surfaces of the magnetic detection element in the magnetic flux passing direction. A magnetic flux concentrating element made of a magnetic material is provided for concentrating the supplied magnetic flux on the magnetic detecting element.

In the case of the rotation detection device of the present invention configured as described above, the magnetic flux entering and exiting from one end surface in the magnetization direction of the permanent magnet is guided to the magnetic flux focusing element and flows to the magnetic detection element. For this reason, regardless of the difference between the area of the one end face in the magnetization direction and the area of the magnetic detection element, the magnetic flux entering and exiting from the one end face in the magnetization direction passes through the magnetic detection element in a concentrated manner.
Therefore, the amount of magnetic flux passing through the magnetic detection element can be increased to increase the degree of change in magnetic flux passing through the magnetic detection element corresponding to the change in magnetic characteristics of the detection surface of the tone wheel. As a result, the output signal of the sensor is greatly changed, and values relating to the rotation of the rotating member, such as the rotation speed and rotation angle of the rotating member, can be accurately obtained.
In particular, the ratio of the magnetic flux flowing without passing through the magnetic detection element out of the magnetic flux entering and exiting from the one end face in the magnetization direction even when the pitch related to the change in the magnetic characteristics of the detection surface of the tone wheel is shortened. The value relating to the rotation of the rotating member can be accurately obtained while keeping it small.

In carrying out the present invention, preferably, as described in claim 2, the magnetic flux converging element has a large area on one end side in contact with one end surface in the magnetization direction of the permanent magnet, and the magnetic flux passing through the magnetic detecting element is passed. The area on the other end side that abuts on one end surface in the direction is narrow, and the cross-sectional area gradually decreases from the one end side toward the other end side.
As such a shape, for example, a truncated cone shape or a substantially truncated cone shape, a truncated cone shape, or a substantially truncated cone shape can be considered.
If the magnetic flux converging element has the shape as described above, the magnetic flux entering and exiting from one end surface in the magnetization direction of the permanent magnet can be efficiently guided to the magnetic detection element, and the output signal of the sensor can be greatly changed.

Further, when the present invention is implemented, preferably, the area on the other end side of the magnetic flux focusing element is made wider than the area where the magnetic flux supplied from the permanent magnet is saturated. In other words, among the magnetic flux focusing elements, the density of the magnetic flux passing through the end surface on the other end side where the magnetic flux passage area is the smallest is suppressed to be equal to or lower than the magnetic saturation density related to the magnetic material constituting the magnetic flux focusing element.
With this configuration, almost the entire amount of the magnetic flux that enters and exits from one end surface of the permanent magnet in the magnetization direction and passes through the magnetic flux converging element can be guided to the magnetic detection element. In other words, of the magnetic flux that has entered the magnetic flux focusing element from the one end surface in the magnetization direction, the leakage magnetic flux that leaks out of the magnetic flux focusing element can be reduced. In addition, when the amount of magnetic flux that flows through the magnetic flux focusing element changes based on the change in characteristics of the detection surface of the tone wheel, the magnetic flux that passes through the magnetic detection element is changed reliably, and the sensor output The signal can be changed greatly.

Preferably, when carrying out the present invention, preferably, the width dimension of the other end side of the magnetic flux focusing element in the circumferential direction of the tone wheel is set to a detected surface of the tone wheel. The magnetic characteristics are made smaller than ½ of the changing pitch.
If comprised in this way, it can prevent more effectively that the magnetic flux which comes in / out from the other end side of the said magnetic flux focusing element flows into the said to-be-detected surface, without passing a magnetic detection element. The amount of magnetic flux passing through the magnetic detection element is secured, the degree of change in the characteristics of the magnetic detection element is increased, and the output signal of the sensor can be changed greatly.

When the present invention is implemented, preferably, as described in claim 5, the other end surface of the both ends of the magnetic detection element in the direction of magnetic flux is made of a magnetic material, and the other end surface is formed on the other end surface. A second magnetic flux concentrating element is provided in which the area of the proximal end surface in contact is large and the area of the distal end surface on the opposite side is small. Then, the front end surface of the second magnetic flux focusing element is made to face the detected surface of the tone wheel. In other words, the magnetic detection element is sandwiched between the magnetic flux focusing element and the second magnetic flux focusing element from both sides of the magnetic flux flow direction.
If comprised in this way, the area of the front end surface of said 2nd magnetic flux concentrating element facing the said to-be-detected surface can be made still smaller than the area of the said magnetic detection element. Even if the pitch relating to the change in the magnetic characteristics of the detection surface of the tone wheel is made smaller, the proportion of the magnetic flux that flows without passing through the magnetic detection element can be kept small. For this reason, the improvement of the measurement accuracy regarding the rotation of the tone wheel and the securing of the magnitude of the output signal change of the sensor can be achieved at a higher level.

Further, when the present invention is implemented, preferably, as described in claim 6, the permanent magnet, the magnetic flux focusing element, and the magnetic detection element are coupled and fixed in a non-separable manner so that they can be handled integrally.
In this case, more preferably, as described in claim 7, a waveform shaping circuit for obtaining an output signal corresponding to a change in characteristics of the magnetic detection element is provided for the permanent magnet, the magnetic flux focusing element, and the magnetic detection element. Non-separated and fixed so that it can be handled as a unit.
If comprised in this way, handling of each structural member of the sensor becomes easy. If the waveform shaping circuit can be handled as a unit, this handling can be further facilitated.

Further, when the present invention is carried out, as described in claim 8, as the permanent magnet, at least a portion near one end surface in the magnetization direction has the smallest area on one end surface in the magnetization direction, and the magnetization direction is uniform. Instead of using a shape that is inclined in a direction in which the cross-sectional area becomes wider as the distance from the end face increases, the magnetic flux focusing element can be omitted.
Even with such a structure, even if the pitch related to the change in the magnetic characteristics of the detection surface of the tone wheel is short, the ratio of the magnetic flux flowing without passing through the magnetic detection element is kept small, and the value related to the rotation of the rotating member is set. Accurately required.

  1 to 3 show Embodiment 1 of the present invention corresponding to claims 1 to 4, 6 and 7. The feature of the present embodiment is that even when a large number of convex portions 16, 16 are formed on the outer peripheral surface in order to shorten the pitch related to the change in magnetic characteristics of the outer peripheral surface, which is the detected surface of the tone wheel 4a, It has a structure for ensuring the amount of magnetic flux that flows while passing through the magnetic detection element 17 constituting the sensor 5b. Since the structure and operation of the other parts are almost the same as the conventional structure shown in FIGS. 5 to 6 or FIGS. 7 to 8, the illustration and explanation of the equivalent parts are omitted. The description will focus on the features of the embodiment.

  As shown in FIGS. 1 and 2, the sensor 5 b incorporated in the present embodiment includes a permanent magnet 15, a magnetic flux converging element 18, and a magnetic detection element 17 in the direction of magnetic flux flow, or each of these members 15, 18, They are stacked in series in 17 axial directions (vertical direction in FIGS. 1 and 2). Of these, the permanent magnet 15 is a thick disk, square or rectangular plate and is magnetized in the axial direction. The magnetism detecting element 17 allows the magnetic flux supplied from the permanent magnet 15 to pass therethrough and changes its characteristics in accordance with the density of the passing magnetic flux. Conventionally, such as Hall IC, MR element, GMR element, etc. Various known elements can be used.

  Further, the magnetic flux concentrating element 18 is made of a magnetic material, and one end surface (the upper end surface in FIGS. 1 and 2) of both end surfaces with respect to the flow direction of the magnetic flux is set to the magnetization direction of the permanent magnet 15. It is made to contact | abut to one end surface (lower end surface of FIGS. 1-2). On the other hand, the other end surface (the lower end surface in FIGS. 1 and 2) of the magnetic flux focusing element 18 is one end surface (the upper end surface in FIGS. 1 and 2) of both end surfaces of the magnetic detection element 17 with respect to the magnetic flux passing direction. ). The magnetic flux concentrating element 18 is for concentrating the magnetic flux supplied from the permanent magnet 15 (from the N pole, which is one end surface in the magnetization direction) on the magnetic detecting element 17, and is magnetic. Made of wood.

  The magnetic flux concentrating element 18 having such a role has a large area of the base end face 19 that abuts on one end face in the magnetization direction of the permanent magnet 15 and an area of the front end face 20 that abuts on one end face of the magnetic detection element 17. Is narrow. The cross-sectional area of the magnetic flux concentrating element 18 with respect to the virtual plane in the direction orthogonal to the direction of flow of magnetic flux is from the base end surface 19 to the front end surface 20 as shown in (a) and (b) of FIG. The closer it is, the narrower it gets. More specifically, a trapezoidal shape or a substantially trapezoidal shape as shown in (a) and (b) of FIG. 3B, or as shown in (a) and (b) of FIG. , Has a shape of a truncated cone or a substantially truncated cone (Mt. Fuji). Among the magnetic flux focusing elements 18 shown in FIGS. 3B and 3C, the magnetic flux focusing element 18 of FIG. 3B is a thick rectangular plate-shaped permanent magnet 15, and the magnetic flux focusing element 18 of FIG. Each is combined with a meat disk-shaped permanent magnet 15.

  When the magnetic flux converging element 18 as shown in FIG. 3B is used, the length direction of the tip surface 20 and the length direction of the convex portion 16 formed on the detection surface of the tone wheel 4a. (The axial direction of the tone wheel 4a). This is because one specific convex portion 16 and the tip surface 20 are opposed to each other over a wide area, and the tip surface 20 and the other convex portion 16 are not opposed to each other. When the magnetic flux converging element 18 as shown in FIG. 3C is used, such a consideration is unnecessary because the area of the tip surface 20 is small. However, when the shape of the convex portion 16 formed on the detection surface of the tone wheel 4a is taken into consideration and the amount of magnetic flux flowing between the convex portion 16 and the magnetic flux focusing element 18 is considered, In some cases, it may be preferable to use the magnetic flux focusing element 18 shown in FIG. 3B and 3C, the circumferential length of the tip surface 20 of the magnetic flux focusing element 18 is the circumferential length of the convex portion 16. If the length is longer than this, the ratio of the magnetic flux flowing from the tip surface 20 to the convex portion 16 adjacent to the convex portion 16 facing the tip surface 20 increases. Therefore, from the viewpoint of suppressing such leakage magnetic flux, the circumferential width dimension of the tip surface 20 of the magnetic flux concentrating element 18 is the width dimension of the convex portion 16 in the circumferential direction (generally, the above-described covered dimension). It is preferable to make it shorter than 1/2 of the pitch of the characteristic change of the detection surface. If the width dimension of the tip surface 20 is regulated in this way, the magnetic flux can be efficiently flowed toward the convex portion 16 opposed to the tip surface 20.

  The type of the magnetic material constituting the magnetic flux concentrating element 18 is not particularly limited, but a material having a small residual magnetic flux such as pure iron flows through the magnetic detecting element 17 as the tone wheel 4a rotates. Since the magnetic flux density can be greatly changed, it can be preferably used. In the case of using pure iron, it is preferable that the surface of the magnetic flux focusing element 18 is plated or painted to prevent the magnetic flux focusing element 18 from being resistant to the flow of magnetic flux in order to prevent rust. On the other hand, if the magnetic flux focusing element 18 is made of ferrite or martensitic magnetic stainless steel, the surface of the magnetic flux focusing element 18 is prevented from being rusted without being separately plated or painted. it can. Further, the magnetic flux concentrating element 18 can be made of other magnetic materials such as ferrite.

  The magnetic detection element 17 is attached to the central portion of the front end surface 20 of the magnetic flux focusing element 18, preferably in a state where the entire front end surface 20 is covered with the magnetic detection element 17. In addition, the members 15, 18, and 17 that are overlapped in the axial direction in this manner can be arranged separately from each other, but preferably, the members 15, 18, and 17 are bonded to each other with an adhesive. They are combined together by bonding or molding in a sensor holder made of synthetic resin. In this way, if the members 15, 18, and 17 are combined together, the sensor 5b, which is a combination of the members 15, 18, and 17, can be easily handled. In this case, a waveform shaping circuit for replacing the characteristic change of the magnetic detection element 17 with the change of the electric signal and further shaping the waveform of the electric signal (to form a rectangular wave) is used for each of the members 15, 18, 17. It is also preferable to combine them with the above because it is not necessary to provide a separate waveform shaping circuit outside.

  The sensor 5b as described above has a stationary state such as the outer ring 1, 1a (see FIGS. 5, 7 and 8) in a state where the magnetic detection element 17 is opposed to the detection surface which is the outer peripheral surface of the tone wheel 4a. Support the member. In this state, when the magnetic detection element 17 faces any one of the convex portions 16 provided on the detected surface, the amount of magnetic flux passing through the magnetic detection element 17 is large as shown by a broken line in FIG. (Passing magnetic flux density is increased). On the other hand, when the magnetic detection element 17 is opposed to the concave portion 21 existing between the convex portions 16 and 16 provided on the detection surface, the amount of magnetic flux passing through the magnetic detection element 17 is reduced. (Passing magnetic flux density is lowered). As a result, the output signal of the sensor 5b changes at a frequency proportional to the rotational speed of the tone wheel 4a (with a period inversely proportional to the rotational speed).

  In particular, in the case of the rotation detection device of the present embodiment, the magnetic flux entering and exiting from one end surface of the permanent magnet 15 in the magnetization direction (in the illustrated embodiment, the magnetic flux exiting from the N pole. Conversely, the magnetic flux entering the S pole. May be guided to the magnetic flux focusing element 18 and flow to the magnetic detection element 17. Therefore, the magnetic flux entering and exiting from one end surface of the magnetization direction passes through the magnetic detection element 17 in a concentrated manner. For this reason, by increasing the amount of magnetic flux passing through the magnetic detection element 17, the degree of change in the magnetic flux passing through the magnetic detection element 17 corresponding to the change in the magnetic characteristics of the detected surface of the tone wheel 4a is set. Can be bigger. As a result, the output signal of the sensor 5b is greatly changed, and values relating to the rotation of the rotating member, such as the rotation speed and the rotation angle of the rotating member, can be obtained accurately.

  In particular, even if the number of the protrusions 16 and 16 provided on the outer peripheral surface, which is the detection surface of the tone wheel 4a, is increased and the pitch related to the change in the magnetic characteristics of the detection surface is shortened, the magnetization direction is reduced. Of the magnetic flux entering and exiting from one end face, the ratio of the magnetic flux that flows without passing through the magnetic detection element 17 is suppressed to a small value, and the value related to the rotation of the rotating member can be accurately obtained. It should be noted that the area through which the magnetic flux passes through the magnetic flux converging element 18 is the narrowest. The area of the tip surface 20 portion is such that the density of the magnetic flux passing through this portion is saturated with the magnetic material constituting the magnetic flux converging element 18. It is preferable to set the magnetic flux density to be equal to or lower. If a magnetic flux exceeding the saturation magnetic flux density is allowed to flow through the magnetic flux focusing element 18, the magnetic flux leaks out from the magnetic flux focusing element 18 and the effect of focusing the magnetic flux is reduced.

  FIG. 4 shows a second embodiment of the present invention corresponding to claims 1 to 7. In the case of the sensor 5c of the present embodiment, the other end face (the lower end face in FIG. 4) of both end faces of the magnetic detection element 17 in the magnetic flux passing direction is made of a magnetic material and comes into contact with the other end face. A second magnetic flux concentrating element 22 having a large end face area and a narrow tip end face area is provided. The tip surface of the second magnetic flux concentrating element 22 is opposed to the outer peripheral surface (convex portion 16), which is the detected surface of the tone wheel 4a. That is, the magnetic detection element 17 is sandwiched by the magnetic flux focusing element 18 and the second magnetic flux focusing element 22 from both sides in the direction of flow of magnetic flux.

  In the case of the present embodiment, by adopting the configuration as described above, the area of the tip surface of the second magnetic flux focusing element 22 is made smaller than the area of the magnetic detection element 17. Even if the number of convex portions 16 and 16 provided on the detection surface of the tone wheel 4a is further increased and the pitch relating to the change in magnetic characteristics of the detection surface is further reduced, the magnetic detection element 17 does not pass through. The ratio of the magnetic flux flowing through the And improvement of the measurement accuracy regarding the rotation of the tone wheel 4a and securing of the magnitude of the output signal change of the sensor 5c can be achieved at a higher level. It should be noted that the front end surface of the second magnetic flux focusing element 22 also has an area that does not saturate the magnetic flux.

  When the present invention is implemented, the tone wheel supported by the rotating member is not limited to the one having the gear-like irregularities on the detection surface as shown in the illustrated example, but as shown in FIG. A metal plate having a large number of through holes may be used. And the installation position of a to-be-detected surface is not restricted to a surrounding surface, An axial direction side surface may be sufficient. In this case, the detection surface and the detection unit of the sensor are opposed to each other in the axial direction.

Although not shown, as described in claim 8, as a permanent magnet, at least a portion near one end surface in the magnetization direction has the smallest area on one end surface in the magnetization direction, and from one end surface in the magnetization direction. Instead of using a shape inclined in a direction in which the cross-sectional area becomes wider as the distance increases, the magnetic flux focusing element can be omitted.
Even with such a structure, even if the pitch related to the change in the magnetic characteristics of the detection surface of the tone wheel is shortened, the ratio of the magnetic flux flowing without passing through the magnetic detection element is kept small, and the value related to the rotation of the rotating member is set. Accurately required.

1 is a schematic front view showing a first embodiment of the present invention. The A section enlarged view of FIG. 6 is a schematic diagram showing the shape of a magnetic flux focusing element. The figure similar to FIG. 2 which shows Example 2 of this invention. Sectional drawing which shows the 1st example of a conventional structure. The figure seen from the right side of FIG. Sectional drawing which shows the 2nd example of a conventional structure. The fragmentary sectional view seen from the right side of FIG. The schematic front view for demonstrating the reason that the magnetic flux which passes a magnetic detection element becomes small when the pitch which the magnetic characteristic of the to-be-detected surface of a tone wheel changes is shortened.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Outer ring 2 Hub 3 Inner ring 4, 4a Tone wheel 5, 5a, 5b, 5c Sensor 6 Outer ring raceway 7 Connection flange 8 Mounting flange 9 Inner ring raceway 10 Rolling element 11 Seal ring 12 Circular ring part 13 Cover 14 Sensor holder 15 Permanent Magnet 16 Convex part 17 Magnetic detection element 18 Magnetic flux focusing element 19 Base end face 20 Front end face 21 Concave part 22 Second magnetic flux converging element

Claims (8)

  A tone wheel having a surface to be detected in which the magnetic characteristics are alternately changed in the circumferential direction, the tone wheel being supported by the rotating member in a state where the center of the detected surface coincides with the rotation center, and adjacent to the rotating member And a sensor that is supported by a non-rotating stationary member and changes an output signal as the tone wheel rotates. The sensor passes a permanent magnet and a magnetic flux supplied from the permanent magnet. In the rotation detection device comprising a magnetic detection element that changes the characteristics in accordance with the density of the magnetic flux passing through, one end surface of the permanent magnet in the magnetization direction and the magnetic detection relating to the magnetic flux passing direction Rotation detection characterized by the installation of a magnetic flux concentrating element made of magnetic material for concentrating the magnetic flux supplied from the permanent magnet on the magnetic detection element between one end face of both end faces of the element Dress .   The magnetic flux concentrating element has a large area on one end side that abuts on one end surface of the permanent magnet in the magnetization direction, and a small area on the other end side that abuts on one end face in the magnetic flux passing direction of the magnetic detection element. The rotation detection device according to claim 1, wherein the rotation detection device has a shape in which a cross-sectional area gradually decreases toward the other end side.   The rotation detection device according to claim 2, wherein an area of the other end side of the magnetic flux focusing element is wider than an area where the magnetic flux supplied from the permanent magnet is saturated.   The width dimension of the other end side of the magnetic flux focusing element with respect to the circumferential direction of the tone wheel is smaller than 1/2 of the pitch at which the magnetic characteristics of the detected surface of the tone wheel change. The rotation detection device described in 1.   The second magnetic flux is made of a magnetic material on the other end face of the both ends of the magnetic sensing element with respect to the direction of passage of the magnetic flux, and has a large area of the base end face in contact with the other end face and a small area of the tip end face on the opposite side. The rotation detecting device according to any one of claims 1 to 4, wherein a focusing element is provided, and a tip surface of the second magnetic flux focusing element is opposed to a detection surface of the tone wheel.   The rotation detection device according to any one of claims 1 to 5, wherein the permanent magnet, the magnetic flux focusing element, and the magnetic detection element are coupled and fixed in a non-separable manner so that they can be handled together.   7. A waveform shaping circuit for obtaining an output signal corresponding to a change in characteristics of the magnetic detection element is coupled and fixed to the permanent magnet, the magnetic flux focusing element, and the magnetic detection element in a non-separable manner so as to be handled integrally. The rotation detection device described in 1.   As a permanent magnet, use at least a portion close to one end surface in the magnetization direction and having a shape in which the area of the one end surface in the magnetization direction is the smallest and the cross-sectional area becomes wider as the distance from the one end surface in the magnetization direction increases. Instead, the rotation detection device according to any one of claims 1 to 7, wherein the magnetic flux focusing element is omitted.

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