JPH0829441A - Rotating speed detecting device - Google Patents

Abstract

PURPOSE:To prevent the change of the distance between a sensor and a tone wheel or the breakage of a constituting component due to the freeze of water that has intruded into the inside. CONSTITUTION:In a synthetic resin case 22a in which a sensor 19 has been enclosedly embedded, a heating element 22 other than the sensor 19 is provided. When the freezing of water is possible, the heating element 23 is electrically energized. Water intruded inside a cover 18a is discharged through a draining hole 24 formed in the lowest position of the cover 18a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION A rotation speed detecting device according to the present invention is incorporated in a hub unit for supporting wheels of an automobile, for example, and is used for detecting the rotation speed of the wheels.

[0002]

2. Description of the Related Art In order to control an antilock brake system (ABS) or a traction control system (TCS) of an automobile, it is necessary to detect the rotational speed of wheels. A rolling bearing unit incorporating a rotation speed detecting device for this purpose is disclosed in, for example, Japanese Utility Model Laid-Open No. 3-128856.
No. 5-4021, or US Pat. No. 506.
It has been conventionally proposed as described in the specification of 3345 and the like. 5 to 7 show an example of the structure of the rolling bearing unit with such a rotation speed detecting device.

Double-row outer ring raceways 2, 2 are formed on the inner peripheral surface of the fixed ring 1 that does not rotate during use. This fixed wheel 1
Is supported by the suspension device by a flange 3 formed on its outer peripheral surface. Inside the fixed wheel 1, a rotating wheel 4 that rotates together with the wheel when used is arranged. This rotating wheel 4
Inner ring raceways 5, 5 are provided on the outer peripheral surface of the inner ring raceways 5, 5, and the inner ring raceways 5, 5 are opposed to the outer ring raceways 2, 2. And, between these outer ring raceways 2 and 2 and inner ring raceways 5 and 5,
A plurality of rolling elements 7, 7 held by cages 6, 6 are provided. Therefore, the rotating wheel 4 is the fixed wheel 1
It is rotatable inside.

An outer peripheral surface of the inner end portion of the rotating wheel 4 (referred to as an end portion that is closer to the center in the vehicle width direction when assembled to the vehicle, which is the right end portion in FIG. 5) and an inner peripheral surface of the inner end portion of the fixed wheel 1. In between
The seal assembly 8 is attached to close the inner end (right end in FIG. 5) opening of the space 9 in which the rolling elements 7, 7 are installed.
The seal assembly 8 includes an inner ring 36 that constitutes the rotary wheel 4.
An inner seal ring 10 externally fitted and fixed to the shoulder portion of the above, and an outer seal ring 11 internally fitted and fixed to the inner end portion of the fixed wheel 1. The outer end of the space 9 (the end that is the outer side in the width direction of the vehicle when assembled to the vehicle, the left end in FIG. 5) is closed by another seal ring 12.

The inner seal ring 10 comprises a core metal 13 and a seal material 14. Then, the inner surface of the cored bar 13 (see FIGS.
The tone wheel 15 is additionally provided on the right side surface of 6.
The tone wheel 15 made by punching a magnetic plate has a gear shape as shown in FIG.
That is, the tongue pieces 16 and 16 and the notches 17 and 17 are alternately and repeatedly formed in the circumferential direction of the tone wheel 15 at equal pitches in the circumferential direction. The tone wheel 15 has a ferromagnetic portion and a non-magnetic or weak magnetic portion alternately and repeatedly arranged at equal pitches in the circumferential direction by such a shape.

A cover 18, which has an L-shaped cross section and is formed in an annular shape as a whole, is externally fitted and fixed to the inner end opening (the right end opening in FIG. 5) of the fixed wheel 1. The sensor 19 is supported and fixed inside. This sensor 19 is configured by arranging a permanent magnet 20 magnetized inward and outward (left and right in FIGS. 5 and 6) and a magnetic detection element 21 such as a Hall element in series. Such a sensor 19 is
For example, the magnetic detection element 21 may be replaced by the tone wheel 15
The rotational speed detection device is configured by facing the outer surface of the device with a minute gap therebetween.

With the tone wheel 15 and the sensor 19 installed as described above, a magnetic field reaching from the one end surface to the other end surface of the permanent magnet 20 is formed in the portion including the magnetic detection element 21. The density of the magnetic flux forming this magnetic field becomes high when the end face of the magnetic detection element 21 and the tongues 16, 16 of the tone wheel 15 face each other, and the end face cuts the tone wheel 15. Lack 1
It becomes low when facing 7 and 17. Such a change in magnetic flux density is extracted as a voltage change by a bridge circuit or the like including the magnetic detection element 21. The frequency at which the voltage changes in this way is proportional to the rotational speed of the wheel. Therefore, if the above voltage is input to the ABS or TCS controller, these ABS and TCS can be controlled appropriately.

[0008]

In order to accurately detect the rotation speed of a rotating portion such as a wheel by the rotation speed detecting device configured and operating as described above, the end surface of the sensor 19 and the side surface of the tone wheel 15 are detected. It is necessary to regulate the distance between and exactly as designed. When this distance becomes larger than the design value, even if the tone wheel 15 rotates, the rate of change of the magnetic flux density passing through the magnetic detection element 21 becomes small and the detection of the rotational speed becomes inaccurate. . On the other hand, since the appropriate value of the distance is a small value of about 0.5 mm, the tone wheel 15 and the sensor 19 interfere with each other while allowing the rotation speed to be accurately detected (rubbing as the wheel rotates). To prevent this, it is necessary to accurately regulate the mounting position of the sensor 19.

On the other hand, since the tone wheel 15 and the sensor 19 for controlling the ABS and TCS are attached to the wheels, it is difficult to completely prevent the ingress of water.
There is a possibility that a small amount of water may enter due to running in the rain or car washing. When the water that has entered the rotation speed detection device in this way expands in volume due to freezing, it is possible to shift the mounting position of the sensor 19. For example, the cover 18, the permanent magnet 20, and the magnetic detection element 21.
When the water that has entered between the housing and the synthetic resin case 22 is frozen, the position of the sensor 19 is in the axial direction (see FIGS.
The horizontal direction) or the diametrical direction (vertical direction in FIGS. 5 and 6), the distance deviates from an appropriate value, the rotational speed detection becomes inaccurate, or the tone wheel 15 and the sensor 1 are detected.
9 may interfere with each other.

Further, for example, between the side surface of the tone wheel 15 and the end surface of the sensor 19, the water that has entered between the portion that is fixed during use and the portion that rotates during use is rotated while being frozen. When the wheel 4 is activated, the rotation speed detection device itself may be damaged. The rotation speed detection device of the present invention was invented in view of the above-mentioned circumstances.

[0011]

The rotation speed detecting device of the present invention is, like the conventionally known rotation speed detecting device, a sensor supported by a fixed ring that does not rotate during use, and is concentric with the fixed ring. It is provided with a tone wheel that is provided and rotates when used.

In particular, the rotation speed detecting device of the present invention is characterized in that a heating element is installed inside or in the vicinity of the sensor or tone wheel.

[0013]

The operational situation when the rotational speed of the rotary wheel is detected by the rotational speed detecting apparatus of the present invention configured as described above is the same as that of the conventionally known rotational speed detecting apparatus.
Particularly, in the case of the rotation speed detecting device of the present invention, it is possible to prevent the water that has entered the inside from being frozen by energizing the heating element. As a result, it is possible to reliably prevent the functional deterioration of the rotation speed detection device and the damage of each part due to the freezing of water.

[0014]

FIG. 1 shows a first embodiment of the present invention.
In this embodiment, the present invention is applied to the prior art described with reference to FIGS. 5 to 6, and the structure of the portion supporting the rotating wheel 4, the tone wheel 15 constituting the rotation speed detecting device, and the permanent magnet. The arrangement and the like of the magnetic detection element 21 and the magnetic detection element 21 are the same as those of the above-described conventional technique. Therefore, the same parts as those of the prior art are designated by the same reference numerals to omit or simplify the overlapping description, and the characteristic part of the present invention will be mainly described below.

A cover 18a, which has an L-shaped cross section and is formed in an annular shape as a whole, is externally fitted and fixed to the inner end opening of the fixed wheel 1, and a synthetic resin case 22a containing a sensor 19 is provided inside the cover 18a. Supported and fixed. Unlike the conventional structure described above, the synthetic resin case 22a is formed in an annular shape as a whole, and the permanent magnet 20 and the magnetic detection element 21 are embedded in a part of the circumferential direction thereof.

In particular, in the case of the rotational speed detecting device of the present invention, the synthetic resin case 22 is provided with a heating element 23 formed in a ring shape, for example, inside the synthetic resin case 22a.
It is embedded almost all around a. As the heating element 23, various conventionally known heating elements such as a semiconductor heater, a nichrome wire, a carbon film resistance, and a metal film resistance can be adopted. The heating element 23 does not have to be integrated, and may be divided into a plurality of pieces in the circumferential direction. Further, in the illustrated embodiment, the cover 18a is
A drainage hole 24 is formed in a portion of the lowermost portion of the above, which is present at the lowest position when it is mounted on the fixed wheel 1.

In the case of the rotation speed detecting device of the present invention configured as described above, the inside of the cover 18a is heated by energizing the heating element 23, and the synthetic resin case is placed inside the cover 18a. It is possible to prevent freezing of water that has entered between the cover 22a and the cover 18a, or between the synthetic resin case 22a and the tone wheel 15, and the seal assembly 8. As a result, the installation position of the synthetic resin case 22a does not shift due to the freezing of water, and the parts that rotate relative to each other do not stick to each other. You can surely prevent damage.

As shown in FIG. 2, the energization of the heating element 23 is frozen based on a signal from a temperature sensor 29 attached to the rotational speed detecting device portion by being embedded in the synthetic resin case 22a or the like. It is also possible to suppress the battery consumption by performing it for a predetermined time only when there is a risk of.
In the case of the structure of FIG. 2, instead of providing the temperature sensor 29 near the rear surface of the sensor 19 (right surface of FIG. 2), the heating element 23 is formed into a cylindrical shape to prevent interference between the temperature sensor 29 and the heating element 23. ing.

Further, as an example of the time zone in which the heating element 23 is energized, it is started at the time when the operation of the automobile is finished, and after the elapse of a sufficient time to drain the water in the cover 18a from the drain hole 24. It is possible that it will end. Also, especially when used in cold regions, while the car is running,
The heating element 23 can also be energized. Such energization control of the heating element 23 is performed by a controller (not shown) based on a detection signal from the temperature sensor 29, a signal indicating ON / OFF of the ignition switch, and the like.

Next, FIG. 3 shows a second embodiment of the present invention. In the first embodiment described above, the drive wheels (the rear wheels of the FR vehicle, F
While the rotation speed detecting device of the present invention was assembled to the hub unit for supporting the front wheel of the F car, in the case of this embodiment, the non-driving wheels (the front wheels of the FR car, the rear wheels of the FF car). ring)
The rotation speed detector is installed in the. Further, in the above-described first embodiment, the sensor 19 is composed of the permanent magnet 20 and the magnetic detection element 21 such as a Hall element, whereas in the case of the present embodiment, the permanent magnet 20 and the pole piece. The sensor 19a is composed of the coil 25 and the coil 26. Further, the tone wheel 15a is formed of a magnetic material in a circular ring shape, and is externally fitted and fixed to the inner end portion of the hub 27, which is a rotating wheel. On the inner surface of the tone wheel 15a facing the sensor 19a, a plurality of recessed grooves 28, 28 extending in the radial direction are formed at equal intervals in the circumferential direction. Therefore, the shape of the inner surface in the circumferential direction is
The concave and convex portions are arranged at equal intervals, and a ferromagnetic portion and a weak magnetic portion (grooves 28, 28 portions) are alternately and repeatedly provided on the inner side surface.

The coil 26 includes the pole piece 2
An electromotive force corresponding to a change in the density of the magnetic flux flowing in the magnetic field 5 is induced. The density of the magnetic flux flowing in the pole piece 25 is such that the end surface of the pole piece 25 has the concave grooves 28, 2
8 is low at the moment of facing the groove 8 and is high at the moment of facing the portion between the concave grooves 28, 28. Therefore, the electromotive force generated in the coil 26 changes at a frequency proportional to the rotation speed of the hub 27.

In order to apply the present invention to the rotation speed detecting device having such a structure, in this embodiment, a constant DC bias current which does not change itself is applied to the coil 26 constituting the sensor 19a. The coil 26 generates heat on the basis of this bias current, and the moisture that has entered the cover 18b is prevented from freezing and is discharged from the drain hole 24.
When the density of the magnetic flux flowing through the pole piece 25 changes due to the rotation of the hub 27, the output of the coil 26 can be taken out as a direct current that changes around the bias current voltage. The rotation speed is detected by the coil 26 in this way.
When the bias current does not flow by comparing the direct current extracted from above with the reference voltage corresponding to (equal to) the bias current voltage and determining the frequency (or cycle) at which the direct current exceeds (or falls below) the reference voltage. You can do the same as.

Next, FIG. 4 shows a third embodiment of the present invention. In this embodiment, the present invention is applied to a rotation speed detecting device incorporated in a bearing device for supporting a rigid axle type axle such as a rear wheel of a truck. The tone wheel 15b is externally fitted and fixed to the outer peripheral surface of one inner ring 30 of the pair of inner rings 30 and 30 which is externally fitted and fixed to the end portion of the axle. Gear-shaped irregularities are formed on the outer peripheral surface of the tone wheel 15b, and ferromagnetic portions (convex portions) and weak magnetic portions (concave portions) are alternately and repeatedly provided on the outer peripheral surface.

A through hole 32 is formed in the intermediate portion of the outer ring 31 supported by the suspension device and aligned with the outer peripheral surface of the tone wheel 15b. Inside the through hole 32, the permanent magnet 2 is formed.
A sensor 19 including 0 and a magnetic detection element 21 is installed. The sensor 19 is embedded in a synthetic resin case 22c, and the synthetic resin case 22c is covered with a cover 18c made of a magnetic metal plate.

In order to apply the present invention to the rotation speed detecting device having such a structure, in this embodiment, the concave portion 33 is formed in the portion of the inner peripheral surface of the intermediate portion of the outer ring 31 facing the outer peripheral surface of the tone wheel 15b. The heating element 23 is formed in the recess 33. Then, the heating wire 23 can be energized by a conductor 35 inserted through a through hole 34 formed in the lower portion of the outer ring 31. The heating element 23 is preferably provided over substantially the entire circumference of the inner peripheral surface of the outer ring 31 except for the portion where the sensor 19 is installed. However, even if only a part thereof is provided, it is made of metal. Since the temperature of the entire outer ring 31 rises, the antifreezing effect can be obtained.

[0026]

Since the rotation speed detecting device of the present invention is constructed and operates as described above, the function of the rotation speed detecting device is deteriorated by the water entering the rotation speed detecting device or the function thereof is reduced. It is possible to reliably prevent damage to parts.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a modification of the first embodiment.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing the third embodiment.

FIG. 5 is a sectional view showing an example of a conventional structure.

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

FIG. 7 is a view of the tone wheel as viewed from the side of FIG.

[Explanation of symbols]

 1 Fixed Ring 2 Outer Ring Raceway 3 Flange 4 Rotating Ring 5 Inner Ring Raceway 6 Cage 7 Rolling Element 8 Seal Assembly 9 Space 10 Inner Seal Ring 11 Outer Seal Ring 12 Seal Ring 13 Core Bar 14 Sealing Material 15, 15a, 15b Tone Wheel 16 Tongue piece 17 Notch 18, 18a, 18b, 18c Cover 19, 19a Sensor 20 Permanent magnet 21 Magnetic detection element 22, 22a, 22b, 22c Synthetic resin case 23 Heating element 24 Drain hole 25 Pole piece 26 Coil 27 Hub 28 Recessed groove 29 Temperature Sensor 30 Inner Ring 31 Outer Ring 32 Through Hole 33 Recess 34 Through Hole 35 Conductor Wire 36 Inner Ring

Claims (1)

[Claims] 1. A rotation speed detection device comprising a sensor supported by a fixed wheel that does not rotate during use, and a tone wheel that is concentric with the fixed ring and that rotates during use. A rotation speed detecting device characterized in that a heating element is installed inside or in the vicinity thereof.