JPH06213914A - Light transmission type wheel speed sensor - Google Patents

Abstract

PURPOSE:To arrange a light source at the same side as that of an encoder plate while avoiding an optical loss of a dirt by so setting directions of light emitting and receiving to the plate having a light transmission window in parallel with an axis of an axle. CONSTITUTION:A wheel speed sensor 300 comprises a transmission type encoder plate 400, a light source for emitting a light to the plate 400, and light receiving means for receiving a light passed through a light transmission window 410 of the plate 400. A light emitting device and a photodetector are disposed on the same side as that of the plate 400 in an electric circuit of light emitting and receiving. The elements are disposed separately from a housing 70. A light from the light source is transmitted via an optical fiber 360, parallelized by a SELFOC lens 350, and then converted at 180 degrees by a rectangular prism 340. Then, it is condensed via a spherical lens, passed through the window to the photodetector via an optical fiber 320. The components of the optical system are gathered and contained in the housing 70.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel speed sensor device for detecting a wheel speed, and more particularly, it is an optical type using an optical fiber, and moreover, a light passing through a light transmitting window of an encoder plate. The present invention relates to a light transmission type in which the rotation speed of a wheel is grasped by detecting the.
The present invention can be applied to a magnetic levitation vehicle, an aircraft, etc., as well as a general vehicle such as an automobile, as a technique for detecting the wheel speed.

[0002]

2. Description of the Related Art Generally, an optical wheel speed sensor device includes an encoder plate for detecting rotation information about a wheel, a light source for projecting light on the encoder plate, and a light source for projecting the light. Light receiving means for receiving light through the encoder plate. In addition, in the case of using the optical fiber, in addition to these, each of the light source-encoder plate and the light-receiving side optical fiber for transmitting optical information between the light source-encoder plate and the light-receiving means-encoder plate is further included. Such an optical fiber type has an advantage that the light transmission function of the optical fiber allows the light source and the light receiving means to be arranged while avoiding an environment where electrical noise is likely to occur. This optical fiber type itself is disclosed in JP-A-62-17.
It is already known in Japanese Patent Publication No. 4661 or Japanese Utility Model Laid-Open No. 61-152969.

Here, it is desirable that the encoder plate and each optical fiber for optical transmission to and from the encoder plate are arranged in the inner space of the axle. Therefore, the optical path itself with respect to the encoder plate should have a space-friendly form. From that point of view, the actual development 61
Rather than performing the light projection / reception with respect to the encoder in the direction orthogonal to the axial direction of the axle as in the technique of -152969, the technique is parallel to the axial direction as in the technique of JP-A-62-174661. It is better to carry out light emission and light reception in the direction.

On the other hand, as the encoder plates, as disclosed in the above-mentioned publications, a transmissive type having a radial light transmitting window and a reflective type having a radial light reflecting metal line are known. . As described above, in consideration of the space, when the direction of the light projected onto the encoder plate and the direction of the light transmitted or reflected from the encoder plate are set to be parallel or parallel to the axis line of the axle, the reflection type is not used. While the light source and the light receiving means can be easily arranged on the same side with respect to the encoder plate, the transmission type is not easy to do so. Considering the arrangement of the electric circuits involved in the light source and the light receiving means, the light source and the light receiving means should be arranged on the same side with respect to the encoder plate.

Further, although the encoder plate is usually housed in the housing, it is located near the wheels, so that it is inevitable that the encoder plate is exposed to high temperatures when the vehicle is running, while the inside of the housing is exposed. It is very difficult to shut out completely from the external environment. for that reason,
The encoder plate and optics will become dirty over time. In particular, the surface of the light-reflecting metal line of the reflection type encoder plate becomes cloudy, and as a result, its reflectance is greatly reduced, resulting in a large light loss.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and a light source and a light receiving means are provided on the same side with respect to an encoder plate while using a transmission type encoder plate which does not cause a fog problem. An object of the present invention is to provide a light transmission type wheel speed sensor technology that can be arranged. Another object of the present invention is to provide a light transmission type wheel speed sensor technology that suppresses light loss as much as possible.

[0007]

According to the present invention, the encoder plate having the radial light transmitting window is arranged so as to be orthogonal to the axis line of the axle, and the light projected onto the encoder plate and the encoder plate pass therethrough. Set the light direction so that it is parallel to the axis of the axle. Then, a prism is arranged behind the encoder plate, and the total reflection of the prism is used to change the direction of light by 180 °. As a result, light can be transmitted through the optical fiber to the light receiving means arranged on the same side as the light source. Since the prism used for changing the direction of light is light reflection by total reflection, light is hardly attenuated even if dirt is attached to its surface. Moreover, the contamination of the one surface of the prism through which light goes in and out does not significantly reduce the transmittance, so the light loss is slight. Further, by interposing a SELFOC lens on the light-projecting side and a condensing lens on the light-receiving side in the portion facing the one surface of this prism, the light loss can be further suppressed. Especially, if the end face of the selfoc lens on the light projecting side for collimating the light is applied to one surface of the prism,
The light loss can be suppressed more effectively.

[0008]

1 is a sectional view showing a wheel portion of a magnetically levitated vehicle including a light transmission type wheel speed sensor device according to the present invention. First, the positioning of the wheel speed sensor device will be clarified with reference to FIG.

The wheels mainly consist of an annular tire (pneumatic rubber tire) 10 that contacts the road surface during traveling, and a wheel 12 that integrally supports the tire 10 on the outer periphery thereof. The wheel 12 is rotatably supported around a hollow axle 14 via a bearing 16. Therefore, the tire 10
The wheel 12 belongs to the rotating side, and the axle 14 belongs to the non-rotating side. In the wheel 12 that opens in one direction,
A brake device for wheels is arranged on the outer periphery of the axle 14 close to the opening. The piston housing 20 is located in a portion facing the opening of the wheel 12. The piston housing 20 is a member that accommodates a brake piston 21 that can move in parallel with the axis of the axle 14, and is itself supported by the axle 14 and does not rotate like the axle 14.
A plurality of rotors 22R and stators 22S are alternately arranged in the internal space of the wheel 12 facing the brake piston 21. The disk-shaped rotor 22R is supported by a key 23 attached to the wheel 12, and
And rotates in accordance with the rotation of the wheel 12. On the other hand, the stator 22S adjacent to the rotor 22R is supported by the spline portion 25a of the torque tube 25 attached to the axle 14 via the piston housing 20, and holds its position without rotating. During braking, when hydraulic pressure is supplied to the brake piston 21, the brake piston 21 pushes the rotor 22R via the stator 22S, and friction between the stator 22S and the rotor 22R generates a braking force. At this time, since a large amount of heat is generated, between the key 23 and the wheel 12, so as to surround the heat generating portion,
Further, heat shield plates 26a and 26b are provided between the torque tube 25 and the wheel 12, respectively. Also,
A thermal fuse 27 is provided at the portion of the wheel 12 facing the inside of the tire 10. This thermal fuse 2
Reference numeral 7 is for exhausting the air pressure of the tire 10 in order to prevent an abnormal situation from occurring in the tire 10 when the wheel 12 is overheated due to running and braking.

In the embodiment shown in the drawings, in addition to the wheel speed sensor device 300 for detecting the wheel rotation speed, a tire pressure detecting device 50 for detecting the air pressure inside the tire 10 is also provided.
It also has The tire pressure detecting device 50 is for knowing an abnormality such as a flat tire, and is a portion P for detecting a pressure that converts a change in the air pressure of the tire 10 into a change in the amount of light.
And a means L for transmitting optical information to the portion P, and a light source and a sensor for handling as optical information. An optical fiber that is elastically deformed by receiving the pressure inside the tire is used for the portion P for pressure detection, and as the transmission means L, another optical fiber that can be optically coupled by being bonded to the optical fiber of the portion P is used. An optical fiber is used. As the elastically deformable optical fiber, a rubber optical fiber whose core and clad are made of a rubber material such as silicone can be used.
When the rubber optical fiber is deformed by receiving the air pressure of the tire 10, the total reflection condition changes, so that the amount of transmitted light is reduced, that is, it functions as a pressure-light conversion element. The latter optical fiber that optically transmits to the rubber optical fiber has its end rotatably supported for signal transmission between the rotating side and the non-rotating side. On the other hand, in the tire pressure detection device 50, the end of the optical fiber to be rotatably supported is arranged concentrically with the axis of the axle 14, and is supported by the bearing inside the housing 70 inside the hollow axle 14.

A short inward flange 141 is provided on the inner periphery of the cylindrical axle 14 near the opening end, and a screw 142 is cut on the inner periphery of the axle 14 extending from the flange 141 to the opening. ing. The screw ring 60, the cap member 61, and the support member 62 are sequentially screwed to the screw portion 142. The screw ring 60 sandwiches the flange portion 71 of the housing 70 between the screw ring 60 and the inward flange 141 to fix the housing 70 to the inside of the axle 14.
At this time, the cap member 61 functions as a locking stopper for the screw ring 60. Further, the support member 62, a part of which is exposed to the outside of the axle 14, functions to support the hub cap 63 from the inside and position it. Hub cap 63
Is located at the center of the wheel 12 and is fixed to the wheel 12 by a stop member 64 so as to cover the opening of the axle 14.

2-4 illustrate the structure of the housing 70 inside the axle 14. Housing 70
Is a three-part structure, a plate-shaped first member 701 on the side of the cap member 61, and a second member 70 having a flange 71.
2, including a third member 703 that is most distant from the opening side.
The first member 701 and the second member 702 are the packing 7
04 and the second member 702 and the third member 703 are integrated with each other by a stopper member 706 while being fitted and coupled with each other by a stopper member 705. In such a housing 70, a central hole 73, which has a different diameter but extends from one end to the other end, is formed in a central portion along the axis of the axle 14. This center hole 73
Inside, a rotating portion 110 of the first optical fiber 100 for detecting tire pressure is rotatably supported by bearings 74a and 74b. These bearings 74a and 74b themselves are arranged at predetermined positions in the housing 70 by the C-shaped retaining ring 75a and the stepped portion of the second member 702, and the spacer 76 and another C-shaped retaining ring 75b. Further, in the center hole 73 of the housing 70, seal rings 77a, 77b are arranged on the axial center of the axle 14 so as to sandwich the bearings 74a, 74b. These seal rings 77a and 77b are used for the bearing 7
4a, 74b for dust protection.

First optical fiber 10 for detecting tire pressure
The rotating portion 110 of 0 has a center-optical fiber 101 along the axial center of the axle 14 as shown in the sectional structure of FIG.
An eccentricity-optical fiber 102 deviated from the axis of the axle 14 is integrated in the cable covering member 103. Each of the optical fibers 101 and 102 is a clad type having a high refractive index core inside and a low refractive index clad on the outer circumference. The rotating portion 11 of the first optical fiber 100
The one end 110 a of 0 is the third member 70 of the housing 70.
3 is located inside the optical fiber 3 and faces the end surface of the second optical fiber 200 for transmission for tire pressure detection with a gap of, for example, about 1 to 2 mm. Second optical fiber 200
Is arranged at the center of the third member 703 of the housing 70 by an optical connector 210 having a built-in condenser lens and a screw ring 220 holding the optical connector 210. Here, the second optical fiber 200 has a structure in which a large number of pixel fibers 201 are melted and integrated with each other and are protected by a cable coating 202, as shown in the sectional structure of FIG. 6. The second optical fiber 200 has a first
Since it belongs to the non-rotating side unlike the optical fiber 100 of
It is possible to pull out the inside of the axle 14 to a place where there is no influence of a strong magnetic field. Then, a light emitting element as a light source and a light receiving element (photo-electric conversion element) as a sensor means can be arranged at the drawn end.

On the other hand, the other end 110b of the rotating portion 110 of the first optical fiber 100 for detecting tire pressure is
It is located inside the cylindrical holder 65 at the center of the hub cap 63, and is butt-connected to the end face of another optical connector 120 supported by the holder 65 concentrically with the axis of the axle 14 (FIG. 1). And FIG. 4). Optical connector 1
20 is a center of the rotating portion 110-an optical fiber 131 for transmission or lead extending from the hub cap 63, and an eccentric portion of the rotating portion 110-an optical fiber 102 for transmitting or lead extending from the hub cap 63. The optical fibers 132 are connected to each other. These two optical fibers 131 and 132 as the transmission means L have one fiber inside, and one of them sends the light from the light emitting element to the portion P for pressure detection. The other sends back the light detected in the portion P to the light receiving element side. These two optical fibers 131, 1
32 extends to the portion P while being supported on the wheel 12 surface by the clamp member 140 in the middle thereof.

In the wheel speed sensor device 300 of the embodiment,
Rotating part 110 of optical fiber 100 for tire pressure detection
Are used to support the encoder plate 400. Moreover,
The housing 70 itself that supports the rotating portion 110 of the optical fiber 100 is also used as the housing of the wheel speed sensor device 300. Therefore, the second of the housing 70
A gap 301 for accommodating the encoder plate 400 is provided in the connecting portion between the member 702 and the third member 703. A transmissive encoder plate 400 having a large number of light transmissive windows 410
Is integrally supported by the support mechanism 310 around the rotating portion 110 of the optical fiber 100, while the rotating portion 110
It is possible to rotate in the gap 301 with the rotation of. Of course, the wheel speed sensor device 300 and the tire pressure detection device 5
It is also possible to provide 0 separately from the inside of the axle 14.

FIG. 7 shows a support mechanism 3 for the encoder plate 400.
Reveals ten. The support mechanism 310 mainly includes a hub 312 that fits in the rotating portion 110 and a screw ring 314 that is screwed to the hub 312.
The encoder plate 400 is sandwiched between the screw 12 and the screw ring 314 to support the encoder plate 400. In addition, the hub 312 has a screw portion 312 to which the screw ring 314 is coupled.
In addition to a, a large diameter portion 312b having a diameter similar to that of the screw ring 314, and a small diameter portion 312 adjacent to the large diameter portion 312b.
with c. The large diameter portion 312b of such a hub 312 has two positioning pins 316, whereby
The slit of the encoder plate 400 is positioned.
Further, the small diameter portion 312c of the hub 312 has a set screw 3
18 is threaded to secure hub 312 to rotating portion 110 of optical fiber 100. According to the support mechanism 310,
The encoder plate 400 can be accurately set on the rotating portion 110 and can be securely fixed.

The wheel speed sensor device 300 includes a transmissive encoder plate 400, a light source for projecting light on the encoder plate 400, and a light transmitting window 4 of the encoder plate 400.
An optical system including a light receiving unit for receiving the light passing through 10 is provided. The light emitting element as a light source and the light receiving element for photoelectrically converting (neither is shown) have an encoder plate 400 because of the arrangement of electric circuits involved in light emission and light reception.
Placed on the same side with respect to. Moreover, in order to avoid the generation of electrical noise, the light emitting and light receiving elements and the electric circuits related thereto are located away from the housing 70. The light from the light source (light emitting element) is transmitted by the optical fiber 360 on the light projecting side, is collimated by the SELFOC lens 350, and is then 180 ° by the right-angle prism 340 that is in close contact with the SELFOC lens 350.
° The direction is changed. The light whose direction has been changed is collected by the spherical lens 330 behind the encoder plate 400, passes through the light transmission window 410 of the encoder plate 400, and then reaches the light receiving element through the light receiving side optical fiber 320.

The respective components of such an optical system are collectively housed in a housing 70. The ends of the optical fibers 360 and 320 for projecting light and receiving light are connected to the third member 7 respectively.
03, the spherical lens 330, the right-angle prism 340, and the SELFOC lens 350 are installed in the holes provided in the second member 702 so that they can be taken in and out. Optical fiber for tire pressure detection 1
Since the encoder plate 400 is supported with respect to the rotating portion 110 of No. 00, the housing 70 for supporting the rotating portion 110 can be used as a housing of an optical component for projecting and receiving light with respect to the encoder plate 400. The end 320e of the optical fiber 320 on the light receiving side is set at a position close to the encoder plate 400, and the SELFOC lens 3 at the end of the optical fiber 360 on the light projecting side is set.
In order to set the position of 50, each optical fiber 320, 36
0 is fixed to the housing 70 by a stopper member such as a hexagon bolt.

Here, the suppression of light loss will be briefly described. The light loss is not only attenuated by the light transmission in each of the optical fibers 360 and 320 on the light projecting side and the light receiving side, but is also diffused after passing through the light transmitting window 410 of the encoder plate 400, and the prism 340. It is considered that the main cause is the diffusion of the light during the change of the direction of the light. The diffusion of the latter two lights is greater than the attenuation of the former. Therefore, in order to reduce such light loss, the light transmission window 410 of the encoder plate 400 is set on the focal plane of the spherical lens 330, and the SELFOC lens 35 is used.
0 and the end of the light-transmitting optical fiber 360 adjacent to it are put in a cylindrical case cover 370, and further, the end surface of the SELFOC lens 350 is brought into close contact with the surface of the rectangular prism 340. SELFOC lens 35
The end surface of 0 is, for example, 1 to 10 m from the surface of the prism 340.
Although they can be separated by about m, the light loss will inevitably increase as compared with the case where they are in close contact. The jig 343 for alignment is in contact with the totally reflecting surface of the prism 340 (see FIG. 4), so that the amount of dirt attached to the jig is small,
Further, even if dirt is attached, it is unlikely that the total reflection is adversely affected.

In the embodiment, one right-angle prism 340 is used to change the direction of light, but two prisms 341 and 342 can also be used as shown by a chain line in FIG. Needless to say, these prisms 341 and 342 can be provided separately from each other. Further, by interposing a SELFOC lens between the encoder plate 400 and the optical fiber 320 on the light receiving side,
It is possible to more efficiently send the light that has passed through the light transmission window 410 of the encoder plate 400 to the optical fiber 320 side.

Further, in the embodiment, after the direction is changed by the right-angle prism 340, the light is projected onto the encoder plate 400. However, the light projection and the light reception are reversed, and the light is first projected onto the encoder plate 400, and the light transmission window 410. It is also possible to change the direction of light that has passed through the rectangular prism 340. In that case, a SELFOC lens may be provided between the encoder plate 400 and the optical fiber, and a convex lens may be provided between the encoder plate 400 and the rectangular prism 340.

[0022]

According to the present invention, since the transmissive encoder plate 400 having the light transmissive window 410 is used and the directions of the light projected and the light received therefrom are set to be parallel to the axis line of the axle. An optical path that is advantageous for being housed in the axle 14 can be formed, and since the light is converted by 180 ° by total reflection by the prism 340, light loss due to dirt can be avoided, The light source and the light receiving means can be arranged on the same side with respect to the encoder plate 400. Further, in particular, the end face of the SELFOC lens 350 is brought into close contact with one surface of the prism 340, and the SELFOC lens 350 is interposed to interpose the optical fiber 3 on the light projecting side.
If the light is sent from 60 to the prism 340 side, the light loss can be effectively suppressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a wheel portion to which a wheel speed sensor device of the present invention is applied.

FIG. 2 is a side view showing a housing portion in an axle.

3 is a cross-sectional view taken along line 3-3 'of FIG.

4 is a cross-sectional view taken along line 4-4 'of FIG.

5 is a cross-sectional view taken along line 5-5 'of FIG.

6 is a cross-sectional view taken along the line 6-6 'of FIG.

FIG. 7 is a sectional structural view showing a support mechanism of an encoder plate.

[Explanation of symbols]

 Reference Signs List 10 tire 12 wheel 14 axle 50 tire pressure detection device 70 housing 300 wheel speed sensor device 310 encoder plate support mechanism 320 light receiving side optical fiber 330 spherical lens (condensing lens) 340 prism 350 selfoc lens 360 light emitting side light Fiber 400 Encoder plate 410 Light transmission window

Claims (3)

[Claims] 1. An encoder plate which has a large number of radial light transmission windows, is arranged in an axle located at the center of a wheel so as to be orthogonal to the axis of the axle, and rotates with the wheel. Is a light transmission type wheel speed sensor device in which the directions of the light projected and the light passing through the encoder plate are set to be parallel to the axis of the axle, and the wheel speed sensor device is arranged on one side of the encoder plate. A light source, an optical fiber on the light projecting side that optically transmits light from this light source to the vicinity of the encoder plate, and is arranged on the other side of the encoder plate,
A prism for converting the direction of the light transmitted by the optical fiber on the light projecting side by 180 ° by total reflection, and a prism that faces one surface of this prism and transmits the direction of the light converted by the prism to one side of the light source. It is composed of an optical fiber on the light receiving side and a light receiving means for receiving the light transmitted by the optical fiber on the light receiving side and converting the light into electricity, and the light is the light of the encoder plate either before or after the direction change by the prism. A light transmission type wheel speed sensor device which is set so as to pass through a transmission window. 2. The light transmission type wheel speed sensor device according to claim 1, wherein a selfoc lens is provided at one end of the optical fiber on the light projecting side, and an end surface of the selfoc lens is in contact with one surface of the prism. 3. The light transmission type of claim 1, wherein a condenser lens is provided between the light transmission window of the encoder plate and the prism, and the light transmission window is located on a focal plane of the condenser lens. Wheel speed sensor device.