Patent Application
20070216505
The present invention relates to a magnetic encoder which has strong magnetic characteristic, superior rigidity and advantage in productivity and cost. More specifically, the present invention relates to a magnetic encoder which is easily attached to a reinforcing ring, and has no fear of generating gap, distortion and deformation resulted from the difference of thermal expansion coefficient between the magnetic ring and the reinforcing ring, and has no fear of damage caused by contamination of foreign material.
A magnetic encoder made of highly elastic rubber material with magnetism has been conventionally used considering damage and deformation caused by contamination of foreign material. The magnetic encoder has been constructed such that a magnetic powder is mixed with the rubber material and the mixture is fed in a mold together with a reinforcing ring and is heated and compressed to be vulcanized and glued.
A magnetic powder of ferrite is generally used for the magnetic powder. Whereas, for example, a magnetic material comprised of rare earth is inferior in kneading working property and moldability and requires high cost, so that it is not suitable to be mixed with a rubber material and it is not generally used.
The magnetic encoder formed by being mixed with the ferrite and vulcanized and glued is superior in moldability, but has small magnetic force and is not uniform in magnetic state density because of orientation of magnetic powder.
The orientation of magnetic powder has to be arranged in advance in the form of dough or to be arranged in process of molding to be vulcanized and molded in order to make the magnetic-flux density uniform (for example, refer to JP-A-2002-333033).
The magnetic encoder made of ferrite bond magnet formed by mixing the magnetic powder of ferrite, as mentioned above, is required to be highly filled with ferrite in order to have practical magnetic characteristic. Therefore, there arise problems such that the rubber property is remarkably deteriorated and its production takes a lots of labor because the above mentioned magnetic encoder is vulcanized and glued in a mold.
Further, complicated site methods are required such that many kinds of ferrite are blended or some extra process of molding are added in order to alleviate the drawback of non-uniform magnetic-flux density of the circumference of the magnetic encoder.
The inventors of the present invention have carefully examined and carried out many magnetic characteristic tests. The object of the present invention is to provide a magnetic encoder which has a strong magnetic characteristic, superior handling ability, and possibility in the price.
Still further object of the present invention is to provide a magnetic encoder which is easily fitted to a reinforcing ring even when a magnetic ring is not a unitary magnetic body but is molded by mixing a binder in a magnetic powder and which has no fear of causing gap, distortion, and deformation even when there is the difference of the coefficient of thermal expansion between the magnetic ring and the reinforcing ring and has no fear of damage resulted by contamination of foreign material.
According to one aspect of the present invention, the magnetic encoder, adapted to use for a vehicle axle or the like, for generating pulse code by magnetic force and a magnetic ring is fitted to a reinforcing ring fixed on the vehicle axle with an adhesive and thereafter S and N poles are alternately and circularly magnetized thereon.
Silicone sealant with elasticity may be preferably used as the adhesive for fixing the magnetic ring into the reinforcing ring. Such an adhesive has a cushion ability and absorbs the difference of the coefficient of thermal expansion when the difference between the magnetic ring and the reinforcing ring is large, thereby preventing generation of gap, distortion and deformation.
According to other aspect of the present invention, a magnetic encoder is used for a vehicle axle or the like for generating pulse code by magnetic force and a magnetic ring is fitted to a reinforcing ring fixed on the vehicle axle with an adhesive, then S and N poles are alternately and circularly magnetized thereon, and thereafter the edge of the reinforcing ring is crimped so as to join to the magnetic ring by bending the edge of the reinforcing ring by force.
According to the above-mentioned magnetic encoder, the magnetic ring is fitted to the reinforcing ring by a crimp in place of using the above-mentioned adhesive. Therefore, its production is facilitated while obtaining the same effect of the above-mentioned one aspect of the present invention without using the adhesive.
In both above-mentioned aspects of the present invention, the magnetic ring may be a single magnetic body or a plastic magnet which is formed of a composite substance in which a binder such as rubber or resin is mixed with a magnetic powder such as ferrite. The magnetic ring made of a single magnetic body is easily produced, has high magnetic force, easily produces a magnetic field, has enough strength, and is highly superior in its handling. Therefore, a magnetic encoder with large pulse generation ability can be provided at a low price and its strong magnetic force makes the gap between the magnetic encoder and a sensor larger, so that its assembly tolerance is roughly determined. As a result, the magnetic encoder will be made smaller and more compact and its high productivity and low cost can be achieved.
The thickness and shape of the magnetic ring formed with a magnetic powder such as ferrite are optionally determined, thereby obtaining a lightweight magnetic encoder.
According to other aspect of the present invention, a magnetic ring is covered with a protective cover made of a nonmagnetic material and the protective cover is fitted to the reinforcing ring by crimping or is fixedly engaged so as to join each other. Therefore, without using an adhesive and without giving the magnetic affect on the magnetic sensor, the magnetic ring is protected from being contact with external factor or colliding.
According to other aspect of the present invention, a cushion material is contained between the magnetic ring and the protective cover. Even when improvident pressure is applied or foreign material is bit in case of assembling, the cushion material also functions as a buffer for absorbing shock or impact.
According to the present invention, a magnetic ring is comprised of a single magnetic body or is molded by mixing a binder such as rubber or resin into a magnetic powder such as ferrite. The former one can provide a magnetic encoder with large pulse generation ability and with enough strength at a low cost. Cast magnet or sintered magnet is selected as the single magnetic body and ferrite, rare earth, MK steel or alnico is used as the material thereof.
According to a preferable embodiment of such a magnetic encoder, a magnetic ring is directly attached to a reinforcing ring with an adhesive to form a magnetic encoder, so that small and compact magnetic encoder can be obtained because of its high magnetic force, thereby remarkably improving the measurement accuracy.
In either case, the magnetic ring is formed such that the single magnetic body or the molded one by mixing a binder in a magnetic powder is attached to the reinforcing ring with an adhesive and S pole and N pole are magnetized. Unevenness or accidental error is not caused in the output accuracy of magnetic pulse signal even when the magnetic ring is out of alignment of the reinforcing ring.
Now, the embodiments of a magnetic encoder of the present invention are explained referring to the attached drawings.
According to the present invention, a magnetic ring 1 is applied with an adhesive 2 such as cyano, epoxy, phenol, rubber, or polyurethane system and is fixed and integrated with a reinforcing ring 3, thus forming a magnetic encoder. If silicone sealant is used as the adhesive 2, it prevents generation of gap, distortion, and deformation, and functions further as a buffer material.
When a plate made of a magnetic material such as cold-rolled steel (SPCC) and SUS430 is used for the reinforcing ring [[2]] 3 supporting the magnetic ring 1, the magnetic field is enlarged to increase the magnetic force.
If a tarnishable material such as neodymium, steel, boron/samarium or nitrogen is used for the magnetic ring 1, it is better to provide a coating or galvanizing treatment on its surface. Or the magnetic ring 1 is covered with a protective cover 4 made of a nonmagnetic material (aluminum, plastic, nonmagnetic austenitic stainless steel like SUS304, SUS301) in order to protect against scattering moisture and foreign material, as shown in
The protect cover 4 is fitted to the magnetic ring by crimping 6 in a manner that the extending edge of the cover is bent to join together as shown in
Soft material such as rubber, plastic, cloth, nonwoven fabric, paper may be used as the cushioning material 5.
In the embodiment of
A preferable embodiment which is incorporated into a sealing unit is explained.
The vehicle axle has an inner member 10, an outer member 20, a rolling element 30 housed between the inner member 10 and the outer member 20, and a pair of sealing units 50 and 50′ for sealing the annular end space between the inner member 10 and the outer member 20. The magnetic encoder A(#1) of the present invention (mentioned later) is attached to the sealing unit 50. A magnetic sensor 8 is provided so as to face the magnetic ring 1 of the magnetic encoder A(#1) as shown in
The inner member 10 and the outer member 20 of the bearing unit have orbit surfaces 10a and 20a of the rolling element 30 respectively and each surfaces are formed like a groove.
The inner member 10 and the outer member 20 are an inner circumferential member and an outer circumferential member via the rolling element 30 respectively and they are rotatable with each other. However, they may be single one like a bearing shaft washer or a bearing housing washer, or may be a combination of a bearing shaft washer or a bearing housing washer with other member.
The inner member 10 may be an axle and the rolling element 30 may be a ball or a roller. In this embodiment a ball is used.
The wheel axle is constructed as an antifriction bearing with double row, more specifically an angular ball bearing with row. The bearing shaft washer is comprised of a pair of dividable shaft washers 10A and 10B which are formed with the orbit surfaces 10a and 10a of the rolling element row respectively. The shaft washers 10A and 10B are fitted in the external circumference of the axle of a hub wheel 60 to constitutes the inner member 10.
The inner member 10 may be comprised of two members, namely a hub wheel with an orbit surface formed by integrating the hub wheel 60 and one shaft washer 10B and other shaft washer 10A, in spite of comprised of three members, namely the hub wheel 60 and a pair of dividable shaft washers 10A and 10B.
One end (for example a housing washer) of an universal joint with uniform velocity 70 is connected to the hub wheel 60 and a vehicle wheel (not shown) is attached to a flange 60a of the hub wheel 60 with a bolt.
The reference numeral 70 indicates an universal joint with uniform velocity and its other end (for example a shaft washer) is connected to a driving wheel (not shown). The outer member 20 is comprised of a bearing housing washer and is attached to a housing (not shown) comprised of a knuckle of a suspension. The rolling element 30 is supported by a retainer 40 per each row.
The magnetic encoder A(#1) of the present invention is provided for one sealing unit 50 of thus constructed vehicle wheel to generate pulse code by the magnetic force. The magnetic ring 1 constitutes the magnetic encoder A(#1) together with the reinforcing ring 3 and magnetic poles N and S are alternately formed around its circumference. The magnetic poles N and S are formed in with a predetermined pitch at a pitch diameter (PCD).
The sealing unit 50 has the reinforcing ring 3 and a fixing member 7 attached to the inner member 10 and the outer member 20 respectively. The reinforcing ring 3 and the fixing member 7 are provided so as to oppose each other to form the letter L with cylindrical portions 31, 71 and vertical plates 32, 72 respectively. According to the present invention, the vertical portion 32 of the reinforcing ring 3 is formed outside of the bearing and the magnetic ring 1 is provided via the adhesive 2 at the outside of the plate 32 as a slinger. A sealing member 9 is vulcanized and integrated at the fixing member 7.
In these figures, the common members to
The encoder A shown in
The magnetic encoder B shown in
According to either one of these magnetic encoders A and B, the magnetic ring 1 is fixed with the reinforcing ring 3 with an adhesive 2 and the magnetic poles S and N are alternately magnetized around its circumference. Therefore, unevenness or accidental error is not caused in the output accuracy of magnetic pulse signal even when the magnetic ring 1 is out of alignment with the reinforcing ring 3. According to these embodiments, a sealant with a cushioning ability is used as an adhesive and a cushioning material is used between the magnetic ring 1 and the protective cover 4, so that even when improvident pressure is applied or foreign material is bit in case of assembling, the cushioning material achieves a buffer action.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-144383 | May 2003 | JP | national |
This application is a Divisional of U.S. patent application Ser. No. 10/850,108 which was filed on May 21, 2004.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10850108 | May 2004 | US |
| Child | 11724181 | Mar 2007 | US |
