Magnetic ring for detecting the rotation of an object

A ring to be attached to a rotating body for producing a magnetic signal in cooperation with a magnetic sensor relative to which the rotating body rotates, comprising: a magnetic ring member having an alternating magnetic property along its circumference consisting of synthetic resin in which magnetic material is dispersed; and a reinforcement ring member which is made of synthetic resin material and substantially surrounds the magnetic ring member. Alternatively, the reinforcement ring may consist of a metallic band which extends the full circumferential surface of the ring. By thus reinforcing the resinous magnetic material, the cost of the ring can be reduced, and the increased mechanical strength of the ring allows easy handling and effective press fitting of the ring. By forming the ring with a plurality of arcuate portions, the stocking and installing of the ring is facilitated.

BACKGROUND OF THE INVENTION 
The present invention relates to a magnetic ring for detecting the rotation 
of an object and in particular to such a magnetic ring making use of 
synthetic resin material in which magnetic particles are dispersed. 
It is often necessary to electrically detect the rotation or rotational 
speed of an object. For instance, it is often desired to measure the 
rotational speed of a shaft in industrial applications, and it is often 
desirable to measure the rotational speed of a wheel in automotive 
applications. For instance, in evaluating the speed of an automobile, one 
can obtain a highly accurate speed reading by measuring the rotational 
speed of a wheel itself; and it is absolutely necessary to measure the 
rotational speed of a wheel in anti-skid control of a brake system. 
In such applications, it has been common to use a toothed gear which is 
mounted on a rotating object and to measure its rotational speed by 
counting pulses generated from a magnetic induction device placed adjacent 
to the toothed gear. Since such a toothed gear is typically press fitted 
into a bore or onto a shaft, it must be capable of withstanding the stress 
arising from such a press fitting, and it is typically made of a metal 
such as steel. Since hobbing of a gear which is a fairly time consuming 
and expensive process, is necessary and a substantial dimensional 
precision is necessary for satisfactory press fitting, such a metallic 
ring for detecting rotational speed tends to be costly. 
Magnetic material consisting of synthetic resin in which ferromagnetic 
powder is dispersed is known and it can be formed into a ring having a 
plurality of gear teeth or magnetized to have alternating magnetic poles 
along its circumference at very low cost. Furthermore, it is substantially 
lighter in weight than a conventional toothed gear ring made of steel. 
However, such material lacks the mechanical strength required for press 
fitting. Such material, particularly in the, form of a toothed gear, is 
prone to damage during assembly and in use, and its reliability and 
durability are insufficient for practical purpose. 
BRIEF SUMMARY OF THE INVENTION 
In view of such problems of the prior art, a primary object of the present 
invention is to provide a ring having a magnetically alternating property 
along its circumference which is inexpensive for manufacture and is yet 
durable and reliable. 
Another object of the present invention is to provide a ring for detecting 
the rotation of an object which is easy to install. 
According to the present invention such objects are accomplished by 
providing a ring to be attached to a rotating body for producing a 
magnetic signal in cooperation with a magnetic sensor relative to which 
the rotating body rotates, comprising: a magnetic ring member having an 
alternating magnetic property along its circumference consisting of 
synthetic resin in which magnetic material is dispersed; and a 
reinforcement ring member which is made of synthetic resin material and 
substantially surrounds the magnetic ring member. 
The resinous magnetic ring member having a magnetically alternating 
property along its circumference according to the present invention may 
consist of a ferromagnetic ring having alternating magnetic poles along 
its inner circumference, outer circumference or end surface which is made 
by molding composite magnetic material which is in turn made by uniformly 
mulling synthetic resin material such as polyamide, polyolefin and 
ethylene copolymer materials with magnetic powder such as barium ferrite, 
strontium ferrite and rare earth magnetic powder, optionally with some 
additives. 
Such a resinous permanent magnetic ring member may typically have ten or 
more N and S poles, and preferably 50 to 200 poles along its 
circumference. The weight ratio of the synthetic resin (I) to the magnetic 
powder (II) in this composite magnetic material may be (I)/(II)=40/60 to 
5/95, preferably (I)/(II)=20/80 to 8/92. 
Preferably, this resinous permanent magnetic ring member is embedded in a 
synthetic resin ring for reinforcement to endow the thus formed ring for 
detecting the rotation of an object with necessary mechanical strength and 
integrity which are necessary for press fitting and easy handling. The 
material for this synthetic resin ring may consist of, for instance, 
polyethylene, polypropylene, polyvinyl chloride, styrene-butadiene 
copolymer, AS resin, ABS resin, polyamide, polyacetal, polycarbonate, 
polyethylene phthalate, polyphenylene sulfide, polyphenylene ether, 
polysulfone, thermoplastic polyurethane, etc. It is preferable to 
reinforce such synthetic resin with glass fiber or other reinforcing 
material. It is also possible to reinforce the synthetic resin ring with a 
metallic ring, extending along its full circumference, which may be press 
fitted to or insert molded with the synthetic resin ring. 
Alternatively, the resinous permanent magnetic ring member having 
alternating magnetic poles along its circumference according to the 
present invention may be replaced by a toothed gear ring having a magnetic 
property as well as a plurality of teeth along its inner circumference, 
outer circumference or end surface which is made by molding composite 
magnetic material which is in turn made by uniformly mulling synthetic 
resin material such as polyamide, polyolefin and ethylene copolymer 
materials with magnetic material such as soft ferrite, iron, iron alloy 
and nickel alloy powder, optionally with some additives. The magnetic 
permeability of this magnetic material may be 5.0 or greater, or 
preferably 10.0 or greater. 
According to another aspect of the present invention, the circumferential 
surface of the ring for detecting the rotation of an object is polygonal 
in shape and is thus prevented from slipping relative to the object to 
which this ring is fitted. 
According to yet another aspect of the present invention, the reinforcement 
ring member is made of metal or alloy material, instead of synthetic 
resin, and extends along the full or whole circumference of the magnetic 
ring member. 
According to yet another aspect of the present invention, there is provided 
a ring to be attached to a rotating body for producing a magnetic signal 
in cooperation with a magnetic sensor relative to which the rotating body 
rotates, comprising: a magnetic ring member having an alternating magnetic 
property along its circumference which comprises at least two arcuate 
parts forming a complete circle through mutual cooperation thereof, 
consisting of synthetic resin in which magnetic material is dispersed; and 
fastening means for holding the arcuate parts together in the state of a 
complete ring. This not only facilitates the work involved in assembling 
and replacing the ring but also improves the convenience in stocking such 
rings as component parts.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
Various embodiments of the magnetic ring for generating a magnetic signal 
according to the present invention are described in the following section 
with reference to the appended drawings. 
FIG. 1 shows a structure for supporting a non-driven wheel of an automobile 
to which a magnetic ring for detecting the rotation of a wheel according 
to the present invention can be applied. The central portion of a wheel 
disc 42 having a flange 41 for a disc brake system is integrally provided 
with an annular boss 43 which projects inwardly towards the center of the 
automobile. The inner circumferential surfaces of a central bore of this 
boss 43 is rotatably supported by the free end of an axle shaft 47 by way 
of a pair of tapered roller bearings 45 and 46. Further, a nut 48 is 
threaded to the outer most part of the free end of this axle shaft 47 by 
way of a washer 49 and holds the mentioned component parts together. 
Numeral 44 denotes one of a number of stud bolts for securing a wheel, not 
shown in the drawing, to the wheel disc 42. 
A ring for magnetically detecting the rotation of a wheel according to the 
present invention may be fitted either onto the outer circumferential 
surface 43a of the boss 43 as denoted by numeral 1 or into an inner 
circumferential surface 42a of a bore of the wheel disc 42 as denoted by 
numeral 1', and a magnetic sensor 38 is fixedly secured to a car body 
portion adjacent to the ring 1, 1'. 
FIG. 2 is an illustrative view showing the working principle of the 
magnetic ring for detecting the rotation of an object according to the 
present invention. The ring 1 is provided with alternating magnetic poles 
at an equal interval along its outer circumferential surface, while the 
magnetic sensor 38 comprises a C-shaped iron core 39 and a coil 40 wound 
on this iron core 39. Therefore, as the ring 1 rotates with the wheel disc 
42, a train of electric current pulses corresponding to the number of 
magnetic poles passing through the vicinity of the iron core 39 are 
induced in the coil 40 and the rotational speed of the ring 1 or the wheel 
disc 42 can be evaluated by counting these pulses. 
FIGS. 3 and 4 show the first embodiment of the ring for detecting the 
rotation of an object according to the present invention. According to 
this embodiment, a permanent magnet ring 2 which is magnetized so that N 
and S poles appear alternatingly along its outer circumferential surface 
is embedded in the middle part of the outer circumferential surface of a 
synthetic resin ring 3. 
The permanent magnet ring 2 may be made by press forming or extruding resin 
material containing ferromagnetic powder dispersed therein in a magnetic 
field into a magnetically either isotropic or anisotropic state, and 
demagnetizing it. Thereafter, this resinous magnetic ring 2 is placed in a 
metallic die and is integrally molded with a synthetic resin compound such 
as polyphenylene sulfide resin compound, preferably containing reinforcing 
material such as glass fiber, by compression molding or injection molding. 
Thus, the permanent magnet ring 2 is embedded in the synthetic resin ring 
3. Then, the resinous permanent magnet ring 2 is magnetized according to a 
desired magnetization pattern with a magnetizer. 
Since the permanent magnet ring 2 is embedded in the synthetic resin ring 3 
which has a much greater mechanical strength than the permanent magnet 
ring 2, the ring 1 for detecting rotation has a sufficient mechanical 
strength to be press fitted onto the shaft 47 as denoted by numeral 1 in 
FIG. 1. Furthermore, the ring 1 thus formed is much lighter in weight than 
a similar conventional ring made of steel or other metallic or oxide 
material. 
In the following description of the different embodiments of the present 
invention, those parts corresponding to the previously described 
embodiments are denoted by like numerals and their detailed description is 
omitted since such description would be redundant and a person skilled in 
the art would not be hindered by such an omission in understanding the 
present invention. 
According to the embodiment shown in FIG. 5, a metallic ring 4 for 
reinforcement covers the whole inner circumferential surface of a 
synthetic resin ring 3, made of synthetic resin material optionally 
containing reinforcing material such as glass fiber, in which a resinous 
permanent magnet ring 2 is embedded in a manner similar to that in the 
embodiment shown in FIGS. 3 and 4. The metallic ring 4 may be attached to 
the ring 1 for instance by insert molding and a groove 4a provided in the 
metallic ring 4 assures a strong bond between the metallic ring 4 and the 
synthetic resin ring 3. Therefore, this embodiment provides an extremely 
high mechanical strength for press fitting. 
FIG. 6 shows yet another embodiment of the present invention. According 
metallic ring 4 having a relatively small height is embedded in the inner 
circumferential surface of a synthetic resin ring 3 in which a permanent 
magnet ring 2 is embedded. 
In the embodiment shown in FIG. 7, a metallic ring 4 for reinforcement is 
attached to an end surface of a synthetic resin ring 3 having a permanent 
magnet ring 2 embedded in the outer circumferential surface thereof, and 
holes 4a provided in the metallic ring 4 assure secure bonding between the 
metallic ring 4 and the synthetic resin ring 3. 
In the embodiment shown in FIG. 8, a pair of metallic rings 4 are attached 
to either end surface of a synthetic resin ring 3 in which a resinous 
permanent magnet ring 2 is embedded in a manner similar to that in the 
embodiment shown in FIG. 7, and holes 4a provided in these metallic rings 
4 assure secure bonding between the metallic rings 4 and the synthetic 
resin ring 2. 
In the embodiment shown in FIG. 9, a cushion or buffer layer 5 which may be 
made, for instance, of natural or synthetic rubber such as silicone rubber 
is interposed between a synthetic resin ring 3 and a resinous permanent 
magnet ring 2. This cushion, layer 5 protects the resinous permanent 
magnetic ring 2 from the stress caused in the synthetic resin ring 3 when 
this ring 1 is press fitted, by preventing the transmission of stress from 
the synthetic resin ring 3 to the resinous magnetic ring 2. 
In the embodiment shown in FIG. 10, a resinous permanent magnet ring 2 is 
embedded and wholly buried in the central portion of a synthetic resin 
ring 3. Therefore, according to this embodiment, the permanent magnet ring 
2 is very well protected from the influences of external elements. 
In the embodiment shown in FIG. 11, a resinous permanent magnetic ring 2 is 
embedded in the outer circumferential surface of a synthetic resin ring 3 
and is further surrounded by a metallic ring 5 which not only protects the 
resinous permanent magnet ring 2 but also increases the overall mechanical 
strength of the ring 1. 
The embodiments which have been described so far are adapted to be fitted 
onto a shaft as denoted by numeral 1 in FIG. 1. 
In the embodiment shown in FIG. 12, a resinous permanent magnet ring 2 is 
embedded in the inner circumferential surface of a synthetic resin ring 3. 
The ring 1 of this embodiment is adapted to be fitted into a bore as 
denoted by numeral 1' in FIG. 1. 
In the embodiment shown in FIG. 13, an end surface of a synthetic resin 
ring 3 has an annular step 3a and a resinous permanent magnetic ring 2 
having an inner circumferential surface that is magnetized into N and S 
poles in an alternating manner is embedded in the vertical wall surface of 
this annular step 3a. The ring 1 of this embodiment is adapted to be 
fitted onto an outer circumferential surface of a rotating object at its 
inner circumferential surface 1a having a smaller diameter that the 
vertical wall surface of the annular step 3a. 
FIG. 14 shows yet another embodiment of the present invention in which 
alternating magnetic poles appear in an end surface of a ring 1 for 
detecting the rotation of an object and, therefore, a magnetic sensor 38 
comprising a C-shaped iron core 39 and a coil 40 wound thereon is disposed 
adjacent to the end surface of the ring 1. FIGS. 15 and 16 show the ring 1 
of FIG. 14 in greater detail. According to this embodiment, a resinous 
permanent magnet ring 2 which is magnetized so that N and S poles appear 
alternatingly along its circumference is embedded in the end surface of a 
synthetic resin ring 3. The resinous permanent magnet ring 2 is 
trapezoidal in cross section and is thus positively attached to the 
synthetic resin ring 1. 
FIG. 17 shows yet another embodiment of the present invention in which a 
plurality of gear teeth 12a are formed along the outer circumferential 
surface of a ring 1 for detecting the rotation of an object and, 
therefore, a magnetic sensor 38 comprising an iron core 39 made of a 
permanent magnet and a coil 40 wound thereon is disposed adjacent to the 
outer circumferential surface of the ring 1. FIGS. 18 and 19 show the ring 
1 of FIG. 17 in greater detail. According to this embodiment, a resinous 
magnetic ring 12 which consists of synthetic resin material such as 
polyamide and magnetic material such as ferrite dispersed therein is 
formed into a toothed gear having the teeth 12a and is embedded in the 
outer circumferential surface of a synthetic resin ring 13 which may be 
made of polypropylene. The inner circumferential surface of the synthetic 
resin ring 13 is adapted to be press fitted onto a rotating object such as 
the shaft 47 shown in FIG. 1. 
According to the embodiment shown in FIG. 20, a metallic ring 14 for 
reinforcement covers the whole inner circumferential surface of a 
synthetic resin ring 13 in which a resinous magnetic ring 12 having a 
plurality of gear teeth 12a is embedded in a manner similar to that of 
FIGS. 18 and 19. The metallic ring 14 may be attached to the synthetic 
resin ring 13 for instance by insert molding and a groove 14a provided in 
the metallic ring 14 assures a strong bond between the metallic ring 14 
and the synthetic resin ring 13. Therefore, this embodiment provides an 
extremely high mechanical strength for press fitting. 
FIG. 21 shows yet an embodiment of the present invention. According to this 
embodiment, a metallic ring 14 having a relatively small height is 
embedded in the inner circumferential surface of a synthetic resin ring 
13, but this embodiment is otherwise similar to that shown in FIG. 20. 
In the embodiment shown in FIG. 22, a metallic ring 14 for reinforcement is 
attached to an end surface of a synthetic resin ring 13, and holes 14a 
provided in the metallic ring 14 assure secure bonding between the 
metallic ring 14 and the synthetic resin ring 13. Otherwise, this 
embodiment is similar to that shown in FIG. 21. 
In the embodiment shown in FIG. 23, a pair of metallic rings 14 are 
attached to either end surface of a synthetic resin ring 13, and holes 14a 
provided in these metallic rings 14 assure secure bonding between the 
metallic rings 14 and the synthetic resin ring 13. Otherwise, this 
embodiment is otherwise similar to that shown in FIG. 22. 
In the embodiment shown in FIG. 24, a cushion or buffer layer 15 which may 
be made, for instance, of natural or synthetic rubber such as silicone 
rubber is interposed between a synthetic resin ring 13 and a resinous 
magnetic ring 12. This cushion layer 15 protects the resinous magnetic 
ring 12 from the stress caused in the synthetic resin ring, 13 when this 
ring 1 is press fitted, by preventing the transmission of stress from the 
synthetic resin ring 13 to the resinous magnetic ring 12. 
In the embodiment shown in FIG. 25, a resinous magnetic ring 12 is embedded 
and wholly buried in the central portion of a synthetic resin ring 13. 
Therefore, according to this embodiment, the toothed resinous magnetic 
ring 12 is very well protected from the influences of external elements. 
In the embodiment shown in FIG. 26, a resinous magnetic ring 12 is embedded 
in the outer circumferential surface of a synthetic resin ring 13 and is 
further surrounded by a metallic ring 14 which not only protects the 
resinous permanent magnetic ring 12 but also increases the overall 
mechanical strength of the ring 1. 
In the embodiment shown in FIG. 27, a resinous magnetic ring 12 is embedded 
in the inner circumferential surface of a synthetic resin ring 13. The 
ring 1 of this embodiment is adapted to be fitted into a bore as denoted 
by numeral 1' in FIG. 1. 
In the embodiment shown in FIG. 28, an end surface of a ring 1 made of 
synthetic resin has an annular step 13a and a resinous magnetic ring 12 
having an inner circumferential surface that is provided with gear teeth 
12a is embedded in the vertical wall surface of this annular step 13a. The 
ring 1 of this embodiment is adapted to be fitted onto an outer 
circumferential surface of a rotating object at its inner circumferential 
surface 1a having a smaller diameter than the vertical wall surface of the 
annular step 13a. 
The embodiment shown in FIG. 29 is similar to that shown in FIG. 24, but 
the resinous magnetic ring 12 is embedded in the inner circumferential 
surface of a synthetic resin ring 13 instead of the outer circumferential 
surface thereof. According to this embodiment, the ring 1 is fitted into a 
hole, as denoted by numeral 1' in FIG. 1, at its outer circumferential 
surface. 
The embodiment shown in FIG. 30 is similar to that shown in FIG. 26 but the 
resinous magnetic ring 12 is embedded in the inner circumferential surface 
of a synthetic resin ring 13 instead of the outer circumferential surface 
thereof. According to this embodiment, the ring 1 is fitted into a hole, 
as denoted by numeral 1' in FIG. 1, at its outer circumferential surface, 
and the metallic ring 14 attached to the inner circumferential surface 
protects the resinous magnetic ring 12 on one hand and reinforces the ring 
1 against the stress arising from press fitting and other external causes. 
Since this metallic ring 14 is made of non-magnetic material such as 
aluminum, it allows passage of magnetic flux therethrough. 
FIG. 31 shows yet another embodiment of the present invention in which a 
plurality of gear teeth 12a is formed on an end surface of a ring 1 
detecting the rotation of an object and, therefore, a magnetic sensor 38 
comprising an iron core 39 made of a permanent magnet and a coil 40 wound 
thereon is disposed adjacent to the end surface of the ring 1. FIGS. 32 
and 33 show the ring 1 of FIG. 31 in greater detail. According to this 
embodiment, a resinous magnetic ring 12 which is formed with a plurality 
of gear teeth 12a along its circumference is embedded in an end surface of 
a synthetic resin ring 13. If desired, the resinous magnetic ring 12 may 
be trapezoidal in cross section for positive attachment to the synthetic 
resin ring 1. 
FIGS. 34 and 35 show yet another embodiment of the present invention. A 
ring 1 for detecting the rotation of an object according to the present 
invention comprises a resinous magnetic ring 12 which is made of a 
synthetic resin such as polyamide and ferromagnetic powder such as ferrite 
dispersed therein and is provided with a plurality of gear teeth along its 
outer circumferential surface. The toothed outer circumferential surface 
of the resinous magnetic ring 12 is surrounded by a metallic ring 14 for 
reinforcement. Since this metallic ring 14 reduces the deformation of the 
ring 1 when being press fitted, the resinous magnetic ring 12 is protected 
from any deterioration from excessive deformation. This metallic ring 14 
is also helpful in preventing foreign material from being caught the gap 
between the teeth 12a or between the teeth 12a and a magnetic sensor. If 
desired, this whole assembly may be enclosed in synthetic resin material. 
Since this metallic ring 14 is made of non-magnetic material, it does not 
substantially affect the pattern of the magnetic field. 
FIGS. 36 and 37 show an embodiment which is similar to that shown in FIGS. 
34 and 35 but differs therefrom in that the gear teeth 12a are formed in 
the end surface, instead of the outer surface, of the resinous magnetic 
ring 12. 
FIGS. 38 and 39 show another similar embodiment according to the present 
invention. A ring 1 for detecting the rotation of an object according to 
the present invention comprises a resinous permanent magnet ring 2 which 
is made of synthetic resin such as polyamide and ferromagnetic powder such 
as ferrite dispersed therein and is magnetized to have alternative 
magnetic poles along its circumference. The outer circumferential surface 
of the resinous permanent magnet ring 2 is surrounded by a metallic ring 4 
for reinforcement. This metallic ring 4 is made of nonmagnetic material, 
it does not substantially affect the pattern of the magnetic field. If 
desired, this whole assembly may be enclosed in synthetic resin material. 
This ring 1 may be fitted either onto a shaft as denoted by numeral 1 in 
FIG. 1 or into a bore as denoted by numeral 1' in FIG. 1. 
In the embodiments shown in FIGS. 40 and 41, a metallic ring 14 having an 
L-shaped cross-section is attached to the outer circumferential and end 
surface of a resinous magnetic ring 12 having a plurality of gear teeth 
12a along their outer circumferential surface and end surface, 
respectively. These rings 1 are adapted to be fitted into a bore as 
denoted by numeral 1' in FIG. 1 at their outer circumferential surfaces. 
The embodiment of FIG. 42 is similar to that shown in FIG. 40 but has a 
resinous permanent magnetic ring 2, which is magnetized to have 
alternating magnetic poles along its circumferential surface, instead of a 
resinous magnetic ring having gear teeth. 
The embodiments shown in FIGS. 43, 44 and 45 are similar to those shown in 
FIGS. 40, 41 and 42, respectively, but metallic rings 14, 4 which are 
shaped like a letter-C cover not only the outer circumferential surfaces 
and one end surface of resinous magnetic rings 12 (FIGS. 43 and 44) and a 
resinous permanent magnet ring 2 (FIG. 45), respectively, but also the 
other end surfaces thereof. 
The embodiments given in FIGS. 43 to 45 are adapted to be fitted into a 
bore as denoted by numeral 1' in FIG. 1, and the metallic rings 14, 4 
ensure the mechanical strength that is required for press fitting. 
According to the embodiments given in FIGS. 46, 47 and 48, metallic rings 
14, 4 for reinforcement are attached only to the inner circumferential 
surfaces of resinous magnetic rings 12 (FIGS. 46 and 47) and a resinous 
permanent magnet ring 2 (FIG. 48), respectively. 
The embodiments shown in FIGS. 49, 50 and 51 are similar to those shown in 
FIGS. 46, 47 and 48, respectively, but metallic rings 14, 4 which are 
shaped like a covers not only the inner circumferential surfaces of 
resinous magnetic rings 12 (FIGS. 49 and 50) and a resinous permanent 
magnet ring 2 (FIG. 51), respectively, but also the one end surfaces 
thereof. 
The embodiments shown in FIGS. 52, 53 and 54 are similar to those shown in 
FIGS. 49, 50 and 51, respectively, but metallic rings 14, 4 which are 
shaped like a letter-C covers not only the inner circumferential surfaces 
and one end surface of resinous magnetic rings 12 (FIGS. 52 and 53) and a 
resinous permanent magnet ring 2 (FIG. 54), respectively, but also the 
other end surfaces thereof. 
The embodiments given in FIGS. 49 to 54 are adapted to be fitted onto a 
shaft as denoted by numeral 1 in FIG. 1, and the metallic rings 14, 4 
ensure the mechanical strength that is required for press fitting. 
According to the embodiments given in FIGS. 55, 56 and 57, metallic rings 
14, 4 cover both the inner and outer circumferential surfaces and the one 
end surfaces of resinous magnetic rings 12 (FIGS. 49 and 50) and a 
resinous permanent magnet ring 2 (FIG. 51), respectively. These 
embodiments are adapted to be fitted either onto a shaft or into a bore as 
denoted by numerals 1 or 1', as the case may be, in FIG. 1, and the 
metallic rings 14, 4 ensure the mechanical strength that is required for 
press fitting 
FIGS. 58, 59 and 60 show different embodiments in which the inner 
circumferential surfaces of resinous magnetic rings 12 are provided with 
gear teeth 12a, and metallic ring 14 cover the outer circumferential 
surface and/or the end surfaces and/or the other end surface of the 
resinous magnetic ring 12. 
FIGS. 61, 62 and 63 show yet other embodiments of the present invention and 
metallic rings 14, 4 cover the one end surfaces of resinous magnetic rings 
12 (FIGS. 61 and 62) and a resinous permanent magnetic ring 2 (FIG. 63), 
respectively. These embodiments are adapted to be fitted either onto a 
shaft or into a bore as denoted by numerals 1 or 1', as the case may be, 
in FIG. 1, and the metallic rings 14, 4 ensure the mechanical strength 
that is required for press fitting. 
FIG. 64 shows yet another embodiment of the present invention. A resinous 
magnetic ring 32 of this embodiment consists of a pair of semicircular 
halves 32a and 32b which can be combined into a complete ring having a 
plurality of gear teeth 32c along its outer circumferential surface. These 
two halves of the ring 1 are held in place on a shaft S (shown in 
imaginary lines in FIGS. 64 and 65) with a metallic ring 24 which 
substantially covers the outer circumferential and end surface of the ring 
1 as shown in FIG. 65. 
FIGS. 66 and 67 show embodiments which are similar to that of FIGS. 64 and 
65 but the embodiment of FIG. 66 has a resinous permanent magnet ring 22 
which is magnetized into alternating magnetic poles along its 
circumference instead of a toothed magnetic ring and the embodiment of 
FIG. 67 has a toothed magnetic ring 32 having a plurality of gear teeth 
32c along its end surface instead of its outer circumferential surface. 
The embodiment shown in FIG. 68 comprises a synthetic resin ring 33 having 
an annular extension 33a and fitted onto a shaft S, a toothed resinous 
magnetic ring 32 embedded in the outer circumferential surface of the 
synthetic resin ring 33 and a metallic ring 24 which is similar to those 
shown in FIGS. 64 to 67 press fitted onto an annular extension 33a of the 
synthetic resin ring 33. The synthetic resin ring 33 as well as the 
toothed resinous magnetic ring 32 consist of a pair of semicircular 
halves, and the metallic ring 24 press fitted onto the extension 33a holds 
them together. 
The embodiment shown in FIG. 69 is similar to that show in FIG. 68 but has 
a resinous permanent magnetic ring 22 which is magnetized to have 
alternating magnetic poles along its circumference, instead of a toothed 
ring, and is embedded in the outer circumferential surface of a synthetic 
resin ring 23. According to the embodiment shown in FIG. 70, a toothed 
resinous magnetic ring 32 having a plurality of gear teeth 32c along its 
end surface is embedded in an end surface of a synthetic resin ring 33 
which is otherwise similar to that shown in FIG. 68. 
The embodiment shown in FIG. 71 comprises a synthetic resin ring 33 
consisting of a pair of semi circular halves 33a and 33b and a resinous 
magnetic ring 32 which is provided with gear teeth 32c along its inner 
circumferential surface and likewise consists of a pair of semicircular 
halves 32a and 32b which are embedded in the corresponding halves 33a and 
33b of the synthetic resin ring 33. This ring 1 for detecting the rotation 
of an object is adapted to be press fitted into a bore B. The embodiment 
shown in FIG. 72 is similar to that shown in FIG. 71 but differs therefrom 
only in that it comprises a resinous permanent magnetic ring 22 which is 
magnetized to have alternating magnetic poles along its circumference, 
instead of a toothed magnetic ring. 
According to the embodiment shown in FIG. 73, the ring 1 for detecting the 
rotation of an object comprises a synthetic resin ring 33 consisting of a 
pair of semicircular halves 33a and 33b and a resinous magnetic ring 32 
which is provided with gear teeth 32c along its outer circumferential 
surface and likewise consists of a pair of semicircular halves 32a and 32b 
which are embedded in the corresponding halves 33a and 33b of the 
synthetic resin ring 33. Furthermore, the synthetic resin ring 33 is 
provided with a plurality of axial through holes 35 and can be secured to 
a shoulder surface or a shoulder surface F with threaded bolts 36 passed 
through these holes 35. According to this embodiment, the ring 1 is fitted 
onto a shaft S but need not be tightly fitted as was the case in previous 
embodiments. 
The embodiment shown in FIG. 74 is similar to that shown in FIG. 73 but 
differs therefrom only in that it comprises a resinous permanent magnet 
ring 22 which is magnetized to have alternating magnetic poles along its 
circumference, instead of a toothed magnetic ring. 
The embodiments shown in FIGS. 75 and 76 are similar to those shown in 
FIGS. 73 and 74, respectively, but differ therefrom in that they are 
fitted into bores B, instead of being fitted onto shafts. 
FIG. 77 shows an embodiment of a metallic ring 24 which can be used to 
fasten together a pair of halves into a complete ring by tightening a 
screw 24a which is passed through the two ends of the metallic ring 24. 
This metallic ring 24 can be conveniently applied to the embodiments shown 
in FIGS. 67 to 70. 
FIG. 78 is a plan view of a ring 1 for generating a magnetic signal in 
which the inner circumferential surface 37 of a synthetic resin ring 3 is 
formed into a polygonal shape so as to prevent a relative free rotation 
between the ring 1 and a corresponding member for press fitting. 
Since the ring for generating a magnetic signal according to the present 
invention makes use of resinous material, it is suitable for mass 
production and light in weight, and, since it is reinforced by a ring 
member which has a great mechanical strength, it would not be damaged when 
press fitted. Furthermore, since the pressure it exerts upon the rotating 
member after press fitting is appropriate, the rotating member will be not 
deformed and no great care is necessary for adjusting the dimensions 
involved in press fitting, thereby improving the facility of manufacture. 
Although the present invention has been shown and described with reference 
to the preferred embodiments thereof, they should not be considered as 
limited thereby. Various possible modifications and alterations could be 
conceived of by one skilled in the art to any particular embodiment, 
without departing from the scope of the invention.