I ' FIELD OF INVENTION
The invention relates to the speed sensing devices and in particular relates
to a brake disc mountable wheel speed sensing device for two wheelers.
BACKGROUND OF THE INVENTION
The statements in this section merely provide background information
related to the present disclosure and may not constitute prior art(s).
I - . Generally, a two wheeler is provided with a speed sensing device, mainly
sensors, for detecting the rotational condition (such as rotational speed) of the
wheel. Typically, the speed sensor is provided adjacent to a rotary member that
rotates together with the wheel. The speed sensor picks up fluctuations in the
magnetic field developed due to rotation of the wheel, converts such fluctuations
I to electrical signals and outputs the electrical signals to a display instruments such
as a speedometer. The rotary member may be a rotor in the form of a pulse ring
I
made of a ferromagnetic material and having teeth (protrusions) formed on the
outer periphery thereof, or a pulse ring having its outer periphery magnetized so
that N and S poles appear circurnferentially alternating with each other. The rotors
contain a magnetic material wherein the speed sensors such as Hall ICs (fitted in a
printed circuit board) and magneto resistive elements are used to detect the
rotation of the rotors. Generally, the printed circuit board face having Hall IC is
inserted in a plastic housing in such a way that the Hall IC comes in fiont of the
magnet and alternately faces the N and S poles position of the magnet. The said
plastic housing is formulated with a channel provided with an internal groove and
an insert-molded sensor casing press which is press-fitted in the channel of the
housing. The insert-molded sensor casing is further provided with atleast one
pokayoke positioning rib provided on the lower side of the insert-molded sensor
casing to correctly guide the insert-molded sensor casing into the channel of the
housing. Precautionally, the plastic housing is further provided with a stopper lip -
with the insert-molded sensor casing to get locked in the internal groove of the
housing.
However, such 'wheel speed sensors integrated with Hall ICs invite a huge
cost in, terms of the application of atleast one Hall IC, the assembly cost, plurality
of components required, and many more. Additionally, the complexions involved
in the manufacturing of the wheel speed sensors integrated with Hall ICs demand
the assembly of a lot of components, thus increasing the assembly time and thus'
reducing the productivity and efficiency of the manufacturing process. Moreover,
the wheel speed sensors integrated with Hall ICs stress on positioning the Hall ICs
on the wheel hub that requires extreme precision in its placement considering the
fact that the wheel is in constant rotation. As a result, there exits a possibility that
the positional relationship between the Hall ICs positioned in the wheel speed
scnsor and the vehicle may get changed asking for troubled speed detection
visible in the speedometer.
Hence, there is ,an urgent need of a reliable, simple, stable, efficient, and
less costly speed sensing device for two wheelers to overcome the above
mentioned drawbacks available withlhe present speed sensing devices.
BRIEF SUMMARY AND OBJECTIVES OF THE INVENTION
The present subject matter relates to a reed switch based wheel speed
sensor for two wheelers. The said reed switch based wheel speed sensor mainly
includes a reed switch sensor . a.s sembly held by a bracket 'welded on a fiont
suspension of the two wheeler and a magnet assembly fitted on one of the holes
- provided on a brake disc mounted on a side' surface of the fiont.whee1 of the two
wheeler in an integrally rotatable manner in a way that the magnet assembly
always faces the reed switch sensor assembly during each rotation of the brake
disc. The reed switch sensor assembly is structured with a hermetically sealed
reed switch encompassed inside a collar structured within a plastic threaded
barrel. The reed switch sensor assembly also includes a jumper wire attached to
one end of the hermetically sealed reed switch for electrically connecting the reed
switch to a vehicle information display instrument via a wire harness.
Operationally, the reed switch sensor assembly sense the number of rotation of the
wheel to accordingly generate pulse signals that is subsequently conveyed to a
microcontroller programmed to display the generated pulse signals in terms of
revolution per minute (rpm) on a liquid crystal display (LCD) screen or a thin film
transistor (TFT) screen @ a vehicle information displ'ay instrument of the two
wheeler. The subject matter explains that the magnet assembly comprises of a
magnet caulked in a magnet holder wherein the magnet holder is fastened on the
brake disc by a circlip.
An object of the present invention is to glue the magnet into the magnet
holder.
Another object of the present invention is to fasten the magnet'holder on
the brake disc with a circlip.
Another object of the present subject matter is to fill the open side of the
plastic threaded barrel with epoxy in order to avoid the entry of unnecessary
external elements such as air, water, dust, and the like.
Another objective of the present subject matter is to provide the collar with
an externally designed guiding sleeve for uniformly guiding the jumper wire '.
through the guiding sleeve and demarcating the jumper Wire from bare wires.
Yet another objective of the present subject matter is to provide the brake
disc with multiple magnet assemblies depending on requirement, response time of
the pulses generated, efficiency, cost and the like.
Yet another objective of the present subject matter is to display the
revolution per minutes of the rotating wheel on a liquid crystal display (LCD)
screen or a thin film transistor (TFT) screen.
Yet another objective of the present subject matter is to structure the wire
harness with an insulated wire protected in a sleeve and a coupler receiving the
insulated wire.
Yet another object of the present invention is to provide an easy, reliable,
efficient and less costly speed sensing device.
BRIEF DESCRIPTION OF DRAWINGS
The summary narrated above and the following detailed description of the
invention can be understood with the drawings appended to this claim. The
illustrations provide the details of the invention. However, it should be understood
that the invention is not limited to the arrangements shown. In the drawings:
FIG. 1 show a perspective view of a two wheeler in an embodiment of the present
subject matter.
FIG. 2A and FIG. 2B show perspective views of a reed switch based wheel speed
sensor mounted on a brake disc of a wheel of a two wheeler in an embodiment of
the present subject matter.
FIG. 3A shows a perspective view of a reed switch based wheel speed sensor in
an embodiment of .the present subject matter.
FIG. 3B shows a cross sectional view of a reed switch based wheel speed sensor
in an embodiment of the present subject matter.
FIG. 4 shows a perspective view of a.collar provided within a reed switch based
wheel speed sensor in an embodiment of the present subject matter.
FIG. 5 shows a perspective view of a magnet assembly in an embodiment of the
present subject matter.
FIG. 6 shows a perspective view of a magnet assembly fitted on a brake disc in an . ,
embodiment of the present subject matter. '
FIG. 7 shows a perspective view of a circlip in an embodiment of the present
subject matter.
DETAILED DESCRIPTION OF THE INVENTION
The embodiments of the present subject matter are described in detail with
reference to the accompanying drawings. However, the present subject matter is
not limited to these embodiments which are only provided to explain more clearly
the present subject matter to the ordinarily skilled in the art of the present
disclosure. In the accompanying drawings, like reference alphabets and numerals
are used to indicate like components.
The invention relates to the speed sensing devices and in .particular relates
to a brake disc mountable wheel speed sensing device for two wheelers. The
following description is merely exemplary in nature and is not intended to limit
the present disclosure, application, or uses. The present invention will hereinafter
be described in detail below as applied to a motor cycle 100. However, the
principles of the present invention are also applicable to other two wheelers such
as scooter, scooty, moped and other two wheelers equipped with a vehicle '
information display instruments. Upward, lower, front and rear directions (see the
directions indicated by the arrows in FIG. 1) will be described with respect to
directions as seated by the rider on the motorcycle 100. Generally, there are two
types of speed sensing devices commonly used, one is passive wheel speed
sensing device and another is active wheel speed sensing device. Compared with
the passive wheel speed sensing device, the active wheel speed sensing device has
the relatively small 'volume, light weight, high integration level, great antiinterference
capacity, and other advantages. Thus, the active wheel speed sensing .
device becomes more and more popular.
FIG. 1 illustrates a two wheeler 100 that include a he1 tank 102 and an
engine mounted ahead of a rider's seat 104, a frame 106 and two relatively large
sized wheels 108 on which the frame 106 fides. The structure is necessarily
provided with a pair of left and right front fork members rotatably supported by a
head pipe 110 on the front end of the vehicle frame. The steering of the two
wheelers PO0 is possible via a front wheel which is mounted on the front fork
member whereas the rear wheel (drive wheel) is at the' rear end. FIG. 1 shows a
handlebar 112 secured to an upper portion of the front fork member, and the front
and rear portion of the handle bar 112 is covered with a handle cover which is
further divided jnto forward and backward portions. The two wheeler 100 are also
provided with various lights mounted externally on the vehicle to indicate certain
information about the vehicle to other drivers and pedestrians. These lights mainIy
include brake lights and tail lights besides indicator light bulbs which are provided
to indicate the driving direction of the two wheelers. The two wheeler 100 is
further provided with' the intelligent vehicle information display instrument 114
(also known as a speedometer) located between the handle bars 112 of the two
wheeler 100. The vehicle information display instrument 114 may be viewable by
the rider of the motor cycle 100 when the rider is seated on the seat 104 and
operating the vehicle 100. The vehicle information display instrument 114 may be
disposed generally in fiont of the rider so that the rider can inspect or view a
variety of information that form part of the vehicle information display instrument
114, which information may indicate an operating condition or conditions of the
vehicle. The vehicle information display instrument. 114 may be provided with
audio/visual warning indicators comprising information such as speed, the he1
level, telephone, bluetooth, rpm of the engine, tell tale symbols, turn signal
indicator, hazard warning indicator and / or other indicators. FIG. 1 further shows
a brake disc 116 mounted at the end of an input shaft protruding, from the center
of the wheel 108 and mounted on a side surface of the wheel 108 of the two ,
wheeler 100 in an integrally rotatable manner. The brake disc 116 is provided
with a brake that apply braking force to the brake disc 116 which consequkntly
apply the same braking force on the wheel 108 to instantly stop the moving
vehicle 100.
FIG. 2A illustrates an assembled view of a reed switch based wheel speed
sensor 118 mounted on the brake disc 116 of the wheel 108 of vehicle 100, in an
embodiment of the present subject matter. The reed switch based wheel speed
sensor 118 is assembled with mainly, two parts i.e. a reed switch sensor assembly
120 and a magnet assembly 122. In an embodiment of the present subject matter,
FIG. 2A discloses that the reed switch sensor assembly 120 is held by a bracket
I24 welded on a fiont suspension 126 which is also known as fork of the vehicle.
In an embodiment of the present subject matter, the magnet assembly 122 is fitted
into one of the holes 128 already designed in the brake disc 116 .of the wheel 108.
The welded reed switch sensor assembly 120 always faces the magnet assembly
122 once in a complete rotation of the brake disc 116 and the wheel 108 depicted
in FIG. 2B, as discussed later.
FIG. 3A illustrates an assembled view of the reed switch based wheel
speed sensor 118 in an cmbodiment of the present subject matter. The reed switch
sensor assembly 120, of the reed switch based wheel speed sensor 118, is mainly
structured of a threaded barrel 130 that encompasses a collar 132 to further covers
a reed switch 134 as shown in FIG. 3A. Generally, the reed switch 134 comprises
of a pair of contacts (not shown) on ferrous metal reeds in a hermetically sealed
glass envelope. The contacts may be normally open, closing when a magnetic
field is present, or normally closed and opening when a magnetic field is applied.
Further, the contacts are separated by a small gap when the switch is open. The
threaded barrel 13.0 covering the reed switch 134 (as shown in FIG. 3B) is made
of plastic in a unique embodiment of the present subject mkter. The reed switch
134 is connected to a jumper wire 136 to establish an electrical connection
between the reed switch 134 and the vehicle information display instrument 114
in an cmbodimcnt of thc prcscnt subject matter. The said electrical connection is
set via a wire harness 138 that includes an insulated wire 140 protected in a sleeve
142 and a coupler 144 receiving the insulated wire 140 as shown in FIG. 3B. In
an embodiment if the present subject matter, one side of the threaded barrel 130 is
sealed with epoxy in order to avoid the entry of any unnecessary external
elements, such as but not restricted to, water, dust, air, and the like. In an
embodiment of the present subject matter, the external part of the collar 132 is
provided with a guiding sleeve 146 (as shown in FIG. 4) for uniformly guiding
the jumper wire 136 through the guiding sleeve 146 to get connected to the reed
switch 134 as explained later. The guiding sleeve 146 also demarcates any bare
wires connected to the reed switch 134 inside the collar 132 from the jumper wire
136 that consequently diminishes any chances of short-circuit between the wires
which may lead to the transmission of incorrect signals to the vehicle information
display instrument 114 in an embodiment of the present subject matter. The
jumper wire 136 may be replaced with a short electrical wire that can . . provide an
electrical connection from anywhere on the breadboard to the input/output pins of
a microcontroller (not shown) provided with an electronic circuit (not shown) of
.the vehicle information display instrument 114 of the two wheeler 100.
FIG. 5 illustrates the magnet assembly 122 fitted into one of the holes 128
already designed in the brake disc 116 of the wheel 108 of the two wheeler 100.
The magnet assembly ,122 comprises of a magnet 148 and a magnet holder 150
wherein the magnet 148 is positioned in the magnet holder 150 in a way that the
shaped portion of the magnet 148 is aligned along the. corresponding shaped
magnet holder 150 to limit the movement of magnet 148 inside the magnet holder
150 during the movement of the two.wheeler 100. In a preferred embodiment of
the present subject matter, the magnet holder 150 is circular in shape. However,
the shape of the magnet holder 150 is not restricted within the scope of the present
subject matter. The magnet 148 is aligned inside the magnet holder 150 in a way
that it restricts the radial and axial movement of the magnet 148 inside the magnet
holder 150. In an embodiment of the present subject matter, the magnet 148 is
caulked into the magnet holder 150 to further hold the magnet 148 inside the
magnet holder 150. In another embodiment of the present subject matter, the
magnet 148 may be glued inside the magnet holder 150 instead of caulking the
magnet 148 into the magnet holder 150. The magnet holder 150, according to the
present subject matter, is fitted on the brake disc 116 of the wheel 108 of the two
wheeler 100 (as shown in FIG. 6) with a circlip 152 (as shown in FIG. 7) that is
fastened on the magnet holder 150 to the lateral movement of the magnet
holder 150 and thus the magnet assembly 122. In an embodiment of the present
subject matter, the shape of the circlip 152 is not restricted within the scope of the
present subject matter.
Operationally, the reed switch based wheel speed sensor 118 is fitted on
the brake disc 116 of the wheel 108 of the two wheelers 100 to sense the
rotational speed of the vehicle 100. As mentioned above, the said reed switch
based wheel speed sensor 118 is structured of the reed switch sensor assembly
120 and the magnet assembly 122 wherein the reed switch sensor assembly 120 is
held by the bracket 124 welded on the fiont 'suspension 126 of the two wheeler
100. The reed switch sensor assembly 120 always focus the magnet assembly 122
fitted in one of the holes I28 already provided with the brake disc PI6 of the
wheel 108. The reed switch sensor assembly 120 and the magnet assembly 122
faces each other once during each rotation of the wheel of the two wheeler.
During their facing of each other, the reed switch 134 provided within the reed
switch sensor assembly 120 is qualified to sense the magnet 148 encompassed
within the magnet assembly 150 on each rotation of the wheel during the
movement of the motor cycle 100. The reed switch 134 senses the number of
rotation' of the wheel 108 and accordingly generate pulse signals (corresponding
to the rotation of the wheel) in terms of the revolution per minute conveyed to a
microcontroller (not shown) provided with the vehicle information display
-
instrument 114 of the 'two wheeler 100. The said revolution per minute is
displayed on a liquid crystal display screen or a TFT screen (not shown) in the
vehicle information display instrument 114 of the two wheeler. .In an embodiment
of the present subject matter, the brake disc 116 may be equipped with multiple
magnet assemblies on the only brake disc 116 at regular intervals depending on
the parameters such as requirement, response time of the pulses generated,
efficiency, cost and many more.
The reed switch based wheel speed sensor 118 in accordance with the
present subject matter advantageously facilitates a less costly way of generating
pulses with the help of reed switch 134 and magnet 1.48 in conlparison to the
usage of Hall ICs as discussed in the background section of the present subject
matter. Additionally, the absence of plurality of components in the reed switch
based wheel speed sensor 118 diminishes the complexities involved in
manufacturing the same. This leads to an increased efficiency and productivity of
the manufacturing process of the wheel speed sensing device. Further; such reed
switch based wheel speed sensor 118 overcomes the drawback of displacement
and re-positioning of the sensing device during the movement of the wheel 108 of
the two wheeler. Furthermore, the option of plurality of magnet 148 assemblies on
the single brake disc 116 may harness the required amount of efficiency of the
reed switch based wheel speed sensor 118 according to the present subject matter.
It will be appreciated by those skilled in the art that changes could be
made to' the embodiments described above without departing fiom the broad
inventive concept thereof. The present embodiments are therefore to be .
considered in all respects as 'illustrative' and not restrictive, the scope of the
invention being indicated by the appended claims rather 'than by the foregoing
description and all variations, substitutions and changes which come within the
meaning and range of equivalency of the claims are therefore intended to be
embraced therein.

WE CLAIM:
1. A reed, switch based wheel speed sensor 118 in two wheelers 100
comprising:
a reed switch sensor assembly 120 held by a bracket 124 welded on a fiont
suspension 126 of the two wheeler 100;
a magnet assembly 122 fitted on one of the holes 128 provided on a brake
, disc 116 mounted on a side surface of the front wheel 108 of the two
wheeler 100 in an integrally rotgable manner in a way that the magnet
assembly 122 always faces the reed switch sensor assembly 120 during
each rotation of the brake disc 116; wherein the reed switch sensor
assembly 120 comprises of; .
a hermetically sealed reed switch 134 encompassed inside a collar
132 . structured within a threaded barrel 130; .
a jumper wire 136 attached to one end of the hermetically sealed
reed switch 134 for electrically connecting the reed, switch 134 to a
vehicle information display iqstrument 114 via a wire harness 138;
the reed switch sensor assembly 120 sense the number of rotation of the
wheel, 108 to accordingly generate pulse signals that is subsequently
conveyed to a microcontroller programmed to display the generated pulse
signals in terms of revolution per minute (rpm) on a vehicle information
display instrument 114 of the two wheeler 100.
2. The reed, switch based wheel speed sensor 118 as claimed in claim 1,
wherein the magnet assembly 122 comprises of a magnet 148 caulked in a
magnet holder 150.
3. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the magnet 148 may be glued into the magnet holder 150.
4. The reed switch based whe'el speed sensor 118 as claimed in claim 1,
wherein the magnet holder 150 is fastened on the brake disc 116 by a
circlip 152.
5. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the threaded barrel 130 is made of plastic.
6. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the open side of the threaded barrel 130 is filled with epoxy to
avoid the entry of unnecessary external elements such as air, water, dust,
and the like.
7. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the collar 132 is externally provided with a guiding sleeve 146
for uniformly guiding the jumper wire 136 through the guiding sleeve 146
and demarcating the jumper wire 136 from bare wires.
8. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the brake disc 116 may be provided with multiple magnet
assemblies depending on requirement, response time of the pulses
generated, efficiency, cost and the like.
-
9. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the revolution per minute (rpm) of the moving wheel 108 is
displayed on a liquid crystal display (LCD) screen or a thin film transistor
(TFT) screen.
10. The reed switch based wheel speed sensor 118 as claimed in claim 1,
wherein the wire harness 138 includes an insulated wire 140 protected in a
sleeve 142 and a coupler 144 receiving the insulated wire.