FIELD OF INVENTION
The invention relates to the speed sensing devices and in particular relates to
the wheel hub mountable 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).
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 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 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
circumferentially 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 fi-ont of the magnet and alternately faces the N and S poles
position of the magnet. Although, there is no issue while inserting the printed circuit
board into the plastic housing, however due to unintentional reverse insertion of the
printed circuit board into the plastic housing, there are always the chances of the nonfunctional
of Hall IC (due to such assembly mistakes) leading to loss of productivity
too.
Further, such wheel speed sensors are necessarily provided with a very
sophisticated grade of synthetic resin filled into the plastic housing after inserting the
printed circuit board into the plastic housing to seal and protect the assembly of
printed circuit board fi-om water, mud, dust, etc. However, this synthetic resin has its
own setting time which is atleast 10 to 15 hours. Additionally, the setting of the
synthetic resin with the printed circuit board demands the plastic housing to be hold
in vertical position and that too amidst high temperature (in the range of 100 to 130
degree Celsius) in plurality of ovens. This leads to decreased productivity of the
products inviting manual errors as there is a constant risk of trickling of the synthetic
resin if the housing (holding the synthetic resin) gets disturbed or overturned during
the process. Moreover, the need of high temperature requires huge costs in terms of
set up (blowers, vibrators, and the like) as well as power consumption.
Hence, there is an urgent need of a reliable, leak-proof, stable, and less costly
speed sensing device for two wheelers to overcome the above mentioned drawbacks
available with the present speed sensing devices.
BRIEF SUMMARY AND OBJECTIVES OF THE INVENTION
The present subject matter relates to a wheel speed sensing device in two
wheelers wherein the speed sensing device is provided with a housing formulated
with a channel provided with an internal groove and an insert-molded sensor casing
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 charmel of the housing. The present subject matter discloses a stopper lip
provided with the inert-molded sensor casing to get locked in the internal groove of
the housing. The speed sensing device, according to the present subject matter, is
reliable, efficient, and less costly.
An object of the present invention is to calibrate the housing with a magnet
mapped at the centre of the housing in a manner that the magnet is maintained at an
appropriate distance from the printed circuit board.
An object of the present invention is to mold the sensor casing by a low
pressure insert molding process.
An object of the present invention is to mold the housing and the sensor
casing with thermoplastic or thermoset plastic.
An object of the present invention is to devise the housing with a channel to
receive the insert-molded sensor casing.
An object of the present invention is to include the sensor casing with the
printed circuit board and the wire cord.
An object of the present invention is to electrically connect the wire cord to
the pre-determined locations on the printed circuit board.
Yet another object of the present invention is to arrange the printed circuit
board within the channel and fixed after filling over with a sealing synthetic material.
Yet another object of the present invention is to provide the insert-molded
sensor casing with a stopper lip to get pressed fit into the groove, provided within the
housing, when assembled.
Yet another object of the present invention is to uniquely provide the insertmolded
printed circuit board with atleast one poka-yoke positioning rib.
Yet another object of the present invention is to position the poka-yoke
positioning rib at the middle of the lower side of the printed circuit board.
Yet another object of the present invention is to position the poka-yoke
positioning rib distant from the middle of the lower side of the printed circuit board.
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 shows a perspective view of a speed sensing device mounted on the hub of the
wheel of the two wheelers in an embodiment of the present subject matter.
FIG. 2 shows a perspective view of the insert molded sensor casing in an
embodiment of the present subject matter.
FIG. 3 shows a perspective view of the assembly of the printed circuit board
connected with the wire cords in an embodiment of the present subject matter.
FIG. 4 shows a perspective view of the insert molded sensor casing provided with a
positioning rib in an embodiment of the present subject matter.
FIG. 5 shows the method of assembly of the sensor casing and the housing in an
embodiment of the present subject matter.
FIG. 6 shows an assembled view of the speed sensing device 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 present invention relates to a speed sensing device, especially to the
speed sensing device mounted on the hub of the wheels of two wheelers. The
following description is merely exemplary in nature and is not intended to limit the
present disclosure, application, or uses. 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 anti-interference capacity, and
other advantages. Thus, the active wheel speed sensing device becomes more and
more popular. The existing active wheel speed sensing device mainly comprises a
sensing element such as a Hall IC on a printed circuit board, a wired cable electrically
connected to the sensing element via an H-terminal, an overmold for receiving these
components and an insulating housing for encapsulating the molded part.
In an embodiment of the present subject matter, FIG. 1 illustrates a
perspective view of the speed sensing device 100 which is mainly comprises of a
sensor casing 102 adapted to be press fitted in an insulated housing 104. In a
preferred embodiment of the present subject matter, the housing 104 is assembled
with a magnet 106 mapped at the centre of the housing 104 in a manner that the
magnet 106 is maintained at an appropriate distance from the printed circuit board
108 (Hall IC) insert-molded in the sensor casing 102, as discussed later. The sensor
casing 102 is insert-molded by a low pressure insert molding process in an
embodiment of the present subject matter. The housing 104 and the sensor casing 102
may be molded with thermoplastic or thermoset plastic. In an embodiment of the
present subject matter, the housing 104 is devised with a channel 110 to receive the
insert-molded sensor casing 102 (shown in FIG. 2).
FIG. 2 illustrates a perspective view of the sensor casing 102 in an
embodiment of the present subject matter. The sensor casing 102 comprises of the
insert molded printed circuit board 108 positioned at one end of the sensor casing 102
in an embodiment of the present subject matter. In an embodiment of the present
subject matter, the sensor casing 102 is also provided with a wire cord 114 which
serves to supply electricity to the sensing element and transmit an output signal from
the sensing element to an indicating instrument (not shown) (for example, a
speedometer). In an embodiment of the present subject matter, the wiring cord 114 is
electrically connected to predetermined locations on the printed circuit board 108 by
soldering, as evident from FIG. 3. Such soldered printed circuit board 108 is arranged
within the charmel 110 and fixed after filling over with a sealing synthetic material
such as but not restricted to an epoxy resin, or the like, as discussed later. In an
embodiment of the present subject matter, FIG. 2 shows that the insert-molded sensor
casing 102 is advantageously provided with a stopper lip 122 which subsequently
gets press fitted into a groove 116, provided within the housing 104, when assembled.
6
FIG. 4 illustrates another embodiment of the present subject matter in which
lower side 118 (the side which is not exposed to the rotating magnet 106) of the
insert-molded printed circuit board 108 is uniquely provided with atleast one pokayoke
positioning rib 120 that advantageously facilitates in avoiding human mistakes
during inserting the insert-molded printed circuit board 108 into the housing 104. In
an embodiment of the present subject matter, the poka-yoke positioning rib 120 is
positioned at the middle of the lower side 118 of the printed circuit board 108. In
another embodiment of the present subject matter, the poka-yoke positioning rib 120
maybe positioned distant from the middle of the lower side 118 of the printed circuit
board 108. This poka-yoke positioning rib reduces the chance of reverse insertion of
the printed circuit board and thus raising the overall productivity too.
During assembly, the sensor casing 102 (which mainly comprises of the
insert-molded printed circuit board 108 and the wire cord 114) is adapted to press fit
into the channel 110 devised in the housing 104. The sensor casing 102 is guided (by
the positioning rib 120) along a positioning slot 112 provided interior to the housing
104. Further, the stopper lip 122 provided with the molded sensor casing 102 gets
tightly locked in the interior groove 116 provided within the channel 110 of the
housing 104 as shown in FIG. 5. The channel 110 before receiving the sensor casing
102 is filled with the synthetic material such as, but not restricted to, epoxy resin.
Thereafter, on filling the channel 110 with the epoxy resin, the sensor casing 102 is
pressed fit into the housing 104 to get the combination of epoxy and the molded
printed circuit board 108 solidified. Additionally, this pressed fit arrangement
guarantees a leak proof display in terms of water, resin, dust, and the like. Moreover,
the printed circuit board 108 is already covered with the insert-molded structure that
uniquely protects the soldering and electrical connection from being affected by the
presence and solidification of the epoxy resin. FIG. 6 ftirther shows the location of
the positioning rib 120 embedded on the opposite side of the sensing part of the
printed circuit board 108 facing the rotating magnet 106.
The speed sensing device 100 in accordance with the present subject matter
advantageously facilitates the press fit grooved arrangement that subsequently
ensures a leak proof arrangement as necessarily required during the assembly in the
speed sensing device 100. Further, the press fit arrangement holds the epoxy resin
inside the sealed channel 110 of the housing 104 and thus consequently the speed
sensing device 100 can be left open for drying/solidifying the epoxy without any need
of high temperature in plurality of ovens. In other words, such wheel speed sensor
reduces the holding time of the housing in ovens required for drying. This, as a result
of, decreases the overall power consumption in manufacturing of the speed sensing
device 100. Furthermore, the sealed channel 110 rejects any chance of trickle in
epoxy resin, thus resulting in a fearless cooling of the epoxy resin. Additionally, the
present subject matter increases the productivity of the speed sensing device 100 as
the solidifying process does not require the ovens to get free for further uses.
Moreover, the insert-molding in the assembly is appropriate for simple and easy
mounting with respect to the housing which would not only be effective for proper
installation of the printed circuit board 108 but would also favor simple and easy
release of the printed circuit board 108 required for inspection or replacement. In
other words, the stress, while releasing the printed circuit board 108 would be on the
stopper lip 122 and not on the printed circuit board 108 and/or the wire cord 114.
Furthermore, the presence of the positioning rib 120 perfectly guides the molded
printed circuit board decreasing the non-functioning of the printed circuit board 108
due to failure. The speed sensing device 100 of this present subject matter is thus
directed to serve the diverse and complex requirements of effective speed sensing
devices in the two wheelers and the like.
It will be appreciated by those skilled in the art that changes could be made to
the embodiments described above without departing from 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.
8

7400^14:
- 0 JKH 18W
1. A wheel speed sensing device 100 in two wheelers comprising: *
a housing 104 formulated with a channel 110 provided with an internal groove
116;
an insert-molded sensor casing 102 press fitted in the channel 110 of the
housing 104;
atleast one pokayoke positioning rib 120 provided on the lower side 118 of
the insert-molded sensor casing 102 to correctly guide the insert-molded
sensor casing 102 into the channel 110 of the housing 104;
a stopper lip 122 provided with the inert-molded sensor casing 102 to get
locked in the internal groove 116 of the housing 104.
2. The wheel speed sensing device 100 as claimed in claim 1, wherein the sensor
casing 102 is insert-molded by a low pressure insert molding process.
3. The wheel speed sensing device 100 as claimed in claim 1, wherein the insert
molded sensor casing 102 comprises of a printed circuit board 108 soldered to
a wire cord 114.
4. The wheel speed sensing device 100 as claimed in claim 1, wherein the wiring
cord 114 is electrically connected to predetermined locations on the printed
circuit board 108 by soldering.
5. The wheel speed sensing device 100 as claimed in claim 1, wherein the
sensing part of the printed circuit board 108 always faces the rotating magnet
106.
6. The wheel speed sensing device 100 as claimed in claim 1, wherein the pokayoke
positioning rib 120 is positioned at the middle of the lower side 118 of
the printed circuit board 108.
it M ™'
7. The wheel speed sensing device 100 as claimed in claim 1, wherein the pokayoke
positioning rib 120 is positioned distant from the middle of the lower
side 118 of the printed circuit board 108.
8. The wheel speed sensing device 100 as claimed in claim 1, wherein the
channel 110 is filed with a sealing synthetic material before the sensor casing
102 is inserted in the channel 110 of the housing 104.
9. The wheel speed sensing device 100 as claimed in claim 1, wherein the wiring
cord 114 serves to supply electricity to the speed sensing element and transmit
an output signal from the speed sensing element to an indicating instrument.
10. The wheel speed sensing device 100 as claimed in claim 1, wherein the
housing 104 and the sensor casing 102 is molded with thermoplastic or
thermoset plastic.