TECHNICAL FIELD
The present invention relates to a magnet holding unit for a gear position sensor.
More particularly, the present invention relates to a locking system for magnet in
the magnet holder of a gear position sensor.
BACKGROUND
The information in this section merely provide background information related to
the present disclosure and may not constitute prior art(s).
A magnet holder unit is being widely used in gear position sensors of vehicles.
The gear position sensor comprises of a magnet assembled inside the magnet
holder, and a Hall IC mounted on a PCB assembly which is located inside
housing. The function of the magnet holder is to hold the magnet firmly so that the
gear position sensor provides the correct output signal specification characteristic
to ECU and it will show correct gear position at the display unit of a vehicle.
In existing techniques, magnet is assembled in the magnet holder by pressing
magnet in pocket provided in magnet holder as illustrated in Figure 1a and 1b.
The gear position sensor consists of a magnet assembled inside the magnet holder
and a Hall IC mounted on a PCB which is located inside housing. The interference
between magnet and pocket in magnet holder is 0.1 mm diametrically. However,
due to linear thermal expansion of plastic material of magnet holder under high
temperature operating conditions surrounded by oil medium, the magnet holder
tends to expand and the magnet press fitted in magnet holder gets loose. As a
consequence, the magnet rotates in the magnet holder about its axis during
dynamic condition e. g. high mechanical stress with jerks and high vibrational
acceleration levels up to 60g due to clearance occurred in between magnet holder
guiding pocket and the magnet. This movement and rotation of magnet in magnet
holder causes the gear position sensor to fail its primary function to show output
signal specification characteristic and adversely affects the performance of the
vehicle.
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In the light of the foregoing discussion, there is need to develop a locking
mechanism for locking the magnet in the magnet holder to overcome the
limitations stated above.
SUMMARY OF THE INVENTION
According to an aspect of the invention magnetic holding unit for gear position
sensor is provided. the said unit comprises a circular magnet (507), comprising a
groove (503) formed along its diameter; and at least one flat surface (508) being
formed at least one end of the groove (503) up to a predetermined length; and a
magnet holder (501) for holding the magnet (507), comprising a base; an O-ring
rigidly fixed at the center of top surface of the base (509), said O-ring (510)
having an inner wall and an outer wall; at least two arc members (511) attached to
the inner wall of the O-ring (510) and placed over the base (509) facing opposite
to each other; at least one rib (502) positioned centrally along the width of at least
one arc member (511) to engage with the groove (503) of the magnet to restrict its
rotational movement; a plurality of guiding surfaces (506) being formed as a step
along the inner wall of the O-ring at predetermine locations, wherein the upper
portion of each of the guiding surface (506) having a protrusion (504) to restrict
axial movement of the magnet; and at least one slot formed on the inner wall of
the O-ring that receives the magnet (507) in the magnet holder (501).
According to another aspect of the invention a magnet holding unit is provided,
wherein the groove of the magnet (507) have a semicircular or tapered or square
or oval or triangular cross-section or any combination thereof.
According to yet another aspect of the invention a magnet holding unit is
provided, wherein the rib (502) of the magnet holder (501) is in conformity with
shape and size of the groove of the magnet.
According to still another aspect of the invention a magnet holding unit is
provided, wherein the groove of the magnet (507), the rib (502) and the guiding
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surfaces (506) of the magnet holder (501) provide a locking for magnet in the
magnet holder..
According to another aspect of the invention a magnet holding unit is provided,
wherein the locking of the magnet (507) in the magnet holder prevents movement
of the magnet in any direction.
According to yet another aspect of the invention a magnet holding unit is
provided, wherein the magnet holder is filled with an adhesive and thereby
encompassing the magnet when assembled together in the magnet holder.
According to still another aspect of the invention a gear position sensor is
provided, wherein the slot of the O-ring receives the magnet (507) in the magnet
holder (501) such that the flat surface of the magnet (507) faces the slot.
BREIF DESCRIPTION OF DRAWINGS
Further aspects and advantages of the present invention will be readily understood
from the following detailed description with reference to the accompanying
drawings. Reference numerals have been used to refer to identical or similar
functionally similar elements. The figures together with a detailed description
below, are incorporated in and form part of the specification, and serve to further
illustrate the embodiments and explain various principles and advantages, in
accordance with the present invention wherein:
Figure 1a and 1b illustrates existing gear position sensor assembly.
Figure 2 depicts cross-sectional view of the gear position sensor assembly
according to an embodiment of the present invention.
Figure 3 illustrates gear position sensor output characteristics while operating
under vibration and high temperature operating conditions.
Figure 4 illustrates an exploded view of the gear position sensor assembly
according to an embodiment of the present disclosure.
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Figure 5a, 5b and 6 illustrates different parts of a magnet holding unit of the gear
position sensor assembly shown in Figure 4.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, there is shown an illustrative embodiment of the
invention a magnet holding unit for gear position sensor assembly. It should be
understood that the invention is susceptible to various modifications and
alternative forms; specific embodiment thereof has been shown by way of
example in the drawings and will be described in detail below. It will be
appreciated as the description proceeds that the invention may be realized in
different embodiments.
Before describing in detail embodiments it may be observed that the novelty and
inventive step that are in accordance with the present invention reside in the
construction of the magnet and magnet holder, accordingly, the drawings are
showing only those specific details that are pertinent to understanding the
embodiments of the present invention so as not to obscure the disclosure with
details that will be readily apparent to those of ordinary skill in the art having
benefit of the description herein.
The terms “comprises”, “comprising”, or any other variations thereof, are
intended to cover a non-exclusive inclusion, such that a setup, device that
comprises a list of components does not include only those components but may
include other components not expressly listed or inherent to such setup or device.
In other words, one or more elements in a system or apparatus proceeded by
“comprises… a” does not, without more constraints, preclude the existence of
other elements or additional elements in the system or apparatus.
Accordingly, it is an aim of the present disclosure to provide magnet holding unit
to hold the magnet in magnet holder under dynamic conditions and wide operating
temperature range in oil medium and restrict its rotary and axial movements.
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The magnet holding unit provided in the present disclosure avoids rotation of the
magnet about its axis and X-Y-Z axial movement of the magnet in the magnet
holder, against the dynamic and high operating temperature conditions in oil
medium. This is accomplished by the provision of tapered profile anti-rotation rib
and snap locks with guide profile in the magnet holder. The tapered slot provided
in magnet is fitted on tapered profile vertical rib of magnet holder restricting the
rotation of magnet under dynamic and high operating temperature conditions. Flat
surface on magnet and slots on magnet holder formed 180° apart also ensures
POKA YOKE for reverse assembly of magnet in magnet holder and the rib
restrict downward movement of magnet.
Figure 2 depicts the cross-sectional view of the gear position sensor assembly
according to an embodiment of the present disclosure. The gear position sensor
assembly consists of a Hall IC mounted on PCB and a magnet encapsulated in the
magnet holder, a lock plate, D-shaft and a self-tapping screw. The magnet holder
along with magnet is first located in the housing. The lock plate is then located on
the magnet holder and rotated in counter clockwise direction until the snap locks
of lock plate gets locked firmly in the housing slots, later the D-shaft is engaged
with the magnet holder by a screw.
As provided in above paragraphs, under vibration and high temperature operating
conditions in synthetic oil medium, the magnet rotates about its axis in magnet
holder causing an undesirable drift in sensor output characteristics as illustrated in
Figure 3.
Figure 4 illustrates an exploded view of the gear position sensor assembly
according to an embodiment of the present disclosure. The gear position sensor
assembly primarily consists of PCB (407) and magnet holding unit. The PCB
(407) consists of Hall IC and other electronic components. During assembly, the
PCB (407) is positioned in housing by mounting in locating pips and arrest
vertical movement by heat caulking and encapsulant filling. The magnet holding
unit consists of a magnet (405) and a magnet holder (404). At first, the magnet
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holding unit is located in the housing and then the lock ring (403) is located on the
magnet holder and rotated in Counter Clockwise direction until the snap locks of
the lock ring (403) gets locked firmly in the housing slots. Later a D-shaft rotor
(402) is engaged with the magnet holder (404) by a self-tapping screw (401). As
the D-shaft rotor (402) is coupled with gear box drum of Gearbox of the vehicle
for example, a motorcycle, it tends to rotate in clockwise and counter clockwise
direction during the operating condition of motorcycle. The magnet holding unit
also rotates in both directions along with the D-shaft, to avoid the magnet holder
coming out of housing during rotation a lock ring is fixed on the magnet holder.
As the in the magnet holding unit, the magnet is locked in the magnet holder
firmly in its position by a primary and a secondary locking of magnet holding unit
(discussed later), a constant air gap is maintained between the magnet and Hall IC.
Thus, the magnet does not rotate about its axis in the magnet holder under external
vibrations and high operating temperature condition in synthetic oil medium and
ensures desired output characteristics of hall IC.
Fig. 5a, 5b and 6 illustrates the different parts of magnet holding unit of the gear
position sensor shown in Figure 4. The magnet holding unit comprises a circular
magnet (507) and a magnet holder (501). The magnet comprises a groove (503)
formed along its diameter and at least one flat surface (508) being formed at least
one end of the groove (503) up to a predetermined length. This predetermined
length may vary from 3 mm to 4 mm but not limited thereto. The magnet holder
(501) comprises a base (509), an O-ring (510) which is rigidly fixed at the center
of top surface of the base, said O-ring has an inner wall and an outer wall, arc
members (511) which are attached to the inner wall of the O-ring (510) and placed
over the base facing opposite to each other. The magnet holder also comprises ribs
(502) positioned centrally along the width of the arc members to engage with the
groove of the magnet (507) to restrict its rotational movement, a plurality of
guiding surfaces (506) being formed as a step along the inner wall of the O-ring at
predetermine locations. The upper portion of each of the guiding surface (506)
having a protrusion (504) or snap locks to restrict axial movement of the magnet
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(507). At least one slot (512) is formed on the inner wall of the O-ring that
receives the magnet (507) in the magnet holder (501).
The groove (503) of the magnet may have either a semicircular or tapered or
square or oval or triangular cross-section or any combination thereof. The similar
shape is provided in the rib (502) of the magnet holder (501) such that when
magnet and magnet holder are assembled together to provide a positive locking of
the magnet.
The groove (503) of the magnet (507), the rib (502) and the guiding surfaces (506)
of the magnet holder (501) provide a primary locking for magnet in the magnet
holder to restrict its rotation about its axis in dynamic conditions. The guide
profile (506) is provided to restrict magnet axial movement in X and Y directions.
The snap locks (504) or protrusions of the guiding surfaces provided in magnet
holder at four places (1, 2, 3, 4) in diagonal direction restrict up-down movement
of the magnet in Z-direction.
Fig. 6 illustrates the secondary locking of the magnet holding unit. Adhesive flow
passages (601) are provided in the magnet holder around magnet holding area and
below magnet resting surface. This construction ensures adhesive application all
over the magnet which firmly holds the magnet in dynamic conditions and serves
as secondary locking of the magnet. Adhesive is already filled in pocket provided
below magnet resting surface and the passage is designed in such a way that at the
time when magnet is being press-fitted in downward direction through snaps, it
creates pressure on adhesive which flows automatically in upward direction and
fill area around the magnet to fix the magnet in the magnet holder.
A flat surface (508) is provided in the magnet at 180º both sides of the groove and
the same profile or slots are maintained in magnet holder. This profile ensures
magnet reverse fitment POKA-YOKE. Thus, the primary and secondary locking
hold the magnet in all degrees of freedom under dynamic and in wide temperature
operating conditions. Also a proper adhesive, for example silicon adhesive
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nullifies effect of linear thermal expansion and contraction of magnet holder
plastic material and ensures bonding of the magnet to the magnet holder surfaces
in high vibration profile and high temperature synthetic oil operating conditions.
Equivalents
With respect to the use of substantially any plural and/or singular terms herein,
those having skill in the art can translate from the plural to the singular and/or
from the singular to the plural as is appropriate to the context and/or application.
The various singular/plural permutations may be expressly set forth herein for
sake of clarity.
It will be understood by those within the art that, in general, terms used herein,
and especially in the appended claims (e.g., bodies of the appended claims) are
generally intended as "open" terms (e.g., the term "including" should be
interpreted as "including but not limited to," the term "having" should be
interpreted as "having at least," the term "includes" should be interpreted as
"includes but is not limited to," etc.). It will be further understood by those within
the art that if a specific number of an introduced claim recitation is intended, such
an intent will be explicitly recited in the claim, and in the absence of such
recitation no such intent is present. For example, as an aid to understanding, the
following appended claims may contain usage of the introductory phrases "at least
one" and "one or more" to introduce claim recitations. However, the use of such
phrases should not be construed to imply that the introduction of a claim recitation
by the indefinite articles "a" or "an" limits any particular claim containing such
introduced claim recitation to inventions containing only one such recitation, even
when the same claim includes the introductory phrases "one or more" or "at least
one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should
typically be interpreted to mean "at least one" or "one or more"); the same holds
true for the use of definite articles used to introduce claim recitations. In addition,
even if a specific number of an introduced claim recitation is explicitly recited,
those skilled in the art will recognize that such recitation should typically be
interpreted to mean at least the recited number (e.g., the bare recitation of "two
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recitations," without other modifiers, typically means at least two recitations, or
two or more recitations). Furthermore, in those instances where a convention
analogous to "at least one of A, B, and C, etc." is used, in general such a
construction is intended in the sense one having skill in the art would understand
the convention (e.g., "a system having at least one of A, B, and C" would include
but not be limited to systems that have A alone, B alone, C alone, A and B
together, A and C together, B and C together, and/or A, B, and C together, etc.). In
those instances where a convention analogous to "at least one of A, B, or C, etc."
is used, in general such a construction is intended in the sense one having skill in
the art would understand the convention (e.g., "a system having at least one of A,
B, or C" would include but not be limited to systems that have A alone, B alone, C
alone, A and B together, A and C together, B and C together, and/or A, B, and C
together, etc.). It will be further understood by those within the art that virtually
any disjunctive word and/or phrase presenting two or more alternative terms,
whether in the description, claims, or drawings, should be understood to
contemplate the possibilities of including one of the terms, either of the terms, or
both terms. For example, the phrase "A or B" will be understood to include the
possibilities of "A" or "B" or "A and B."
While the invention has been described with reference to a preferred embodiment,
it is apparent that variations and modifications will occur without departing the
spirit and scope of the invention. It is therefore contemplated that the present
disclosure covers any and all modifications, variations or equivalents that fall
within the scope of the basic underlying principles disclosed above and claimed
therein.
REFERRAL NUMERALS
REFERRAL NUMERALS DESCRIPTION
407 PCB
402 D-shaft rotor
403 Lock ring
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401 Self-tapping screw
507, 405 Circular magnet
503 Groove
508 Flat surface
501, 404 Magnet holder
509 Base
510 O-ring
511 Arc members
502 Rib
506 Guiding surface
504 Protrusion or snap locks
512 Slot
601 Flow passages

We claim:
1. A magnet holding unit for gear position sensor assembly, said unit
comprising:
a circular magnet (507), comprising:
a groove (503) formed along its diameter; and
at least one flat surface (508) being formed at least one end of
the groove (503) up to a predetermined length; and
a magnet holder (501) for holding the magnet (507), comprising:
a base (509);
an O-ring (510) rigidly fixed at the center of top surface of the
base, said O-ring having an inner wall and an outer wall;
at least two arc members (511) attached to the inner wall of the Oring
(510) and placed over the base facing opposite to each other;
at least one rib (502) positioned centrally along the width of at least
one arc member to engage with the groove of the magnet (507) to restrict
its rotational movement;
a plurality of guiding surfaces (506) being formed as a step along
the inner wall of the O-ring at predetermine locations, wherein the upper
portion of each of the guiding surface (506) having a protrusion (504) to
restrict axial movement of the magnet (507); and
at least one slot (512) formed on the inner wall of the O-ring that
receives the magnet (507) in the magnet holder (501).
2. The magnet holding unit of claim 1, wherein the groove of the magnet
(507) have a semicircular or tapered or square or oval or triangular crosssection
or any combination thereof.
3. The magnet holding unit of claim 1, wherein the rib (502) of the magnet
holder (501) is in conformity with shape and size of the groove of the
magnet (507).
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4. The magnet holding unit of claim 1, wherein the groove (503) of the
magnet (507), the rib (502) and the guiding surfaces (506) of the magnet
holder (501) provide a locking for magnet in the magnet holder.
5. The magnet holding unit of claim 5, wherein the locking of the magnet
(507) in the magnet holder (501) prevents movement of the magnet in any
direction.
6. The magnet holding unit of claim 1, wherein the magnet holder (501) is
filled with an adhesive and thereby encompassing the magnet when
assembled together in the magnet holder.
7. The magnet holding unit of claim 1, wherein the slot of the O-ring receives
the magnet (507) in the magnet holder (501) such that the flat surface of
the magnet (507) faces the slot.