FIELD OF THE INVENTION
The present invention relates to an acceleration position sensor used in two wheelers
for controlling speed. More particularly, the present invention to magnetic circuit
which provides the same feel to the driver as of mechanical throttle grip and also
maintains constant air gap between magnet and hall sensor unit in dynamic conditions.
BACKGROUND OF THE INVENTION
Presently in automobiles, generally two wheelers, an accelerator grip is rotationally
mounted on a handlebar and the accelerator is rotated with respect to the handlebar to
open and close a throttle valve of the internal combustion engine. On many two
wheelers, an electric relative position detection device is used, in which the rotational
movement of the accelerator is detected by a potentiometer and the throttle valve is
opened and closed by an actuator based upon the output voltage from the
potentiometer.
To reduce the likelihood of a malfunction in the potentiometer resulting in undesired
throttle positional control, a separate mechanical switch also is provided that is capable
of detecting a completely-closed position of the accelerator so as to close the throttle
valve if the accelerator is positioned in the closed position and the throttle valve is not
fully closed.
An improved system has also been developed that features a magnetic relative position
detection device in which a magnet is disposed in an accelerator and the rotational
position of the accelerator is detected via changes in the magnetic flux density.
However, in the existing system the problem of flux leakage still exists which results
into improper detection of magnetic flux and position of throttle.
Referring to Figure 1, conventional technology non-contact twist grip consists of
magnet mounted on Rotor and Hall IC mounted in housing. As rotor moves in radial
direction due to vibrations, it causes magnet to also move in radial direction with
respect to Hall IC. Moment of magnet in radial direction results in change of air gap,
flux density and hence sensor output which is not desired. This change in sensor
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output results in sudden acceleration of vehicle speed or increase in engine idle rpm.
Also, feel to the rider is not same as that of conventional (cable type) accelerator
position sensor.
The disadvantages of the existing technology are:
1. The Rider does not have same feel as of conventional throttle.
2. Since there is no friction mechanism rider will have great difficulty in
maintaining the throttle grip at constant speed while driving.
3. External vibrations will cause rotor and magnet moment in radial direction
which results in change in sensor output characteristics which is not intended.
Therefore, there exists a need to develop a magnetic circuit provides the same feel to
the driver as of mechanical throttle grip and also maintains constant air gap between
magnet and hall IC in dynamic conditions
SUMMARY OF THE INVENTION
An accelerator position sensor (APS) system for detecting angular rotation of a
throttle pipe mounted on handlebar of a vehicle, said APS system comprising a rotor
coupled with the throttle pipe so as to rotate about a rotational axis of the throttle pipe,
a magnet being mounted on the rotor is angularly movable about the rotational axis of
the throttle pipe, a sensor case being mounted on the handlebar; wherein the sensor
case comprises: a hall sensor unit accommodated in the sensor case and configured to
provide output based on change in magnet flux due to angular movement of the
magnet, a torsion spring, a lever partly disposed over the rotor and biased by at least a
resilient mean towards the outer periphery of the rotor and a cover screwed to the
sensor case to hold the components in the system.
BRIEF DESCRIPTION OF FIGURES
Further aspects and advantages of the present invention will be readily understood
from the following detailed description with reference to the accompanying
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figures. 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 1 illustrates an existing of non-contact existing grip showing a stator, rotor and
a magnet.
Figure 2a illustrates an APS magnetic circuit according to an embodiment of the
present invention.
Figure 2b illustrates sectional view of APS magnetic circuit shown in Figure 2a.
Figure 3 illustrates an APS magnetic circuit according to an embodiment of the present
invention.
Figure 4a illustrates the dimensions of the lever according to an embodiment of the
present invention.
Figure 4b illustrates the dimensions of rotor according to an embodiment of the
present invention.
Figure 5 illustrates the exploded view of accelerator position sensor assembly.
Figure 6a illustrates an APS magnetic circuit according to an alternative embodiment
of the present invention.
Figure 6b illustrates sectional view of APS magnetic circuit shown in Figure 5a.
Figure 6c illustrates the dimensions of the lever according to an alternative
embodiment of the present invention.
Figure 7a illustrates an APS magnetic circuit according to an alternative embodiment
of the present invention.
Figure 7b illustrates the front view of plunger according to an alternative embodiment
of the present invention.
Figure 7c illustrates the top view of plunger according to an alternative embodiment of
the present invention.
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Figure 8 illustrates a hysteresis graphing showing frictional torque characteristics of
throttle grip.
Skilled artisans will appreciate that elements in the drawings are illustrated for
simplicity and have not necessarily been drawn to scale. For example, the
dimensions of some of the elements in the drawings may be exaggerated relative to
other elements to help to improve understanding of embodiments of the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
While the invention is susceptible to various modifications and alternative forms,
specific embodiment thereof has been shown by way of example in the figures and
will be described in detail below. It should be understood, however that it is not
intended to limit the invention to the particular forms disclosed, but on the contrary,
the invention is to cover all modifications, equivalents, and alternative falling with in
the spirit and the scope of the invention as defined by the appended claims.
Before describing in detail the various embodiments of the present invention it may
be observed that the novelty and inventive step that are in accordance with the present
invention resides in the construction of APS magnetic circuit and lever in magnetic
circuit. It is to be noted that a person skilled in the art can be motivated from the
present invention and modify the various construction of APS magnetic circuit and
lever in magnetic circuit. However, such modification should be construed within the
scope and spirit of the invention.
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”, “including” or any other variations thereof, are
intended to cover a non-exclusive inclusion, such that an assembly, mechanism,
setup, that comprises a list of components does not include only those components but
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may include other components not expressly listed or inherent to such assembly,
mechanism or setup. In other words, one or more elements in an accelerator position
sensor (APS) system for detecting angular rotation of a throttle pipe mounted on
handlebar of a vehicle proceeded by “comprises” does not, without more constraints,
preclude the existence of other elements or additional elements in the assembly or
mechanism. The following paragraphs explain present invention and the same may be
deduced accordingly.
Accordingly, it is an aim of the present invention to provide APS which overcomes at
least one of the problems associated with the prior existing APS.
Another aim of the present invention is to provide an accelerator position sensor
(APS) system for detecting angular rotation of a throttle pipe mounted on handlebar
of a vehicle with lever. Yet another object of the present invention is to provide a
lever to the existing magnetic circuit which overcomes at least one of the problems of
existing mechanism of throttle of throttle or accelerator position sensor.
Accordingly, the present invention provides an accelerator position sensor (APS)
system for detecting angular rotation of a throttle pipe mounted on handlebar of a
vehicle, said APS system comprising;
a rotor coupled with the throttle pipe so as to rotate about a rotational axis of the
throttle pipe;
a magnet being mounted on the rotor is angularly movable about the rotational axis of
the throttle pipe;
a torsion spring;
a sensor case being mounted on the handlebar; wherein the sensor case comprises:
a hall sensor unit accommodated in the sensor case and configured to provide output
based on change in magnet flux due to angular movement of the magnet;
a lever partly disposed over the rotor and biased by at least a resilient mean towards
the outer periphery of the rotor;
a cover screwed to the sensor case to hold the components in the system.
In an embodiment of the present invention, the said lever has a first end and a second
end.
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In another embodiment of the present invention, the first end of the lever is pivoted in
the sensor case along with the rotor.
In yet another embodiment of the present invention, the second end of the lever is
attached to a compression spring.
In a further embodiment of the present invention, the lever is located over the rotor so
as to be circumferentially in contact with the outer periphery of the rotor.
In a further more embodiment of the present invention, the torsion spring is mounted
on the grip side of the handle bar by means of a spring holder.
In still another embodiment of the present invention, the lever is made of spring steel.
In still another embodiment of the present invention, the lever comprises a plunger
loaded by means of a spring.
The following paragraphs describe the present invention with reference to Figures 2-
8.
As shown in Figure 2a and 2b, the accelerator position sensor (APS) magnetic system
(1) comprises of a rotor (2), a magnet (3), a sensor case (4), a hall sensor unit (8), a
resilient means (6), a lever (5) and a cover (9). The said system (1) is mounted on the
handle bar (not shown in Figure) of a vehicle for detecting angular rotation of a
throttle pipe (7). The hall sensor unit (8) is used to convert mechanical rotation of the
throttle grip into analogue voltage output through mapping the magnet (3) position.
The speed of the vehicle is varied according to the amount through which the throttle
grip is rotated on the handle bar.
In the present system, the rotor (2) is coupled with the throttle pipe (7) so as to rotate
about a rotational axis (X). The magnet (3) is mounted on the rotor (2) and is
angularly movable about the rotational axis (X). The sensor case (4) is mounted on
the handle bar.
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As shown in Figures 3, 4a and 4b, the sensor case (4) comprises rotor (2), lever (5)
and a compression spring (6). The lever (5) is located on top of the rotor. The lever
(5) has a first end (5a) and a second end (5b). The lever (5) has a length (L1), a height
(H1), an outer radius (R1’) and an inner radius (R1). The rotor (2) has an outer radius
(R2) and an inner radius (R2’). The inner radius (R1) of the lever (5) makes contact
with the outer radius (R2) of rotor (2). The inner radius (R1) of the lever (5) is
generally equal to the outer radius (R2) of the rotor (2).
The first end (5a) of the lever (5) is pivoted in the sensor case (4) and the second end
(5b) of the lever (5) is attached to the compression spring (6). The compression spring
(6) is located in the sensor case (4) to provide necessary spring force (SF) which
creates a reaction force (Rn) in radial downward direction at the center of the rotor (2)
as shown in Figure 3. The reaction force (Rn) generates a frictional torque (FT) as the
rotor (2) rotates and provides required feel to the rider while driving. The reaction
force (Rn) also pushes rotor (2) in downward direction and maintains a constant air
gap between the magnet (3) and the hall sensor unit (8) in radial axis.
The Frictional torque (FT) generated by the present mechanism is calculated as below:
Table 1
Input parameters Description
Length of lever pivot center to point of
load application
L
Length of lever pivot center to rotor
center
X
Rotor Outer Radius R2
Spring rate Sr
Compressed length of spring Cl
Spring Force SF
Reaction Force on rotor Rn
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Frictional Torque on rotor FT
Co-efficient of Friction between rotor
and lever
μ
Torque of torsional spring at 0 ͦ Ts1
Torque of torsional spring at N ͦ
(Complete rotation)
Ts2
 Lever spring force calculations(SF):-
SF=spring rate X compressed length
= Sr x Cl
 Normal reaction force on rotor(Rn):-
Rn=(L/X) x SF
 Frictional Torque on rotor(FT):-
FT=Rn x μ x R2
 Nominal opening Torque at 0°:-
C1=Ts1 + FT
 Nominal opening Torque at complete rotation(N°):-
C2=Ts2 + FT
 Nominal closing Torque at 0°:-
A1=Ts1 - FT
 Nominal closing Torque at complete rotation(N°):-
A2=Ts2 – FT
On the grip side of the throttle pipe (not shown in figure), a torsion spring (10) is
located along with a spring holder (11). The torsion spring (10) has a first end (10a)
and a second end (10b). The first end (10a) of the torsion spring (10) is located in the
spring holder (11) and the second end (10b) is connected to the sensor case (4). The
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spring holder (11) is coupled to the rotor (2) by spline contact and is locked by snap
locks on the rotor (2). The torsion spring (10) brings the rotor (2) back to its initial
position after release of the throttle grip. The throttle grip consists of a plurality of
positive guide walls which are engaged in a plurality of slots in the rotor (2). A pcb
sub-assembly (12) along with the hall sensor unit (8) is placed in the sensor case (4)
and a lid plate is screwed to hold and cover the pcb sub-assembly (12).
Figure 5 shows an exploded view of the Accelerator Position Sensor (APS) system (1)
with various child parts such as lower case, upper case, sensor case (4), lever (5),
compression spring (6), rotor (2), magnet (3), cover (9), throttle pipe (7), etc. The
cover (9) is screwed to the sensor case (4) to hold the components in the system (1).
The material of each child part is given below for reference however, any alternate
material can be used which can meet the required function and withstand the
environmental conditions for the product.
Table 2
Child Part Material
Lower Case PA6 30% GF
Upper case PA6 30% GF
Sensor case PBT 30% GF
Lever POM
Compression spring Spring steel
Rotor PA66 30% GF
Magnet Rare earth(NdFeb)
Cover PBT 30% GF
PCB with hall IC ----------
Lid plate Aluminium
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M2 self tapping screw Mild steel
Torsion spring Spring steel
Spring holder PA6 30% GF
Throttle pipe PBT 30% GF
M2.5 self-tapping screw Mild steel
M3 self-tapping screw Mild steel
M5 screw Mild steel
Figures 6a-6c show an alternative embodiment of the present invention wherein the
height and length of the lever (50) are considerably reduced to reduce the overall size
Accelerator Position Sensor (APS) system (10).
As shown in Figure 6c, the lever (50) has a first end (50a) and a second end (50b).
The lever (50) has a length (L2) and a height (H2). Referring to Figure 6a and 6b, the
lever (50) is pivoted in the sensor case (40) by means of an arc (A). The compression
spring (60) in the present embodiment has a first end (60a) and a second end (60b).
The first end (60a) of the compression spring (60) is located in the sensor case (40)
and the second end (60b) rests on the lever (50). The compression spring (60) is
aligned with the rotor (20) along Y axis. The material of the lever is commonly spring
steel.
Figures 7a-7c shows another alternative embodiment of the present invention wherein
the lever is replaced by a plunger (P). The plunger (P) is a cylindrical shaped structure
having an open end (P1). The said open end (P1) is adapted to accommodate a
resilient means such as a compression spring (600) in the hollow interior of the
plunger (P). The plunger has a length (L3). The plunger surface (PS) has an inner
surface (PS1) and an outer surface (PS2) wherein the outer surface (PS2) of the
plunger (P) is guided in the sensor case (400). The compression spring (600) is
aligned with the rotor (200) along Y axis.
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As shown in Figure 7a, the axis of the plunger (P) is aligned with Y-axis of the rotor
(200). The plunger (P) makes line contact on the rotor surface and provides a
downward radial force to maintain constant air gap between the hall sensor unit (800)
and the magnet (300). The material of the plunger is commonly polyoxymethylene.
Figure 8 illustrates a hysteresis graph representing frictional torque characteristics of
throttle grip which has friction mechanism inbuilt. Ideally if there is no friction
mechanism torque characteristics will follow the spring line.
Advantages of the present invention:
1) The Rider will have the same feel as that of conventional throttle.
2) Due to use of the present mechanism, driver can comfortably maintain throttle
grip position to achieve constant speed as the friction on the rotor will keep the
throttle grip stable during its operation.
3) The air gap between the Hall sensor and the magnet will remain constant under
external vibrations in radial axis. Hence, the sensor output characteristics will
remain constant as desired.

We Claim:
1. An accelerator position sensor (APS) system (1) for detecting angular rotation
of a throttle pipe (7) mounted on handlebar of a vehicle, said APS system (1)
comprising;
a rotor (2) coupled with the throttle pipe (7) so as to rotate about a rotational
axis of the throttle pipe (7);
a magnet (3) being mounted on the rotor (2) is angularly movable about the
rotational axis of the throttle pipe (7);
a torsion spring (10);
a sensor case (4) being mounted on the handlebar; wherein the sensor case (4)
comprises:
a hall sensor unit (8) accommodated in the sensor case (4) and configured to
provide output based on change in magnet flux due to angular movement of
the magnet (3);
a lever (5) partly disposed over the rotor (2) and biased by at least a resilient
mean (6) towards the outer periphery of the rotor (2);
a cover (9) screwed to the sensor case (4) to hold the components in the
system (1).
2. An accelerator position sensor (APS) system (1) as claimed in claim 1,
wherein the said lever (5) has a first end (5a) and a second end (5b).
3. An accelerator position sensor (APS) system (1) as claimed in claim 1,
wherein the first end (5a) of the lever (5) is pivoted in the sensor case (4)
along with the rotor (2).
4. An accelerator position sensor (APS) system (1) as claimed in claim 1,
wherein the second end (5b) of the lever (5) is attached to a compression
spring (6).
5. An accelerator position sensor (APS) system (1) as claimed in claim 1,
wherein the lever (5) is located over the rotor (2) so as to be circumferentially
in contact with the outer periphery of the rotor (2).
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6. An accelerator position sensor (APS) system (1) as claimed in claim 1,
wherein the torsion spring (10) is on mounted the grip side of the handle bar
by means of a spring holder (11).
7. An accelerator position sensor (APS) system (1) as claimed in claim 1,
wherein the lever (5) is made of spring steel.
8. An accelerator position sensor (APS) system (100) as claimed in claim 1,
wherein the lever comprises a plunger (500) loaded by means of a spring
(600).