FIELD OF THE INVENTION:

The invention relates to a magnetic direction sensing system and particularly those for use in a motorcycle.

DESCRIPTION OF THE PRIOR ART:

Magnetic direction sensing system has been a standard accessory in ships and airplanes since the invention of the magnetic compass. There has also been magnetic direction sensing systems made for on road vehicles as shown in the block diagram (Fig1). Such systems consist of a magnetic field sensor that senses the earth's magnetic field and a control system that corrects the sensor output and calibrates the sensor to account for the change in vehicle's magnetism.

The earth can be considered as a magnetic dipole with its magnetic north(MN) and south(MS) poles located near the geographic poles (GN and GS) as shown in Fig 2. The axis of the earth's magnetic dipole and the axis of rotation are separated by an angle of about 11.5 degrees called declination (A in Fig 3). In a magnetic direction sensing system as shown in Fig 1, the magnetic field sensor output will indicate the angle of separation between heading direction of the vehicle and the earth's magnetic north. This has to be corrected by a declination factor to find the heading direction with respect to geographic north (true north). The angle between the earth's magnetic field vector (He) and the horizontal plane is called inclination or dip (5 in Fig 3). Inclination has to be considered if the compass tilts and corresponding correction has to be done.

Flux gate type sensors, magneto inductive sensors and magneto resistive sensors have been used as magnetic field sensors to sense the earth's magnetic field and provide signals representative thereof to the control circuit.
The signal conditioning unit (SCU) in Fig 1 is required to amplify the signals provided by the sensors, correct any offset present and provide compensation for sensitivity variation. The direction determination unit is used to obtain the azimuth information (angle between the magnetic north and direction of heading of vehicle, a in Fig 3) from the signal conditioned sensor output.

The signal conditioning output (Vx and Vy) for a full clockwise rotation of the magnetic field sensor are shown in Fig 4. The direction determination unit compares the Signal
Conditioning Unit signals with the thresholds Vt+ and Vt- to obtain logic signals for North (N), South (S), East (E) and West (W).

For a motorcycle (Fig 5) there is a requirement for positioning of the magnetic direction sensor such that the vehicle magnetism does not affect the accuracy of the system and the magnetic field created by current carrying conductors in the vehicle do not interfere with the sensor.

The engine vibrations and vehicle vibrations due to different road conditions should not affect the operation of the magnetic direction sensing system. The direction is to be displayed on the instrument cluster and the entire system should occupy less space and should be easy to service.

The objective of the invention disclosed is to provide a low cost and easily serviceable magnetic direction sensing system for a motorcycle that is not affected by the vehicle magnetism and vehicle vibration and to provide an indication unit for visually indicating the direction of heading on the instrument cluster.

SUMMARY OF THE INVENTION:

The present invention is a magnetic direction sensing and indication system for a motorcycle.

It comprises a magnetic field sensor connected with a control circuit and located inside the headlamp housing of the motorcycle. The magnetic field sensor and control circuit are housed within a box and connected with the headlamp rear housing by means of a single bracket.

The circuit module is connected to a battery in the motorcycle through the main wiring harness.

The circuit module is also connected to an indication unit located on the instrument cluster to provide a visual indication of the heading direction to the rider.

The magnetic field sensor is placed away from the high current carrying conductors in the motorcycle to avoid errors in sensing earth's magnetic field. The circuit module is located inside the headlamp housing of the motorcycle such that it can easily be replaced. The box with the magnetic field sensor and control circuit is connected with the headlamp rear housing in front of the frame head pipe by means of a bracket.

BRIEF DESCRIPTION OF DRAWINGS:

The invention and objects and features thereof wilt be more readily apparent from the following description and appended claims when taken with the drawing, in which:

Fig 1 is a block diagram of the magnetic direction sensing and indication system.

Fig 2 is a pictorial view of the earth's magnetic field.

Fig 3 is a vector diagram showing the magnetic field sensor output with respect to the earth's magnetic field.

Fig 4 is a plot showing the Signal Conditioning Unit output for a full rotation of the magnetic field sensor.

Fig 5 is a pictorial view of the motorcycle.

Fig 6 is a pictorial view of the circuit module connection with the main wiring harness in the motorcycle.

Fig 7 is a pictorial view of the circuit module location in the motorcycle.

Fig 8 is a pictorial view of the circuit module connection with rear headlamp housing.

Fig 9 is a circuit diagram for Direction Determining Unit and Indication Unit.

Fig 10 is a table showing the Signal Conditioning Unit output at different orientations of magnetic field sensor.

Fig 11 is a pictorial view of the box in which the magnetic field sensor and control circuit are housed.

Fig 12 is a pictorial view of the bracket used to connect the circuit module with the rear headlamp housing.

DESCRIPTION OF PREFERRED EMBODIMENT:

Referring to Figs 6 to 8 inclusive, a circuit module (20) comprising the magnetic field sensor and control circuit housed in a box is connected with the headlamp rear housing (30) of the motorcycle by means of a bracket (40). The circuit module (20) is electrically connected with the main wiring harness (50) by means of a coupler (60). The circuit module (20) is located in front of the frame head pipe (70) so that the circuit module can be replaced easily. The circuit module (20) is electrically connected with an indication unit mounted on the instrument cluster (80) of the motorcycle.

Referring to Fig 9, a direction determining unit comprising a logic circuit made of comparators and logic gates based on table in Fig 10 is used to connect Signal Conditioning Unit output (Vx and Vy) with indication unit. The indication unit is made up of Light Emitting Diodes (LEDs). Alternatively, Liquid Crystal Display (LCD) or alpha numeric display or an arrangement of bulbs can be used.

Referring to Fig 11 and Fig 12, the outer surface of the box of circuit module (20) has a cylindrical projection (90) for mounting the circuit module (20) through hole (100) in, bracket (40).

The Signal Conditioning Unit and Direction Determination Unit together constitute the control circuit of the magnetic direction sensing system. The control circuit may comprise of one or more analog and/or digital electrical or electronic components and may include a microprocessor, microcontroller, application specific integrated circuit, programmable logic, and/or other analog and/or digital circuit elements configured to perform various input, output, control and analysis functions.

The indication unit can be located at different locations on the motorcycle such that it is
visible to the rider, instead of instrument cluster, the indication unit can also be located
on the handle bar assembly or on the fuel tank of the motorcycle.

Instead of a battery, the circuit module can also be connected with capacitors in which energy is stored in an electrostatic field,
Various modifications and adaptations may occur to those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

We claim,

i. A magnetic direction sensing and indication system for a motorcycle comprising:

a) a circuit module connected with a headlamp housing of the said motorcycle,

b) the said circuit module comprising at least one magnetic field sensor and a control circuit, and

c) an indication unit electrically connected with the said control circuit and positioned on the said motorcycle such that the said indication unit is visible to a rider of the said motorcycle.

2. The magnetic direction sensing and indication system according to Claim 1, wherein, the said circuit module is connected with a rear headlamp housing of the said motorcycle.

3. The magnetic direction sensing and indication system according to Claim 2, wherein, the said circuit module is connected with the rear headlamp housing by means of at least one bracket.

4. The magnetic direction sensing and indication system according to Claim 3, wherein, the said circuit module is electrically connected with an energy storing device in the said motorcycle.

5. The magnetic direction sensing and indication system according to Claim 4, wherein, the said energy storing device is a battery.

6. The magnetic direction sensing and indication system according to Claim 1, wherein, the said circuit module comprises a box within which the said magnetic field sensor and control circuit are housed.

7. The magnetic direction sensing and indication system according to Claim 5, wherein, the said box is connected with the rear headlamp housing by means of at least one bracket.

8. The magnetic direction sensing and indication system according to Claim 1,
wherein, the said indication unit is an arrangement of Light Emitting Diodes.

9. The magnetic direction sensing and indication system according to Claim 1,
wherein, the said indication unit is positioned in an instrument cluster of the said motorcycle.

10. A magnetic direction sensing and indication system for a motorcycle substantially as herein described and illustrated.