THROTTLE OPERATED IGNITION CONTROL SYSTEM

FIELD OF THE INVENTION

[0001] The subject matter as described herein, relates generally to a throttle position sensor and more particularly, but not exclusively, to a throttle position sensor for use with automobile engines.

BACKGROUND OF THE INVENTION

[0002] Throttles have been in use for long in automobile engines to accelerate or decelerate the engine when required. They are operated by an operator of a vehicle through a throttle grip which is connected to a carburettor sliding valve through a throttle cable. Such throttles usually include a throttle position sensor which provides a feedback to the electronic control unit of the engine in the form of an electric signal indicating the accurate position of the movable throttle grip. Consequently the engine ignition timing switches between two predetermined ignition timing curves based on the position of the throttle as indicated by the throttle position sensor. The throttle position sensor can be used with both fuel injected and carburetted engines.

[0003] The throttle position sensor generally comprises a plunger connected to the throttle cable, a moving member for movement along with the plunger, a set of fixed members made up of metal tracks and a spring for restoring the position of plunger. When the throttle grip position is below a predetermined rotational angle, the moving member and fixed members are in contact with each other and the electrical circuit formed on their interaction is closed. However, beyond the predetermined rotational angle, there is a discontinuity in the metal tracks and the electrical closed circuit formed by the fixed members and the moving member is opened. The change in the electrical signal of the throttle position sensor is detected by an ignition control unit which in turn changes the ignition timing curve accordingly.

[0004] Indian Patent No. 988/MUM/2002 discloses an ignition controller for an internal combustion engine wherein a micro switch is used to switch between two ignition timing curves and the state of the micro switch is based on the throttle sliding valve of the carburettor. The micro switch can however only be used to support two ignition timing characteristics. Additionally, the engine spark depends on several factors, one of them being the "instant" at which spark is provided. This instant is decided by the ignition system and the instant at which spark should start depends on the engine speed, engine load, throttle position etc. So higher the number of ignition timing curves, better will be the matching of ignition timing with engine operating conditions. Moreover, at the switching instant, because of ignition curve switch over, the rider may experience jerks. However having multiple ignition timing curves would result in smaller switchover time thereby decreasing the overall effect of vehicle jerk.

SUMMARY OF THE INVENTION

[0005] It is therefore an objective of the present subject matter to provide a throttle operated ignition control system with a throttle position sensor having at least two switches, the throttle position sensor operatively connected between the throttle grip and throttle valve of the carburettor and providing a signal to the ignition control unit to switch between a plurality of ignition timing curves. To this end, the present subject matter discloses a throttle position sensor taking its input from a throttle grip and comprising of a moving member having at least two pairs of metal sliding pairs, a fixed member having a plurality of metal tracks, the moving member in sliding contact with the metal tracks of the fixed member; wherein the plurality of metal tracks are segregated into at least two sets defining a plurality of switches and the output of the throttle position sensor is recognised by an ignition control unit to choose among a plurality of predetermined ignition timing curves based on the throttle grip position. The ignition timing curves consist of a first, second and third characteristics.

[0006] The foregoing objectives and summary provide only a brief introduction to the present subject matter. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the subject matter and the claims should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The above and other features, aspects, and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 illustrates an illustrative view of the five metal tracks in the throttle position sensor and the output generated for the ignition control unit.

FIG. 2 shows a second embodiment of the present subject matter disclosing three tracks in the throttle position sensor.

DETAILED DESCRIPTION OF THE INVENTION

[0008] The present subject matter describes a throttle position sensor which is connected to a vehicle, or a part of the vehicle thereof and also operably connected to a throttle grip through a control cable. The control cable is operatively connected between the said sensor and said throttle grip by its ends. The said sensor is electrically connected to a known type of an ignition control unit (which regulates spark generation in the automobile engines) through electrical cables. Further the said sensor is operatively connected to the throttle valve in the carburettor through the throttle cable for its known function.

[0009] The throttle position sensor provided herein comprises of a plurality of movable members and a plurality of fixed members. The movable members are in sliding contact with the fixed members. According to an embodiment of the present invention, the movable members are arranged into two collinear pairs, namely a first pair and a second pair whereas the fixed members are segregated into five tracks. All tracks are connected to the ignition control unit and take their input from the throttle grip.

[00010] The five tracks of fixed members can be segregated into two sets, a first set with two tracks used for determining the ignition curve that is to be followed at a throttle grip position and a second set with three tracks which may be used for determining the ignition curve as well as for speedometer indication. The first pair of the moving member slides over the first set of the fixed member whereas the second pair of the moving member slides over the second set of the fixed member. The moving contact is controlled by a single plunger which is ultimately connected to the throttle cable. A gap is provided in one of the metal tracks of the first set and another gap is provided in one of the metal tracks of the second set for the changeover of the ignition timing curve. The two gaps are non-collinear and thus the second set can be employed to get another switching action wherein the second set is not used for speedometer indication. Thus the two sets together form two switches which can provide three different combinations. The ignition unit thus can detect the state of the two switches of the sensor and can shift between three corresponding predetermined ignition timing curves.

[00011] FIG. 1 shows an illustrative view of the metal tracks in the throttle position sensor and the output generated for the ignition control unit. According to the subject matter, when the throttle grip is operated for opening with an angle within a predetermined point, the first pair and second pair of the moving member getting an electrical input from the corresponding electrical input terminal (or metal tracks) 2A and 2B, give the electrical output to the corresponding terminals 2C and 2E by closing the corresponding electrical circuit. The ignition unit detects this electrical output and functions accordingly. When the throttle grip is still open beyond that said predetermined point, the said ignition unit are functioned by the corresponding other electrical terminals 2D, 2F and 2G. The operation of the terminals (or metal tracks) thus define a first, second and third ignition curve characteristic A, B and C after the input is received from 2 A and 2B. The two sets together forming the two switches can provide three different possible combinations. The ignition unit thus could detect the state of the two switches and can vary between three corresponding timing curves. Higher number of curves depending on metal track configuration ensures better matching of ignition timing to engine operating conditions which would improve engine performance. Multiple curves result in smaller step changes decreasing the overall effect of the vehicle jerk and lower emissions. FIG. 2 shows a second embodiment where only three metal tracks are present. The metal tracks form fixed contact with the gaps. The throttle position sensor can switch between the three tracks. The ignition control unit detects the throttle position switch state and switches between the three ignition timing curves.

[00012] The novelty of the present subject matter lies in the configuration of the throttle position sensor that switches between more than two states and hence the ignition unit can operate at multiple ignition timing characteristics depending upon the number of tracks in the said sensor.

[00013] The present subject matter is thus described. The description is not intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above description. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore the forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.

We claim:

1. A throttle position sensor taking its input from a throttle grip and comprising of a moving member having at least two pairs of metal sliding pairs, a fixed member having a plurality of metal tracks, the moving member in sliding contact with the metal tracks of the fixed member; wherein the plurality of metal tracks are segregated into at least two sets defining a plurality of switches and the output of the throttle position sensor is recognised by an ignition control unit to choose among a plurality of predetermined ignition timing curves based on the throttle grip position.

2. A throttle position sensor as claimed in claim 1 wherein the ignition timing curves consist of a first, a second and a third characteristic.

3. A throttle position sensor as claimed in claim 1, wherein a gap is provided in one of the metal tracks belonging to each set for switchover of the ignition timing curve.