Description:FIELD OF INVENTION:

This invention is related to Automobile field in two wheeler motor cycles.

BACKGROUND OF INVENTION

Gear position sensor of potentiometric type (Resistance based) giving analog voltage output has Resistors (different values) for different gear positions from Neutral to 5 or 6 gear ratios of manual transmission. Potentiometric type is discussed in U.S. Pat. No 20120319708 which is incorporated herein by reference to illustrate the state of the prior art.

There will be contact pins on the sensor connected to one end of the resistors and a constant voltage (+5V) from the display device is applied to the other end of the resistors. A sliding contact pin will be mounted on the gear shift drum for making contact with the sensor pin. As the drum rotates during gear shifting, the sliding pin will make contact with the contact pin on the sensor and the circuit closes during the contact through the transmission ground path (Ground path is from sliding pin –gear drum-star index-arm stopper-spring –chassis-battery negative). As and when contact is made by the sliding gear pin, a voltage drop occurs across the resistor. Based on the resistor value deployed for different gears, the voltage drop varies.

This voltage drop is sensed by the display device and based on the voltage drop (analog value) of different gears; gear position is displayed to the user.

Main drawback in the above indicated system is that the electrical ground path is achieved through the mechanical transmission parts which are highly unstable due to uncontrolled clearances in the components, presence of oil and wear and tear of the interference components which often leads to the build-up of resistance for the ground flow path.

Based on the additional resistance developed in the ground path, the voltage drop gets added and then deviates from the specification .This causes the display device to provide erroneous information/wrong gear indication to the user.

S.No Patent No Brief Description
A 20,120,319,708 Gear position sensor employs a sliding electrical connection between conductors and flexible wiper arms held on opposite surfaces that rotate relative to each other with the movement of a gear selector shaft. The traces may have multiple segments joined by resistors to provide flexible change in resistance value and resistance range for different applications
B US5847344 In gear position sensor Electrical contacts within the sensor are configured to minimize wear and corrosion by eliminating electrical continuity in the switching elements when the gear shift lever is in the Drive position.
c US 6462651 B1 The gear indicator bridges the gear position switch to the motorcycle CPU receiving this ground information through a bridge and a similar number of leads communicate with the gear indicator processor from this bridge. The processor of the gear indicator processes the information received to drive a display to reflect the gear to the operator.
D US8746104 The sensor assembly preferably comprises at least one Hall effect or other type of magnetic field (proximity) sensors in combination with an application specific integrated circuit (ASIC) which is supplied with data from the sensors, decodes the output of the sensors and provides an output identifying a specific engaged gear or neutral for use by vehicle or engine management electronics.

a) This invention is a resistive type Gear position sensor. The invention does not claim anything about the grounding.

b) This invention claims for minimizing wear and tear in the contacts.

c) This invention claims for switch type gear position sensor.

d) This invention claims for noncontact type gear sensor using hall effect sensors.

SUMMARY OF INVENTION

The present invention is directed to a Gear position sensor for a transmission gear selector.

An isolated ground path through transistors is engulfed in the sensor which exhibits immunity to the varying resistance (even up to ~5kO) in the transmission ground through mechanical transmission parts thereby eliminating the erroneous gear indication in the display unit.

The circuit comprises of a microcontroller and NPN transistors wherein base of the transistors are interfaced to the microcontroller which in turn is interfaced to sensor transmission ground through gear selectors. When a varying ground potential is sensed by the microcontroller at a particular gear pin, it triggers the respective transistor. Collector end is supplied with +5V from the display device. Also, collector side of the NPN transistors are pulled up (hooked up) with resistors of different values to attain predetermined voltage drops for identification of the selected gear by the display device. Emitter side of the NPN transistors are permanently connected to electrical ground which provides the isolated ground path.

ADVANTAGES AND HIGHLIGHTS OF INVENTION

1. Having thus set forth the nature of the invention, what is claimed herein is: Prevention of erroneous gear indication on the display device by providing an isolated ground path for the Gear position sensor through transistors. This isolated ground to the GPS through transistors remains immune to the build-up of resistance in the transmission ground path (consisting of the mechanical transmission parts) and prevents the wrong gear indication on the display unit.
2. The isolated grounding mechanism of Gear Position Sensor (GPS) of claim 1 wherein the electronic circuit structure includes a microcontroller interfaced to the gear pins in the input side and to NPN transistors at the output side. When a varying ground potential is sensed by the microcontroller at a particular gear pin during the gear drum pin contact with the sensor pin, it triggers the respective transistor to turn ON.
3. The isolated grounding mechanism of Gear Position Sensor of claim 2 wherein isolated grounding is achieved through the emitter path after the transistor is turned ON.
4. The isolated grounding mechanism of Gear Position Sensor of claim 2 wherein resistors of different values are connected in the transistor collector end to achieve different voltage drops for the identification of the different gears.
5. The isolated grounding mechanism of Gear Position Sensor of claim 2 wherein the voltage drop sensed by the display unit is the collector to emitter voltage drop of the transistor and the drop across the corresponding resistor connected to it in the collector end. Based on this voltage drop, display device displays the gear position as programmed/instructed in the software.
6. The isolated grounding mechanism of Gear Position Sensor of claim 1 wherein Gear position sensor remains immune to the varying ground resistance sensed in the mechanical transmission parts.

DESCRIPTION OF DRAWINGS

Fig 1: Block diagram of the present invention

Fig 2: Circuit diagram of the sensor as per present invention.

Fig 3: Block diagram of the relevant electrical, electronic and mechanical components of a vehicle having a manual transmission and equipped with the present invention

Fig 4: Table 1 title TYPICAL VOLATGE VALUES FOR GEAR IDENTIFICATION
Pull up resistance – 500 O (Typical value) : Voltage drops for identifying the various gears by the display device is indicated in the table.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An example of an embodiment in which the invention claimed herein is advantageously used to determine the selected gear position of a transmission gear in an automotive vehicle is now described with particular reference to the attached figures.

Fig 1&2 depicts the circuit diagram of the present invention.

Base of the NPN transistors are connected to the microcontroller output pins. The gear pins are connected to the input side of microcontroller. During gear shift, when a gear pin makes contact with the sliding pin in the gear drum, transmission ground (varying ground potential) is sensed at the gear pin by the microcontroller which in turn turns ON the respective NPN transistor. Identical NPN transistors and resistors with different values are used in all gear indication paths. For indication of Gear-1, Resistor value of 160O is connected to the collector end of the 1stNPN transistor. For indication of Gear-2, Resistor value of 330O is connected to the collector end of the 2nd NPN transistor. For indication of Gear-3, Resistor value of 528O is connected to the collector end of the 3rd NPN transistor. For indication of Gear-4, Resistor value of 820O is connected to the collector end of the 4th NPN transistor. For indication of Gear 5, Resistor value of 1.5kO is connected to the collector end of the 5th NPN transistor. Emitter end of the transistors are soldered to a common ground which is permanently connected to Battery negative for firm grounding claimed herein as isolated ground.

5V input from the display device is applied to collector end of the transistor of all the gears. Base of every transistor will get the trigger from the microcontroller when it senses transmission ground input at a gear pin of the selected gear when the corresponding gear is engaged. At any point of time, one gear will be engaged; hence one transistor will be turned ON when the microcontroller senses the transmission-ground input from the gear pin contact. Transmission-ground input value may vary from 0 O ~ 1 kO. When the gear is engaged, corresponding contact in the sensor is engaged by gear pin contact which makes the transmission-ground available to the microcontroller to switch ON the corresponding transistor. When the transistor is turned ON, 5V input from the display device is connected to the firm ground which is isolated from transmission-ground. Electrical ground potential (claimed isolated ground) value will be ~0 O. Based on the voltage drop across the resistor and the connected transistor, voltage output will vary which would be fed to display device as input. Based on the voltage fed to the display device, gear position will be indicated to the user as instructed in its software.

Fig 3 is the block diagram of the transmission system wherein the present invention in the Gear position sensor (2) provides isolated grounding to the system. Gear position sensor (2) gives voltage signal to the display device (1) when a transmission ground potential (unstable) is achieved through mechanical transmission parts (3) for the selected gear enabling the circuit to get closed through isolated ground as depicted in the block diagram. The mechanical transmission parts are designated by reference number (3). The transmission parts (3) include a gear pin, spring, gear drum, star spindle, arm stopper, spring and crank case which collectively provide an unstable ground path.

The disclosure is to the extent of few embodiments and examples for sake of understanding the invention and these shall not limit the scope of the invention. All the variations and modifications are within the spirit and scope of the invention.

Claims:1. A gear position sensor with isolated grounding means and a variable resistive arrangement for displaying the selected gear from the gear shift drum of a vehicle on a display means comprising :
- a microcontroller with a plurality of input end pins N and a corresponding plurality of output end pins N.
- a gear position sensor means with a plurality of N gear sensor pins, representative of N selectable gears and each gear sensor pin at one end connected to one of the corresponding plurality of N input pins of microcontroller, thereby enabling the microcontroller to detect the variable ground potential, each ground potential value corresponding to a specific gear pin contacting the sliding pin of the gear shift drum, and which is representative of the selected gear, and further the other end of each gear sensor pin is connected to electrical ground, and
- a gear select display means with a plurality of N resistors arranged with a corresponding set of N transistors together forming a plurality of N transistor-resistor combinations, each combination at one end connected to corresponding N output pins of microcontroller thereby enabling the microcontroller to trigger a corresponding transistor on the basis of detected ground potential which is representative of specific gear selected and further the arrangement includes the non-transistor facing side of each resistor i.e., emitter side of transistor is connected to electrical ground and the transistor facing side of each resistor i.e., collector side of transistor is connected to supply end of the display means, the said sensor characterised in the arrangement of providing isolated path for the gear position sensor through a plurality of transistors.

2. The gear position sensor with isolated grounding technique as claimed in claim 1 wherein the each of the resistance has a specific ohm value, which is so calculated to achieve a predetermined specific voltage drop when a corresponding specific gear sensor pin contacts the sliding pin of the gear shift drum for detecting a selected gear amongst the N selectable gears in the vehicle.