A Device And Method For Detecting Gear Position

CLIAMS:I claim, 1. A device (100) for detecting gear position, said device (100)comprising, an engine speed sensor (101); a means to detect a trigger (102) for change in the gear position; a processing means (103) adapted to receive said engine speed and said trigger for change in the gear position, said processing unit (103) adapted to determine a rate of change of the engine speed during the changing of the gear position and determine a corresponding gear ratio to detect the gear position. 2. A device as claimed in claim (1), wherein said trigger for the change in gear position is the output of a throttle position sensor (102a). 3. A device as claimed in claim (1) wherein, said trigger for the change in gear position is the output of a clutch switch (102b). 4. A device as claimed in claim (1), wherein said trigger for the change in gear position is the combined output of a throttle position sensor (102a) and a clutch switch (102b). 5. A device as claimed in claim (1) wherein said processing means is provided with the engine load conditions from any known engine load sensing means. 6. A device as claimed in claim (1) wherein said processing means (103) includes a sampling means (104) to sample the received engine speed on detecting the trigger for change in gear position. 7. A device as claimed in claim (1) wherein the processing means (103) of said device (100) is provided with a memory (105) which includes predetermined gear ratios for different rates of change of engine speed and engine load stored in it. 8. A device as claimed in claim (1) wherein said processing means (103) includes a comparator (106) which compares the determined rate of change of engine speed with the predefined rates of change of engine speed and corresponding engine load stored in the memory (105). 9. A method for detecting gear position, said method comprising, measuring the engine speed and transmitting the measured engine speed to a processing means; detecting a trigger for change in gear position and transmitting said trigger to the processing means; measuring engine load by an engine load sensing means; sampling the engine speed by a sampling means in said processing means for a predefined time interval after detecting of said trigger; determining the rate of change of engine speed from said sampled engine speed; comparing said determined rate of change of engine speed with a predefined rate of change of engine speeds and the corresponding engine load for different gear ratios stored in a memory associated with the processing means; detecting of the gear position based on the said comparison of the rates of change of engine speed. 10. A method as claimed in claim (9) wherein, the sampling rate is synchronous to the engine speed. ,TagSPECI:Field of the invention:

[001] The invention relates to a device and method for detecting gear position. Background of the invention:

[002] Detecting the position of the gear in which a vehicle is being driven is necessary for the operation of different vehicle control systems. Presently for detecting the gear position, dedicated gear position sensors are used. Gear position can also be determined based on the engine speed sensor and vehicle speed sensor. In such systems, the engine speed is measured by an engine speed sensor and the vehicle speed is measured by a vehicle speed sensor. The engine speed and vehicle speed data from the two sensors is compared real time with the engine and vehicle speed data for the different gear ratio stored in a memory of a control unit of the vehicle. Based on this comparison the active gear can be detected.

[003] US5562569 discloses a system for detecting vehicle gear position based on the engine speed and the vehicle speed. Brief description of the invention:

[004] In accordance with one embodiment of the invention it is envisaged that a device for detecting gear position comprises an engine speed sensor and a means to detect a trigger for change in the gear position. A processing means is adapted to receive the engine speed and the trigger for change in the gear position. The processing unit is adapted to determine a rate of change of the engine speed during the changing of the gear position and determine a corresponding gear ratio to detect the gear position by comparing the measured rate of change of engine speed with rate of change of engine speed corresponding to the different gear ratios and the engine load stored in a memory associated with the processing unit. The trigger for change in gear position can be from a throttle position sensor or a clutch sensor.

[005] The present invention proposes a device and method for detecting the gear position of a vehicle without using additional sensors. The sensors required for the detection of the gear position in accordance with this invention is the engine seed sensor and throttle position sensor which are mandatory sensors in a vehicle. Brief description of the drawings:

[006] The embodiments of the present invention is described with reference to the following drawings,

[007] Fig. 1 of the accompanying drawing illustrates a device for detecting gear position in accordance with one embodiment of the invention;

[008] Fig. 2 of the accompanying drawings illustrates a flowchart for a method for detecting gear position in accordance with one embodiment of the invention;

[009] Fig. 3 of the accompanying drawings illustrates the engine speed signal and the triggers corresponding to change in gear position in accordance with one embodiment of the invention;

[0010] Fig. 4 of the accompanying drawings illustrates a graph of engine speed variation at different gear positions in accordance with one embodiment of the invention; and

[0011] Fig. 5 of the accompanying drawings illustrates a graph for determining rate of change of engine speed for a particular gear position, in accordance with one embodiment of the invention. Detailed description of the embodiments:

[0012] Fig. 1 of the accompanying drawing illustrates a device for detecting gear position in accordance with one embodiment of the invention.

[0013] The device (100) for detecting gear position comprises an engine speed sensor (101); a means to detect a trigger (102) for change in the gear position; and a processing means (103) adapted to receive said engine speed and said trigger for change in the gear position. The processing unit (103) is adapted to determine a rate of change of the engine speed during the changing of the gear position and determine a corresponding gear ratio to detect the gear position.

[0014] In accordance with one embodiment of the invention, the trigger for the change in gear position is the output of a throttle position sensor (102a) which is also used to determine the engine load. In another embodiment of the invention the trigger for the change in gear position is the output of a clutch switch (102b). In a further embodiment the trigger for the change in gear position is the combined output of a throttle position sensor (102a) and a clutch switch (102b). In another embodiment the engine load may be sensed by any known engine load sensing means for example, manifold pressure, engine speed, air mass sensor and the like.

[0015] In one embodiment of the invention the processing means (103) includes a sampling means (104) to sample the received engine speed on detecting the trigger for change in gear position. The sampling means (104) samples the engine speed at a predefined intervals and the processing means (103) determines the rate of change of engine speed from the samples. The processing means (103) of the device (100) is provided with a memory (105) which has predetermined gear ratios for different rates of change of engine speed corresponding to engine load stored in it. The processing means (103) includes a comparator (106) which compares the determined rate of change of engine speed with the predefined rates of change of engine speed corresponding to engine load stored in the memory (105). Based on the comparison the gear position of the vehicle can be detected.

[0016] Fig. 2 of the accompanying drawings illustrates a flowchart for a method for detecting gear position in accordance with one embodiment of the invention.

[0017] The method for detecting gear position starts with the step of measuring the engine speed and transmitting the measured engine speed to a processing means (S0). The second step (S1) is detecting a trigger for change in gear position and transmitting the trigger to the processing means. Sampling the engine speed (S2) is done by a sampling means in the processing means for a predefined time interval after detecting the trigger. The rate of change of engine speed is determined (S3) from said sampled engine speed by the processing means. A comparator in the processing means compares the determined rate of change of engine speed with a predefined rate of change of engine speeds for different gear ratios and the corresponding engine load stored in a memory associated with the processing means (S4). Based on the comparison of the rate of change of engine speed the gear position is detected (S5). In accordance with one embodiment of the invention the sampling rate is synchronous to the engine speed.

[0018] Fig. 3 of the accompanying drawings illustrates the engine speed signal and the triggers corresponding to change in gear position in accordance with one embodiment of the invention.

[0019] The variation in the engine speed is illustrated in Fig. 3 as signal ES. The trigger for sampling of the engine speed is obtained from either the throttle sensor or the clutch sensor. The output of the throttle sensor is indicated by the signal TH and the clutch sensor output is indicated by the signal CS in the figure. The trigger point tg, indicates the time instant which indicates the trigger for change in the gear position. When the gear is to be changed the driver releases the accelerator which closes the throttle which is indicated by a sharp dip in the throttle sensor output (TH) as shown in the figure. Similarly when the gear is to be changed, the driver presses the clutch which is visible as a change in the output (CS) of the clutch sensor. The engine speed signal ES is sampled by the sampling means after the instant tg. The trigger to start sampling the engine speed signal may be taken from the throttle position sensor signal (TH) or the clutch sensor signal (CS) or a combination of both these signals. The engine speed signal (ES) is sampled by the sampling means for a predetermined time duration (Ts). During the engine speed sampling phase, the throttle position sensor input is referred to detect the engine load. The change in the engine speed (?ES) is determined from the sampling output by the processing means and the rate of change of the engine speed is determined.

[0020] Fig. 4 of the accompanying drawings illustrates a graph of engine speed variation at different gear positions in accordance with one embodiment of the invention. The rate of change of engine speed is different at different gear positions (G1, G2, G3, G4, and G5). Each of the gear position has a unique operating range in terms of the engine speed.

[0021] Fig. 5 of the accompanying drawings illustrates a graph for determining rate of change of engine speed for a particular gear position, in accordance with one embodiment of the invention. For a particular gear position Gx, the change in engine speed ?ESGx is equal to the engine speed gradient at that gear Gx for the specific engine load.

[0022] Based on the change in the engine speed for a particular gear Gx, the rate of change in engine speed is determined. The memory associated with the processing means has the rate of change of engine speed at different gear ratios calibrated and stored in it. The real time change in engine speed is determined and then compared with the calibrated stored rate of change in engine speed and the engine load. The gear detection is possible when the rate of change of engine speed with respect to time is compared to the calibrated rate for specific gear position with respect to the engine load.

[0023] The proposed strategy uses the rate of change of engine speed whenever a gear is engaged, either up-shift or down-shift, where the engine speed follows a specific pattern for the engaged gear and the engine speed gradient is always reproducible within the threshold limits of each gear ratio.

[0024] In accordance with one embodiment of the invention, the present invention is implemented as a programmed logic in said processing means. The programmed logic detects the change in engine speed on a real time basis whenever triggered, the trigger can either be by the throttle position signal, as the throttle will be normally closed during gear change which can be used as a trigger for detection of engine speed gradient, or using the clutch switch input, since for gear change the clutch will be disengaged from the power train. Based on these triggers, the engine speed variation is checked at desired sampling rate and hence engine speed gradient is obtained. For example, engine speed increase of ?ES rpm / sec can be used to detect specific gear ratio which can be calibrated based on the vehicle transmission data and the corresponding engine load. The gear detection is done effectively during both up-shift and down-shift using the programmed logic in accordance with one embodiment of the invention.

[0025] It must be understood that the embodiments explained in the above paragraphs are only illustrative and do not limit the scope of the disclosure in terms of sensors used for detecting certain parameters. Any known means for detecting or measuring of different parameters as disclosed would also be within the scope of the invention. The scope of this disclosure is only limited by the scope of the claims.