DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
A GEAR SHIFT PREVENTION SYSTEM AND METHOD THEREOF

Applicant:
BEML Limited
A company Incorporated in India under the Companies Act, 1956
Having Address As:
BEML Soudha, 23/1, 4th Main,
Sampangirama Nagar, Bengaluru - 560 027,
Karnataka, India

The following specification particularly describes the invention and the manner in which it is to be performed.
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[001] The present invention claims priority from Indian patent application numbered IN 202241052478 filed on 14th September, 2022.

FIELD OF THE INVENTION
[002] The present invention generally relates to a gear shift prevention system, and more specifically to a system to prevent gear shifting to higher gears during inching operation and method of prevention thereof.
BACK GROUND OF THE INVENTION
[003] A motor grader uses a hydrostatic transmission operated by a gear shift lever to engage the required forward/reverse gears. A Transmission Control Unit (TCU) receives inputs of gear selection from the gear shift lever and operates appropriate solenoid valves to activate desired clutches.
[004] The gear shift lever typically has four positions - parking, neutral, forward and reverse. Forward gear is engaged when gear shift lever is moved fore from neutral position. For engaging reverse gear, gear shift lever is moved aft from neutral position. Generally, motor grader transmission has 8 forward and 8 reverse gears. An inching pedal is provided for a smooth speed control while shifting lower gears. The Inching pedal allows the operator to move forward/backward slowly over short distances for fine positioning of the equipment. The purpose of the inching pedal is to disengage the transmission without shifting the gear lever into neutral for slowing down the equipment and also transfer the engine power at higher RPM for work control operation. Therefore, the operator depresses the inching pedal which gear shifting up to 3rd gears in forward and reverse. However, shifting in higher gears lead to partial engagement of clutch at a high torque value and may cause serious damage to the transmission when the inching pedal is actuated.
[005] Hence there is need of a system to prevent shifting of transmission in higher gears during inching operation.

OBJECTS OF THE INVENTION
[006] Main object of the present disclosure is to provide a system for controlling gear shifting in a transmission.
[007] Another object of the present disclosure is to provide a system for preventing gear shifting in higher forward/reverse gears during inching operation.
[008] Another object of the present disclosure is to provide a system for preventing an operator from accidently shifting into higher forward/reverse gears when inching pedal is depressed.
[009] Yet another object of the present disclosure is to provide a system for preventing directional shift when vehicle speed is more than or equal to 1stgear speed at engine idle rpm.
[0010] Yet another object of the present disclosure is to provide a system for preventing engagement of transmission gear from neutral to forward/reverse 1st gear when vehicle speed is more than or equal to 1st gear speed at engine high idle rpm and also engine rpm is more than 1000 RPM.
[0011] Yet another object of the present disclosure is to provide a method for preventing inadvertent gear shifting in a transmission during inching.

SUMMARYOF THE INVENTION
[0012] Before the present system is described, it is to be understood that this application is not limited to the particular machine, device or system, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a gear shift prevention system and the aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[0013] The present subject matter discloses a gear shift prevention system for a transmission. The system comprises of a transmission control unit (TCU), a gear shift lever, an engine speed sensor, a vehicle speed sensor, a display, transmission solenoid valves and a proximity switch. The proximity switch is provided on an inching pedal to detect depressed and released state of the inching pedal and provide the respective signals to the TCU. The TCU receives signals of engine rpm, vehicle speed and shift lever position from the engine speed sensor, the vehicle speed sensor and the gear shift lever, respectively. The TCU show the data related to gear selection on the display. Further, the TCU controls the transmission solenoid valves for shifting the transmission to desired gear. The TCU prevents the shifting of transmission to high gears (4th – 8th gears) when inching pedal is depressed. Further, TCU prevents the directional shifting when vehicle speed is more than a first predetermined vehicle speed limit S1. Moreover, the TCU prevents the shifting of transmission from neutral to first gear when vehicle speed is more than a second predetermined speed limit S2.

STATEMENT OF INVENTION
[0014] The present invention discloses a gear shift prevention system for a transmission comprising a gear shift lever for indicating gear selection information, transmission solenoid valves configured to shift the transmission to a desired gear, a proximity switch configured to detect the depressed and released states of an inching pedal. A transmission control unit is configured to control the transmission solenoid valves to prevent inadvertent shifting to higher gears during inching operation in both forward and reverse directions based on signals received from the proximity switch is configured to allow directional shifting upon detecting the vehicle speed being less than or equal to a predetermined speed limit, during depressed state of the inching pedal. The TCU is configured to prevent shifting the transmission from neutral to the first gear forward/reverse upon detecting the vehicle speed exceeding a predetermined speed limit or the engine speed exceeding a predefined threshold RPM, during depressed state of the inching pedal. The TCU is configured to restrict the shifting the gear to the next gear when a shift is desired from a lower gear to a higher gear, during depressed state of the inching pedal. The TCU is configured to allow downshifting to a desired gear when the currently engaged gear is the higher gear, during depressed state of the inching pedal. The TCU is configured to prevent shifting to a higher gear when the currently engaged gear is in the third gear or higher and an upshift is requested, during depressed state of the inching pedal.
[0015] The present invention further discloses a method for preventing inadvertent gear shifting in a transmission comprising detecting the depressed and released states of an inching pedal by a proximity switch, receiving signals related to engine RPM, vehicle speed, and gear shift lever position from an engine speed sensor , the vehicle speed sensor , and the gear shift lever. Gear shift lever controlling transmission solenoid valves based on the received signals to shift the transmission to a desired gear and preventing inadvertent shifting to higher gears during inching operation in both forward and reverse directions by the transmission control unit based on the signals from the proximity switch, the engine speed sensor , the vehicle speed sensor , and the gear shift lever . The directional shifting is allowed only when the vehicle speed is less than or equal to a predetermined speed limit, during depressed state of the inching pedal. The shifting from neutral to the first gear forward/reverse is prevented when the vehicle speed exceeds a predetermined speed limit or the engine speed exceeds a predefined threshold RPM, during depressed state of the inching pedal. The shifting of the transmission to a predefined gear is allowed when a shift is desired from a lower gear to a higher gear, during depressed state of the inching pedal.

BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and device disclosed in the document and the drawing. The detailed description is described with reference to the following accompanying figures.
[0017] Figure 1 illustrates a block diagram of a shift control system for a transmission, in accordance with an embodiment of the present subject matter; and
[0018] Figure 2 illustrates a flow chart of a shift control system for a transmission, in accordance with an embodiment of the present subject matter.
[0019] The figures depict various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF INVENTION
[0020] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any devices and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, devices and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0021] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[0022] The present subject matter discloses a gear shift prevention system (100) for a transmission. Figure 1 shows a block diagram of the gear shift prevention system (100). The system (100) comprises of a transmission control unit (TCU) (102) to control transmission in the vehicle, a gear shift lever (104), an engine speed sensor (106), a vehicle speed sensor (108), display (112), transmission solenoid valves (114) and a proximity switch (110). The proximity switch (110) is provided on an inching pedal to detect depressed and released state of the inching pedal and provide the respective signals to the TCU (102). The TCU (102) further receives signals of engine rpm, vehicle speed and shift lever position from the engine speed sensor (106), the vehicle speed sensor (08) and the gear shift lever (104), respectively. The TCU (102) show the data related to gear selection on the display (112). Further, the TCU (102) controls the transmission solenoid valves (114) for shifting the transmission to desired gear.
[0023] The inching operation is sensed by the proximity switch (110) which will close and give ground signal to the TCU (102) when inching pedal is depressed. The TCU (102) prevents the operator from inadvertently/accidently shifting to higher gears (from 4th to 8th gear) during inching operation both in forward/reverse directions. During directional shift, the TCU (102) checks for the vehicle speed and only when the speed is <= 2 Km/h (Max speed in 1st gear at low idle engine rpm) directional shifting is allowed otherwise it will restrict to current gear. During up-shift from a neutral to 1st gear forward/reverse the TCU (102) checks for the vehicle speed and only when the speed is <= 4 Km/h (Max speed in 1st gear at high idle engine rpm) otherwise it will restrict to neutral gear only.
[0024] In another embodiment, when an operator changes the shift lever position (SLP) on the gear shift lever, TCU (102) checks the state of inching pedal. If inching pedal is not depressed, the transmission is shifted to desired gear as per the SLP. When the inching pedal is depressed, TCU (102) works as follows’
1. If shift is desired from a lower gear (e.g., 1st or 2nd gear) to higher gear (e.g., 4th, 5th, 6th, 7th or 8th gear), the TCU (102) shifts transmission to a predefined gear (e.g., 3rd gear).
2. If downshift is desired from gear >= 3rd gear, the TCU (102) shifts transmission to the desired gear.
3. If up-shift is desired from gear >= 3rd gear, the TCU (102) prevents the shifting of transmission to desired position.
4. If SLP is moved from neutral to 1st gear and vehicle speed is greater than a second predetermined speed S2 (e.g., 4 km/hr), the TCU (102) prevents the shifting of transmission to desired position.
5. If directional shift (from any gear to neutral position) is requested and vehicle speed is greater than a first predetermined speed S1 (e.g., 2 km/hr), the TCU (102) prevents the shifting of transmission to desired position.
[0025] Figure 2 illustrates a flowchart for the transmission control strategy. When the engine is in running condition and operator tries to shift the gear from neutral to forward/reverse gear, the TCU (102) checks, whether inching pedal is depressed or not depressed. If inching pedal is not depressed then TCU (102) will allow to shift the gear in desired position. If inching pedal is depressed then TCU (102) will check for current gear position,
a) whether the currently engaged gear is in 1st or 2nd in forward/reverse, if "Yes" then the TCU (102) will check whether selected gear is in 4-8 forward/reverse gear position, if "Yes" then the TCU (102) will allow to engage forward/reverse 3rd gear only.
b) If current engaged gear is not in 1st or 2nd in forward/reverse, then the TCU (102) will check whether the currently engaged gear is in 3rd or higher gear in forward/reverse and downshift is requested, if "Yes" then TCU (102) will allow to shift the gear in desired position. If engaged gear is in 3rd or in higher gear and up shift is requested then the TCU (102) will not allow to shift the gear, the TCU (102) will maintain current gear position in transmission.
c) whether SLP moves from neutral to 1st gear forward/reverse, if "Yes" then the TCU (102) will allow to shift the gear to 1st position if vehicle speed is less and equal to a second predetermined speed limit (e.g., 4 km/h) and engine speed is less than 1000 rpm. If vehicle speed is more than second predetermined speed limit (e.g., 4 km/h) or engine speed is more than 1000 rpm then the TCU (102) will not allow to shift the gear.
d) whether engaged gear is in 1st or 2nd forward/reverse gear and selected gear shift is from 1st to 2nd gear or from 1st to 3rd gear or from 2nd to 3rd gear, if "Yes" then the TCU (102) will allow to shift to desired gear, and if "No" then the TCU will check for condition "b" above.
e) Whether directional shift is requested and vehicle speed is less than or equal to a first predetermined speed limit (e.g., 2 km/h), If "Yes" then the TCU (102) will allow to shift the gear otherwise it will restrict the transmission to currently engaged gear.
[0026] Accordingly, present invention discloses a gear shift prevention system (100) for a transmission comprising a gear shift lever (104), an engine speed sensor (106), a vehicle speed sensor (108), a display (112) for indicating gear selection information, transmission solenoid valves (114) configured to shift the transmission to a desired gear, a proximity switch (110) configured to detect the depressed and released states of an inching pedal. A transmission control unit (TCU) (102) is configured to control the transmission solenoid valves (114) to prevent inadvertent shifting to higher gears during inching operation in both forward and reverse directions based on signals received from the proximity switch (110), engine speed sensor (106), vehicle speed sensor (108), and gear shift lever (104). The TCU (102) is configured to allow directional shifting upon detecting the vehicle speed being less than or equal to a predetermined speed limit, during depressed state of the inching pedal. The TCU (102) is configured to prevent shifting the transmission from neutral to the first gear forward/reverse upon detecting the vehicle speed exceeding a predetermined speed limit or the engine speed exceeding a predefined threshold RPM, during depressed state of the inching pedal. The TCU (102) is configured to restrict the shifting the gear to the next gear when a shift is desired from a lower gear to a higher gear, during depressed state of the inching pedal. The TCU (102) is configured to allow downshifting to a desired gear when the currently engaged gear is the higher gear, during depressed state of the inching pedal. The TCU (102) is configured to prevent shifting to a higher gear when the currently engaged gear is in the third gear or higher and an up-shift is requested, during depressed state of the inching pedal.
[0027] The present invention further discloses a method for preventing inadvertent gear shifting in a transmission comprising (a) detecting the depressed and released states of an inching pedal by a proximity switch (110), (b) receiving signals related to engine RPM, vehicle speed, and gear shift lever position from an engine speed sensor (106), a vehicle speed sensor (108) and a gear shift lever (104), respectively, (c) controlling transmission solenoid valves (114) based on the received signals to shift the transmission to a desired gear and (d) preventing inadvertent shifting to higher gears during inching operation in both forward and reverse directions by the transmission control unit (TCU) (102) based on the signals from the proximity switch (110), the engine speed sensor (106), the vehicle speed sensor (108), and the gear shift lever (104). The directional shifting is allowed only when the vehicle speed is less than or equal to a predetermined speed limit, during depressed state of the inching pedal. The shifting from neutral to the first gear forward/reverse is prevented when the vehicle speed exceeds a predetermined speed limit or the engine speed exceeds a predefined threshold RPM, during depressed state of the inching pedal. The shifting of the transmission to a predefined gear is allowed when a shift is desired from a lower gear to a higher gear, during depressed state of the inching pedal.
[0028] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include the following.
[0029] Some embodiments of the subject matter provide a system for controlling gear shifting in a transmission.
[0030] Some embodiments of the subject matter provide a system for preventing gear shifting in higher forward/reverse gears during inching operation.
[0031] Some embodiments of the subject matter provide a system for preventing an operator from accidently shifting into higher forward/reverse gears when inching pedal is depressed.
[0032] Some embodiments of the subject matter provide a system for preventing directional shift when vehicle speed is more than or equal to 1st gear speed at engine idle rpm.
[0033] Some embodiments of the subject matter provide a system for preventing engagement of transmission gear from neutral to forward/reverse 1st gear when vehicle speed is more than or equal to 1st gear speed at engine high idle rpm and also engine rpm is more than 1000 RPM.
[0034] Some embodiments of the subject matter provide a method for preventing inadvertent gear shifting in a transmission during inching.
[0035] Following is a list of elements and reference numerals used to explain various embodiments of the present subject matter.
Reference Numeral Element Description
100 Gear shift prevention system
102 Transmission Control Unit (TCU)
104 Gear shift lever
106 Engine speed sensor
108 Vehicle speed sensor
110 Proximity switch for inching pedal
112 Display
114 Transmission solenoid valves

,CLAIMS:
1. A gear shift prevention system (100) for a transmission, comprising:
a gear shift lever (104);
an engine speed sensor (106);
a vehicle speed sensor (108);
a display (112) for indicating gear selection information;
transmission solenoid valves (114) configured to shift the transmission to a desired gear;
a proximity switch (110) configured to detect the depressed and released states of an inching pedal; and
a transmission control unit (TCU) (102) configured to control the transmission solenoid valves (114) to prevent inadvertent shifting to higher gears during inching operation in both forward and reverse directions based on signals received from the proximity switch (110), engine speed sensor (106), vehicle speed sensor (108), and gear shift lever (104).
2. The gear shift prevention system (100) as claimed in claim 1, wherein the TCU (102) is configured to allow directional shifting upon detecting the vehicle speed being less than or equal to a predetermined speed limit, during depressed state of the inching pedal.
3. The gear shift prevention system (100) as claimed in claim 1, wherein the TCU (102) is configured to prevent shifting the transmission from neutral to the first gear forward/reverse upon detecting the vehicle speed exceeding a predetermined speed limit or the engine speed exceeding a predefined threshold RPM, during depressed state of the inching pedal.
4. The gear shift prevention system (100) as claimed in claim 1, wherein the TCU (102) is configured to restrict the shifting the gear to the next gear when a shift is desired from a lower gear to a higher gear, during depressed state of the inching pedal.
5. The gear shift prevention system (100) as claimed in claim 1, wherein the TCU (102) is configured to allow downshifting to a desired gear when the currently engaged gear is the higher gear, during depressed state of the inching pedal.
6. The gear shift prevention system (100) as claimed in claim 1, wherein the TCU (102) is configured to prevent shifting to a higher gear when the currently engaged gear is in the third gear or higher and an up-shift is requested, during depressed state of the inching pedal.
7. A method for preventing inadvertent gear shifting in a transmission, comprising:
detecting the depressed and released states of an inching pedal by a proximity switch (110);
receiving signals related to engine RPM, vehicle speed, and gear shift lever position from an engine speed sensor (106), a vehicle speed sensor (108) and a gear shift lever (104), respectively;
controlling transmission solenoid valves (114) based on the received signals to shift the transmission to a desired gear; and
preventing inadvertent shifting to higher gears during inching operation in both forward and reverse directions by the transmission control unit (TCU) (102) based on the signals from the proximity switch (110), the engine speed sensor (106), the vehicle speed sensor (108), and the gear shift lever (104).

8. The method as claimed in claim 8, wherein the directional shifting is allowed only when the vehicle speed is less than or equal to a predetermined speed limit, during depressed state of the inching pedal.
9. The method as claimed in claim 8, wherein the shifting from neutral to the first gear forward/reverse is prevented when the vehicle speed exceeds a predetermined speed limit or the engine speed exceeds a predefined threshold RPM, during depressed state of the inching pedal.
10. The method as claimed in claim 8, wherein shifting the transmission to a predefined gear is allowed when a shift is desired from a lower gear to a higher gear, during depressed state of the inching pedal.