Claims:WE CLAIM:
1. A power shuttle transmission system of a vehicle, said transmission system comprising:
a. a forward clutch (10a) configured to be engaged for propelling the vehicle in a forward direction and a reverse clutch (10b) configured to be engaged for propelling the vehicle in a reverse direction and said forward clutch and said reverse clutch configured to be simultaneously disengaged during gear shifting; and
b. a hydraulic circuit (20) comprising a reservoir (28), a hydraulic pump (27) and a plurality of valves for controlling magnitude and direction of the pressure delivered to said clutches (10a, 10b), said plurality of valves including atleast one modulation valve (25) configured to allow modulation of time required for engagement of said clutches (10a, 10b), said modulation valve (25) comprising a piston with a first orifice, said first orifice being always in fluid communication with said reservoir (28);
wherein said modulation valve (25) comprises a second orifice (254) in parallel to said first orifice and said system comprises atleast one switching valve (26) for opening and closing said second orifice (254) for changing the desired modulation time.
2. The power shuttle transmission system as claimed in claim 1, wherein said plurality of valves includes atleast one priority valve (21) configured to allow a fixed flow rate of hydraulic fluid through the transmission system irrespective of the input flow rate and provide the rest of the fluid to flow for lubrication of said clutches (10a, 10b).
3. The power shuttle transmission system as claimed in claim 1, wherein said plurality of valves includes atleast one inching valve (22) configured to enable disengagement of said clutches (10a, 10b) during gear shifting and also to enable partially engaging the clutch corresponding to the desired direction of movement to facilitate control slow movement of the vehicle.
4. The power shuttle transmission system as claimed in claim 1, wherein said plurality of valves includes atleast one direction control valve (23) configured to facilitate selection of one of said clutches (10a, 10b) to be engaged based on the operator’s input.
5. The power shuttle transmission system as claimed in claim 1, wherein said plurality of valves includes atleast one relief valve (24) configured to facilitate relieving of hydraulic back pressure exerted on said system.
6. The power shuttle transmission system as claimed in claim 5, wherein said system comprises an electrical switch coupled to said switching valve for facilitating manual switching of said switching valve (26), said electrical switch being an ON/OFF switch.
7. The power shuttle transmission system as claimed in claim 6, wherein in an ON state, said switch switches said switching valve to select said second orifice (254).
8. The power shuttle transmission system as claimed in claim 7, wherein said system comprises a hand-operated lever for facilitating operation of said direction control valve (23), said switch being mounted on said lever.

Dated this 04th day of October, 2019

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT CHENNAI

, Description:
FIELD
The present disclosure relates to the field of power shuttle transmission systems of vehicles like tractors.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
A power shuttle mechanism is a mechanism actuated by a power shuttle lever available in the cabin of a vehicle such as a tractor, which makes the vehicle stop and reverse the direction of motion and move in the same speed. The power shuttle mechanism does not require a clutch to be operated. Hence, the name ‘power shuttle’. The power shuttle mechanism is driven by a hydraulic circuit comprising a plurality of valves. In a forward/reverse mode, pressure is built in the hydraulic circuit due to flow of hydraulic fluid to the wet clutches. The actuation of the wet clutches is controlled by the power shuttle transmission valve. A conventional power shuttle transmission valve assembly consists of a priority valve, a modulation valve, a relief valve, a directional control valve and a proportional inching valve. The priority valve allows a fixed mass flow rate of hydraulic fluid through the hydraulic circuit irrespective of the input mass flow rate and provides the rest of the fluid to flow for lubrication of the clutches. The modulation-cum-relief valve allows modulation of time required for clutch engagement by setting the maximum pressure. The direction control valve allows selection of the clutch based on the operator’s input. The proportional inching valve disengages the clutch during gear shifting and also controls slow movement (i.e., inching) of the vehicle.
A conventional mechanical power shuttle transmission valve has a single modulation time. The modulation time of the power shuttle transmission valve when optimized for providing the required pressure modulation during forward/reverse operation while the clutch is fully engaged, does not provide the required rate of increase in momentum while performing gear shifting operations, which require disengaging and engaging the clutch.
When the modulation time was reduced for improving the shifting response, forward/reverse (F/R) shuttling was compromised in the form of increase in jerkiness. The operator’s expectation is to get a very minimum jerk during the operation of F/R shuttling, as the F/R shuttling is the most frequent operation performed in a vehicle with a power shuttle transmission.
Therefore, there is felt a need to provide a power shuttle transmission system for mitigating the aforesaid drawback.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a power shuttle transmission system for a vehicle, which has reduced response time during gear shifting.
An object of the present disclosure is to provide a power shuttle transmission system for a vehicle, which provides a jerk-free F/R shuttling operation.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages a power shuttle transmission system of a vehicle. The power shuttle transmission system of the present disclosure comprises a forward clutch and a reverse clutch and a hydraulic circuit. The forward clutch is configured to be engaged for propelling the vehicle in the forward direction and the reverse clutch is configured to be engaged for propelling the vehicle in the reverse direction. The forward clutch and the reverse clutch are configured to be simultaneously disengaged during gear shifting. The hydraulic circuit comprises a reservoir, a hydraulic pump and a plurality of valves for controlling magnitude and direction of the pressure delivered to the clutches. The plurality of valves includes a modulation valve. The modulation valve is configured to allow modulation of time required for engagement of the wet clutches. The modulation valve comprises a piston with a first orifice, wherein the first orifice is always in fluid communication with the reservoir. The modulation valve also comprises a second orifice in parallel to the first orifice. The transmission system comprises a switching valve for opening and closing the second orifice, for changing the desired modulation time.
The plurality of valves also includes a priority valve, an inching valve, a direction control valve and a relief valve. The priority valve is configured to allow a fixed flow rate of the hydraulic fluid through the transmission system irrespective of the input flow rate and provide the rest of the fluid to flow for lubrication of the clutches. The inching valve is configured to enable disengagement of the clutches during gear shifting or to enable partial engagement of the clutch corresponding to the desired direction of movement to facilitate control slow movement of the vehicle. The direction control valve is configured to facilitate selection of one of the wet clutches to be engaged based on operator’s input. The relief valve is configured to facilitate relieving of hydraulic back pressure exerted on said system.
In an embodiment, the transmission system comprises an electrical switch coupled to the switching valve for facilitating manual switching of the switching valve. Preferably, the electrical switch is an ON/OFF switch. In an ON state, the switch switches the switching valve to open the second orifice.
Typically, the transmission system comprises a hand-operated power shuttle lever for facilitating operation of the direction control valve. In an embodiment, the switch is mounted on the power shuttle lever.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
A power shuttle transmission system of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a schematic diagram of a power shuttle transmission system of a prior art;
Figure 2 illustrates a plot of pressure rise versus time in the system of Figure 1;
Figure 3 illustrates a schematic diagram of a power shuttle transmission system according to an embodiment of the present disclosure;
Figure 4 illustrates a plot of pressure rise versus time in the system of Figure 3;
Figure 5a illustrates a side view of a subassembly of a modulation valve and a switching valve of the present disclosure;
Figure 5b shows section A-A of Figure 5a;
Figure 5c shows section B-B of Figure 5a;
Figure 6 illustrates an exploded view of the subassembly of Figure 5a;
Figure 7a shows another side view of the subassembly of Figure 5a;
Figure 7b shows section G-G of Figure 7a;
Figure 8a shows a top view of the subassembly of Figure 5a;
Figure 8b shows section H-H of Figure 8a; and
Figure 9 shows a bottom view of the subassembly of Figure 5a.
LIST OF REFERENCE NUMERALS
10a forward clutch
10b reverse clutch
20 hydraulic circuit
21 priority valve
22 inching valve
23 direction control valve
24 relief valve
25 modulation valve
251 modulation valve housing
252 modulation valve oil gallery
253 modulation valve piston cavity
254 second orifice
255 Allen screw
256 plug
26 switching valve
27 hydraulic pump
28 reservoir
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises”, “comprising”, “including” and “having” are open-ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof.
When an element is referred to as being “mounted on”, “engaged to”, “connected to” or “coupled to” another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.
Terms such as “inner”, “outer”, “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
A conventional power shuttle transmission system 1000’, shown in Figure 1, comprises a modulation valve 25’ for modulating the response time of the transmission system, by facilitating limiting of the maximum hydraulic pressure delivered therethrough. The arrows in Figure 1 indicate the direction of flow of hydraulic fluid through the system, wherein the continuous arrows denote pressurized flow, whereas the dashed arrows denote tank line flow or leakage flow. Figure 2 shows the plot ‘a’ of the modulation time achieved in the conventional power shuttle transmission system using the conventional modulation valve 25’. Different pressure modulation times are desired during forward/reverse shuttling operation and during clutch pedal operation for clutch engagement/disengagement during gear shifting. The piston of the conventional modulation valve 25’ of a conventional power shuttle transmission system 1000’ has a single orifice for allowing flow of pressurized fluid therethrough. The present disclosure seeks to provide a modulation valve which allows selection of different modulation times for different operations, i.e., forward/reverse shuttling and clutch pedal operation during gear shifting.
The power shuttle transmission system 1000 of a vehicle, of the present disclosure, is illustrated by the schematic diagram of Figure 3. The power shuttle transmission system 1000 comprises a forward clutch 10a and a reverse clutch 10b configured to be engaged for propelling the vehicle in a forward direction and in a reverse direction respectively, and to be disengaged during gear shifting. The clutches 10a, 10b are actuated by a hydraulic circuit comprising a reservoir 28, a hydraulic pump 27 and a plurality of valves for controlling the magnitude and the direction of the pressure delivered to the clutches 10a, 10b. The plurality of valves includes a priority valve 21, an inching valve 22, a direction control valve 23, a relief valve 24 and a modulation valve 25.
The priority valve 21 is configured to allow a fixed flow rate of hydraulic fluid through the transmission system 1000 irrespective of the input flow rate and provide the rest of the fluid to flow for lubrication of the clutches 10a, 10b. The inching valve 22 is configured to enable disengagement of the clutches 10a, 10b during gear shifting and also facilitate control slow movement of the vehicle by partially engaging the clutch corresponding to the desired direction of movement. The direction control valve 23 is configured to facilitate selection of one of the wet clutches 10a, 10b to be engaged based on operator’s input. The relief valve 24 facilitates relieving of hydraulic back pressure exerted on the priority valve 21. The modulation valve 25 is configured to allow modulation of time required for engagement of the wet clutches 10a, 10b.
The modulation valve 25 of the present disclosure comprises a first orifice (not shown) and a second orifice 254. The first orifice is configured on the piston (not shown) of the modulation valve 25. The first orifice is always in fluid communication with the reservoir 28. The second orifice 254 is configured in parallel to the first orifice.
The system comprises a switching valve 26 for opening and closing the second orifice 254, for changing the desired modulation time. The modulation time achieved by closing the second orifice 254 is represented by the curve ‘b’, as illustrated in the plot of Figure 4. When opened, the second orifice 254 allows additional mass of the hydraulic fluid to flow, simultaneously with the first orifice, so that the rate of pressure rise increases, thereby decreasing the modulation time, represented by the curve ‘c’ of Figure 4.
In an embodiment, the switching valve 26 is a solenoid valve. For facilitating manual switching of the switching valve 26, an electrical switch is provided. Preferably, the electrical switch for operating the switching valve 26 is mounted on the power shuttle lever that is operated for operating the direction control valve 23 for forward/reverse shuttling. In an embodiment, the electrical switch for operating the switching valve is an ON/OFF switch. In an ON state, the switch is switched in a state that corresponds to forward/reverse shuttling, thus providing a longer modulation time, while, in an OFF state, the switch is switched in a state that corresponds to gear shifting or to inching of the vehicle, thus providing a shorter modulation time.
The construction of the modulation valve 25 according to an embodiment of the present disclosure is illustrated through Figures 5-9.
The modulation valve 25 has a modulation valve housing 251 in which oil galleries 252 and a piston cavity 253 are defined. The piston cavity 253 receives the piston of the modulation valve 25, wherein the piston has the first orifice. The second orifice 254 is provided in the modulation valve housing 251 in parallel to the first orifice. The modulation valve housing 251 receives the switching valve 26 of the present disclosure. The modulation valve housing 251 of the modulation valve 25 is configured to be fitted to the main hydraulic block (not shown) of the power shuttle transmission system using Allen screws 255. Further, plugs 256 are provided for plugging open ports of the oil galleries 252.
In the working of a preferred embodiment of the power shuttle transmission system 1000 of the present disclosure, the vehicle’s operator performs forward/reverse shuttling by retaining the switching valve in a first state, by retaining the electrical switch available on the hand-operated power shuttle lever in the default ON state. A relatively longer modulation time of the clutches 10a, 10b is available in this mode. Thus, the system 1000 provides a slower response and hence a jerk-free forward/reverse shuttling operation. While performing a gear shifting operation, the vehicle operator switches the electrical switch in an OFF state to switch the switching valve in a second state, which causes the transmission system to have a shorter modulation time. Thus, the transmission system 1000 provides a quick response for clutch operation during gear shifting by fully disengaging the clutch or during inching of vehicle using a partially disengaged clutch. In other words, there is no undesirable lag between clutch pedal release and vehicle movement. Hence, the transmission system 1000 improves satisfaction of the operator.
In another embodiment, the electrical switch for the switching valve 26 is implemented in the form of a gear shifting lever operation sensor or a clutch pedal depression sensor, wherein on receiving a signal corresponding to gear shifting lever operation or clutch pedal depression, the switching valve would provide the transmission a shorter modulation time. In yet another embodiment, the electrical switch is implemented in the form of a sensor which senses a neutral position of the power shuttle lever.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a power shuttle transmission system for a vehicle, which:
• has reduced response time during gear shifting or during inching;
• provides a jerk-free F/R shuttling operation;
• improves operator’s satisfaction; and
• is easy to operate.
The foregoing disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, but not the exclusion of any other element, integer or step, or group of elements.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation