DESC:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“AN APPARATUS FOR PRESSURE MODULATION IN A HYDRAULIC SYSTEM OF A VEHICLE”

APPLICANT:

Name Nationality Address
Mahindra & Mahindra Limited Indian Mahindra & Mahindra Ltd.,
MRV, Mahindra World City,
Anjur Post, Chengalpattu,
Kanchipuram District – 603204 (TN) INDIA

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

TECHNICAL FIELD
[001] The embodiments herein generally relate to control systems in vehicles and more particularly, but not exclusively to a pressure modulation system for controlling clutches of a power shuttle transmission system and the like in vehicles.

BACKGROUND
[002] Generally, power shuttle transmission systems are used in vehicles such as tractors or other similar vehicles for instant forward to reverse and/or reverse to forward direction operation at the same speed by engaging a lever or a button and thereby eliminating the need for using a clutch pedal to enable gear shifting. The power shuttle transmission system is controlled by a power shuttle transmission (hereinafter “PST”) valve (valve block) that is mounted thereof to govern gear shifting. The function of the PST valve (valve block) is to gradually engage and/or disengage at least one clutch by regulating an oil pressure in a clutch pack of at least one clutch so as to enable smooth gear shifting in vehicles. This pressure regulation is known as pressure modulation. The PST valve includes a pressure modulation valve to gradually increase the oil pressure in the clutch pack for gradual engagement and /or disengagement of at least one clutch and thereby gear shifting is done with less jerk and lag.
[003] A conventional pressure modulation valve of a PST valve, as shown in Figs. 1, 2a and 2b, includes a relief piston, springs and a modulation piston. The working of the pressure modulation valve is quite similar to a relief valve (i.e. the pressure is relieved as it exceeds the preset pressure). The relief pressure at relief piston 1 is gradually increased by increasing spring force on relief piston 1, which is dependent on the spring stiffness. Further, the relief piston 1 and the modulation piston 2 are connected through an orifice, to ensure restricted oil flow there through. The oil restriction causes a lag between pressure at relief piston 1 and modulation piston 2 till the modulation piston 2 is fully compressed and then equalizes. The modulation piston 2 presses the springs toward the relief piston 1, thus increasing force on relief piston 1.
[004] Thus the orifice and spring combinations govern the modulation time and curve. As is apparent from fig 2b, the pressure modulation is a 2 stage pressure modulation. Therefore, the gear shifting happens with some jerk and lag and is not smooth.
[005] Therefore, there exists a need for an effective pressure modulation system in a vehicle that obviates the aforementioned drawbacks of the conventional pressure modulation systems.

OBJECTS
[006] The principal object of an embodiment of this invention is to provide an apparatus facilitating an effective pressure modulation in a hydraulic system for controlling clutches of a power shuttle transmission system and the like in vehicles for smooth gear shifting without lag.
[007] Another object of an embodiment of this invention is to provide the apparatus for gradual engagement and/or disengagement of at least one clutch of the power shuttle transmission system for smooth gear shifting without lag.
[008] The objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS
[009] The embodiments of this invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0010] FIG. 1 depicts a cross-sectional view of a conventional PST valve;
[0011] FIG. 2a depicts a cross-sectional view of a pressure modulation valve of the conventional PST valve;
[0012] FIG. 2b depicts a graph showing pressure versus time of the conventional PST valve;
[0013] FIG. 3 depicts a cross-sectional view of an apparatus for pressure modulation in a hydraulic system of a vehicle, according to an embodiment of the invention as disclosed herein;
[0014] FIG. 4 depicts a hydraulic circuit diagram of a control valve, the apparatus of a power shuttle transmission valve block and a plurality of clutches of a power shuttle transmission system, according to an embodiment of the invention as disclosed herein; and
[0015] FIG. 5 depicts a graph showing pressure versus time of the apparatus of FIG. 3, according to an embodiment of the invention as disclosed herein.

DETAILED DESCRIPTION
[0016] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed 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.
[0017] The embodiments herein achieve an apparatus facilitating an effective pressure modulation in a hydraulic system for controlling clutches of a power shuttle transmission system and the like in vehicles for smooth gear shifting without lag. Referring now to the drawings and more particularly to FIG. 3 through 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0018] For the purpose of this description and ease of understanding, the apparatus 100 (as shown in fig. 3) explained herein is configured to provided in a power shuttle transmission valve block (not shown) that is mounted to a power shuttle transmission system (not shown) of a vehicle i.e., in general terms the apparatus 100 is configured to be provided to a valve block that is mounted to the power shuttle transmission system of the vehicle. However, it is also within the scope of the invention to use the apparatus 100 in a power shift transmission system or any other transmission systems in vehicles without otherwise deterring the intended function of the apparatus 100 as can be deduced from the description. Furthermore, it is also within the scope of the invention to use the apparatus 100 in rail vehicles, shunt locomotives, ski-lifts, any other hydraulic clutch applications or any other hydraulic systems provided for any systems or machines without otherwise deterring the intended function of the apparatus 100 as can be deduced from the description. In an embodiment, the vehicle (not shown) includes a hydraulic system (not shown) and a power shuttle transmission system (not shown).
[0019] The hydraulic system (not shown) is used to control the power shuttle transmission system (not shown) and may also have other standard functions of the standard hydraulic systems in vehicles. In an embodiment, the hydraulic system (not shown) includes a valve block (not shown), fluid supply system (not shown), at least one tank T and may also include other standard units or components of the standard hydraulic system in vehicles. The valve block (not shown) includes at least one housing (not shown), at least one control valve V, an apparatus 100 and may also include other standard valves or other components of a standard power shuttle transmission valve block in vehicles. The housing (not shown) is used to enclose and protect the apparatus 100, at least one control valve V and other standard valves or any other components of the standard power shuttle transmission valve block. The housing (not shown) includes at least one inlet (not shown), at least one outlet (not shown), at least one chamber H, at least one orifice (not shown), a plurality of channels (not shown) and other standard valves or components of the standard power shuttle transmission valve block. The inlet (not shown) of the housing (not shown) facilitates entry of a fluid into the housing (not shown) from the fluid supply system (not shown). The outlet (not shown) of the housing (not shown) facilitates exit of the fluid from the housing (not shown) of the valve block (not shown). The chamber H serves as a working chamber for the apparatus 100. The orifice (not shown) is used to facilitate fluid communication in the housing (not shown). The plurality of channels (not shown) is used to facilitate fluid communication between the at least one orifice (not shown), apparatus 100 and at least one control valve V. In an embodiment, the fluid is at least oil. However, it is also within the scope of the invention to provide the valve block (not shown) with air or any other fluid without otherwise deterring the intended function of the fluid in the valve block (not shown) as can be deduced from the description. The control valve V is provided in fluid communication with the apparatus 100. The control valve V is used to control or regulate the flow or direction flow to the power shuttle transmission system (not shown). The fluid supply system (not shown) is used to supply the fluid to the apparatus 100 and other components in the hydraulic system (not shown). The tank T is used to collect or store the excess fluid. The power shuttle transmission system (not shown) includes at least one forward clutch F, at least one reverse clutch R and includes other standard components or units of a standard power shuttle transmission system. The power shuttle transmission system (not shown) is used to enable the vehicle (not shown) for instant forward to reverse and/or reverse to forward direction operation at the same speed by engaging a lever (not shown) or a button (not shown).
[0020] FIG. 3 depicts a cross-sectional view of an apparatus 100 for pressure modulation in a hydraulic system of a vehicle, according to an embodiment of the invention as disclosed herein. The apparatus 100 is used to gradually engage and/or disengage at least one forward clutch F and/or at least one reverse clutch R of the power shuttle transmission system (not shown) for enabling smooth gear shifting due to pressure modulation of a fluid that is provided to at least one forward clutch F and/or at least one reverse clutch R thereof. In an embodiment, the apparatus 100 is configured to be provided in the valve block (not shown) mounted to the power shuttle transmission system (not shown). However it is also within the scope of the invention to provide the apparatus 100 as a separate part enclosed in a separate housing and is provide in fluid communication with the valve block (not shown) mounted to the power shuttle transmission system (not shown) without otherwise deterring the intended function of the apparatus 100 as can be deduced from the description. In an embodiment, the apparatus 100 includes a first movable member 102, a second movable member 104, a shaft 106, a first resilient means 108, a second resilient means 110 and a third resilient means 112.
[0021] In an embodiment, the first movable member 102 is configured to receive the first resilient means 108 i.e., the first movable member 102 includes an opening (not shown) for receiving the first resilient means 108. The first movable member 102 is configured to be provided in engagement with the fluid from the fluid supply system (not shown) of the hydraulic system (not shown). In an embodiment, an outer diameter of the first movable member 102 is smaller than an outer diameter of the second movable member 104. However, it is also within the scope of the invention to provide the outer diameter of the first movable member 102 equal to or bigger than the outer diameter of the second movable member 104 without otherwise deterring the intended function of the first movable member 102 and the second movable member 104 as can be deduced from the description. Further, in an embodiment, the first movable member 102 is configured to move to drain a fluid to a tank T (as shown in fig. 4) when the pressure is at least 20bar. The first movable member 102 is configured to have a preset pressure value of maximum 20bar. However, it is also within the scope of the invention to configure the first movable member 102 to move to drain the fluid to the tank T when the pressure is between 1 to 20 bar or any other pressure range without otherwise deterring the intended function of the first movable member 102 as can be deduced from the description. Further, it is also within the scope of the invention to provide the apparatus 100 with any other means instead of the first movable member 102 without otherwise deterring the intended function of the first movable member 102 as can be deduced from the description. Furthermore, in an embodiment, the first movable member 102 has circular cross-section. However, it is also within the scope of the invention to provide the first movable member 102 in rectangular cross-section or any other cross-section without otherwise deterring the intended function of the first movable member 102 as can be deduced from the description.
[0022] In an embodiment, the second movable member 104 is configured to receive the first resilient means 108 and also to engage the second resilient means 110 i.e., the second movable member 104 includes an opening (not shown) for receiving the first resilient means 108 and also to engage the second resilient means 110. The second movable member 104 is configured to be provided in engagement with the fluid during operation. In an embodiment, the second movable member 104 is configured to move between a first position and a second position on engagement of the fluid thereof i.e., the second movable member 104 is configured to move between the first position and the second position for compressing the first resilient means 108 and then the third resilient means 112 and thereafter the second resilient means 110 on engagement of the fluid from the fluid supply system (not shown) and thereby resulting in regulating the pressure of the fluid in three stages (gradual rise in fluid pressure) for gradual engagement and/or dis-engagement of at least one forward clutch F and/or at least one reverse clutch R of the power shuttle transmission system (not shown) for smooth gear shifting of the vehicle (not shown). However, it is also within the scope of the invention to provide the apparatus 100 with any other means instead of the second movable member 104 without otherwise deterring the intended function of the second movable member 104 as can be deduced from the description. Further, in an embodiment, the second movable member 104 has circular cross-section. However, it is also within the scope of the invention to provide the second movable member 104 in rectangular cross-section or any other cross-section without otherwise deterring the intended function of the second movable member 104 as can be deduced from the description.
[0023] The shaft 106 is used to engage or hold the second resilient means 110 and the third resilient means 112. In an embodiment, the shaft 106 includes a first end 106a, a second end 106b and a portion 106c between the first end 106a and the second end 106b. In an embodiment, a diameter of the second end 106b is smaller than a diameter of the first end 106a of the shaft 106. However, it is also within the scope of the invention to provide the diameter of the second end 106b equal to the diameter of the first end 106a of the shaft 106 without otherwise deterring the intended function of the first end 106a and the second end 106b of the shaft 106 as can be deduced from the description. Further, in an embodiment, the portion 106c of the shaft 106 is used to engage the second resilient means 110 and also to engage the third resilient means 112. However, it is also within the scope of the invention to provide the apparatus 100 with any other means instead of the shaft 106 without otherwise deterring the intended function of the shaft 106 as can be deduced from the description. Furthermore, in an embodiment, the shaft 106 has circular cross-section. However, it is also within the scope of the invention to provide the shaft 106 in rectangular cross-section or any other cross-section without otherwise deterring the intended function of the shaft 106 as can be deduced from the description.
[0024] The first resilient means 108 is configured to compress on engagement of the second movable member 104 for generating pressure as zone 1 in pressure modulation curve as shown in fig. 5. In an embodiment, the first resilient means 108 includes a first end 108a and a second end 108b. The first end 108a of the first resilient means 108 is received by the first movable member 102. The second end 108b of the first resilient means 108 is received by the second movable member 104. The first resilient means 108 is configured to compress on engagement or movement of the second movable member 104. In an embodiment, the first resilient means 108 is at least of a spring and the like. However, it is also within the scope of the invention to provide the apparatus 100 with any other means instead of the first resilient means 108 without otherwise deterring the intended function of the first resilient means 108 as can be deduced from the description.
[0025] The second resilient means 110 is configured to compress on engagement of the second movable member 104 for generating pressure as zone 2 in pressure modulation curve as shown in fig. 5. In an embodiment, the second resilient means 110 includes a first end 110a and a second end 110b. The first end 110a of the second resilient means 110 is engaged to the portion 106c of the shaft 106. The second end 110b of the second resilient means 110 is engaged to the second movable member 104. The second resilient means 110 is configured to compress on engagement or movement of the second movable member 104. In an embodiment, the second resilient means 110 is at least one of a spring and the like. However, it is also within the scope of the invention to provide the apparatus 110 with any other means instead of the second resilient means 110 without otherwise deterring the intended function of the second resilient means 110 as can be deduced from the description. Further, in an embodiment, an inner diameter of the second resilient means 110 is smaller than an inner diameter of the third resilient means 112. However, it is also within the scope of the invention to provide the inner diameter of the second resilient means 110 equal to the inner diameter of the third resilient means 112 without otherwise deterring the intended function of the second resilient means 110 and the third resilient means 112 as can be deduced from the description. Furthermore, in an embodiment, an outer diameter of the second resilient means 110 is smaller than an inner diameter of the first resilient means 108.
[0026] The third resilient means 112 is configured to compress on engagement of the second movable member 104 for generating pressure as zone 3 in pressure modulation curve as shown in fig. 5. In an embodiment, the third resilient means 112 includes a first end 112a and a second end 112b. The first end 112a of the third resilient means 112 is operatively engaged to the first movable member 102. The second end 112b of the third resilient means 112 is engaged to the portion 106c of the shaft 106. The third resilient means 112 is configured to compress on engagement or movement of the second movable member 104. In an embodiment, the third resilient means 112 is at least one of a spring and the like. However, it is also within the scope of the invention to provide the apparatus 100 with any other means instead of the third resilient means 112 without otherwise deterring the intended function of the third resilient means 112 as can be deduced from the description. In an embodiment, a longitudinal axis of the third resilient means 112 is substantially concentric to a longitudinal axis of the second resilient means 110. Further, in an embodiment, the third resilient means 112, the second resilient means 110 and the first resilient means 108 are substantially concentric to each other. Furthermore, in an embodiment, an outer diameter of the third resilient means 112 is smaller than an outer diameter of the second resilient means 110.
[0027] The working of the apparatus 100 is as follows. Initially fluid from the fluid supply system (not system) is provided to at least one forward clutch F and/or at least one reverse clutch R of the power shuttle transmission system (not shown) through the control valve V of the valve block (not shown). During engagement of a lever or a button (not shown) of the power shuttle transmission system (not shown), the apparatus 100 starts working such that the fluid from the fluid supply system (not shown) is supplied to valve block (not shown) of the hydraulic system (not shown) to provide engagement of the fluid with the first movable member 102 and simultaneously the fluid also engages the second movable member 104 through an orifice (not shown) and the fluid pushes the second movable member 104 against the force created by inlet flow and spring force. The movement of the second movable member 104 causes compression of the first resilient means 108 and pressure starts developing at the chamber H as zone1 shown in graph of Fig. 5. Further, movement of the second movable member 104 causes compression of third resilient means 112 against the first movable member 102 and pressure again starts building up as zone 2 shown in graph of fig. 5. Further, the second movable member 104 again moves to compress the second resilient means 110 till the equilibrium condition reaches by pressure in the inlet flow pressure and pilot line pressure and give final zone3 as shown in graph of fig. 5. When the equilibrium condition has been reached, pressure will be maintained at 20bar for the first movable member 102 to move for draining the remaining oil to tank T. Thus the pressure starts developing gradually in three stages with the help of first resilient means 108, the second resilient means 110 and the third resilient means 112 with different stiffness and the pressure modulated fluid is provided to at least one forward clutch F and/or at least one reverse clutch R of the power shuttle transmission system (not shown) through the control valve V for gradual engagement and/or dis-engagement of at least one forward clutch F and/or at least one reverse clutch R of the power shuttle transmission system (not shown) to enable smooth gear shifting of the vehicle (not shown).
[0028] FIG. 5 depicts a graph showing pressure versus time of the apparatus 100 of FIG. 3, according to an embodiment of the invention as disclosed herein. The pressure produced by the apparatus 100 was found to be around 23bar and the corresponding time taken was 2.1 seconds. Thus from FIG. 5 (based on the value of pressure and corresponding time) it is clearly evident that the apparatus 100 regulates the pressure of the fluid (pressure of the fluid rises gradually) in three stages for gradual engagement and/or dis-engagement of at least one forward clutch F and/or at least one reverse clutch R of the power shuttle transmission system (not shown) and thereby resulting in smooth gear shifting.
[0029] The foregoing description of the specific embodiments will 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.

CLAIMS
We claim,
1. An apparatus for pressure modulation in a hydraulic system of a vehicle, said apparatus comprising:
a first movable member;
a second movable member;
a shaft having a first end, a second end and a portion between the first end and the second end;
a first resilient means having a first end received by the first movable member and a second end received by the second movable member;
a second resilient means having a first end engaged to the portion of the shaft and a second end engaged to the second movable member; and
a third resilient means having a first end operatively engaged to the first movable member and a second end engaged to the portion of the shaft,
wherein
the second movable member is configured to move between a first position and a second position on engagement of a fluid thereof.
2. The apparatus as claimed in claim 1, wherein the first resilient means is at least a spring.
3. The apparatus as claimed in claim 1, wherein the second resilient means is at least a spring.
4. The apparatus as claimed in claim 1, wherein the third resilient means is at least a spring.
5. The apparatus as claimed in claim 1, wherein an inner diameter of the second resilient means is smaller than an inner diameter of the third resilient means.
6. The apparatus as claimed in claim 1, wherein an outer diameter of the second resilient means is smaller than an inner diameter of the first resilient means.
7. The apparatus as claimed in claim 1, wherein the first resilient means, the second resilient means and the third resilient means are substantially concentric to each other.
8. The apparatus as claimed in claim 1, wherein the first movable member is configured to move to drain the fluid to a tank when the pressure is at least 20bar.
9. The apparatus as claimed in claim 1, wherein an outer diameter of the first movable member is smaller than an outer diameter of the second movable member.

10. The apparatus as claimed in claim 1 is configured to be provided to a power shuttle transmission valve block.

Dated 27th May 2016 Signature:
Name: Dr.Kalyan Chakravarthy
ABSTRACT
An apparatus for pressure modulation in a hydraulic system of a vehicle includes a first movable member, a second movable member, a shaft, a first resilient means, a second resilient means and a third resilient means. The second movable member is configured to move between a first position and a second position for compressing the first resilient means and then the third resilient means and thereafter the second resilient means on engagement of a fluid thereof and thereby resulting in regulating the pressure of the fluid in three stages for gradual engagement and/or dis-engagement of at least one clutch of a power shuttle transmission system for smooth gear shifting of the vehicle.
Fig. 3

,CLAIMS:CLAIMS
We claim,
1. An apparatus for pressure modulation in a hydraulic system of a vehicle, said apparatus comprising:
a first movable member;
a second movable member;
a shaft having a first end, a second end and a portion between the first end and the second end;
a first resilient means having a first end received by the first movable member and a second end received by the second movable member;
a second resilient means having a first end engaged to the portion of the shaft and a second end engaged to the second movable member; and
a third resilient means having a first end operatively engaged to the first movable member and a second end engaged to the portion of the shaft,
wherein
the second movable member is configured to move between a first position and a second position on engagement of a fluid thereof.
2. The apparatus as claimed in claim 1, wherein the first resilient means is at least a spring.
3. The apparatus as claimed in claim 1, wherein the second resilient means is at least a spring.
4. The apparatus as claimed in claim 1, wherein the third resilient means is at least a spring.
5. The apparatus as claimed in claim 1, wherein an inner diameter of the second resilient means is smaller than an inner diameter of the third resilient means.
6. The apparatus as claimed in claim 1, wherein an outer diameter of the second resilient means is smaller than an inner diameter of the first resilient means.
7. The apparatus as claimed in claim 1, wherein the first resilient means, the second resilient means and the third resilient means are substantially concentric to each other.
8. The apparatus as claimed in claim 1, wherein the first movable member is configured to move to drain the fluid to a tank when the pressure is at least 20bar.
9. The apparatus as claimed in claim 1, wherein an outer diameter of the first movable member is smaller than an outer diameter of the second movable member.

10. The apparatus as claimed in claim 1 is configured to be provided to a power shuttle transmission valve block.