GB2572777A

GB2572777A - Energy storage system for powertrains of machines

Info

Publication number: GB2572777A
Application number: GB1805909.7A
Authority: GB
Inventors: Earl Jacobson Evan
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2018-04-10
Filing date: 2018-04-10
Publication date: 2019-10-16
Also published as: GB201805909D0

Abstract

A powertrain system 170 for a machine includes a transmission unit 178 that varies speed of the machine in discrete steps, and a differential unit 182 that receives the transmission unit's rotary power. Further, a flywheel 222 is coupled with the differential unit, a planetary gear assembly 220 transfers power between the differential unit and the flywheel, and a clutch 226 selectively transfers power between the flywheel and the differential unit through the planetary gear assembly. A motor 224 selectively powers a rotation of the flywheel. Moreover, a controller 300 detects a predetermined discrete step, controls the clutch to disable a power transfer between the differential unit and the flywheel based on the predetermined discrete step, activates the motor to rotate the flywheel up to a speed, and controls the clutch to enable a power transfer from the flywheel to the differential unit, during a shift from the predetermined discrete step to a succeeding discrete step. This ensures that torque continues to be transmitted to the differential (and thus the rear wheels) during gear changes, thereby avoiding torque holes and allowing the machine to maintain a constant speed. This may be especially useful for grader machines.

Description

ENERGY STORAGE SYSTEM FOR POWERTRAINS OF MACHINES

Technical Field [0001] The present disclosure generally relates to an energy storage system for a powertrain of a machine. More particularly, the disclosure relates to an energy storage system that facilitates an uninterrupted movement of a machine during transmission shift events in the machine.

Background [0002] Machines, such as construction machines, with discrete ratio transmission systems may experience a drop in the machine’s propulsion force during transmission shift events. Such conditions (also referred to as torque holes) may lead to an interruption in an otherwise steady movement of the machine, and may in turn affect an operation that the machine is associated with. For example, an interruption during a grading operation may lead to an uneven spread, levelling, and distribution of materials, over a work surface. Further, torque holes also make it difficult for machines, such as grader machines, to accommodate varying load conditions of a work surface. Moreover, condition of torque holes may be exaggerated in machines that require stationary members of transmission units to rapidly accelerate during transmission shift events. Such rapid acceleration events may draw a relatively significant portion of the engine’s power, leaving relatively less power to pass through the machine’s transmission system to maintain propulsion.

[0003] United States Patent No. 9,718,343 relates to an apparatus comprising a flywheel for storing kinetic energy and an electrical machine mechanically coupled to the flywheel and arranged for conversion between mechanical and electrical energy. The apparatus is arranged for transferring energy between the flywheel and a vehicle transmission via a variable ratio transmission. The electrical machine is coupled to the flywheel via a disconnect clutch which comprises a magnetic coupling.

-2Summary of the Invention [0004] In one aspect, the disclosure is directed towards a powertrain system for a machine. The powertrain system includes a transmission unit that varies a speed of the machine in discrete steps, and a differential unit that receives rotary power from the transmission unit. Further, the powertrain system includes a flywheel selectively coupled with the differential unit, a planetary gear assembly configured to facilitate a transfer of power between the differential unit and the flywheel, a clutch to selectively engage the flywheel with the differential unit to enable a selective transfer of power between the flywheel and the differential unit through the planetary gear assembly, a motor to selectively power a rotation of the flywheel, and a controller. The controller is configured to detect a predetermined discrete step, control the clutch to disable a power transfer between the differential unit and the flywheel based on the predetermined discrete step, activate the motor to rotate the flywheel up to a speed to generate supplementary kinetic energy at the flywheel, and control the clutch to enable a power transfer from the flywheel to the differential unit. A power transfer from the flywheel to the differential unit facilitates transfer of the supplementary kinetic energy from the flywheel to the differential unit during a shift from the predetermined discrete step to a succeeding discrete step.

Brief Description of the Drawings [0005] FIG. 1 is an exemplary construction machine, in accordance with an embodiment of the present disclosure;

[0006] FIG. 2 is a schematic layout of a powertrain system of the machine that includes a powertrain and an energy storage system for the powertrain, in accordance with an embodiment of the present disclosure; and [0007] FIG. 3 in an enlarged, detailed view of the energy storage system of FIG. 2, in accordance with an embodiment of the present disclosure.

-3Detailed Description [0008] Referring to FIG. 1, a machine 100 is shown, and as depicted, is a motor grader 102. The machine 100 may be used to displace, spread, distribute, level, and grade materials 106, such as soil, over a work surface 110. Generally, a grading operation is performed during machine movement, and for this purpose, the machine 100 may include traction devices 114 that facilitate movement of the machine 100 over the work surface 110. For example, the traction devices 114 may include a set of front wheels 118 disposed towards a front end 120 of the machine 100 and a set of rear wheels 122 disposed towards a rear end 124 of the machine 100. The terms ‘front’ and ‘rear’, as used herein, are in relation to a direction of travel of the machine 100, as represented by arrow, T, in FIG. 1, with said direction of travel being exemplarily defined from the rear end 124 towards the front end 120. Further, the machine 100 may include a frame 130, and an operator cab 132 that houses controls associated with a power source (discussed later) and various implements of the machine 100, supported on the frame 130. Although the machine 100 is exemplarily noted to embody the motor grader 102, it is possible for various other machines, such as scrapers, loaders, excavators, and mining trucks, to make use of one or more aspects of the present disclosure.

[0009] To grade and level materials over the work surface 110, the machine 100 may include a drawbar-circle-blade (DCB) arrangement - also referred to as a grader group 140. The grader group 140 may be supported by the frame 130. The grader group 140 may include a drawbar 142, a circle assembly 144, and a blade assembly 146, each of which may function in concert to perform a grading operation on the work surface 110.

[0010] Referring to FIGS. 1 and 2, the set of front wheels 118 may be further categorized into a left front wheel 150 and a right front wheel (hidden behind the left front wheel 150 in FIG. 1). Similarly, the set of rear wheels 122 may be further categorized into left rear wheels 156 and right rear wheels 158 (see FIG. 2). A movement (i.e., a rotation) of the set of rear wheels 122 may be facilitated by a powertrain system 170 (see FIG. 2) of the machine 100. A movement of the set of

-4rear wheels 122 may facilitate a propulsion of the machine 100 over the work surface 110.

[0011] Referring to FIGS. 1 and 2, the powertrain system 170 is discussed in further detail. As shown, the powertrain system 170 includes a powertrain 174 that includes a power source 176, a transmission unit 178, a driveshaft 180, a differential unit 182, and an axle unit 184. Further, the powertrain system 170 also includes an energy storage system 190 details of which are depicted in FIGS. 2 and 3, but will be discussed later.

[0012] The power source 176 may include an engine 192, which may be housed in a power compartment 194 (see FIG. 1) of the machine 100. The engine 192 may be applied to power a working of the powertrain 174 and facilitate machine propulsion. The engine 192 may power various other operational requirements of the machine 100, as well. In one example, the engine 192 may be an internal combustion engine of a reciprocating type that generates rotary power, and may be functionally implemented as one of a diesel engine, a gasoline engine, a natural gas engine, a dual fuel engine, and/or may correspond to any engine type available in the art. It is also possible to incorporate various other types of power units, such electrically operated power units, either singularly, or in combination with the power source 176, to facilitate machine propulsion.

[0013] The transmission unit 178 may convert speed/torque characteristics of the power source 176, so as to facilitate a controlled transfer and application of power to the traction devices 114. More particularly, the transmission unit 178 may be operated across discrete gear ratios, and in turn may vary a speed of the machine 100 in discrete steps. For example, the transmission unit 178 may facilitate a shift between a higher gear (that is, a gear with a lower gear ratio) and a lower gear (that is, a gear with a higher gear ratio) to facilitate the controlled transfer and application of power. Such a shift may be enabled either automatically or manually. As an example, the transmission unit 178 provides 5 discrete gear ratios.

-5[0014] The driveshaft 180 may be coupled between the transmission unit 178 and the differential unit 182, and may facilitate a transfer of rotary power (arrow, A, FIG. 3) gained from the transmission unit 178 to the differential unit 182. For example, the driveshaft 180 may include (or be coupled to) a bevel pinion 196 at one end 198, and the bevel pinion 196 may be extended into the differential unit 182 and be engaged with a crown gear 200 of the differential unit 182, as shown. Rotational energy derived from the transmission unit 178 may be transferred to the crown gear 200, so as to rotate the crown gear 200.

[0015] The differential unit 182 may be configured to split torque of the rotary power received from the transmission unit 178 equally between the left rear wheels 156 and the right rear wheels 158 of the machine 100. To this end, the differential unit 182 may include a conventional arrangement of gears and various moving parts (including the crown gear 200) that in concert facilitate the transmission of the equal torque to the left rear wheels 156 and to the right rear wheels 158 through respectively arranged transfer chain casings 202, as shown. The conventional arrangement of gears and various moving parts of the differential unit 182 may be enclosed within a housing 206 of the differential unit 182. Elaborate details and annotations pertaining to the differential unit 182 have not been provided for the sake of clarity.

[0016] Since the transmission unit 178 includes a discrete speed transmission pattern, every shift event from a lower gear ratio to a higher gear ratio (or, in some cases, from a higher gear ratio to a lower gear ratio) may correspondingly include a shift duration. In other words, a shift duration may be defined between a preceding discrete step and a succeeding discrete step of the transmission unit 178. During each shift duration (which may exemplarily range between 1.5 seconds to 2 seconds), a transmission of torque from the transmission unit 178 to the differential unit 182 is bound to be reduced to an extent to not just cause operator discomfort, but to also affect machine operation. Such conditions may be referred to as ‘torque holes’. In such cases, the energy storage system 190 provides supplementary power (or supplementary energy) to the powertrain 174 to drive the

-6set of rear wheels 122, and enables the set of rear wheels 122 to move (i.e., to rotate) at a steady, uninterrupted speed, during each shift duration. The energy storage system 190 includes a planetary gear assembly 220, a flywheel 222, a motor 224, a first clutch 226, and a second clutch 228.

[0017] Referring to FIGS. 2 and 3, the flywheel 222 is a mechanical energy storing device, or a mechanical battery that has an outer rim portion 230, and mass concentrated at the outer rim portion 230, as shown. The flywheel 222 may be selectively coupled with the differential unit 182 (i.e., to the crown gear 200). The flywheel 222 is designed to efficiently store rotational energy gained from the rotation of the crown gear 200, and is in turn able to resist changes in a rotational speed of the crown gear 200 (and in turn of the driveshaft 180 and the axle unit 184) because of its (i.e., the flywheel’s) moment of inertia. The flywheel 222 includes a shaft 242 (such as an integrally formed shaft) passing through a central portion of the flywheel 222, and which may be used to rotatably support the flywheel 222 to a sub-frame portion (not shown) of the machine 100. The flywheel 222 and the shaft 242 may together define a common axis of rotation 244 for the flywheel 222. In some embodiments, the axis of rotation 244 of the flywheel 222 may be aligned with an axis 240 of the driveshaft 180, and, thus, the flywheel 222 may be arranged substantially in line (or parallelly) with the driveshaft 180.

[0018] Referring to FIGS. 2 and 3, the planetary gear assembly 220 is arranged in between the flywheel 222 and the differential unit 182, and, in some cases, is configured to gather rotational energy from the rotation of the crown gear 200 (arrow, C, FIG. 3), and pass the rotational energy to the flywheel 222. Thus, the planetary gear assembly 220 is configured to facilitate a transfer of power between the differential unit 182 and the flywheel 222. In passage of the rotational energy to the flywheel 222, the planetary gear assembly 220 may alter the speed ratio, and may cause the flywheel 222 to rotate at a greater speed in comparison to the rotary speed gathered from the crown gear 200. In further detail, the planetary gear assembly 220 includes a bevel gear 250, a set of planet gears 252, a sun gear 254, and a ring gear 256.

-7[0019] The bevel gear 250 is meshed with the crown gear 200 of the differential unit 182 and is coupled to (or is integrally formed with) a carrier 260, as shown. The bevel gear 250 may be situated axially opposite to the bevel pinion 196, and may be symmetrically arranged relative to the bevel pinion 196, about the axle unit 184. The carrier 260 is in turn coupled to the set of planet gears 252, with each of the planet gears 252', 252 being able to rotate about their respective axes 262', 262 relative to the carrier 260. The planet gears 252', 252 are in turn meshed with the sun gear 254, and, thus, are moveable around the sun gear 254 while rotating about their respective axes 262', 262. It may be noted that the set of planet gears 252 are also in engagement with the ring gear 256, and thus each of the planet gears 252', 252 assume a position defined in between the sun gear 254 and the ring gear 256. In effect, the set of planet gears 252 may move relative to both the sun gear 254 and the ring gear 256, during operation. Further, the sun gear 254 is fixedly coupled to the shaft 242 extending from the flywheel 222, and thus the flywheel 222 is able to rotate synchronously with a movement imparted to the sun gear 254.

[0020] During operation, the ring gear 256 may be engaged with the differential unit 182 (such as to the housing 206 or to a fixed frame of the differential unit 182) by use of the first clutch 226. Such engagement (see FIGS. 2 and 3) causes the ring gear 256 to become stationary relative to the housing 206 of the differential unit 182, in turn operatively engaging the flywheel 222 to the crown gear 200. In so doing, a transfer of motion from the crown gear 200 to the flywheel 222 (and, in some cases, a transfer of motion from the flywheel 222 to the crown gear 200) may be attained. As an exemplary flow of motion, a movement gathered from the crown gear 200 (arrow, C, FIG. 3) may be first transferred to the bevel gear 250. A movement of the bevel gear 250 may be passed to the carrier 260, which in turn may turn the set of planet gears 252 around the sun gear 254. Since the ring gear 256 may be stationary relative to the housing 206, a turning of the set of planet gears 252 around the sun gear 254 may eventually turn the sun gear 254. A movement imparted to the sun gear 254 causes the flywheel

-8222 to rotate (arrow, B, FIG. 3). In some embodiments, the flywheel 222 rotates at 7 times the speed of the bevel gear 250, and, thus, in some cases, a speed ratio attained between the flywheel 222 and the bevel gear 250 is 7:1.

[0021] The first clutch 226 may include a friction clutch that may rely upon frictional forces for its operation. In that way, the first clutch 226 may be able to connect a moving component to another component that is either moving at a different speed or is stationary, in a stepwise manner. In this case, the first clutch 226 may facilitate an engagement of the ring gear 256 to the housing 206 of the differential unit 182 (the housing 206 itself may be immovable relative to the machine 100). In so doing, the first clutch 226 may facilitate a selective engagement of the flywheel 222 with the differential unit 182, enabling a selective transfer of power between the flywheel 222 and the differential unit 182 (i.e., the crown gear 200) through the planetary gear assembly 220. Additionally, or optionally, the first clutch 226 may include other clutch types, such as a multi-plate clutch, or a magnetic clutch, or any other type of clutch that may facilitate an engagement/disengagement between the housing 206 of the differential unit 182 and the ring gear 256.

[0022] The motor 224 may be a hydraulic motor 264 that converts hydraulic pressure into torque, and may selectively power a rotation of the flywheel 222 through a set of transfer gears 270. The set of transfer gears 270 may include a spur gear 272 and a gearing arrangement 274. For example, the motor 224 may be operatively coupled to the spur gear 272, which may be in turn meshed with the gearing arrangement 274 provided at an end 276 of the shaft 242 extending from (and through) the flywheel 222, as shown. In that manner, the motor 224 may power a rotation of the spur gear 272, and in turn of the flywheel 222. In some embodiments, it is possible that a belt drive be used to transmit motion from the motor 224 to the flywheel 222 instead of using the set of transfer gears 270. In some embodiments, the motor 224 may power a spinning of the flywheel 222 up to a speed that may be higher than a speed attained by the crown gear 200 in any of the discrete steps. Further, although a hydraulic motor 264 is disclosed, it is

-9possible for the motor 224 to embody various other types of motors. For example, an electric motor may be applied instead. Although not limited, a working of the motor 224 may be powered by the power source 176.

[0023] The second clutch 228 may help the motor 224 to selectively power a rotation of the flywheel 222. To this end, the second clutch 228 may be disposed between the spur gear 272 and the motor 224, as shown, and may facilitate an operative engagement of the motor 224 to the spur gear 272. For example, the second clutch 228 may include a one-way clutch 280 that may allow the motor 224 to drive the flywheel 222 alone, and may disallow any transfer of motion to be enabled from the flywheel 222 to the motor 224. However, in some cases, the second clutch 228 may be of a type that allows two-way transfer of motion when engaged - i.e., motion may be transferred from the motor 224 to the flywheel 222, and motion may be transferred from the flywheel 222 to the motor 224, as well. Such two-way transfer of motion may facilitate the flywheel 222 to power the motor 224 (i.e., the hydraulic motor 264) in some situations, and, in turn, the hydraulic motor 264 may be optionally used to power one or more auxiliary systems, such as a secondary steering system (not shown), of the machine 100. In cases where use of a one-way clutch is omitted, the second clutch 228 may include any of the aforementioned clutch types discussed for the first clutch 226.

[0024] Referring again to FIG. 2, in some embodiments, the energy storage system 190 includes a controller 300 that is coupled to the motor 224 and to the first clutch 226. The controller 300 may include a control strategy, according to which the controller 300 may control and switch (and/or vary) the first clutch 226 between an ‘engaged state’ and a ‘disengaged state’. For example, in the engaged state, the ring gear 256 may be engaged to the housing 206, and the flywheel 222 may be in operative engagement with the crown gear 200 and may receive/transfer rotational energy from/to the crown gear 200. Similarly, in the disengaged state, the ring gear 256 may be disengaged from the housing 206, and the flywheel 222 may be disengaged from the crown gear 200 and may not receive input from the

-10crown gear 200. According to the control strategy, the controller 300 may also be able to activate and deactivate an operation of the motor 224.

[0025] According to an aspect of the present disclosure, the controller 300 may also be coupled to the transmission unit 178 so as to receive signals pertaining to the change in gear ratios (e.g., the discrete steps) and upshifts and downshifts from the transmission unit 178. For example, the transmission unit 178 provides 5 discrete steps (as already noted in an example above), and data pertaining to every shift from any preceding discrete step to any succeeding discrete step may be delivered to the controller 300 via a dedicated link 302 - the link 302 may be a physical link or a wireless link. As an example, the controller 300 may process a time for which a discrete step has been maintained, and/or a time within which a shift from one discrete step to another discrete step has occurred, and the same may be recorded in a memory (not shown) associated with the controller 300. If in any case, the machine 100 is quickly accelerating, shifts may become increasingly frequent, and if one or more shifts are occurring within a preset time threshold, the controller 300 may anticipate and determine the possibility of an occurrence of a future shift to a future discrete step. In some embodiments, it may be prestored within the memory that the shift duration associated with the future shift to the future discrete step may require the supplementary energy from the energy storage system 190, so as to mitigate torque holes during the future shift.

[0026] In one example, the discrete step that precedes the future discrete step may be a predetermined discrete step - which may be prestored within the memory, and which, upon occurrence, may be detectable by the controller 300. With the controller 300 being able to determine the possibility of the future shift to the future discrete step based on the preset time threshold, the controller 300 may carry out a series of functions. For ease in understanding these series of functions, the predetermined discrete step may be referred to as a ‘preceding discrete step’, while the future discrete step may be referred to as a ‘succeeding discrete step’ (i.e., a discrete step that succeeds the preceding discrete step).

-11[0027] According to the series of functions, the controller 300 is configured to detect an onset of the preceding discrete step. Thereafter, the controller 300 controls the first clutch 226 to move to the disengaged state, and thereby disables a power transfer between the differential unit 182 and the flywheel 222 at the preceding discrete step. Next, the controller 300 activates the motor 224 to rotate the flywheel 222 up to a speed to generate supplementary kinetic energy at the flywheel 222. In some embodiments, the flywheel 222 is set to attain a speed of rotation (which in this case may be equivalent to a maximum speed offered by the motor 224). Further, as the shift to the succeeding discrete step is detected by the controller 300, the controller 300 controls the first clutch 226 to gradually (or in a stepwise fashion) move to the engaged state, thereby enabling a power transfer from the flywheel 222 to the differential unit 182, and in turn facilitating transfer of the supplementary kinetic energy from the flywheel 222 to the differential unit during the shift (i.e., the future shift defined between the preceding discrete step and the succeeding discrete step). It may be noted that the speed at which the motor 224 may spin the flywheel 222 may be higher than a maximum rotational speed of the crown gear 200 attainable at the preceding step (or at any discrete step). An exemplary detailed sequence of events is laid out later in the present disclosure.

[0028] In some cases, the controller 300 may be connected to the machine’s electronic control module (ECM) (or the controller 300 may be integral and be one and the same as the ECM). The ECM may provide data pertaining to a position or state of the implements (such as of the drawbar 142) to the controller 300. If the drawbar 142 were in a retracted state, the controller 300 may keep the control strategy deactivated for the entire period for which the drawbar 142 is in the retracted state. This is because a retracted state of the drawbar 142 may be inferred as a general running state of the machine 100 (i.e., when the machine 100 is traveling from a source to a destination and no load from the underlying materials 106 is sustained). Alternatively, if the drawbar 142 were in the extended state, in which position the drawbar 142 may engage with the underlying materials 106 of the work surface 110, the controller 300 may keep the control strategy activated.

-12Industrial Applicability [0029] Since the present disclosure exemplarily contemplates the provision of 5 discrete gear ratios by the transmission unit 178, a speed of the machine 100 may vary from a 1^st discrete step to a 5^th discrete step. For describing the aspects of the present disclosure, it may be contemplated that the preceding discrete step is the 4^th discrete step and the succeeding discrete step is the 5^th discrete step.

[0030] During operation, as the machine 100 moves over the work surface 110, the transmission unit 178 may progress from the 1^st discrete step to the 4^th discrete step. The first clutch 226 may remain in an engaged state throughout the progress from the 1^st discrete step to the 4^th discrete step, ensuring that the ring gear 256 is stationary relative to the housing 206 of the differential unit 182, and that a motion of the crown gear 200 is passed to the flywheel 222 through the planetary gear assembly 220. However, during every shift duration (i.e., between the 1^st discrete step and the 2^nd discrete step, between the 2^nd discrete step and the 3^rd discrete step, and between the 3^rd discrete step and the 4^th discrete step), an inertia of the rotating (or free-wheeling) flywheel 222 may be provided in return to the crown gear 200, and, thus, to the powertrain 174, in turn stabilizing machine movement, providing a natural load leveling effect on the powertrain 174, and thereby arresting torque holes during those shift durations.

[0031] At the onset of the 4^th discrete step, the controller 300 analyzes and anticipates the possibility of a future shift occurring from the 4^th discrete step to the 5^th discrete step. Such anticipation is possible by determining how quickly the machine 100 is accelerating. As an example, if the shifts from the 1^st discrete step to the 4^th discrete step, or if the shift from the 3^rd discrete step to the 4^th discrete step occurs within a preset time threshold, the controller 300 may determine that a shift from the 4^th discrete step to the 5^th discrete step is impending and highly possible.

[0032] As a result, from the onset of the 4^th discrete step, the controller 300 controls the first clutch 226 to disengage ring gear 256 from the housing 206, thus disallowing a motion transfer between the flywheel 222 and the crown gear. With

-13the flywheel 222 now independent from an engagement to the crown gear 200, the flywheel starts to free-wheel. At this point, the controller 300 activates the motor 224, and the motor 224 starts powering the rotation of the flywheel 222, adding additional inertia to the flywheel 222. In some cases, the motor 224 spins the flywheel 222 up to a speed higher than a maximum rotational speed of the crown gear 200 attainable at the preceding discrete step (or at any discrete step), and thereby facilitates the generation of supplementary kinetic energy at the flywheel 222. hr some embodiments, the motor 224 rotates at its maximum speed, transferring the equivalent amount of kinetic energy to the flywheel 222. Thereafter, as a progress or shift from the 4^th discrete step to the 5^th discrete step is initiated, the controller 300 determines the start of the shift, and, in response, controls the first clutch 226 to facilitate a stepwise engagement of the ring gear 256 to the housing 206 of the differential unit 182, thereby operatively engaging the crown gear 200 with the flywheel 222, in turn transferring the supplementary kinetic energy and torque generated at the flywheel 222 to the crown gear 200, and thus to the driveshaft 180 and the axle unit 184 (arrow, C, FIG. 3) of the powertrain 174.

[0033] The energy storage system 190 of the present disclosure enables torque continuity, enhanced efficiency, and performance of an operation of the machine 100 by stabilizing machine movement and arresting torque holes during transmission shift events. Therefore, if a tough spot, such as a boulder, is encountered while grading, for example, the energy storage system 190 may help push through it without stalling the power source 176. In particular, in machines where a transmission shift event occurs with the drawing of a relatively significant portion of the engine’s power, such as is discussed for the 4^th discrete step to the 5^th discrete step in the present disclosure, the motor 224 facilitates a dump of additional kinetic energy into the powertrain 174, thereby maintaining torque continuity across such transmission shift events. In some optional embodiments, since the flywheel 222 may be inherently resistant to speed change, the energy storage system 190 may also be applied to assist in decelerating the machine 100.

-14Furthermore, the energy storage system 190 is environment friendly, compact for integration into the axle unit 184, and cost efficient, and may be adapted for incorporation into a variety of machines, other than the one described in the present disclosure.

[0034] It will be apparent to those skilled in the art that various modifications and variations can be made to the system of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalent.

Claims

1. A powertrain system for a machine, the powertrain system comprising: a transmission unit configured to vary a speed of the machine in discrete steps;

a differential unit operatively engaged with the transmission unit and configured to receive rotary power from the transmission unit;

a flywheel selectively coupled with the differential unit;

a planetary gear assembly configured to facilitate a transfer of power between the differential unit and the flywheel;

a clutch to selectively engage the flywheel with the differential unit to enable a selective transfer of power between the flywheel and the differential unit through the planetary gear assembly;

a motor to selectively power a rotation of the flywheel; and a controller configured to:

detect a predetermined discrete step;

control the clutch to disable a power transfer between the differential unit and the flywheel based on the predetermined discrete step;

activate the motor to rotate the flywheel up to a speed to generate supplementary kinetic energy at the flywheel; and control the clutch to enable a power transfer from the flywheel to the differential unit, facilitating transfer of the supplementary kinetic energy from the flywheel to the differential unit during a shift from the predetermined discrete step to a succeeding discrete step.