POWERTRAIN ECO-MODE FOR WORK MACHINES

A work machine having a powertrain, an engine, a torque converter operably connected to the engine, a transmission, a selector interface, and a control system. The control system is configured to: receive a machine activation signal from the selector interface indicative of operation of the work machine; receive machine conditions to determine an optimal gear for next pass; and send a gear pass signal to command execution of a directional shift and a speed shift simultaneously when a gear ratio setting of the transmission is indicative of a second gear ratio.

TECHNICAL FIELD

The present disclosure relates generally to a powertrain of a work machine, and more particularly relates to a control system for a powertrain system of the work machine.

BACKGROUND

A compactor is adapted to compact a material to a desired density. The compactor may be a landfill compactor or a soil compactor. Examples of applications include, but are not limited to, construction sites to prevent natural settling of the ground, landfill sites to compact the landfill waste into as small a volume as possible, and blacktop roads and parking lots, to prevent settling of the blacktop, and hence prevent future cracking of the road or the parking lots.

The landfill compactor is propelled by a powertrain having an engine connected to a transmission via a torque converter. One characteristic of torque converters is their ability to multiply torque when there is a difference between the input speed to the converter from the engine and the output speed of the converter to the transmission. Some torque converters also include a locking mechanism that transfers engine speed directly to the transmission with no substantial torque multiplication or speed variation. The landfill compactor may be desired to run in a first or second gear transmission ratio for efficient fuel management. Further, the use of torque converter in the second gear transmission ratio may overheat the torque converter due to heavy loading conditions while on an inclination and lead to inefficiency of the landfill compactor and loss of fuel economy during gear to gear shifting.

U.S. Pat. No. 5,467,854 discloses a method of controlling clutch-to-clutch shifts for a transmission including a plurality of speed and direction changing clutches to produce a shift from a first transmission ratio to a second transmission ratio through disengagement of an off-going clutch associated with the first transmission ratio and engagement of an on-coming clutch associated with the second transmission ratio. During an upshift, the direction clutch is disengaged, then re-engaged after the on-coming speed clutch is engaged.

It can therefore be seen that a need exists for an improved control strategy that utilizes a work machine's conditions, in a particular inclination grade, to perform a directional shift and a speed shift simultaneously when executing a gear shift.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a work machine having a powertrain, an engine, a torque converter operably connected to the engine, a transmission, a selector interface, and a control system. The control system is configured to: receive a machine activation signal from the selector interface indicative of operation of the work machine; receive current machine conditions to determine an optimal gear for next pass; and send a gear pass signal to command execution of a directional shift and a speed shift when a gear ratio setting of the transmission is indicative of a second gear ratio.

In accordance with another aspect of the disclosure, a method for operating a work machine having a powertrain, the powertrain including an engine operably connected to a torque converter, a torque converter connected to a transmission, and a selector interface is disclosed. The method comprises: activating operation of the machine via the selector interface; receiving machine conditions by a control system to determine an optimal gear for next pass; and sending a gear pass signal by the control system to command execution of a directional shift and a speed shift simultaneously when a gear ratio setting of the transmission is indicative of a second gear ratio.

In accordance with another aspect of the disclosure, a work machine powertrain is disclosed. The work machine powertrain comprises: an engine operably connected to a torque converter, the torque converter connected to a transmission, and a control system. The control system is configured to: receive powertrain conditions to determine an optimal gear for next pass; and send a gear pass signal to command execution of a directional shift and a speed shift simultaneously when a gear ratio setting of the transmission is indicative of a second gear ratio.

These and other aspects and features of the present disclosure will be better understood upon reading the following detailed description when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

This disclosure generally relates to a powertrain of a machine having a transmission and, more particularly, to the powertrains that includes a torque converter capable of directly and selectively linking an output of an engine with the transmission.FIG.1, in one embodiment, displays a side view of a work machine100illustrated as a landfill compactor, in which various embodiments of the present disclosure may be implemented. In the illustrated embodiment, the work machine100may include an engine frame portion102connected to a non-engine frame portion104by an articulated joint106. Further, a set of ground engaging elements108, such as a set of wheels, may support the engine frame portion102and the non-engine frame portion104on ground. The engine frame portion102includes an engine110to provide power to the ground engaging elements108. The work machine100further includes an operator station112that houses various control devices which can be operated manually by an operator in the operator station112or autonomously. While the work machine100depicted and described as a landfill compactor, it is to be understood that the teachings of this disclosure applies to other work machines as well, including, but not limited to, excavators, track type tractors, backhoes, cranes, skid steers, wheel loaders, tractors, and mulchers, and the like

Now referring toFIG.2, in one embodiment, the work machine100may include one or more operator interface devices114located in the operator station112. The operator interface devices114may include a throttle pedal116having a throttle position sensor (TPS)118, and a gear selector lever120having a lever encoder122.

Furthermore,FIG.2illustrates a schematic of a powertrain200associated with the work machine100. Referring toFIGS.1and2, the powertrain200may include respective axles202connected to the set of ground engaging elements108. An engine output shaft204is connected to a torque converter206, and the torque converter206is further connected to a transmission208via a transmission input shaft210. Further, a transmission output shaft212is connected to a splitter214that powers two drive shafts216, one for each of the axles202. Each of the drive shafts216transmits power to the ground engaging elements108via respective differentials218such that rotational power produced at the engine output shaft204is transmitted to the ground engaging elements108. The torque converter206may be a hydro-mechanical device configured to couple the engine110with the transmission208. The torque converter206may include a lock-up clutch220for selectively coupling the engine output shaft204to the transmission input shaft210. The lock-up clutch220may be hydraulically actuated. The work machine100may operate with or without a lock-up clutch220. A person having ordinary skill in the arts would recognize that the work machine100may require a lock-up clutch220for some applications in the field of use and in other applications of the work machine100do not require a lock-up clutch220. The work machine100may further comprise directional clutches and speed clutches.

The transmission208may embody a multi-speed, bidirectional, mechanical transmission having a neutral gear ratio, a plurality of forward gear ratios, and a plurality of reverse gear ratios. The forward gear ratios may include a first gear ratio and a second gear ratio. The reverse gear ratios may include a first reverse gear ratio and a second reverse gear ratio.

The TPS118and the lever encoder122are configured to provide a desired ground speed signal indicative of a desired machine speed and a current gear ratio setting of the transmission208that is commanded by an operator during the operation. The operator interface devices114may also include a selector interface124configure to select a manual mode or an automatic mode operation of the work machine100. The selector interface124may embody a switch, a dial, a lever, a touch-based interface, or a voice-based interface or the like. One will recognize that the work machine100may be configured to operate only in automatic mode or be configured to selectively operate in either an automatic or manual made.

As shown inFIG.2, a control system222is provided to regulate the operation of the powertrain200. The control system222may be an electronic controller that may include a processor operably associated with other electronic components such as data storage devices and various communication channels. The control system222is connected to an engine output shaft speed sensor224via an engine speed communication channel226, a torque converter locked state sensor228via a torque converter communication channel230, a ground speed sensor232via a ground speed communication channel234, and an inclinometer sensor235via a machine grade communication channel237. The inclinometer sensor235is configured to provide a machine grade percentage or inclination of the work machine100while on ground level or a sloped ground while the work machine100is moving in reverse or forward motion. The slope may be an inclined or declined slope.

The control system222may regulate the operation of the powertrain200in response to signals indicative of the operation of the powertrain200as well as the signals received from the operator interface devices114, such as the TPS118, the lever encoder122, and the selector interface124. The selector interface124may also be configured to display the current machine conditions received by the control system222through the various communication channels.

The powertrain200may further include a transmission controller236, which is configured to control the operation of the transmission208. The transmission controller236is connected to a transmission interface238via a transmission communication channel240. The transmission interface238may include a data structure that can selectively engage the transmission208in the first gear ratio or the second gear ratio in response to a command from the transmission controller236. The transmission interface238may also provide information to the transmission controller236indicative of the current gear ratio setting as well as other information, such as the power transmitted to the ground engaging elements108through the transmission208, the speed of the transmission output shaft212, the speed of the transmission input shaft210, the machine grade percentage from the inclinometer sensor235, the engagement status of the lock-up clutch220, and the like. In the illustrated embodiment, information may be exchanged between the control system222and the transmission controller236via a data bus242. However, it should be appreciated that although the control system222and the transmission controller236are shown as separate components they may alternatively be integrated into a single control unit. For example, a master controller may be operatively implemented within an engine control unit (ECU), used to control the engine110. The functionality of these devices, while shown conceptually inFIG.2that include various discrete functions for illustrative purposes only, may be implemented in hardware and/or software without regard to the discrete functionality shown. Accordingly, various interfaces of the control system222and the transmission controller236are described relative to the other components of the powertrain200inFIG.2, which follows such interfaces, are not intended to limit other type of components.

According to an embodiment of the present disclosure, the control system222is configured to send a speed command signal to an engine interface244associated with the engine110via an engine communication channel246based on an activation signal received from the selector interface124indicative of the automatic mode operation of the work machine100. The speed command signal may limit the engine speed at the engine output shaft204below a first engine speed limit. The first engine speed limit may be a transmission requested engine speed limit (TRESL) and may lie in a range of about 1400 rpm to 1600 rpm. The first engine speed limit is 1400 rpm. However, it will be apparent to a person having ordinary skill in the art that the first engine speed limit may vary based on the application and size of the engine110and the transmission208. Further, the speed command signal may be based on the current gear ratio setting of the transmission208received and processed by the control system222via the transmission controller236. The speed command signal may be transmitted when the gear ratio setting of the transmission208and current machine conditions is indicative of the second gear ratio, while on an inclined or declined slope or while on ground level. As described above, the control system222is configured to receive a ground speed signal from the ground speed sensor232via the ground speed communication channel234. The first engine speed limit may also be based on the ground speed signal, such a machine speed in the second gear ratio of the transmission208is below a ground speed limit. The ground speed limit is 4.0 mph. The signals received by the control system222may be provided continuously during operation of the work machine100.

The control system222may be further configured to receive the machine grade percentage of the work machine100on a certain grade level. The machine grade signal may be transmitted continuously from the inclinometer sensor235via the machine grade communication channel237. It will be recognized that there may be a plurality of inclinometer sensors235provided on the work machine100. The control system222determines execution of the directional shift and speed shift simultaneously for the optimal gear for the next pass or desired in response to the current conditions of the work machine100including torque converter output speed, torque converter output torque, gear, lock-up clutch engagement, and machine grade percentage. The simultaneous directional and speed shifts are executed using the current conditions of the work machine100and optimized for increasing fuel economy, increasing productivity, increasing efficiency, and decreasing component wear, while maintaining the same fuel rate. When the control system222executes the directional shift and speed shift at the same time, the directional clutches absorb a majority of the engagement energy which results in less wearing of the speed clutch.

The control system222is also configured to shift gear ratio settings of the transmission208during the automatic mode operation of the work machine100. The gear ratio settings of the transmission208may be activated through the torque converter206either in a converter-drive operating mode (“CD”) or in a direct-drive operating mode (“DD”), when the lock-up clutch220is in a locked position. During the automatic mode operation of the work machine100, the control system222may command the torque converter206to remain in the direct-drive mode (DD) while the transmission208shifts from the first gear ratio to the second gear ratio. Moreover, an up-shift and a down-shift sequences for the powertrain200during the automatic mode operation of the work machine100may be:1CD→1DD→2CD→2DD (during up-shift)2DD→2CD→1DD→1CD (during down-shift)
where the numbers 1-2 represent the first gear ratio and the second gear ratio settings of the transmission208, “CD” represents the converter-drive mode of the torque converter206, and “DD” represents the direct-drive mode of the torque converter206. Moreover, an additional down-shift sequences for the powertrain200is permitted during the automatic mode operation of the work machine100such as:2DD→2CD→1CD (during down-shift)
During the up-shift in the automatic mode operation of the work machine100, the shift in the gear ratio settings of the transmission208from 1DD→2DD may occur at a substantially full throttle position. A throttle position signal is configured to be received by the control system222from the TPS118associated with the throttle pedal116.

The control system222uses the current machine conditions, including torque converter output speed and torque, gear, lock up clutch engagement, and machine grade percentage, to determine the optimal gear for the next pass and then command a gear when a change in directional speed or clutch engagement occurs. The control system222is configured to calculate the speed and torque thresholds in each gear while the work machine100is on a slope by calibrating the machine grade percentage of the sloped ground received by the inclinometer, while the work machine100moves in either forward or reverse gears. The torque converter output speed and torque converter output torque are then used to determine the speed and torque thresholds to be used in the next state flow. When above a certain speed and torque threshold, the control system222will command an upshift by executing a directional clutch shift and speed clutch shift simultaneously. When performing a directional shift while on a sloped surface, the directional shift or directional clutch and the necessary speed shift or speed clutches may be executed at the same time. By executing the directional shift and speed shift simultaneously while on a sloped surface, the directional clutch may absorb the engagement energy resulting in less wearing of the speed clutch. Each directional shift in the multi-pass sequence increases fuel economy and decreases wear on components during shifting.

In another embodiment, in the manual mode operation of the work machine100, while shifting the gear ratio settings of the transmission208from direct-drive mode first gear ratio (1DD) to the second gear ratio, the control system222is configured to automatically lock the lock-up clutch220. Thus, achieve 1DD→2DD shift in the gear ratio settings of the transmission208during the up-shift in the manual mode operation of the work machine100.

Moreover, the control system222is also configured to limit the engine speed from passing a second engine speed limit. The second engine speed limit may be a threshold engine speed to restrict an uncontrolled increase in the engine speed, leading to a mechanical failure. The control system222may receive an engine speed signal from the engine output shaft speed sensor224via the engine speed communication channel226, and monitor for an over-speed condition of the engine110. Based on the over-speed condition of the engine110, the control system222may further regulate the air/fuel supply to control the engine speed below the second engine speed limit, while on a slope or at ground level.

Furthermore, it will be apparent to a person having ordinary skill in the art that the control system222may further be operating in conjunction or cooperation with other control schemes or algorithms, which are not shown for simplicity. Relative to the present disclosure, the control system222operates to select an appropriate set of engine power curves depending on the operating conditions of the engine110, the torque converter206and the transmission208, while on a slope or at ground level.

INDUSTRIAL APPLICABILITY

In operation, the present disclosure may find applicability in many industries including, but not limited to, the mining, construction, earth-moving, industrial, and agricultural industries. While the foregoing detailed description is made with specific reference to landfill compactors, it is to be understood that its teachings may also be applied onto any type of work machine such as, but not limited to, backhoes, cranes, skid steers, wheel loaders, tractors, and mulchers, and the like, may embody the disclosed systems and methods, for performing at least one operation associated with mining, construction, and other industrial or non-industrial applications. The industrial applicability of the systems and methods for controlling a powertrain having a torque converter connected to a transmission in a machine described herein will be readily appreciated from the foregoing discussion.

In accordance with an embodiment of the present disclosure, largely, the operating performance of a machine such as, material compaction performance in case of the landfill compactor, is based on the machine speed of the machine and a rolling resistance experienced by the machine, taking into consideration the inclination of the ground. Typically, engine load/power of the machine is controlled based on the machine speed and the rolling resistance experienced by the machine to achieve an optimal operating performance. Moreover, the machine speed is required to be maintained below a ground speed limit to achieve the optimal operating performance. Usually, to achieve the optimal operating performance and the fuel efficiency, the machine is operated in the second gear ratio of the transmission with a converter-drive mode of the torque converter to maintain the machine speed below the ground speed limit. However, the torque convertor may be overheated due to continuous working cycles of the machine in the first or second gear ratio with the converter-drive mode. This may adversely affect a lifetime of the torque convertor and reduce the performance of the overall powertrain. By utilizing the inclinometer sensor235, the performance of the powertrain in the work machine100may increase the efficiency, productivity, and fuel economy, decrease the wear on components for shifting, and improving upshifting and downshifting commands by the control system222. The inclinometer sensor235provides the machine grade percentage to the control system222for better optimized gear shifting commands which aids in increasing the productivity, efficiency, and fuel economy utilizing the same fuel rate.

The control system222may limit the engine speed below the pre-determined speed (TRESL) in the second gear ratio of the transmission208and select the torque converter206in the direct-drive mode (DD) to achieve a desired machine speed while operating. Advantageously, the control system222may achieve fuel efficiency by operating in the second gear ratio, optimal operating performance by maintaining the desired machine speed, and avoid overheating of the torque converter206by remaining in the direct-drive mode (DD) while in the second gear ratio.

FIG.3illustrates a flowchart for an exemplary transmission transition strategy300in the work machine100, in accordance with one embodiment of the present disclosure. At step302, an operator may start the work machine100in the converter-drive mode second gear ratio (2CD) to initiate compaction process. At step304, the operator may select the automatic mode operation of the work machine100, if the automatic mode operation is selected (Step304: YES), the control system222may down-shift the powertrain200to the converter-drive mode first gear ratio (1CD) at step306. Following step306, the control system222may up-shift the powertrain200to the direct-drive mode first gear ratio (1DD) at step308. The control system222may provide a delay of a pre-determined time during the up-shift from 1CD→1DD to minimize any undesirable loading/jerks. The pre-determined time may be in a range of about 2 seconds to 5 seconds. Further, as described above, at step310, based on the machine speed and machine grade percentage associated with the work machine100and/or the throttle position signal, the control system222may up-shift the powertrain200to the second gear ratio of the transmission208while commanding the torque converter206to remain in the direct-drive mode. In the direct-drive mode second gear ratio (2DD), the machine speed associated with the landfill compactor may be limited below the ground speed limit while compacting the material. At step310, the control system222may also limit the engine speed below the first engine speed limit to achieve the optimal compaction performance and the fuel efficiency in the work machine100, while on a slope or ground level. At step310, control system222may also monitor for an over-speed condition of the engine110and limit the engine speed from passing the second engine speed limit, while on a slope or ground level.

Moreover, if the automatic mode operation is not selected at step304(Step304: NO), the control system222may up-shift the powertrain200to the direct-drive mode second gear ratio (2DD) based on an input from the operator, the inclinometer sensor235, and the machine speed at step312. In this mode, the work machine100may be primarily cruising without performing compaction of material. However, in the event an operator selects the automatic mode operation of the work machine100at step314, the control system222go to step310by limiting the engine speed below the first engine speed limit to achieve the optimal compaction performance and fuel efficiency. In the automatic mode operation of the work machine100, the control system222commands the gear shifts by considering the current machine conditions and the machine grade percentage. The control system222optimizes execution of each gear shift so that the directional shift and speed shift are executed simultaneously. When the directional shift and speed shift are executed simultaneously, the direction shift clutches absorbs a majority of the engagement energy which reduces the wear of the speed shift clutches.

FIG.4illustrates a flowchart for an exemplary transmission transition strategy400for forward gear shifts in the work machine100, in accordance with one embodiment of the present disclosure. At step402, an operator may start the work machine100in the converter-drive mode first gear ratio (1CD). At step404, the operator may increase the throttle position so that the torque converter output speed increases above a torque converter output speed threshold, the control system222may up-shift the powertrain200to the direct-drive mode first gear ratio (1DD). The control system222may up-shift the powertrain200to the direct-drive mode first gear ratio (1DD) whereby the directional shift and speed shift are executed at the same time in automatic mode or when the operator performs the up-shift in manual mode. If provided, the work machine100may utilize the lock-up clutch220to aid during gear shifting. The control system222may provide a delay of a pre-determined time during the up-shift from 1CD→1DD to minimize any undesirable loading/jerks during gear shifting. The pre-determined time may be in a range of about 2 seconds to 5 seconds, in step402. Furthermore, while in 1DD, the work machine100may decelerate so that the torque converter output speed decreases below a reverse torque converter output speed threshold, whereby the control system222down-shifts the powertrain200to the converter-drive mode first gear ratio (1CD), in a step406. The control system222may provide a delay of a pre-determined time during the down-shift.

Following step404, while in the 1DD the operator may accelerate the work machine100via the throttle pedal116so that the torque converter output speed increases above a second torque converter output speed threshold, the control system222may up-shift the powertrain200to the converter-drive mode second gear ratio (2CD), in a step408. The control system222may up-shift the powertrain200to the converter-drive mode second gear ratio (2CD) whereby the directional shift and speed shift are executed at the same time in automatic mode or when the operator performs the up-shift in manual mode. If provided, the work machine100may utilize the lock-up clutch220to aid during gear shifting. The control system222may provide a delay of a pre-determined time during the up-shift from 1DD→2CD to minimize any undesirable loading/jerks during gear shifting. The pre-determined time may be in a range of about 2 seconds to 5 seconds, in step404. Furthermore, while in 2CD, the work machine100may decelerate so that the torque converter output speed decreases below a reverse torque converter output speed threshold, whereby the control system222down-shifts the powertrain200to the converter-drive mode first gear ratio (1CD), in a step410. The control system222may provide a delay of a pre-determined time during the down-shift.

Following step408, while in the 2CD the operator may accelerate the work machine100via the throttle pedal116so that the torque converter output speed increases above a third torque converter output speed threshold, whereby the control system222may up-shift the powertrain200to the direct-drive mode second gear ratio (2DD), in a step412. The control system222may up-shift the powertrain200to the direct-drive mode second gear ratio (2DD) whereby the directional shift and speed shift are executed at the same time in automatic mode or when the operator performs the up-shift in manual mode. The control system222may provide a delay of a pre-determined time during the up-shift from 2CD→2DD to minimize any undesirable loading/jerks during gear shifting. The pre-determined time may be in a range of about 2 seconds to 5 seconds, in step406. Furthermore, while in 2DD, the work machine100may decelerate so that the torque converter output speed decreases below a third reverse torque converter output speed threshold, whereby the control system222down-shifts the powertrain200to the converter-drive mode second gear ratio (2CD), in a step414. The control system222may provide a delay of a pre-determined time during the down-shift.

Now referring toFIG.5, illustrates a flowchart for an exemplary transmission transition strategy500in the work machine100considering the machine conditions and inclination, in accordance with one embodiment of the present disclosure. At a first step502, the work machine100may start operation in a neutral gear. One will recognize that the machine may also start in any reverse, first, or second gear. At step504, the work machine100shifts into first or second gear, in either forward or reverse. In a step506, the control system222receives machine conditions including the machine speed, the torque converter output speed and torque, gear, lock up clutch engagement, and machine grade percentage. Next, in a step508, the control system222determines the proper speed gear in forward or reverse direction. At a step510, the control system222selects the gear shift direction. Alternatively, an operator in the work machine100may select the gear shift direction on the selector interface124. The control system222optimizes the gear shift and executes both the directional shift and speed shift simultaneously, in a step512. Returning to step504, the machine shifts into the desired first or second gear, in forward or reverse direction, continuously repeating steps506-512during operation of the work machine100to optimize and improve the efficiency, productivity, and fuel economy of the work machine100as well as reducing the wear on the components during shifting.

From the foregoing, it can be seen that the technology disclosed herein has industrial applicability in a variety of settings such as, but not limited to work machines in the construction and agricultural industries. It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples.