The present application relates generally to transmissions, and more particularly, to an auto efficiency mode for power shift transmissions.
Various types of agricultural vehicles (e.g., tractors, floaters, sprayers, or the like) may be used to plow a field, till land, plant seeds, or accomplish other similar agricultural operations. Typical agricultural vehicles include an engine configured to power the vehicle, and a transmission configured to transfer engine power to rotating wheels at a desired gear ratio.
Some agricultural vehicles include controllers that control the engine and/or transmission based on the assumption that the lowest possible engine speed is best for the engine's fuel economy. That is, some controllers do not calculate whether a higher or lower gear of the transmission may result in better overall fuel economy.
In one embodiment, a system includes an agricultural vehicle, including an engine, a transmission with multiple gear ratios driven by the engine, and a controller. The controller is configured to receive a requested wheel speed input by an operator, calculate a desired engine speed, command a gear upshift if a current engine speed is more than the desired engine speed and if upshifting will locate the current engine speed closer to the desired engine speed, and command a gear downshift if the current engine speed is less than the desired engine speed and if downshifting will locate the current engine speed closer to the desired engine speed.
In one embodiment, a tangible, non-transitory computer-readable media storing computer instructions thereon, the computer instructions, when executed by a processor: receive a requested wheel speed input by an operator, calculate a desired engine speed, command a gear upshift if a current engine speed is more than the desired engine speed and if upshifting will locate the current engine speed closer to the desired engine speed, and command a gear downshift if the current engine speed is less than the desired engine speed and if downshifting will locate the current engine speed closer to the desired engine speed.
In a third embodiment, a method of operating an agricultural vehicle, includes receiving a requested wheel speed input by an operator at a processor, commanding a gear upshift if a current engine speed is more than a desired engine speed and if upshifting will locate the current engine speed closer to the desired engine speed, and commanding a gear downshift if the current engine speed is less than the desired engine speed and if downshifting will locate the current engine speed closer to the desired engine speed.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
The embodiments disclosed herein relate to a system including an agricultural vehicle controller configured to achieve and maintain a requested wheel speed input by a driver. The controller uses an auto-efficiency mode (AEM) controller to carry out the techniques described herein. The controller may reduce occurrences of engine stalling by managing power consumption. The controller may be configured to substantially match the engine speed to a requested wheel speed, while using a power-engine speed curve. The controller may adjust an engine speed and a transmission gear to maintain the requested wheel speed and to minimize fuel consumption at a given power. The controller may also receive signals from other components (e.g., a brake controller, and so forth).
In certain embodiments, the controller system receives a driver input (e.g., via a speed control lever. The controller system may calculate a corresponding transmission output and a corresponding acceptable engine speed range. The controller system may determine if the desired engine speed is more than a maximum engine speed, and shifts up and throttles back (e.g., reduces engine speed) until the engine speed is less than the maximum engine speed. If the desired engine speed is less than a minimum engine speed, the controller system shifts down and throttles up (e.g., increases engine speed) until the desired engine speed is more than the minimum engine speed. The controller system may control an engine speed governor to adjust the current engine speed to reach the desired engine speed by adjusting a quantity of fuel injected.
The controller system may use a brake specific fuel consumption (BSFC) subsystem to select a desired engine speed based on an optimal BSFC curve for the engine. In some embodiments, no gear will enable the engine speed to fall on the optimal BSFC curve. In these instances, the controller system may use the techniques described herein to locate the engine speed as close as possible to the desired engine speed on the optimal BSFC curve.
The controller system first estimates a torque value (e.g., after upshifting using gear ratios). The estimated torque value is then multiplied by the actual engine speed to calculate a power requirement (e.g., a power that enables the requested wheel speed). The power requirement may be determined after the requested wheel speed is achieved (e.g., at steady state). The controller system uses a BSFC subsystem to determine an optimal or desired engine speed (e.g., a desired engine speed or the engine speed at which the value of the BSFC is lowest for a given engine power). The BSFC subsystem may use a BSFC look up table to determine the desired engine speed. The BSFC curve and/or look up table may be engine-specific (e.g., based on engine characteristics) and may be pre-determined and/or stored in a memory within or accessible to the controller system.
The controller system may command an upshift if a current engine speed is more than the desired engine speed and if upshifting will result in moving closer to the desired engine speed. The controller system may command a downshift if the current engine speed is less than the desired engine speed and if downshifting will result in moving closer to the desired engine speed. In certain embodiments, the controller system may command an upshift if the current engine speed is greater than the desired engine speed, if upshifting will result in moving closer to the desired engine speed, and/or if a maximum gear index has not been reached (e.g., a higher gear is available). As described above, the controller system may control the engine speed by controlling an engine speed governor. The engine speed governor adjusts the current engine speed to reach the desired engine speed by adjusting a quantity of fuel injected.
In certain embodiments, the controller system may command a downshift if the current engine speed is less than the desired engine speed, if downshifting will result in moving closer to the desired engine speed, and/or if a minimum gear index has not been reached (e.g., a lower gear is available).
The controller system may include various protection subsystems. For example, the controller system may include a maximum gear index to avoid engine stalling when the engine is under high load conditions (e.g., upshift protection). The controller system may also include a mechanism to downshift if the power (e.g., power requirement) exceeds the maximum available engine power to reduce occurrences of stalling (e.g., downshift protection). The controller system may include a power protection subsystem. For example, if the current wheel speed is lower than the requested wheel speed, the power protection subsystem may estimate a hypothetical power value if an upshift occurs, and if the hypothetical power value is higher than the maximum available engine power, the upshift does not occur. As used herein, the maximum available engine power, the maximum engine speed, and the minimum engine speed are engine characteristics and/or are known or pre-determined features of the engine.
With the foregoing in mind,
In the illustrated embodiment, the engine controller 34 may receive signals from sensors configured to output data indicative of a condition (e.g., speed) of the engine 52. In certain embodiments, the engine controller 34 may control the engine 42 such that the engine maintains a constant engine speed. The agricultural vehicle controller 36 is communicatively coupled to the engine controller 34 and the transmission controller 38. In the illustrated embodiment, the agricultural vehicle controller 36 includes a memory 50 and a processor 52. The memory 50 may be any type of non-transitory machine readable medium for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, optical discs, and the like. The processor 52 may execute instructions stored on the memory 50. For example, the memory 50 may contain machine readable code, such as instructions, that may be executed by the processor 52. In some embodiments, the memory 50 and the processor 52 of the agricultural vehicle controller 36 may instruct the engine controller 34 and/or the transmission controller 38 to automatically shift (e.g., processor/memory controlled) between gears of the transmission 44 to improve brake specific fuel consumption, for example.
In the illustrated embodiment, a requested wheel speed may be set by a user (e.g., via a speed control lever, the user interface 48, or other input device). The user interface 48 may enable an operator to select an engine speed and/or adjust various parameters associated with the engine/transmission system operation. An AEM mode (e.g., executed by the controller system 31) may be configured to determine a corresponding transmission output and a corresponding desired engine speed. For example, the corresponding transmission output may be determined based on the requested wheel speed, gear ratio, and tire radius. The corresponding desired engine speed may be determined based on the corresponding transmission output, gear index, and current gear ratio.
The controller system 31 first estimates a torque value (e.g., after upshifting using gear ratios). The estimated torque value is then multiplied by the actual engine speed to calculate a power requirement (e.g., a power that enables the requested wheel speed). The power requirement may be determined after the requested wheel speed is achieved (e.g., at steady state). The controller system 31 uses a BSFC subsystem to determine an optimal engine speed (e.g., a desired engine speed or the engine speed at which the value of the BSFC is lowest for a given power requirement). The BSFC subsystem may use a BSFC look up table to determine the desired engine speed. The BSFC curve and/or look up table may be engine-specific (e.g., based on engine characteristics) and may be pre-determined and/or stored in a memory within or accessible to the controller system 31.
The controller system 31 may control the engine speed by controlling an engine speed governor 40. The engine speed governor 40 may adjust the current engine speed to reach the desired wheel speed, including adjusting the engine speed after an upshift or downshift. For example, the engine speed governor 40 may adjust the current engine speed by adjusting a quantity of fuel injected to achieve and/or maintain a wheel speed close to the desired wheel speed.
The controller system 31 may command an upshift if a current engine speed is more than the desired engine speed and if upshifting will result in moving closer to the desired engine speed. The controller system 31 may command a downshift if the current engine speed is less than the desired engine speed and if downshifting will result in moving closer to the desired engine speed. In certain embodiments, the controller system 31 may command an upshift if the current engine speed is greater than the desired engine speed, if upshifting will result in moving closer to the desired engine speed, and/or if a maximum gear index has not been reached (e.g., a higher gear is available).
In certain embodiments, the controller system 31 may command a downshift if the current engine speed is less than the desired engine speed, if downshifting will result in moving closer to the desired engine speed, and/or if a minimum gear index has not been reached (e.g., a lower gear is available).
The controller system 31 may include various protection subsystems. For example, the controller system 31 may include a maximum gear index to avoid engine stalling when the engine is under high load conditions (e.g., upshift protection). The controller system 31 may also include a mechanism to downshift if the power (e.g., power requirement) approaches the maximum available engine power at the current engine speed to reduce occurrences of stalling (e.g., downshift protection). The controller system 31 may include a power protection subsystem. For example, if the current wheel speed is lower than the requested wheel speed, the power protection subsystem may estimate a hypothetical power value if an upshift occurs, and if the hypothetical power value is higher than the maximum available engine power, the upshift does not occur. As used herein, the maximum available engine power, the maximum engine speed, and the minimum engine speed are engine characteristics and/or are known or pre-determined features of the engine.
As noted above, in some embodiments, the control system 30 may be configured to calculate a corresponding transmission output and a corresponding desired engine speed based at least in part on the requested wheel speed. In certain embodiments, the controller system 31 may command an upshift if the current engine speed is greater than the desired engine speed, if upshifting will result in moving closer to the desired engine speed, and/or if a maximum gear index has not been reached (e.g., a higher gear is available).
In certain embodiments, the controller system 31 may command a downshift if the current engine speed is less than the desired engine speed, if downshifting will result in moving closer to the desired engine speed, and/or if a minimum gear index has not been reached (e.g., a lower gear is available).
It should be understood that the steps (e.g., the steps of method 70) disclosed herein by be performed by any suitable components of the control system 30, including the controllers 34, 36, 38, and their respective processors and memory components, for example.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.