The present disclosure generally relates to a vehicle powertrain.
Vehicle powertrains may be comprised of electric machines, multi-speed transmissions, disconnect mechanisms, and gearboxes.
According to an aspect of the present disclosure, a vehicle may include an engine, a first electric machine, a multi-speed transmission, a second electric machine, and a third electric machine. The first electric machine may be connected to the engine. The multi-speed transmission may be engageable with the ground through a gearbox. The second electric machine may electrically connected to the first electric machine and may be engageable with the ground through the multi-speed transmission. The third electric machine may be electrically connected to the first electric machine and may be engageable with the ground through the gearbox but not through the multi-speed transmission.
According to another aspect of the present disclosure, the vehicle may also include a controller configured to command the second electric machine and the third electric machine based on a position of a user input.
According to another aspect of the present disclosure, the controller may also be configured to command the second electric machine and the third electric machine based on an efficiency of the second electric machine and an efficiency of the third electric machine.
According to another aspect of the present disclosure, a method of controlling a powertrain of a vehicle may include sensing an input indicative of at least one of a requested rimpull, requested acceleration, requested speed, and requested torque for the vehicle, sensing an input indicative of a speed of the vehicle, selecting a first available rimpull from a first electric machine engageable with the ground through a multi-speed transmission, selecting a second available rimpull from a second electric machine engageable with the ground at a fixed speed ratio, commanding the first electric machine to produce the first rimpull, and commanding the second electric machine to produce the second rimpull.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting at least one of the first rimpull and the second rimpull based on an efficiency with which at least one of the first electric machine can produce the first rimpull and the second electric machine can produce the second rimpull.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting the first rimpull and selecting the second rimpull such that, when combined, the first rimpull and the second rimpull are sufficient to achieve the requested rimpull, requested acceleration, requested speed, or requested torque.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting the first rimpull and selecting the second rimpull based on an efficiency with which the first electric machine can produce the first rimpull, an efficiency with which the second electric machine can produce the second rimpull, and the requested rimpull, requested acceleration, requested speed, or requested torque.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting the first rimpull and selecting the second rimpull based on the amount of vehicle power generated in excess of vehicle power consumed.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting the first rimpull and the second rimpull to achieve the requested rimpull, requested acceleration, requested speed, or requested torque while minimizing the rimpull from one of the first electric machine or the second electric machine.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting the first rimpull and the second rimpull based on a temperature of the first electric machine, the second electric machine, or the multi-speed transmission.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include commanding a disconnect mechanism to open and disengage the multi-speed transmission from the ground when the first rimpull is zero.
According to another aspect of the present disclosure, the method of controlling the powertrain of the vehicle may also include selecting a non-zero value for the first rimpull, determining whether a disconnect mechanism through which the multi-speed transmission is engageable with the ground is disconnected, commanding the first electric machine to reduce the difference between an input speed of the disconnect mechanism and an output speed of the disconnect mechanism while the disconnect mechanism is determined to be disconnected, and commanding the disconnect mechanism to connect when the difference between the input speed of the disconnect mechanism and the output speed of the disconnect mechanism is below a threshold.
According to another aspect of the present disclosure, a vehicle may include a first electric machine and a second electric machine. The first electric machine may be engageable with the ground through a multi-speed transmission. The second electric machine may be engageable with the ground at a fixed speed ratio.
According to another aspect of the present disclosure, the vehicle may also include an engine and a third electric machine connected to the engine and electrically connected to the first electric machine and the second electric machine.
According to another aspect of the present disclosure, the vehicle may also include a controller configured to command the first electric machine and the second electric machine based on a position of a user input.
According to another aspect of the present disclosure, the controller may also be configured to command at least one of the first electric machine and the second electric machine based on an efficiency of at least one of the first electric machine and the second electric machine.
According to another aspect of the present disclosure, the vehicle may also include a controller configured to command at least one of the first electric machine and the second electric machine based on a temperature of at least one of the first electric machine, the second electric machine, and the multi-speed transmission.
According to another aspect of the present disclosure, the controller may also be configured to command at least one of the first electric machine and the second electric machine based on a thermal headroom of at least one of the first electric machine, the second electric machine, and the multi-speed transmission.
According to another aspect of the present disclosure, the vehicle may also include a controller configured to command at least one of the first electric machine and the second electric machine based on an available torque of at least one of the first electric machine and the second electric machine.
According to another aspect of the present disclosure, the multi-speed transmission may be engageable with the ground through a clutch and the controller may be configured to disconnect the clutch when the first electric machine is not exerting torque.
The above and other features will become apparent from the following description and accompanying drawings.
The detailed description of the drawings refers to the accompanying figures in which:
a-7c are graphs generally illustrating the efficiency of an electric machine generating rimpull through a multi-speed transmission as a function of vehicle speed for three different speed ratios.
The vehicle may be any vehicle with a powertrain and any number of wheels, tracks, or other ground engaging components, such as a construction or forestry vehicle. Vehicle 100 is illustrated as a wheel loader and vehicle 200 is illustrated as an articulated dump truck, but the vehicle may also be, to list just a few examples, a backhoe loader, crawler, excavator, feller buncher, forwarder, harvester, knuckleboom loader, motor grader, scraper, skidder, skid steer loader, track loader, or off-highway truck (such as a mining truck).
Controller 104 may control the powertrain of vehicle 100 or vehicle 200. Controller 104 is in communication with sensors, controllers, and operator inputs such that it may send electrical signals to, or receive electrical signals from, such other components. Controller 104 may communicate with the sensors, controllers, and operator inputs in a number of manners, including through radio transceivers, a wiring harness, or through a Controller Area Network (CAN), an electrical bus intended to transmit such communications. Controller 104 may sense operator inputs (e.g., switch positions, pedal positions), sense the state of vehicle components (e.g., engine speed, transmission gear, clutch engagement), determine component performance (e.g., engine power output, drivetrain power output), command components (e.g., command a torque output from an electric machine, shift the transmission to a different gear, disconnect clutches), and send messages to the operator, to name but a few operations which controller 104 may perform.
Engine 302, for example a diesel engine, connects to first generator 306 and second generator 308 through engine gearbox 304. As used herein, “connect,” and conjugations thereof, comprises connections through which mechanical power may be transmitted, including both direct connections and indirect connections which include intermediate components. As used herein, “electrically connect,” and conjugations thereof, comprises connections through which electrical power may be transmitted, including both direct connections and indirect connections which include intermediate components. First generator 306 electrically connects to electrical bus 310 and may generate electric power for, or draw electric power from, electrical bus 310. Second generator 308 also electrically connects to electrical bus 310 and may generate electrical power for, or draw electrical power from, electrical bus 310. First generator 306 and second generator 308 may be operated in tandem, for example each generating the same amount of electrical power, or they may be operated independently, for example first generator 306 generating electrical power while second generator 308 generates no power. Engine 302 may indirectly connect to engine gearbox 304 through other components, such as a flywheel, coupler, or shaft. Engine gearbox 304 may serve multiple functions. It may provide mounts to aid in connecting multiple components to engine 302, such as first generator 306, second generator 308, hydraulic pumps, and other components. Such mounts may be positioned to improve the overall packaging of powertrain 300. Engine gearbox 304 may also be designed so its mounts rotate faster or slower than engine 302, or rotate in the opposite direction. This may be desirable when the maximum speed of first generator 306 or second generator 308, for example 10,000 rotations per minute (RPM), is greater than the maximum speed of engine 302, for example 2,500 RPM. Alternatively, first generator 306 and second generator 308 may be directly connected to engine 302 (see
The term gearbox, when used herein, refers to devices and methods known in the art for transferring, splitting, combining, or altering mechanical force, particularly torsional forces, including those that can create a speed ratio between an input and an output (e.g., the ratio of the rotational speed of an input to the rotational speed of an output). A gearbox is not limited to mechanical gears, and may include combinations of gear systems (e.g., bevel, crown, helical, hypoid, spur), hydraulic systems (e.g., pumps, motors), and continuously variable systems (e.g., variable diameter pulleys, toroids, cones), to name just a few known methods for transferring, splitting, combining, or altering mechanical force.
Although first generator 306 and second generator 308 are referred to as “generators” and first motor 312 and second motor 314 are referred to as “motors” for simplicity, each may be an electric machine capable of operating as a generator to convert mechanical energy into electrical energy and a motor to convert electrical energy into mechanical energy. For example, when vehicle 100 is accelerating, first generator 306 and second generator 308 may operate as generators to convert mechanical energy from engine 302 into electrical energy on electrical bus 310, and first motor 312 and second motor 314 may operate as motors to convert this electrical energy into mechanical energy to provide motoring rimpull (i.e., rimpull tending to propel the vehicle) to wheels 102. When vehicle 100 is decelerating, first motor 312 and second motor 314 may operate as generators to convert mechanical energy from wheels 102 into electrical energy on electrical bus 310, and first generator 306 and second generator 308 may operate as motors to convert this electrical energy into mechanical energy to rotate engine 302 or other components connected to it, and thereby provide retarding rimpull (i.e., rimpull tending to retard the vehicle), a technique which may be referred to as regenerative braking. As used herein, “rimpull” means the tractive force exerted by the vehicle on the ground, for example 1,200 N in sum exerted through wheels 102, and includes both motoring and retarding rimpull. First generator 306, second generator 308, first motor 312, and second motor 314 may each be any number of AC or DC electric machine types, for example induction, synchronous, shunt, permanent magnet, or switched reluctance, to name but a few types of electric machines.
First generator 306, second generator 308, first motor 312, and second motor 314 may be controlled, for example through power electronics, to suit the needs of the powertrain 300. Power electronics are not shown in
Electrical bus 310 transmits electrical power between first generator 306, second generator 308, first motor 312, and second motor 314. Electrical bus 310 thereby electrically connects first generator 306, second generator 308, first motor 312, and second motor 314, either directly, or indirectly through power electronics or other components controlling the electric machines or conditioning their electrical input and output. The design of electrical bus 310 depends on the type of electric machines used for powertrain 300, and may be comprised, for example, of two conductors for DC electric machines (some applications may use an electrical path through the vehicle chassis) or three conductors for three-phase electric machines. Alternatively, multiple electrical busses may be used to connect the generators and the motors, such as using a separate electrical bus for each generator-motor pair (see
Driveshaft gearbox 320 is connected to driveshaft 322, clutch 318, and second motor 314. Driveshaft gearbox 320, like engine gearbox 304, may serve multiple functions. It may provide mounts to aid in connecting multiple components to driveshaft 322, such as clutch 318, second motor 314, hydraulic pumps, parking brakes, and other components. Such mounts may be positioned to improve the overall packaging of powertrain 300, such as to bridge a drop from where these components are located down to driveshaft 322 (sometimes referred to as a “dropbox” in such applications). Driveshaft gearbox 320 may also be designed to provide a speed ratio between its mounts and driveshaft 322. This may be desirable when the operating rotational speed ranges of transmission 316 and second motor 314 are different than that of driveshaft 322. Alternatively, clutch 318 and second motor 314 could be directly connected to driveshaft 322.
First motor 312 is connected to the input of transmission 316. The output of transmission 316 is connected to differentials 324, axles 326, and wheels 102 through disconnect mechanism clutch 318, driveshaft gearbox 320, and driveshaft 322. Transmission 316 selectively provides multiple speed ratios, such as three forward speed ratios in one embodiment (see
Driveshaft 322 may be connected, including selectively connected, to differentials 324. Differentials 324 may comprise any number of well-known differential types, including open, limited slip, and locking, and may comprise any number of features, including a disconnect mechanism allowing the differential to be selectively disconnected from driveshaft 322, it being understood that it would be well within the skill of one of ordinary skill in the art to utilize these differential types or provide these features without undue experimentation. Differentials 324 are connected to axles 326, on which are mounted wheels 102. Differentials 324 may also contain additional components, such as final drives, to achieve the desired total speed ratio between first motor 312 and second motor 314 and wheels 102.
Clutch 318 allows transmission 316 to be selectively connected to driveshaft gearbox 320. Clutch 318 may comprise any number of suitable clutch types, including friction, dog, and hydraulic, it being understood that it would be well within the skill of one of ordinary skill in the art to utilize these clutch types without undue experimentation. When clutch 318 is connected, transmission 316 is connected to driveshaft gearbox 320 and first motor 312 may thereby exert torque on wheels 102 and engage the ground at a total speed ratio determined at least in part by the speed ratio of transmission 316. When clutch 318 is disconnected, transmission 316 is not connected to driveshaft gearbox 320, is not engaged with the ground, and may instead rotate freely or cease rotational motion. Clutch 318 thereby allows transmission 316 and first motor 312 to be selectively disconnected from driveshaft 322 and wheels 102 and selectively engaged with the ground, which may be useful in multiple scenarios. Clutch 318 may be disconnected when the non-transmission motor(s) is able to provide sufficient motoring or retarding rimpull for vehicle 100, thereby allowing first motor 312 and transmission 316 to cease rotation. This may be useful to eliminate parasitic (sometimes referred to as “windage”) losses incurred by the rotation of transmission 316 and first motor 312, and may allow powertrain 300 to motor or retard vehicle 100 more efficiently than it could if both first motor 312 and second motor 314 were connected. In this disconnected state, first motor 312 and transmission 316 may also be used to store energy from electrical bus 310. First motor 312 can generate torque and increase the rotational speed of itself and transmission 316 and thereby store kinetic energy. To discharge such kinetic energy, motor 312 can retard the rotational speed of itself and transmission 316 and convert such kinetic energy into electrical energy on electrical bus 310. Clutch 318 may not be necessary if this disconnect feature is not desired (see
Clutch 318 may be designed to accommodate rotational speed differences across itself when it connects. Alternatively, first motor 312 may be commanded to target a rotational speed that synchronizes the rotational speeds across clutch 318 to minimize the slippage and forces associated with closing clutch 318 while there is a rotational speed difference across it. This synchronization may allow for the usage of a less complex or more cost effective design for clutch 318 or extend the life of clutch 318. Perfect synchronization may not be required, and some embodiments may close clutch 318 as soon as the rotational speed difference across it is below a threshold, for example 100 RPM.
Right first motor 602 is connected to right final drive 608 through right transmission 606. Right second motor 604 and right transmission 606 are directly connected to right final drive 608. Alternatively, right transmission 606 could connect to right final drive 608 through a disconnect mechanism, such as clutch 318 (see
The electric machines connected to engine 302 (e.g., first generator 306 and second generator 308 in
In the embodiment illustrated in
Other alternative embodiments exist but are not depicted in
Controller 104 may receive signals from, and send signals to, components in
a-7c generally illustrate the net efficiency of a motor engaged with the ground through a multi-speed transmission (including the losses associated with the transmission), such as first motor 312 in
Using the requested rimpull from step 902 and the vehicle speed from step 904, controller 104 determines the available rimpull and efficiency from the transmission motor(s) in step 906. The transmission motor(s) are those motors engaged with the ground through a multi-speed transmission, such as first motor 312 in
In step 910, controller 104 selects the desired rimpull from the transmission motor(s) and the desired rimpull from the non-transmission motor(s). The method by which the amount of desired rimpull from each set of motor(s) is selected may vary depending on the embodiment and the current operating conditions for that embodiment. When motoring the vehicle, the available rimpulls and efficiencies from steps 906 and 908 may be used to select the combination of rimpulls which achieves the maximum overall powertrain efficiency or a target powertrain efficiency while producing the requested rimpull sensed in step 902. Some embodiments may include a feature to increase rimpull from the non-transmission motor(s) at the time the transmission undertakes a shift to mitigate or eliminate any overall powertrain rimpull reduction associated with the transmission shift. Some embodiments may include a feature to produce less than the requested rimpull sensed in step 902 if it allows increased powertrain efficiency, which may be referred to as an eco-mode or economy mode. When retarding the vehicle, the combination of rimpulls with the lowest overall powertrain efficiency or a target powertrain efficiency (below the maximum efficiency) may be selected to minimize the energy which must be dissipated from electrical bus 310, such as through resistor grid 508, while producing the requested rimpull sensed in step 902. Alternatively, in step 910, controller 104 may select the maximum available rimpull from the motor(s) which engage the ground through more durable (or lower wear-cost, or more serviceable) components and select additional rimpull from the motor(s) which engage the ground through the less durable (or higher wear-cost, or less serviceable) components only if necessary to reach the requested rimpull sensed in step 902. Alternatively, in step 910, controller 104 may distribute rimpull between the two sets of motor(s) based on the thermal headroom available (i.e., how close a component through which the motor(s) engages the ground is to exceeding a desired temperature range), to keep the temperatures of drivetrain components within a desired range. Further, step 910 could include a function to actuate the service brakes (e.g., friction brake pads and discs located in axles 326) if the retarding rimpull is requested and there is no thermal headroom available, in order to achieve blended braking (i.e., a blend of service braking and regenerative braking) equal to the requested rimpull sensed in step 902.
Step 910 may also involve combinations of the above, such as selecting the desired rimpull from each set of motor(s) to maximize overall powertrain efficiency when motoring, selecting the desired rimpull from each set of motor(s) to minimize energy dissipation when retarding, increasing rimpull from the non-transmission motor(s) when the transmission is shifting to mitigate overall rimpull reduction, and modifying these rimpulls as necessary to keep the temperatures of drivetrain components, including the motors, multi-speed transmission, and other components, within a desired range. Control system 900 may be designed to function regardless of the direction of the rimpull requested, and may therefore be designed to optimize the powertrain when providing both motoring rimpull and retarding rimpull.
For example, when controlling powertrain 300 using control system 900 to achieve maximum overall powertrain efficiency, if the rimpull request sensed in step 902 can be produced entirely by second motor 314 at 95% efficiency or can be produced entirely by first motor 312 through transmission 316 at 85% efficiency in the second forward gear and 91% efficiency in the third forward gear, step 910 would result in all the rimpull being produced by second motor 314 and none of the rimpull being produced by first motor 312. As another example, if the rimpull request sensed in step 902 can be produced in part by second motor 314 at 80% efficiency, or can be produced entirely by first motor 312 through transmission 316 at 90% efficiency in the first forward gear, step 910 would result in all the rimpull being produced by first motor 312. As yet another example, if half the rimpull request sensed from step 902 can be produced by second motor 314 at 94% efficiency, all the rimpull can be produced by first motor 312 through transmission 316 in first forward gear at 87% efficiency, or half the rimpull can be produced by first motor 312 through transmission 316 in second forward gear at 91% efficiency, step 910 would result in half the rimpull being produced by second motor 314 and half the rimpull being produced by first motor 312 through transmission 316 in second forward gear.
After the desired rimpulls are selected in step 910, controller 104 in step 912 commands the non-transmission motor(s) (e.g., second motor 314, third motor 504, right second motor 604, left second motor 612) to exert the necessary torque to achieve the rimpull selected for the non-transmission motor(s) in step 910. The requested rimpull of the non-transmission motor(s) may be converted to the torque necessary from the non-transmission motor(s) by a number of methods well known in the art, including lookup tables or the usage of a common percent (e.g., requesting 50% of maximum rimpull converts to 50% of maximum motor torque). If the powertrain lacks clutch 318 or an equivalent disconnect between transmission 316 and wheels 102, controller 104 would perform step 920 next and would command the transmission motor(s) (e.g., first motor 312, first right motor 602, first left motor 610) to exert the torque necessary to achieve the rimpull selected for the transmission motor(s) in step 910. The requested rimpull of the transmission motor(s) may be converted to the torque necessary from the transmission motor(s) by a number of methods well known in the art, including lookup tables or the usage of a common percent (e.g., requesting 50% of maximum rimpull requires 50% of maximum motor torque).
Control system 900 synchronizes the two sides of the transmission clutch to minimize the forces it must accommodate when it goes from disconnected to connected, which may allow the usage of a smaller, lower cost, less complex clutch, or may extend the service life of the clutch chosen. Alternatively, step 922 could be eliminated if such a feature is not desired and the transmission clutch is capable of accommodating a significant difference in rotational speeds when it connects.
Although control system 900 is illustrated as a flowchart, the disclosure is not limited to such steps and the order of steps of presented, and it would be well within the skill of one of ordinary skill in the art to reorder, combine, or split many of the steps and achieve the same result.
While “rimpull” is used in this disclosure to characterize the ultimate tractive force output of each of the motors in the embodiments described herein, alternative embodiments may use alternate measure or measures. For example, control system 900 may instead utilize requested torque in step 902, available torques in steps 906 and 908, and select desired torques in step 910, which may involve less conversion between rimpull and torque for some embodiments.
As shown in embodiments powertrain 300, powertrain 400, powertrain 500, and powertrain 600, regenerative braking is possible and first motor 312, second motor 314, third motor 504, right first motor 602, right second motor 604, left first motor 610, and left second motor 612 may transmit energy onto electrical bus 310, first electrical bus 402, or second electrical bus 404. This energy may be used by first generator 306 or second generator 308 to transmit mechanical energy into engine 302 or other components connected to engine 302, such as hydraulic pumps, air conditioning compressors, fans, water pumps, and alternators. Further, battery 502 may be included in the powertrain to store energy on electrical bus 310. If the power generated by regenerative braking exceeds the total power consumption of the vehicle and the power which can be stored by battery 502, energy dissipation components such as resistor grid 508 may be installed (see
Although wheels 102 mounted on axles 326 are shown in the embodiments illustrated in
Increasing the maximum rimpull and power which a powertrain is capable of transmitting to the ground on which a vehicle rides may require redesigning the transmission to handle increased torque and power. The design of a new transmission, even if it is a redesign of an existing product, may entail considerable cost, time, and risk, and a number of such new transmissions may be necessary if a number of different sized vehicles are desired. To reduce the number of transmission designs required, it may be possible to use oversized transmissions for some vehicle sizes, but such a course of action may increase the cost and weight of the vehicles using the oversized transmissions.
The powertrains and associated methods disclosed herein may broaden the range of vehicle sizes covered by, for example, transmission 316 by making the powertrains more modular through the usage of additional motors engaged with the ground not through transmission 316. Transmission 316 may satisfy a range of power and torque requirements by its use, for example, without second motor 314, with a small second motor 314, with a large second motor 314, or with second motor 314 and third motor 504. The number and size of the generators in powertrains 300, 400, 500, and 600 may need to be adjusted to provide sufficient electrical power for the motor configuration selected.
The powertrains and associated methods disclosed herein may also broaden the range of vehicle sizes which may be powered by a limited number of motor designs. First motor 312 and second motor 314 could be directly connected to driveshaft gearbox 320 or driveshaft 322 without transmission 316 or clutch 318. Such a configuration requires the motors to be sized so as to provide the peak torque required by the powertrain at all speeds, which may result in large motors which are expensive, difficult to manufacture, and inefficient for the torque and speed ranges the motors will encounter in non-peak torque conditions. The addition of transmission 316 allows first motor 312 to be connected to driveshaft 322 at multiple speed ratios (see
The powertrains and associated methods disclosed herein may also increase the efficiency of vehicle 100 and vehicle 200. The powertrain configurations each contain at least two paths for torque to reach wheels 102, one of which travels through a multi-speed transmission (e.g., transmission 316) and one which does not. Each path may contain multiple motors (e.g., second motor 314 and third motor 504 in
As used herein, “based on” means “based at least in part on” and does not mean “based solely on,” such that it neither excludes nor requires additional factors.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is not restrictive in character, it being understood that illustrative embodiment(s) have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. Alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the appended claims.
Number | Date | Country | |
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61927129 | Jan 2014 | US |