Patent Application
20250091420
The present disclosure relates to an electric drive system with a higher voltage electric motor and a lower voltage electric generator.
Electric vehicles make use of electric drive units to generate motive power and provide an attractive alternative in terms of hydrocarbon emissions in relation to vehicles that solely rely on internal combustion engines for propulsion. Some vehicles have relatively high power demands. However, as a vehicle's power demand increases it may be more difficult to fulfill power demands of lower voltage devices in the vehicle. To elaborate, the power demands of some auxiliary systems is much lower than traction motors and particularly traction motors for larger vehicles with high power demands.
Some vehicle systems have included a higher voltage generator and a lower voltage generator. However, this type of system demands that the generators be driven by an external motor or internal combustion engine. Other attempts have been made to provide electrical power to lower voltage auxiliary systems via a separate lower voltage electrical system that includes a specific battery pack. However, the inventors have recognized several drawbacks with the use of a separate lower voltage electrical system with a dedicated battery pack. For instance, the space efficiency of the system is decreased and the likelihood of component degradation is increased in systems that utilize a lower voltage battery pack. Further, the use of a standalone lower voltage electrical system may demand additional maintenance and/or servicing, in some instances.
Facing the abovementioned issues, the inventors developed an electric drive system to at least partially overcome at least a portion of the issues. In one example, the electric drive system includes a gearbox. In such an example, the gearbox includes a first shaft rotationally coupled to a higher voltage electric motor and a second shaft rotationally coupled to a lower voltage electric motor-generator assembly. The electric drive system further includes an inverter that is electrically coupled to the higher voltage electric motor and an energy storage device. Further, in such an example, the lower voltage electric generator is configured to electrically couple to an auxiliary device. Using the lower voltage electric motor-generator assembly allows the auxiliary device to be effectively driven via a space efficient assembly. In such an example, a lower voltage energy storage device (e.g., a lower voltage battery) may be omitted from the system, which reduces system complexity and increases system compactness. Further, in one example, the lower voltage electric generator and motor assembly includes a lower voltage generator that is rotationally coupled to the second shaft and a lower voltage electric motor electrically coupled to the lower voltage generator and rotationally coupled to the auxiliary device. In this way, power is efficiently transferred to the auxiliary device.
Still further in one example, the electric drive system may additionally include a disconnect clutch which is configured to selectively disconnect the lower voltage electric generator and motor assembly from the second shaft. In this way, the lower voltage electric generator and motor assembly may be disconnected when auxiliary device operation is not desired, thereby increasing system efficiency.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The vehicle may be a passenger vehicle, a commercial vehicle, an on-highway vehicle, or an off-highway vehicle, in different examples. Specifically, in one use-case example, the EV 100 may be an off-highway vehicle. An off-highway vehicle may be a vehicle whose size and/or maximum speed precludes the vehicle from being operated on highways for extended durations. For instance, the vehicle's width may be greater than a highway lane and/or the vehicle top speed may be below the highway's minimum allowable or suggested speed, for example. Industries and their corresponding operating environments in which the off-highway vehicle may be deployed include construction, forestry, mining, agriculture, and the like.
In the vehicle example, the vehicle 100 includes a powertrain 102 with a gearbox 104 and a higher voltage electric motor 106. At least a portion of the gearbox 104, the higher voltage electric motor 106, and a lower voltage electric generator and motor assembly 130 discussed in greater detail herein, are included in an electric drive system 110.
The higher voltage electric motor 106 may be a higher voltage electric traction motor. The higher voltage electric motor 106 includes a rotor that electromagnetically interacts with a stator to drive rotation of a rotor shaft which is included in the rotor. The higher voltage electric traction motor may further include a housing, bearings coupled to the rotor shaft, and the like.
In the illustrated example, the higher voltage electric motor 106 is a multi-phase alternating current (AC) motor. However, other suitable types of higher voltage electric motors have been contemplated. Further, in the illustrated example, the higher voltage electric motor 106 is electrically coupled to a higher voltage inverter 112 (e.g., a higher voltage AC drive) via an AC electrical connection 114 (e.g., multiphase bus bars, wires, and the like). The higher voltage inverter 112 is designed to convert DC power to AC power and vice versa.
The higher voltage inverter 112 may receive electric energy from one or more higher voltage energy storage device(s) 116 (e.g., traction batteries, capacitors, combinations thereof, and the like). A DC electrical connection (as denoted via arrows 118) is formed between the higher voltage inverter 112 and the higher voltage energy storage device 116. The DC electrical connection 118 may specifically include a higher voltage DC bus and/or other suitable electrical comments for transferring electrical energy therebetween.
The higher voltage electric motor 106 is rotationally coupled (e.g., directly rotationally coupled) to a shaft 120 (e.g., an input shaft) in the gearbox 104. To elaborate, the higher voltage electric motor 106 is coupled to an end 122 of the shaft 120. The rotational coupling between the shaft 120 and the higher voltage electric motor 106 may be achieved via a splined interface, a sleeve, bolted flanges, combinations thereof, and the like.
The gearbox 104, in the illustrated example, is a single speed gearbox. However, the gearbox may be a multi-speed gearbox with clutches for shifting between different active gear ratios, in other examples. However, it will be understood the use of a single speed gearbox decreases the gearbox's complexity as well as the likelihood of component degradation, and increases the gearbox's space efficiency, if desired.
A gear 124 is fixedly coupled to the shaft 120 such that they rotate in unison. The gear 124 meshes with a gear 126 which is fixedly coupled to a shaft 128 (e.g., an intermediate shaft), in the illustrated example.
A lower voltage electric generator and motor assembly 130 is rotationally coupled to the shaft 128. To elaborate, a lower voltage generator 132 is rotationally coupled (e.g., directly rotationally coupled) to the shaft 128 at an end 134 of the shaft, in the illustrated example. In this way, the lower voltage assembly may be effectively incorporated into the gearbox. However, the lower voltage generator 132 may be coupled to the shaft in another suitable manner, in alternate examples. The lower voltage generator 132 is designed to convert rotational energy (transferred to the generator from the shaft) into electrical energy. As such, the generator may include a rotor and a stator that electromagnetically interact to provide this functionality.
In the illustrated example, the lower voltage electric generator and motor assembly 130 further includes a first lower voltage inverter 136 (e.g., a lower voltage generator drive). A lower voltage electrical connection 138 is established between the first lower voltage inverter 136 and the lower voltage generator 132. Bus bars, electrical wires, combinations thereof, and the like may be used to establish this electrical connection.
The first lower voltage inverter 136 may be electrically connected to a second lower voltage inverter 140 (e.g., a lower voltage motor drive) via an electrical connection 142 (e.g., a lower voltage DC bus and/or other suitable electrical components). Further, a lower voltage electric motor 144 may be electrically coupled to the second lower voltage inverter 140 via an electrical connection 146 (e.g., bus bars, electrical wires, combinations thereof, and the like). The lower voltage electric motor 144 includes a rotor and a stator.
In turn, the lower voltage electric motor 144 is rotationally coupled to an auxiliary device 148 via a mechanical connection 150. The auxiliary device 148 may be a hydraulic pump, a steering system, a parking brake system, combinations thereof, and the like. The lower voltage electric motor 144 may be incorporated into the auxiliary device 148, in one specific example. To expound, the lower voltage electric motor and the auxiliary device may be formed as one unit which may be housed in a common enclosure, for instance. In such an example, the auxiliary device and the lower voltage electric motor may be in the form of an electric pump, an electric parking brake, and the like.
A disconnect clutch 152 may further be included in the gearbox 104. The disconnect clutch 152 is configured to selectively rotationally decouple the shaft 128 from the lower voltage generator 132. The disconnect clutch 152 may be a dog clutch, in one example, or a friction clutch, in another example. Additionally, the disconnect clutch may be hydraulically, pneumatically, and/or electro-mechanically actuated.
The lower voltage electric generator and motor assembly 130 may function using electrical power in the range of 24-144 Volts (V), in one specific example. To expound, the lower voltage electric motor 144 may be supplied with electrical power in the range of 24-144 V (e.g., direct current voltage). On the other hand, the higher voltage electric motor 106 may function using electrical power which is greater than or equal to 400 V (e.g., direct current voltage). However, the higher and/or lower voltage components may be operated using other suitable voltages.
Another gear 154 may be fixedly coupled to the shaft 128. In the illustrated example, the gear 154 meshes with a gear 156 that is fixedly coupled to a shaft 158 (e.g., an output shaft). However, other geartrain architectures with a greater number of gears and/or an alternate gear layout have been envisioned. It will be appreciated, that the gears 124, 126, 154, and 156 may conceptually be included in a gear train 159.
The shaft 158 includes an output interface 160 at one end 162 and another output interface 164 at the opposite end 166. However, in alternate examples, the output shaft may include a single output interface or the output interface may be positioned in alternate suitable locations. The output interfaces 160 and 164 may be rotationally coupled to drive axle assemblies 168 as denoted via arrows 170. Shafts, joints, chains, belts, combinations thereof, and the like may be used to establish these mechanical connections. Each of the drive axle assemblies may include a differential, axle shafts (e.g., half shafts), and drive wheels, for instance.
Bearings may be coupled to each of the shafts in the gearbox to enable rotation thereof. To elaborate, bearings may be coupled to opposing sides of each of the gearbox shafts, in one specific example. However, other gearbox bearing arrangements may be used, in other examples. The gearbox 104 may include a housing 171 which may at least partially enclose the gearbox gears and the shafts.
The electric drive system 110 directly transfers power from the lower voltage generator 132 to the auxiliary device 148, in the illustrated example. In this way, the auxiliary device is efficiently driven by a lower voltage assembly. Further, in the illustrated example, a lower voltage battery has been omitted from the electric drive system. In this way, the complexity of the system is decreased and the space efficiency of the system is increased. However, in other examples, the vehicle may include a lower voltage energy storage device (e.g., lower voltage battery).
The vehicle 100 may further include a control system 190 with a controller 191 (e.g., a vehicle control unit (VCU)), as shown in
The controller 191 may receive various signals from sensors 195 coupled to various regions of the vehicle 100. For example, the sensors 195 may include a pedal position sensor designed to detect a depression of an operator-actuated pedal such as an accelerator pedal and/or a brake pedal, speed sensor(s) at the transmission input and/or output shaft, a motor speed sensor, and the like. An input device 198 (e.g., accelerator pedal, brake pedal, drive mode selector, gear selector, combinations thereof, and the like) may further provide input signals indicative of an operator's intent for system control.
Upon receiving the signals from the various sensors 195 of
An axis system is provided in
The method 200 illustrated in
Next at 204, the method includes judging if the lower voltage generator and motor assembly should be disconnected from the gearbox. This judgement may take into account auxiliary device power demand, generator temperature, motor temperature, generator speed, motor speed, and the like. To elaborate, if the auxiliary device power demand is less than a threshold value (e.g., near zero or approaching zero) it may be determined that the lower voltage generator and motor assembly should be disconnected. Conversely, if the auxiliary device power demand is greater than the threshold value, it may be determined that the mechanical connection between the gearbox and the lower voltage generator and motor assembly should be sustained.
If it is determined that the lower voltage generator and motor assembly should not be disconnected from the gearbox (NO at 204) the method moves to 206 where the method includes sustaining engagement of the disconnect clutch in the gearbox. For instance, pressure in an actuation piston in the clutch may be sustained, in one use-case example.
Conversely, if it is determined that the lower voltage generator and motor assembly should be disconnected from the gearbox (YES at 204) the method moves to 208 where the method includes disengaging the disconnect clutch. For example, pressure in an actuation piston in the clutch may be decreased, in one use-case example. Method 200 allows the gearbox's efficiency to be increased. However, as previously indicated, the disconnect clutch may be omitted from the electric drive system in certain architectures.
The technical effect of the electric drive system operating methods described herein is to increase gearbox operating efficiency.
The invention will be further described in the following paragraphs. In one aspect. an electric drive system is provided that comprises a gearbox including: a first shaft rotationally coupled to a higher voltage electric motor; and a second shaft rotationally coupled to a lower voltage electric generator and motor assembly; and an inverter electrically coupled to the higher voltage electric motor and an energy storage device; and wherein the lower voltage electric generator and motor assembly is configured to rotationally couple to an auxiliary device. In one example, the lower voltage electric generator and motor assembly may include: a lower voltage generator that is rotationally coupled to the second shaft; and a lower voltage electric motor electrically coupled to the lower voltage generator and rotationally coupled to the auxiliary device. In another example, the first shaft may be an input shaft. In yet another example, the second shaft may be an intermediate shaft. In yet another example, the electric drive system may further comprise an output shaft and a gear train which includes gears on the input shaft, the intermediate shaft, and the output shaft that mesh with one another. In yet another example, the electric drive system may further comprise a disconnect clutch configured to selectively disconnect the lower voltage electric generator and motor assembly from the second shaft. In yet another example, the system may include a controller with instructions that when executed, when a power demand from the auxiliary device is less than a threshold value, cause the controller to: disengage the disconnect clutch. In one example, the higher voltage electric motor may be a higher voltage traction motor. In yet another example, the electric drive system may be included in an all-electric vehicle. In yet another example, the all-electric vehicle may be an off-highway vehicle. In yet another example, the gearbox may be a single speed gearbox. In yet another example, the auxiliary device may be an electric pump, an electric actuator, an electric steering device, or an electric parking brake.
In another aspect, a method for operation of an electric drive system is provided that comprises transferring mechanical power from a higher voltage electric motor to a first shaft; and transferring mechanical power from a second shaft to a lower voltage electric generator and motor assembly; wherein the electric drive system includes: a gearbox comprising: the first shaft, the second shaft, the higher voltage electric motor, and the lower voltage electric generator; and an inverter electrically coupled to the higher voltage electric motor and an energy storage device; and wherein the electric generator and motor assembly is configured to rotationally couple to an auxiliary device. The method may further comprise, in one example, transferring electrical power from the lower voltage electric generator to the auxiliary device. The method may further comprise, in one example, disengaging a disconnect clutch which is coupled to the lower voltage electric generator and motor assembly and the second shaft. In one example, the first shaft may be an input shaft and the second shaft may be an intermediate shaft and wherein the electric drive system may further comprise an output shaft configured to rotationally couple to one or more axle assemblies. Further, in one example, a lower voltage generator in the lower voltage electric generator and motor assembly may generate a direct current (DC) voltage in a range of 24-144 volts (V).
In yet another aspect, an electric drive system is provided that comprises a gearbox including: an input shaft rotationally coupled to a higher voltage traction motor; and an intermediate shaft rotationally coupled to a lower voltage generator; an inverter electrically coupled to the higher voltage traction motor and an energy storage device; and wherein the lower voltage generator is electrically coupled to a lower voltage auxiliary motor; and wherein the lower voltage auxiliary motor is configured to rotationally couple to an auxiliary device. Further in one example, the inverter may be configured to supply electrical power to the higher voltage traction motor at a voltage that is greater than 400 volts (V); and the lower voltage electric generator may generate a direct current (DC) voltage in a range of 24-144 volts (V). Still further, in one example, the electric drive system may be included in an all-electric off-highway vehicle; and the gearbox may be a single speed gearbox.
In another representation, an electric gearbox is provided that includes a higher voltage traction motor which receives electrical power from a higher voltage battery via a higher voltage inverter and a lower voltage generator and motor assembly that drives an auxiliary device and does not includes a lower voltage battery.
Note that the example control and estimation routines included herein can be used with various system (e.g., powertrain) configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other system hardware in combination with the electronic controller. As such, the described actions, operations, and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the vehicle and/or powertrain control system. The various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the examples described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. One or more of the method steps described herein may be omitted if desired.
While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive. As such, the configurations and routines disclosed herein are exemplary in nature, and that these specific examples are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to powertrains that include different types of propulsion sources including different types of traction motors, internal combustion engines in some instances, transmissions, and the like. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. Further, components that are
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
