Transmission system for electric vehicles

Abstract

A transmission system for an electric vehicle is disclosed. The system comprises a gear box comprising gears and a lubricating fluid. A pump is provided for supplying and removing lubricating fluid from the gear box. Operation of the pump is controlled by a controller. A reservoir is provided for storing lubricating fluid. The controller is configured to control the pump such that a portion of the lubricating fluid is removed from the gear box when the vehicle is involved in a high acceleration event.

Description

Technical Field

[0001] This disclosure generally relates to the field of drivetrain systems for electric vehicles. Specifically, it relates to a lubricated drivetrain system for electric vehicles. Background Technology

[0002] In electric vehicles, the efficient use of electrical power is extremely important. A vehicle's drive system contains various components, and if any of these components cannot operate efficiently, the vehicle and its users may lose the range, time, and power associated with electric vehicle use that might otherwise be available. Electric vehicles typically rely solely on stored electrical power. Therefore, it is essential to convert electrical energy into propulsion power as efficiently as possible. Summary of the Invention

[0003] This application discloses a transmission system for electric vehicles that improves the efficiency of power transmission within the transmission system, thereby providing electric vehicles with increased range, operating time, and power. Attached Figure Description

[0004] The features, aspects, and advantages of the present invention will become apparent from the following description and the accompanying exemplary embodiments shown in the accompanying drawings, which are briefly described below.

[0005] Figure 1 This is a schematic block diagram of various components of an exemplary embodiment of the powertrain of an electric vehicle.

[0006] Figure 2 This is a schematic block diagram of various components of an exemplary embodiment of the powertrain of an electric vehicle.

[0007] Figure 3 It is a schematic block diagram of the various components used in the transmission system of electric vehicles.

[0008] Figure 4 This is a schematic end view of two gears of a gearbox coupled to a drive system according to various disclosed embodiments. Detailed Implementation

[0009] As disclosed herein, a drivetrain for an electric vehicle is provided. The vehicle includes a DC power source that supplies power to one or more propulsion motors. A transmission can be used to change the speed of the motor shafts to match the desired speed of the shafts driving the vehicle wheels. The DC power source in the electric vehicle may be the main battery of the electric vehicle.

[0010] Figure 1An exemplary electric vehicle 100 is shown, configured to be driven by a pair of propulsion motors 172, 174. The vehicle may include a rechargeable energy storage system 150 (e.g., a battery). The vehicle may also include an engine 120 to provide supplemental power. Engine 120 can generally refer to any device operable to increase power or range beyond the range associated with the power provided by battery 150. For example, engine 120 may be an internal combustion engine that consumes gasoline. Storage system 150 may be, for example (but not limited to), a high-voltage battery, such as a high-voltage lithium-ion battery pack. Operation of vehicle 100 may be driven by each power source and / or both. Vehicle 100 may include multiple electric motors / generators 172, 174, which may operate as drive motors that convert electrical power into rotational mechanical energy or as generators that convert rotational mechanical energy into electrical energy. Motors / generators are sometimes simply referred to as motors, but as described herein, they include the ability to be driven to generate electricity. Motors / generators may be electrically driven and coupled to engine 120 and storage device 150.

[0011] According to various embodiments, vehicle 100 includes a first motor / generator 172 that functions as a motor to drive the front wheels 110 of the vehicle. In regenerative braking mode, motor 172 can function as a generator to charge storage device 150. Vehicle 100 also includes a second motor / generator 174 (e.g., a rear-wheel drive (RWD) motor) that engages a drive shaft to rotate one or more rear wheels 110. One or more intermediate devices, such as a rear gearbox 144 and a rear differential 134, may be disposed between the second motor / generator 174 and the rear wheels 110. Similarly, vehicle 100 may include a front gearbox 142 and a front differential 132 located between the front motor / generator 172 and the front wheels 110.

[0012] Vehicle 100 may also include generator 124, which is driven by engine 120 and generates power for propulsion or for charging battery 150. As further described below, gearboxes 142, 144 may be single-speed or multi-speed gearboxes. Motor / generators 172, 174, 124 and battery 150 may be coupled to a common DC bus 155. In some embodiments, generator 124 and motor / generators 172, 174 may be AC ​​and electric conversion devices, such as inverters 162, 164, 166, which may be coupled between the motor generator and DC bus 155. Vehicle 100 may operate normally as a RWD vehicle, with the front wheels powered only when additional power or traction is required.

[0013] When the vehicle accelerates or increases energy consumption, the drive motor speed increases to deliver more power or energy to the wheels 110. The rotation of the motor can be reversed to provide regenerative braking, which provides the impression of downshifting the vehicle. This also generates energy that can be stored in the battery 150. Thus, in some embodiments, the vehicle 100 can actuate regenerative braking to decelerate the vehicle 100 when the brake actuator is activated, instead of decelerating the wheels with brake pads (not shown).

[0014] When a vehicle accelerates, the speed of the drive motor increases, causing the gearbox's operating efficiency to decrease due to the increased temperature and pressure of the lubricating oil within the gearbox. For example, efficiency decreases due to lubricating oil churning losses, frictional losses from rotating parts, and increased temperature (i.e., heat dissipation). The disclosed system reduces the oil level in the reservoir and adds oil to the gearbox during transient events. For example, the disclosed system provides a system that temporarily adds additional oil to the gearbox system during transient events (e.g., high acceleration events) to provide improved operating efficiency for the gears, bearings, and shafts located within the gearbox. The total amount of lubricating oil is distributed throughout all system components, including the reservoir, gearbox, pump, and connecting lines (e.g., pipes, conduits, etc.).

[0015] The disclosed innovative drivetrain achieves this efficiency improvement (or reduces the amount of lubricant lost due to lack) by temporarily adding a portion of the lubricating oil from the reservoir to the gearbox, thereby increasing gearbox efficiency during high acceleration events. This portion of the lubricating oil is relatively small in size or volume and depends on the dimensions of various components of the drivetrain, including, for example, the total amount of oil located in the gearbox. For example, when a high acceleration event is detected, the system preferably adds approximately 500 ml of lubricating oil from the reservoir to the gearbox. Alternatively, the amount of oil removed from the reservoir can be between 400 ml and 600 ml, or other suitable amounts. The normal amount of oil in the reservoir is likely to be approximately 2.5 liters. Therefore, in the event of a temporary high acceleration, the disclosed system removes approximately 20% of the oil volume from the reservoir and pumps it to the gearbox. Essentially all the oil removed from the reservoir is added to the gearbox. The amount of oil added may be between 15% and 25% of the total amount of oil used during standard operating conditions, depending on the dimensions of the gearbox, reservoir, and oil system.

[0016] In another example, the normal volume of oil in the reservoir can be 2.3 liters, and the system can be configured to transfer 500 ml of oil between the system and the gearbox. Therefore, the amount of oil transferred is approximately 22% of the system volume.

[0017] Figure 2 An alternative exemplary embodiment of a powertrain for an electric vehicle 200 is disclosed, which is configured to be driven by a pair of propulsion motors 272, 274. Although Figure 2Not shown, but the vehicle can be an all-wheel drive (AWD) vehicle and includes two or four motors and the ability to drive all four wheels simultaneously. Figure 2 The vehicle 200 shown in the image is in conjunction with Figure 1 The vehicles operate in the same basic manner and may include the same variations and embodiments of the systems and components described above.

[0018] Vehicle 200 may include a rechargeable energy storage system 200 (e.g., a battery). The vehicle may also include an engine 220 to provide supplemental power. Engine 220 can generally refer to any device operable to increase power or range beyond the range associated with the power provided by battery 250. For example, engine 220 may be an internal combustion engine that consumes gasoline. Storage system 250 may be, for example (but not limited to), a high-voltage battery, such as a high-voltage lithium-ion battery pack. Operation of vehicle 200 may be driven by each power source and / or both. Vehicle 200 may include multiple electric motors / generators 272, 274, which may operate as drive motors converting electrical power into rotational mechanical energy or as generators converting rotational mechanical energy into electrical energy. Motors / generators are sometimes simply referred to as motors, but as described herein, they include the ability to be driven to generate electricity. Motors / generators may be electrically driven and coupled to engine 220 and storage device 250.

[0019] According to various embodiments, vehicle 200 includes a pair of motors / generators 272, 274 for driving the front wheels 210 of the vehicle. In regenerative braking mode, motors 272, 274 can function as generators to charge storage device 250. Vehicle 200 may include a gearbox 240 located between motors / generators 272, 274 and the front wheels 210. Gearbox 240 may be configured as a separate gearbox (i.e., driving each wheel independently of a separate motor) or as an integrated gearbox that allows one of the two motors 272, 274 to drive both wheels 210 simultaneously.

[0020] Vehicle 200 may also include generator 224, which is driven by engine 220 and generates power for propulsion or for charging battery 250. As further described below, gearbox 240 may be a single-speed gearbox or a multi-speed gearbox. Motors / generators 272, 274, 224 and battery 250 may be coupled to a common DC bus 255. In some embodiments, generator 224 and motors / generators 272, 274 may be AC ​​and electric conversion devices, such as inverters 262, 264, 266, which may be coupled between the motor generator and DC bus 255. Vehicle 200 may operate normally as a FWD vehicle.

[0021] Figure 3An exemplary drivetrain 300 for use in electric vehicles such as those described above is disclosed. However, the innovative drivetrains disclosed herein are not limited to those exemplary embodiments of electric vehicles disclosed in this application.

[0022] The disclosed transmission system 300 includes an oil reservoir 350, which may be, for example, a dedicated oil tank for the transmission system or a housing shared with other systems using the same lubricating fluid. The system includes a pump 390 driven by a motor 392. The pump 390 can be of any suitable type, such as centrifugal, positive displacement (e.g., screw, piston, etc.). Screw pumps are preferred. The motor 392 includes a controller 394 for controlling the operation of the motor 392, and therefore also the operation of the pump 390. The pump can be operated to move lubricating fluid or lubricating oil toward or away from the component to be lubricated. The system may include various valves (not shown) to prevent oil from flowing in an undesirable direction when the pump is not operating.

[0023] The system may also include a heat exchanger 380 for cooling the lubricating fluid. The heat exchanger may include cooling fluid 384, which is carried through the heat exchanger to remove heat from the fluid or oil. The lubricating fluid is supplied to the gearbox 340, as further described below.

[0024] System 300 may include a controller 394 for motor 392. Controller 394 may be configured to send or receive data to or from other vehicle components. For example, controller 394 may be connected to a vehicle CAN bus 396 or other similar data-bearing system. CAN bus 396 may carry information from various vehicle components and sensors, such as inertial measurement units (e.g., acceleration sensors in the x, y, and / or z directions), vehicle speed sensors (e.g., wheel speed sensors), propulsion motor speed sensors, and steering angle sensors. CAN bus can transmit information about vehicle acceleration to the controller. Alternatively, controller 394 may be configured to determine vehicle acceleration based on information received from one or more of the aforementioned vehicle sensors.

[0025] The controller 394 can be configured to direct the motor 392 to drive the pump 390 to remove oil from the gearbox 340 when the vehicle acceleration is determined to be greater than a predetermined value. The first predetermined value can be in the range of 1.0 to 1.4 G. Preferably, a setpoint of 1.2 G is used for the predetermined value. The pump 390 operates only during the period of vehicle acceleration to remove a relatively small amount of oil from the gearbox. Once the vehicle acceleration returns to below a second predetermined value, the pump operates to return the removed oil from the reservoir 350 to the gearbox. The second predetermined value is preferably in the range of 3.5 G to 6.5 G. A preferred value for the second predetermined value is 0.5 G. Therefore, the lubrication of the gearbox components is not compromised because the amount of oil removed during high acceleration events is small, the duration of the oil reduction in the gearbox is short, and the pressure of the remaining oil in the gearbox is relatively high.

[0026] Figure 4 The internal structure of an exemplary gearbox 240 is shown. In an exemplary embodiment, the propulsion motors (172, 174, 272, 274) include drive shafts 241 that drive motor gears 242. Each motor gear 242 drives a larger gear 243, which is connected to a smaller gear 246 that engages a wheel gear 245, which is connected to a drive shaft 244 of each wheel. The drive shafts may alternatively be connected to a differential (132, 134). In alternative embodiments, the gearbox may include more gears, depending on the vehicle's usage (e.g., the gradient encountered, the maximum desired speed, etc.). Figure 4 The split gearbox shown is merely exemplary. In an alternative embodiment, the gearboxes may be internally cross-connected to allow one motor to drive two wheels.

[0027] As utilized herein, the terms “about,” “approximately,” “substantially,” and similar terms used in the subject matter of this disclosure are intended to have a broad meaning consistent with common and accepted usage by those skilled in the art to which the subject matter of this disclosure pertains. Those skilled in the art who read this disclosure will understand that these terms are intended to allow for the description and protection of certain features without limiting the scope of those features to the precise numerical ranges provided. Therefore, these terms should be interpreted as meaning that non-substantial and insignificant modifications and alterations to the described and claimed subject matter are considered to fall within the scope of this disclosure as set forth in the appended claims.

[0028] It should be noted that the term "exemplary" used herein to describe different embodiments is intended to indicate that such embodiments are possible examples, representations, and / or illustrations of possible embodiments (and this term is not intended to imply that such embodiments must be particular or best examples).

[0029] As used herein, the terms “connection,” “joint,” and similar terms refer to the direct or indirect connection between two components. Such a connection can be fixed (e.g., permanent) or movable (e.g., detachable or releasable). Such a connection can be achieved by integrally molding two components or two components and any additional intermediate components into a single monolithic structure, or by attaching two components or two components and any additional intermediate components to each other.

[0030] References to the position of elements herein (e.g., top, bottom, above, below, etc.) are used only to describe the orientation of the various elements in the accompanying drawings. It should be noted that the orientation of the various elements may differ according to other exemplary embodiments, and such differences are intended to be included within this disclosure.

[0031] It is important to note that the construction and arrangement of the drive systems and electric vehicles shown in the various exemplary embodiments are merely illustrative. While this disclosure describes only a few embodiments in detail, those skilled in the art who read this disclosure will readily understand that many modifications (e.g., variations in size, dimensions, structure, shape and proportion of various elements, parameter values, mounting arrangements, use of materials, color, orientation, etc.) are possible without substantially departing from the novel teachings and advantages of the subject matter described herein. For example, an element shown as a single piece may be constructed from multiple components or elements, the positions of the elements may be reversed or otherwise changed, and the nature and number of discrete elements or positions may be changed or different. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. Other substitutions, modifications, alterations, and omissions may also be made in the design, operating conditions, and settings of different exemplary embodiments without departing from the scope of the invention.

Claims

1. A transmission system for an electric vehicle, comprising: A gearbox, which includes gears and lubricating fluid; A reservoir for storing the lubricating fluid; as well as A pump for moving the lubricating fluid into and out of the reservoir, wherein the operation of the pump is controlled by a controller. The controller is configured as follows: The vehicle's current acceleration is determined based on information received from the propulsion motor speed sensor; In response to determining that the vehicle's current acceleration is greater than a first predetermined acceleration value, the operation of the pump is controlled such that when the vehicle's current acceleration is greater than the first predetermined acceleration value, a portion of the lubricating fluid is transferred from the gearbox to the reservoir; and In response to determining that the vehicle’s current acceleration has returned to a second predetermined acceleration value that is smaller than the first predetermined acceleration value, the operation of the pump is controlled so that a portion of the lubricating fluid is returned from the reservoir to the gearbox.

2. The transmission system according to claim 1, wherein, The controller is configured to continuously control the operation of the pump such that when the current acceleration of the vehicle is greater than the first predetermined acceleration value, a portion of the lubricating fluid is transferred from the gearbox to the reservoir.

3. The transmission system according to claim 2, wherein, The first predetermined acceleration value is 1.2G.

4. The transmission system according to claim 1, wherein, The controller is connected to a vehicle data communication bus, wherein the data communication bus transmits data relating to the condition of a plurality of vehicle components; and wherein the controller is configured to determine the current acceleration of the vehicle based on the condition of at least one of the plurality of vehicle components.

5. The transmission system according to claim 1, wherein, The portion of the lubricating fluid is less than 100 ml.

6. The transmission system according to claim 1, wherein, The portion of the lubricating fluid is approximately 50 ml.

7. The transmission system according to claim 1 further includes a motor for driving the pump.

8. The transmission system according to claim 7, wherein, The controller directly controls the operation of the motor, thereby controlling the operation of the pump.

9. A method of operating a transmission system for an electric vehicle, wherein, The system includes: a gearbox comprising gears and lubricating fluid; and a pump for transferring fluid into and out of a reservoir storing the lubricating fluid, the method comprising the following steps: The vehicle's current acceleration is determined based on information received from the propulsion motor speed sensor; In response to determining that the current acceleration of the vehicle is greater than a first predetermined acceleration value, the pump is operated such that when the current acceleration of the vehicle is greater than the first predetermined acceleration value, a portion of the lubricating fluid is transferred from the gearbox to the reservoir; and In response to determining that the vehicle’s current acceleration has returned to a second predetermined acceleration value that is smaller than the first predetermined acceleration value, the pump is operated so that a portion of the lubricating fluid is returned from the reservoir to the gearbox.

10. The method according to claim 9, wherein, Operating the pump to transfer a portion of the lubricating fluid from the gearbox to the reservoir includes: continuously operating the pump such that when the current acceleration of the vehicle is greater than the first predetermined acceleration value, the portion of the lubricating fluid is transferred from the gearbox to the reservoir.

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