Electric vehicles with energy recovery systems

Abstract

The invention relates to an electromechanical energy recovery system in an electric vehicle and a method for operating the same. The invention also relates to an electric vehicle comprising a device (10, 20, 30, 40, 70) for converting waste heat of at least one electric machine (50) and / or at least one energy storage device (60) of the electric vehicle (1) into mechanical and / or electrical energy.

Description

Technical Field

[0001] The present invention relates to an electromechanical energy recovery system in an electric vehicle and an operating method thereof. Background Art

[0002] In today's vehicles, electric rotary machines are used in various components. These machines are used almost exclusively to generate mechanical work. With the exception of belt starter generators and three-phase AC motors in hybrid transmissions / drive motors in electric vehicles, energy recovery is not possible.

[0003] Thermal energy is not used to recover energy for other applications in the vehicle. This potential energy is usually released to the environment as waste heat in any vehicle. Currently, there is only an attempt to store a certain amount of heat capacity to save vehicle heating power in winter. However, considering the power and efficiency of the electric drive, the potential for energy recovery is considerable.

[0004] DE 10 2014 019 657 A1 relates to a vehicle having at least one internal combustion engine, a waste heat recovery device, and a control unit for operating the waste heat recovery device. The waste heat recovery device is based on a thermodynamic cycle, the so-called Clausius Rankine cycle. A working medium is conveyed in a circulation loop. To convey the working medium, a pump is integrated into the circulation loop, which conveys the liquid working medium to an evaporator, where it evaporates. For this purpose, the evaporator is preferably connected to the exhaust system of the internal combustion engine. The evaporator can serve as a heat exchanger, absorbing heat from the exhaust gas of the internal combustion engine, whereby this heat causes the working medium to evaporate. The heated and evaporated working medium, which is at a relatively high pressure, is conveyed from the evaporator via a circulation loop to a fluid energy machine arranged in the circulation loop. In the fluid energy machine, the heated and evaporated working medium expands, extracting thermal energy from the working medium and converting it into mechanical energy. The fluid energy machine can be configured, for example, as a scroll expander, a reciprocating piston expander, or a turbine. In one embodiment, a generator is driven by a fluid energy machine, which is part of a waste heat utilization system designed as a waste heat generator. Additionally or alternatively, mechanical energy itself can also be used. The expanded steam is conveyed from the fluid energy machine to a condenser, which is also integrated into the circulation circuit. In the condenser, the steam is condensed, i.e., liquefied, and the liquid working medium is then conveyed back to the pump via the circulation circuit.

[0005] DE 10 2016 217 743 A1 discloses a system for an internal combustion engine in a vehicle, comprising a waste heat recovery system and a regeneration system. The waste heat recovery system has a circulation circuit for conveying a working medium. The circulation circuit comprises, in the direction of flow of the working medium, a feed fluid pump, an evaporator, an expander, and a condenser. The expander is mechanically connected to a generator. The regeneration system has an electric motor that can be connected to the crankshaft of the internal combustion engine via a transmission element. The generator and the electric motor are electrically connected to a common energy accumulator. The waste heat recovery system and the regeneration system have a common control logic.

[0006] DE 10 2010 007 911 A1 discloses a drive unit for a motor vehicle having an internal combustion engine coupled to an output shaft and a waste heat recovery system, by which at least a portion of waste heat discharged from the internal combustion engine and / or from an exhaust system connected downstream of the internal combustion engine is converted into electrical energy by means of a heat-driven energy converter, which can at least partially be supplied to at least one auxiliary consumer and / or an onboard electrical system of the motor vehicle. In addition to the waste heat recovery system, a further heat source is provided, by which heat can be supplied to the heat-driven energy converter. Summary of the Invention

[0007] Against this background, the object of the present invention is to provide a device and a method with which the energy efficiency of electric vehicles can be further improved.

[0008] According to the invention, this object is achieved by a device having the features of claim 1 and a method having the features of claim 9. Developments and improvements of the invention are apparent from the dependent claims, the description and the drawings.

[0009] The subject matter of the invention is an electric vehicle comprising a device for converting waste heat of at least one electric machine and / or at least one energy storage device of the electric vehicle into mechanical and / or electrical energy.

[0010] In one embodiment, the electric vehicle comprises a device for converting waste heat of at least one electric machine and / or at least one energy storage device of the electric vehicle into mechanical and / or electrical energy.

[0011] According to the present invention, waste heat generated by vehicle operation is used to generate gas pressure, enabling energy recovery. In one embodiment, a combination of a mechanical motor and an electric motor (combined generator) is installed in the vehicle. Mechanical drive can be achieved using waste heat from the drive motor or waste heat from an electrical energy storage device. The evaporation of a working medium with a low boiling point and high vapor pressure creates a pressure potential relative to the surrounding environment, which can be used to drive the motor.

[0012] In another embodiment, the vehicle employs a gas expansion turbine (expander) that utilizes the generated gas pressure to recover energy. The expander can provide mechanical assist torque for driving the vehicle and / or drive a generator to generate electrical energy for supplying the vehicle's storage and / or the vehicle's traction motor.

[0013] In another embodiment, the device for converting waste heat into mechanical and / or electrical energy comprises a combined generator comprising a gas-driven mechanical linear motor and an electric motor mechanically coupleable to the gas-driven mechanical linear motor.

[0014] The combined generator connects a mechanical linear motor (pressure chamber, piston, damping element, piston rod) via a clutch to an electric motor (stator, rotor) and via a flywheel to a common bearing device.

[0015] In one embodiment of the combined generator, the piston rod of a linear piston of a gas-driven mechanical linear motor is axially supported in a flywheel having a guide curve. The guide curve converts the linear motion of the piston rod into the rotational motion of the motor's rotor. The rotational motion and mechanical torque are generated by the piston stroke and the torsion of the guide curve.

[0016] The piston rod can be hollow for better cooling. This allows for active cooling in a separate cooling circuit, possibly with the motor, or passive cooling via a sodium filling, etc.

[0017] The combination of a mechanical linear motor and an electric drive allows for various applications. These can be achieved by using a clutch and a control unit:

[0018] Consume pure mechanical work in the form of linear motion,

[0019] Producing purely mechanical rotational motion,

[0020] Producing electrical energy (energy recovery),

[0021] By superimposing mechanical motion on the electric drive, additional torque is introduced to save electrical energy.

[0022] In one embodiment, the at least one energy storage device comprises at least one HV (high voltage) battery. In another embodiment, the at least one energy storage device comprises at least one fuel cell.

[0023] The combined generator requires a heating and cooling circuit, through which a vaporizable working medium circulates. In one embodiment, the combined generator has a separate first heating and cooling circuit, through which the vaporizable working medium circulates. Heat transfer from at least one electric motor (traction motor) and / or at least one energy storage device for electrical energy (e.g., a hybrid battery, fuel cell) occurs via a second cooling circuit, through which a liquid heat transfer medium (e.g., silicone oil) circulates. Heat exchange between the two circuits occurs via a heat exchanger / evaporator. After expansion work in the combined generator, the working medium condenses again and is supplied to the evaporator. A pressure accumulator is also conceivable for compensating for peak power, etc., in the first circuit. This depends on the system design and its requirements / purpose. Furthermore, there is the possibility of supplying thermal energy to the vehicle from an external source, so that the thermal energy can be converted into mechanical work and / or electrical energy within the vehicle and provided.

[0024] In another embodiment, a device for converting waste heat from at least one energy storage device and / or at least one electric motor of an electric vehicle into mechanical and / or electrical energy is integrated into a single heat transfer medium circuit, in which a vaporizable working medium circulates. Waste heat from at least one heat source, namely at least one electric motor (traction motor) and / or at least one energy storage device for electrical energy (e.g., a hybrid vehicle battery or fuel cell), is absorbed by a liquid working medium. The liquid working medium is supplied to an evaporator, evaporated, and supplied to a waste heat conversion device (e.g., a combined generator or expander). After expansion and work in the waste heat conversion device, the working medium is condensed again in a condenser and returned to one or more heat sources.

[0025] In one embodiment, the device for converting waste heat into mechanical and / or electrical energy comprises a circulation circuit in which a working medium circulates, the working medium having a boiling point of not more than 80° C. at 1013.25 hPa.

[0026] The working medium must have a boiling point at atmospheric pressure that allows the working medium to evaporate and an overpressure to build up at the temperature of at least one electric machine, i.e., the traction motor or motors of the electric vehicle, or at the temperature of at least one energy storage device for electrical energy, during normal operation of the electric vehicle. Typically, this temperature is below 100°C.

[0027] In principle, the working medium can be hydrocarbons, such as n-butane, n-pentane, isopentane, or neopentane; or fluorocarbons, such as 1,1,1,2-tetrafluoroethane (R134a), 1,1,1,3,3-pentafluoropropane (R245fa), or 2,3,3,3-tetrafluoropropylene (R1234yf). However, these compound media have certain disadvantages due to their flammability or their fluorine content. In one specific embodiment, the working medium is carbon dioxide. In another specific embodiment, the working medium is ethanol.

[0028] The calculation unit controls both the required cooling circuit and the combined generator. To this end, the usual measurement parameters: temperature, pressure, speed, are determined and adjusted via corresponding sensors.

[0029] In one embodiment, the computing unit is part of the integrated control system of the electric vehicle, which also has access to all sensor measurement data and navigation system data of the vehicle. This enables proactive control of the waste heat conversion system, which compensates for hysteresis in the overall system comprising one or two heat circuits, predicts and takes into account the expected waste heat during control, and also ensures that the required heat is provided for the anticipated heating demand.

[0030] The subject matter of the present invention also includes a method for operating an electric vehicle, wherein waste heat of at least one electric machine and / or at least one energy storage device of the electric vehicle is converted into mechanical energy and used to drive the electric vehicle and / or converted into electrical energy and supplied to at least one electric machine and / or at least one energy storage device of the electric vehicle.

[0031] In one embodiment of the method, as described above, the waste heat is used to evaporate the working medium, and the gaseous working medium drives the combined generator.

[0032] The device and method according to the invention make it possible to use the waste heat generated during operation of an electric vehicle to support the vehicle's drive by means of additional torque and / or to save or recover electrical energy. Further advantages and embodiments of the invention are apparent from the description and the accompanying drawings.

[0033] It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention is illustrated by way of example with reference to the drawings and will be described in further detail with reference to the drawings.

[0035] Figure 1An embodiment of an electric vehicle according to the present invention is shown;

[0036] Figure 2 One embodiment of a combined electrical generator for converting thermal energy into mechanical and / or electrical energy is shown. DETAILED DESCRIPTION

[0037] Figure 1 An embodiment of an electric vehicle 1 according to the present invention is schematically illustrated. Electric vehicle 1 includes a combined generator 10 for converting thermal energy into mechanical and / or electrical energy. Combined generator 10 is connected to a heat exchanger / evaporator 20 and a condenser 30 via pipes in a circulation loop 40, in which a vaporizable working medium circulates. Heat exchanger / evaporator 20 is connected to a heat transfer medium circulation loop 70, which removes heat from the electric vehicle's traction motor 50 and hybrid vehicle battery 60. In heat exchanger / evaporator 20, heat from the heat transfer medium circulating in heat transfer medium circulation loop 70 is used to evaporate the working medium circulating in circulation loop 40. The gaseous working medium is used in combined generator 10 to perform mechanical work and / or generate electrical current. After expansion and work in combined generator 10, the working medium is recondensed in condenser 30 and supplied to evaporator 20.

[0038] Figure 2 An embodiment of a combined generator 10 for converting thermal energy into mechanical and / or electrical energy is schematically shown. The combined generator 10 comprises a linear piston 110 with a piston rod 160, which is movably arranged in a pressure chamber 120. A regulating unit 200 regulates the flow of gaseous working medium into or out of the pressure chamber 120 (indicated by arrows in the figures). The damping element 130, for example, can be a damping volume or a mechanical spring that generates a restoring force when the linear piston 110 moves. The linear or radial movement of the piston rod 160 can be used to produce mechanical work via a system interface 300.

[0039] The combined generator 10 further comprises an electric machine with a stator 180 and a rotor 190. The supply 400 of electrical energy to the electric machine or the absorption of electrical energy 400 from the electric machine is achieved via electrical contacts (indicated by arrows in the drawing).

[0040] The piston rod 160 of the linear motor is axially supported in the flywheel 150 , which has a guide curve that generates a rotational movement of the rotor 190 during a linear movement of the piston rod 160 when the friction clutch 140 connects the flywheel 150 to the housing.

[0041] Combined generator 10 connects the mechanical linear motor (pressure chamber 120, piston 110, damping element 130, piston rod 160) to the electric motor (stator 180, rotor 190) via clutch 140 and to a common bearing via flywheel 150. Piston rod 160 is axially supported in flywheel 150 and guided via a guide curve. Rotational motion and mechanical torque can be generated by the stroke of piston 110 and the torsion of the guide curve.

[0042] When clutch 140 is open, the linear motion of piston rod 160 can be mechanically dissipated. Flywheel 150 cannot generate torque because it is not supported by the housing. When clutch 140 is closed, rotational motion of rotor 190 is generated. If the electric motor is operated as a generator, the torque is used to generate current. In an alternative variant, the electric motor is also used as a drive device, and the mechanical torques generated by the linear motor and the electric motor are superimposed on each other.

[0043] The piston rod 160 can be designed to be hollow for better cooling. The cavity 170 can be actively cooled in a separate cooling circuit, possibly with an electric motor, or passively cooled by sodium filling or the like.

[0044] A computing unit (not shown) controls both the required cooling circuit and the combination generator 10. For this purpose, the usual measured variables: temperature, pressure and rotational speed are determined and adjusted by corresponding sensors.

[0045] Reference Signs List

[0046] 1. Electric Vehicle

[0047] 10 Combined generator

[0048] 20 Heat exchanger / evaporator

[0049] 30 Condenser

[0050] 40 Working medium circulation loop

[0051] 50 motor

[0052] 60 HV battery

[0053] 70 Heat medium circulation loop

[0054] 110 linear piston

[0055] 120 Pressure Chamber

[0056] 130 damping element

[0057] 140 Friction clutch for connecting housing and flywheel

[0058] 150 Flywheel with guide curve

[0059] 160 piston rod

[0060] 170 cavity

[0061] 180 stator

[0062] 190 rotor

[0063] 200 adjustment units

[0064] 300 System interfaces for linear or radial motion

[0065] 400 Transmission or absorption of electrical energy.

Claims

1. An electric vehicle (1), comprising a device (10, 20, 30, 40, 70) for converting waste heat of at least one electric machine (50) and / or at least one energy storage device (60) of the electric vehicle (1) into mechanical and / or electrical energy, the device (10, 20, 30, 40, 70) for converting waste heat into mechanical and / or electrical energy having a combined generator (10), the combined generator comprising a gas-driven mechanical linear motor (120, 110, 130, 160) and a motor (180, 190) that can be mechanically coupled to the mechanical linear motor, wherein the piston rod (160) of the linear piston (110) of the mechanical linear motor (120, 110, 130, 160) is axially supported in a flywheel (150) having a guide curve, and the guide curve converts the linear motion of the piston rod (160) into the rotational motion of the rotor (190) of the motor (180, 190) that can be mechanically coupled to the mechanical linear motor, characterized in that The mechanical linear motors (120, 110, 130, 160) and the motors (180, 190) that can be mechanically coupled to the mechanical linear motors are connected via a friction clutch (140) and connected to a common support device via a flywheel (150). When the friction clutch (140) connects the flywheel (150) to the housing, the guide curve generates a rotational motion of the rotor (190) when the piston rod (160) moves linearly. When the friction clutch (140) is disconnected, the flywheel (150) cannot generate torque due to the lack of support from the housing.

2. The electric vehicle (1) according to claim 1, characterized in that The at least one energy storage device (60) comprises at least one high-voltage battery.

3. The electric vehicle (1) according to claim 1, characterized in that The at least one energy accumulator (60) includes at least one fuel cell.

4. The electric vehicle (1) according to any one of claims 1 to 3, characterized in that The device (10, 20, 30, 40, 70) for converting waste heat into mechanical and / or electrical energy has a circulation circuit (40) in which a working medium circulates, the working medium having a boiling point of not more than 80° C. at 1013.25 hPa.

5. The electric vehicle (1) according to claim 4, characterized in that The working medium is carbon dioxide.

6. The electric vehicle (1) according to claim 4, characterized in that The working medium is ethanol.

7. A method for operating an electric vehicle (1), wherein: The waste heat of at least one motor (50) and / or at least one energy accumulator (60) of the electric vehicle (1) is converted into mechanical energy and used to drive the electric vehicle (1), and / or converted into electrical energy and supplied to at least one motor (50) and / or at least one energy accumulator (60) of the electric vehicle (1), wherein the device (10, 20, 30, 40, 70) for converting waste heat into mechanical energy and / or electrical energy has a combined generator (10), which includes a gas-driven mechanical linear motor (120, 110, 130, 160) and an electric motor (180, 190) that can be mechanically coupled to the mechanical linear motor, wherein the piston rod (160) of the linear piston (110) of the mechanical linear motor (120, 110, 130, 160) is axially supported on the piston rod (160) of the linear piston (110) In a flywheel (150) having a guide curve, the guide curve converts the linear motion of the piston rod (160) into the rotational motion of the rotor (190) of the motor (180, 190) that can be mechanically coupled to the mechanical linear motor, characterized in that the mechanical linear motor (120, 110, 130, 160) and the motor (180, 190) that can be mechanically coupled to the mechanical linear motor are connected via a friction clutch (140) and connected to a common support device via the flywheel (150); when the friction clutch (140) connects the flywheel (150) to the housing, the guide curve generates the rotational motion of the rotor (190) when the piston rod (160) moves linearly; when the friction clutch (140) is disconnected, the flywheel (150) cannot generate torque due to the lack of support from the housing.

8. The method according to claim 7, characterized in that The waste heat is used to evaporate the working medium, and the gaseous working medium drives the combined generator (10) or the expander.

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