DE102015201405A1 - Motor vehicle and method for warming up a fuel cell system of a motor vehicle - Google Patents

Abstract

The technology disclosed herein relates to a motor vehicle having a fuel cell system 100 and at least one electric drive machine 200. During a warm-up phase ta of the fuel cell system 100, the electrical energy provided by the fuel cell system 100 during the warm-up phase ta is at least partially present in the engine 200 and / or consumed in at least one actuator 310 of the engine 200.

Description

The technology disclosed herein relates to a motor vehicle and a method of warming up a fuel cell system of a motor vehicle.

Fuel cell systems for mobile applications such as motor vehicles are known in the art. In its simplest form, a fuel cell is an electrochemical energy converter that converts fuel and oxidant into reaction products, producing electricity and heat. For example, hydrogen is used as the fuel and air or oxygen as the oxidizing agent in such a fuel cell. The reaction product of the reaction in the fuel cell is, for example, water. The gases are fed into corresponding diffusion electrodes, which are separated by a solid or liquid electrolyte.

When operating fuel cells in particular, the cold start (start at an ambient temperature of 0 ° C to 25 ° C) and the frost start (start at an ambient temperature below 0 ° C) is problematic. For example, at low temperatures, the molecules of the catholyte and the ions traversing the separator have a comparatively low kinetics. This leads to the polarization curves having lower values during a cold start than during a warm start. Thus, the fuel cell system can be operated less efficiently at low temperatures. For this reason, there is a need to bring the fuel cell system as soon as possible to an operating temperature at which the system has a better efficiency.

From the DE 10 2007 054299 A1 For example, it is known to provide a cooling system for a fuel cell with an electric heater for heating the coolant.

It is an object of the technology disclosed herein to reduce or eliminate the disadvantages of the prior art solutions. In particular, it is an object of the technology disclosed herein to bring a fuel cell to its operating temperature quickly and efficiently. The object (s) is / are solved by the subject matter of claim 1. The dependent claims are preferred embodiments.

The technology disclosed herein relates to a motor vehicle having a fuel cell system. A fuel cell system according to the technology disclosed herein may include at least one fuel cell and the peripheral system components (balance-of-plant components or BOP components) that may be used in the operation of the at least one fuel cell. A fuel cell comprises an anode and a cathode, which are separated in particular by an ion-selective separator. The anode has a supply for a fuel to the anode. In other words, during operation of the fuel cell system, the anode is in fluid communication with a fuel reservoir. Preferred fuels for the fuel cell system are: hydrogen, low molecular weight alcohol, biofuels, or liquefied natural gas. The cathode has, for example, a supply of oxidizing agent. Preferred oxidizing agents are, for example, air, oxygen and peroxides. The ion-selective separator can be designed, for example, as a proton exchange membrane (PEM). Preferably, a cation-selective polymer electrolyte membrane is used. Materials for such a membrane include Nafion ^®, Flemion ^® and Aciplex ^®. For simplicity's sake, a system with a fuel cell is often discussed.

The motor vehicle further comprises at least one electric traction working machine (hereinafter and in the claims, the term "prime mover" is used to simplify both terms). The prime mover is used to drive the vehicle and can preferably be operated by motor and generator. The prime mover is electrically conductive u. a. connected to the fuel cell system. The prime mover is also preferably electrically connected to a high-voltage battery.

The motor vehicle may further comprise at least one control device which controls at least one of the following components: the fuel cell system, the at least one prime mover, and / or at least one actuator of the prime mover.

The motor vehicle or the control device may be configured such that during a warm-up phase of the fuel cell system, the electrical energy that is provided by the fuel cell system during the warm-up phase is consumed or converted at least partially in the prime mover and / or in the at least one actuator of the prime mover , In particular, the energy provided by the fuel cell system is consumed or converted without causing at least one drive wheel to move the motor vehicle in motion. Preferably, the energy provided is at least partially converted into thermal energy in the engine and / or in the at least one actuator of the engine.

The warm-up phase is the phase in which the fuel cell system of the motor vehicle is heated to the (optimal) operating temperature. The warm-up phase begins with the activation of the fuel cell system and ends with the reaching of the operating temperature, from which the driving operation of the motor vehicle from the vehicle or a control is permitted.

Particularly preferably, the warm-up phase of the fuel cell is activated before the ignition key or the starter button is actuated. For example, the warm-up phase can be initiated by a radio signal or by a timer. In one embodiment, the driver may, for example, start the warming up of the fuel cell system via an appropriate software of a mobile telephone. Alternatively, the warm-up phase may begin with the signal to unlock the central lock.

The at least one actuator of the drive machine is preferably at least one of the following actuators: circuit breaker, contactor, soft starter, variable transformer, variable resistor, AC / AC power controller, DC and / or inverter, DC-DC converter and / or inverter. The actuator of the prime mover is used to connect or disconnect the energy flow to the electric drive machine. In many cases, the actuator is used to control or regulate this energy flow and is used to implement various operating conditions, such as start-up, speed setting and braking. The construction and use of actuators for controlling the flow of energy is well known. Actuators are designed according to the electric drive machine and the required control quality. The at least one actuator may be part of the power electronics, for example.

The basic idea of the technology disclosed here is to generate a lot of self-heat in the fuel cells of the fuel cell system during the warm-up phase. For this purpose, according to the technology disclosed here, the fuel cell system is operated at high power and poor efficiency. However, the energy provided by the fuel cells must then also be consumed. For this purpose, other auxiliary consumers, such as. Interior temperature, rear window heating, cooling circuit heater, etc. are not enough. According to the technology disclosed herein, it is now proposed to consume or convert the energy provided by the fuel cell system during the warm-up phase in the electric drive machine or in its actuator (s). The electric drive machines are used to drive the motor vehicle and are designed accordingly large. For ordinary motor vehicles, for example, prime movers with an output of about 30 kW to about 300 kW can be used. Assuming an efficiency of approx. 95%, losses of approx. 1.5 kW to 15 kW can be achieved in these components. Since these components are installed in the vehicle anyway, so additional consumers can be used during the warm-up, without requiring additional space is required. Most hardware components are present anyway, so that the manufacturing costs are not or only slightly increase.

In addition to the consumption of electrical energy during the warm-up phase, it is of course also possible to store the energy provided by the fuel cell system in a high-voltage storage, for example a high-voltage battery or in supercapacitors.

In principle, any electric drive machine and any actuator suitable for this purpose can be used. Particularly preferably, the at least one actuator is a converter and the at least one drive machine is a three-phase machine, in particular a permanent-magnet synchronous machine.

Preferably, the electric drive machine or the at least one actuator are controlled such that on the drive shaft of the electric drive machine no or only a small drive torque is generated. The low drive torque of the electric drive machine is so small that the at least one drive wheel of the vehicle does not set the motor vehicle in motion. In other words, the motor vehicle stays in place during the warm-up phase. For example, the inertia of the drive train connected to the shaft of the electric drive machine can be so great that the torque of the electric drive machine is insufficient to set the rotor of the electric drive machine in motion. The counter-torque to the low drive torque can alternatively or additionally be applied by a parking brake.

The electric drive machine can be controlled by the controller and the actuator such that the electric drive machine is used as a resistive and inductive load.

Preferably, at least during the warm-up phase, a periodic intermittent voltage is applied to the electric drive machine, in particular a periodic pulse voltage. For example, a periodic intermittent operation may be a series of identical voltage pulses sized such that, due to the currents flowing, the motor does not reach the thermal limit at which the insulation of the motor winding fails.

Further preferably, the periodic intermittent voltage is designed such that the drive motor is brought into a vibrating state.

In particular, the intermittent voltage can be designed in such a way or the drive machine can be controlled in such a way that a rotor of the drive machine is not set in rotation in the warm-up phase. In particular, the intermittent voltage can be designed in such a way or the drive machine can be controlled such that a rotor of the drive machine in the warm-up phase performs a pendulum motion. Preferably, the pendulum motion is such that the at least one drive wheel of the motor vehicle is not set in motion by this oscillating movement.

The at least one fuel cell of the fuel cell system may be arranged in the same cooling circuit as the at least one electric drive machine and / or the at least one actuator. For example, it may be a liquid-cooled converter and / or a liquid-cooled drive machine. Preferably, the prime mover and / or the actuator are arranged at least during the warm-up phase upstream of the at least one fuel cell in the same cooling circuit. Thus, the heat energy generated during the warm-up phase in the electric drive machine and / or in the inverter can be used to heat the fuel cell system. Thus, the warm-up time of the fuel cell system can be further reduced.

• – Bereitstellen von elektrischer Energie durch ein Brennstoffzellensystem während einer Aufwärmphase des Brennstoffzellensystems, und
• – Verbrauchen bzw. Umwandeln von zumindest einem Teil der elektrischen Energie in einer Antriebsmaschine und/oder in einem Stellglied der Antriebsmaschine, ohne dass ein Antriebsdrehmoment auf einen der Fahrzeugreifen übertragen wird, insbesondere ohne dass dadurch mindestens ein Antriebsrad das Kraftfahrzeug in Bewegung versetzt.

The technology disclosed herein further includes a method of warming up a fuel cell system of a motor vehicle, particularly a fuel cell system, as disclosed herein. The method comprises the steps:

• Providing electrical energy through a fuel cell system during a warm-up phase of the fuel cell system, and
• Consuming or converting at least part of the electrical energy in a drive machine and / or in an actuator of the drive machine, without a drive torque is transmitted to one of the vehicle tires, in particular without thereby at least one drive wheel, the motor vehicle in motion.

The technology disclosed here will now be explained in more detail with reference to the figures. Show it

1 a schematic structure of a motor vehicle, and

2 the current and voltage curve in the electric drive machine.

In 1 shown is the fuel cell system 100 with a fuel cell 110 , which has a DC / AC converter with an electric drive machine 200 connected is. The energy flow from the fuel cell system 100 to the electric drive machine 200 is via the actuator 310 , here a converter 310 , regulated or controlled. The control device 300 is designed here to regulate or control the aforementioned components. Of course, it is possible that a plurality of decentralized control devices are used instead of a superordinate control device. During the warm-up phase ta is via the actuator 310 a pulse voltage Ua (cf. 2 ) to the engine 200 created. The pulse voltage Ua is dimensioned such that the electric drive machine 200 gives no or only a small moment, which is not sufficient to put the motor vehicle in motion.

2 shows the intermittent voltage Ua over the time t. During the warm-up phase ta is located on a stator winding of the electric drive machine 200 the intermittent voltage Ua. Depending on the design of the engine 200 For example, the intermittent voltage Ua may have a positive sign or a negative sign. Along with the intermittent voltage Ua is a pulsating current Ia. In this case, the intermittent voltage Ua or the pulsating current Ia is dimensioned such that it does not come to the thermal overload of the motor winding and no or only a small torque is transmitted to the drive train. The electric drive machine may be, for example, a three-phase motor. A winding string can then be viewed as a simplified LR resonant circuit. The electrical resistance R and the inductance L of the drive winding are known. By selecting an appropriate time constant τ based on the inductance L and the electrical resistance R, the maximum current Ia can thus be limited, without resulting in thermal overload or excessive torque being generated at the shaft.

Preferably, the individual strands of the three-phase drive machine are driven in such a way that the rotor carries out a periodic oscillating movement about a zero position. For this purpose, for example, the individual phase voltages Uai of the individual phase windings i can be varied with respect to their phase position and their drive times. Preferably, the pendulum movement is so small that it does not lead to a movement of the entire vehicle.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007054299 A1 [0004]

Claims (9)

Motor vehicle comprising a fuel cell system ( 100 ) and at least one electric drive machine ( 200 ), wherein during a warm-up phase (t _a ) of the fuel cell system ( 100 ) the electrical energy generated by the fuel cell system ( 100 ) is provided during the warm-up phase (t _a ), at least partially in the prime mover ( 200 ) and / or in at least one actuator ( 310 ) of the prime mover ( 200 ) is consumed. Motor vehicle according to claim 1, wherein the at least one actuator ( 310 ) is an inverter, and wherein the at least one prime mover ( 200 ) a three-phase machine ( 200 ). Motor vehicle according to claim 1 or 2, wherein on the prime mover ( 200 ) At least during the warm-up phase (t _a ) a periodic exposure voltage (U _a ) is applied. Motor vehicle according to one of the preceding claims, wherein the drive machine ( 200 ) is driven such that a rotor of the prime mover ( 200 ) is not rotated or performs a pendulum motion. Motor vehicle according to one of the preceding claims, wherein the at least one fuel cell ( 110 ) of the fuel cell system ( 100 ) is arranged in the same cooling circuit as the at least one electric drive machine ( 200 ) and / or the at least one actuator ( 310 ). Method for warming up a fuel cell system ( 100 ) of a motor vehicle, comprising the steps of: - providing electrical energy through a fuel cell system ( 100 ) during a warm-up phase (t _a ) of the fuel cell system ( 100 ), and - Consumption of at least part of the electrical energy in an engine ( 200 ) and / or in an actuator ( 310 ) of the prime mover ( 200 ). Method according to claim 6, wherein on the drive machine ( 200 ) At least during the warm-up phase (t _a ) a periodic exposure voltage (U _a ) is applied. A method according to claim 6 or 7, wherein the prime mover ( 200 ) is controlled such that a rotor ( 210 ) of the prime mover ( 200 ) is not rotated or performs a pendulum motion. Method according to one of claims 6 to 8, wherein at least one fuel cell ( 110 ) of the fuel cell system ( 100 ) is arranged in the same cooling circuit as the at least one electric drive machine ( 200 ) and / or the actuator ( 310 ).

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