DE10359486A1 - Device for operating electric supply unit located at vehicle, designed as generator driven by vehicle engine - Google Patents

Abstract

A vehicle nowadays is fitted with numerous electrically operated devices (5) including an engine stop facility. For an avoidance of a breakdown of the electric system (4) or a reduced performance a device for generating electric energy (2) is activated in the particular case. The device (2) is designed as a claw pole generator with a stator carrying a winding for a three-phase-current and a rotor carrying an exciting winding. A condenser charged by the battery (7) or activated by the generator using an electronic function (8), serves as the supply of the required voltage (1).

Description

The The invention relates to a method for operating an electrical Machine in a motor vehicle, in which for generating a magnetic air gap field between a rotor and a stator of the electric machine an exciter winding arranged on the rotor or on the stator is applied with an excitation voltage, and in which the electrical Machine in a function as a generator for generating electrical Energy for an electrical system and to maintain the state of charge of an electric Energy storage of the electrical system is driven by an internal combustion engine, and / or wherein the electric machine in a function as Starter motor is used to start the internal combustion engine.

The The invention further relates to a device for operating a electric machine in a motor vehicle, in the generation of a magnetic air gap field between a rotor and a Stator of the electric machine one on the rotor or on the stator arranged excitation winding can be acted upon by an excitation voltage, and in which the electric machine in a function as a generator for generating electrical energy for an electrical system and for maintaining the State of charge of an electrical energy storage of the electrical system is drivable by an internal combustion engine, and / or in which the electric machine in a function as a starter motor for starting the Internal combustion engine is used.

electrical Machine transform over the movement of a conductor in a magnetic field mechanical into electrical Energy or vice versa. Such electrical machines are in Motor vehicles as generators for generating electrical energy and increasingly also in vehicles with an engine stop automatic (MSA) as Starter motors used for starting the internal combustion engine. These machines have a fixed component, the stator and a rotating one Component, the rotor, also runners called, up. In today's motor vehicles commonly used permanent magnet synchronous machines, which are usually designed as Klauenpolgeneratoren is on the rotor a field winding (instead of the usual for smaller electrical machines Permanent magnets) and arranged on the stator is a three-phase winding (Armature winding) arranged. The rotor stops by applying a Excitation voltage to the exciter winding the magnetic field ready. Decisive for the power output of the generator, or for the torque development of the starter motor is the magnetic Flux density in the air gap field between rotor and stator, the when driving the rotor over the internal combustion engine, or generated by energizing the rotor winding becomes.

The Today's claw pole generators have an electrophysical inertia, the at a changing Performance requirement causes the a Nacherregung the rotor winding to adjust the air gap field not done fast enough to the requested (increased) performance immediately available to deliver. On the other hand, vehicle electrical systems are relatively high voltage fluctuations subjected and available standing tension for the rotor-magnet excitation is limited by the current vehicle electrical system voltage, which is unfavorable on the effectiveness the re-excitation effects. The power output to the electrical system of the vehicle therefore can not immediately to a sudden increase in power requirements be aligned. In particular, by connecting transient high-current consumers, for example, fan motors, Air conditioning compressors and increasingly also through innovative systems such as Electric valve trains and drive-by-wire systems can reduce voltage drops several volts in the electrical system arise. The electrical system voltage, at the usual today 14V electrical system with a 12V lead-acid battery in normal operation in a range above the battery break-in voltage (about 12.8V) is and can be up to 15V, decreases in such a voltage dip Values below the battery starting voltage (for example, on up to 11 V) until the generator is energized and the required electrical power supplies. The period of such voltage dips is typically in a range of 100ms to several 100ms. analog applies to future 42V vehicle electrical system. unfavorable Operating conditions, in particular an aged, defective or dead battery, with the the voltage dips not immediately or at all not completely can be compensated, can cause that these voltage drops an order of magnitude in which the function of individual consumers, in particular Control devices, can fail. Furthermore you can also loss of comfort occur, for example due to flicker or a uneven fan sound.

From the DE 101 55 670 A1 a method for stabilizing a motor vehicle electrical system is known in which, in the alternative, a currently not required electrical load with sufficiently high electrical power consumption is connected to the electrical system to drive the generator to a higher level of performance. The auxiliary consumer can be switched on permanently or with a weak battery and is then disconnected from the electrical system when another required consumer, for example a safety-relevant consumer such as an electrohydraulic brake, is switched on.

A disadvantage of the known method Affects that the operation of the auxiliary consumer additional fuel consumption. In addition, the regulation of generator operation via auxiliary consumers is relatively expensive in terms of costs and construction.

Farther are control mechanisms for voltage stabilization in on-board electrical systems known with the help of auxiliary storage and electronic circuits compensate for occurring voltage fluctuations.

adversely These systems have a relatively high impact Cost in construction and costs cause, as they costly control equipment and need expensive electronic components. Continue to deliver these Systems an exciter maximum voltage for the electric machine, the determined by the voltage level of the electrical system and in particular is limited and thus relatively inflexible.

One Another problem occurs in the operation of the electric machine Vehicles with automatic engine stop. The engine can directly over the electric machine to be started, which then by an additional Power electronics, for example, operated as a belt-driven starter generator becomes. Before the power electronics that for the generation of the starting torque required rotating field must have the magnetic air gap field by energizing the exciter winding of the generator, for example via carbon brushes, built become. This takes, e.g. in electric machines in claw pole construction, typically a period of about 150ms to complete. Together with the period for the turning of the internal combustion engine until the first ignition (about 200ms) and the time to boot up to idle speed (about 200ms) results in a total start time of about 500-550ms. This period is considered borderline regarding the reasonableness of the user of such System. A development goal in automotive engineering is it Therefore, to achieve start times of MSA systems of well below 500ms. Although it is known by a permanent partial magnetization of Excitation winding (during the total downtime) the magnetization and thus the starting period To shorten, However, this requires a permanent power of several Amperes, which is reflected in a measurable fuel consumption and additionally that electrical electrical system, the battery or other electrical energy storage loaded or their dimensions adversely affected.

task The present invention is therefore the known methods for the operation of an electric machine in motor vehicles so too Improve that the provision of electrical and / or the mechanical performance of the electric machine with a lower Cost expenditure is optimized in time.

The Task is inventively in conjunction solved with the preamble of claim 1, characterized in that the electric machine the motor vehicle, if necessary, by means of a circuit device, a separate voltage source associated with the electrical machine is switched on, over the the excitation winding for a fast excitation of the electric machine with an on-grid independent excitation voltage is charged.

By the connection of the own voltage source if necessary, in particular upon detection of certain operating conditions of the motor vehicle, becomes the electric machine, or the rotor of the electric machine due to the new, by the connection higher, voltage in essential shorter Time, than this with conventional control systems, which would be possible to use as excitation voltage of the vehicle electrical system voltage. The to disposal standing excitation voltage is no longer due to the voltage level limited in the electrical system. This will significantly improve dynamics reached, with which the air gap field can be corrected. Farther If required, it is always a high absolute measure of the maximum excitation of the machine available. This available Becomes measure not as before while driving with a high dynamic power requirement in the Vehicle electrical system by a sinking electrical system voltage and thus a sinking Voltage at the rotor winding decreased. As a result, one of the functionality of a much more complex dynamic on-board network support comparable performance for achieved the operation of the electric machine. Basically the inventive method also as a synergistic supplement suitable for electronic dynamic on-board network support.

According to one preferred embodiment of Invention is the excitation winding acting as a generator electric machine upon detection of a voltage dip in the electrical system due to the connection of a transient load, over the Voltage source in the short term, a higher excitation voltage than the available in the electrical system Excitation voltage for supplied the fast excitation of the generator.

Upon detection of a voltage dip in the electrical system with the aid of appropriate monitoring means due to the connection of one or more transient loads, is via the circuit device, for example via a modified controller power electronics and the slip rings of the claw pole generator, the voltage source switched to the exciter winding of the rotor. In regenerative operation, this results in a spontaneous torque request to the internal combustion engine and the generator power is increased immediately. Since the spontaneous torque request too low idle speed or at low speeds loss of comfort during driving (Fahrzeugruckeln) may occur, the system is in the function to prevent or compensate for critical voltage dips primarily as a measure for emergencies, ie in particular for cases that are appropriate intended to bring down important ECUs to failure. In these cases, then a short-term loss of comfort can be accepted. Basically, however, measures are also conceivable that prevent such short-term loss of comfort when using the system and make the use even with uncritical voltage drops advantageous.

To a further preferred embodiment The invention is the exciter winding acting as a generator electric machine upon detection of a voltage dip in the electrical system due to a failure of the energy storage of the electrical system, over the Voltage source short-term excitation voltage for fast excitation supplied to the generator.

at A failure of the vehicle battery can be due to the fast excitation the generator's functionality important electrical systems of the vehicle. This provides a redundant power source available the security of supply of the on-board network additionally increased or even elaborate 2-Batterie Bordnetzkonzepte or additional Capacitor packages (Ultracaps), without sacrificing security of supply of the electrical system can replace. This aspect is especially true then given if a fuel-efficient and engine-performance-optimizing variable generator control (iGR) in vehicles with brake energy recovery systems is provided as they are increasingly integrated into future vehicles shall be. In this function, the generator is up to a de-energized lower limit, so he does not have any electrical power in can deliver the vehicle electrical system. Instead, the wiring system supplied from the vehicle battery until it reaches a defined discharge state has reached. From a certain depth of discharge can then with Such a system by deliberately controlling the generator excitation very effectively braking energy can be converted back into electrical energy. Is a such function is active, so the generator is not energized or defined under-excited, a redundant energy source is missing in the vehicle electrical system, if not additional Maßnahem, like an extra Emergency battery or Ultracaps are provided in the electrical system. Because falls in In this operating condition, the battery will spontaneously turn off, e.g. through a Line break, so immediately the entire vehicle is de-energized and the Generator can not be re-energized because the battery is not as a charge dispenser for the needed Excitation energy available is. In such a case, the connection is the voltage source of the generator particularly advantageous because the generator then in a short time interval can be excited faster, causing a failure of control units or other safety-related components reliably avoided and possible serious consequential damage be prevented.

According to one another preferred embodiment The invention is the excitation winding acting as a starter motor for an automatic engine stop electric machine at a start of the engine by means of of the starter motor, over the voltage source is an exciter voltage for the fast excitation of the starter motor fed.

For the starfall of the internal combustion engine by means of the starter motor, can be because of the fast excitement the start time around the largest part shorten the magnetization time (about 150ms). This will be the startup performance (Dynamics) significantly improved on vehicles with MSA engine start. On a permanent Vorerregung the excitation winding to the Erstzeitverkürzung can be omitted, resulting in a fuel economy.

To a further preferred embodiment The invention is used to excite the excitation winding of the electrical Machine a higher exciter voltage taken from the voltage source, is available as maximum in the electrical system.

There the electromagnetic time constant of the electric machine through The relationship of inductance and resistance of the excitation winding (L / R) is determined by the application of a higher exciter voltage a higher one Erregrestrom be driven by the excitation winding and thus in shorter Time the magnetization and thus the generation of the magnetic Air gap field can be achieved. This can be the Nacherregung the Generator by a maximum excitation of the air gap field means one clearly over the vehicle electrical system voltage lying correspondingly high excitation voltage, or the start performance increase due to the rapid magnetization of the rotor continue to improve over time. Furthermore, it is possible by a fast excitation in a given time, for example 10ms, which can be derived from the latency, the ECUs at a survive a defined voltage dip without transition to a malfunction, to further improve the security of supply of the electrical system.

The known devices for operating an electrical machine in a motor vehicle have the disadvantage that they are spontaneous Power demand due to certain operating conditions one relatively large Period until the requested service is required.

Further Object of the present invention is therefore the known devices To improve so that they are in all operating conditions of a motor vehicle a temporally improved power output of the electric machine enable.

The Task is inventively in conjunction solved with the preamble of claim 6, characterized in that the electric machine a switchable by means of a circuit device own voltage source is assigned over the excitation winding of the electric machine an on-grid independent excitation voltage can be fed.

By the switchable voltage source can be the electric machine a performance requirement in a much shorter time than the previous one Systems that depend on the voltage level in the electrical system, excited be over there the voltage source is higher Excitation voltage available can be made. this makes possible a fast regeneration of the generator at critical voltage drops as well a quick start when using the machine as a starter generator. The machine's own voltage source is in operative connection with the electric machine is a redundant energy source, the increases the security of supply of the electrical system of the motor vehicle. Of the Expenditure in costs and construction for this redundant energy source is much lower than in the previous electronic Voltage stabilization and voltage protection measures within the wiring system architecture.

preferred embodiments The invention are described in the subclaims.

The Voltage source may be formed as a capacitor. Conceivable but is also a voltage source in the form of an induction coil in combination with a suitable electrical storage element. Both possibilities make a cost-effective Rechargeable power source with one depending on the type of electrical Machine easily customizable voltage level available The voltage source may preferably be integrated into the generator, whereby installation space is saved, but it can also be arranged externally, which in particular in a starter generator system with external power electronics is advantageous.

The Power source has ideally at least over an energy content and such a low internal resistance, which machine-specific is required in order to for example, 10 ms, the air gap field of the electric machine maximum excite. In this case, the voltage level of the voltage source above the maximum vehicle electrical system voltage to one as possible short fast excitation, or to realize Nacherregung. Thereby can be an increased, or spontaneous power output of the electric machine to a spontaneous current request (generator operation), or starting torque request (Start operation). In particular, the failure of security relevant Consumers reliable avoided and the starting performance of vehicles with automatic engine stop improved.

By the recharging of the voltage source by means of a suitable voltage converter arrangement, For example, DC / DC converter, transformer, power electronics, through the electric machine itself or from the electrical energy storage (vehicle battery) the on-board network ensures that even with frequent connection the fast pace availability the voltage source is not limited.

Further Details of the invention will become apparent from the following detailed Description and attached Drawing in which a preferred embodiment of the invention, for example is illustrated.

It shows

1 : A block diagram of a vehicle electrical system of a motor vehicle.

An apparatus for operating an electrical machine in a motor vehicle essentially consists of a voltage source 1 that an electric machine 2 via a circuit device 3 is switchable.

The electric machine 2 is in per se known construction as a Klauenpolgenerator with a fixed stator which carries a three-phase winding and with a rotating rotor, which carries a field winding formed. The claw pole generator 2 is for electrical power generation for the power supply for a vehicle electrical system 4 with the consumers 5 as well as to maintain or recharge an energy store 7 of the electrical system 4 , via an internal combustion engine 6 drivable. Furthermore, the generator 2 as a starter motor for starting the internal combustion engine 6 by means of power electronics 8th be operated reversibly. The electric machine 2 with the power electronics 8th forms a starter generator system.

The voltage source 1 is advantageously designed as a capacitor. The capacitor 1 is via the circuit device 3 , which is advantageously designed as a regulator power electronics, with the exciter winding, not shown, of the rotor of the generator 1 electrically connectable. The capacitor 1 can from the energy store 7 ie via the vehicle battery, via the vehicle electrical system 4 or during generator operation via the generator 2 to be reloaded if necessary. About monitoring means, not shown, with the help of which the voltage level in the electrical system 4 is monitorable, is the circuit device 3 controllable. Furthermore, the circuit device 3 via the power electronics 8th can be controlled for starter operation.

A method for operating an electrical machine in a motor vehicle is based essentially on the on-demand connection of one of the electric machines 2 associated voltage source 1 on a field winding of the electric machine 2 ,

The inventive method is preferably carried out with the device described above. In a first embodiment, the method serves as an emergency measure in which an immediate power output of the generator 2 due to a critical voltage dip in the electrical system 4 is mandatory. Occurs such a (via the vehicle electrical system monitoring detected) case, for example by simultaneous connection of several high-current consumers 5 in the electrical system 4 , is via the circuit device 3 the voltage source 1 on the excitation winding of the rotor of the generator 1 switched. The excitation voltage is advantageously well above the maximum excitation voltage of the electrical system 4 , This has an immediate Nacherregung the exciter winding and thus an immediate reinforcement of the magnetic air gap field between the rotor and stator result. In operative connection with the torque request thereby caused to the internal combustion engine 6 becomes a spontaneous higher power output of the generator 1 generated. This happens in a period of a few milliseconds, whereby a collapse of the electrical system supply, possibly with a failure of control devices or safety-related consumers, is prevented. Has the voltage in the electrical system 4 normalized again, the now discharged voltage source 1 (Condenser) recharged and is available again within a short time.

In a second embodiment of the method, the voltage source 1 used in a vehicle without emergency battery or other auxiliary storage but with braking energy recovery and variable generator excitation. If the vehicle battery fails 7 in a partially or completely de-energized generator 2 Off, an immediate excitation on the connection of the voltage source is immediately 1 of the generator 2 initiated a total failure of the electrical system 4 prevents and at least the function of safety-relevant consumers as a redundant energy source 5 of the vehicle.

In a third embodiment of the method, the electric machine 2 used as a starter motor in a vehicle with an automatic engine stop (MSA). If the vehicle is at a standstill and the combustion engine is to be started when the MSA is activated, the generator will be activated 2 via the power electronics 8th switched to starter mode. At the same time via the circuit device 3 the voltage source 1 switched on and the exciter winding with a voltage which is adapted to the maximum possible excitation of the air gap field of the generator type used, applied. Due to a low internal resistance of the voltage source 1 in operative connection with the adjusted for the maximum excitation high electrical energy content of the voltage source 1 , there is a sudden fast excitation of the starter motor 1 and the associated generation of the spin field necessary for the starmoment. As a result, a significantly improved starting dynamics is achieved.

1

voltage source

2

electrical machine

3

circuit means

4

board network

5

electrical consumer

6

internal combustion engine

7

energy storage

8th

power electronics

Claims (14)

A method for operating an electrical machine in a motor vehicle, wherein for generating a magnetic air gap field between a rotor and a stator of the electric machine, an exciter winding arranged on the rotor or on the stator is subjected to an exciter voltage, and in which the electric machine in a Function as a generator for generating electrical energy for a vehicle electrical system and for maintaining the state of charge of an electrical energy storage of the on-board network is driven by an internal combustion engine, and / or in which the electric machine is used in a function as a starter motor for starting the internal combustion engine, characterized in that the electrical machine ( 2 ) of the motor vehicle as needed, by means of a circuit device ( 3 ) one of the electrical machine ( 2 ) associated own voltage source ( 1 ) is switched, via which the field winding for a fast excitation of the electric machine ( 2 ) is charged with a grid voltage independent exciter voltage. A method according to claim 1, characterized in that the excitation winding of the electric machine acting as a generator ( 2 ) upon detection of a voltage dip in the electrical system ( 4 ) due to the connection of a transient load ( 5 ), via the voltage source ( 1 ) in the short term, a higher excitation voltage than that in the electrical system ( 4 ) available excitation voltage for the fast excitation of the generator ( 2 ) is supplied. A method according to claim 1 or 2, characterized in that the excitation winding of the electric machine acting as a generator ( 2 ) upon detection of a voltage dip in the electrical system ( 4 ) due to a failure of the energy store ( 7 ) of the vehicle electrical system ( 4 ), via the voltage source ( 1 ) shortly excitation voltage for the fast excitation of the generator ( 2 ) is supplied. A method according to claim 1, characterized in that the field winding of the starter motor for an engine stop automatic acting electrical machine ( 2 ) at a start of the internal combustion engine ( 6 ) by means of the starter motor ( 2 ), via the voltage source ( 1 ) An excitation voltage for the fast excitation of the starter motor is supplied. Method according to one of claims 1 to 4, characterized in that for exciting the excitation winding of the electric machine ( 2 ) a higher excitation voltage from the voltage source ( 1 ) is taken as the in the electrical system ( 4 ) maximum available excitation voltage. Device for operating an electrical machine in a motor vehicle, wherein for generating a magnetic air gap field between a rotor and a stator of the electric machine arranged on the rotor or on the stator field winding with an excitation voltage can be acted upon, and wherein the electric machine in a Function as a generator for generating electrical energy for a vehicle electrical system and for maintaining the state of charge of an electrical energy storage of the electrical system of an internal combustion engine is driven, and / or in which the electric machine can be used in a function as a starter motor for starting the engine, characterized in that the electrical machine ( 2 ) one by means of a circuit device ( 3 ) switchable own voltage source ( 1 ) is assigned, via which the excitation winding of the electric machine ( 2 ) An on-grid independent excitation voltage can be fed. Device according to claim 6, characterized in that the voltage source ( 1 ) is formed as a capacitor. Device according to claim 6, characterized in that the voltage source ( 1 ) is formed as an induction coil in combination with an electric storage element. Device according to one of claims 6 to 8, characterized in that the voltage source ( 1 ) in the electric machine ( 2 ) is geometrically integrated. Device according to one of claims 6 to 8, characterized in that the voltage source ( 1 ) as an outside of the electrical machine ( 2 ) arranged separate component is formed. Device according to one of claims 6 to 10, characterized in that the voltage source ( 1 ) has a maximum voltage, which is above that from the electrical system ( 4 ) Removable maximum excitation voltage is. Device according to one of claims 6 to 11, characterized in that the voltage source ( 1 ) a the performance data of the electric machine ( 2 ) has adapted maximum energy content, by means of which the magnetic air gap field of the electric machine ( 2 ) is excitable maximum. Device according to one of claims 6 to 12, characterized in that the voltage source ( 1 ) has a low-resistance internal resistance. Device according to one of claims 6 to 13, characterized in that the voltage source ( 1 ) via a voltage transformer arrangement by means of the electric machine ( 2 ) and / or from the electrical energy store ( 7 ) of the vehicle electrical system ( 4 ) is reloadable.