WO2011064013A2

WO2011064013A2 - Circuit assembly for a control device

Info

Publication number: WO2011064013A2
Application number: PCT/EP2010/064227
Authority: WO
Inventors: Matthias Schmidt
Original assignee: Robert Bosch Gmbh
Priority date: 2009-11-26
Filing date: 2010-09-27
Publication date: 2011-06-03
Also published as: WO2011064013A3; DE102009047163A1

Abstract

The invention relates to a circuit assembly (1) for an electric machine (2), in particular a starter motor for starting an internal combustion engine (15), in a motor vehicle, comprising a current limiter (3) for limiting an activation current of the electric machine (2). In order to operate the electric machine (2) in the most simple and resource-conserving manner, the circuit assembly (1) comprises a bridging device (4) having a controllable switching device (5) for bridging the current limiter (3).

Description

description

title

Circuit arrangement for a starting device prior art

The invention relates to a circuit arrangement for an electric machine, in particular a starter motor for starting an internal combustion engine, in a motor vehicle, with a current limiting device for limiting an inrush current of the electric machine. The invention also relates to a method for operating such a circuit arrangement.

Furthermore, the invention relates to a starting device for starting an internal combustion engine in a motor vehicle, with a, in particular the aforementioned, circuit arrangement and with a starter motor.

To start internal combustion engines in motor vehicles starting devices are used, which are constructed with a starter motor on the principle of a DC machine with mechanical commutation, especially as Außenpol- machine.

In order to achieve a required high torque and high performance of the starter with a comparatively low vehicle electrical system voltage of about 12 V to 14 V, or 24 V to 28 V, the DC machine is equipped with a low number of turns and a large cable cross-section. Due to the resulting low impedance, that is about as a rotor or a stator, depending on the embodiment, the power loss is reduced and achieved a high torque output with relatively good efficiency. On the other hand, just the low impedance, and especially the low ohmic resistance, but also the low inductance, leads to high inrush currents and a temporary voltage dip in a battery-powered vehicle electrical system. Only with the start of the starter motor is with decreasing speed induces a reverse voltage, which limits the current and thus counteracts the voltage drop. Additional consumers that are connected to the vehicle electrical system must be designed for this voltage dip or are deactivated at the time of the voltage dip.

In conventional starting systems, the voltage drop at the start is usually not critical, since additional consumers are mostly not yet active or inactive, or the temporary shutdown of a consumer is accepted. In starter-based start-stop systems in which the internal combustion engine is started by the starter motor even with additional active consumers, for example, after a short holding phase of the motor vehicle, increasingly higher demands are placed on a voltage maintenance in the electrical system. In order to provide a stable vehicle electrical system voltage, a second battery or a DC / DC converter is provided.

DE 103 17 466 A1 describes a circuit arrangement with a starter motor of an internal combustion engine of a motor vehicle and with a series resistor connected in series to the starter resistor, namely an NTC series resistor whose resistance decreases with increasing temperature. When starting the starter motor, the NTC series resistor heats up and its resistance value decreases.

DE 102 31 088 A1 describes a circuit arrangement of a starting device for an internal combustion engine of a motor vehicle with two series-connected transistors, wherein two resistors are connected as a voltage division in each case parallel to a transistor to diagnose a short-circuit defect of the transistors in an off state of the transistors ,

It is an object of the invention to provide a circuit arrangement, a method for operating the same and a starting device of the type described above in such a way that an electric machine is as simple as possible, resource-saving operation with the highest possible electrical system stability.

Disclosure of the invention According to the invention the object is achieved by the subject matter of claims 1, 6 and 10. The dependent claims define preferred embodiments of the invention. It is an idea of the invention that the circuit arrangement for an electrical machine comprises a bridging device with a controllable switching device for bypassing a current limiting device and which limits an inrush current of the electric machine when starting by means of the current limiting device and then the current limiting device is bridged with the bridging device. So can with the

Circuit arrangement limit the inrush current of the electric machine and, in particular after a start, operate the electric machine with a full power by the current limiting device is bridged, so that a maximum current is achieved. The electric machine can be easily operated with a current limiting device by the current limiting device can be deactivated by mere bridging. Furthermore, a resource-saving operation of the electric machine is possible because the electrical machine is spared by reducing the voltage drop when starting the electric machine and a more dimensioned electrical supply, or protective measures further electrical

Consumers are avoided.

The controllable switching device can also be designed as an electromechanical switching relay or as an electronic switch, for example with a transistor. Thus, the bridging of the current limiting device and thus also the voltage drop can be controlled defined by switching the switching device. In addition, such a switching device is easy to control and cost feasible. It is preferred that the electric machine is arranged in a motor vehicle and in particular is operated via a battery-powered vehicle electrical system. With the current limiting device, the electrical load of the electrical system can limit and still operate the electric machine by means of the lock-up device with a maximum power, so that the battery of the electrical system for a lower power, so resource-saving, dimensioned. Preferably, the circuit arrangement for a starter motor for starting an internal combustion engine is formed in a motor vehicle, so that the electric machine is therefore a starter motor. To start an internal combustion engine, a high power is required, which is achieved in particular by a high current to the starter motor, resulting in a voltage drop of the electrical system results, which can be reduced by means of the current limiting device. Furthermore, the current limiting device can be bridged with the bridging device in order to be able to use a maximum starting torque during a cold start and / or the starting power after a breakaway of the motor.

It is further preferred that the circuit arrangement is designed for a starter motor of a start-stop system, in which, for example, during short holding phases of the motor vehicle, the internal combustion engine is turned off and is turned on again for a drive, in particular fuel consumption and / or C0 _second To reduce emissions.

In a start-stop system, with a short stop, so in particular when the engine is switched off, a vehicle electrical system consumers, such as a radio or control units of the motor vehicle, in operation and from the voltage dip, especially at a warm start, be affected. Due to the voltage dip, a short-term failure of the electrical system consumer can occur because it requires a certain minimum voltage in order to function safely. Such a failure is, for example in the case of a radio, at least undesirable or even constitutes a safety risk, in particular in the case of a control device which prevents, for example, an unintentional rolling away of the motor vehicle, namely a so-called ESP control device with hill hold function.

Conventionally, a second battery and / or a DC / DC converter installed in the electrical system to provide, at least selected electrical system consumers a stabilized voltage available. By the current limiting device, the inrush current of the starter motor can be limited during startup and the resulting voltage dip, at least to an uncritical degree, can be reduced. The second battery or the DC / DC converter can be be pulled, so that the electrical system of the motor vehicle is resource-saving feasible. It is ensured by bridging the current limiting device that the engine can still be safely started with a full electrical power of the starter motor.

In a preferred embodiment, the current-limiting device comprises a start-up resistor limiting the inrush current of the electrical machine, in particular an ohmic resistor. The starting resistor can be connected in series with the electric machine and allows for low circuit complexity a resource-saving and cost-effective limitation of the current supply of the electric machine.

The starting resistance can be designed as a line resistance, in particular as an electrical supply line of the electrical machine, wherein it can be defined by a suitable choice of the line material, the line length and / or the line cross-section. This reduces the cost and assembly costs.

Preferably, the starting resistor is a discrete resistance element, in particular a metallic conductor. Such resistance elements are in numerous

Versions, in particular with respect to their resistance value and current carrying capacity, available and allow a cost-effective and resource-saving implementation of the circuit arrangement. In this case, a thermal design of the resistive element is particularly important, since in particular a starter motor is subjected to high current and also in a

Motor vehicle, the resistance element is exposed to large temperature fluctuations.

The starting resistor may be arranged in an engine compartment of the motor vehicle, so that it is easily accessible and a simple assembly is possible.

Preferably, the starting resistor is formed on the starter motor. The starting resistor and the starter motor can thus be produced in a cost-effective and resource-saving manner as a prefabricated, in particular coordinated, module and can be easily installed in a plurality of different motor vehicle platforms. In this sense, the taxable

Switching device and / or other components of the lock-up device be arranged in the engine compartment and also on the starting device, in particular on the starter motor.

The starting of the electric machine takes a start-up period, which is determined in particular by a mechanical realization of the electric machine, the electric power and / or by a driven by the electric machine device, in particular the internal combustion engine of the motor vehicle. During the start-up period, the inrush current through the electrical machine, which is the cause of the voltage dip, flows to the current supply. In a preferred embodiment, the current-limiting device can be bridged with the bridging device in a time-controlled manner, in particular after a current limiting period. A time control is simple and inexpensive, for example, as a switching delay or as a correspondingly slow switching time, in particular a relay feasible.

Preferably, with the current limiting device, the inrush current is essentially limited during the startup period, wherein, in particular, the startup duration essentially corresponds to the current limiting duration. Thus, the voltage drop can be reliably reduced and the electric machine can be operated immediately after starting with a maximum electric power limited by the start-up current during startup and the lockup device, in particular synchronously to the end of the startup period, timed activated, so the current limiting device is bypassed , As previously explained, the voltage drop at the start of the electrical

Machine particularly high and decreases with increasing speed of the electric machine. Preferably, the current limiting device with the lock-up device is speed-controlled, in particular as a function of the rotational speed of the electric machine bridged, and preferably so that when starting the electric machine, ie at low speeds, the energization of the electric machine with the current limiting device is limited and from a certain speed, the current limiting device with the lock-up device, in particular for a maximum current, is bridged. Thus, a simple and inexpensive start-up current limit can be realized. In this case, the current limiting device can be used particularly effectively, and in particular only until the electrical see machine has reached a certain speed, from the voltage drop has fallen below a critical value. Incidentally, the current limiting device can also be bridged as a function of a rotational speed of the internal combustion engine, since it is coupled to the electric machine as a starter motor at least for starting.

According to a preferred embodiment, the bridging device, in particular the controllable switching device, is controlled by a control device, in particular time-controlled and / or speed-controlled. In this case, a control unit with a timer or a timer, that is, a timer as a time-control device for the current limit duration be designed to operate the lock-up device time-controlled, so to bridge the current limiting device time-controlled. In addition, but preferably alternatively, the control unit can detect the rotational speed of the electric machine, for example by means of a sensor or as information from another control device, in order to operate the lockup device in a speed-controlled manner, ie to bypass the current limiting device in a speed-controlled manner. The control unit may be integrated in the circuit arrangement, in particular in the lockup device, or, alternatively, as a, in any case already existing, start-stop control unit, engine control unit, on-board control unit or control unit of the electrical machine, in particular as a starter control unit, may be formed, optionally under Use of an additional relay to control the lock-up device.

Furthermore, the controller may be formed with a microcomputer and a computer program product, for example, to flexibly adapt the current limiting period during which the current limiting device is bridged to different starting times or to bridge the current limiting device according to different speed specifications.

In a further preferred embodiment, the bridging device is positively controlled, so no additional control or regulation, in particular as an additional electronic module or as

Control unit, is necessary. This makes a simple and cost-effective start-up Current limit can be realized. The bridging device can also be positively controlled by the speed of the electric machine, as explained later. In a further preferred embodiment, the bridging device is controlled by a voltage that drops in particular across the electric machine, in particular by the controllable switching device is switched by the voltage. A voltage as an electrical variable can be used with little component complexity simply and directly for switching the bridging device. In this case, the voltage can be detected and evaluated with additional electronics or a control unit that is present in any case, in order to control the bridging device in a voltage-dependent manner, ie to bridge the current-limiting device in a voltage-dependent manner. Alternatively, the bridging device can be forcibly controlled by the voltage, for example by the controllable switching device being switched by the voltage, preferably directly, ie not by means of the control device.

Incidentally, the voltage drop across the electric machine as the operating variable may also be due to a voltage induced in the electric machine which increases with increasing speed. Since the voltage drop across the electrical machine thus depends on its rotational speed, the current limiting device can thus be bypassed simultaneously with limited component and speed control.

It is preferred that a switch-on voltage, the overwriting of which switches the bridging device from a switched-off to a switched-on state, amounts to at least 30% and / or at most 70% of a rated voltage of the electrical machine. This ensures that the bridging device switches in a medium voltage range and in particular prevents contact flutter, ie unintentional switching in the case of low voltage fluctuations, with a nominal voltage switched on or off. Furthermore, it is ensured that the lock-up device remains switched off when the electric machine is turned on, namely only after a certain rotational speed of the electric machine has a certain tension is induced, which corresponds to the turn-on voltage of the lock-up device, in which the current limiting device is bridged.

Further, it is preferred that a turn-off, below which the lock-up device from a switched to a switched off

Condition changes, at most 50% of a nominal voltage of the electrical machine is. This prevents that after switching on the lock-up device it is switched off unintentionally, since just from the bridging of the current limiting device results in an increased current flow and thus a voltage dip, wherein the voltage under the

Switch-on voltage may drop. Preferably, the turn-off voltage is thus significantly lower, for example, at least 30% of the rated voltage of the electric machine, as the turn-on, to ensure safe switching on and off of the lock-up device. Thus, quasi, a hysteresis in the voltage-controlled positive control of the

Bridging device to realize a reliable switching of the lock-up device.

The turn-on and / or the turn-off can be defined by a mechanical or electronic nature of the lock-up device, especially in a switching relay as a controllable switching device by a suitable design of an iron circuit, a relay winding, an armature, a return spring or switching contacts. Preferably, a working current of the switching relay is a maximum of 5 A, so that the electrical system of the motor vehicle is only slightly loaded by the switching relay and a voltage drop is reduced due to the switching of the switching relay. As a preferred embodiment of the invention, as mentioned above, the

Bridging device switched by a voltage drop across the electrical machine. In this case, the bridging device, in particular the controllable switching device can be set to an electrical potential on the electric machine, for example by being connected via an e- lectric line with a terminal of the starter motor, so that the energization of the switching device directly through the over the Starter motor declining voltage is controlled. Such a circuit arrangement allows a simple, in particular without further electronic or electromechanical components realizable, switchable lock-up device. The bridging device may have a series resistor connected in series with the controllable switching device, in particular with a relay coil of the switching relay, so that a switching point of the switching device can be adjusted via the setting resistor. If the bridging device is switched by a voltage, in particular by the voltage drop across the electric machine, the switching point of the bridging device can be tuned or defined by means of the adjusting resistor, in particular with respect to the rotational speed of the electric machine. In this case, the adjustment resistor with the controllable switching device, in particular with an internal resistance of the relay coil, acts as a voltage divider. The Einstellwi- resistance may have a fixed or variable resistance.

In a preferred embodiment, the bridging device is designed as a contact closer, namely for bridging the current limiting device in a switched, in particular energized, state of the bridging device. Then, the lock-up device must be turned on only after the inrush current of the electric machine has been limited, so that an additional voltage dip in the operation of the current limiting device is avoided by the energization of the lock-up device. Another advantage of the lock-up device as a contact closure is that during the start-up period only the contact must remain open, so that the voltage limiting the current limiting device is not accidentally bypassed, for example by a switching relay as a controllable switching device unintentionally drops due to the voltage drop.

In this case, the bridging device, in particular the controllable switching device, preferably has a switching delay for closing, which essentially corresponds to the starting time. Thus, the bridging device and the electric machine can be controlled at the same time, in particular powered, in which case the energization of the electric machine with the current limiting device is limited during the startup period and after Expires the switching delay, the current limiting device is bridged by the then switching bridging device. As a result, the circuit arrangement can be realized in a resource-conserving manner, namely, in particular without a time-switching control unit.

As an alternative preferred embodiment, the lockup device is configured as a contact opener. Then, a contact of the lock-up device is preferably opened before the electric machine is energized to start. This can for example be realized by the contact of the lock-up device is opened in good time before the energizing of the electric machine or by the contact of the lock-up device is faster, so with a shorter switching time, designed as a switching device for energizing the electric machine, so that the lock-up device can be controlled simultaneously with the electrical machine with low component costs.

Furthermore, the circuit arrangement can be realized in this embodiment so that the lock-up device must be energized only during start-up of the electric machine. Then a greater electrical power is available for operation of the electric machine after startup. in the

Incidentally, in each case one of the two aforementioned alternative embodiments for a, in particular speed-dependent, controlled by a voltage bridging device can be suitably selected. According to a preferred embodiment, at a temperature below a temperature limit value, the current limiting device is bridged with the bridging device, in particular when starting the electric machine, because the power required to start the internal combustion engine increases with decreasing temperature. If the current-limiting device is already bridged when the electric machine starts up, that is to say if the electric machine is more strongly energized, a greater power or a higher torque is available when starting up. In addition, as the temperature decreases, the performance of the supply battery decreases. Thus, in particular at cold temperatures, that is to say at least below the selected temperature limit value, the starter motor can be activated from the start with a full main current for breaking the internal combustion engine out of a standstill. Operate position. Thus, in a cold start with maximum power, namely without current limit, but at an increased voltage dip, the electric machine, so in particular the internal combustion engine, and turn on a warm start, in which in particular in a start-stop system more electrical system consumers are turned on , realize a current limit to reduce a voltage dip.

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.

Brief description of the drawings

The invention will be explained in more detail below with reference to the drawings. Show it:

1 shows a starting device with a circuit arrangement, FIG. 2 shows another starting device with a circuit arrangement, FIG. 3 shows a further circuit arrangement, FIG. 4 shows a further circuit arrangement and FIG

5 shows a flow chart for a method for operating the starting device or the circuit arrangement.

1 shows a starting device 17 for starting an internal combustion engine 15 in a motor vehicle, not shown, with a circuit arrangement 1 and a starter motor 2 as an electric machine 2. The starting device 17 further comprises a conventional starter relay 7, in particular for switching on and off of a current supply the starter motor 2 with a starter relay contact 1 1 is formed. With the starter relay, a starter motor driven by the starter motor 2, a ring gear of an internal combustion engine is fed to start them. The circuit arrangement 1 is formed with a current limiting device 3, namely a current limiting starting resistor, for limiting an inrush current of the starter motor 2. Furthermore, the circuit arrangement 1 comprises a bridging device 4 for bridging the current-limiting device 3 with a switching relay 5 as a controllable switching device.

In this case, the circuit arrangement 1 is controlled by an already present in the motor vehicle control unit 16 for a start-stop control, which also controls the energization of the starter motor 2 via the starter relay 7. The control unit 16 has its own connection interface for the circuit arrangement 1. As alternative embodiments, the circuit arrangement 1 can also be controlled by an ignition switch or a start button in an instrument panel of the motor vehicle.

The starting resistor 3 limits an inrush current of the starter motor 2 by the starting resistor 3 is quasi connected as a series resistor in series with the starter motor 2, in particular, only the inrush current is limited, as will be explained later. The starting resistor 3 is formed as a commercially available discrete resistance element based on a metallic conductor.

The switching relay 5 of the lock-up device 4 is designed as a contact closer, namely for bridging the starting resistor 3 in an on, energized state of the switching relay 5, in which a switching relay contact 12 is closed.

In this embodiment, the starter relay 7 is formed in a conventional construction with a retraction 14 and a holding winding 13 and arranged together with the starter motor 2 in an engine compartment of the motor vehicle, wherein the starting device 17 is formed, for example, as a thrust drive starter.

At the beginning of a starting operation of the internal combustion engine 15, the lock-up device 4 is deactivated by the control unit 16, so that the switching relay 5 is not energized and the switching relay contact 12 is opened. The starter relay 7 is controlled by the control unit 16 in order to close the starter relay contact 1 1 and to energize the starter motor 2 from a battery 10, that is to say a switch. As a result, the inrush current is limited by the starting resistor 3 and a voltage drop in a vehicle electrical system 18 is reduced. Incidentally, by tightening the starter relay 7, not shown, the starter motor 2 is meshed with a starter pinion in a ring gear of the internal combustion engine 15 for a mechanical coupling.

With the beginning of energization, namely the beginning of a startup period of the starter motor 2, the speed increases increasingly, while the inrush current increasingly decreases, to a point in time from which even without a current limiting the voltage dip would not exceed an undesirable level and the End of the start-up period determined. Therefore, after a certain current limiting period since switching on the starter motor 2, namely essentially after the startup period, the lockup device 4 is activated in a timed manner by the control unit 16 by means of a timer control of the control unit 16, namely the switching relay contact 12 is closed. Thus, the current limiting device 3 is bypassed to energize the starter motor 2 with a maximum power through the battery 10.

As an alternative, not shown, embodiments, the controller 16 may also determine a speed of the starter motor 2, for example, with a speed sensor or by evaluating a voltage at a terminal KL45 of the starter motor 2. Then the bridging device 4 can be controlled, ie the switching relay 5 are energized to close the switching relay contact 12, as soon as a certain speed is reached.

Another, not shown, embodiment differs from that shown in FIG. 1 in that the switching relay 5 is not actuated as a contact closer via the control unit 16 but directly by a voltage at the terminal KL50 or alternatively at the terminal KL45. Furthermore, the switching relay 5 with a sufficiently long switching delay, the

Substantially corresponds to the startup duration, designed so that after the start of the energization of the starter motor 2, the switching relay contact 12 for bridging the current limiting device 3 is quasi time-controlled closed only after the switching delay. Thus, the inrush current can be limited and the current limiting device forcibly controlled and timed for a over a certain period of time, namely the switching delay, for a maximum excitation of the starter motor 2.

Alternatively, in another embodiment, not shown, the switching relay 5 may be connected as a contact opener between the terminal 50 and the terminal KL45. In this case, the switching relay 5, as explained later, is formed so that it has a short switching time for opening the switching relay contact 12, which is in particular shorter than a switching time of the starter relay 7. In addition, it is designed to close slowly enough with the switching delay in order to bridge the current limiting device 3 in a time-controlled manner, namely substantially after the start-up period.

2 shows a starting device 17 for starting an internal combustion engine 15 in a motor vehicle, not shown, with a circuit arrangement 1 and a starter motor 2. The circuit arrangement 1 is for an electric machine 2, namely the starter motor 2 for starting the internal combustion engine 15 in the motor vehicle, with a current limiting device 3, namely a starting resistor, designed to limit an inrush current of the starter motor 2. The circuit arrangement 1 comprises a bridging device 4, namely a switching relay 5 and a setting resistor 6, for bypassing a current limiting device 3, specifically the current limiting starting resistor. In this embodiment, the circuit arrangement 1 comprises the conventional starter relay 7, which is designed in particular for switching on and off an energization of the starter motor 2 with a starter relay contact 1 1. In this case, the circuit arrangement 1 is controlled by a control unit 16 for a start-stop control, which ultimately controls the energization of the starter motor 2 via a switching device 8. As alternative embodiments, the switching device 8 may also be controlled via an ignition switch or a start button in an instrument panel of the motor vehicle.

The starting resistor 3 and the switching relay 5 are, as described in FIG. 1, designed as a discrete resistance element or as a contact closer. Also analogous to FIG. 1, the starter relay 7 is formed with a pull-in winding and a holding winding 13. In contrast to FIG. 1, the bridging device 4, in particular the switching relay 5, is not controlled directly by the control unit 16, but is, as explained later, realized by a voltage forcibly controlled.

To start the internal combustion engine 15, the switching device 8 is actuated by the control unit 16, so that a current path with the pull-in winding 14, the starting resistor 3 and the starter motor 2 and a current path with the holding winding 13 are energized by the battery 10. Consequently, the starter relay 7 attracts and the starter relay contact 1 1 is closed. By tightening the starter relay 7 also, not shown, the starter motor 2 is meshed with a starter pinion in a ring gear of the internal combustion engine 15 for a mechanical coupling. Once the starter relay contact 1 1 is closed, the pull-in winding 14 is bridged and the power consumption of the starter relay 7 is reduced, namely to the energization of the holding winding 13. In addition, the starter motor 2 is energized via the starter relay contact 1 1 and the starting resistor 3 and thus turns on , wherein the inrush current is limited by means of the starting resistor 3 and so also a voltage dip is reduced.

The switched in series with the adjusting resistor 6 switching relay 5 is connected in parallel with the starter motor 2, so that about the switching relay 5 with the adjusting resistor 6 about the same voltage as applied to the starter motor 2. When starting the starter motor 2 only a small voltage drops over this and the switching relay 5 is open, so that the energization of the starter motor 2 is limited by the starting resistor 3. With increasing speed of the starter motor 2, a voltage is increasingly induced in this, which increases so much that a switch-on voltage of the switching relay 5 is achieved. Consequently, the switching relay 5 is increasingly energized and switches to an on state, so that the starting resistor 3 is bridged by means of the switching relay contact 12, the full available voltage is switched when energizing the battery 10 to the starter motor 2 and thus a maximum current is available for full starter performance.

The switching relay 5 is thus forcibly controlled by the voltage drop across the starter motor 2, in such a way that starting from a certain speed of the starter motor 2, the starting resistor 3 is bridged. A suitable speed, in which the lock-up device 4, in particular the switching relay 5, is switched, can be adjusted via the adjustment resistor 6, since it forms a voltage divider of the voltage drop across the starter motor 2 with an internal resistance of the relay coil of the switching relay 5, so that the ratio of the turn-on of the switching relay 5 to that induced in the starter motor 2

Set voltage.

Thus, in this embodiment, the lock-up device 4 is speed-controlled, in dependence on the speed of the starter motor 2. In this case, the switching relay 5 has a relation to the turn-on voltage significantly lower turn-off, so it is not in a further voltage dip immediately after bridging the starting resistance 3 again releases, so the lock-up device 4 is turned off accidentally.

Upon termination of the starting process, ie an opening of the switching device 8, the energization of the starter relay 7, in particular the holding winding 13, is interrupted and the starter relay contact 1 1 is opened. Thereafter, the switching relay 5 drops with a certain delay, since for the time being one of the outgoing, quasi-dynamically operated starter motor 2 induced voltage is applied. Then the arrangement is ready for the next start.

In this embodiment, a starter motor 2 with an electric power between 1 kW and 2.5 kW is preferred, in which case a starting resistor 3 between 2 mOhm and 20 mOhm is selected. In addition, the turn-on voltage of the switching relay 5 is about 60% and the turn-off voltage about 30% of the rated voltage of the starter motor. 2

FIG. 3 shows a circuit diagram of a further, alternative circuit arrangement 1 of the starter device 17 according to FIG. 2, which, apart from a simpler starter relay 7 with only one winding, comprises the same components as the exemplary embodiment previously shown. Such a simplified starter relay 7 can be produced in a resource-saving and cost-effective manner. Furthermore, apart from the pull-in winding 14, the explanation of FIG. 2 also applies without restriction to this exemplary embodiment. 4 shows a circuit diagram of a further circuit arrangement 1 of the starting device 17 according to FIG. 2 for the starter motor 2 for starting the internal combustion engine 15. In this embodiment, the switching relay 5 is designed as a contact opener, ie the switching relay contact 12 is in the de-energized state the switching relay 5 is closed. Below are only the essential

Differences from the embodiment shown in FIG. 3 explained: When closing the switching device 8, the switching relay 5 is first energized through the adjustment resistor 6 and a diode 9 through the still stationary at this time, or then starting starter motor 2 through, so that the switching relay contact 12 opens and a bridging of the starting resistor 3 is canceled. In this case, a switching time of the switching relay 5 is formed significantly below a switching time of the starter relay 7, so that the likewise when closing the switching device 8 energized starter relay 7 only after opening the switching relay contact 12, the starter relay contact 1 1 closes and the starter motor 2 on the starting resistor 3 of the Battery 10 is energized.

As explained above, an increasing voltage is induced with increasing speed of the starter motor 2, so that in this circuit 1, the voltage at the switching relay 5 is increasingly reduced, in such a way that the turn-off voltage of the switching relay 5 is exceeded. Consequently, the

Switching relay contact 12 is opened, the bridging of the starting resistor 3 is canceled and the starter motor 2 is energized at the full available voltage so that the full starter power is available. Thus, a power consumption of the switching relay 5 is reduced after the starter motor 2 is turned on.

Upon termination of the starting operation by opening the switching device 8, the diode 9 prevents the switching relay 5 is energized via the still closed starter relay contact 1 1 quasi backward and closes again. In addition, the diode prevents 9 in this case that the starter relay 7 is energized via the relay winding of the switching relay 5 and thus goes into latching.

Other, not shown embodiments differ from those previously illustrated in that the circuit arrangement 1 has a temperature-dependent switch, which interrupts the bridging of the starting resistor 3 at a temperature below a certain limit, so that at

Temperatures below this limit already at start-up, so from the beginning on, the full voltage for a maximum current, so also a maximum power of the starter motor 2 is available.

FIG. 5 shows a flowchart with steps of a method for operating the circuit arrangement 1 or else the starting device 17 according to FIGS. 1 to 4.

In a step 40, it is checked whether a temperature of the starting device 17 falls below a certain limit value. If this is the case, the bridging device 4 is switched on in a step 42, otherwise the bridging device 4 remains switched off in a step 41.

Subsequently, in a step 43, the starter motor 2 is energized by closing the switching device 8 to turn it, wherein in dependence of the preceding steps at a temperature of at least the limit of the inrush current of the current limiting device 3 is limited and at a temperature below the limit, the current limiting device 3 is bridged by the beginning of the energization of the starter motor 2 with the lock-up device 4, so that it is operated with a maximum power at the expense of a maximum voltage dip.

In a step 44, it is virtually checked during start-up of the starter motor by means of a positive control, whether a certain speed of the starter motor 2 is reached by the lock-up device 4 is controlled by a voltage drop across the starter motor 2. If this is true, so that the starter motor 2 is turned on with the inrush current, in a step 45, the lock-up device 4 is turned on positively controlled, or remains turned on, if it was already turned on due to the temperature condition. Finally, in a step 46, the starter motor 2 is operated with a bridged current limiting device 3 for full power without current limiting for starting the internal combustion engine 15. All figures show only schematic not to scale representations. Incidentally, reference is made in particular to the drawings for the invention as essential.

Claims

claims

1 . Circuit arrangement (1) for an electric machine (2), in particular a starter motor (2) for starting an internal combustion engine (15) in a motor vehicle, having a current limiting device (3) for limiting an inrush current of the electric machine (2), characterized in that the circuit arrangement (1) comprises a bridging device (4) with a controllable switching device (5) for bypassing the current-limiting device (3).

2. Circuit arrangement (1) according to claim 1, characterized in that the current limiting device (3) comprises a starting current of the e- lectric machine (2) current-limiting starting resistance.

3. Circuit arrangement (1) according to claim 2, characterized in that the starting resistor (3) is a discrete resistance element, in particular a metallic conductor.

4. Circuit arrangement (1) according to one of claims 1 to 3, characterized in that the bridging device (4) is designed as a contact closure.

5. Circuit arrangement (1) according to one of claims 1 to 4, characterized in that the bridging device (4) is designed as a contact opener.

6. A method for operating a circuit arrangement (1), in particular according to one of claims 1 to 5, for an electric machine (2), in particular a starter motor (2) for starting an internal combustion engine (15), in a motor vehicle, with a current limiting device ( 3) for limiting an inrush current of the electric machine (2), characterized in that the circuit arrangement (1) comprises a bridging device (4) with a controllable switching device (5) for bypassing the current limiting device (3) and that the inrush current the electrical machine (2) when starting by means of the current limiting device (3) limited and then the current limiting device (3) with the lock-up device (4) is bridged.

7. The method according to claim 6, characterized in that the current limiting device (3) with the lock-up device (4) time-controlled, in particular after a current limiting period, is bridged.

8. The method according to claim 6 or 7, characterized in that the

Current limiting device (3) with the lock-up device (4) speed-controlled, in particular in response to a speed of e-lektrischen machine (2) is bridged.

9. The method according to any one of claims 6 to 8, characterized in that the lock-up device (4) by a voltage, in particular on the electric machine (2) drops, is controlled, in particular by the controllable switching device (5) through the Voltage is switched.

10. Starting device (17) for starting an internal combustion engine (15) in a motor vehicle, with a circuit arrangement (1), in particular according to one of claims 1 to 5, and with a starter motor (2), characterized in that the circuit arrangement (1) a current limiting device (3) for limiting an inrush current of the starter motor (2) and a bridging device (4) with a controllable switching device (5) for bridging the current limiting device (3) and that the starting device (17) in particular for a method according to one of claims 6 to 9 is formed.