WO2008087103A1

WO2008087103A1 - Method for operating a motor vehicle generator with variable voltage

Info

Publication number: WO2008087103A1
Application number: PCT/EP2008/050301
Authority: WO
Inventors: Oliver Gerundt; Reinhard Meyer
Original assignee: Robert Bosch Gmbh
Priority date: 2007-01-16
Filing date: 2008-01-11
Publication date: 2008-07-24
Also published as: DE102007002272A1

Abstract

The invention relates to a method for operating a reserve energy accumulator (15), in particular a supercap, connected in an electrical on-board network (1) of a vehicle. The reliability of the on-board network (1) can be substantially improved when the reserve energy accumulator (15) is operated in a first operating mode in a first set of driving conditions, and in a second operating mode in a second set of driving conditions.

Description

description

title

Method for operating a variable voltage motor vehicle generator

State of the art

The invention relates to a method for operating a motor vehicle generator according to the preamble of patent claim 1.

Generators, as used in today's motor vehicles, essentially comprise a polyphase electric machine with a rectifier for rectifying the AC voltage generated by the machine. The generator output voltage is regulated by means of a generator regulator. The manipulated variable of the control is i. d. R. The current flowing through a field winding exciting current.

Known motor vehicle generators are usually driven by a belt (V-ribbed belt) from the internal combustion engine. During operation, the generator generates a generator torque (drag torque) which, depending on the level of the electrical load, acts more or less braking on the internal combustion engine. The operating state of the vehicle generator therefore influences the drive torque and the fuel consumption of the internal combustion engine.

Disclosure of the invention

It is now the object of the present invention to provide a method for operating an on-board electrical system, by means of which the reliability of the power supply and at the same time the fuel consumption can be reduced. This object is achieved according to the invention by the features specified in claim 1. Further embodiments of the invention are the subject of dependent claims.

An essential aspect of the invention is to operate a connected in the electrical system additional energy storage, especially a super-cap to operate in different driving conditions in different modes. Due to the driving state-dependent change between at least two operating modes, the energy balance and the reliability of the electrical system can be optimized as a whole.

In the first mode, the additional energy storage is charged as much as possible and maintained in the further driving operation (the engine is turned on) at a high charge or voltage level. The charging of the additional energy storage is preferably carried out in overrun mode (so-called recuperation) when the vehicle z. B. rolls or the driver or a vehicle system brakes. When driving, the additional memory is preferably not or only slightly discharged and maintains a high voltage. For vehicles that are designed for start-stop operation, the additional energy storage in the stop phases (the engine is switched off) is used to provide the electrical consumers with electrical power. The additional energy storage then discharges increasingly. After restarting the vehicle, the additional energy storage is recharged. The voltage dropping at the additional energy storage is therefore relatively high during the driving operation on average and fluctuates only slightly. In addition, the vehicle battery is spared because there is no significant cyclic loading and unloading.

In the second operating mode, the additional energy store is operated in such a way that the electrical consumers are already supplied with electrical power during driving from the additional energy store. This reduces the charge or voltage on the energy storage. The additional energy storage is then preferably recharged in the next overrun phase (recuperation). The voltage at the additional energy storage is thus lower during driving on average and shows greater fluctuations than in the first mode. As a result, the vehicle generator and the internal combustion engine are relieved, so that the fuel consumption can be reduced. According to a preferred embodiment of the invention, the additional energy storage is connected via a switching device with the generator and the electrical loads. The switching device may include one or more switches, by means of which or the energy storage can be switched on or off. The switching device may also comprise one or more diodes.

The first operating mode is preferably selected in a driving state that corresponds to a typical trip in an inner city area. The first operating mode is preferably selected in a driving state that corresponds to a driving behavior during a typical trip in an extra-urban area.

The respective driving state can be sensed and determined by evaluating one or more characteristic data. Scope and limits of driving conditions "city trip" or "overland travel" can be desired, for. B. by specifying certain ranges of values for the characteristic data, are set.

For recognizing the individual driving conditions, position data of a navigation system and / or speed data of

Speed sensors, eg. B. wheel speed sensors, and / or data that describe the driver's request, such. B. the accelerator pedal position or brake actuation, evaluated. From these data can be readily z. B. determine the driving conditions "city driving" or "overland travel".

In addition to the operating modes described above, a third operating mode is preferably also provided. The third mode is set when an acceleration request (of the driver or a vehicle system) is detected, which is a predetermined threshold, for. B. 80% of the maximum acceleration exceeds. In this case, the generator is automatically regulated to a lower voltage. As a result, the drag torque acting on the internal combustion engine decreases, so that the vehicle can accelerate faster. The electrical system is then temporarily supplied from the energy storage with electrical power. The motor vehicle generator is preferably a generator which can be regulated to a variable output voltage. The bandwidth of the control is preferably at least between 12V and 24V, or between 12V and 42V.

Brief description of the drawings

The invention will now be described by way of example with reference to the accompanying drawings. Show it:

Fig. 1 is a schematic block diagram of a multi-voltage vehicle electrical system;

Fig. 2 is a schematic diagram of the entire system for controlling a motor vehicle generator.

Embodiments of the invention

Fig. 1 shows a block diagram of a multi-voltage vehicle electrical system 1, with a first subnet 2 and a second subnet 3, which are powered by a generator 4 with electrical power. The first subnet 2 has a variable voltage range, which in the present embodiment is between 12 V and 42 V. The second subnet 3 has a fixed mains voltage of about 14 V.

The two subnets 2, 3 are connected via voltage transformers 5, 6 with each other, which present the voltage present in the first subnet 2 in the

Mains voltage of the second subnet 3 convert. The converter 5 is realized as a DC / DC converter and the converter 6 as a so-called longitudinal regulator. Optionally, only a single transducer 5 or 6 could be provided.

The first subnet 2 contains various electrical consumers 7a, 7b, which can be operated with variable voltage. These include, in particular, fans, air conditioning systems, seat heaters, auxiliary heating, etc. In the second subnet 3, such electrical consumers 8a, 8b are connected, which are dependent on a mains voltage of 14 V. These include, for example, control units, lights or the ignition system. The multi-voltage vehicle electrical system 1 is, as mentioned, supplied by a generator 4 with electrical power. The electrical power generated by the generator 4 is used, on the one hand, to operate the electrical consumers 7, 8, but is also stored in a capacitor 15 (super-cap) and a battery 13 (see FIG. The super-cap 15 is connected in the first sub-network 2 and the battery 13 in the second sub-network 3. Between the generator 4 and the super-cap 15 and the rest of the electrical system, a diode 17 is connected.

In order to increase the performance of the electrical system 1 and at the same time to reduce fuel consumption, the super-cap 15 is operated depending on the driving condition of the vehicle in different modes. In this case, a distinction is made between at least two different driving conditions, namely a city drive or a driving state that corresponds to a typical trip in the inner city area, and a cross-country drive or a driving state that corresponds to a typical trip in an extra-urban area.

In the "city driving" state, the super-cap 15 (see Fig. 2) is charged as fully as possible during the drive (the engine is switched on) .This charging is preferably carried out in coasting mode by recuperation 16 is closed during charging, the switch 16 is opened after charging, so that the super-cap 15 does not discharge in the following driving operation and the voltage dropped on the super-cap 15 remains at a high level when the vehicle has stopped and If the internal combustion engine is switched off (stop-Betheb), the switch 16 is closed, so that the electrical consumers 7, 8 are fed from the super-cap 15. After restarting the vehicle, the super-cap 15 is recharged at least while driving only to relatively low charge and discharge of the battery 13, so that the battery 13 can be spared considerably.

In the second operating mode (overland operation), the super cap 15 is also fully charged while driving. The charging is preferably again in overrun by recuperation, the generator output voltage is raised as high as possible. After charging the switch 16 remains closed - unlike in the first mode - so that the electrical loads 7, 8 are supplied from the super-cap 15. In the next Shear phase, or when the voltage at the super-cap 15 falls below a predetermined threshold, the super-cap 15 is recharged. As a result, in particular, the generator 4 and thus also the internal combustion engine are relieved during driving, which in turn can be achieved fuel savings.

The generator 4 is connected to a control unit 14 which controls the generator 4 in response to the driving condition. In the control unit, a corresponding software is stored. The switch 16 can also be controlled by the control unit 14.

The current driving state is detected by means of a suitable sensor system, which preferably comprises a position-recognition system that uses navigation data. Based on the current geographical position and the navigation data can be determined at any time, whether the vehicle moves within a city area or outside a city. The driving condition of the vehicle can also be based on driving dynamics variables such. As the vehicle speed or acceleration can be determined. The operating state "city operation" of the generator 4 may also apply outside, when the vehicle z. B. in congested traffic or in a traffic jam moves. The same applies in the case of a city trip for the "overland operation" when the vehicle z. B. moves on an inner-city highway. The conditions and limits for recognizing the individual driving states can be defined as desired.

FIG. 2 shows a schematic diagram of the overall system, the essential components of which form the generator controller 10 and the generator 4. The generator controller 10 is here with a navigation system 11 (GPS), the engine control unit 9 and a battery management control unit 12 in connection.

In operation, the navigation system 11 sends information concerning the current driving state. It may be z. B. to act information indicating whether the vehicle is moving inside or outside a city area, driving on a traffic light or drives in slow-moving traffic, etc. The engine control unit 9 provides information about the current driver's request, such. B. "accelerate" or "go from the gas". Also from this information alone or in combination with the navigation system 11 delivered Information a decision on the bethebmodus to be selected of the generator 4 are made.

The generator controller 10 is also in communication with the battery management controller 12, which provides information about the state of charge of the battery 13. From this information (if necessary, further information can be added) determines the generator controller 10, the operating strategy of the generator. 4

Claims

claims

1. A method for operating a connected in an electrical system (1) of a vehicle additional energy storage device (15), in particular a super-cap, characterized in that the additional energy storage (15) in a first driving state in a first mode, and is operated in a second driving state in a second mode.

2. The method according to claim 1, characterized in that the additional energy storage (15) held in the first mode, while driving the vehicle, at a high voltage level, and in the second mode, while driving the vehicle, for the supply of electrical consumers (7,8) is used, and therefore has a mean lower voltage.

3. The method according to claim 1 or 2, characterized in that the additional energy storage (15) is charged in overrun operation of the vehicle.

4. The method according to any one of the preceding claims, characterized in that the first driving state corresponds to a typical trip in an inner city area.

5. The method according to any one of the preceding claims, characterized in that the second driving state corresponds to a typical trip in a non-urban area.

6. The method according to any one of the preceding claims, characterized in that position data of a navigation system are evaluated to determine the current driving condition.

7. The method according to any one of the preceding claims, characterized in that speed data are evaluated to determine the current driving condition.

8. The method according to any one of the preceding claims, characterized in that the engine control unit (9) supplied data are evaluated to determine the current driving condition.

9. The method according to any one of the preceding claims, characterized in that the generator (4), when an acceleration request is detected, which is greater than a predetermined threshold, is controlled to a lower voltage to relieve the internal combustion engine.

10. The method according to any one of the preceding claims, characterized in that the generator (4) is a generator which can be regulated to a variable output voltage.