EP0691908A1

EP0691908A1 - Non-railbound vehicle with an electric motor

Info

Publication number: EP0691908A1
Application number: EP94908959A
Authority: EP
Inventors: Erich Karg; Dieter Lutz
Original assignee: Fichtel and Sachs AG; Mannesmann AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1993-04-02
Filing date: 1994-03-04
Publication date: 1996-01-17
Also published as: US5848659A; JPH08508392A; BR9405628A; DE4311230A1; DE4311230C2; JP3331218B2; WO1994022689A1

Abstract

The invention relates to a non-railbound vehicle with an electric motor. To modify such vehicles in such a way that the specific fuel consumption remains as low as possible and the maximum possible power of the internal combustion engine is fully available to the vehicle drive in case of need without the sacrifice of any convenience relating to the electrical operation of subsidiary functions, it is proposed that the control system (FST) provide the on-board low-voltage system with part of the power produced by the generator and that, during operational phases in which the full power of the engine (1) is required for propulsion, a program in the electronic control system (FST) provide for the temporary interruption (interrupter 11) of the electric power supply from the generator (2) to the low-voltage system, the subsidiary electric consumers (10) then being powered from the vehicle battery (10).

Description

Non-track-bound vehicle with an electric motor

The invention relates to a non-track-bound vehicle according to the preamble of claim 1.

From the publication "Transmissions in vehicles today and tomorrow" (VDI reports 878, 1991, pages 611-622) a drive system for non-track-bound vehicles is known which is equipped with an internal combustion engine, the output shaft of which is coupled to an electrical generator. The drive wheels of the vehicle are connected to electric traction motors, which draw their drive energy from the generator. Because of the comparatively high performance for the

The vehicle drive operates the generator in the medium voltage range (e.g. at 650 volts). For the electrical in the vehicle

Ancillary consumers such as interior and exterior lighting, fan motors, window heating, seat heating, electric windows etc.) is usually one (also for safety reasons)

Low-voltage supply (for example 12 or 24 volts) is provided, which is realized by a corresponding on-board network with a vehicle battery. Such a vehicle can also be equipped with a memory for storing drive energy, for example with a Short-term storage in the form of a flywheel storage coupled to an electrical generator or with a long-term storage in the form of an accumulator.

In conventional vehicles, the supply of electrical

Auxiliary consumers regularly through one as an alternator

designated small electrical 6 generator ensured, which is driven by the internal combustion engine. The alternator also provides the electricity necessary to charge the vehicle battery. The latter is then available for the power supply of the electrical auxiliary consumers if the generator does not have enough (the combustion engine is at a standstill) or does not have enough power (low speed, many consumers)

switched on).

In the publication VDI report 878 it is already mentioned that the function of the alternator can be taken over by the generator which generates the current for the electric drive motors. However, no further details are given.

In order to be able to supply the vehicle's low-voltage on-board electrical system from the generator, the medium voltage generated by the generator must first be reduced (above 60 volts) for the current fed in

Low voltage. With an AC generator, this transformation is possible without any problems. This also applies to generators that deliver a pulsed direct current. Suitable are for this

DC / DC converter known on an electronic basis.

The future development of non-track-bound vehicles stands

especially with regard to the drive technology under the requirement to significantly reduce the specific consumption values, i.e. the most effective use of the energy chemically bound in the fuel in the Ensure conversion to drive energy. In order to achieve a high degree of efficiency in the internal combustion engine and to make the vehicle as light as possible, the aim is to make the internal combustion engine as small as possible. This tends to mean a reduction in

Internal combustion engine performance. The maximum engine power will therefore in future be significantly closer to the average drive power required than is the case today with conventional vehicles.

This development is opposed to another development that leads to increased electricity consumption in the vehicle. The number of electrical auxiliary consumers is constantly increasing as more and more functions (e.g.

Sunroof, seat adjustment, mirror adjustment, automatic climate control, etc.) can be realized electrically. This has already resulted in a reinforced alternator or even two alternators being operated in conventional vehicles. Not only is the disadvantage of the high weight of these units to be seen, but you also have to accept a relatively poor efficiency in energy conversion. For example, to generate an electrical power of 1.5 KW, depending on the speed, a mechanical drive power in the order of 3-5 KW is required. For an internal combustion engine with 50 KW output, this is up to 10% of the theoretically available drive power. Especially from

For safety reasons (e.g. kick-down in overtaking maneuvers), one would like to be able to provide as much as possible of the maximum possible output of the internal combustion engine for the vehicle drive.

The object of the invention is to change a generic vehicle with the least possible effort so that its more specific

Fuel consumption remains as low as possible and, if necessary, the maximum possible power of the internal combustion engine for the vehicle drive is fully available without sacrificing comfort in relation to the Actuation of auxiliary functions must be accepted electrically.

This task is solved with the characteristic features of the

1. Advantageous further developments of the invention are characterized in the subclaims 2 to 6.

The invention is applicable regardless of which machine type is used as a generator (e.g. with permanent or field excitation, with or without electronic commutation) or as an electric drive motor (e.g. synchronous, asynchronous, DC motor). First of all, it provides that the electric current required in the vehicle as drive energy and for the secondary consumers only from that with the

Output shaft of the internal combustion engine coupled electrical generator is generated, so no separate alternator is used. This not only has the advantage of saving weight, but is also inexpensive because the generator enables electricity to be generated with a significantly higher efficiency than was previously the case with alternators. The use of a so-called "generator high drive", as is sometimes necessary to achieve sufficiently high speeds on the alternator at low speeds of the internal combustion engine, is completely unnecessary. All of this helps to keep the vehicle's specific fuel consumption low. The effort for this is low. Essentially, only one

Voltage converter required to convert the 5-current required for the electrical auxiliary consumers and for charging the vehicle battery from the originally generated medium voltage (preferably in the range of 60 - 1500 volts, in particular in the range up to 650 volts) to the low voltage of the vehicle electrical system (e.g. 12 or 24 volts). A particularly important feature of the invention can be seen in the fact that the electronic control of the vehicle, which is present anyway, and which, depending on the drive power requested by the driver, the operation of the internal combustion engine, the generator and the

Electric motors for the vehicle drive is influenced, expanded to the extent that in operating phases with a particularly high, i.e. at or close to, the theoretical maximum power requirement (e.g.

Kick-down) a circuit is actuated, which feed current from

Generator in the low-voltage on-board network temporarily interrupts and the power supply of the electrical auxiliary consumers is alternatively ensured from the vehicle battery. In such phases, which generally only last for short periods of time, the total maximum possible power of the internal combustion engine is then available for driving the vehicle

Available without sacrificing comfort because individual auxiliary consumers would have to be switched off. The additional power available is of course of greater importance, the lower the power for which the internal combustion engine was designed. The mobilization of these performance reserves is largely software-based, that is, possible with little effort. All that is needed is a circuit that temporarily separates the

Low voltage on-board network from the generator supply. As soon as the phase of maximum power consumption is over, the electronic control can release the feed from the generator again, so that the vehicle battery can also be recharged.

The supply to the low-voltage on-board network can take place directly (via the voltage converter) from the generator. The invention can be carried out particularly advantageously in such a way that the voltage converter for supplying the low-voltage on-board electrical system supplies the current from one

Intermediate circuit, in particular a DC link, which is connected downstream of the generator and from which the current for the electric drive motors is also taken. Since the components required for implementing the invention are operatively connected to the rest of the system by electrical lines, all freedom is given with regard to their local placement in the vehicle. This not only enables weight savings, but also optimizations with regard to weight distribution and volume utilization can be achieved.

The invention is explained in more detail below on the basis of the exemplary embodiments shown in FIGS. 1 and 2 as a block diagram. The two block diagrams each essentially represent the drive train of a non-track-bound vehicle.

In Fig. 1, an internal combustion engine 1 is coupled with its crankshaft to a generator 2 which, for example, is permanently excited

DC machine is designed with electronic commutation. The generator 2 generates an AC voltage which, after rectification in the rectifier 3, is fed into a DC voltage intermediate circuit 4. The drive energy for the operation of the electric motors 8 is taken from the DC voltage intermediate circuit 4, which e.g. are each coupled to a wheel 9 of the vehicle, not shown. The

Like the generator 2, electric motors 8 are preferably designed as permanently excited direct current machines with electronic commutation (block 7). The electric current is supplied to the electric motors 8 e.g. supplied as alternating current (block 7). The electronic control that controls the generator 2 is labeled G5T, while the electronic controls of the electric motors 8 are labeled MST; however, only one of them is shown as an example. The controls for the electric motors 8 and the generator 2 are superordinate

FST drive control overlaid. In order to distinguish the signal flow from the power flow, the former has been shown with dashed arrows. The operating voltage in the DC link 4 is in the medium voltage range, preferably around 650 volts. In addition to the electric motors 8, electric vehicles must also be in the vehicle

Ancillary consumers 10 (e.g. fans, disc heaters, etc.) are supplied with electricity. For this purpose, a low-voltage on-board network of, for example, 12 or 24 volt voltage is provided, the one

Vehicle battery 6 includes. In order to charge the battery 6 and / or to feed the auxiliary consumers 10 during normal driving, the required current is taken from the DC link 4. Since the voltage level of the DC link 4 is significantly too high, the voltage in an electronic converter 5 is reduced down to the range of the vehicle electrical system voltage. In operating phases in which the highest possible power for the vehicle drive is to be made available, the electronic control FST provides that the connection between the DC link 4 and the

Voltage converter 5 is temporarily interrupted by a switching device (breaker 11), so that the entire current generated by the generator 2 can be supplied to the electric motors 8. During these phases, the supply to the secondary consumers 10 is without

Maintain an interruption via the vehicle battery 6. As soon as the high power requirement is eliminated (e.g. termination of one

Overtaking) the connection between the

DC voltage intermediate circuit 4 and the voltage converter 5 are restored by the electronic control so that the battery 6 can be recharged and / or the auxiliary loads 10 are supplied directly from the DC voltage intermediate circuit 4.

Instead of taking a current from the DC voltage intermediate circuit 4, it is of course also possible to branch off the current for the secondary consumers 10 already at the generator 2, as is shown, for example, in FIG. 2. In order to convert the voltage to the level of

To achieve the low-voltage on-board network is a voltage converter 12 provided that the alternating voltage of the generator 2nd

transformed down and rectified. The 5 voltage converter 5 from FIG. 1 is omitted in this case. Otherwise, the function corresponds to

2 of that of FIG. 1, so that there is no need to go into this again.

It can also be provided that the generator 2 for the direct

Feeding power into the low-voltage electrical system is equipped with a special device (e.g. special low-voltage winding or circuit) so that there is no need to lower the voltage (blocks 5 or 12). In this case, too, an interruption of the feed into the

Low-voltage electrical system initiated by the FST drive control.

The principle according to the invention can also be applied without difficulty when using alternating current generators and motors. Then, of course, rectification must be carried out before being fed into the vehicle electrical system. The advantages of being able to make the full power of the combustion engine available as drive energy at all times without sacrificing comfort when a separate alternator is not required remain the same.

Claims

1. Non-track-bound vehicle, in which at least one wheel (9) for driving is coupled to an electric motor (8), which is influenced by power electronics (3, 4, 7) influenced by an electronic control (FST, GST, MST) ) is fed with electrical current in accordance with a power requirement entered by the driver via an accelerator pedal, the current being generated by a generator (2) which is coupled in terms of drive technology to an internal combustion engine (1), the current for driving the generator (2 ) with an operating voltage in the medium voltage range

(especially in the range from 100 volts to 1500 volts)

is provided and with an on-board electrical system in the

Low-voltage range (in particular below 60 volts) is present, which ensures the supply of electrical secondary consumers (10), has a vehicle battery (6) and is fed with electricity which is obtained by converting part of the mechanical energy generated by the internal combustion engine (1),

characterized,

that the control (FST) a part of the power generated by the generator (2) for feeding into the low-voltage electrical system

provides and that the program of electronic control (FST) in operating phases in which the full performance of the

Internal combustion engine (1) is required for the drive, the temporary interruption (interrupter 11) of the 5-current feed from the generator (2) into the low-voltage electrical system and the power supply of the electrical auxiliary consumers (10) is then carried out alternatively via the vehicle battery (6).

2. Vehicle according to claim 1,

characterized,

that a voltage converter (5, 12) is provided which

Feed current for the low voltage electrical system from

Medium voltage range of the generator (2) to the voltage of the

Low voltage on-board network.

3. Vehicle according to claim 2,

characterized,

that the generator (2) for generating direct current

Rectifier (3) is connected downstream that a DC link (4) is provided behind the rectifier (3), from which the electric motor (s) (8) are supplied with current for the drive, and that the voltage converter (5) as DC / DC -Converters designed and connected to the DC link (4)

connected.

4. Vehicle according to claim 3,

characterized,

that the DC link (4) is designed for an operating voltage of about 650 volts.

5. Vehicle according to claim 2,

characterized,

that the voltage converter (12) is connected directly to the generator (2) via the interrupter (11).

6. Vehicle according to claim 1,

characterized,

that the generator (2) with a special device, in particular a separate low-voltage winding, for the direct

Feed into the low-voltage electrical system.