DE102010031540A1 - Method and device for operating a vehicle, which comprises at least one electric machine - Google Patents

Abstract

The invention relates to a method for operating a vehicle, which comprises at least one electrical machine, the electrical machine (2) being operated as a generator when the vehicle (1) brakes, and which is provided by the electrical machine (2) in generator operation Energy is used as useful energy to supply electrical consumers in the vehicle (1). In order to ensure a deceleration or braking effect of the electrical machine (2), to relieve the service brake system of the vehicle and to prevent a drop in performance of the service brake system, an amount of energy which is generated by the at least one electrical machine (2 ) is generated, but is not required as useful energy by the electrical consumers currently operated according to the driving state of the vehicle and / or the driver's request, by starting up at least one additional electrical consumer of the vehicle and / or at least one additional drive unit (4, 9) of the vehicle (1) and / or by shifting the operating point of at least one electrical consumer and / or at least one drive unit (4, 9) of the vehicle into heat and dissipated to the environment.

Description

State of the art

The invention relates to a method for operating a vehicle, which comprises at least one electric machine, wherein the electric machine is operated as a generator during a braking operation of the vehicle and at least partially as useful energy for supplying electrical consumers in the vehicle during regenerative operation by the electric machine is used and a device for carrying out the method.

Electric, hydraulic or hybrid vehicles usually have one or more drive units, such as electric or hydraulic motors, which are mechanically connected to at least one drive wheel, said drive units are powered by an energy storage with energy. In a deceleration or braking of the vehicle while braking energy is recovered. This is done in which the drive unit is operated as a generator and the braking energy is stored in the energy storage. For longer descents the braking effect of the drive unit is used to relieve the service brake system of the motor vehicle and a power loss of the service brake system, z. B. due to overheating of brake discs and friction liners, etc. to avoid.

The storage of the recovered braking energy in the energy storage is limited by the absorption capacity of the energy storage. Does z. B. a driver of an electric vehicle with a nearly fully charged energy storage on a longer gradient, the electric machine can not or only to a small extent generate a braking effect, since the charged energy storage, the electrical energy generated by the electric machine while driving in the generator mode, can not record. The braking power in this case must be largely generated by the service brake system. There is thus the risk of overheating of the service brake system, associated with a high risk to the vehicle occupants and the vehicle environment.

From the DE 41 42 863 A1 is a vehicle with an electric motor drive and a regenerative braking known in which during a braking operation of the vehicle, electrical energy is removed from the working as generators electric motors and useful energy is provided to the ancillaries of the vehicle. The ancillaries can consume the useful energy provided only if the connection of the ancillaries by the driver or the vehicle occupant is desired or requires the vehicle state this.

Disclosure of the invention

The inventive method for operating a vehicle having the features of claim 1 has the advantage that a deceleration or braking effect of the electric machine can be ensured at any time to relieve the service brake system of the vehicle and a power loss of the service brake system, associated with safety-critical situations , to avoid. Characterized in that an amount of energy which is generated in the braking operation of the vehicle by the at least one electric machine, but is not required by the currently operated according to the driving condition of the vehicle and / or the driver's request electrical consumers as useful energy, by commissioning at least one additional electrical load the vehicle and / or at least one additional drive unit of the vehicle and / or by shifting the operating point of at least one electrical load and / or at least one drive unit of the vehicle is converted into heat and dissipated to the environment, it is ensured that the excess amount of energy completely degraded and the electric machine applies a maximum possible braking assistance to the vehicle, for example if the absorption capacity of an energy store is reduced.

Among the currently operated according to the driving condition of the vehicle and / or the driver's request electrical consumers only those consumers are understood, which are required depending on the current driving condition of the vehicle or the driver's request. The driving condition and / or the driver's request also determine the power with which these consumers are operated. For example, the instantaneous cooling requirement of powertrains and consumers may determine the instantaneous power of a variable-power electrical coolant pump. The electrical consumers currently actuated according to the driving state of the vehicle and / or the driver's request do not include the electrical consumers put into operation in accordance with the method according to the invention.

The term "energy" is understood in the present embodiments, an amount of energy per unit time in terms of performance. Ie. The terms energy amount and useful energy also mean corresponding services such as a benefit amount and a net benefit

Advantageously, the amount of energy is determined from the difference between the regenerated energy of the at least one electric machine and the current required by the driving state of the vehicle and / or the driver's request electrical consumers needed and / or recorded by one or more energy storage useful energy. The determination of the difference amount of the energy generated by the electric machine in regenerative operation and the power consumed by the electrical consumers or one or more energy stores allows a precise strategy, which further consumers or drive units put into operation and / or which consumers or Drive units must be moved at its operating point to consume the difference calculated.

In one embodiment, the useful energy corresponds to the energy that is required by the currently operated according to the driving condition of the vehicle and / or the driver's request electrical consumers at the best possible efficiencies and / or the energy storage or the maximum can be accommodated. In this case, the driving state of the vehicle or the driver's request determines which electrical consumers are actuated and with what power they are required. For example, this is done by the driver turning on an indoor fan and specifying one of several fan levels. The useful energy is determined by the operation in operating points with the best possible efficiencies is based on the operated according to the driving condition of the vehicle and / or the driver's desire electrical operation. This results in a basis or a defined starting point for the inventive shift of the operating points. This allows a precise strategy, as well as the consideration of the maximum of the energy storage recordable energy.

Potential consumers may include an air conditioning compressor, an interior electric heater, an electric heater for controlling the temperature of an aggregate, an electric cooling water heater, a window heater, a ventilation, a radiator fan, pumps, power steering, lighting, radio, controllers, a fuel cell compressor, and so on.

In a further development, with an increase in the amount of energy which can not be utilized as useful energy, a plurality of additional electrical consumers and / or the at least one additional drive unit are put into operation successively at different times. By gradually switching on the additional consumers, the consumption of the difference can be adjusted well, so that only as many consumers are put into operation as are needed to destroy the excess energy.

In one variant, with an increase in the amount of energy which can not be utilized as useful energy, a plurality of consumers and / or drive units of the vehicle are brought one after the other at different times into a changed operating point. This ensures that more electrical energy is converted into heat or heat energy, which is delivered to the environment of the motor vehicle. In an electric machine, this is done for example by influencing the magnetization of the electric machine, the choice of a suitable speed of the electric machine by changing a ratio or by using an eddy current brake.

Advantageously, the changed operating point of the at least one consumer and / or drive unit of the vehicle is characterized by an increased power and / or a low efficiency. An increased performance can z. B. be achieved by increasing the speed of a fan or a pump, a lower efficiency results in an electric machine z. B. by influencing the magnetization.

In another embodiment, the additionally commissioned and / or shifted in the operating point, electrical consumers and / or drive units of the vehicle are monitored by a cooling system, which increases the power loss of the additionally commissioned and / or shifted at the operating point at least one electrical load and / or the at least one drive unit provides an increased cooling capacity. As a result, the formation of heat by the electrical consumers and the drive units is counteracted, so that overheating and influencing the vehicle occupants are prevented by the additional heat released.

In a further development, at least one energy store in a charging process is charged only incompletely to absorb the energy generated during the braking process of the vehicle by the electric machine operating in generator mode. This ensures that during a braking operation of the vehicle at least one energy storage device is capable of receiving the energy provided by the electric machine.

In a further variant, a starting state of charge of the at least one energy store is adapted over a plurality of journeys of the motor vehicle, wherein the starting state of charge of the energy store is lowered continuously. This option is particularly advantageous whenever a daily recurring trip begins with a long downhill. The starting state of charge of the at least one energy storage is z. B. on the basis of incurred during the previous trips energy amount, which can not be utilized as useful energy and / or based on route data, eg. B. a navigation device adapted

In one embodiment, the amount of energy that is generated in the braking operation of the vehicle by the at least one electric machine, but is not required by the currently operated according to the driving condition of the vehicle and / or the driver's request electrical consumers, estimated when the at least one Energy storage and the actuated electrical consumers record the electrical energy generated by the electric machine during braking operation when the absorption capacity of the at least one energy storage device falls below a predetermined threshold. Such an allowance allows a quick response to changes in braking power and protection of the energy storage by an overload of the energy storage and thus overheating of the same is avoided.

Advantageously, the connection of the number of additional electrical loads or the additional drive units and / or the shift of the operating points of the number of electrical loads or the drive units takes place in dependence on the capacity of the at least one energy storage and / or the energy amount. As a result, it is possible to react flexibly to the changing absorption capacity of the at least one energy store. The more the absorption capacity of the at least one energy store decreases, the more the number of additionally connected consumers or drive units increases.

By influencing the additional electrical consumers and / or additional drive units, a minimum braking effect of the electric machine is ensured. If there is no generation of a minimum energy by the generator-operated electric machine during braking operation of the vehicle, a warning message is output to the driver. It is assumed that a defect or a reduction of the electrical machine, an energy storage, consumers or drive units or a controller.

A further development of the invention relates to a device for operating a vehicle, which comprises at least one electric machine, wherein the electric machine is operated as a generator during a braking operation of the vehicle and the energy provided in the generator mode by the electric machine as useful energy for supplying electrical consumers used in the vehicle. In order to ensure a deceleration or braking effect of the electric machine in order to relieve the service brake system of the vehicle and to prevent a drop in performance of the service brake system, means are provided which an amount of energy generated in the braking operation of the vehicle by the at least one electric machine, but of the according to the driving condition of the vehicle and / or the driver's request operated electrical consumers is not required as useful energy, by commissioning at least one additional electrical load of the vehicle and / or at least one additional drive unit of the vehicle and / or by shifting the operating point of at least one electrical load and / or convert at least one drive unit of the vehicle into heat and dissipate it to the environment. This ensures that the excess amount of energy is completely reduced and the electric machine applies a maximum possible brake support for the service brake system of the motor vehicle, z. B. if the absorption capacity of the at least one energy storage is limited.

Advantageously, the vehicle has a first electric machine as a drive unit, an energy store and a combination of an internal combustion engine and a second electric machine, wherein in the braking mode of the vehicle, the second electric machine is driven by the first electric motor and drags the internal combustion engine. Since the internal combustion engine is not ignited, but only rotates mechanically, the energy provided by the first electric machine during the braking process of the motor vehicle is converted into heat by the mechanical movement of the internal combustion engine and thus degraded.

In one embodiment, a, a speed of the second electric machine varying control device is connected to the first electrical machine.

By changing the speed of the second electric machine, the rotational movement of the internal combustion engine and thus the Amount of energy that is released as heat to the environment.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing:
It shows:

1 : Schematic representation of a hybrid vehicle with a range extender

In 1 is a hybrid vehicle 1 with a serial drive with a first electric machine 2 shown, which with a serving as energy storage battery 3 and a second electric machine 4 connected is. The first electric machine 2 is via a differential gear 5 via drive shafts 6 with the drive wheels 7 . 8th of the vehicle 1 connected. The second electric machine 4 is to an internal combustion engine 9 coupled. Such a combination of internal combustion engine 9 and second electric machine 4 is called a range extender. In normal operation drives the internal combustion engine 9 the second electric machine 4 whose energy from the first electric machine 2 is used to propel the vehicle when the energy of the battery 3 not enough. The second electric machine 4 can in regenerative operation the battery 3 charge while the first electric machine 2 over the differential gear 5 the drive wheels 7 . 8th of the vehicle 1 drives.

Furthermore, the first 2 and the second electric machine 4 with a control unit 10 connected, which is the two electrical machines 2 . 4 , the internal combustion engine 9 and the battery 3 controls.

In the purely electric driving of the hybrid vehicle 1 is the internal combustion engine 9 off. The drive to the vehicle 1 necessary energy gets from the battery 3 to the first electric machine 2 delivered. To brake or decelerate the hybrid vehicle 1 becomes the first electric machine 2 operated as a generator, that is, the mechanical energy of the wheels 7 . 8th from the first electric machine 2 is converted into electrical energy. The electrical energy generated in this way is taken from the battery 3 added. This increases the state of charge of the battery 3 , which increases the energy absorption capacity of the battery 3 reduced. At high battery level 3 reduces the power capacity of the battery 3 also.

Below the capacity of the battery 3 a predetermined threshold, which may be the case, for example, when driving on long slopes, so is the operating point of the range extender 4 . 9 through the control unit 10 affected. This is the second electric machine 4 put into operation and operated by motor. That is, the second electric machine 4 that from the first electric machine 2 supplied electrical energy absorbs. Because the second electric machine 4 stuck with the combustion engine 9 is powered by the second electric machine 4 the internal combustion engine 9 hauled, which means that the internal combustion engine 9 mechanically turning, but no fuel injection is triggered. This has the consequence that in the internal combustion engine 9 no ignition takes place and thus an independent movement of the internal combustion engine 9 is prevented. By varying the speed of the second electric machine 4 and / or the internal combustion engine 9 by the control unit is the towing power of the engine 9 and with it the second electric machine 4 recorded electrical energy varies as needed, so that always a maximum braking power through the first electric machine 2 is guaranteed.

The towing capacity of the internal combustion engine 9 but can also be changed by influencing a throttle. If necessary, as an engine brake, an additional, not shown throttle in the exhaust pipe of the engine 9 used to the towing power and that of the second electric machine 4 increase absorbed electrical energy. By doing so, the first electric machine generates 2 a braking performance, even if the battery 3 can no longer absorb energy or power.

Also in the case where a mechanical connection between the range extender 4 . 9 and the drive wheels 7 . 8th is switched, which can be done by a switchable clutch, the described serial operation of the hybrid vehicle benefits by the need-based adjustment of the second electric machine 4 absorbed energy. There are no negative effects on the ride comfort as a result of the shifting process on the shiftable clutch. This mechanical connection can be used as a fallback level, if z. B. the first or the second electric machine 2 . 4 fails.

Alternatively or additionally, the deterioration of the efficiency of an electrical component occurs when the capacity of the battery 3 falls below a predetermined threshold. For example, this is done by the first electric machine 2 is brought by influencing the magnetization at a constant torque in a low-efficiency operating point and the mechanical energy of the wheels 7 . 8th for the most part be converted into heat and dissipated to the environment.

Alternatively and additionally, the power of an electrical component is increased when the capacity of the battery 3 falls below a predetermined threshold, z. B. by an increased power consumption of a cooling fan or a coolant pump is adjusted by speed increase, without an increased cooling would be required. Also an air conditioning compressor, a heat pump or a compressor for compressed air supply, eg. B. for a fuel cell system, can be operated at increased power. The additional power is not used, but stored or converted into heat and discharged for example via a radiator or a throttle point to the environment. In addition, the power transferred by a DC / DC converter from a traction on-board network to a low-voltage on-board network can be increased. The efficiency of an entire battery system is z. B. worsened by an associated cooling fan or a coolant pump can be operated with increased power without increased cooling of the battery 3 would be required.

Can z. B. as a result of a defect or a reduction in over- or under-temperature, z. B. the first electric machine 2 or the second electric machine 4 , a braking effect by the drive train are not or only incomplete generated, a warning message to the driver.

Another application for the solution according to the invention is when starting on a hill or a slope. The approach on the mountain is carried out by a forward, ie uphill driving (positive) torque of the first electric machine 2 on the drive wheels 7 . 8th , If a travel movement in the forward direction, ie uphill, occurs immediately, the result is a positive rotational speed of the first electric machine 2 , connected with a motor operation. However, if the driver gives an excessively low positive torque for the first electric machine 2 before, so can the vehicle 1 during the starting process, ie, roll downhill, connected to a negative speed of the first electric machine. With positive torque and negative speed of the first electric machine 2 results in a regenerative operation, wherein the first electric machine 2 provides electrical energy. If this electrical energy can not be dissipated, the positive torque collapses and the vehicle collapses 1 accelerates further backwards, ie downhill. A start in the forward direction is then no longer possible. This misconduct is reliably prevented by the method according to the invention. Corresponding conditions arise in a driver, z. B. by a selector lever position "R" desired backwards, ie uphill start on a slope.

Also when starting a hybrid vehicle, in which an electric machine z. Example, with the aid of a planetary gear the function of a starting clutch for the adaptation of different speeds takes over and is operated as a generator, the solution according to the invention can be used.

The inventive solution can also be used in vehicles with hydraulic or pneumatic drive units, consumers and energy storage.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 4142863 A1 [0004]

Claims (15)

Method for operating a vehicle, which comprises at least one electric machine, wherein the electric machine ( 2 ) during a braking operation of the vehicle ( 1 ) is operated as a generator and in generator mode by the electric machine ( 2 ) provided energy as useful energy for the supply of electrical consumers in the vehicle ( 1 ), characterized in that an amount of energy which, in the braking operation of the vehicle ( 1 ) of the at least one electrical machine ( 2 ) is generated, but of the momentary according to the driving condition of the vehicle ( 1 ) and / or the driver's request actuated electrical consumers is not required as useful energy, by commissioning at least one additional electrical load of the vehicle and / or at least one additional drive unit ( 4 . 9 ) of the vehicle ( 1 ) and / or by shifting the operating point of at least one electrical load and / or at least one drive unit ( 4 . 9 ) of the vehicle ( 1 ) is converted into heat and dissipated to the environment. A method according to claim 1, characterized in that the amount of energy from the difference between the regenerated energy of the at least one electric machine ( 2 ) and the currently of the according to the driving condition of the vehicle ( 1 ) and / or the driver's request actuated electrical consumers needed and / or one or more energy stores ( 3 ) is determined. Method according to Claim 1 or 2, characterized in that the useful energy corresponds to the energy which currently depends on the driving condition of the vehicle ( 1 ) and / or the driver's request actuated electrical consumers is required at the best possible efficiencies and / or of the one or more energy storage ( 3 ) can be recorded at maximum. Method according to at least one of claims 1, 2 or 3, characterized in that with an increase in the amount of energy that can not be utilized as useful energy, several additional electrical consumers and / or the at least one additional drive unit ( 4 . 9 ) are put into operation successively at different times. A method according to claim 1, 2, 3 or 4, characterized in that with an increase in the amount of energy, which can not be utilized as useful energy, several consumers and / or drive units ( 4 . 9 ) at different times in a changed operating point. A method according to claim 1 or 5, characterized in that the changed operating point of the at least one consumer and / or drive unit of the vehicle ( 1 ) is characterized by increased power and / or low efficiency. A method according to claim 6, characterized in that the additional commissioning and / or displacement of the operating point of at least one electrical load of the motor vehicle ( 1 ) and / or at least one drive unit of the vehicle ( 1 ) is monitored by a cooling system which, upon increasing a power loss of the at least one electrical load and / or the at least one drive unit ( 4 . 9 ) provides an increased cooling capacity. A method according to claim 1, characterized in that for receiving the during the braking operation of the vehicle ( 1 ) by the operating in generator mode electrical machine ( 2 ) generated energy, at least one of the energy storage ( 3 ) is charged only incompletely in a charging process. Method according to claim 8, characterized in that a starting state of charge of the at least one energy store ( 3 ) over several journeys of the vehicle ( 1 ), wherein the starting state of charge of the energy store ( 3 ) is lowered continuously. A method according to claim 1, characterized in that the amount of energy which, in the braking operation of the vehicle ( 1 ) of the at least one electrical machine ( 2 ) is generated, but of the momentary according to the driving condition of the vehicle ( 1 ) and / or the driver's request actuated electrical consumers is not required as useful energy is estimated when the at least one energy storage ( 3 ) and the electrical consumers operated by the electrical machine ( 2 ) record electrical energy generated during braking operation when the Absorption capacity of the at least one energy store ( 3 ) falls below a predetermined threshold. A method according to claim 10, characterized in that the connection of the number of additional electrical consumers or the additional drive units ( 4 . 9 ) and / or the shift of the operating points of the number of electrical consumers or of the at least one drive unit ( 4 . 9 ) as a function of the absorption capacity of the at least one energy store ( 3 ) he follows. Method according to at least one of the preceding claims, characterized in that in the absence of generation of a minimum energy by the regenerative electric machine ( 2 ) in the braking operation of the vehicle ( 1 ) a warning message is issued to the driver. Device for operating a vehicle, which comprises at least one electric machine, wherein the electric machine ( 2 ) during a braking operation of the vehicle ( 1 ) is operated as a generator and in the generator operation by the electric machine ( 2 ) energy is used as useful energy for the supply of electrical consumers in the vehicle, characterized in that means are present which an amount of energy, in the braking operation of the vehicle from the at least one electric machine ( 2 ) is generated, but of the momentary according to the driving condition of the vehicle ( 1 ) and / or the driver's request actuated electrical consumers is not required as useful energy, by commissioning at least one additional electrical load of the vehicle ( 1 ) and / or at least one additional drive unit ( 4 . 9 ) of the vehicle ( 1 ) and / or by shifting the operating point of the at least one electrical load and / or the at least one drive unit ( 4 . 9 ) of the vehicle ( 1 ) convert into heat and dissipate to the environment. Device according to claim 13, characterized in that the vehicle ( 1 ) a first electric machine ( 2 ) as a drive unit, an energy store ( 3 ) and a combination of an internal combustion engine ( 9 ) and a second electrical machine ( 4 ), wherein in the braking operation of the vehicle, the second electric machine ( 4 ) from the first electric machine ( 1 ) and the internal combustion engine ( 9 ) drags. Apparatus according to claim 14, characterized in that one, a rotational speed of the second electric machine ( 4 ) varying control device ( 10 ) with the first electric machine ( 2 ) connected is.

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