DE102005058829A1 - Electrical energy recuperating method for hybrid-vehicle, involves effecting part of desired-braking torque as long as energy storage is capable of absorbing it, and remaining part of torque is dissipated by producing lost heat - Google Patents

Abstract

The method involves determining a reference-braking torque in a recuperation operation of an electrical machine (10). An electrical parameter of the electrical machine is adjusted in such a manner that the electrical machine produces the desired reference-braking torque. A part of the desired-braking torque is effected, by producing an electrical energy, as long as an energy storage (8) is capable of absorbing it, and a remaining part of the torque is dissipated by producing lost heat. An independent claim is also included for a device for recuperating electrical energy in a hybrid-vehicle.

Description

The The invention relates to a method for recovering energy a hybrid vehicle according to the preamble of the patent claim 1 and a corresponding device according to the preamble of Patent claim 12.

hybrid vehicles In addition to the internal combustion engine usually include an electrical Machine depending on from the driving situation in either engine or generator mode is operated. In engine operation, the electric machine generates an additional Drive torque that drives the engine, e.g. in an acceleration phase supported. In generator mode, however, the delay in the Vehicle released kinetic energy into electrical energy converted (recuperation). The electrical energy thus obtained is in an energy store, such as e.g. a battery or a super cap and can in other driving situations z. B. to drive the vehicle or used to supply electrical consumers. Of the Efficiency of the vehicle can be significantly increased.

in the Recuperation operation is attempted to maximize the proportion of the desired total delay (the driver by pressing of the foot brake pedal pretends) exercise through the generator and thus gaining maximum energy back. The amount of However, generator-generated electrical energy is dependent on State of charge or capacity of the energy store. For a fully charged energy storage can only very little or no electrical energy fed into the electrical system Otherwise, the energy storage will be overloaded or voltage sensitive Consumer damaged could become. The power delivered by the generator is controlled by a regulator set.

Of the Generator generates a power-dependent braking or drag torque in recuperation mode. In principle, that the drag torque increases with increasing generation of electrical power. Because of dependence From the state of charge of the electrical energy storage, the drag torque vary greatly. When initiated by the driver braking (by activity the service brake), in which the electric machine in recuperation switched on, thus also varies the braking behavior of the vehicle corresponding. This endangers the driving safety.

Hybrid vehicles with a conventional one hydraulic or pneumatic brake system (in which a mechanical Pass-through between the brake pedal and the individual wheel brakes are therefore designed so that either only when rolling out the vehicle (not braking) energy recovered or braking Only a very small amount of energy is recovered back to the influence to keep the generator low. However, this has the essential Disadvantage that the generator of the maximum producible electrical Performance - provided the energy storage is receptive - not fully exploited and Thus, the efficiency of the vehicle can be improved only slightly can.

A maximum recovery of braking energy is i. d. R. only in hybrid vehicles with an electrohydraulic Braking system (EHB) possible, because the fluctuating braking effect of the generator in such systems can be compensated. The driver feels in this case at the same activity the brake pedal always the same braking effect. This compensation is only with electrohydraulic brake systems, but not with purely hydraulic or purely pneumatic braking systems possible.

It is therefore the object of the present invention, a method or a device for recuperation of energy in a hybrid vehicle with a conventional one hydraulic or pneumatic brake system to create with the or a constant, independent of the current state of charge of the energy storage braking behavior can be achieved.

Is solved this task according to the invention by the specified in claim 1 and in claim 12 Characteristics. Further embodiments of the invention are the subject of dependent claims.

An essential idea of the invention is to operate the electric machine in the recuperation mode such that it generates a specifiable, reproducible braking torque independently of the state of charge of the electrical energy store. This is achieved according to the invention in that at least one electrical parameter, such as a voltage, a current and / or phase angle of the electric machine is set so that the machine generates the desired desired braking torque, ei NEN part of the desired torque, if the energy storage is receptive, by generating electrical energy, and the remaining part is effected by generating heat loss. In the limit case, ie when the energy storage is fully charged, the machine is operated so that it only generates power loss. In this way, a constant relation between braking operation and total deceleration can be established, ie a predetermined brake pedal position or braking force always causes an equal generator torque and thus an equally strong vehicle deceleration, regardless of the state of charge of the energy storage. The braking torque of the electric machine can be set to a desired value, for example, within the scope of a control.

The electric machine is preferably operated such that the Proportion of the electric generator power is maximum. This can a maximum of electrical energy can be generated.

So long the energy storage receptive and the required generator braking torque is low, the electric machine is preferably in the pure Generator operation (without additional Generation of power loss) operated. When the required generator braking torque on the other hand, as high or the energy storage is so little receptive, that a maximum allowable Charging current or a maximum charging voltage would be exceeded operated the electric machine in a "mixed operation" becomes a part of the required generator braking torque - preferably a maximum possible Part - by generation electrical energy, and the remaining portion by generation of heat loss causes. When the energy store is fully charged or already Charged from the beginning, is the output from the generator electrical Energy equal to zero and only heat loss is generated. This is said to be a borderline case of "mixed Operation ".

The Height of Generator braking torque is preferably dependent on the strength of pedal operation and preferably increases with increasing pedaling, in particular linear to. The generator braking torque is physically through a maximum generator braking torque limited by the design and in particular, the heat dissipation properties depends on the generator. The recuperation system is preferably designed such that the vehicle parallel to this or a lower limit delayed by the generator and the service brake. A beyond Braking torque is then exclusive caused by the service brake.

According to one preferred embodiment The invention provides at least one phase and / or one voltage and / or a current of the electrical machine adjusted so that the generator generates a predetermined generator braking torque. For this is preferably a converter, in particular a pulse inverter controlled accordingly.

Around not to overload the energy store in the recuperation mode, must be the controller know the state of charge of the energy storage. It is therefore a device such as B. a known from the prior art state of charge detection provided that monitors the state of charge of the energy storage and transmitted to the control unit. The status recognition can also be integrated in the control unit as software.

A maximum charging current (I _max ) is preferably determined from the determined state of charge or the capacity to absorb. The maximum charging current defines the value at which the electrical machine goes into mixed operation and generates increasing power loss.

The Rekuperations system is preferably designed such that the Vehicle already delayed, though the foot brake pedal not or only slightly pressed becomes. As a result, it may happen that the brake light is not yet is active. According to the invention Therefore, the brake light is preferably activated when the vehicle deceleration exceeds the given threshold. This ensures that that subsequent drivers always receive a brake signal, even if the driver of the front vehicle does not use the brake pedal actuated.

According to one preferred embodiment According to the invention, the recuperation system is designed such that already when rolling out the vehicle (without pressing the foot brake pedal) a predetermined regenerative braking torque is generated. Thereby can additionally Energy can be saved.

The recuperation operation can either be initiated automatically or initiated by the driver, for example via a sensor integrated in the vehicle. The sensor may be, for example, a switch, button or other sensor, such as a arranged on the brake pedal pedal encoder. The sensor could Alternatively, be arranged on the steering wheel, a steering wheel lever, the shift lever or another position in the cockpit.

According to one special embodiment the invention, a pedal encoder is provided, the strength of a activity of the foot brake pedal detected. In this case, the recuperation system is set up that the height the generator braking torque from the operation of the foot brake pedal depends. By weaker or stronger Actuate of the foot brake pedal the driver can recover less or more energy. The amount of the recovered Energy can be given to the driver e.g. be displayed on a display.

alternative could the generator braking torque after actuation of the sensor also automatically, e.g. ramped, raised become.

Of the Recuperation is preferably by pressing the accelerator pedal or by an intervention of a control system, e.g. ABS or ESP interrupted or ended.

A inventive device for recuperation of energy includes a control unit that with a Inverter is connected between the electric machine and an electrical system is connected with an electrical energy storage, which is charged by the generator. The control unit controls the inverter in this way that the electric machine - depending on the state of charge of the energy storage - a given part of electrical energy and one more or less huge Part of (loss) heat generated.

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

1 a schematic block diagram of the essential elements of a Rekuperationssystems;

2 a flowchart illustrating the main steps in the recuperation of the electric machine;

3a - 3c the course of the generator braking torque and the battery charging current in dependence on the position of the brake pedal; and

4 a simplified electrical equivalent circuit diagram of the electric machine.

1 shows a schematic block diagram of the essential elements of a Rekuperationssystems in a hybrid vehicle. The hybrid vehicle includes an internal combustion engine 6 and an electric machine 10 which can be operated in both motor and generator mode. In engine operation, the internal combustion engine 6 through the electric machine 10 supported; In generator mode electrical energy is generated in an energy storage, here a battery 8th , is stored. The electrical energy obtained can be used in other driving situations, for example to drive the vehicle or to supply electrical consumers.

The electric machine 10 and the battery 8th are via a pulse inverter 9 (PWR) interconnected. The PWR 9 determines the power and operating mode of the electric machine 10 and is from a controller 4 controlled accordingly.

The control unit 4 is also with the battery 8th connected and receives various battery state variables, such as the terminal current and the terminal voltage. One in the control unit 4 Integrated battery status recognition evaluates the battery sizes and calculates the state of charge of the battery 8th , The state of charge determines the maximum charge current at which the battery is charged 8th can be charged. In recuperation mode, the maximum charging current (I _max ) must not be exceeded, as otherwise the energy storage could be overloaded or consumers could be overloaded.

The in the control unit 4 Deposited recuperation algorithm is designed such that the electric machine 10 In recuperation, a predetermined, reproducible braking torque generated - regardless of the state of charge of the electrical energy storage 8th , This is achieved in that at least one electrical parameter of the electric machine 10 , such as a voltage, current or phase angle, by means of the PWR 9 is adjusted so that the generator generates the desired generator braking torque. The proportion of the braking torque that can not be caused by the delivery of electrical power is through Generation of thermal energy causes. The essential process steps of the recuperation operation are described below with reference to FIG 2 and 3 explained in more detail.

The recuperation system further includes a brake pedal with pedal encoder 2 that takes up the driver's braking request. The pedal encoder is connected to the control unit 4 connected. The service brake is denoted by the reference numeral 1 designated. It is an arbitrary brake system with mechanical penetration between the pedal and brake actuator, such as a conventional hydraulic or pneumatic brake system (or a non-EHB brake system).

At the control unit 4 are also an accelerator pedal encoder 5 and a rule system 7 , eg ESP or ABS, connected (the control algorithm could also be in the control unit 4 be implemented). The Rekuperationsbetrieb is preferably by the operation of the foot brake pedal 2 activated. Optionally or additionally, a separate sensor could also be used 11 be provided, with which the driver can manually activate or control the Rekuperationsbetrieb.

2 shows the essential steps of a recuperation operation. The recuperation operation is in the following example by pressing the foot brake pedal 2 activated (step 15 ). The pedal encoder generates a corresponding signal to the controller 4 is forwarded.

In step 16 calculates the controller 4 based on the brake signal, a corresponding torque M _B , which is the target braking torque for the electric machine 10 represents. The relationship between the brake application or -weg and generator target torque can be specified for example by a characteristic, as in the 3a . 3b is shown.

In step 17 becomes the state of charge of the energy storage 8th determined and calculated from a maximum charging current I _max (step 18 ). If the charging current I required to implement the setpoint braking torque M _B is less than the maximum charging current I _max , the electric machine becomes 10 in pure generator mode (block 20 ) operated. In "pure generator mode", the electric machine becomes 10 or the PWR 9 controlled such that the generator 10 generates a maximum proportion of electrical power and a minimum (only due to the resistive losses) share of power loss.

When the calculated battery charging current I in step 19 on the other hand, is greater than the maximum charging current I _max , the electric machine 10 operated in a mixed operation B (step 21 ). The generator generates 10 , if possible, partial electrical power and a variable proportion of power loss, the brake request and the state of charge of the energy storage 8th is dependent.

The recuperation operation is in step 22 interrupted or deactivated when the driver again steps on the accelerator pedal or a slip controller, such as ESP or ABS engage in driving.

3a shows the brake pedal travel s over time (characteristic 23 ) 3b the desired braking torque M _{B of} the electric machine 10 (Curve 24 ) Corresponding to the brake pedal position and 3c the battery charging current I (characteristic 25 ).

In this example, the battery is 8th not fully charged and therefore can from the generator 10 continue to be charged. The charging capacity is determined by the maximum battery charge current I _max ( 3c ) limited. With a small operation of the brake pedal 2 becomes the electric machine 10 operated in purely generator mode A and the battery 8th loaded with a dependent of the pedal travel s battery current I. With greater actuation, the charging current reaches the maximum value I _max (see 3c ). After reaching the maximum battery charging current I _max , the machine goes 10 in a mixed operation B over, in which they generated in addition to the electrical power increasingly dissipated power. The charging current I remains at the maximum value I _max . The braking torque M _{B of} the electric machine 10 increases linearly with increasing pedal travel s until a limit torque M _{g is} reached.

As already mentioned, the generator operation by appropriate control of the pulse inverter 9 set. The control unit 4 supplies the pulse inverter 9 For this setpoints for various electrical state variables, such as a phase, a current or voltage value.

Various possibilities for varying the power loss of the electric machine 10 result from the following mathematical description of the electric machine 10 ,

4 shows a simplified equivalent circuit diagram of an electrical machine 10 , such as a claw pole generator. The winding of the machine 10 has an inductance L and an ohmic resistance R. The pole wheel voltage is designated by U _P. The terminal current is designated I ₁ and the terminal voltage U ₁ .

For the electric machine 10 generally applies: P 1 = P mech + P Cu . where P _{1 is} the electrical terminal power, P _mech the mechanical power (internal power) and P _Cu the ohmic power dissipation in the winding of the electrical machine 10 is. In engine operation, the sizes P ₁ and P _{mech are} positive; In generator mode, these quantities assume negative values.

For mechanical performance (internal power):

For the electrical terminal performance (mains power):

For the ohmic power loss applies:

The two powers P ₁ and P _mech can be set within certain limits independently. This makes it possible to vary the ohmic power loss P _Cu accordingly.

The different powers P _mech , P ₁ and P _Cu can be set, for example, via the two free parameters U ₁ and α, where α is the phase angle between the terminal voltage U ₁ and the pole wheel voltage U _p . From the two equations for P ₁ and P _mech , a clear solution can be determined for the two unknowns U ₁ and α. The fundamental oscillation of the terminal voltage U ₁ can be set between a value U ₁ = 0 and a maximum value U ₁ = U _max . The angle α can be set, for example, between α = 0 and α = 360 °.

The value of the parameters U ₁ , α with fully charged battery results from the following example. When the battery is fully charged, the grid power P _{1 of} the electrical machine is 10 zero, because the battery 8th can not absorb any more power. The machine 10 is therefore to be controlled so that the entire braking power of the machine 10 is converted into ohmic heat losses and no energy in the battery 8th (or the network) is fed. The maximum battery charging current I _max in this case is I _max = 0. Substituted in equation (2), the terminal voltage U ₁ results in:

For the mechanical power P _mech results:

daraus kann für den Fall P₁ = 0 als maximale Bremsleistung der Wert

bei α = 90° ermittelt werden.From this, the angle α can be determined.

From this, for the case P ₁ = 0, the value can be the maximum braking power

be determined at α = 90 °.

Because converters, such as the PWR 9 frequently do not regulate the terminal voltage U ₁ and its angle α to the rotor, but instead regulate the stator current I ₁ and the angle β of the current, the current I ₁ and its angle β to the pole wheel voltage U _p could alternatively be determined.

Claims (16)

Method for recuperation of energy in a hybrid vehicle having an internal combustion engine ( 6 ) and an electric machine ( 10 ) and an electrical system with an energy store ( 8th ), in the recuperation of the electric machine ( 10 ) is charged with electrical energy, characterized in that in the recuperation a desired braking torque (M _B ) determines and at least one electrical parameter (U, I, α) of the electric machine ( 10 ) is adjusted so that the electric machine ( 10 ) generates the desired setpoint braking torque (M _B ), wherein a part of the desired torque (M _B ), provided that the energy store ( 8th ) is caused by generating electrical energy, and the remaining part is caused by generating heat loss. Method according to claim 1, characterized in that the electric machine ( 10 ) is operated such that the proportion of electrical power is maximum. A method according to claim 1 or 2, characterized in that a maximum charging current (I _max ) of the electric machine ( 10 ) and the electric machine ( 10 ) is operated until the maximum charging current (I _max ) is reached in a pure generator mode, and after reaching the maximum charging current (I _max ) in a mixed mode (B) in which the electric machine generates a variable loss component (P _cu ). Method according to one of the preceding claims, characterized in that that of the electrical machine ( 10 ) generated in Rekuperationsbetrieb braking torque (M _B ) increases linearly with increasing increase of the driver's braking request. Method according to one of the preceding claims, characterized in that a phase (α) and / or a voltage (U ₁ ) and / or a current (I ₁ ) is varied in order to vary the portion of the power loss (P _cu ) and the desired desired braking torque (M _B ) to produce. Method according to one of the preceding claims, characterized in that the state of charge of the energy store ( 8th ) of a state recognition ( 4 ) is monitored. Method according to one of the preceding claims, characterized in that a brake light ( 3 ) is activated when the deceleration of the vehicle exceeds a predetermined threshold, even if the foot brake pedal ( 2 ) is not operated. Method according to one of the preceding claims, characterized in that the recuperation operation of the electric machine ( 10 ) is activated when the driver has an appropriate sensor ( 11 ). Method according to claim 8, characterized in that the sensor ( 11 ) a switch, button, a brake value transmitter ( 2 ) or another sensor. A method according to claim 8 or 9, characterized in that the strength of the braking torque (M _B ) of the electric machine ( 10 ) on the sensor ( 11 ) is adjustable. Method according to one of claims 8 to 10, characterized in that the braking torque (M _b ) of the electric machine ( 10 ) after pressing the sensor ( 11 ) is ramped automatically. Device for recuperation of energy in a hybrid vehicle having an internal combustion engine ( 6 ) and an electric machine ( 10 ) and an electrical system with an energy store ( 8th ) and a converter ( 9 ), which between the DC electrical system and the electrical machine ( 10 ), characterized in that a device ( 4 ) is provided, which in dependence on the height of a driver's braking request, a desired braking torque (M _B ) of the electric machine ( 10 ) and the inverter ( 9 ) such that the electric machine ( 10 ) the desired target braking torque (M _B ) partly by generating electrical energy, provided that the energy storage ( 8th ) is receptive, and on the other hand effected by generating heat loss. Device according to claim 12, characterized in that the device ( 4 ) the inverter ( 9 ) specifies a phase (α) and / or a voltage (U ₁ ) and / or a current (I ₁ ) in order to vary the proportion of the power loss (P _cu ) and to produce the desired set braking torque (M _B ). Apparatus according to claim 12 or 13, characterized in that a state recognition ( 4 ) is provided which determines the state of charge of the electrical energy store ( 8th ) and determines therefrom a maximum charging current (I _max ). Device according to one of claims 12 to 14, characterized by a sensor ( 11 ), by means of which the driver can start the recuperation operation. Device according to claim 15, characterized in that that the sensor on the steering wheel, a steering wheel lever, a shift lever or at a different location within the vehicle.