WO2008015041A1

WO2008015041A1 - Method for the improvement of driving characteristics of a hybrid drive

Info

Publication number: WO2008015041A1
Application number: PCT/EP2007/055525
Authority: WO
Inventors: Martin Streib
Original assignee: Robert Bosch Gmbh
Priority date: 2006-08-03
Filing date: 2007-06-05
Publication date: 2008-02-07
Also published as: DE102006036217A1

Abstract

The invention relates to a method for the control of a hybrid drive (110). The hybrid drive (110) contains at least one internal combustion engine (112) and at least one electrical machine (118) with at least one electric motor function (120) and at least one generator function (122). The method is developed in such a way that at least one operating state modulation of the hybrid drive (110) is provided in which at least one operating value of the at least one electric motor function (120), in particular an electric motor torque, and/or an electric motor engine speed, and/or an electric motor engine output, is modulated with a predefined frequency spectrum. This modulation can be accomplished in particular by the fact that an electric motor voltage is put into effect with at least one amplitude modulation with at least one frequency modulation and at least one phase modulation. This serves as an active cushioning of vibration.

Description

description

title

Method for improving the driving characteristics of a hybrid drive

The invention relates to a method for controlling a hybrid drive and a

Hybrid drive, which is set up to carry out the method according to the invention and a computer program for carrying out the method. Such methods, hybrid drives and computer programs are used in particular in the field of automotive engineering.

State of the art

Various types of motor vehicles with hybrid drives are known from the prior art. Hybrid drives usually have at least one internal combustion engine and at least one electric machine. Usually, the at least one electric machine and / or the at least one internal combustion engine can be individually switched on and off during operation. Furthermore, an additional energy store is usually provided, which is usually one or more batteries and / or accumulators. From the energy storage, the electric machine is supplied with electrical energy. Conversely, from the

Electric machine to be recovered electrical energy and, for example, in a so-called braking energy recuperation, are fed back to the energy storage.

Various concepts of hybrid drives are known from the state of the art and the commercial use already taking place today. Thus, in practice, so-called parallel hybrids, serial hybrids and branched hybrids are often distinguished. These different types of hybrids may be in different operating states as needed (eg, vehicle speed, accelerator pedal signal, etc.) are operated, so that usually an optimal distribution of the load between the electric machine and the internal combustion engine is ensured. As a rule, the state of charge of the battery is always taken into account.

For example, there are operating conditions in which the internal combustion engine is completely switched off. Depending on the hybrid concept, the internal combustion engine can be disconnected from the drive train, for example, via a separating clutch in this deactivated state. The drive is then purely electric motor in this operating conditions. Preferably, this electromotive drive, if by the driver and / or environmental conditions only a small

Drive power is required. Due to the comparatively good efficiency of the electric motor, this operating state proves to be particularly energy- and exhaust-efficient in practice.

The change between different operating states, for example

Operating conditions with running internal combustion engine and operating conditions with pure electric driving, is usually audible and / or haptic perceivable even for the driver of a motor vehicle. This is due to the fact that the internal combustion engine inherently has a rotational nonuniformity. The output torque is at a speed proportional frequency (usually even a whole

Frequency spectrum) modulated, which is predetermined by the working cycles of the internal combustion engine. These vibrations are transmitted via engine mounts and powertrain in a damped form on the body and tell the driver both acoustically and by felt vibrations (haptics).

By contrast, an electric motor usually has a virtually uniform torque output. This is in principle a comfort advantage over the internal combustion engine. However, this advantage can be disadvantageous in a hybrid vehicle, namely when, when switching from an operating state to a second operating state, for example from pure electric driving to driving with

Combustion engine, without the driver understandable reason (ie usually without the driver has initiated this switching itself) abruptly the acoustic and perceived perception, ie the driving characteristics and / or driving behavior of the motor vehicle to change. Only in direct comparison between the "quiet" electrical operation and the operation of the internal combustion engine becomes clear how "loud" the combustion engine is.

Disclosure of the invention

Advantages of the invention

It is therefore proposed a method for controlling a hybrid drive, in particular for use in the motor vehicle sector, which at least largely avoids the described disadvantages of the known methods and the driving characteristics of

Vehicles with hybrid drives improved. In particular, the difference that can be heard and felt by the driver between driving with different uses of an internal combustion engine is thereby reduced. Furthermore, a hybrid drive is proposed, which is set up to carry out the method according to the invention in accordance with one of the embodiments described below, as well as a

Computer program for carrying out the method.

The hybrid drive has at least one internal combustion engine and at least one electric machine with at least one electric motor function and at least one generator function. For example, one known from the prior art

Hybrid drive can be used in one of the configurations described above.

A basic idea of the invention is that the hybrid drive is operated such that at least one modulation operating state is provided. In this at least one modulation operating state, at least one operating variable of the at least one electric motor function, in particular an electric motor torque and / or an electric motor speed and / or an electric motor power, is modulated with a predetermined frequency spectrum. Preferably, this modulation may be accomplished by modulating an electric motor current having at least one modulation amplitude and at least one modulation frequency (which may be a single modulation frequency)

Modulation frequency or can also be a modulation frequency spectrum) take place. In this way, a changed acoustics and / or changed haptics can be compensated for changes in the operation of the at least one internal combustion engine. This can be used, for example, when the at least one modulation operating state comprises at least one electrical operating state in which the at least one internal combustion engine is not operated or only reduced. In this case, it is then possible to determine, for example, one (or more) "virtual rotational speed" for the at least one internal combustion engine. The frequency spectrum of the modulation of the at least one operating variable of the at least one electric motor function can then preferably be selected according to this virtual speed. For example, this virtual speed can correspond to the speed with which the at least one internal combustion engine would have to be operated in order to operate the hybrid drive exclusively by means of the at least one internal combustion engine with unchanged instantaneous drive properties of the hybrid drive. Alternatively or additionally, the virtual speed can also correspond to the speed at which the at least one internal combustion engine would have to be operated if it were switched on in the current driving situation. The current driving situation is essentially defined by the present total torque request (the total torque must be applied by the at least one internal combustion engine in conjunction with the at least one electric motor function) and the current vehicle speed, or, at

Parallel hybrid, a transmission input speed, which in turn depends on the currently set transmission ratio.

However, it is generally not possible to derive a modulation frequency or a modulation spectrum of the at least one electric motor function directly from the virtual speed of the at least one internal combustion engine calculated in this way, since constructive properties of the at least one internal combustion engine additionally have to be taken into account. In particular, for example, the number of cylinders and / or the number of cycles of the at least one internal combustion engine should be taken into account. For example, the angular frequency of the imprinted is calculated

Modulation of the angular velocity belonging to the virtual speed multiplied by half the number of cylinders of the internal combustion engine. The factor ¹ A is due to the fact that the engine requires two revolutions until all cylinders have completed a stroke. The thus calculated modulation frequency is impressed on the at least one electric motor function. Since the torque is usually proportional to the injected current in the electric motor, a ripple of the torque output is effected by this impressed modulation, so that at a suitable modulation amplitude and / or

Modulation frequency, the behavior of the at least one electric motor function is similar to the behavior of the at least one internal combustion engine. Thus, an acoustically and / or haptic perceptible vibration is transmitted to the body in purely electrical operation. As a result, the driver no longer perceives the difference between electrical operation and operation with an internal combustion engine or only reduces it.

The modulation amplitude and / or the modulation frequency is preferably not a fixed value, but above all depends on the speed and the average output torque or the engine load. The tendency is

Modulation amplitude is greater at high load than at low load and at low speed higher than at high speed. For example, corresponding modulation frequencies and / or modulation amplitudes for predetermined operating states of the hybrid drive can be stored in a table (for example an electronic table, for example a look-up table) and retrieved as needed.

An online calculation with predetermined algorithms is also conceivable. Thus, for example, depending on the required torque and the virtual speed of the internal combustion engine, modulation amplitude and / or modulation frequency can be selected or calculated accordingly to simulate as well as possible the acoustic behavior and / or vibration behavior of the at least one internal combustion engine by means of at least one electric motor function.

The idea according to the invention can be developed advantageously in various ways. Thus, for example, the modulation can be selected such that the hybrid drive in all operating states at least substantially constant

Torque ripple and thus has a substantially same ride.

In operating states in which the at least one internal combustion engine and the at least one electric motor function are operated simultaneously ("hybrid In contrast to driving exclusively with an internal combustion engine, the at least one internal combustion engine generates less torque ripple due to the load dependency of the rotational nonuniformity To generate the same torque ripple, the at least one electric motor function can also be modulated in hybrid driving by impressing a current modulation and thus a torque modulation The amplitude of the modulation is greater, the smaller the proportion of the internal combustion engine in the total torque.

Alternatively or additionally, the described concept of the modulation of the at least one operating variable of the at least one electric motor function can also be used for vibration damping. For example, the at least one modulation operating state may include, for example, at least one damping operating state in which an active vibration damping of vibrations of the at least one internal combustion engine is brought about by the modulation of the at least one operating variable of the at least one electric motor function. This refinement can be used in particular when the at least one damping operating state comprises at least one charging operating state in which at least one energy store, in particular one, is provided by the at least one generator function

Battery is being charged.

When hybrid drive operating conditions exist in which the at least one engine generates more torque than is required in the current driving situation. The excess will be used to charge the at least one

Energy storage (for example, a battery and / or capacitors) used by the at least one electric machine with the at least one generator function is operated as a generator. Due to the increased load of the at least one internal combustion engine generates a greater torque ripple compared to an operation without charging the at least one energy storage. This increased torque

Ripple in the generator mode, which in turn makes acoustically and / or haptically noticeable to the driver, can be compensated according to the described embodiment of the invention in the damping operating state, for example, that the modulation of at least one operating size of at least one Electric motor function is adjusted accordingly. For example, a phase shift of a current modulation of the at least one electric motor function can take place, preferably by 180 degrees. With a suitable choice of the amplitude and phase shift then takes place destructive interference between the at least one of the at least one electric motor function and that of the at least one

Internal combustion engine generated vibrations, so that for example, the increased ripple by the generator operation can be completely or partially eliminated.

Moreover, the described concept of the modulation of the at least one operating variable of the at least one electric motor function is also for a general one

Vibration damping possible in other operating states. Thus, for example, one or more vibration sensors may be provided, for example on a vehicle body and / or fittings or a steering wheel of the

Motor vehicle. On the basis of the oscillations determined by this at least one vibration sensor (for example frequency spectrum and / or oscillation amplitudes and / or phases), the modulation of the at least one operating variable of the at least one electric motor function can then be carried out according to the usual calculation methods

Vibration damping take place and the at least one electric motor function are modulated accordingly.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it:

Figure 1 shows a first embodiment of a hybrid drive according to the invention in parallel hybrid arrangement;

Figure 2 shows a second embodiment of a hybrid drive in a branched arrangement; and

3 shows a schematic flowchart of an embodiment of a method according to the invention for controlling a hybrid drive. FIGS. 1 and 2 show two different exemplary embodiments of hybrid drives 110, which are intended to illustrate that the idea according to the invention can basically be used in all possible hybrid arrangements.

Thus, the exemplary embodiment in FIG. 1 shows a hybrid drive 110 in parallel hybrid

Arrangement. The hybrid drive 110 has an internal combustion engine 112 which is fueled by a fuel tank 114. On the output side, the internal combustion engine 112 is connected to an electric machine 118 via a first coupling element 116. This electric machine 118 simultaneously assumes an electric motor function 120 and a generator function 122 in the parallel hybrid arrangement according to FIG.

The electric motor function 120 is used, for example, in hybrid driving or purely electric driving. For this purpose, the electric machine 118 is connected on the output side via a second coupling element 124 with a gear 126. For example, it can be a continuous variable transmission (English: Continuous Variable Transmission, CVT) or an electric continuous variable transmission (English: Electric CVT). This transmission 126 is in turn connected to the output side with an axle gear 128, via which one or more drive wheels 130 are driven.

In the electromotive driving operation, the electric motor function 120 draws electrical energy from an energy store 132, which is shown here in the form of a battery. Alternatively or additionally, other types of energy storage 132 may be provided, such as capacitors.

Alternatively, the electric machine 118 can also be operated in generator mode, the generator function 122 being used in this operating state. This generator operation occurs, for example, during braking energy recuperation, in which kinetic energy is used via the generator function 122 and an electrical converter 134 in order to charge the energy store 132. A drive of the generator function 122 via the internal combustion engine 112 is also possible. Furthermore, a load controller 136 and a motor control device 138 are shown as components of the hybrid drive 110 in Figure 1. Both components 136, 138 can be realized, for example, with the aid of one or more microcomputer systems, for example one or more embedded systems. Such systems are known from the prior art, which are modified according to the invention in the present embodiment.

While the load controller 136 essentially serves to provide load sharing between the engine 112 and the electric machine 118, the engine controller 138 serves to control the engine 112. Both systems process demand quantities and actual quantities, such as current vehicle speed, speeds, torques, and / or the (eg by pressing an accelerator pedal) transmitted driver request. Accordingly, the load distribution between electric machine 118 and engine 112 is adjusted, i. H. Various operating states of the internal combustion engine 112 are selected. A possible operating state is, for example, the operating state already described above, in which the internal combustion engine 112 is switched off and, for example after opening of the first clutch element 116, the drive of the motor vehicle is completely taken over by the electric motor function 120. Another possible operating state is the generator operation described above, in which the generator function 112 is used for charging the energy store 132. This generator operation can in turn be subdivided into different operating states, depending on whether, for example, a braking energy recuperation takes place (opened first coupling element 116) or whether a drive of the generator function 122 takes place with the first coupling element 116 closed via the internal combustion engine 112. In addition, there are several hybrid driving conditions in which internal combustion engine 112 and electric motor function 120 jointly accomplish the drive of the motor vehicle.

FIG. 2 shows an exemplary embodiment of a hybrid drive 110 in a so-called branched arrangement. In the illustrated branched arrangement, an internal combustion engine 112 powered by a fuel tank 114 and an electric machine 118 are also provided again. In contrast to the parallel arrangement in Figure 1, however, in the electric machine 118 in the branched drive the Electric motor function 120 and the generator function 122 separated. Accordingly, the internal combustion engine 112 is connected with its output shaft initially to a transmission element 140, which is usually (which is assumed below) is a planetary gear. The transmission element 140 is in turn connected to the drive of the electric motor function 120, whose output is in turn connected to the axle gear 128. Furthermore, the transmission element 140 is connected to the drive of the generator function 122, via which the energy store 132 can be charged by means of the electrical converter 134. The electric motor function 120 can draw electrical energy directly from the electrical energy storage 132.

Once again, in the hybrid drive 110 according to FIG. 2 in the branched arrangement, a load controller 136 and a motor control device 138 are provided. The function of these components 136, 138 essentially corresponds to the function as described with reference to FIG. By means of the load controller 136, analogously to the above description, an adjustment of the operating conditions and a load distribution between the electric motor function 120 and the internal combustion engine 112. At the same time, the transmission element 140, which is usually an adjustable transmission, is usually controlled by the load controller 136 , so that, for example, the transmission ratio of the transmission another adjustable

Operating size represents.

The two hybrid drives 110 according to the exemplary embodiments in FIGS. 1 and 2 are merely exemplary representations of hybrid drives 110 in which the invention can be implemented. An example of the operation is shown in FIG

Embodiment of a method according to the invention for controlling the hybrid drive 110 shown according to one of the embodiments shown above. The process steps shown are preferably (but not necessarily) carried out in the order shown, but also additional, not shown, process steps can be performed. Also, individual can

Procedural steps are repeated or performed in parallel time. The illustrated method according to FIG. 3 can be implemented, for example, in the form of a computer program, usually realized by corresponding program code, this computer program preferably being executed on a microcomputer, for example on the load controller 136 and / or the engine control unit 138 is executed. The illustrated method steps usually proceed in addition to the usual method steps, which are provided, for example, in the load controller 136 and / or in the engine control unit 138 in order to ensure the usual operation of the hybrid drive 110 known from the prior art.

In a first method step 310, different operating parameters are read into the method. For example, this may be an actual vehicle speed and / or a current acceleration request. This reading according to step 310 already takes place in conventional

Hybrid drives 110 in order to make a corresponding motor control, for example, to calculate a corresponding torque can. Alternatively or additionally, in this step, for example, sensor signals of at least one (not shown in the figures) vibration sensor for receiving vehicle vibrations can be read.

In step 312, a corresponding determination of an operating state then takes place in the load controller 136. This step is also known in principle from conventional hybrid drives 110. In this case, for example, a load distribution between the engine 112 and electric motor function 120 takes place. For example, this can

Operating state determination based on the read in step 310 operating parameters by using on predetermined operating conditions (for example, stored in a table operating state parameters) is used. A continuous adaptation of the operating states is also conceivable.

As described above, in accordance with the operating state 110 determined in 310 in step 314, the determination of a virtual rotational speed of the internal combustion engine 112 ensues. In step 116, a suitable modulation of at least one operating variable of the at least one electric motor function 120 is determined from this virtual rotational speed. Preferably, this is a modulation of an electric motor current of the electric motor function 120. For this purpose, for example, which is designated by reference numeral 318 in FIG. 3, different modulation parameters can be read which preferably have known engine properties, in particular properties of the internal combustion engine 112 include. These modulation parameters can be stored, for example, in a table, in particular a look-up table, and contain, for example for the operating state and the determined virtual speed, optimal modulation frequencies (or modulation frequency spectra), modulation phases and / or modulation amplitudes.

The optimum modulation determined in this way for the respective operating state is then used in method step 318 in order to correspondingly control the electric motor function 120. This control can be carried out directly, for example, by the load controller 136, or a transfer of the modulation information to a separate control of the electric motor function 120, not shown in FIGS. 1 and 2, can take place. In this way, then the electric motor current with which the electric motor function 120 is operated, be modulated accordingly.

Claims

claims

A method for controlling a hybrid drive (110), wherein the hybrid drive (110) at least one internal combustion engine (112) and at least one electric machine (118) having at least one electric motor function (120) and at least one generator function (122), characterized in that at least one

Modulation operating state of the hybrid drive (110) is provided, wherein in the at least one modulation operating state of the hybrid drive (110) at least one operating variable of the at least one electric motor function (120), in particular an electric motor torque and / or an electric motor speed and / or an electric motor power a predetermined frequency spectrum is modulated.

2. Method according to the preceding claim, characterized in that the modulation is effected by a modulation of an electric motor current with at least one modulation amplitude, at least one modulation frequency and at least one modulation phase.

3. The method according to one of the two preceding claims, characterized in that the at least one modulation operating state comprises at least one electrical operating state, wherein in the at least one electrical operating state, the at least one internal combustion engine (112) is not operated or only reduced, wherein a virtual Speed is determined for the at least one internal combustion engine (112), wherein the frequency spectrum of the modulation of the at least one operating variable of the at least one electric motor function (120) is selected according to the virtual speed.

4. Method according to the preceding claim, characterized in that the virtual speed is determined according to at least one of the following methods:

- The virtual speed corresponds to the speed at which the at least one internal combustion engine (112) would have to be operated to unchanged current drive characteristics of the hybrid drive (110) to operate the hybrid drive (110) exclusively by means of the at least one internal combustion engine (112);

- The virtual speed corresponds to the speed at which the at least one internal combustion engine (112) would have to be operated, if this in the current

Driving situation would be switched on.

5. The method according to any one of the preceding claims, characterized in that further a modulation amplitude is selected.

6. The method according to any one of the preceding claims, characterized in that the modulation is selected such that the hybrid drive (110) has at least substantially constant torque ripple in all operating conditions.

7. The method according to any one of the preceding claims, characterized in that the at least one modulation operating state comprises at least one damping operating state, in which by the modulation of the at least one operating variable of the at least one electric motor function (120) an active vibration damping of vibrations of the at least one internal combustion engine

(112) is brought about.

8. The method according to the preceding claim, characterized in that the at least one damping operating state comprises at least one charging operating state, in which by the at least one generator function (122) at least one

Energy storage (132), in particular a battery is charged.

9. The method according to any one of the preceding claims, characterized in that by means of at least one vibration sensor at least one vibration of the hybrid drive (110) containing motor vehicle is determined, wherein the

Modulation of at least one operating variable of the at least one electric motor function (120) is selected to attenuate this at least one vibration.

10. Hybrid drive (110) with at least one engine control unit (138) and / or at least one load controller (136), wherein the at least one engine control unit (138) and / or the at least one load controller (136) are arranged to a method according to one of to carry out previous method claims.

Computer program with program code for carrying out the method according to one of the preceding method claims, when the program is executed on a computer or computer network, in particular on a motor control device (138) and / or a load regulator (136)