Method and device for torque control of a hybrid motor vehicle

Abstract

Method for torque control of a motor vehicle with a hybrid drive unit (10) which comprises an internal combustion engine (12) and at least one electric machine (14) which can be operated either as a motor or as a generator, wherein the electric machine (14) supplies a positive or negative electromotive torque (M_EM) which, together with an internal combustion engine torque (M_VM), represents a total drive torque (M_Fzg) of the drive unit (10), and wherein, in the presence of a desired torque (M_W) which is greater than a currently provided total drive torque (M_Fzg) of the drive unit (10), (a) in an initial boost phase (B), a dynamic, positive, electromotive torque (M_EM) is imposed on the combustion engine torque (M_VM), which reaches a maximum during the boost phase (B), and (b) in a second phase (S, L) for a predeterminable duration, a predeterminable, constant, positive electromotive torque (M_EM) is impressed on the combustion engine torque (M_VM), which lies below the maximum of the electromotive torque (M_EM) in the boost phase (B), so that the resulting total drive torque (M_Fzg) corresponds to the desired torque (M_W), wherein the level of the electromotive torque (M_EM) is predetermined as a function of the desired torque (M_W), characterized in that, if the desired torque (M_W) is greater than the maximum combustion engine torque (M_VMmax) and at the same time a pedal value (PW) of a pedal value sensor is 90 to 100%, a neutral phase (N) is carried out following the second phase, in which the electric machine (14) is operated with a zero torque and at the end of the neutral phase (N) the electromotive torque (M_EM) is reduced to a negative value is controlled.

Description

[0001] The invention relates to a method for controlling the drive torque of a motor vehicle with a hybrid drive unit comprising an internal combustion engine and at least one electric machine that can be operated selectively in motor or generator mode. The electric machine delivers a negative electromotive torque in generator mode and a positive electromotive torque in motor mode, and the electromotive torque, together with an internal combustion engine torque, represents a total drive torque of the drive unit. The invention further relates to a hybrid vehicle with a corresponding torque control system.

[0002] The term "hybrid vehicle" refers to motor vehicles in which at least two drive units are combined, each drawing on different energy sources to provide the power needed to propel the vehicle. The properties of an internal combustion engine, which generates kinetic energy through the combustion of gasoline or diesel fuel, and an electric motor, which converts electrical energy into kinetic energy, complement each other particularly advantageously. Today's hybrid vehicles are therefore predominantly equipped with a combination of an internal combustion engine and one or more electric motors. Two different hybrid concepts can be distinguished.In so-called serial hybrid concepts, the vehicle is powered exclusively by the electric motor, while the combustion engine generates the electrical power via a separate generator to charge an energy storage device that feeds the electric motor or to directly power the electric motor. In contrast, parallel hybrid concepts are preferred today, at least in passenger car applications, where the vehicle can be powered by both the combustion engine and the electric motor.

[0003] The electric machines used in such parallel concepts can be operated either as a motor or as a generator. For example, the electric motor in motor mode is typically switched on at operating points with higher vehicle loads, supporting the combustion engine. It can also assume the function of a starter motor for the combustion engine. In contrast, the electric motor in a combustion engine-powered drive system is predominantly operated as a generator, with the electrical power generated by the electric motor being used, for example, to charge the energy storage device and / or to supply an on-board electrical system. In the case of a power-split hybrid concept with more than one electric motor, the generator operation of one electric motor can also be used to feed another.Furthermore, at least part of the braking power is usually provided by the generator-driven electric motor (regeneration), whereby part of the mechanical energy loss is converted into electrical energy. In hybrid concepts, it is generally advantageous that the electric motors operate with greater efficiency than conventional claw-pole generators.

[0004] The goal of controlling the so-called boost function—the supporting parallel use of the electric motor, for example, to increase the overall drive torque of the hybrid drive—is, on the one hand, to achieve the most significant improvement in driving performance, while, on the other, also to provide reproducible driving behavior without negative effects on driving performance, for example, in the form of undesirable torque fluctuations or "torque drops." The boost function requires high electrical power from the electric motor's electrical energy storage unit. Due to the limited performance of the energy storage unit—the energy content of an electrical energy storage unit typically corresponds to only a fraction of the energy stored in the fuel tank—suitable strategies for implementing this boost function are required.Energy storage devices with low energy content, such as capacitor storage devices, place particularly high demands on the control system.

[0005] US 2003 / 0 160 455 A1 discloses a hybrid powertrain comprising an internal combustion engine, a regenerative brake, an electric drive motor, and an electrical energy storage device, such as a battery. The internal combustion engine is preferably a diesel engine with programmable injection events and programmable intake and exhaust valves. The regenerative brake / regenerative motor is capable of operating both as an electric generator and as an electric motor.

[0006] DE 198 58 348 B4 describes a vehicle drive system with an internal combustion engine coupled to a coupled electric machine, in which the internal combustion engine and the electric machine interact to generate torque, with an external control input directly affecting the control of the electric machine. The internal combustion engine is controlled indirectly, depending on an intermediate circuit voltage of an electrical system supplying the electric machine, with the electric machine being controlled by an intermediate circuit inverter.

[0007] A parallel hybrid electric vehicle is known from US Pat. No. 6,367,570 B1. An electric motor strategically supports the combustion engine. This arrangement can increase drivability and ensure a very smooth vehicle. Lower emissions are achieved by operating the engine in a manner that minimizes emissions. Fuel consumption is significantly reduced by efficiently generating the required power.

[0008] DE 103 18 882 A1 describes a device and a method for energy management in a motor vehicle, comprising an internal combustion engine and at least one electric machine, wherein the electric machine can be operated at least as a generator, generator operation of the electric machine can be enabled by the internal combustion engine when a charge state threshold value is undershot, and a power output of the electric machine can be limited at least as a function of the charge state of the battery.

[0009] Furthermore, DE 103 46 720 A1 discloses a vehicle control device for reliably preventing the generation of fluctuations by improving the setting of a threshold value, and capable of achieving stable motor drive regardless of the state of a battery. Therefore, an electronic control unit performs control for a vehicle that includes a motor and a battery for supplying electric power to drive the motor, and can charge the regenerative electric power of the motor.

[0010] The object of the present invention is therefore to propose a control system for torque coordination between the internal combustion engine and the electric motor that ensures efficient and demand-oriented use of the supporting electromotive drive torque of the electric motor when the driver requests torque. Furthermore, a suitable torque control system for implementing the method is to be provided.

[0011] This object is achieved by a method and a torque control system having the features of the independent claims. The method according to the invention provides that when a torque request is made by the driver, i.e., when a desired torque is present that is greater than the currently available drive torque of the drive unit, (a) in an initial boost phase, a dynamic positive electromotive torque is imposed on the combustion engine torque, which reaches a maximum during the boost phase, and (b) in a second phase, a predeterminable, substantially constant positive or negative electromotive torque is impressed on the combustion engine torque for a predeterminable duration, so that the resulting total drive torque corresponds at least approximately to the desired torque, the sign and / or magnitude of the electromotive torque being predetermined as a function of the desired torque.

[0012] By applying the dynamic positive torque of the electric motor to the accelerating internal combustion engine torque during the initial boost phase, a rapid and relatively smooth ramp-up of the total drive torque is achieved. By passing through a maximum of the electromotive torque, i.e., by initially increasing and then decreasing during the boost phase, the disproportionately increasing torque of the internal combustion engine is supplemented in a substantially linearly smoothing manner. By specifying the sign and / or magnitude of the electromotive torque in the second phase as a function of the desired torque, in particular as a function of a difference between the desired torque and the drive torque delivered by the internal combustion engine, the electric motor is used in a particularly needs-based manner, taking into account the limited energy content of the energy storage device.

[0013] In the context of the present invention, the term “impression of the electromotive torque” is understood to mean the addition of a positive (motor) torque of the electric machine to the torque of the combustion engine or the reduction of the total drive torque by subtracting the negative “recuperation torque” of the electric machine when it is operated as a generator.

[0014] The invention takes advantage of the fact that the electric motor, due to its typical torque characteristics, operates predominantly in the lower speed range, which is typically found in hybrid drives up to a speed limit of approximately 3000 to 3500 rpm -1can be used to effectively increase driving performance. In contrast, combustion engines have relatively lower torques at lower engine speeds. This is especially true for turbocharged combustion engines, which are supplied with compressed combustion air via a turbocharger. These engines exhibit particularly low torques during dynamic operation at low engine speeds, typically below 2000 to 3000 rpm. -1 , a so-called "turbo lag," which can be ideally compensated for by the electromotive torque. The present invention can therefore be used particularly advantageously in turbocharged internal combustion engines. In principle, however, it can also be used advantageously for any other internal combustion engine in combination with an electric motor.

[0015] In a preferred embodiment of the invention, essentially three boost functions are distinguished in three different scenarios. In the first case, a very high pedal value of a pedal value sensor (accelerator pedal) of at least 90%, in particular at least 95%, preferably approximately 100%, is present, and at the same time, a desired torque is greater than the maximum combustion engine torque, in particular a maximum desired torque. In this first scenario, which occurs, for example, during overtaking maneuvers at already high speeds, the aim is to achieve the highest possible and longest possible assistance from the electric motor.

[0016] In the second scenario, a desired torque is also present that exceeds the maximum combustion engine torque, but the accelerator pedal is not fully depressed, meaning the pedal pressure falls below the limits specified for the first scenario. In this case, the electric motor also provides high to maximum support of the total drive torque in the initial boost phase and the subsequent second phase, but the total duration of the electric motor support is shorter than in the first scenario.

[0017] Finally, according to the third scenario, there is also a torque request from the driver, but the resulting desired torque is less than the maximum combustion engine torque. Typically, the pedal value in such situations corresponds to a relatively low value, for example, it falls below a threshold of 50%, preferably 40%, particularly preferably 30% of the maximum pedal value. In this phase, the initial boost phase also sees dynamic assistance from the electric motor, albeit with a lower assisting torque. Since the requested desired torque can then be provided solely by the combustion engine, no further assistance is provided by the electric motor; it is either switched to torque-free or deactivated, or operated as a generator if necessary.

[0018] According to the invention, the second phase is carried out as a support phase, i.e., the electric machine is operated as a motor with a positive electromotive torque if the desired torque is greater than or equal to a maximum combustion engine torque. This is the case in the first two of the described scenarios. If, on the other hand, the desired torque is less than the maximum combustion engine torque (scenario 3), the second phase is carried out as a charging phase, in which the electric machine is operated as a generator with a negative electromotive torque, or as a neutral phase, in which the electric machine is switched to torque-free or deactivated. This occurs depending on the charge and / or aging state of the energy storage device, as well as on the current on-board electrical system requirements.

[0019] A further advantageous embodiment of the invention provides that the duration of the second phase and / or the magnitude of the electromotive torque during it is predetermined depending on the state of charge (SOC) and / or the state of health (SOH) of the electrical energy storage device of the electric motor and / or depending on the current speed of a crankshaft, in particular a common one, of the hybrid drive unit. In this way, the use of the electric motor is, on the one hand, tailored to what the driver desires and, on the other hand, limited by the state of the energy storage device, i.e., what is possible.

[0020] According to the invention, if the desired torque is greater than the maximum combustion engine torque, in particular, if it is maximum, and at the same time a pedal value is between 90 and 100%, preferably 95 to 100%, and particularly preferably approximately 100%, a neutral phase is carried out following the second phase, in which the electric motor is operated with zero torque or deactivated. In this way, the delivered maximum combustion engine torque is passively supported by the electric motor, in that no braking torque of the generator-driven electric motor reduces the total drive torque.

[0021] The torque control according to the invention is a digital program algorithm, which is preferably stored in a hybrid control or in an extended engine or transmission control, which executes the previously executed steps of the method according to the invention in the event of a torque request.

[0022] Further advantageous embodiments of the invention are the subject of the remaining subclaims.

[0023] The invention is explained below in exemplary embodiments with reference to the accompanying figures. They show: Fig. 1 schematically shows the structure of a hybrid drive unit according to the invention; Fig. 2 Time courses of a combustion engine and electric motor torque, a total drive torque of a hybrid drive according to Fig. 1 and a desired torque according to the present invention at maximum torque request and maximum pedal value (full load); Fig.3 Time courses of the torques as in Fig. 2 at maximum torque requirement and a non-maximum pedal value (high load) and Fig. 4 Time courses of the torques as in Fig. 2 at partial load.

[0024] In Fig.1, 10 designates a parallel hybrid drive unit of a hybrid vehicle (not shown in detail). The vehicle is driven selectively or simultaneously by a conventional internal combustion engine 12 (gasoline or diesel engine) and an electric motor 14 (electric machine, e-machine), both of which act on the same shaft, in particular the crankshaft of the internal combustion engine 12. The internal combustion engine 12 is supplied with compressed charge air via a charger (not shown), in particular an exhaust gas turbocharger. The electric motor 14 can be connected to the engine crankshaft in various ways. For example, the electric motor 14 can be connected to the crankshaft directly or via a clutch, or via a belt drive, for example a toothed belt, or a transmission, or another non-positive and / or positive connection.The internal combustion engine 12 and the electric motor 14 are connected to a drive train 18 (shown) via a transmission 16. The drive shafts of the internal combustion engine 12 and the electric motor 14 are decoupled from the transmission 16 via a clutch 20, which can be opened by the driver actuating a clutch pedal (not shown) and is closed when not actuated. Alternatively, the transmission 16 can be designed as an automatic transmission, in which the actuation of the clutch 20 is omitted. In particular, the transmission 16 can be designed as a dual-clutch transmission, in which the control and actuation of the two clutches takes place automatically.

[0025] The electric motor 14, which is, for example, a three-phase asynchronous or synchronous motor, can be operated either in motor mode with a positive electromotive torque M_EM or in generator mode with a negative electromotive torque M_EM. In motor mode, the electric motor 14 drives the drive train 18—alone or in support of the combustion engine torque M_VM of the combustion engine 12—using electrical energy (current). The electric motor 14 draws this energy from an energy storage device 22, which can be, for example, a battery and / or preferably a capacitor storage device. In generator mode, however, the electric motor 14 is driven by the combustion engine 12 or the vehicle's overrun mode and converts the kinetic energy into electrical energy to replenish the energy storage device 22.The switching of the electric motor 14 between motor and generator operation is carried out by a power electronics 24, which simultaneously carries out any necessary conversion between direct current and alternating current.

[0026] According to the concept presented, the vehicle is predominantly driven by the combustion engine 12, which is started by the electric motor 14 designed as a starter generator. The electric motor 14 also performs a boost function by being switched on to support the vehicle drive in high-load situations, particularly during vehicle acceleration (motor operation). On the other hand, in driving situations in which there is an excess of kinetic energy in the vehicle, the electric motor 14 has a so-called recuperation function by converting the kinetic energy into kinetic energy in generator mode to charge the energy storage device 22 and thus simultaneously provide a braking torque. An electric motor 14 that is particularly suitable in this context has an output of no more than 50 kW, in particular no more than 30 kW, preferably in the range of 15 to 25 kW, specifically approximately 20 kW.

[0027] In Fig.1 also shows an optional additional clutch 26, which can be arranged between the internal combustion engine 12 and the electric motor 14. Such an additional clutch 26 allows the separate decoupling of the internal combustion engine 12 from the drive train 18 or from the electric motor 14, which fundamentally offers the advantage that when the internal combustion engine 12 is switched off, its mechanical frictional resistance does not have to be carried along. Although the additional clutch 26 therefore provides additional fuel savings potential, it is associated with additional costs, design effort, and installation space requirements. The method described here can be applied equally to hybrid drives with and without an additional clutch 26.

[0028] The operation of the combustion engine 12 and the power electronics 24 is controlled here by an engine control unit 28, into which a torque control (indicated by 30) is integrated in the form of a program algorithm. Alternatively, the torque control 30 can also be provided in a separate control unit. Various current operating parameters of the vehicle are input to the engine control unit 28. In particular, a crankshaft speed n and a pedal value PW from a pedal value sensor indicated by 32 are sent to the control unit 28. The pedal value PW indicates the position of an accelerator pedal, i.e., the degree to which the driver operates the accelerator pedal. Furthermore, the engine control unit 28 receives or determines information that characterizes a state of charge (SOC) and an aging state (SOH, state of health) of the energy storage device 22.

[0029] Depending on the pedal value PW and the speed n, the torque control 30 determines a current desired torque M_W from stored characteristic maps and controls both the internal combustion engine torque M_VM of the internal combustion engine 12 and the electromotive torque M_EM of the electric motor 14 accordingly. The present invention is particularly useful in phases in which the requested desired torque M_W exceeds a currently available total drive torque M_Fzg of the hybrid drive unit 10, i.e., during load requirements, such as acceleration situations. Depending on the determined desired torque M_W, a case differentiation is made, which leads to different strategies, which are implemented in the Fig. 2 to 4 are shown using the progression of the different moments.

[0030] In Fig.2 shows a situation in which, at time t0, the pedal value sensor 32 indicates a pedal value PW of 100%, i.e., the accelerator pedal is fully depressed (“full throttle”). Depending on the pedal value and a current engine speed n (not shown), the engine control unit 28 determines a maximum desired torque (M_W = M_Wmax), which is always greater than a maximum permissible combustion engine torque M_VMmax. In this full-throttle situation, the combustion engine torque M_VM is supported by a maximum boost from the electric machine 14. For this purpose, in an initial boost phase B, the combustion engine 12 is ramped up at maximum speed to its maximum torque M_VMmax.At the same time, the electric motor 14 is operated dynamically during boost phase B, initially ramping up as quickly as possible and then ramping down again, so that a dynamic, positive, electromotive torque M_EM, passing through a maximum, is imposed on the combustion engine torque M_VM. As a result, the total drive torque M_Fzg of the hybrid drive 10 increases as rapidly as possible and essentially linearly, reaching the requested desired torque M_W already during boost phase B.

[0031] The boost phase B ends when the internal combustion engine 12 has reached its maximum torque M_VMmax (time t1). Then, a switch is made to a subsequent support phase S, while the internal combustion engine 12 continues to operate at its maximum torque M_VMmax and is supported by a likewise at least approximately constant positive torque M_EM of the electric machine 14. The magnitude of the supporting electromotive torque M_EM is primarily selected such that the resulting total drive torque M_Fzg essentially corresponds to the desired torque M_W. In addition, the torque V_EM and the duration of the quasi-static support phase S are specified as a function of the speed n and the current charge and aging state SOC, SOH of the energy storage device 22.If, for example, the storage level is low or the storage capacity is already impaired due to significant aging, the duration of the support phase tends to be shorter. If the available electrical energy from the storage device 22 is very low, a lower torque M_EM can also be controlled – accepting that the desired torque M_W cannot be fully realized.

[0032] After the specified duration of the support phase S has elapsed at time t2, the electromotive torque M_EM is reduced during a first reduction phase D1 with a defined torque change until a torque at least almost zero is reached. This is achieved by reducing and ultimately switching off the excitation by means of the power converter. During the subsequent neutral phase N, the zero torque of the electric machine 14 is maintained and the combustion engine 12 is thus passively supported. In this phase N, the combustion engine 12 is neither supported nor loaded by the electric machine 12. It should be noted that with permanently excited synchronous machines, zero torque cannot usually be set; instead, a slight drag torque is generated, which is subsumed here under the term zero torque.The neutral phase N is preferably only performed in the case of maximum load demand, for example during short accelerations at already high vehicle speeds. Accordingly, a high desired torque M_W is provided as a criterion for performing the neutral phase N, which is in particular greater than the maximum combustion engine torque M_VMmax, preferably close to or equal to the maximum desired torque M_Wmax. At the same time, a pedal value PW of at least 90%, in particular at least 95%, preferably a maximum pedal value of approximately 100% must be present. The duration of the neutral phase N can also be specified depending on the SOC and / or SOH of the energy storage device 22.

[0033] At the end of the neutral phase N, at time t4, in a further reduction phase D2, the torque M_EM is reduced to a negative value with a defined torque change, i.e., the electric machine 14 is operated as a generator. During the subsequent charging phase L, the generator torque M_EM is selected such that an on-board power supply requirement is just met, i.e., the energy storage device 22 is not charged due to a lack of excess energy. In this way, on the one hand, the on-board electrical supply is ensured and, on the other hand, the braking torque thus generated is minimized. Depending on the state of charge SOC of the energy storage device 22 and / or a conventional on-board power supply battery, as well as the prevailing energy management requirements, the negative electromotive torque M_EM can be reduced even further in the further course of the process in order to charge the energy storage device 22 and / or the battery.

[0034] Also in the Fig. In the situation shown in Figure 3, a desired torque M_W exists that exceeds the maximum combustion engine torque M_VMmax, in particular, a maximum desired torque M_Wmax exists. Unlike in Fig. 2, however, the pedal value PW is less than 100% and amounts to 80% of the maximum pedal value. In this case, the boost phase B and the subsequent support phase S are carried out as shown in Fig. 2. In contrast to the previously described case, however, no neutral phase N with passive support is carried out here, since the pedal value is below the above-mentioned threshold of 90%, in particular 95%, preferably 100%. Rather, following the support phase S, in a reduction phase D, the torque M_EM of the electric machine 14 is reduced with a defined gradient down to a negative (generator) torque. In the charging phase L, analogous to Fig.2 - the electromotive torque M_EM is determined according to the current on-board power supply demand requested by the energy management system. Here, too, the electromotive torque M_EM can subsequently be further reduced to ensure charging of the energy storage device 22.

[0035] In the driving situation according to Fig.4, a partial load situation exists, i.e., the desired torque M_W requested at t0 is below the maximum combustion engine torque M_VM and the pedal value PW is relatively low (e.g., 20%). In order to nevertheless provide the desired torque in the shortest possible time, the relatively inert torque M_VM of the combustion engine 12 is again supported in the initial boost phase B by a dynamic, maximum-passing electromotive torque M_EM. In contrast to the situations described above, however, a lower boost torque of the electric machine 14 is sufficient in this case. The boost phase B lasts at least until the requested torque M_W is reached. Since, in the present partial load situation, the entire desired torque M_W can be provided by the combustion engine 12, no further electromotive support is necessary following the boost phase B.Therefore, at time t1, the torque M_EM is reduced to a negative value at a defined rate (generator operation). The torque M_EM controlled in the subsequent charging phase L can be selected, depending on the SOC and / or SOH of the energy storage device 22, either to cover the current on-board network demand (according to . Fig. 2 and Fig.3) or to charge the energy storage device 22. In order to compensate for the braking torque thus achieved, the combustion engine torque M_VM is increased accordingly during the charging phase L. Following the charging phase L, the electromotive torque M_EM is increased to zero torque and the combustion engine torque M_VM is correspondingly reduced in a boost phase H. However, if the energy storage device 22 is fully charged at time t1 or if the charge state exceeds a predeterminable threshold and there is no or only a low on-board network demand, the charging phase L can be dispensed with entirely and the system can switch directly from the boost phase B to the neutral phase N, in which the electric machine 14 is switched off.

[0036] The three strategies described above can be summarized in the following table. Boost phase (B) Second phase (S, L) Neutral phase (N) Full load boost M_W > M_VMmax PW = 90...100 % yes maximum boost Support phase (S), motor operation of the electric motor Yes High load boost M_W > M_VMmax PW < 90% yes maximum boost Support phase (S), motor operation of the electric motor no Partial load boost M_W < M_VMmax yes low boost Charging phase (L), generator operation of the electric motor or neutral phase (N) electric motor "off" Yes List of reference symbols 10 Hybrid drive unit 12 combustion engine 14 Electric motor 16 gearboxes 18 Powertrain 20 Clutch or dual clutch unit 22 Energy storage / battery 24 Power electronics 26 additional clutch 28 Engine control unit 30 torque control 32 pedal value sensors n speed PW pedal value M_EM electromotive moment M_VM combustion engine torque M_VMmax maximum combustion engine torque M_Fzg total drive torque M_W Desired moment M_Wmax maximum desired torque B Boost phase S support phase N neutral phase L Charging phase D Shutdown phase H boost phase

Claims

[1] Method for torque control of a motor vehicle with a hybrid drive unit (10) which comprises an internal combustion engine (12) and at least one electric machine (14) which can be operated either as a motor or as a generator, wherein the electric machine (14) supplies a positive or negative electromotive torque (M_EM) which, together with an internal combustion engine torque (M_VM), represents a total drive torque (M_Fzg) of the drive unit (10), and wherein, in the presence of a desired torque (M_W) which is greater than a currently provided total drive torque (M_Fzg) of the drive unit (10), (a) in an initial boost phase (B), a dynamic, positive, electromotive torque (M_EM) is imposed on the combustion engine torque (M_VM), which reaches a maximum during the boost phase (B), and (b) in a second phase (S, L), a predeterminable, constant, positive electromotive torque (M_EM) is impressed on the combustion engine torque (M_VM) for a predeterminable duration, which lies below the maximum of the electromotive torque (M_EM) in the boost phase (B), so that the resulting total drive torque (M_Fzg) corresponds to the desired torque (M_W), wherein the magnitude of the electromotive torque (M_EM) is specified as a function of the desired torque (M_W) characterized by that, if the desired torque (M_W) is greater than the maximum combustion engine torque (M_VMmax) and at the same time a pedal value (PW) of a pedal value sensor is 90 to 100%, a neutral phase (N) is carried out after the second phase, in which the electric machine (14) is operated with a zero torque and at the end of the neutral phase (N) the electromotive torque (M_EM) is reduced to a negative value. [2] Method according to claim 1, characterized by that, if the desired torque (M_W) is greater than a maximum internal combustion engine torque (M_VMmax) of the internal combustion engine (12), the second phase is carried out as a support phase (S), in which the electric machine (14) is operated with a positive electromotive torque (M_EM). [3] Method according to one of the preceding claims, characterized by that the duration of the second phase (S, L) and / or the level of the electromotive torque (M_EM) during the second phase (S, L) is predetermined as a function of a state of charge (SOC) and / or an ageing state (SOH) of an electrical energy store (22) of the electrical machine (14). [4] Method according to one of the preceding claims, characterized bythat the duration of the second phase (S, L) and / or the level of the electromotive torque (M_EM) during the second phase (B) is predetermined as a function of a current rotational speed of a common crankshaft of the hybrid drive unit (10). [5] Method according to one of the preceding claims, characterized by that, if the desired torque (M_W) is greater than a maximum combustion engine torque (M_VMmax) of the combustion engine (12), the boost phase (B) is carried out until the maximum combustion engine torque (M_VMmax) is reached. [6] Method according to one of the preceding claims, characterized by that during the boost phase (B) the combustion engine torque (M_VM) and the electromotive torque (M_EM) are controlled in such a way that a maximum increase in the total drive torque (M_Fzg) results. [7] Torque control (30) of a motor vehicle with a hybrid drive unit (10), which comprises an internal combustion engine (12), and at least one electric machine (14), which can be operated optionally as a motor or generator, wherein the electric machine (14) supplies a positive or negative electromotive torque (M_EM), which together with an internal combustion engine torque (M_VM) represents a total drive torque (M_Fzg) of the drive unit (10), wherein the torque control (30) in the presence of a desired torque (M_W) which is greater than a currently provided total drive torque (M_Fzg) of the drive unit (10), (a) in an initial boost phase (B) imposes a dynamic, positive, electromotive torque (M_EM) on the combustion engine torque (M_VM), which reaches a maximum during the boost phase (B), and (b) in a second phase (S, L) for a predeterminable duration, a constant, positive electromotive torque (M_EM) is imposed on the combustion engine torque (M_VM), which lies below the maximum of the electromotive torque (M_EM) in the boost phase (B), so that the resulting total drive torque (M_Fzg) corresponds to the desired torque (M_W), wherein the level of the electromotive torque (M_EM) is specified as a function of the desired torque (M_W) characterized by that, if the desired torque (M_W) is greater than the maximum combustion engine torque (M_VMmax), if at the same time a pedal value (PW) of a pedal value sensor is 90 to 100%, a neutral phase (N) is carried out after the second phase, in which the electric machine (14) is operated with a zero torque and at the end of the neutral phase (N) the electromotive torque (M_EM) is reduced to a negative value. [8] Torque control (30) according to claim 7, characterized bythat the combustion engine (12) is supplied with compressed charge air via an exhaust gas turbocharger.

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