Patent ID: 12221933

DETAILED DESCRIPTION OF THE DRAWINGS

As presented in the introduction, the present disclosure is concerned with the operation of a hybrid drive, in particular upon the ending of one or more drag-torque-reducing measures. In this context,FIGS.1a,1b,1cand1dshow block diagrams of exemplary hybrid drives for a vehicle100. A hybrid drive comprises a combustion motor101and an electric machine102, which can be utilized individually or jointly to generate a drive torque for the vehicle100. The combustion motor101and the electric machine102are arranged such that the torques generated by the respective drive motor add together to give an overall drive torque, which is transmitted for example via a transmission104and an output shaft108of the transmission104to one or more wheels109of the vehicle100. The electrical energy for the operation of the electric machine102may be stored in an electrical energy store110.

The vehicle100furthermore comprises a control unit111(for example a motor control unit) which is configured to determine a demanded overall drive torque. The demanded overall drive torque may be specified by a driver of the vehicle for example by way of an accelerator pedal and/or by way of a setting of the transmission104. For example, a driver may actuate the accelerator pedal in order to demand an increased overall drive torque. The control unit111may be configured to divide up the demanded overall drive torque into a first torque (for the combustion motor101) and a second torque (for the electric machine102). In other words, the control unit111may be configured to operate the combustion motor101and the electric machine102in a manner dependent on a demanded overall drive torque.

In the example illustrated inFIG.1a, the vehicle100comprises a dual clutch transmission104which has a first clutch105which is configured to couple the drive shaft107of the combustion motor101to a first input shaft115, to form a first partial transmission125of the transmission104, or to decouple said drive shaft from said first input shaft. Furthermore, the transmission104has a second clutch106which is configured to couple the drive shaft107of the combustion motor101to a second input shaft116, to form a second partial transmission126of the transmission104, or to decouple said drive shaft from said second input shaft.

The first input shaft115and the second input shaft116are typically coaxial with respect to one another. In particular, the first input shaft115may be a solid shaft which is surrounded by the second input shaft116in the form of a hollow shaft. The first input shaft115may be coupled via the first partial transmission125, and a gear ratio set therein, to the output shaft108. Furthermore, the second input shaft115may be coupled via the second partial transmission126, and a gear ratio set therein, to the output shaft108. For example, the odd-numbered gear ratios (for example 1, 3, 5 etc.) may be provided by the first partial transmission125and the even-numbered gear ratios (for example 2, 4, 6 etc.) may be provided by the second partial transmission126. The first and/or second partial transmissions125,126typically have one or more shift elements103by way of which the various gear ratios of the respective partial transmission125,126can be engaged in automated fashion and/or by way of which the respective partial transmission125,126can be placed into a neutral position (without any gear ratio engaged). In a neutral position, it is typically the case that the input shaft115,116of a partial transmission125,126is decoupled from the output shaft108.

The electric machine102of the hybrid drive may, in an efficient manner in terms of structural space, be couplable to one or both of the two partial transmissions125,126, or may be connected to only one of the two partial transmissions125,126. In particular, the electric machine102may be couplable directly to the input shaft115,116of one of the two partial transmissions125,126. Furthermore, the electric machine102may be arranged such that coupling to the input shaft115,116of the respective other partial transmission125,126is possible only by way of the clutches105,106.

FIG.1bshows a vehicle100with a parallel hybrid drive, in which the drive torques of the two motors101,102act additively on the common input shafts of the transmission104. Furthermore,FIG.1bshows a clutch114by way of which the transmission104can be decoupled from the combustion motor101.

FIG.1cshows a vehicle100with an axle hybrid drive, in which the combustion motor101and the electric machine102drive different axles of the vehicle100. In other words, the drive torques of the two motors101,102act on different axles of the vehicle100.

FIG.1dshows a vehicle100with a parallel hybrid drive with a P1architecture, in which the electric machine102acts directly on the crankshaft107without the presence of a separating clutch situated between electric machine102and combustion motor101.

The combustion motor101of a hybrid drive can be at least intermittently deactivated, for example in the case of (possibly purely) electric operation of the hybrid drive and/or if the one or more wheels109of the vehicle100are driving the output shaft108. The drive shaft107of the deactivated combustion motor101can thus, in unfired cranked operation, be driven and/or concomitantly rotated by the electric machine102and/or by the one or more wheels109of the vehicle100. Unfired cranked operation of the combustion motor101has the advantage that the combustion motor101can be rapidly and efficiently fired again in order to contribute drive torque for the overall drive of the vehicle100. However, the cranking of the combustion motor101by the electric machine102and/or by one or more wheels109of the vehicle100leads to relatively high cranking losses.

To reduce the drag torque of the combustion motor101, one or more drag-torque-reducing measures can be implemented. For example, one or more cylinders of the combustion motor101can be deactivated. Alternatively or in addition, the opening and/or closing angles and/or the valve lift of the inlet and/or outlet valves of the combustion motor101can be adapted in order to reduce the drag torque. For a commencement of fired operation of the combustion motor101, it is however typically necessary that, in preparation for the commencement of fired operation, the one or more drag-torque-reducing measures are ended again.

The unfired cranked operation of the combustion motor101can thus be implemented such that a transition from the unfired cranked operation of the combustion motor101to fired operation of the combustion motor101is possible. The unfired cranked operation however results in a relatively high drag torque of the combustion motor101and thus relatively high losses. Alternatively, an operating mode with one or more drag-torque-reducing measures may be selected. This drag-torque-reduced, unfired, cranked operation of the combustion motor101can have the effect that, upon a transition to combustion operation of the combustion motor101, the drag torque thereof briefly increases, owing to the transition via the unfired cranked operation required for this, before a switch can subsequently be made to fired operation. Furthermore, the departure from the unfired cranked operation can have the effect that, upon the commencement of firing of the combustion motor101, a positive drive torque is immediately generated, which can be perceived as uncomfortable by the driver of a vehicle100and should therefore be compensated by the electric machine102. For the compensation of the briefly increased drag torque, an additional torque reserve can be kept in reserve by the electric machine102.

For the departure from drag-torque-optimized overrun cut-off of the combustion motor101, the opening and/or closing angles and/or the valve lift of the inlet and/or outlet valves of the combustion motor101can be controlled such that the minimal fired base torque of the combustion motor101does not exceed the generator torque that can be provided by the electric machine101with regard to the demanded crankshaft torque at the combustion motor101. During the fading-in of the fired operation of the combustion motor101, the electric machine102can compensate the base torque such that the resulting drive torque of the hybrid drive continues to correspond to the driver demand. After reactivation of the combustion motor101, the overall drive torque can again be distributed between the electric machine102and the combustion motor101in a standard manner.

FIG.2shows an exemplary course211of the torque200of a combustion motor101. Here, the combustion motor101has, in unfired operation, a full drag torque201or, in the event of activation of one or more drag-torque-reducing measures, a reduced drag torque202. Drag-reduced, unfired operation may be departed at a time221. The one or more drag-torque-reducing measures may be ended then, which leads to an increase of the drag torque to the full drag torque201. Synchronously with the ending of the one or more drag-torque-reducing measures, the electric machine102may be caused to generate a positive torque200(see course212), such that the increase of the drag torque of the combustion motor101is at least partially or preferably entirely compensated. The result is then the overall torque according to the torque course213, which acts on the one or more wheels109.

It is pointed out thatFIG.2illustrates only the additional torque that is imparted by the electric machine102for the purposes of compensation upon the ending of the drag-torque-reduced, unfired operation of the combustion motor101. Over and above this, the electric machine102may impart a drive torque which can be superposed on the course with respect to course212illustrated inFIG.2.

At the time223, the fired operation of the combustion motor101may be started (after ending of the one or more drag-torque-reducing measures), whereby a positive base torque204is typically generated by the combustion motor101. The fired operation of the combustion motor101thus typically leads to a positive minimum or base torque204. The electric machine102can be utilized to at least partially and preferably entirely compensate this positive base torque204, by virtue of the electric machine102being operated as a generator (see course212between time223and time224).

At the time225, a (possibly additional) positive drive torque may be demanded by a user of the hybrid drive, in particular by a driver of the vehicle100(for example by actuation of the accelerator pedal). The negative compensation torque effected by the electric machine102can then be reduced (for example to zero), as illustrated by way of example inFIG.2. Furthermore, the overall drive torque may be divided up between the electric machine102and/or the combustion motor101.

The commencement of fired operation of the combustion motor101may be performed such that the positive base torque204is as far as possible only so low that the base torque204can be compensated by the electric machine102by way of a generator torque, and the electrical power generated in the process can be accommodated by the electrical energy store110. In particular, the ignition of the combustion motor may take place relatively late (be “retarded”) in order to reduce the base torque204generated by the combustion motor101. As a consequence, the reserve214for the electric machine102, which must be kept in reserve in order to allow a uniform transition from the drag-torque-reduced, unfired operation to the fired operation of the combustion motor101, can also be reduced. Here, firing of all cylinders or only of a certain subset of the cylinders may commence, whereby different base torque courses can be generated.

FIG.3shows a flow diagram of an exemplary method300for the operation of a hybrid drive, in particular upon departure from a drag-torque-optimized overrun cut-off or upon departure from drag-torque-reduced, unfired operation of the combustion motor101. The method300may be carried out by a control unit111of a hybrid drive or of a vehicle100.

The method300comprises the ending301of one or more drag-torque-reducing measures of the combustion motor101in preparation for a commencement of fired operation of the combustion motor101. Here, the one or more drag-torque-reducing measures may be such that the one or more drag-torque-reducing measures must be ended before the combustion motor101can be fired again, that is to say before fuel can be injected into the combustion motor101again in order to cause at least a base torque204.

Furthermore, the method300comprises the operation302of the electric machine102in order to at least partially or possibly entirely compensate the increase of the drag torque of the combustion motor101caused as a result of the ending of the one or more drag-torque-reducing measures.

By way of the aspects described in this disclosure, the required torque reserve214in the electric machine102for the departure from unfired operation of the combustion motor101can be reduced. The reduced torque reserve214in the electric machine102makes it possible to maintain the unfired operation of the combustion motor101with a relatively low drag torque for a longer period of time because, owing to the reduced torque reserve214, the electric machine102can provide more power for the driving task and, furthermore, during recuperation operation, charges more energy into the electrical store110. Alternatively or in addition, it may be effected that the combustion motor102, after the departure from overrun cut-off, starts with a higher base torque204and thus exhibits improved efficiency, which reduces the overall consumption of the hybrid drive.

The present invention is not restricted to the exemplary embodiments shown. In particular, it is to be noted that the description and the figures are intended merely to illustrate the principle of the proposed methods, devices and systems.