Operating procedures for a powertrain, powertrain and vehicle

Abstract

Method for operating a drive train (22) with at least one first and one second drive motor, with a transmission arrangement and a drive control unit, optionally in a purely stepped operating mode or a continuously variable operating mode of the transmission arrangement, wherein a first target speed (10) of the at least one first drive motor is provided in the drive control unit in the purely stepped operating mode of the transmission arrangement and a second target speed (12) of the at least one second drive motor is provided in the drive control unit in a continuously variable operating mode of the transmission arrangement, characterized in that the at least one first drive motor is an internal combustion engine and the at least one second drive motor is an electric drive motor.wherein a third target speed (14) of the internal combustion engine in a third operating mode of the transmission arrangement is formed from the first target speed (10) and the second target speed (12) of the electric drive motor as a function of a further parameter based on a calculation rule and / or a characteristic map in the drive control unit, and wherein the internal combustion engine is operated at the third target speed (14).

Description

[0001] The invention relates to an operating method for a drive train according to the preamble of claim 1. Furthermore, the invention relates to a drive train according to claim 7 and a vehicle according to claim 8.

[0002] Powertrains typically feature a transmission with a variable gear ratio. The gear ratio is adjusted depending on various parameters, such as the current engine speed or power requirement. Depending on the type of powertrain and transmission, changes in the gear ratio occur either abruptly (stepped) or continuously (continuously). Some powertrain-transmission combinations also allow for both stepped and continuously variable gear ratio changes.

[0003] For example, the document DE 10 2015 206 061 A1 discloses a shift routine for a stepped automatic transmission in a power-split drive train, which regulates the speed of an internal combustion engine to a target speed in order to increase energy efficiency.

[0004] The document DE 10 2014 016 188 A1 also discloses a drive train with a transmission and a control method which enables both continuously variable and stepped operation and, for example, switches between stepped and continuously variable operation depending on the drive power.

[0005] The document DE 103 57 239 A1 discloses an automatic transmission for a motor vehicle with continuously variable transmission ratio, which can be operated in a constant speed mode or in an acceleration mode, wherein the speed can be increased or decreased in stages in the acceleration mode.

[0006] The document DE 11 2015 004 130 T5 discloses a control device for a vehicle drive device, comprising a first electric machine, a second electric machine, a differential gear unit having a first rotating element, a second rotating element and a third rotating element in an order of arrangement in a speed diagram, wherein the first electric machine is coupled to the first rotating element, an internal combustion engine coupled to one of the second rotating element and the third rotating element, wherein the second electric machine and an intermediate input element are coupled to the respective other rotating element, and a switching device.The switching device has a plurality of engagement devices that establish a plurality of switching speeds having different speed ratios selected according to engagement states of the plurality of engagement devices, wherein a speed of the intermediate input member is switched at the speed ratio of the established switching speed and a resulting rotation is transmitted to an output member that is drivingly coupled to wheels.

[0007] US 5 947 861 A1 discloses a continuously variable transmission control system for controlling a gear ratio of a continuously variable transmission of a vehicle based on a gear ratio control map defining an engine speed according to the driving conditions of the vehicle, the continuously variable transmission control system comprising: a driving condition monitor for monitoring a driving condition of the vehicle; a gear ratio control map having a stepwise control range of driving conditions in which the engine speed is controlled to alternately increase gradually and decrease rapidly as the vehicle speed increases to thereby change a gear ratio stepwise, and a continuous control range of driving conditions in which the engine speed is controlled to increase approximately linearly with an increase in the vehicle speed.to thereby continuously change a gear ratio; and a control device for judging whether the driving condition monitored by the driving condition monitoring device lies within a specified unstable zone of driving conditions, and for narrowing the stepwise control zone of driving conditions if it is judged that the driving condition lies within the specified unstable zone. The document DE 10 2014 016 188 A1 discloses a vehicle with a hybrid drive comprising an internal combustion engine and at least one electric motor, each of which is connected via input shafts to a continuously variable, power-split automatic transmission, which drives the vehicle wheels via an output shaft, and with an electronic control device which, for vehicle acceleration in response to a driver-side load request in the higher load range, controls the internal combustion engine until a predetermined target speed is reached.and controls the electric machine at a speed, specifically by increasing the speed of the output shaft acting on the vehicle wheels, wherein the control device for controlling the electric machine during vehicle acceleration has a speed tracking unit with which a speed tracking can be carried out, in which the speed gradients at the output shaft and at the internal combustion engine input shaft are compared, and in which, on the basis of this gradient comparison, the electric machine can be controlled such that the two gradients behave synchronously with each other.

[0008] The object of the present invention is to increase driving comfort during the switching process between a stepped and a continuously variable operation of a drive train.

[0009] This object is achieved according to the invention by a method having the features of claim 1, as well as by a drive train according to claim 7 and a vehicle according to claim 8. Advantageous developments of the invention are characterized in the dependent claims. The features listed individually in the patent claims can be combined with one another in a technologically expedient manner and can be supplemented by explanatory facts from the description and / or details from the figures, whereby further embodiments of the invention are demonstrated.

[0010] The method according to the invention serves to operate a drive train with at least a first and a second drive motor, with a transmission arrangement, and a drive control unit. In this context, the drive control unit can advantageously be configured to control components located outside the drive train in addition to controlling the drive train. Furthermore, the properties and functions attributed to the drive train control unit within the scope of this description can also be distributed among several hardware-distributed control units, which together form the drive control unit. The transmission arrangement can optionally be operated at least in a purely stepped operating mode or a continuously variable operating mode.In the drive control unit, a first target speed of the at least one first drive motor for a purely stepped operating mode of the transmission arrangement is provided in the drive control unit, and a second target speed of the at least one second drive motor for a continuously variable operating mode of the transmission arrangement is provided in the drive control unit. Furthermore, a third target speed of the at least one first drive motor in a third operating mode of the transmission arrangement is formed in the drive control unit as a function of the first target speed and the second target speed, and the at least one first drive motor is then operated at the third target speed. The resulting continuous switching process can produce particularly comfortable driving behavior in a transmission arrangement that can be switched in both stepped and continuously variable mode.

[0011] The at least one first drive machine is an internal combustion engine and the at least one second drive machine is an electric drive machine, wherein a third target speed of the internal combustion engine is formed in a third operating mode of the transmission arrangement from the first target speed and the second target speed of the electric drive machine as a function of a further parameter using a calculation rule and / or a characteristic map in the drive control unit, and wherein the internal combustion engine is operated at the third target speed.

[0012] A drive train can advantageously be understood as an assembly suitable for driving a machine or a vehicle, in particular a land vehicle, preferably a non-rail-bound land vehicle, for example by providing a rotational or translational movement. A rotational movement provided by the drive train can also be referred to as the output speed. Particularly preferably within the meaning of the present invention, a drive train can be used to drive an electrified vehicle, in particular a hybrid or electric vehicle. A hybrid vehicle can be designed as a plug-in hybrid vehicle. Plug-in hybrid vehicles advantageously enable purely electrical operation over longer distances and offer a high degree of freedom in drive train control.

[0013] The drive train can comprise one or more drive machines, for example internal combustion engines, in particular reciprocating piston engines, and / or one or more electric machines, for example asynchronous machines and / or synchronous machines. The drive train preferably comprises an internal combustion engine and at least one, preferably two electric machines. A drive train preferably also comprises a transmission arrangement. The drive machines can act individually or in combination with the transmission arrangement. It is possible for individual drive machines to act directly on an output of the drive train, or for them to act, for example, to brake the drive train and / or other drive machines and to charge or discharge a traction battery that may be included in the drive train.If drive motors act directly on the output of a drive train, this leads to improved efficiency of the overall system, as inefficient energy conversion processes can be avoided.

[0014] The term "gearbox arrangement" can be understood here as an assembly comprising several, in particular different, sub-gears. The gearbox arrangement sometimes makes it possible to set the speeds of different drive motors relative to one another and / or their speeds relative to one or more outputs of the gearbox arrangement in a fixed and / or variable manner. This also applies to the individual sub-gears themselves. Speed ​​ratios, if they are variable, can be changed in stages and / or continuously, depending on the type and control of the gearbox arrangement. A stepped gearshift is characterized in particular by the fact that only defined gear ratios can be permanently implemented, whereby changes in the gear ratio can typically be implemented relatively quickly.In contrast, a continuously variable transmission is distinguished by the fact that, within the maximum adjustment range of a transmission, theoretically all gear ratios can be applied permanently.

[0015] An example of a stepped transmission is a conventional manual transmission designed as a shiftable spur gear, which can be shifted automatically using a hydraulic actuator and / or by an operator using a shift lever. Stepped shifting behavior can also be achieved using a combination of different planetary gear sets, often used in conventional automatic transmissions, which enable different gear ratios when different degrees of freedom of the transmission are blocked, for example, using clutches.

[0016] A continuously variable transmission can be implemented, for example, as a mechanically continuously variable transmission, such as a push-link belt or a belt transmission, with variable friction radii. A continuously variable transmission can preferably also be implemented as a so-called electric continuously variable transmission, also known as an eCVT. An electric continuously variable transmission within the meaning of the present invention can comprise at least one electric machine that interacts with at least one internal combustion engine by means of a power-split transmission and / or a superposition transmission. This arrangement advantageously makes it possible to combine the properties of electric machines, such as four-quadrant operation, with the increased efficiency of an internal combustion engine resulting from gear ratio optimization.

[0017] A conventional torque converter, as is often used in automatic transmissions, especially in the vehicle segment, does in theory also represent a type of continuously variable transmission, but it is not considered as such in the sense of the invention, since the above-mentioned property of being able to be operated permanently with any gear ratio cannot be achieved or can only be achieved with very high technical effort.

[0018] In a preferred embodiment of the method according to the invention, a stepped manual transmission with a continuously variable transmission, in particular, for example, one comprising at least one planetary gear set, is combined with an electrically continuously variable transmission to form a transmission arrangement. This allows the advantages of manual transmissions, such as a wide speed range, to be combined with the advantages of continuously variable transmissions, such as very free and comfortable speed control.

[0019] The speeds of the drive motors, if more than one is provided, as well as the gear ratios of the various sub-transmissions and the output speed of the drive train are linked to one another via mathematical relationships. For this reason, the target speed according to the invention can advantageously relate to the target speed, in other words the desired speed, of an internal combustion engine in the drive train. This is advantageous because the speed of the internal combustion engine has a particularly strong influence on the efficiency of the drive train and its effect on the vehicle occupants. Furthermore, if the output speed of the drive train is assumed to be given, the gear ratios of the switchable sub-transmissions can be determined from it. The speed can be specified, for example, as revolutions per unit of time or as a qualitative value ("high", "medium", "low" or similar).

[0020] The first target speed for stepped operation of the transmission arrangement can in this case be freely determined within an adjustment range. In a drive train with a partially or fully continuously variable transmission arrangement, a target speed for stepped operation can be emulated with a continuously variable transmission. In other words, this results in virtual gears. This has the advantage that the target speed of a drive motor can be set completely freely. In a preferred embodiment of the method according to the invention, the first target speed is determined based on physical gear ratios of a manual transmission. In a transmission arrangement that can be operated both in a stepped and continuously variable manner, this has the advantage that in the case of a stepped change, only the stepped shifting component needs to be adjusted, whereby the shift can be carried out particularly efficiently and quickly.

[0021] In a further embodiment of the invention, it is also provided that the second target speed for continuously variable operation of the transmission arrangement is determined or set based on the gear ratio of an electric continuously variable transmission. Analogous to the determination of the first speed, this has the advantage in a transmission arrangement that can be operated both stepped and continuously variable that, when changing the gear ratio, only the continuously variable portion needs to be adjusted, allowing a gear ratio change to be carried out particularly efficiently and conveniently.

[0022] In a preferred embodiment, the third target speed is formed, in addition to the first and second target speeds, as a function of an accelerator pedal position and / or a speed of the at least one drive motor and / or a vehicle speed and / or a selector lever position and / or a state of the air conditioning system and / or an operating mode selection. In this case, the state of the air conditioning system can be understood to mean, for example, heating and / or cooling operation. Furthermore, it can be understood to mean a target temperature for the vehicle interior desired by the vehicle driver. The use of the air conditioning system does not have to be limited to the passenger compartment, but in some embodiments can also be used to cool drive components, such as a traction battery. The at least one first drive motor is an internal combustion engine.Determining the target speed based on the speed of an internal combustion engine has the advantage that this speed has a particular influence on the efficiency and acoustic effect of the drivetrain. Setting the target speed based on a vehicle speed advantageously simplifies the consideration of driving resistance and driving noise in a drivetrain control system optimized for efficiency and comfort. In some embodiments of the drivetrain according to the invention, particularly when used in a motor vehicle, a high power output of the drive motors can be advantageously achieved in a stepped-shifting operation, and high comfort with low power output can be advantageously achieved in a continuously shifting operation of the transmission arrangement.Since the accelerator pedal position is a good indicator of the power demand on a drivetrain, especially when used as a vehicle drive, it is particularly advantageous for determining a third target speed from the first and second target speeds. Within the meaning of the invention, the term "accelerator pedal" can also be understood as an analogue actuating or operating device, such as a lever or slider, but also as a virtual accelerator pedal, for example, when applying an automatic control of a method according to the invention by, for example, a robot or software. This depends on where exactly the method according to the invention is used.

[0023] In one group of preferred embodiments, the third target speed is determined by interpolating between the first and second speeds using a characteristic map. By using a characteristic map, a third target speed, and thus a drivetrain behavior, can be generated for a specific combination of input parameters, such as those mentioned above, in a particularly resource-efficient and / or reproducible manner. In particularly simple embodiments, this can be a characteristic map with only one input parameter—in other words, a characteristic curve.

[0024] The method is particularly advantageous when switching between continuously variable and stepped operation of a transmission arrangement, for example, during acceleration. In this case, the method can comprise the following steps in the following order: a. Operating the drive machine in a continuously variable mode, b. Determining that at least one input parameter of the drive control unit exceeds a predetermined first value, c. Operating the first drive machine at the third target speed as an interpolation between the first and second target speeds based on a characteristic map, until at least one input parameter of the drive control unit falls below the first value or exceeds a predetermined second value, d. If the first value is exceeded, operate the drive machine in a continuously variable operating mode; otherwise, operate the drive machine in a stepped operating mode.

[0025] The at least one input parameter in the aforementioned embodiment can be, for example, an accelerator pedal position or an acceleration request, and the drive engine can be, for example, an internal combustion engine in a vehicle.

[0026] According to the invention, a vehicle with a drive train, comprising a drive control unit, is further provided for carrying out the method according to the invention.

[0027] Further advantages and advantageous embodiments and developments of the invention are presented in the following description with reference to the figures. In detail: Fig. 1 the curves of the first, second and third target speeds as a speed curve of an internal combustion engine over the speed when applying the method in a motor vehicle, Fig. 2 a speed curve during a transition from a continuously variable to a stepped operation depending on an accelerator pedal position, Fig. 3 an exemplary sequence of a method for the transition from a continuously variable to a stepped operation depending on the accelerator pedal position, Fig. 4 a vehicle with a drive train comprising a switchable and a continuously variable transmission stage.

[0028] With reference to the figures, embodiments of the method according to the invention and its exemplary application in a vehicle are shown.

[0029] Fig. Figure 1 shows, for a possible embodiment of the invention, the curves of a first stepped 10, a second continuously variable 12, and a third target speed 14 over a vehicle speed. This is a vehicle 20 with a drive train configuration 22 as shown in Fig. 2. A manual transmission 24 is combined with an electric continuously variable transmission 26 in a transmission arrangement. The drive train also includes an internal combustion engine and an electric motor.

[0030] The target speed curve for the stepped transmission 10 is formed such that the gear ratio jumps in the speed curve of the internal combustion engine correspond to the gear ratio jumps of the stepped transmission. The target speed of the continuously variable transmission 12, in contrast, is formed assuming a high gear ratio of the stepped transmission with continuous gear ratio change by means of the electric continuously variable transmission. Thus, in this exemplary embodiment, a first and a second target speed exist for each speed.

[0031] Preferably depending on a further parameter, such as the accelerator pedal position, the third target speed 14 intended for operating the internal combustion engine can then be formed from these target speeds using a calculation rule and / or a characteristic map.

[0032] An example of the transition from a continuously variable to a stepped operation of the transmission arrangement is shown Fig. 3 and Fig. 4. Fig. 3 shows the speed curve of an internal combustion engine n VM depending on the accelerator pedal position at a fixed speed. Below the first threshold value 16, the drive train is in a low load demand state, with the transmission arrangement operating continuously. This initial situation, i.e., the operation of the internal combustion engine at the third speed, where this speed corresponds to the second speed, corresponds to the Fig.4. In the next method step S2, it is determined that the accelerator pedal position exceeds the first threshold value 16. As the accelerator pedal position increases, the speed of the internal combustion engine is then slowly transferred to the purely stepped operation 10, which is suitable for higher power requirements, in the next method step S3 by regulating the speed to the third target speed 14. In the last method step S4, when the second accelerator pedal threshold 18 is exceeded, the third target speed corresponds entirely to that determined for the stepped operation 10. The third target speed 14 is not shaped linearly to the accelerator pedal position. This can be provided, for example, to improve drivability by allowing the speed shaping, and thus the transition from continuously variable to stepped operation, to be carried out more quickly yet comfortably in speed ranges in which this is less noticeable for vehicle occupants.In this exemplary embodiment, the corresponding interpolation rule for forming the third target speed is stored in a characteristic curve depending on the accelerator pedal position. List of reference symbols 10 First target speed 12 Second target speed 14 Third target speed 16 First threshold 18 Second threshold 20 vehicles 22 Drivetrain 24 manual transmissions 26 Continuously variable transmission S1 First process step S2 Second process step S3 Third procedural step S4 Fourth procedural step

Claims

[1] Method for operating a drive train (22) with at least a first and a second drive machine, with a transmission arrangement and a drive control unit, optionally in a purely stepped operating mode or a continuously variable operating mode of the transmission arrangement, wherein a first target speed (10) of the at least one first drive machine in the purely stepped operating mode of the transmission arrangement is provided in the drive control unit and a second target speed (12) of the at least one second drive machine in a continuously variable operating mode of the transmission arrangement is provided in the drive control unit, characterized byin that the at least one first drive machine is an internal combustion engine and the at least one second drive machine is an electric drive machine, wherein a third target speed (14) of the internal combustion engine is formed in a third operating mode of the transmission arrangement from the first target speed (10) and the second target speed (12) of the electric drive machine as a function of a further parameter using a calculation rule and / or a characteristic map in the drive control unit, and wherein the internal combustion engine is operated at the third target speed (14). [2] Method according to claim 1, characterized by that the first target speed (10) is determined based on physical gear ratios of a manual transmission (24). [3] Method according to one of claims 1 or 2, characterized by that the second target speed (12) is determined based on the gear ratio of an electric continuously variable transmission (26). [4] Method according to one of the preceding claims, characterized by that the further parameter for determining the third target speed (14) is an accelerator pedal position and / or a speed of the at least one drive engine and / or a vehicle speed and / or a selector lever position and / or a state of the air conditioning system and / or an operating mode selection. [5] Method according to one of the preceding claims, characterized by that the third target speed (14) is determined by an interpolation between the first (10) and the second speed (12). [6] Method according to one of the preceding claims, characterized by the following steps in the following order: a. Operating the transmission arrangement in a continuously variable mode, b. Determining that at least one input parameter of the drive control unit exceeds a predetermined first value (16), c. Operating the internal combustion engine at the third target speed (14) as an interpolation between the first (10) and second target speed (12) based on a characteristic map until the at least one input parameter of the drive control unit falls below the first value (16) or exceeds a predetermined second value (18), d. If the first value (16) has been undercut, operate the gear arrangement in a continuously variable operating mode, otherwise operate the gear arrangement in a stepped operating mode. [7] Drive train (22) with a drive control unit which is designed to carry out the method according to one of the preceding claims. [8] Vehicle (20) having a drive train (22) according to claim 7.

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