Method for carrying out a gear change in a hybrid drive train of a motor vehicle

Abstract

The invention relates to a method for carrying out a gear change in a hybrid drive train (10) of a motor vehicle, wherein the hybrid drive train (10) comprises an internal combustion engine (12), an electric machine (20), a planetary transmission (38), a first sub-transmission (40), a second sub-transmission (42), a blocking clutch (K1), a first clutch (A1), a second clutch (A2) and an output shaft (34). The planetary transmission (38) has a first planetary gear set (44) with a first element (48), a second element (50) and a third element (52), as well as a second planetary gear set (46) with a fourth element (54), a fifth element (56) and a sixth element (58). The second element (50) is connected to the fifth element (56) for conjoint rotation. The third element (52) is connected to the sixth element (58) for conjoint rotation. The blocking clutch (K1) is designed to block the planetary transmission (38).

Description

[0001] Method for performing a gear change in a hybrid powertrain of a motor vehicle

[0002] The invention relates to a method for performing a gear change in a hybrid powertrain of a motor vehicle, in particular a motor car, according to the preamble of claim 1.

[0003] DE 10 2010 053 757 A1 discloses a hybrid drive device which has a connection unit comprising at least a first connection element for connecting a first drive motor, a second connection element for connecting a second drive motor, a third connection element for connecting a first sub-transmission unit, and a fourth connection element for connecting a second sub-transmission unit. A similar hybrid drive device is known from DE 10 2012 001 315 A1. DE 10 2019 203 243 A1 discloses a shifting method for a transmission of a hybrid drive device of a motor vehicle. And DE 10 2020 004 085 A1 discloses methods for torque control and automated gear shifting of a hybrid powertrain of a motor vehicle.

[0004] The object of the present invention is to provide a method for performing a gear change in a hybrid powertrain of a motor vehicle, so that the gear change can be carried out particularly advantageously.

[0005] This problem is solved by a method with the features of claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims. The invention relates to a method for performing a gear change in a hybrid powertrain of a motor vehicle, also referred to simply as a vehicle, whose interior, also referred to as passenger compartment, passenger cell, or cabin, is formed, for example, by a structure of the motor vehicle, in particular a self-supporting body. Preferably, the motor vehicle is a motor car, in particular a passenger car. During a journey of the motor vehicle, persons such as the driver of the motor vehicle may be present in the interior.For example, the method is carried out while the motor vehicle is in motion, preferably driven by the hybrid powertrain, also referred to as a hybrid drive device, and thus propelled forward. In other words, it is preferably provided that the motor vehicle performs a forward movement during the method, in which the motor vehicle is propelled by the hybrid powertrain and thus propelled forward.

[0006] In this method, the hybrid powertrain includes an internal combustion engine, also referred to as a combustion engine or internal combustion power unit. The internal combustion engine preferably has an output shaft through which it can provide a first torque for driving the vehicle. This first torque is also called the first drive torque. The first torque can be varied, allowing it to assume different values, thus enabling different values ​​to be set. For example, the internal combustion engine has a housing element, wherein the output shaft is rotatable about an output shaft axis relative to the housing element. In particular, the output shaft is rotatably mounted on the housing element about the output shaft axis relative to the housing element.In particular, combustion processes take place in the internal combustion engine, especially in the combustion chambers of the internal combustion engine, which drive the engine output shaft and thereby rotate it around the engine output shaft axis relative to the housing element.

[0007] In this process, the hybrid powertrain includes an electric machine, which, for example, has a stator and a rotor. The rotor is rotatable around a machine axis relative to the stator. The electric machine can provide a second torque via its rotor to propel the vehicle. This second torque is also referred to as the second drive torque. The second torque can also be varied, allowing it to assume different values; thus, different values ​​of the second torque can be set. In particular, the rotor can be driven by means of the stator and thereby rotated around a machine axis relative to the stator.

[0008] In this method, the hybrid powertrain comprises a planetary gear set, a first sub-transmission, and a second sub-transmission. For example, the vehicle can be driven by the engine output shaft, and thus by the internal combustion engine, via the planetary gear set and the sub-transmissions. Furthermore, the vehicle can be driven by the rotor, and thus by the electric machine, via the planetary gear set and the sub-transmissions. In this method, the hybrid powertrain also comprises a locking clutch, a first clutch in addition to the locking clutch, and a second clutch in addition to both the first clutch and the locking clutch. Finally, the hybrid powertrain in this method comprises an output shaft.The output shaft can be driven, for example, via the planetary gear set and the sub-gearboxes from the engine output shaft and thus from the internal combustion engine, particularly to power the vehicle. Furthermore, the output shaft can be driven, for example, via the planetary gear set and the sub-gearboxes from the rotor and thus from the electric machine, particularly to power the vehicle.

[0009] For example, in this method, the motor vehicle has at least or exactly two axles arranged consecutively in the longitudinal direction of the vehicle, namely a first axle and a second axle. Each axle has, for example, at least or exactly two wheels. The wheels of the motor vehicle are ground contact elements by which the motor vehicle can be supported or is supported downwards against the ground. If the motor vehicle is driven along the ground while supported downwards in the vertical direction by the ground contact elements, the ground contact elements roll along the ground, in particular directly.For example, in this method, the vehicle is driven along the ground while, in the vehicle's vertical direction, it is supported downwards by the ground contact elements. For example, the vehicle wheels of at least or exactly one of the vehicle axles are driven by the output shaft, the vehicle wheels driven by the output shaft also being referred to as drive wheels. In particular, the drive wheels are the vehicle wheels of the same vehicle axle. In other words, for example, the vehicle wheels of the first vehicle axle are driven by the output shaft.With reference to a first torque transmission path, via which the first torque from the internal combustion engine, i.e. from the engine output shaft, can be transmitted to the drive wheels in order to drive the drive wheels and thus the motor vehicle, the planetary gear set, the first sub-gear set and the second sub-gear set are arranged downstream of the engine output shaft and upstream of the output shaft and upstream of the vehicle wheels, and the output shaft is arranged upstream of the drive wheels and downstream of the planetary gear set and downstream of the sub-gear sets and thus also downstream of the engine output shaft, and therefore downstream of the internal combustion engine.With regard to a second torque transmission path, via which the second torque can be transmitted from the rotor, i.e., from the electric machine, to the drive wheels in order to drive the drive wheels and thus the vehicle, the output shaft is arranged downstream of the planetary gear set, downstream of the sub-gear sets, and downstream of the rotor, thus downstream of the electric machine and upstream of the vehicle wheels. Therefore, the planetary gear set and the sub-gear sets are arranged downstream of the electric machine, thus downstream of the rotor and upstream of the output shaft. At least certain sections of the aforementioned torque transmission paths can be the same, i.e., identical.

[0010] In this method, the planetary gear set comprises a first planetary gear set, which includes a first element, a second element, and a third element. The first, second, and third elements are gear elements of the first planetary gear set. For example, a first gear element is a first sun gear, a second gear element can be a first planet carrier, and a third gear element can be a first ring gear.

[0011] In this method, the planetary gear set comprises a second planetary gear set, which includes a fourth, a fifth, and a sixth element. The fourth, fifth, and sixth elements are planetary gear elements of the second planetary gear set. For example, the first of the planetary gear elements is a second sun gear, the second of the planetary gear elements can be a second planet carrier, and the third of the planetary gear elements can be a second ring gear. The hybrid powertrain includes, for example, a housing, in which the planetary gear set, and thus the planetary gear sets, can be at least partially arranged within the housing.Particularly when the respective gear element of the first planetary gear set is not rotationally fixed to the housing, the respective gear element of the first planetary gear set is rotatable about a first planetary gear set axis of rotation relative to the housing. Particularly when the respective planetary gear element is not rotationally fixed to the housing, the respective planetary gear element is rotatable about a second planetary gear set axis of rotation relative to the housing. Preferably, the planetary gear sets are arranged coaxially to one another, so that the planetary gear set axes of rotation coincide. Thus, it is particularly provided that the first, second, third, fourth, fifth, and sixth elements are all arranged coaxially to one another and coaxially to a main axis of rotation, with the planetary gear set axes of rotation coinciding with the main axis of rotation.

[0012] The second element is, in particular, permanently and rotationally fixed to the fifth element. The third element is, in particular, permanently and rotationally fixed to the sixth element. The locking coupling is designed to lock the planetary gear set, in particular by means of the locking coupling allowing one of the gear elements to be rotationally fixed to one of the planetary gear elements. In other words, the planetary gear set can be locked by means of the locking coupling, in particular by means of the locking coupling allowing one gear element to be rotationally fixed to one planetary gear element.

[0013] The internal combustion engine, in particular the engine output shaft, is coupled or connectable to the first element in such a way, particularly in a torque-transmitting manner and especially in a rotationally fixed manner, that the first torque emanating from the internal combustion engine, i.e., from the engine output shaft, and thus provided or make available, can be introduced into the planetary gear via the first element. For example, the engine output shaft is torque-transmitting, and in particular in a rotationally fixed manner, connectable or coupled to the first element. For example, the engine output shaft is permanently torque-transmitting, and in particular in a rotationally fixed manner, coupled to the first element.The characteristic that the first torque originating from the engine output shaft, i.e., from the internal combustion engine, can be introduced into the planetary gear at the first element means that, with respect to the aforementioned first torque transmission path, the first element is arranged upstream of the second element and upstream of the third element, i.e., that the first element is the first of the gear elements on which the first torque acts.

[0014] The electric machine, i.e., the rotor, is coupled or can be coupled to the third element in such a way, particularly in a torque-transmitting and especially rotationally fixed manner, that the second torque emanating from the electric machine, i.e., from the rotor, and thus provided or makeable, can be introduced into the planetary gear via the third element. This means that, with respect to the second torque transmission path, the third element is arranged upstream of the first element and upstream of the second element; thus, the third element is the first of the gear elements on which the second torque acts.

[0015] The first sub-transmission has a first switchable gear pair, which includes a first gear and a second gear. For example, the first gear is a first spur gear, and the second gear is a second spur gear. Thus, the first gear pair, also referred to as the first gear stage, is a first spur gear pair, also referred to as the first spur gear stage. The first gear and the second gear mesh with each other, in particular directly, such that the first gear and the second gear mesh continuously with each other.This means that the first gear and the second gear are preferably not switchable between a meshing state, in which the first gear and the second gear mesh with each other, and a disengaged state, in which the first gear and the second gear do not mesh with each other. Instead, the first gear and the second gear preferably mesh with each other always, that is, permanently. The first gear is or can be connected to the second gear in a rotationally fixed manner. For example, the first gear is permanently and rotationally fixed to the second gear, or the first gear can be connected to the second gear in a rotationally fixed manner. For example, the second gear is connected or can be connected to the output shaft in a torque-transmitting manner, and in particular in a rotationally fixed manner; thus, it is coupled or can be coupled.It is conceivable that the second gear is permanently connected to the output shaft in a torque-transmitting manner, and in particular permanently fixed against rotation, or that the second gear can be connected to the output shaft in a torque-transmitting manner, and in particular fixed against rotation. The second sub-transmission has a second switchable gear pair comprising a third gear and a fourth gear. The fourth gear meshes, in particular permanently, with the third gear and vice versa. Thus, it is preferably provided that the third gear and the fourth gear are not switchable between a meshing state, in which the third gear and the fourth gear mesh with each other, and a disengaged state, in which the third gear does not mesh with the fourth gear, but preferably the third gear and the fourth gear always mesh with each other, and thus permanently.For example, the third gear is a third spur gear, and the fourth gear is a fourth spur gear, so that the second gear pair is a second spur gear pair, also referred to as the second spur gear stage. The second gear pair is also referred to as the second gear stage.

[0016] The third gear is either fixedly connected to the fourth element or can be connected to it in a rotationally fixed manner. For example, the third gear is permanently fixedly connected to the fourth element, or the third gear can be connected to the fourth element in a rotationally fixed manner.

[0017] For example, the fourth gear is connected or connectable to the output shaft in a torque-transmitting manner, particularly in a rotationally fixed manner. For example, the fourth gear is permanently connected to the output shaft in a torque-transmitting manner, particularly in a rotationally fixed manner, or the fourth gear is connectable to the output shaft in a torque-transmitting manner, particularly in a rotationally fixed manner.

[0018] The first coupling is designed to connect the first gear pair to the output shaft, particularly for torque transmission. In other words, the first gear pair can be connected to the output shaft by means of the first coupling, particularly for torque transmission. The second coupling is designed to connect the second gear pair to the output shaft. In other words, the second gear pair can be connected to the output shaft, particularly for torque transmission, by means of the second coupling.

[0019] The hybrid powertrain has at least or exactly two gears: a first gear and a second gear. Each gear is a selectable gear. This means that each gear can be selected to be engaged (activated) or disengaged (deactivated). Specifically, it is provided that whenever the first gear is engaged and thus activated, the second gear is disengaged and thus deactivated. Furthermore, it is preferably provided that whenever the second gear is engaged and thus activated, the first gear is disengaged and thus deactivated. The output shaft can be driven by the motor output shaft and the rotor via the selected gear.The first gear can be engaged by having the interlocking clutch closed, while the first clutch is closed and the second clutch is open. The second gear can be engaged by having the interlocking clutch open, while the first clutch is closed and the second clutch is closed. This means that the interlocking clutch can be selectively open or closed. This means that the interlocking clutch can be switched between an open state and a closed state. In the open state, the interlocking clutch is open, and in the closed state, the interlocking clutch is closed. The aforementioned transmission element, which can be rotationally fixed to one of the planetary gear elements by means of the interlocking clutch, is also referred to as the first interlocking element.The aforementioned planetary gear element, which can be connected to the first locking element by means of the locking coupling to lock the planetary gear set, is also referred to as the second locking element. In the first closed state of the locking coupling, the locking elements are connected to each other in a rotationally fixed manner, thus preventing relative rotation between them. In the first open state, the locking coupling releases the locking elements for relative rotation about the main axis of rotation, so that in the first open state the locking elements can rotate relative to each other about the main axis of rotation, i.e., about the respective planetary gear set axis of rotation.

[0020] The first clutch is switchable between a second closed state and a second open state. In the second closed state, the first clutch is closed. In the second open state, the first clutch is open. In the second closed state, the first gear pair is coupled to the output shaft, particularly for torque transmission, via the first clutch. In the second open state, the first gear pair is not coupled to the output shaft via the first clutch. Specifically, in the second open state, the first gear pair is decoupled from the output shaft, so that no torque can be transmitted between the output shaft and the first gear pair via the first clutch in this state.

[0021] The second clutch is switchable between a third open state and a third closed state. In the third closed state, the second clutch is closed, and in the third open state, the second clutch is open. In the third closed state, the second gear pair is coupled to the output shaft, particularly for torque transmission, by means of the second clutch. In the third open state, the output shaft is not coupled to the second gear pair via the second clutch. In particular, in the third open state, the output shaft is decoupled from the second gear pair, so that no torque can be transmitted between the output shaft and the second gear pair via the second clutch in this third open state. In particular, in the second closed state, torque can be transmitted between the output shaft and the first gear pair via the first clutch.In particular, in the third locking state, torques can be transmitted between the output shaft and the second gear pair via the second clutch.

[0022] In order to perform a particularly advantageous gear change from first to second gear, whereby during this gear change the initially engaged first gear is disengaged and the initially engaged second gear is engaged, the invention provides that a first step of the process, also referred to as the first process step, is carried out during the gear change from first to second gear. In the first step of the process, the first torque of the internal combustion engine is increased.In other words, it is provided, for example, that in the first step, the internal combustion engine provides the first torque via the engine output shaft as a driving torque, that is, as a torque intended or designed to propel the vehicle and thereby move it forward, i.e., to effect forward movement of the vehicle, which in the first step is increased, for example, from a first value to a second value that is greater than the first value. Preferably, the second value is a value other than zero. Preferably, the first value is a value other than zero. Furthermore, it is provided in the method that in the first step, the electric machine provides the second torque as a braking torque.The braking torque is a torque intended or designed to slow down the motor vehicle and thus opposes or counteracts its forward motion. In other words, during the aforementioned forward motion of the motor vehicle, the third element, for example, rotates around the main axis of rotation, that is, around the first planetary gear set axis of rotation relative to the housing in a first direction of rotation. The braking torque is a braking torque that opposes the rotation of the third element around the main axis of rotation relative to the housing and in the first direction of rotation, and thus slows down the third element with respect to its rotation around the main axis of rotation relative to the housing and in the first direction of rotation. In particular, it is provided that during gear changes, the electric machine, that is, the rotor, is coupled to the third element in a torque-transmitting, and in particular rotationally fixed, manner.Furthermore, it is preferably provided that during the gear change the internal combustion engine, i.e. the engine output shaft, is coupled to the first element in a torque-transmitting, in particular rotationally fixed manner.

[0023] According to the invention, during the gear change, a second step of the process, also referred to as the second process step, is carried out following the first step, so that the second step occurs after the first step. In the second step, the locking clutch is opened and the second clutch is closed. Thus, for example, it is provided that the locking clutch is closed and remains closed during the first step. For example, it is provided that the second clutch is open and remains open during the first step. For example, the first clutch is closed and remains closed during the first step. For example, the first clutch is not opened between the first and second steps.

[0024] Each gear is preferably a fixed gear. This means that each gear has a fixed and therefore non-variable torque and speed ratio, particularly when viewed from the engine output shaft or rotor to the output shaft. The invention is based on the understanding that, in gear changes (also referred to as shifts) between two fixed gears, there is a so-called approaching shift element and a so-called reversing shift element. The approaching shift element is, for example, a clutch, which was initially open and is closed during or to perform the gear change. The reversing shift element is, for example, a clutch, which was initially closed and is opened during the gear change.The shift element should ideally not be opened under load, as opening it under load would cause the vehicle to lose propulsion or driving torque. This loss of propulsion can be perceived as uncomfortable by occupants, such as the driver. This typically results in a smooth shift taking longer, which places a higher load on the shift element (e.g., a friction element or clutch, particularly a multi-plate clutch) than if the shift were performed quickly, albeit potentially less smoothly.Furthermore, a prolonged shift increases the likelihood of a so-called "change-of-mind" shift, as the driver might decide on a different maneuver during the time allotted for the shift, resulting in the shift not being executed or a different shift being performed. Such change-of-mind shifts, also known as COM shifts (COM - Change-of-Mind), should be avoided due to their duration and often inadequate shift quality.

[0025] The hybrid drivetrain according to the invention offers the possibility of modifying the power flow within a transmission comprising the sub-transmissions and the planetary gear set of the hybrid drivetrain by means of a corresponding torque ratio between the combustion engine and the electric motor. This allows the operating shift element to be prepared without load, without affecting the current driver-requested torque, and without having to actuate a shift element. This adjustable torque ratio is influenced or determined, for example, by the fixed gear ratios of the planetary gear sets, also referred to simply as planetary sets. If the gear change is then actually initiated, the operating shift element can be opened immediately without the vehicle losing propulsion. A prediction of the next gear can be made by the driver-requested torque in combination with the current speed gradient of the output shaft.The method according to the invention, compared to conventional solutions, eliminates a torque transition phase, thereby enabling gear changes to be performed in an advantageously short shift time. This is possible because the time required for preparing hydraulics and for torque ramp-up is eliminated.

[0026] In order to make the gear change particularly comfortable, the first step is furthermore carried out according to the invention, in particular if and only if, as a first precondition, a position of the aforementioned accelerator pedal, also referred to as the accelerator pedal position, falls below a first pedal threshold and / or if a rotational speed of the output shaft exceeds a first rotational speed threshold.

[0027] In order to make the gear change particularly comfortable, the second step is furthermore carried out according to the invention, in particular if and only if, as a second prerequisite, the accelerator pedal position falls below a second pedal threshold value that is smaller than the first pedal value.

[0028] To enable particularly smooth gear changes, one embodiment of the invention provides that, in the first step of the process, the first torque of the combustion engine and the braking torque of the electric motor are adjusted such that the sum of the first torque of the combustion engine and the braking torque of the electric motor equals a driver-requested torque. The driver-requested torque is a torque desired and requested by the driver of the motor vehicle, for example, by the driver operating a control element, such as a pedal, in particular an accelerator pedal, and thereby moving it to a specific position. This allows the gear change to be carried out without any loss of propulsion of the motor vehicle.To enable particularly smooth gear changes, a further embodiment of the invention provides that, in the first step, the first torque of the internal combustion engine and the braking torque of the electric motor are adjusted, i.e., brought to or set to such a respective value, that there is no load between the coupling halves of the locking coupling. This means, in particular, that a first coupling half of the locking coupling is connected, in particular permanently, to one of the locking elements in a torque-transmitting manner, and in particular in a rotationally fixed manner, and a second coupling half of the locking coupling is connected, in particular permanently, to the other locking element in a torque-transmitting manner, and in particular in a rotationally fixed manner.Each coupling half can, for example, be a plate carrier, particularly if the interlocking coupling is designed as a friction coupling configured as a multi-plate clutch. The interlocking coupling has, for example, at least one coupling element which is movable between a closed position and an open position, particularly relative to the coupling halves. In the first closed position, the coupling halves of the interlocking coupling are connected to each other in a torque-transmitting manner, particularly in a rotationally fixed manner, thus interlocking the planetary gear set. In the open position, the coupling halves are rotatable relative to each other, particularly about the main axis of rotation, so that interlocking of the planetary gear set does not occur.For example, in the closed position, the coupling halves are connected to each other by means of the coupling element in a torque-transmitting manner, in particular in a rotationally fixed manner, such that the closed position effects the first closed state, or such that the coupling element is in the closed position in the first closed state. In the open position of the coupling element, the first open state of the locking coupling is effected or set, so that in the open position of the coupling element, the coupling halves and thus the locking elements are rotatable relative to each other, and locking of the planetary gear by the locking coupling is prevented. For example, the coupling element is or comprises at least one or more friction plates of the friction coupling, also simply referred to as plates.The characteristic that there is no load between the coupling halves means in particular that no load, and therefore no torque, is transferred from one of the coupling halves to the other coupling half, or that no different torques act on or at the coupling halves, especially while the locking coupling is closed, i.e., while the locking coupling is in the first closed state.

[0029] Another embodiment is characterized in that, in the first step, the first torque of the internal combustion engine and the braking torque of the electric machine are set as a function of a first stationary gear ratio of the first planetary gear set and as a function of a second stationary gear ratio of the second planetary gear set. The stationary gear ratios are stored, for example, in an electronic data storage device, which is used to carry out the process. This allows the previously described torque ratio, which is set or must be set to disengage the locking clutch, to be adjusted advantageously, quickly, and precisely, so that gear changes can be performed particularly smoothly.

[0030] In order to make the gear change particularly comfortable, it has proven especially advantageous if the second step is carried out, in particular and only then, when the speed of the output shaft exceeds a second speed threshold that is greater than the first speed threshold.

[0031] Another embodiment is characterized in that the locking coupling is designed to connect the fourth element to the second element in a rotationally fixed manner, thereby locking the planetary gear unit. In other words, it has proven particularly advantageous if one of the locking elements is the fourth element and the other locking element is the second element. This ensures particularly convenient operation.

[0032] Finally, it has proven particularly advantageous for realizing a particularly beneficial gear change if the first element is the first sun gear, the second element the first planet carrier, the third element the first ring gear, the fourth element the second sun gear, the fifth element the second planet carrier and the sixth element the second ring gear.

[0033] Within the scope of the present disclosure, the feature that two components, such as the second and fifth elements, are rotationally fixed to one another, is understood to mean that the components, being rotationally fixed to one another, are arranged coaxially and, in particular when the components are driven, rotate together or simultaneously about a common axis of rotation, such as the main axis of rotation, at the same angular velocity, especially relative to a reference element, such as the housing. In other words, two elements, which are in particular rotatably mounted, are rotationally fixed to one another if they are arranged coaxially, especially with respect to their axis of rotation and / or with respect to a rotational symmetry axis, and if they are connected to one another in such a way that they always rotate at the same angular velocity.An element is fixed to the housing if it cannot be rotated opposite, that is, relative to the housing.

[0034] In particular, the aforementioned elements of the planetary gear sets are or comprise shafts of the planetary gear set. The sun gears and the ring gears are also referred to as planet gears of the planetary gear set and are, in particular, permanently, rotationally fixed to their respective associated shafts. It is conceivable that the respective planet gear and the respective associated shaft are designed separately from one another and, in particular, permanently, rotationally fixed to each other, or that the respective planet gear and the respective associated shaft are formed as a single unit, that is, made from a single piece and thereby rotationally fixed to each other.Since the second element is permanently connected to the fifth element in a rotationally fixed manner, and the third element is permanently connected to the sixth element in a rotationally fixed manner, the planetary gear is designed as a four-shaft planetary gear because, in particular, four of the shafts of the planetary gear are rotatable relative to each other about the main axis of rotation.

[0035] Within the scope of this disclosure, the term "coupled" means, for example, that when two components are coupled to one another, the components are coupled to one another in a torque-transmitting manner, and in particular in a rotationally fixed manner. Two components coupled to one another, i.e., torque-transmitting components, can be rotationally fixed to one another. Furthermore, two components coupled to one another, i.e., torque-transmitting components, can be torque-transmitting with respect to a torque transmission flow via one or more transmission stages and, in particular, can be rotatable relative to one another.In other words, the characteristic that two components are connected or coupled to each other in a torque-transmitting manner means that the components are coupled or connected in such a way that torques can be transmitted between them. If the components are connected or coupled in a rotationally fixed manner, then they are also connected or coupled in a torque-transmitting manner. Two components connected in a torque-transmitting manner can therefore be connected in a rotationally fixed manner.Furthermore, it is conceivable that two components connected to each other in a torque-transmitting manner are connected to each other in a torque-transmitting manner via at least or exactly one intermediate transmission unit or via several intermediate transmission units, so that torques can be transmitted between the components via the transmission unit or transmission units, while the components are connected to each other in a torque-transmitting manner, whereby the components can be rotatable relative to each other.

[0036] The characteristic that two components are permanently connected or coupled in a torque-transmitting manner means that there is no switching element that can be toggled between a coupling state in which the components are connected or coupled in a torque-transmitting manner and a decoupling state in which no torque can be transmitted between the components via the switching element. Rather, the components are always and therefore permanently torque-transmitting, meaning they are connected or coupled in such a way that torque can be transmitted between them. Thus, for example, one component can be driven by the other, and vice versa.

[0037] In particular, the feature that two components are permanently connected or coupled to each other in a rotationally fixed manner means that a switching element is not provided which can be switched between a coupling state in which the components are rotationally fixed to each other and a decoupling state in which the components are decoupled from each other and rotatable relative to each other, so that no torques can be transmitted between the components via the switching element. Rather, the components are always, i.e., permanently, connected or coupled to each other in a rotationally fixed manner. Furthermore, the feature that two components can be connected or coupled to each other in a rotationally fixed manner means that the components are assigned a switching element which can be switched between at least one coupling state and at least one decoupling state.In the coupled state, the components are rotationally fixed to one another by means of the switching element. In the decoupled state, the components are decoupled from each other, so that in the decoupled state the components can rotate relative to each other about the component axis of rotation and no torque can be transmitted between the components via the switching element. The same applies to the feature that two components can be connected or coupled to one another in a torque-transmitting manner. Thus, the feature that two components can be connected or coupled to one another in a torque-transmitting manner means that a switching element is assigned to the components, wherein the switching element can be switched between at least one connected state and at least one enabled state.In the connected state, the components are coupled or connected to each other via the switching element, thus transmitting torque between them. In the released state, the components are decoupled from each other, so that no torque can be transmitted between them via the switching element.

[0038] The term "locking" the planetary gear system means, in particular, that the locking elements can be connected to each other in a rotationally fixed manner by means of the locking coupling, whereby the locking elements are two elements that are not already permanently connected to each other in a rotationally fixed manner.

[0039] For example, the output shaft is a differential input shaft of a differential gear, from which the drive wheels can be driven. The drive wheels, via the differential gear, are driven by a complete transmission comprising the planetary gear set and the sub-gear sets, which in turn drives the output shaft. With respect to the respective torque transmission path, the complete transmission is thus located downstream of the rotor and downstream of the motor output shaft, and upstream of the drive wheels and upstream of the output shaft. In particular, if the differential gear, also simply referred to as a differential, is a bevel gear differential, the output shaft is, for example, a differential cage of the differential gear, i.e., of the bevel gear differential.

[0040] The term "switchable gear pair" refers in particular to the following: One of the meshing gears of the respective gear pair is designed as a loose gear arranged on a first shaft, while the other meshing gear of the respective gear pair is designed as a fixed gear, which is permanently and rotationally fixed to a second shaft. One of the gears of the respective gear pair is a so-called input gear, and the other gear of the respective gear pair is a so-called output gear. This means that, with respect to the respective torque transmission path, the respective input gear is arranged upstream of the respective output gear.For the respective switching capability of the respective gear pair, it is irrelevant whether the input gear or the output gear is switchable, i.e., whether the input gear or the output gear is the respective loose gear of the respective gear pair.

[0041] The aforementioned speed and torque ratio of each gear is also simply referred to as the gear ratio of that gear. The ratio of the first gear is also referred to as the first ratio, and the ratio of the second gear is also referred to as the second ratio. It is preferably provided that the second ratio, viewed from the engine output shaft (e.g., the crankshaft) of the internal combustion engine to the output shaft, is smaller than the first ratio, viewed from the engine output shaft to the output shaft.

[0042] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. The drawing shows in Fig. 1 a schematic representation of a hybrid powertrain of a motor vehicle;

[0043] Fig. 2 is a shift table to illustrate different gear ratios of the hybrid powertrain; and

[0044] Fig. 3 is a flowchart illustrating a procedure for performing a gear change in the hybrid powertrain.

[0045] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0046] Fig. 1 shows a schematic representation of a hybrid powertrain 10, also referred to as a hybrid drive device or hybrid drive system, of a motor vehicle, also referred to simply as a vehicle, whose interior, also referred to as the passenger compartment, passenger cell, or cabin, is formed by a body structure of the motor vehicle, for example, a self-supporting body. With reference to Figs. 1 to 3, a method for performing a gear change in the hybrid powertrain 10 is described below. The hybrid powertrain 10 has an internal combustion engine 12, which is also referred to as an internal combustion engine. The internal combustion engine 12 has a housing element 14, which in this case is designed as an engine block. The housing element 14 has cylinders 16, with each cylinder 16 partially delimiting a respective combustion chamber of the internal combustion engine 12.During operation of the internal combustion engine 12, combustion processes take place in the respective combustion chamber, specifically such that within each operating cycle of the internal combustion engine 12, one of the combustion processes takes place in the respective combustion chamber, and in particular, exactly one of the combustion processes. The internal combustion engine 12 has an engine output shaft 18, which is rotatable about an engine output shaft axis relative to the housing element 14. Each operating cycle of the internal combustion engine 12 comprises exactly two complete revolutions of the engine output shaft 18, since the internal combustion engine 12 is designed as a four-stroke engine. Preferably, the internal combustion engine 12 is designed as a reciprocating engine, i.e., as a piston engine, so that the engine output shaft 18 is designed as a crankshaft. Thus, each operating cycle of the internal combustion engine 12 comprises exactly 720 degrees of crank angle.In particular, the internal combustion engine 12 is operated in the fired mode during the process. The internal combustion engine 12 can provide a first torque, also referred to as the first drive torque, via its engine output shaft 18, and the motor vehicle can be driven by means of this first torque. The first torque can be adjusted, i.e., varied, so that the first torque can assume different values, and thus different values ​​of the first torque can be set. This will be explained in more detail below.

[0047] The hybrid powertrain 10 also includes an electric machine 20, which has a stator 22 and a rotor 24. The electric machine 20 can provide a second torque via the rotor 24, which can be used to propel the vehicle. This second torque can also be varied, allowing it to assume different values; that is, different values ​​of the second torque can be set.

[0048] The motor vehicle has, for example, a control element, which is located, in particular, in the interior of the motor vehicle. A person, especially one located in the interior, can operate the control element, particularly with their foot, and thereby move the control element to different positions, particularly relative to a base element. This person is, for example, the driver of the motor vehicle. By operating the control element, the person can adjust, that is, vary, the total torque to be provided by the hybrid powertrain 10 for propelling the motor vehicle.For this purpose, for example, a specific total torque value is assigned to each position of the control element, so that by moving the control element to the respective position, the total torque value assigned to that position can be set. Thus, the person, i.e., the driver of the motor vehicle, can express their desired total torque value by moving the control element to the respective position. The respective position of the control element therefore represents, or characterizes, the person's desired total torque value, also referred to as the driver's request.Thus, the respective total value is or characterizes a respective desired moment, also referred to as driver request moment, which is to be requested by the person by moving the control element to the respective position of the hybrid powertrain 10 and is subsequently to be provided or is provided by the hybrid powertrain 10.In order to provide the total torque, i.e., the respective requested total torque value, and thus fulfill the driver's request, the electric machine 20 and the combustion engine 12 are operated, for example, in such a way that the first torque or the respective value of the first torque and the second torque or the respective value of the second torque add up to the requested, i.e., desired total value, or that the desired, i.e., requested total value results from the first torque or the respective value of the first torque and from the second torque or the respective value of the second torque.This means that the total torque to be provided by the hybrid powertrain 10, i.e., the respective total value of the total torque to be provided by the hybrid powertrain 10, is divided between the first torque and the second torque, i.e., between the value of the first torque and the value of the second torque, such that, for example, to provide the total torque, i.e., to provide the respective total value of the total torque, in particular, one of the values ​​of the first torque and, in particular, one of the values ​​of the second torque are set. It is conceivable that, in particular, one of the values ​​of the first torque is 0, and furthermore, it is conceivable that, in particular, one of the values ​​of the second torque is 0.Thus, it is conceivable that, for example, if the value of the first torque is a value other than 0, the value of the second torque is simultaneously 0 and vice versa, in order to effect the respective, in particular currently requested, total value, or the value of the first torque and the value of the second torque are values ​​other than 0, in order to set, that is, to effect, the respective, in particular currently requested, total value of the total torque.

[0049] The motor vehicle has, for example, at least or exactly two axles arranged one behind the other in the longitudinal direction of the vehicle, namely a first axle and a second axle. The first axle, designated 26, is shown particularly schematically in Fig. 1. Each axle has exactly two wheels arranged on opposite sides of the vehicle in the transverse direction, the wheels of axle 26 being shown schematically in Fig. 1 and designated 28 and 30. This can be seen in Fig.1. The hybrid powertrain 10 is such that, with respect to the vehicle wheels of the vehicle axles, at least or exclusively the vehicle wheels 28 and 30 of the vehicle axle 26 can be driven, so that, by means of the total torque, i.e., by means of the respective total value of the total torque, the vehicle wheels 28 and 30, and thus the motor vehicle, can be driven. The vehicle wheels of the motor vehicle are ground contact elements by means of which the motor vehicle can be supported or is supported downwards in the vertical direction against a ground. In particular, in the method, the motor vehicle is supported downwards in the vertical direction against the ground by means of the ground contact elements of the motor vehicle. In particular, it is provided that in the method the motor vehicle is driven along the ground while the motor vehicle is supported downwards in the vertical direction against the ground by means of the ground contact elements.Thus, in this process, the ground contact elements roll along the ground, especially directly.

[0050] As can be seen from Fig. 1, the hybrid drivetrain 10 has a differential gear 32, also simply referred to as a differential, assigned to the vehicle wheels 28 and 30, via which the vehicle wheels 28 and 30 can be driven by the electric motor 20 and by the internal combustion engine 12, i.e., by the rotor 24 and by the engine output shaft 18. The differential gear 32 has the function, well known from the prior art, of allowing different rotational speeds of the vehicle wheels 28 and 30 when the vehicle is cornering, in particular such that the outer vehicle wheel 28, 30 rotates at a higher speed than the inner vehicle wheel 30, 28 when cornering.

[0051] The hybrid drivetrain 10 has an output shaft 34, which, in the embodiment shown in Fig. 1, is also referred to as the input shaft of the differential gear 32. The differential gear 32 has differential gears (not shown in Fig. 1) via which the vehicle wheels 28 and 30 can be driven by the output shaft 34. This means that the output shaft 34 can drive the differential gears and, via these, drive the vehicle wheels 28 and 30. In particular, if the differential gear 32 is designed as a bevel gear differential, the differential gears are designed as bevel gears. The hybrid drivetrain 10 has a complete transmission 36, which includes a planetary gear set 38, a first sub-transmission 40, and a second sub-transmission 42.The first torque can be transmitted along a first torque transmission path from the motor output shaft 18 to the vehicle wheels 28 and 30, and the second torque can be transmitted along a second torque transmission path from the rotor 24 to the vehicle wheels 28 and 30. With respect to the respective torque transmission path, the complete transmission 36 is arranged downstream of the rotor 24 and downstream of the motor output shaft 18, upstream of the vehicle wheels 28 and 30, and upstream of the differential 32, such that the first torque and the second torque, respectively, on their way from the motor output shaft 18 or the rotor 24 to the vehicle wheels 28 and 30, first flow from the motor output shaft 18 or the rotor 24 to the complete transmission 36, and then via the transmission to the differential 32, and finally via the differential 32 to the vehicle wheels 28 and 30.With respect to the respective torque transmission path, the planetary gear 38 is arranged upstream of the respective sub-gearboxes 40, 42, upstream of the differential gear 32, upstream of the vehicle wheels 28 and 30, and downstream of the motor output shaft 18 and downstream of the rotor 24, such that the first torque and the second torque, respectively, can be transmitted from the motor output shaft 18 and the rotor 24, respectively, via the planetary gear 38 to the respective sub-gearboxes 40, 42. From the planetary gear 38, the first torque and the second torque, respectively, can be transmitted via the respective sub-gearboxes 40, 42 to the output shaft 34. It can be seen that, with respect to the respective torque transmission path, the complete gear unit 36 ​​is arranged upstream of the output shaft 34 and downstream of the motor output shaft 18 and downstream of the rotor 24.The first torque or the second torque from the planetary gear 38 can be transmitted to the output shaft 34 via the respective sub-gearbox 40, 42.

[0052] The hybrid powertrain 10 also includes a locking clutch Kl, a first clutch Al, and a second clutch Bl. The planetary gear set 38 includes a first planet gear set 44 with a first element, a second element, and a third element. The planetary gear set 38 also includes a second planet gear set 46 with a fourth element, a fifth element, and a sixth element. In the embodiment shown in Fig. 1, the first element designated 48 is a first sun gear, the second element designated 50 is a first planet carrier, and the third element designated 52 is a first ring gear. Furthermore, in the embodiment shown in Fig. 1, the fourth element designated 54 is a second sun gear, the fifth element designated 56 is a second planet carrier, and the sixth element designated 58 is a second ring gear. As can be seen from Fig.Figure 1 states that elements 50 and 56, i.e., the second element 50 and the fifth element 56, are permanently and non-rotatably connected to each other. Furthermore, elements 52 and 58, i.e., the third element 52 and the sixth element 58, are permanently and non-rotatably connected to each other. The planetary gear sets 44 and 46 are arranged coaxially to each other, so that each element is rotatable about a main axis of rotation H relative to a housing 60 of the hybrid drive train 10, which is shown schematically in Fig. 1. Since elements 50 and 56 are permanently and non-rotatably connected to each other, and since elements 52 and 58 are permanently and non-rotatably connected to each other, the planetary gear set 38 in the embodiment shown in Fig. 1 is a four-shaft planetary gear set, since the planetary gear set 38 has, in particular, four shafts that are rotatable about the main axis of rotation H relative to the housing 60 and relative to each other. A first of the shafts is or comprises the first element 48.A second wave is or comprises elements 50 and 56. A third wave is or comprises elements 52 and 58, and the fourth wave is or comprises element 54.

[0053] The first planetary gear set 44 comprises the first planetary gears 62. Each planetary gear 62 meshes simultaneously with elements 48 and 52, without meshing with elements 54 and 58. Each planetary gear 62 is rotatably mounted on element 50. The second planetary gear set 46 comprises the second planetary gears 64. Each planetary gear 64 meshes simultaneously with elements 54 and 58, without meshing with elements 48 and 52. Each planetary gear 64 is rotatably mounted on element 56.

[0054] In the embodiment shown in Fig. 1, the internal combustion engine 12, i.e., the engine output shaft 18, can be coupled to the first element 48 in a rotationally fixed manner. A disconnecting clutch K0 is provided for this purpose, by means of which the engine output shaft 18, and thus the internal combustion engine 12, can be connected, i.e., coupled, to the first element 48 in a rotationally fixed manner. This allows the engine output shaft 18, and thus the internal combustion engine 12, to be coupled to the first element 48, in particular in a rotationally fixed manner, such that the first torque emanating from the engine output shaft 18, and thus from the internal combustion engine 12, and thus provided or capable of being provided, can be introduced at the first element 48 and thus via the first element 48 into the planetary gear 38.

[0055] The rotor 24, and thus the electric machine 20, is coupled, in particular permanently, to the elements 52 and 58 in a torque-transmitting manner. Thus, the rotor 24, and thus the electric machine 20, is coupled to the elements 52 and 58 in such a way, in particular in a torque-transmitting manner, and most importantly permanently, that the second torque emanating from the rotor 24, and thus from the electric machine 20, and therefore provided or makeable, can be introduced at the elements 52 and 58 and thus via the elements 52 and 58 into the planetary gear 38.

[0056] The first sub-gearbox 40 has a first switchable gear pair 66, comprising a first gear ZI and a second gear Z2. In the embodiment shown in Fig. 1, gear ZI is, in particular, permanently, rotationally fixed to the second element 50 and thus to the fifth element 56. A first shaft section of the second shaft is designated W1, wherein gear ZI is, in particular, permanently, rotationally fixed to the shaft section W1. The shaft section W1 is a first sub-gearbox input shaft. A second shaft section of the fourth shaft of the planetary gear set 38 is designated W2. The shaft section W2 is a second sub-gearbox input shaft. It can be seen that, because the planetary gear sets 44 and 46 are arranged coaxially to each other, the shafts of the planetary gear set 38, and thus the shaft sections W1 and W2, and thus the sub-gearbox input shafts, are all arranged coaxially to each other and coaxially to the main axis of rotation H.Accordingly, the gear ZI is arranged coaxially to the shaft part W1 and thus coaxially to the second shaft, wherein the gear ZI is, in particular permanently, rotationally fixed to the second shaft of the planetary gear 38.

[0057] The hybrid drive train 10 has a fifth shaft in addition to the four shafts of the planetary gear set 38, which is also referred to as the intermediate shaft ZW or countershaft. It can be seen that the second gear Z2 is arranged coaxially with the intermediate shaft ZW. In the embodiment shown in Fig. 1, the gear ZI is a first fixed gear of the gear pair 66, since the gear ZI is permanently fixed to the shaft section W1 and thus permanently fixed to the second shaft of the planetary gear set 38. In the embodiment shown in Fig. 1, the second gear Z2 is a loose gear, which is rotatably arranged on the intermediate shaft ZW. It can be seen that the gears ZI and Z2 mesh with each other, particularly permanently. It can also be seen that the gear pair 66 can be switched by means of the first coupling Al, which connects the loose gear Z2 to the intermediate shaft ZW in a rotationally fixed manner.

[0058] The second sub-gearbox 42 has a second switchable gear pair 68, which includes a third gear Z3 and a fourth gear Z4. Gears Z3 and Z4 mesh permanently with each other. It can be seen that gear Z3 is arranged coaxially with the shaft section W2 and thus coaxially with the fourth shaft. In the embodiment shown in Fig. 1, gear Z3 is a second fixed gear and gear Z4 is a second loose gear, since gear Z3 is permanently and rotationally fixed to the shaft section W2 and thus permanently and rotationally fixed to the fourth shaft of the planetary gear 38. The fourth gear Z4, designed as a loose gear, is rotatably mounted on the intermediate shaft ZW. The second gear pair 68 is switchable by means of the second clutch Bl, which connects the fourth gear Z4, designed as a loose gear, to the intermediate shaft ZW in a rotationally fixed manner.The respective gear ZI, Z3 is an input gear of the respective gear pair 66, 68, also referred to as the input gear, and the respective gear Z2, Z4 is an output gear of the respective gear pair 66, 68, also referred to as the output gear, since, with respect to the respective torque transmission path, the respective output gear is arranged downstream of the respective input gear and upstream of the output shaft 34. As an alternative to the embodiment shown in Fig. 1, it would be possible for gear Z2 to be designed as a fixed gear, which is permanently and rotationally fixed to the intermediate shaft ZW, so that, for example, gear ZI is then designed as a loose gear, which is rotatably arranged on the shaft section W1 and thus rotatably on the second shaft of the planetary gear set 38.Then, for example, the first coupling Al would allow the gear ZI, which would then be designed as a loose gear, to be connected non-rotatably to the shaft section W1 and thus to the second shaft of the planetary gear 38. Alternatively or additionally, it would be possible for the gear Z4 to be designed as a fixed gear, which is connected non-rotatably, in particular permanently, to the intermediate shaft ZW. Then, for example, the gear Z3 would be designed as a loose gear, which is rotatably arranged on the shaft section W2 and thus on the fourth shaft of the planetary gear 38. Then, for example, the second coupling Bl would allow the gear Z3, which would then be designed as a loose gear, to be connected non-rotatably to the shaft section W2 and thus to the fourth shaft of the planetary gear 38. Furthermore, instead of the intermediate shaft ZW, on which in the Fig.In the embodiment shown in Figure 1, the gears Z2 and Z4, designed as loose gears, are arranged, and two countershafts are used, in particular each with a final reduction pinion, wherein the two final reduction pinions would then mesh with the output shaft 34, i.e. with a respective gear connected or connectable to the output shaft 34, in particular permanently, transmitting torque, in particular rotationally fixed, so that, for example, at the latest at the output shaft 34, in particular at the differential cage, all torque flows of the sub-gearboxes 40 and 42 would converge.

[0059] Since the first coupling Al allows the gear Z2, designed here as a loose gear, to be connected to the intermediate shaft ZW in a rotationally fixed manner, the first coupling Al is designed to couple the first gear pair 66, in particular for torque transmission, to the output shaft 34. Since the gear Z4, designed here as a loose gear, can be connected to the intermediate shaft ZW in a rotationally fixed manner by means of the second coupling Bl, the second coupling Bl is designed to couple the second gear pair 42, in particular for torque transmission, to the output shaft 34.

[0060] Fig. 2 shows a shift table, from which it can be seen that the hybrid powertrain 10 has at least or exactly three switchable gears, also simply referred to as gears, namely a first gear G1, a second gear G2, and an intermediate gear G2*. It can be seen from Fig. 1 that the planetary gear set 38 is to be locked together by means of the locking clutch Kl. In the embodiment shown in Fig. 1, the elements 50, 54, and 56 can be connected to each other in a rotationally fixed manner by means of the locking clutch Kl in order to lock together the planetary gear set 38.

[0061] The gears of the hybrid powertrain 10 are selectable. This means that the respective gear of the hybrid powertrain 10 can be selected or selected. In particular, and preferably always, when one of the gears of the hybrid powertrain 10 is selected, the other gears of the hybrid powertrain 10 are selected.

[0062] The disconnect clutch K0, the locking clutch Kl, the clutch Al, and the clutch Bl are switching elements of the hybrid drivetrain 10. Each switching element can be switched between a closed state and an open state. The closed state is also referred to as the coupling state, and the open state is also referred to as the decoupling state. In the coupling state of the disconnect clutch KO, the engine output shaft 18 is rotationally fixed to the element 48. In the decoupling state of the disconnect clutch KO, the engine output shaft 18 and the element 48 are rotatable relative to each other, and in particular, the engine output shaft 18, and thus the combustion engine 12, is then separated from the rest of the hybrid drivetrain 10, i.e., decoupled. In the coupling state of the locking clutch Kl, the elements 50, 56, and 54 are rotationally fixed to each other.In the disengaged state of the locking coupling Kl, element 54 is rotatable about the main axis of rotation H relative to elements 50 and 56, and the planetary gear 38 is not locked. In the engaged state of the first coupling Al, gear Z4 is rotationally fixed to the intermediate shaft ZW. The intermediate shaft ZW is rotatable about an intermediate shaft axis of rotation relative to the housing 60. For example, the intermediate shaft axis of rotation runs parallel to the main axis of rotation H, with the main axis of rotation H and the intermediate shaft axis of rotation being spaced apart. In the disengaged state of the first coupling Al, gear Z2 is rotatable about the intermediate shaft axis of rotation relative to the intermediate shaft ZW. It can be seen that gears Z2 and Z4 are arranged coaxially with each other and each is coaxial with the intermediate shaft ZW and coaxial with the intermediate shaft axis of rotation. In the engaged state of the second coupling Bl, gear Z4 is rotationally fixed to the intermediate shaft ZW.In the disengaged state of the second coupling Bl, gear Z4 is rotatable about the intermediate shaft's axis of rotation relative to the intermediate shaft ZW. It is also evident that gears ZI and Z3 are arranged coaxially with each other and coaxially with the main axis of rotation H. Furthermore, gears ZI and Z3 are each arranged coaxially with shaft section W1 and coaxially with shaft section W2, and thus coaxially with the second shaft and coaxially with the fourth shaft of the planetary gear set 38.

[0063] In the shift table shown in Fig. 2, "X" means that the respective shift element listed in the shift table, under which the "X" is located, is closed, i.e., in its coupled state. If no "X" is listed under the shift element in the shift table, this means that the shift element is in its disengaged state, i.e., that the shift element is open. Thus, it can be seen from Fig. 2 that the first gear Gl can be engaged or is engaged by the fact that the disconnect clutch KO, the locking clutch Kl, and the first clutch Al are simultaneously closed, i.e., simultaneously in their respective coupled states, while the second clutch Bl is open, i.e., while the second clutch Bl is in its disengaged state.The second gear, G2, can be engaged or is engaged by simultaneously closing the disconnect clutch KO, the first clutch Al, and the second clutch Bl, i.e., by simultaneously being in their respective coupled states, while the locking clutch Kl is open, i.e., while the locking clutch Kl is in its disengaged state. The intermediate gear, G2*, can be engaged or is engaged by simultaneously closing the disconnect clutch KO and the first clutch Al, i.e., by simultaneously being in their coupled states, while the locking clutch Kl and the second clutch Bl are simultaneously open, i.e., while they are in their respective disengaged states. Gears Gl and G2 are fixed gears.Each fixed gear has a fixed, i.e., non-variable, transmission ratio, particularly when viewed from the motor output shaft 18 or the rotor 24 to the output shaft 34. The transmission ratio of the first gear (Gl) is also referred to as the first gear ratio, and the transmission ratio of the second gear (G2) is also referred to as the second gear ratio. In contrast, gear G2* is an intermediate gear, and when the intermediate gear is engaged, the locking clutch (Kl) is open. In this intermediate gear, i.e., when the intermediate gear is engaged, a variable transmission ratio can be set via the planetary gear set 38 into the first sub-gearbox 40 by means of the electric motor 20.In other words, the intermediate gear has a variable, i.e., variable, transmission ratio, in particular from the rotor 24 or the motor output shaft 18 to the output shaft 34, whereby the transmission ratio of the intermediate gear can be varied by varying the rotational speed of the rotor 24, which rotates at that speed around a machine axis of rotation relative to the stator 22.

[0064] To perform the aforementioned gear change particularly advantageously, especially comfortably and efficiently, it is provided that the gear change occurs from first gear Gl to second gear G2. This means that during the gear change, and thus during the process, the initially engaged first gear Gl is disengaged and the initially engaged second gear G2 is engaged. This gear change from first gear Gl to second gear G2, and thus the process for performing the gear change, is illustrated in Fig. 3 by a flowchart. The process begins at block 70.During the aforementioned gear change from first gear Gl to second gear G2, a first step S1 is performed in which the first torque of the internal combustion engine 12 is increased, in particular from a first value of the first torque to a second value of the first torque that is greater than the first value. Preferably, the second value of the first torque is a value other than zero and, in particular, greater than zero, and preferably, the first value of the first torque is a value other than zero and greater than zero. Furthermore, during the first step S1, the electric machine 20 provides the second torque via its rotor 24 as a braking torque, and thus as a braking torque. The braking torque therefore opposes the rotation of elements 52 and 58, and thus the rotation of the third shaft of the planetary gear 38.For example, the procedure is carried out when the motor vehicle is traveling forward, whereby the aforementioned rotation of the third shaft of the planetary gear 38 occurs during or while traveling forward. The braking torque is a braking torque that opposes the aforementioned rotation of the third shaft of the planetary gear 38 during forward travel. When shifting gears from first gear Gl to second gear G2, a second step S2 is performed. In the second step S2, which occurs after the first step S1, the locking clutch Kl is opened, and the second clutch Bl is closed, specifically while the first clutch Al and the disconnect clutch KO remain closed.Thus, for example, the disconnect coupling KO and the first coupling Al are closed both during the first step and during the second step, in particular continuously and therefore without interruption, and preferably the disconnect coupling KO and the first coupling Al are not opened between the first step S1 and the second step S2.

[0065] For example, the first step S1, starting from the beginning of the method illustrated by Block 70, is carried out if and preferably only if a first precondition is met. In a test step PI, it is checked whether the first precondition is met. Preferably, and especially only if, the first precondition is met, the first step S1 is carried out. If the test PI shows that the first precondition is not met, the method returns to Block 70. The first precondition is met if the current position of the control element, also referred to as the accelerator pedal position, i.e., a position value characterizing the current position of the control element, falls below a first pedal threshold value and / or if the rotational speed of the output shaft 34 exceeds a first rotational speed threshold value.It is evident that test PI is performed after the commencement of the procedure as illustrated by block 70 and before the execution of the first step S1, wherein step S1 is performed if and only if test PI shows that the current position of the control element, and thus the position value characterizing the current position of the control element, is less than the first pedal threshold and / or the current speed of the output shaft 34 is greater than the first speed threshold. Preferably, a second test P2 is performed after the first step S1, that is, after the execution of the first step S1 and before the execution of the second step S2.The second check, P2, verifies whether a second precondition is met. For example, the second step, S2, is performed after the first step, Sl, if and only if the second precondition is met. Thus, if the second check, P2, shows that the second precondition is met, then, and preferably only if, the second step, S2, is performed. If the second check, P2, shows that the second precondition is not met, the procedure returns to the first check, PI, particularly via a cancellation step, AS.The second precondition is fulfilled if and preferably only if the current position of the control element, and thus the position value characterizing the current position of the control element, falls below a second pedal threshold value that is lower than the first pedal threshold value, and / or if the current rotational speed of the output shaft 34 exceeds a second rotational speed threshold value that is higher than the first rotational speed threshold value. After the second step S2, that is, after the second step S2 has been executed, the method returns, for example, via the cancellation step AS, to the beginning of the method illustrated by block 70. In the cancellation step AS, the first step Sl is cancelled.This means that the first step Sl, or rather the processes or settings effected by or during the first step Sl, such as increasing the first torque and providing the second torque as the braking torque, are not maintained indefinitely. Instead, during the cancellation step AS, a more energy- and fuel-efficient setting of the first and second torques is made compared to performing the first step Sl; this setting is also referred to as torque adjustment. For example, at the beginning of the process, and thus with first gear Gl engaged, there is equality of speed across the locking clutch Kl, which is closed. It is desirable to adjust the second torque of the electric machine 20 so that there is also equality of torque across the locking clutch Kl.Using the fixed gear ratios of the two planetary gear sets 44 and 46, the second torque, or a value for the second torque, can be calculated for a given and / or current first torque of the internal combustion engine 12 in order to achieve the aforementioned torque equality. Before the gear change, also referred to as shifting, and especially with the control element in a constant position and thus with a constant desired torque, the first and second torques are modified so that, on the one hand, there is no torque across the locking clutch Kl, and on the other hand, the total torque desired by the driver for starting the vehicle remains unchanged. This allows the gear change to be carried out without any loss of propulsion and is therefore imperceptible to the driver.The previously described torque-free state across the locking clutch Kl is achieved in the first step S1. Subsequently, that is, in the second step S2, synchronization is performed at the second clutch to be engaged in order to achieve equal rotational speeds at the clutch Bl to be engaged. This is also achieved by selectively changing the rotational speed of the rotor 24 and, if necessary, by changing the rotational speed of the motor output shaft 18.

[0066] Reference symbol list

[0067] 10 Hybrid powertrain

[0068] 12 Internal combustion engine

[0069] 14 Housing element

[0070] 16 cylinders

[0071] 18 Engine output shaft

[0072] 20 electric machine

[0073] 22 Stator

[0074] 24 Rotor

[0075] 26 vehicle axle

[0076] 28" vehicle wheel

[0077] 30 vehicle wheel

[0078] 32 Differential gears

[0079] 34 Output shaft

[0080] 36 Total gearbox

[0081] 38 planetary gears

[0082] 40 first sub-gearbox

[0083] 42 second sub-transmission

[0084] 44 first planetary gear set

[0085] 46 second planetary gear set

[0086] 48 first element

[0087] 50 second element

[0088] 52 third element

[0089] 54 fourth element

[0090] 56 fifth element

[0091] 58 sixth element

[0092] 60 cases

[0093] 62 planetary gear

[0094] 64 planetary gear

[0095] 66 first gear pair

[0096] 68 second gear pair

[0097] 70 blocks

[0098] AS cancellation step

[0099] First clutch AS release step

[0100] BL second clutch

[0101] Gl first gear

[0102] G2 second gear

[0103] G2* gear

[0104] H Main axis of rotation

[0105] KO disconnect coupling

[0106] Kl locking coupling

[0107] PI exam

[0108] P2 exam

[0109] S1 first step

[0110] S2 second step

[0111] ZI first gear

[0112] Z2 second gear

[0113] Z3 third gear

[0114] Z4 fourth gear

[0115] ZW intermediate shaft

Claims

Patent claims 1. Method for performing a gear change in a hybrid powertrain (10) of a motor vehicle, wherein: - the hybrid powertrain (10) comprises an internal combustion engine (12), an electric machine (20), a planetary gear set (38), a first sub-gear set (40), a second sub-gear set (42), a locking clutch (Kl), a first clutch (Al), a second clutch (Bl) and an output shaft (34); - the planetary gear (38) comprises a first planet gear set (44) with a first element (48), a second element (50) and a third element (52) and a second planet gear set (46) with a fourth element (54), a fifth element (56) and a sixth element (58); - the second element (50) is connected to the fifth element (56) in a rotationally fixed manner; - the third element (52) is connected to the sixth element (58) in a rotationally fixed manner; - the locking coupling (Kl) is designed to lock the planetary gear (38); - the internal combustion engine (12) is coupled or can be coupled to the first element (48) in such a way that a first torque emanating from the internal combustion engine (12) can be introduced into the planetary gear (38) at the first element (48); - the electric machine (20) is coupled or can be coupled to the third element (52) in such a way that a second torque emanating from the electric machine (20) can be introduced into the planetary gear (38) at the third element (52); - the first partial transmission (40) has a first switchable gear pair (66) with a first gear (ZI) which is non-rotatably connected or connectable to the second element (50) and a second gear (Z2) which meshes with the first gear (ZI); - the second sub-transmission (42) has a second switchable gear pair (68) with a third gear (Z3) which is non-rotatably connected or connectable to the fourth element (54) and a fourth gear (Z4) which meshes with the third gear (Z3); - the first clutch (Al) is designed to couple the first gear pair (66) with the output shaft (34); - the second clutch (Bl) is designed to couple the second gear pair (68) with the output shaft (34); - a first gear (Gl) can be engaged by the locking clutch (Kl) being closed, the first clutch (Al) being closed, and the second clutch (Bl) being open; and - a second gear (G2) can be engaged by the locking clutch (Kl) being open, the first clutch (Al) being closed and the second clutch (Bl) being closed; characterized in that when changing gears from the first gear (Gl) to the second gear (G2): - in a first step (Sl) the first torque of the combustion engine (12) is increased and the electric machine (20) provides the second torque as a braking torque; and - in a second step (S2) following the first step (Sl), the locking clutch (Kl) is opened and the second clutch (Bl) is closed; wherein the first step (Sl) is carried out if, as a first precondition, the accelerator pedal position falls below a first pedal threshold and / or if the speed of the output shaft (34) exceeds a first speed threshold, and wherein the second step is carried out if, as a second precondition, the accelerator pedal position falls below a second pedal threshold that is lower than the first pedal threshold.

2. Method according to claim 1, characterized in that in the first step (Sl) the first torque of the internal combustion engine (12) and the braking torque of the electric machine (20) are adjusted such that a sum the first torque of the internal combustion engine (12) and the braking torque of the electric machine (20) equals a driver-requested torque.

3. Method according to claim 1 or 1, characterized in that in the first step (Sl) the first torque of the internal combustion engine (12) and the braking torque of the electric machine (20) are adjusted such that there is no load between the coupling halves of the locking coupling (Kl).

4. Method according to one of the preceding claims, characterized in that in the first step (Sl) the first torque of the internal combustion engine (12) and the braking torque of the electric machine (20) are set as a function of a first stationary gear ratio of the first planetary gear set (44) and as a function of a second stationary gear ratio of the second planetary gear set (46).

5. Method according to one of the preceding claims, characterized in that the locking coupling (Kl) is designed to connect the fourth element (54) to the second element (50) in a rotationally fixed manner in order to lock the planetary gear (38).

6. Method according to one of the preceding claims, characterized in that the first element (48) is a first sun gear, the second element (50) is a first planet carrier, the third element (52) is a first ring gear, the fourth element (54) is a second sun gear, the fifth element (56) is a second planet carrier and the sixth element (58) is a second ring gear.

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