Method for controlling the clutch of a hybrid vehicle and system for shifting a hybrid vehicle

Abstract

Method for controlling the clutch of a hybrid vehicle, comprising: a first planetary gear unit (PG1) having a first sun gear (S1), a first planetary gear, a first ring gear (H1) and a first planetary gear carrier (P1); a second planetary gear unit (PG2) having a second sun gear (S2) rotating together with the first sun gear (S1), a second planetary gear, a second ring gear (H2) and a second planetary gear carrier (P2) transmitting torque to an output shaft (GT output); a drive (A) arranged to rotate the first planetary gear carrier (P1) of the first planetary gear unit (PG1); a first motor / generator (MG1) arranged to rotate the first ring gear (H1); a second motor / generator (MG2) arranged to rotate the second sun gear (S2); a first brake (BR1) arranged to stop rotation of the first motor / generator (MG1) and the first ring gear; a first clutch (KU1) arranged to connect the first planetary gear carrier (P1) to the first ring gear so that they rotate together; a second clutch (KU2) arranged to connect the first planetary gear carrier (P1) to the second ring gear so that they rotate together; a second brake (BR2) arranged to selectively stop rotation of the second ring gear (H2); and one or more control units which are designed to release the first / second brakes (BR1, BR2) and the first / second clutches (KU1, KU2), for Disengaging the one or more clutches (KU1, KU2) and brakes (BR1, BR2) from a transmission when the transmission is placed in a neutral position; and Controlling an input (A) and a first and second motor / generator (MG1, MG2) by at least one of the one or more control units to prevent a rotating element of the transmission from rotating when the one or more clutches (KU1, KU2) and one or more brakes (BR1, BR2) of the transmission are in the neutral position until the transmission is subsequently shifted to a drive or reverse position by calculating a target speed of the first motor / generator (MG1), wherein a first calculation is used by the control unit(s) to calculate the target speed of the first motor / generator (MG1) when an output speed is greater than a predetermined value, and a second calculation is used by the control unit(s) to calculate the target speed of the first motor / generator (MG1) when the output speed is less than or equal to the predetermined value.

Description

BACKGROUND OF THE INVENTION(a) Technical Field

[0001] The present invention relates to a method for shifting a hybrid vehicle that combines a drive and a motor to generate a steady-state torque and to transmit the steady-state torque to an output shaft by means of a transmission. (b) Description of the associated technology

[0002] Generally, an automatic transmission uses hydraulic pressure to shift gears in a multi-stage process, thereby delivering appropriate torque from the steady-state torque of a drive / motor according to a driving situation. Some hybrid vehicles use two motor / generators (MG) and a drivetrain connected by a planetary gear train, controlling the motor / generator to achieve continuously variable transmission.

[0003] At least two motors and a planetary gear train are typically used in conjunction to create an electric continuously variable transmission (CVT), allowing the speed of the drivetrain to be freely controlled. Clutches and / or brakes are often used between the planetary gear trains or their rotating elements. By releasing and / or engaging the clutches and / or brakes in the CVT, the running characteristics of the motor and drivetrain can be controlled. In a conventional CVT, the clutches and / or brakes are released to prevent torque from being transmitted to the transmission output in a neutral (N) or park (P) position of the transmission.

[0004] When the transmission is shifted from park or neutral to drive (D) or reverse (R), a difference in engine speed creates slippage in the clutch and brake. As a result, frictional force generates vibration / noise, reducing transmission durability.

[0005] In this context, DE 10 2007 000 207 A1 discloses a torque control selection device that selects one of a first torque control device and a second torque control device (88) as a control device for controlling a torque output by an automatic transmission based on a vehicle condition. The first torque control device controls the output torque by controlling an engagement pressure for a first clutch (C1) or a second clutch. The second torque control device controls the output torque by controlling a reaction torque produced by a first motor when power transmission is permitted in a shift mechanism.

[0006] Furthermore, DE 10 2009 046 730 A1 discloses a drive train for a hybrid vehicle which enables a multiple drive mode combined with a fixed gear ratio drive mode, such as the gear ratios of a conventional transmission, and high efficiency drive, thereby increasing the fuel efficiency of the vehicle.

[0007] The above information disclosed in this Background Description section is provided only to facilitate understanding of the background of the invention and may therefore contain information that does not constitute prior art that is already known to those skilled in the art in this country. OVERVIEW OF THE INVENTION

[0008] It is an object of the present invention to provide a clutch control for a hybrid vehicle which prevents slippage in a clutch or a brake when a transmission is shifted from a park or a neutral or drive or reverse position.

[0009] The object is achieved by a method for clutch control having the features of claims 1 or as well as a system for shifting a hybrid vehicle having the features of claims 5 or 10. Advantageous further developments can be found in the subclaims.

[0010] Accordingly, the present invention reduces vibration / noise and improves durability.

[0011] A control device and method for coupling a hybrid vehicle according to an exemplary embodiment of the present invention includes a first planetary gear unit having a first sun gear, a first planetary gear set, a first ring gear, and a first planetary gear carrier; a second planetary gear unit having a second sun gear that rotates together with the first sun gear, a second planetary gear set, a second ring gear, and a second planetary gear carrier that transmits torque to an output shaft; an input arranged to rotate the first planetary gear carrier of the first planetary gear unit; a first motor / generator arranged to rotate the first ring gear; a second motor / generator arranged to rotate the second sun gear; a first brake arranged to stop rotation of the first motor / generator and the first ring gear;a first clutch arranged to connect the first planetary gear carrier to the first ring gear so that they rotate together; a second clutch arranged to connect the first planetary gear carrier to the second ring gear so that they rotate together; a second brake arranged to selectively stop rotation of the second ring gear; and one or more control devices configured to release the first / second brakes and the first / second clutches (KU1, KU2). The method includes releasing one or more clutches and brakes from a transmission in a neutral position, and preventing a rotating element from rotating when one or more clutches and brakes of the transmission are in the neutral position by controlling a drive and a motor / generator until the transmission is subsequently shifted to a drive or reverse position.

[0012] Furthermore, the present invention is adapted to control the speed of a motor / generator such that a steady-state speed of a rotating element directly connected to an input is equal to that of the input when a transmission is subsequently shifted to a drive or reverse position.

[0013] Specifically, the method for clutch control of a hybrid vehicle may include a drivetrain that rotates a first planetary gear carrier of a first planetary gear unit, a first motor / generator that rotates a first ring gear of the first planetary gear unit, and a second motor / generator that rotates a second sun gear of a second planetary gear unit. Additionally, the system may include one or more of, e.g., control units, processors, etc.which are configured to release one or more brakes and clutches when the transmission is shifted into the park or neutral position, to determine whether a second brake should be operated to stop a second ring gear of the second planetary gear unit or a second clutch should be operated for direct connection to the first planetary gear carrier with the second ring gear of the second planetary gear unit in a drive or reverse position, to prepare the transmission for subsequent shifting into a drive or reverse position, and to control the drive, the first motor / generator and the second motor / generator such that the second ring gear is not rotated if it is determined that a ring gear is held by the second brake, the first motor / generator being speed controlled.Additionally, if it is determined that the input is to the second ring gear from the second clutch, then the input, the first motor / generator, and the second motor / generator can be controlled such that a steady-state speed of the second ring gear is equal to the output speed of the input. If an output speed of the transmission is greater than a predetermined value, then the input, the first motor / generator, and the second motor / generator can be controlled such that a steady-state speed of the second ring gear is equal to an output speed of the input. The speed of the first motor / generator can be regulated for optimization.

[0014] In addition, if an output speed of a transmission is less than a predetermined value, the drive, the first motor / generator and the second motor / generator may be controlled such that the second ring gear is not rotated.

[0015] A method for clutch control of a hybrid vehicle having a first planetary gear unit with a first sun gear, a first planetary gear, a first ring gear, and a first planetary gear carrier; a second planetary gear unit with a second sun gear rotating together with the first sun gear, a second planetary gear, a second ring gear, and a second planetary gear carrier that transmits torque to an output shaft; an input arranged to rotate a first planetary gear carrier of the first planetary gear unit; a first brake arranged to stop rotation of the first motor / generator and the first ring gear; a first clutch arranged to connect the first planetary gear carrier to the first ring gear so that they rotate together;a second clutch arranged to connect the first planetary gear carrier to the second ring gear so that they rotate together; and a second brake arranged to selectively stop rotation of the second ring gear. The present invention may include releasing the first / second brakes and the first / second clutches if a transmission is shifted to a park (P) position or a neutral (N) position, determining whether to apply the first brake or apply the second clutch to prepare for a drive (D) position or a reverse (R) position in a current park state or a current neutral state, and controlling the drive, the first motor / generator, and the second motor / generator so that the second ring gear is not rotated if it is determined that the first brake should be applied.

[0016] Again, if it is determined that the second clutch is to be actuated, then the drive, the first motor / generator, and the second motor / generator may be controlled such that an output speed of the drive is equal to a steady-state speed of the second ring gear.

[0017] As described above, in a clutch control method of a hybrid vehicle according to an exemplary embodiment of the present invention, a shift shock or a slip is minimized when a transmission is shifted from a park or a neutral position to a drive or a reverse state to improve a shifting feel or safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic diagram of a switching system of a hybrid vehicle according to an exemplary embodiment of the present invention. Fig. 2A, B is a speed diagram showing an EVG1 mode and an EVG2 mode in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. Fig. 3 is a speed diagram showing a park / neutral state in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. Fig. 4A, B is a speed diagram showing a flow that prepares an EVG1 mode in a park / neutral position in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. Fig. 5A, B is a speed diagram showing a flow that prepares an EVG2 mode in a park / neutral position in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. Fig. 6 and Fig. 7 are flowcharts showing processes that prepare an EVG1 mode and an EVG2 mode in a park / neutral state in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0019] Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0020] It is understood that the term "vehicle" or "vehicle..." or other similar expressions, as used herein, includes motor vehicles in general, such as passenger cars, including all-wheel-drive off-road vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels produced from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more power sources, for example, both gasoline-powered and electric-powered vehicles.

[0021] Fig. 1 is a schematic diagram of a switching system of a hybrid vehicle according to an exemplary embodiment of the present invention. Referring to Fig. 1, a gearshift system of a hybrid vehicle comprises a drive (A), a first planetary gear unit PG1, a second planetary gear unit PG2, a first motor / generator MG1, a second motor / generator MG2, a first clutch KU1, a second clutch KU2, a first brake BR1, a second brake BR2 and an output shaft of the transmission (GT output).

[0022] The first planetary gear unit PG1 includes a first sun gear S1 at the center thereof, a pair or a plurality of first gears Z1 externally meshing with the first sun gear S1, and a first ring gear H1 internally meshing with the first gear Z1, wherein the first planetary gear carrier P1 connects the first gear Z1 to rotate axially around the first sun gear S1.

[0023] The second planetary gear unit PG2 includes a second sun gear S2 at the center thereof, a pair or a plurality of second gears Z2 externally meshing with the second sun gear S2, and a second ring gear H2 internally meshing with the second gear Z2, wherein the second planetary gear carrier P2 connects the second gear Z2 to rotate axially around the second sun gear S2.

[0024] An output shaft of the drive (A) is connected to the first planetary gear carrier P1, and the drive (A) rotates the first planetary gear carrier P1 axially around the first sun gear S1. Additionally, the first motor / generator MG1 is configured to rotate the first ring gear H1. Furthermore, the first brake BR1 is configured to selectively decelerate (stop) the first ring gear H1. The first sun gear S1 and the second sun gear S2 are connected by a shaft to rotate together, and the second motor / generator MG2 is configured to rotate the second sun gear S2.

[0025] The first coupling KU1 selectively connects the first planet carrier P1 to the first ring gear H1 so that they rotate or stop together, and the second coupling KU2 selectively connects the first planet carrier P1 to the second ring gear H2 so that they rotate or stop together.

[0026] The second brake BR2 is mounted to selectively brake the second ring gear H2. Furthermore, the second planetary gear carrier P2 is connected to an output shaft (GT output) of a transmission to provide torque from the input (A), the first motor / generator MG1, and the second motor / generator MG2 to one or more wheels in the system architecture of the vehicle's drivetrain.

[0027] Fig. 2A, B is a speed diagram showing an Electronically Variable Transmission (EVG) EVG1 mode ( Fig. 2A) and an EVG2 mode ( Fig. 2B) in a method for gearshifting a hybrid vehicle according to an exemplary embodiment of the present invention.

[0028] Referring to Fig. 2A, the transmission of the hybrid vehicle performs an EVG1 mode in a predetermined state (for example, drive or reverse state). As illustrated, the first ring gear H1, the first planetary carrier P1, the first and second sun gears S1 and S2, the second planetary carrier P2, and the second ring gear H2 are arranged on a horizontal axis according to a predetermined gear ratio. The first motor / generator MG1, the input (A), and the second motor / generator MG2 are arranged along a line to form a predetermined speed line, and the second motor / generator MG2, the output shaft (GT output), and the second ring gear H2 are arranged along a line to form a predetermined speed line.

[0029] In the EVG1 mode, the second brake BR2 is applied, the other brake (BR1) and clutches (KU1, KU2) are released, and the second ring gear H2 is held by the BR2. As can be seen from Fig. As can be seen in Figure 2A, the output shaft of the transmission (GT output) has a lower speed in this mode than the speed limit of MG2.

[0030] Referring to Fig. 2B, the transmission of the hybrid vehicle performs an EVG2 mode in a predetermined state (for example, drive or reverse state). As in Fig. As shown in Figure 2B, the first ring gear H1, the first planetary carrier P1, the first and second sun gears S1 and S2, the second planetary carrier P2, and the second ring gear H2 are arranged on a horizontal axis according to a predetermined gear ratio. The first motor / generator MG1, the input (A), and the second motor / generator MG2 are arranged along a line to form a predetermined speed line, and the second motor / generator MG2, the output shaft (GT output), and the second ring gear H2 are arranged along a line to form a predetermined speed line.

[0031] The second clutch KU2 is actuated and the other brakes (BR1, BR2) and the clutch (KU1) are released in the EVG2 mode and a steady-state speed of the drive (A) is controlled such that it is equal to that of the second ring gear H2 by actuating KU2.

[0032] However, the output shaft (GT output) has a predetermined high speed from the first motor / generator MG1, the drive (A), and the second motor / generator MG2. In EVG2 mode, the output speed to GT is determined by the maximum or minimum speed of MG1, MG2, and the drive, and its output speed to GT can be faster than that of EVG2.

[0033] Fig. 3 is a speed diagram showing a park / neutral state in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. Referring to Fig. 3, when the transmission is placed in a park or neutral state, the transmission releases all clutches and brakes to apply a park (P) or neutral (N) arrangement. As in Fig. As shown in Figure 3, the first ring gear H1, the first planetary gear carrier P1, the first and second sun gears S1 and S2, the second planetary gear carrier P2, and the second ring gear H2 are arranged on a horizontal axis according to a predetermined gear ratio. The first motor / generator MG1, the input (A), and the second motor / generator MG2 form a predetermined rotational speed along one line, and the second motor / generator MG2, the output shaft (GT output), and the second ring gear H2 form a predetermined line along another line.

[0034] In a park / neutral mode, all clutches and brakes are released, the output shaft (GT output) rotates in accordance with the vehicle's speed, the input (A) is controlled to output a predetermined torque, and the first and second motor / generators MG1 and MG2 are controlled to output a predetermined speed. Meanwhile, the speed of the second ring gear H2 and the speed of the input are controlled to prepare for the EVG1 mode and the EVG2 mode in a park / neutral state according to an exemplary embodiment of the present invention. Hereinafter, this invention will be described in detail with reference to Fig. 4, Fig. 5, Fig. 6 and Fig. 7 are described.

[0035] Fig. 4A, B is a speed diagram showing a flow that prepares an EVG1 mode in a park / neutral state in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention. Fig. 4A has a predetermined speed of an output shaft (GT output), all clutches and brakes are released to maintain a park (P) or a neutral (N) position in a transmission, and the first motor / generator MG1 and the input (A) are speed-controlled so that the steady-state speed of the second ring gear H2 is controlled to become 0 when an output shaft (GT output) has a predetermined speed.

[0036] Accordingly, when the EVG1 mode is performed, by switching from a park or neutral position to a drive (D) or reverse (R) position, the second brake BR2 is applied with a certain degree of slip.

[0037] Fig. 4B has a speed of 0 for an output shaft (GT output), all clutches and brakes are released to maintain a park (P) or a neutral (N) position of the transmission, and the first motor / generator MG1 and the input (A) are speed-controlled so that the steady-state speed of the second ring gear H2 is controlled to become 0 when an output shaft (GT output) has a predetermined speed.

[0038] Accordingly, when the EVG1 mode is performed, by switching from a park or neutral position to a drive (D) or reverse (R) position, the second brake BR2 is applied with a certain degree of slip.

[0039] Fig. 5A, B is a speed diagram showing a flow that prepares an EVG2 mode in a park / neutral state in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention.

[0040] Fig. 5A has a predetermined speed of an output shaft (GT output), all clutches and brakes are released to maintain a park (P) or a neutral (N) position in a transmission, and the first motor / generator MG1 and the input (A) are speed-controlled so that the steady-state speed of the second ring gear H2 is controlled to be equal to the steady-state speed of the input (A) when an output shaft (GT output) has a predetermined speed.

[0041] Accordingly, when the EVG2 mode is implemented, by switching from a park or neutral position to a drive (D) or reverse (R) position, the second clutch KU2 is actuated with a certain degree of slip.

[0042] Fig. 6 and Fig. 7 are flowcharts showing processes that prepare an EVG1 mode and an EVG2 mode in a park / neutral state in a gear shifting method of a hybrid vehicle according to an exemplary embodiment of the present invention.

[0043] Referring to Fig. 6, the control is started at S600, and an engine state, a target idle speed of the drive, an existing speed of a drive (A), a speed of the first motor / generator MG1, a speed of the second motor / generator MG2, a speed of the output shaft of the transmission (GT output), and a target charging power are detected / calculated in S610.

[0044] In S610, it is determined whether the speed of the transmission output shaft (GT) is greater than a predetermined value in EVG1 mode or EVG2 mode. If the speed of the transmission output shaft (GT output) exceeds a predetermined value, S620 is performed, and if the speed of the transmission output shaft (GT output) is lower than a predetermined value, S630 is performed.

[0045] At S620, a target speed of the second ring gear is controlled to be equal to a steady-state speed of the input, and at S630, a target speed of the second ring gear is controlled to become 0. At S620, a target speed of the first motor / generator MG1 is calculated to become (1+R1+R2) * R1 * input speed - (1+R2) / R1 * speed of the output shaft of the transmission (GT output). At S630, a target speed of the first motor / generator MG1 is calculated to become (1+R1) / R1 * input speed - (1+R2) / R1 * speed of the output shaft of the transmission (GT output). In addition, a speed of the first motor / generator MG1 is controlled as described in S635.

[0046] In the above equations, R represents the gear ratio of the planetary gear set, where R = the number of teeth of a ring gear / the number of teeth of a sun gear. That is, R1 = the number of teeth of a first ring gear / the number of teeth of a first sun gear, and R2 = the number of teeth of a second ring gear / the number of teeth of a second sun gear.

[0047] In S640, the system, for example, a processor or a control unit, determines whether the drive is operating. If the drive is operating, then the system / method proceeds to step A of Fig. 7, and if the drive is not operating, then the system / method continues to step B of Fig. 7.

[0048] Referring to B of Fig. 7, the output torque of the second motor / generator MG2 is 0, and the output torque of the driver (A) is 0 in a state where the driver (A) is not operating. In this case, only the first motor / generator MG1 is speed-controlled.

[0049] Referring to A of Fig. 7, a target charging power is calculated in S700. The target charging power is calculated by dividing the target charging power by the speed of the drive when the drive (A) is operating.

[0050] A torque of the second motor / generator MG2 is calculated from a target charging torque / (1+R1) in S710 to perform charging by speed control of the first motor / generator MG1 and the engine (A).

[0051] In S720, the speed is controlled according to the target charging torque, and a torque is added according to the target charging torque to be output at this speed. At S750, the steady-state speed and torque of the drive (A), the first motor / generator MG1, and the second motor / generator MG2 are output, respectively, and control ends at S760. Description of symbols S1 First sun gear Z1 First gear transmission H1 First ring gear P1 First planet carrier BR1 First Brake BR2 Second Brake KU1 First clutch KU2 Second clutch A drive MG1 First Motor / Generator MG2 Second Motor / Generator S2 Second sun gear Z2 Second gear transmission H2 Second ring gear P2 Second planet carrier GT output output shaft (of the gearbox)

Claims

[1] Method for controlling the clutch of a hybrid vehicle, comprising: a first planetary gear unit (PG1) having a first sun gear (S1), a first planetary gear, a first ring gear (H1) and a first planetary gear carrier (P1); a second planetary gear unit (PG2) having a second sun gear (S2) rotating together with the first sun gear (S1), a second planetary gear, a second ring gear (H2) and a second planetary gear carrier (P2) transmitting torque to an output shaft (GT output); a drive (A) arranged to rotate the first planetary gear carrier (P1) of the first planetary gear unit (PG1); a first motor / generator (MG1) arranged to rotate the first ring gear (H1); a second motor / generator (MG2) arranged to rotate the second sun gear (S2); a first brake (BR1) arranged to stop rotation of the first motor / generator (MG1) and the first ring gear; a first clutch (KU1) arranged to connect the first planetary gear carrier (P1) to the first ring gear so that they rotate together; a second clutch (KU2) arranged to connect the first planetary gear carrier (P1) to the second ring gear so that they rotate together; a second brake (BR2) arranged to selectively stop rotation of the second ring gear (H2); and one or more control units which are designed to release the first / second brakes (BR1, BR2) and the first / second clutches (KU1, KU2), for Disengaging the one or more clutches (KU1, KU2) and brakes (BR1, BR2) from a transmission when the transmission is placed in a neutral position; and Controlling an input (A) and a first and second motor / generator (MG1, MG2) by at least one of the one or more control units to prevent a rotating element of the transmission from rotating when the one or more clutches (KU1, KU2) and one or more brakes (BR1, BR2) of the transmission are in the neutral position until the transmission is subsequently shifted to a drive or reverse position by calculating a target speed of the first motor / generator (MG1), wherein a first calculation is used by the control unit(s) to calculate the target speed of the first motor / generator (MG1) when an output speed is greater than a predetermined value, and a second calculation is used by the control unit(s) to calculate the target speed of the first motor / generator (MG1) when the output speed is less than or equal to the predetermined value. [2] A clutch control method of a hybrid vehicle according to claim 1, wherein the rotating element is a ring gear (H1, H2) of a planetary gear unit (PG1, PG2). [3] Method for controlling the clutch of a hybrid vehicle, comprising: a first planetary gear unit (PG1) comprising a first sun gear (S1), a first planetary gear, a first ring gear (H1) and a first planetary gear carrier (P1); a second planetary gear unit (PG2) having a second sun gear (S2) rotating together with the first sun gear (S1), a second planetary gear, a second ring gear (H2) and a second planetary gear carrier (P2) transmitting torque to an output shaft (GT output); a drive (A) arranged to rotate the first planetary gear carrier (P1) of the first planetary gear unit (PG1); a first motor / generator (MG1) arranged to rotate the first ring gear (H1); a second motor / generator (MG2) arranged to rotate the second sun gear (S2); a first brake (BR1) arranged to stop rotation of the first motor / generator (MG1) and the first ring gear; a first clutch (KU1) arranged to connect the first planetary gear carrier (P1) to the first ring gear so that they rotate together; a second clutch (KU2) arranged to connect the first planetary gear carrier (P1) to the second ring gear so that they rotate together; a second brake (BR2) arranged to selectively stop rotation of the second ring gear (H2); and one or more control units which are / are designed to release the first / second brakes (BR1, BR2) and the first / second clutches (KU1, KU2), for Releasing the clutches (KU1, KU2) and the brakes (BR1, BR2) to bring a transmission into a neutral state; and Controlling a rotational speed of a first motor / generator (MG1) by calculating a target rotational speed of the first motor / generator (MG1), wherein a first calculation is used by the control unit(s) to calculate the target rotational speed of the first motor / generator (MG1) when an output rotational speed is greater than a predetermined value, and a second calculation is used by the control unit(s) to calculate the target rotational speed of the first motor / generator (MG1) when the output rotational speed is less than or equal to the predetermined value, wherein by means of the control the steady-state rotational speed of at least two rotational elements of the transmission which are to be coupled to one another is set equal when the transmission is subsequently switched to a drive or reverse position. [4] A method for controlling the clutch of a hybrid vehicle according to claim 3, wherein at least one of the two rotating elements is a ring gear (H1, H2) of a planetary gear unit (PG1, PG2). [5] A system for switching a hybrid vehicle, the system comprising: a drive (A) operatively connected to a first planetary gear carrier (P1) of a first planetary gear unit (PG1); a first motor / generator (MG1) operatively connected to a first ring gear (H1) of the first planetary gear unit (PG1); a second motor / generator (MG2) operatively connected to a second sun gear (S2) of a second planetary gear unit (PG2); and a control unit configured to release one or more brakes (BR1, BR2) and clutches (KU1, KU2) when a transmission is shifted to a park or neutral position, to determine whether a second brake (BR2) should be operated to stop a second ring gear (H2) of the second planetary gear unit (PG2), and whether a first clutch (KU1) should be actuated to directly connect the first planetary gear carrier (P1) to the first ring gear (H1) of the first planetary gear unit (PG1) when the transmission is subsequently shifted to a drive or reverse position, to prepare the transmission for shifting to the drive or reverse position, and to prevent the second ring gear (H2) from being actuated by controlling the drive (A) and the first motor / generator (MG1), wherein the first motor / generator (MG1) is speed-controlled by calculating a target speed of the first motor / generator (MG1),wherein a first calculation is used by the control unit to calculate the target speed of the first motor / generator (MG1) when an output speed is greater than a predetermined value, and a second calculation is used by the controller to calculate the target speed of the first motor / generator (MG1) when the output speed is less than or equal to the predetermined value. [6] The system of claim 5, wherein the controller is further configured to control the input (A), the first motor / generator (MG1) and the second motor / generator (MG2) such that a steady-state speed of the second ring gear (H2) is equal to the output speed of the input (A) when it is determined that the input (A) is connected to the second ring gear (H2) through the second clutch. [7] The system according to claim 6, wherein the control unit is further configured to control the drive (A), the first motor / generator (MG1) and the second motor / generator (MG2) such that a steady-state speed of the second ring gear (H2) is equal to the output speed of the drive (A) if the output speed is greater than the predetermined value. [8] The system according to claim 7, wherein a speed of the first motor / generator (MG1) is controlled. [9] The system according to claim 6, wherein the control unit is further configured to control the drive (A), the first motor / generator (MG1) and the second motor / generator (MG2) such that the second ring gear (H2) is not rotated if an output speed from a transmission is less than the predetermined value. [10] A system for switching a hybrid vehicle, the system comprising: a first planetary gear unit (PG1) comprising a first sun gear (S1), a first planetary gear, a first ring gear (H1) and a first planetary gear carrier (P1); a second planetary gear unit (PG2) having a second sun gear (S2) rotating together with the first sun gear (S1), a second planetary gear, a second ring gear (H2) and a second planetary gear carrier (P2) transmitting torque to an output shaft (GT output); a drive (A) arranged to rotate the first planetary gear carrier (P1) of the first planetary gear unit (PG1); a first motor / generator (MG1) arranged to rotate the first ring gear (H1); a second motor / generator (MG2) arranged to rotate the second sun gear (S2); a first brake (BR1) arranged to stop rotation of the first motor / generator (MG1) and the first ring gear; a first clutch (KU1) arranged to connect the first planetary gear carrier (P1) to the first ring gear so that they rotate together; a second clutch (KU2) arranged to connect the first planetary gear carrier (P1) to the second ring gear so that they rotate together; a second brake (BR2) arranged to selectively stop rotation of the second ring gear (H2); and one or more control units which are configured to release the first / second brakes (BR1, BR2) and the first / second clutches (KU1, KU2), to determine whether the first brake (BR1) should be applied or the second clutch (KU2) should be applied, to prepare the transmission to be shifted into a drive or reverse (R) position, and to control the drive (A), the first motor / generator (MG1), and the second motor / generator (MG2) such that the second ring gear (H2) is not rotated when the first brake (BR1) is to be applied, wherein a rotational speed of the first motor / generator (MG1) is controlled by calculating a target rotational speed of the first motor / generator (MG1), wherein a first calculation is used by the controller to calculate the target rotational speed of the first motor / generator (MG1) when an output rotational speed is greater than a predetermined value is,and a second calculation is used by the controller to calculate the target speed of the first motor / generator (MG1) when the output speed is less than or equal to the predetermined value. [11] The system of claim 10, wherein the one or more control devices are configured to control the drive (A), the first motor / generator (MG1) and the second motor / generator (MG2) such that an output speed of the drive (A) is equal to a steady-state speed of the second ring gear (H2) if it is determined that the second clutch (KU2) is to be actuated.

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