DRIVE AND METHOD FOR OPERATING A DRIVE

Description

[0001] The invention relates to a drive and a method for operating a drive.

[0002] It is generally known that a transmission has a gear ratio. For example, a planetary gear has a high gear ratio.

[0003] A hybrid transmission high-voltage connection is known from DE 10 2019 114 810 A1.

[0004] A drive train with variable input and constant output speed is known from DE 103 18 696 A1.

[0005] A hybrid vehicle is known from DE 695 16 129 T2.

[0006] A control strategy for electromechanically power-splitting hybrid drives is known from DE 103 33 931 A1.

[0007] A power transmission system for a hybrid vehicle is known from DE 698 35 174 T2.

[0008] From DE 103 18 696 A1, the closest prior art is a drive train with variable input and constant output speed.

[0009] A hybrid vehicle is known from DE 695 16 129 T2.

[0010] A control strategy for electromechanical power-splitting hybrid drives is known from DE 103 33 931 A1.

[0011] A power transmission system for a hybrid vehicle is known from DE 698 35 174 T2.

[0012] An integrated power train is known from US 2012 / 157255 A1.

[0013] From US 2005 / 119083 A1 is a hybrid system with a controllable speed.

[0014] An electromechanical drive system is known from CN 106 560 336 A.

[0015] The invention is therefore based on the object of developing a drive in which the gear ratio is controllable.

[0016] According to the invention, the object is achieved with the drive according to the features specified in the claim and with the method according to the features specified in claim 12 or 14.

[0017] Important features of the invention in the drive are that the drive is provided for power transmission from an input shaft, in particular planetary carrier, to an output shaft,

[0018] wherein a part of the power to be transmitted is supplied from the input shaft to a generator-operated first electric motor and converted into electrical power, which is at least partially supplied to a motor-operated second electric motor, the mechanical power of which is supplied to the output shaft, wherein the first electric motor feeds an AC-side terminal of a first inverter, the DC-side terminal of which feeds a DC-side terminal of a second inverter, the AC-side terminal of which feeds the second electric motor, in particular wherein the first electric motor has an electromagnetically actuated holding brake, the activation of which makes the part vanishingly small and the deactivation of which makes the part controllable by the inverter, the remaining portion of the power to be transmitted being transmitted from the input shaft to the output shaft via a mechanical gear, in particular a planetary gear.

[0019] An advantage is that when the holding brake is engaged, no power is conducted via the electrical path. However, when the holding brake is disengaged, the power conducted via the electrical path can be regulated by appropriately controlling the inverter. In particular, the overall transmission ratio of the drive can be controlled, particularly between zero and a value that is greater than the transmission ratio achievable via the purely mechanical path, in particular via the gearbox.

[0020] Important features of the invention in the drive are that the drive has: a rotatably mounted planetary carrier, in particular which is connected in a rotationally fixed manner to a drive shaft, planetary gears which are rotatably mounted on bolts connected to the planetary carrier, a ring gear which has an internal toothing and an external toothing, a rotatably mounted sun gear and a first gear which is in engagement with the external toothing of the ring gear, wherein the first gear is connected in a rotationally fixed manner to the rotor shaft of a first electric motor, in particular a synchronous motor, in particular a synchronous motor designed as a three-phase motor, wherein the drive has a second gear which is in engagement with a toothed part, in particular with a third gear, wherein the second gear is connected in a rotationally fixed manner to the rotor shaft of a second electric motor, in particular a synchronous motor, in particular a synchronous motor designed as a three-phase motor, wherein the toothed part is connected in a rotationally fixed manner to the sun gear.

[0021] The advantage here is that a mechanical and an electrical power transmission path are designed in parallel. This is because part of the power is transmitted from the ring gear to the first electric motor, which is operated as a generator. The electrical power thus provided is fed to the output shaft of the drive via the second electric motor. Thus, a power path mechanically transmitted by the planetary gear is connected in parallel with an electrical power path that can be controlled by the inverter. In this way, the power portion transmitted via the electrical path can also be used to control or regulate a transmission ratio, i.e. the quotient of the speed of the output shaft and the speed of the planet carrier.If only the constant gear ratio generated by the mechanical path, i.e. the planetary gear, is desired, the drive can be operated purely mechanically, in particular like a planetary gear with a fixed ring gear, by activating the brake of the first electric motor and deactivating, in particular activating the de-energized state, the second electric motor. However, if a different gear ratio is desired, this first electric motor can be operated as a generator in controlled mode by releasing the brake of the first electric motor, and the power generated by the generator can be fed to the output shaft in a controlled manner via the second electric motor in motor mode. Instead of a specific gear ratio, however, a time-dependent curve, i.e. a temporal sequence of different gear ratios, can also be specified.

[0022] In an advantageous embodiment, the first electric motor is powered by the AC voltage connection of a first inverter, whose DC voltage connection is electrically connected, in particular in parallel, to the DC voltage connection of a second inverter, whose AC voltage connection feeds the second electric motor. The advantage here is that the power to be absorbed by the generator is controllable, in particular by controlling the speed of the input shaft, in particular of the planetary carrier, towards a target value and determining the associated torque according to the power to be transmitted in the electrical path. This power is supplied to the output shaft by applying a torque such that the speed of the output shaft is brought to the desired overall transmission ratio of the drive. Alternatively, this can also be achieved via a voltage regulator.

[0023] In an advantageous embodiment, the control signals for the first inverter are generated by a first signal electronics unit. The advantage here is that the first inverter determines the regeneratively controlled operation of the first motor.

[0024] In an advantageous embodiment, the control signals for the second inverter are generated by a second signal electronics unit. This is advantageous because the second inverter determines the controlled regenerative operation of the first motor. If an energy storage device is interposed between the first and second inverters, the regenerative and motor power do not have to be the same, but may differ from each other. Thus, control deviations do not cause the drive to oscillate. The control quality is thus improved.

[0025] In an advantageous embodiment, the first signal electronics comprises a speed controller, in particular a first linear controller, in particular a P controller or PI controller, whose manipulated variable is a particularly regenerative torque of the first electric motor. This is advantageous because it can be implemented simply.

[0026] In an advantageous embodiment, the second signal electronics unit comprises a second linear controller whose manipulated variable is, in particular, a motor torque of the second electric motor. This is advantageous because it can be implemented simply.

[0027] In an advantageous embodiment, a first sensor for detecting the rotational speed of the first gearwheel is connected to the first signal electronics, in particular a sensor for detecting the voltage applied to the DC-side terminal of the first inverter, and / or a second sensor for detecting the rotational speed of the second gearwheel is connected to the second signal electronics, as is a sensor for detecting the voltage applied to the DC-side terminal of the second inverter. It is advantageous that the motors can be designed as synchronous motors, each with a speed sensor.

[0028] In an advantageous embodiment, a first sensor for detecting the output current at the AC-side terminal of the first inverter is connected to the first signal electronics unit, and / or a second sensor for detecting the output current at the AC-side terminal of the second inverter is connected to the second signal electronics unit. Advantageously, the motor currents are detected.

[0029] In an advantageous embodiment, the first signal electronics unit includes a device for detecting the voltage present at the DC-side terminal of the first or second inverter. This is advantageous in that pulse-width modulated operation of the controllable semiconductor switches of the inverters is possible, with the pulse width being determined depending on the DC voltage available to the respective inverter. Thus, in the event of fluctuating intermediate circuit voltage, a well-defined AC voltage can be generated at the AC-side terminal of the second inverter.

[0030] In an advantageous embodiment, an energy storage device is electrically connected in parallel to the DC-side terminals of the first and second inverters. This is advantageous because power fluctuations caused by control deviations can be buffered. With a large energy storage capacity, even different control strategies can be applied to the two inverters. For example, after starting, a smaller power flow can initially be supplied to the output shaft by the motor than from the first motor to the energy storage device. Thus, the speed can initially be accelerated more slowly than would be possible with full power transmission.

[0031] In an advantageous embodiment, the energy storage device comprises an accumulator and / or a double-layer capacitor, in particular an ultracapacitor. This is advantageous because a large buffer energy can be provided.

[0032] In an advantageous embodiment, the first electric motor is designed as a synchronous motor. This is advantageous in that a high torque can be generated and / or efficient regenerative operation can be carried out.

[0033] In an advantageous embodiment, the second electric motor is designed as a synchronous motor. This is advantageous in that a high torque can be generated and / or efficient motor operation can be carried out.

[0034] Important features in the method for operating a drive are that the torque of the first electric motor, in particular the motor current of the first electric motor, in particular the motor voltage of the first electric motor, is set such that the speed n1_actual of the rotor shaft of the first electric motor is detected and regulated to a setpoint value n1_setpoint, in particular by means of the first inverter, wherein the torque of the second electric motor, in particular the motor current of the second electric motor, in particular the motor voltage of the second electric motor, is set such that the detected voltage U_z_actual present at the DC voltage side connection of the second inverter is regulated to a setpoint value U_z_setpoint, in particular by means of the second inverter.

[0035] The advantage here is that the generator-controlled motor tries to increase the voltage and the motor-controlled motor tries to reduce the voltage, whereby limiting the voltage can also be carried out in a simple manner.

[0036] In an advantageous embodiment, the target value n1_Soll is determined from the speed n2_ist detected on the rotor shaft of the second electric motor, taking into account a predetermined gear ratio and a predetermined split ratio, in particular wherein the gear ratio equals the desired value of the quotient of the speed of the sun gear shaft and the speed of the planet carrier or the desired value of the quotient of the speed of the rotor shaft of the second electric motor and the speed of the first electric motor. It is advantageous that the target speed of the first motor is determined from the actual value of the speed of the output shaft, thus taking into account the desired gear ratio for the electrical path.

[0037] Important features in the method for operating a drive according to claim 13 are that the torque of the first electric motor, in particular the motor current of the first electric motor, in particular the motor voltage of the first electric motor, is set such that the speed n1_actual of the rotor shaft of the first electric motor is detected and regulated to a setpoint n1_setpoint, in particular by means of the first inverter, wherein the torque of the second electric motor, in particular the motor current of the second electric motor, in particular the motor voltage of the second electric motor, is set such that the speed n2_actual of the rotor shaft of the second electric motor is detected and regulated to a setpoint n2_setpoint, in particular by means of the second inverter, wherein the setpoint n2_setpoint is determined from the detected speed n1_actual of the rotor shaft of the first electric motor, taking into account a predetermined gear ratio and a predetermined division of the gear ratio for the electrical and mechanical branch of the drive.

[0038] The advantage here is that the speed setpoint of the first motor is aligned with the actual speed of the output shaft and both motors can be operated with speed control, i.e. they are operated with similar controller structures.

[0039] In an advantageous embodiment, the gear ratio of the drive is specified as a monotonically increasing function of time, and when a target value is reached, the holding brake of the first motor is activated; in particular, the holding brake is applied, whereby the gear ratio of the drive, with the ring gear fixed, equals the target value. The advantage here is that, to start the drive, the brake is released and the ring gear can thus rotate. Furthermore, during start-up, not only is the speed of the output shaft increased, but also the gear ratio of the drive from a low value, for example, zero, to the target value, which equals the gear ratio of the purely mechanical path, in particular of the gearbox.

[0040] The invention will now be explained in more detail using a schematic illustration: In the Figure 1 A drive according to the invention is shown schematically.

[0041] As in Figure 1As shown, a torque source 1, in particular an electric motor, drives a rotatably mounted planet carrier 2 of the drive.

[0042] The planet carrier 2 is connected to bolts aligned parallel to the axis of rotation of the planet carrier 2, on which planet gears 4 are rotatably mounted, in particular via needle bearings or other rolling bearings.

[0043] The planetary gears 4, which are preferably evenly spaced from one another in the circumferential direction, are in engagement on the one hand with a centrally arranged sun gear 5 and on the other hand with a rotatably mounted ring gear 3 which radially surrounds the planetary gears 4.

[0044] The ring gear 3 not only has an internal toothing which engages with the external toothing of the planet gears 4, wherein the external toothing of the planet gears 4 engages with the external toothing of the sun gear 5, but the ring gear 3 also has an external toothing which engages with the external toothing of a first gear 6.

[0045] This first gear 6 is rotatably mounted and rotationally fixedly connected to the rotor shaft of a first electric motor, in particular a synchronous motor, which can be fed by an inverter 7. During generator operation, torque is transmitted from the ring gear 3 to the first gear 6, and thus, depending on the speed of the first gear 6, electrical power is transmitted from the first electric motor to the inverter.

[0046] The AC voltage side connection of the inverter 7 is connected to the connection of the electric motor, in particular to the stator of the first electric motor.

[0047] The DC voltage connection of inverter 7 is connected to the DC voltage connection of a second inverter 9, whose AC voltage connection is connected to the connection of a second electric motor, in particular a synchronous motor. This second electric motor directly drives a second gear 10, which meshes with a toothed part 11, in particular a third gear, which is rotationally fixedly connected to the shaft 12 that is rotationally fixedly connected to the sun gear 5, in particular to the output shaft of the planetary gear. Thus, the sun gear 5 is rotationally fixedly connected to the toothed part 11.

[0048] The connection of the DC voltage side terminals of the two inverters (7, 9) can be designated as intermediate circuit 8, whereby an upper potential of this DC voltage and a lower potential of this DC voltage, i.e. intermediate circuit voltage, is provided.

[0049] Optionally, an energy storage device can be added to this intermediate circuit 8 so that a quantity of energy generated by a generator can be stored in the energy storage device, in particular used as buffer energy.

[0050] The first inverter 7 has a means for detecting the motor current, i.e. the output current to the first electric motor, whose rotor shaft is connected in a rotationally fixed manner to the first gear 6.

[0051] A gear ratio is specified to operate the drive. To achieve this, the first inverter operates in speed control. The detected speed n1_actual of the first gear 6 is regulated to a setpoint n1_setpoint by setting a torque M1. The torque is regenerative, i.e., has a negative value.

[0052] The actual value U_z_Ist of the intermediate circuit voltage is recorded and regulated by the second inverter 9 to a setpoint U_z_Soll by applying a torque M2 via the second motor to the second gear 10 as a manipulated variable.

[0053] The setpoint U_z_Soll is set as low as possible, for example 100 volts.

[0054] The power supplied by the generator tries to increase the intermediate circuit voltage, which is limited to a maximum value U_z_max, for example to 650 volts or a value between 650 volts and 800 volts.

[0055] Thus, the first inverter 7 tends to increase the intermediate circuit voltage, while the second inverter 9 tends to decrease it. Ideally, the intermediate circuit voltage initially remains at a medium value, but after the brake of the first electric motor is activated, i.e., applied, the intermediate circuit voltage reaches a vanishingly small value, in particular zero.

[0056] By providing a capacitance in the intermediate circuit 8, in particular by providing an energy storage device in the intermediate circuit 8, control fluctuations of the first inverter 7 have less influence on the control behavior of the second inverter and the tendency of the entire system to oscillate is reduced.

[0057] The speed controller of the first inverter 7 is preferably designed as a linear controller, such as a P controller or PI controller. The controller of the second inverter 9 is preferably also designed as a linear controller, such as a P controller or PI controller.

[0058] Thus, only one speed measurement on the first electric motor and one measurement of the intermediate circuit voltage as well as the measurement of the output currents of the two inverters (7, 9) at their respective AC-side connections are necessary. In addition, a speed measurement on the second electric motor is helpful to generate the most well-adapted rotating field possible.

[0059] The first electric motor is preferably designed as a three-phase motor and the second electric motor is also designed as a three-phase motor.

[0060] The respective inverter (7, 9) comprises a parallel circuit of three series circuits fed from the intermediate circuit voltage, each of the series circuits comprising two controllable semiconductor switches, in particular IGBTs or MOSFETs, connected in series. In this way, a three-phase voltage can be provided at the AC-side terminal of the respective inverter.

[0061] The control voltages for the semiconductor switches are generated by signal electronics, which preferably consists of a first part, which is arranged in a housing with the first inverter 7, and a second part, which is arranged in a housing with the second inverter 9. The two parts are connected via a data exchange connection. The first part contains the speed controller, and the second part the voltage controller, with both controllers each having a torque as a manipulated variable.

[0062] The sun gear 5 is arranged radially inside the planet gears 4, which in turn are arranged radially inside the ring gear 3.

[0063] In further embodiments according to the invention, a different controller structure is used. Here, both inverters 7 and 9 are each operated in speed control, and a desired gear ratio is specified for the electrical branch. The speed n1_actual detected at the first electric motor is controlled to a predetermined target speed curve n1_target (t) by setting a torque M1 and thus transmitting it to the first gear 6 via the first electric motor. The second inverter receives, as target speed n2, a value dependent on the detected speed n1_actual and controls the detected speed n2_actual of the geared part 11 to this target speed n2 by setting a corresponding torque M2. The target speed is preferably determined as the sum of the speed of the planet carrier 2, multiplied by the mechanical gear ratio and detected by a speed sensor, and the additional speed generated via the electrical path.

[0064] In further embodiments according to the invention, instead of a constant value for the gear ratio, in particular the gear ratio, a temporal progression of the gear ratio is specified. In particular, for starting a drive, during acceleration from zero speed until the target speed is reached, the gear ratio increases from zero to a value that corresponds to the purely mechanical gear ratio of the planetary gear, i.e., the gear ratio that is achieved when the brake of the first motor is activated, i.e., fixing the ring gear 3, when the second motor is deactivated. Thus, the brake is only activated, and thus the ring gear 3 is only fixed, when the gear ratio has reached the value that can be achieved purely mechanically by the planetary gear. List of reference symbols

[0065] 1 Torque source, in particular electric motor 2 Planet carrier 3 Ring gear 4 Planet gear 5 Sun gear 6 First gear 7 Inverter, in particular generator-operated inverter 8 Intermediate circuit 9 Inverter, in particular motor-operated inverter 10 Second gear 11 Geared part, in particular third gear 12 Shaft, in particular output shaft

Claims

1. A drive, having - a rotatably mounted pinion cage (2), in particular which is connected non-rotatably to a drive shaft, - planet gears which are rotatably mounted on bolts connected to the pinion cage (2), - a ring gear (3) which has internal gearing and external gearing, - a rotatably mounted sun gear (5) and - a first gear wheel (6) which meshes with the external gearing of the ring gear (3), characterised in that the first gear wheel (6) is connected non-rotatably to the rotor shaft of a first electric motor, in particular synchronous motor, in particular of a synchronous motor embodied as a three-phase motor, with the drive having a second gear wheel (10) which meshes with a toothed part (11), in particular with a third gear wheel, with the second gear wheel (10) being connected non-rotatably to the rotor shaft of a second electric motor, in particular synchronous motor, in particular of a synchronous motor embodied as a three-phase motor, with the toothed part (11) being connected non-rotatably to the sun gear (5).

2. A drive according to claim 1, characterised in that the first electric motor is fed from the AC-voltage-side connector of a first inverter (7), the DC-voltage-side connector of which is connected electrically, in particular in parallel, to the DC-voltage-side connector of a second inverter (10), the AC-voltage-side connector of which feeds the second electric motor.

3. A drive according to one of the preceding claims, characterised in that the activation signals for the first inverter (7) are generated by first signal electronics and in that the activation signals for the second inverter are generated by second signal electronics.

4. A drive according to one of the preceding claims, characterised in that the first signal electronics have a speed controller, in particular a first linear controller, in particular P controller or PI controller, the controlled variable of which is an in particular generator-mode torque of the first electric motor.

5. A drive according to one of the preceding claims, characterised in that the second signal electronics have a second linear controller, the controlled variable of which is an in particular motor-mode torque of the second electric motor.

6. A drive according to one of the preceding claims, characterised in that to the first signal electronics there is connected a first sensor for detecting the speed of rotation of the first gear wheel (6), in particular and a sensor for detecting the voltage applied to the DC-voltage-side connector of the first inverter (7), and / or in that to the second signal electronics there is connected a second sensor for detecting the speed of rotation of the second gear wheel (10) and a sensor for detecting the voltage applied to the DC-voltage-side connector of the second inverter (10).

7. A drive according to one of the preceding claims, characterised in that to the first signal electronics there is connected a first sensor for detecting the output current at the AC-voltage-side connector of the first inverter (7), and / or in that to the second signal electronics there is connected a second sensor for detecting the output current at the AC-voltage-side connector of the second inverter (10).

8. A drive according to one of the preceding claims, characterised in that to the first signal electronics a for detecting the voltage applied to the DC-voltage-side connector of the first or second inverter (7, 10).

9. A drive according to one of the preceding claims, characterised in that an energy storage means is electrically connected in parallel to the DC-voltage-side connectors of the first and the second inverter (7, 10).

10. A drive according to one of the preceding claims, characterised in that the energy storage means has a storage battery and / or a double-layer capacitor, in particular ultracap.

11. A drive according to one of the preceding claims, characterised in that the first electric motor takes the form of a synchronous motor and / or in that the second electric motor takes the form of a synchronous motor.

12. A method for operating a drive, in particular according to one of the preceding claims, characterised in that the torque of the first electric motor, in particular the motor current of the first electric motor, in particular and the motor voltage of the first electric motor, is set such that the speed of rotation n1_actual of the rotor shaft of the first electric motor is detected and controlled to a setpoint value n1_setpoint, in particular by means of the first inverter (7), with the torque of the second electric motor, in particular the motor current of the second electric motor, in particular and the motor voltage of the second electric motor, being set such that the detected voltage U_z_actual applied to the DC-voltage-side connector of the second inverter (10) is controlled to a setpoint value U_z_setpoint, in particular by means of the second inverter (10).

13. A method according to claim 12, characterised in that the setpoint value n1_setpoint is determined from the speed of rotation n2_actual detected at the rotor shaft of the second electric motor, taking into account a specified transmission ratio and a specified split ratio, in particular with the transmission ratio being equal to the desired value of the quotient of the speed of rotation of the sun gear shaft and of the speed of rotation of the pinion cage (2), or to the desired value of the quotient of the speed of rotation of the rotor shaft of the second electric motor and of the speed of rotation of the first electric motor.

14. A method for operating a drive, in particular according to one of claims 1 to 12, characterised in that the torque of the first electric motor, in particular the motor current of the first electric motor, in particular and the motor voltage of the first electric motor, is set such that the speed of rotation n1_actual of the rotor shaft of the first electric motor is detected and controlled to a setpoint value n1_setpoint, in particular by means of the first inverter (7), with the torque of the second electric motor, in particular the motor current of the second electric motor, in particular and the motor voltage of the second electric motor, being set such that the speed of rotation n2_actual of the rotor shaft of the second electric motor is detected and controlled to a setpoint value n2_setpoint, in particular by means of the second inverter (10), with the setpoint value n2_setpoint being determined from the detected speed of rotation n1_actual of the rotor shaft of the first electric motor, taking into account a specified gear ratio number and a specified split of the gear ratio number for the electrical and mechanical branches of the drive.

15. A method according to one of the preceding claims, characterised in that the gear ratio number of the drive is specified as a monotonically increasing function of the time and when a target value is reached the holding brake of the first motor is activated, in particular is therefore applied, with the gear ratio number of the drive with ring gear (3) fixed being equal to the target value.