DE102020212775A1 - Method for operating a motor vehicle drive train - Google Patents

Abstract

Method for operating a motor vehicle drive train, the drive train having an internal combustion engine (VM), a first electrical machine (EM) and a transmission (G) with a pump (P), the first electrical machine (EM) having the internal combustion engine ( VM) is connected or connectable, wherein the pump (P) can be driven by means of the first electric machine (EM) and by means of a second electric machine (EM2), wherein a drive shaft (P1) of the pump (P), the first electric machine ( EM) and the second electrical machine (EM2) are each connected to an element (E1, E2, E3) of a planetary gear set (RS), wherein when there is a request to start the internal combustion engine (VM) using the first electrical machine (EM), the second electric machine (EM2) is operated to drive the pump (P); and electronic control unit (ECU) or pump drive unit (PU) with an electronic control unit (ECU) for carrying out such a method, and motor vehicle transmission (G) with such a pump drive unit (PU).

Description

The invention relates to a method for operating a motor vehicle drive train. The invention also relates to an electronic control unit for carrying out such a method, a pump drive unit with an electronic control unit and a motor vehicle transmission with such a pump drive unit.

From the DE 10 2018 206 287 A1 a method for operating a motor vehicle drive train is known, which according to in 4 illustrated embodiment can be designed as a hybrid drive with an internal combustion engine and an electric machine. A transmission of this drive train has an oil pump for supplying hydraulic consumers of the transmission. A drive shaft of the oil pump, the electric machine and an electric motor are each connected to a member of a planetary gear set. In such a drive train, the internal combustion engine can be started by means of the electric machine.

The torque required to start the internal combustion engine depends on environmental influences. For example, the torque required at low temperatures is significantly greater than at higher temperatures. The existing crankshaft angle of the stationary combustion engine also has an influence on its starting torque. In order to be able to reliably start the internal combustion engine under all these operating conditions, the electric machine and its power supply must be powerful enough. This is usually ensured by a correspondingly large electrical machine and by a battery with a correspondingly large capacity. However, the overall weight of the motor vehicle increases due to the enlargement of the electric machine and battery. This is undesirable.

It is therefore the object of the invention to provide a method by means of which the most efficient possible starting process of the internal combustion engine can be achieved.

The object is achieved by the features of patent claim 1. Further solutions are given by an electronic control unit with the features of patent claim 10, by a pump drive unit with the features of patent claim 11, and by a motor vehicle transmission with the features of patent claim 13. Advantageous configurations emerge from the dependent claims, the description and the figures.

To solve the problem, a method for operating a motor vehicle drive train is proposed, which has an internal combustion engine, a first electrical machine and a transmission with a pump for supplying pressure to hydraulic consumers of the transmission. The first electric machine is either permanently connected to the internal combustion engine or can be connected in a switchable manner via a clutch, so that the internal combustion engine can be started by operating the electric machine.

The pump of the transmission can be driven by means of the electric machine and by means of a second electric machine. For this purpose, a drive shaft of the pump, the first electrical machine and the second electrical machine are each connected to an element of a planetary gear set. The planetary gear set is set up to sum up the drive power of the first and second electric machines and to transmit it to the drive shaft of the pump.

If there is now a request to start the internal combustion engine using the first electric machine, the second electric machine is operated according to the invention in order to drive the pump.

The invention is based on the idea of using the torque of the first electrical machine in the best possible way for starting the internal combustion engine. In order to achieve this goal, the power consumption of other elements that are also driven by the first electric machine should be minimized. This goal is achieved by the procedure according to the invention, because by driving the pump using the second electrical machine, the absorption torque of the pump has to be applied at least partially by the first electrical machine.

The second electric machine is preferably deactivated again after the internal combustion engine has been started successfully or after a defined period of time has elapsed. This avoids unnecessary further operation of the second electrical machine.

When the internal combustion engine start request is present, the second electrical machine is preferably operated as a function of a temperature value of the internal combustion engine and/or the transmission. In this case, the second electrical machine is preferably operated when the temperature value is less than a limit value. This avoids unnecessary operation of the second electrical machine. Because at higher temperatures, the torque required to start the combustion engine is less than at low temperatures, so that the first electric machine can reliably start the combustion engine even without additional measures. The temperature value is preferably determined using the oil temperature of the transmission, since a sensor for measuring the transmission oil temperature is usually present anyway.

When the internal combustion engine start request is present, the second electric machine is preferably operated as a function of a power value of the electric machine, which is determined, for example, on the basis of a charge state of a battery. The battery supplies electric power to the first electric machine. If the battery state of charge is less than a limit value, the maximum possible torque of the first electric machine is potentially not available. By operating the second electrical machine, the torque available from the first electrical machine can be used in the best possible way for starting the internal combustion engine.

If the second electrical machine is to be operated when the internal combustion engine start request is present, a target speed or a target speed gradient is preferably specified for the second electrical machine.

As a further solution to the problem, an electronic control unit is proposed which is set up to carry out the method described in the introduction. The electronic control unit is preferably assigned directly to the second electrical machine and controls the operation of the second electrical machine.

A pump drive unit for a motor vehicle is proposed as a further solution to the problem. The pump drive unit has an electric machine with an output shaft, a sensor for determining a speed of the output shaft, and an electronic control unit. The electronic control unit is set up to control the electric machine based on a signal from the sensor and at least one other signal, for example based on a setpoint speed of the electric machine. The electronic control unit is set up to carry out the method described above. The pump drive unit can have a freewheel between the output shaft and a non-rotatable element of the pump drive unit.

The pump drive unit can be part of a motor vehicle transmission. Such a motor vehicle transmission has a pump. The pump can be driven by a first drive source and a second drive source. For this purpose, a drive shaft of the pump, the first drive source and the second drive source are each connected to an element of a planetary gear set. The electric machine of the pump drive unit forms the second drive source of the pump.

The motor vehicle transmission preferably has a further electronic control unit which is set up to control functions of the transmission. For example, the additional electronic control unit controls the gear change actuators of the transmission. The additional electronic control unit is in communication with the electronic control unit of the pump drive unit, for example via an information bus. The electronic control unit of the pump drive unit controls the electric motor based on the signal from the sensor and at least the further signal, the electronic control unit of the pump drive unit receiving the further signal from the further electronic control unit.

The electric machine of the pump drive unit is preferably connected to a sun gear which forms a first of the planetary gear set elements. The drive shaft of the pump is connected to a planet carrier which forms a second of the planetary gear set members. The first power source drives a ring gear of the planetary gear set, which forms a third of the planetary gear set members.

• 1 bis 3 je eine schematische Ansicht eines Kraftfahrzeug-Antriebsstrangs; und
• 4a bis 4c verschieden Betriebszustände eines Planentenradsatzes, dargestellt als Drehzahlplan; und

Exemplary embodiments of the invention are described in detail with reference to the figures. Show it:

• 1 until 3 each a schematic view of a motor vehicle drive train; and
• 4a until 4c various operating states of a planetary gear set, shown as a speed plan; and

1 shows a schematic view of a motor vehicle drive train according to a first embodiment. The motor vehicle drive train has an internal combustion engine VM and a first electric machine EM connected to it for driving drive wheels DW of the motor vehicle. In order to adapt the speed and torque output characteristics of the internal combustion engine VM to the driving resistance of the motor vehicle, a transmission G is connected between the internal combustion engine VM and the drive wheels DW. The transmission G has an input shaft GW1, a gear wheel set GS and an output shaft GW2. The input shaft GW1 is connected to the internal combustion engine VM via a torsional vibration damper TD and a torque converter TC that can be bridged via a clutch WK. The output shaft GW2 is via a differential gear AG connected to the drive wheels DW. The gear wheel set GS is set up to provide different transmission ratios between the input shaft GW1 and the output shaft GW2. For example, in 1 not shown planetary gear sets and / or spur gears are used, which interact with switching elements for gear formation.

A hydraulic circuit is provided for lubricating and cooling components of the transmission G. If elements of the transmission G are actuated hydraulically, for example the clutch WK, then this hydraulic actuation also takes place through the hydraulic circuit. The hydraulic circuit has a pump P, which draws in oil from a tank T and feeds it to a hydraulic control unit HCU. In the hydraulic control unit HCU, the oil from the pump P is distributed to the various hydraulic consumers of the transmission G as required. An electronic control unit TCU is provided to control the hydraulic control unit HCU.

A drive shaft P1 of the pump is connected to a planet carrier E2 of a planetary gear set RS. A plurality of planet gears EP are rotatably mounted on the planet carrier E2. The planet gears EP mesh with a ring gear E3 and with a sun gear E1 of the planetary gear set RS. An external toothing formed on the ring gear E3 meshes with an intermediate gear ZR. The intermediate wheel ZR meshes with a toothing which is non-rotatably connected to an input side of the torque converter TC and thus to a rotor of the first electrical machine EM. The sun gear E1 is connected to an output shaft WX of a second electrical machine EM2, which is designed, for example, as a permanently excited brushless DC motor. A freewheel F is arranged between the output shaft WX and a non-rotatable element GX.

With such a structure, the pump P can be driven both by the internal combustion engine VM and/or by the first electric machine EM as the first drive source and by the second electric machine EM2 as the second drive source. If the pump P is to be driven by the second electric machine EM2, the electronic control unit TCU transmits a corresponding command to an electronic control unit ECU controlling the second electric machine EM2, for example a setpoint speed of the second electric machine EM2. The electronic control unit ECU is assigned a speed sensor RLS, which determines the direction of rotation and speed of the output shaft WX. The electronic control unit ECU controls the second electric machine EM2 to rotate in a first direction of rotation. In the first direction of rotation, the freewheel F is in its freewheeling position. By comparing the target speed with the actual speed of the output shaft WX determined by the speed sensor RLS, the electronic control unit ECU can regulate the speed of the output shaft WX. The electronic control unit ECU, the first electrical machine EM and the second electrical machine EM2 are supplied with power via a battery BAT, which is 1 is shown schematically.

2 shows a schematic view of a motor vehicle drive train according to a second embodiment, which essentially corresponds to that in 1 corresponds to the first embodiment shown. A separating clutch K0 is now arranged between the torsional vibration damper TD and the first electrical machine EM. By opening the separating clutch K0, the first electric machine EM can drive the motor vehicle without dragging the internal combustion engine VM with it. If the first electrical machine EM starts the internal combustion engine VM, the separating clutch K0 is closed. The separating clutch K0 can be actuated, for example, by the hydraulics of the transmission G or by its own electromechanical actuator.

3 shows a schematic view of a motor vehicle drive train according to a second embodiment, which essentially corresponds to that in 2 illustrated second embodiment corresponds. The torque converter and the lock-up clutch are omitted here, so that the first electrical machine EM is connected directly to the input shaft GW1.

If the internal combustion engine VM is now to be started by means of the first electrical machine EM, then the electrical machine EM also drives the pump P via the intermediate gear ZR and via the planetary gear set RS. The torque of the first electrical machine EM available for starting the internal combustion engine VM is thus reduced by the absorption torque of the pump P. In order to avoid this, the second electrical machine EM2 is operated when there is a request to start the internal combustion engine VM. This is illustrated by the illustrations 4a until 4c clarified.

4a until 4c each show a speed diagram of the planetary gearset RS. The speed diagram shows the speeds of the sun gear E1, the planet carrier E2 and the ring gear E3 in relation to each other. With a speed value n=0, the respective element stands still, i.e. has no speed. At a speed value n+, the respective element rotates in a first direction of rotation. at a speed value n-rotates the respective element in a second direction of rotation, which is opposite to the first direction of rotation. A speed of the pump drive shaft P1 connected to the planetary carrier E2 with a speed value n+ corresponds to pump operation in the delivery direction. A rotational speed of the pump drive shaft P1 connected to the planetary carrier E2 with a rotational speed value n− corresponds to pump operation in the opposite direction to the pumping direction.

If there is now a request to start the internal combustion engine VM using the first electric machine EM, the second electric machine EM2 is first driven in the first direction of rotation. The internal combustion engine VM is still at a standstill, so that the ring gear E3 is not being driven. The moment of resistance of the internal combustion engine VM is - taking into account the supporting factors of the planetary gear set RS - higher than the moment of resistance of the pump P. Torque is thus transmitted from the second electrical machine EM2 to the pump drive shaft P1. This state is in 4a shown.

The internal combustion engine VM is then started by means of the first electrical machine EM, so that a speed in the first direction of rotation is also set at the ring gear E3. Such a state is in 4b shown. The pump P is now driven by joint operation of the first electrical machine EM and the second electrical machine EM2. As a result, at least part of the absorption torque of the pump P is made available by the second electric machine EM2, and the difference is now also available for starting the internal combustion engine VM using the first electric machine EM.

If the start of the internal combustion engine VM is complete or if a defined period of time has elapsed, the second electrical machine EM2 is deactivated again. The pump P is now driven solely by the internal combustion engine VM, optionally in combination with the first electrical machine EM. This state is in 4c shown. The support torque at the sun gear E1 is provided by the freewheel F.

The operation of the second electrical machine EM2 during the starting process of the internal combustion engine VM does not have to take place under all operating conditions. For example, the operation of the second electric machine EM2 can stop if a temperature value of the internal combustion engine VM or the transmission G is above a limit value. For this purpose, for example, the signal of a temperature sensor, which measures the temperature of the oil in the tank T, can be used. In addition or as an alternative to this, the operation of the second electric machine EM2 can be stopped if the state of charge of the battery BAT is high enough to ensure a reliable start of the internal combustion engine VM using the first electric machine EM.

Reference List

VM

combustion engine

Inc

differential gear

DW

drive wheel

G

transmission

GW1

input shaft

GW2

output shaft

GS

gear set

TD

torsional vibration damper

TC

torque converter

WK

coupling

EM

First electric machine

K0

disconnect clutch

TCU

Electronic control unit

HCU

Hydraulic control unit

T

tank

P

pump

P1

Drive shaft of the pump

ZR

intermediate wheel

RS

planetary gear set

E1

sun gear

E2

planet carrier

E3

ring gear

EP

planet wheel

PU

pump drive unit

EM2

Second electric machine

WX

output shaft

GX

Non-rotating element

f

freewheel

RLS

sensor

BAT

battery

n

speed value

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018206287 A1 [0002]

Claims (15)

Method for operating a motor vehicle drive train, the drive train having an internal combustion engine (VM), a first electric machine (EM) and a transmission (G) with a pump (P) for supplying pressure to hydraulic consumers of the transmission (G), - wherein the first electrical machine (EM) is connected or can be connected to the internal combustion engine (VM), so that the internal combustion engine (VM) can be started by operating the first electrical machine (EM), - the pump (P) using the first electrical machine ( EM) and can be driven by means of a second electrical machine (EM2), a drive shaft (P1) of the pump (P), the first electrical machine (EM) and the second electrical machine (EM2) each having an element (E1, E2, E3) of a planetary gear set (RS) are connected, characterized in that when there is a request to start the internal combustion engine (VM) by means of the first electric machine (EM), the second electric M machine (EM2) is operated to drive the pump (P). procedure after claim 1 , characterized in that the second electrical machine (EM2) is deactivated again after the internal combustion engine (VM) has been successfully started or after a defined period of time has elapsed. procedure after claim 1 or claim 2 , characterized in that when there is a request to start the internal combustion engine (VM) by means of the first electrical machine (EM), the second electrical machine (EM2) is operated depending on a temperature value of the internal combustion engine (VM) and/or the transmission (G). . procedure after claim 3 , characterized in that the second electrical machine (EM2) is then operated when the request to start the internal combustion engine (VM) is present when the temperature value is less than a limit value. procedure after claim 3 or claim 4 , characterized in that the temperature value is determined based on an oil temperature of the transmission (G). Procedure according to one of Claims 1 until 5 , characterized in that when there is a request to start the internal combustion engine (VM) by means of the first electrical machine (EM), the second electrical machine (EM2) is operated depending on an available power value of the electrical machine (EM). procedure after claim 6 , characterized in that the second electrical machine (EM2) is then operated when the requirement to start the internal combustion engine (VM) is present when the power value of the electrical machine (EM) is less than a limit value. procedure after claim 6 or claim 7 , characterized in that the power value of the electrical machine (EM) is determined based on a state of charge of a battery (BAT) which supplies the first electrical machine (EM) with electrical power. Method according to one of the preceding claims, characterized in that when there is a request to start the internal combustion engine (VM) using the electric machine (EM), the second electric machine (EM2) is operated by specifying a target speed or a target speed gradient. Electronic control unit (ECU), characterized in that the electronic control unit (ECU) for carrying out the method according to one of Claims 1 until 9 is set up. Pump drive unit (PU) for a motor vehicle, the pump drive unit (PU) having an electric machine (EM2) with an output shaft (WX), a sensor (RLS) for determining the speed of the output shaft (WX) and an electronic control unit (ECU), the Electronic control unit (ECU) is set up to control the electric machine (EM2) based on a signal from the sensor (RLS) and at least one further signal, characterized in that the electronic control unit (ECU) for carrying out the method according to one of Claims 1 until 9 is set up. Pump drive unit (PU) after claim 11 , Characterized by a freewheel (F) between the output shaft (WX) and a non-rotatable element (GX) of the pump drive unit (PU). Motor vehicle transmission (G) with a pump (P) for supplying oil to hydraulic consumers of the motor vehicle transmission (G), a drive shaft (P1) of the pump (P) being drivable by means of a first drive source (VM, EM) and by means of a second drive source (EM2). is, wherein the drive shaft (P1) of the pump (P), the first drive source (VM, EM) and the second drive source (EM2) each having an element (E1, E2, E3) of a planetary gear set (RS) are connected, characterized that the motor vehicle gear (G) after a pump drive unit (PU). claim 11 or after claim 12 for driving the pump (P), wherein the second drive source is formed by the electric machine (EM2) of the pump drive unit (PU). Motor vehicle transmission (G) after Claim 13 , characterized in that the motor vehicle transmission (G) has a further electronic control unit (TCU) which is set up to control functions of the motor vehicle transmission (G), the further electronic control unit (TCU) being connected to the electronic control unit (ECU) of the pump drive unit ( PU) is in communication, with the electronic control unit (ECU) of the pump drive unit (PU) being set up to control the electric motor (EM2) based on the signal from the sensor (RLS) and at least the other signal, with the electronic control unit (ECU) of the Pump drive unit (PU) receives the further signal from the further electronic control unit (TCU). Motor vehicle transmission (G) after Claim 13 or Claim 14 characterized in that - a first of the elements (E1) of the planetary gear set (RS) is a sun gear and is connected to the output shaft (WX) of the electric machine (EM2) of the pump drive unit (PU), - a second of the elements (E2) of the planetary gear set (RS) is a planet carrier and is connected to the drive shaft (P1) of the pump (P), and - a third of the elements (E3) of the planetary gear set (RS) being a ring gear and driven by the first drive source (VM, EM ) is drivable.

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