DE102020204284A1 - Method for operating a hybrid drive train for a motor vehicle - Google Patents

Abstract

A method for operating a hybrid drive train for a motor vehicle, the drive train having an internal combustion engine (VM) and an electric machine (EM) as drive sources for the motor vehicle, with a Separating clutch (K0) is arranged, the internal combustion engine (VM) and electrical machine (EM) acting alone or together mechanically on drive wheels (DW) of the motor vehicle, with the electrical machine (EM) driving the motor vehicle alone in a first purely electrical operating mode, while the separating clutch (K0) is open, with the separating clutch (K0) being closed in a second purely electrical operating mode, in which the electric machine (EM) alone drives the motor vehicle, as well as the electronic control unit (ECU) for carrying out such a method, as well as Motor vehicle with such a control unit (ECU).

Description

The invention relates to a method for operating a hybrid drive train for a motor vehicle. The invention also relates to an electronic control device for carrying out such a method, as well as a motor vehicle with such a control device.

Various variants of hybrid drive train configurations for motor vehicles are known in the prior art. In particular for plug-in hybrid vehicles, a parallel hybrid configuration is often used, in which the internal combustion engine and electrical machine can be connected to one another or decoupled from one another by a separating clutch. As a result, in the case of a purely electric drive of the motor vehicle, the internal combustion engine can be decoupled from the drive train so that its drag losses do not reduce the efficiency of the drive.

The patent application EP 2 666 689 A1 teaches a recuperation control for such a hybrid drive train. In this, the separating clutch is closed during a recuperation operation when the control calculates a fuel saving.

The patent application WO 2014/158826 A1 teaches a method for controlling the disconnect clutch in a hybrid drive during a recuperation operation. In this case, the separating clutch is opened when the fuel savings that can be achieved thereby are greater than the fuel consumption when the internal combustion engine is idling.

It is the object of the invention to expand the operating range of such a parallel hybrid drive train.

The object is achieved by the features of claim 1. Advantageous embodiments result from the dependent claims, the description and the figures.

To achieve the object, a method for operating a hybrid drive train for a motor vehicle is proposed. The drive train has an internal combustion engine and an electrical machine as drive sources for the motor vehicle. A separating clutch is arranged in the power flow between the internal combustion engine and the electrical machine. If the separating clutch is open, the electrical machine acts mechanically on the drive wheels of the motor vehicle; the combustion engine is decoupled from the drive train when the separating clutch is open. If the separating clutch is closed, the electric machine and the internal combustion engine work together on the drive wheels of the motor vehicle. The drive connection between the electric machine and the drive wheels can be interrupted, for example by a gear arranged between the electric machine and the drive wheels.

There are two different, purely electrical operating modes for operating the hybrid drive train. In a first purely electrical operating mode, the electrical machine alone drives the motor vehicle while the separating clutch is open. According to the invention, a second purely electrical operating mode is provided in which the electrical machine alone drives the motor vehicle while the separating clutch is closed.

Such an operating mode of the hybrid drive train, which at first glance is disadvantageous, has advantages in certain operating situations of the motor vehicle. Because by keeping the clutch closed during the purely electric drive, the time to start the internal combustion engine can be shortened, for example, since the internal combustion engine does not need to be dragged up to its starting speed. In addition, the torque potential of the electrical machine can be used in its entirety in the second, purely electrical operating mode, since no torque reserve needs to be kept for starting the internal combustion engine.

The internal combustion engine is preferably operated unfired in the second purely electrical operating mode. According to a further advantageous embodiment, inlet and outlet valves of the internal combustion engine are either permanently open or permanently closed in the second purely electrical operating mode at least when the motor vehicle is being driven by the electrical machine. Such an operation allows the drag losses of the unfired internal combustion engine to be reduced, since there are no gas exchange losses. In addition, the internal combustion engine can be started very easily from this mode of operation by resuming the opening and closing of the inlet and outlet valves and fuel being injected into the combustion chambers. There is no need to accelerate the internal combustion engine to its starting speed.

When the motor vehicle is decelerating or braking, the inlet and outlet valves are preferably activated in such a way that the drag losses of the internal combustion engine are increased. This method step is preferably used when a torque that can be generated by the electric machine as a generator is to be limited, for example when the battery is fully charged. This can For example, when driving downhill, the speed of the motor vehicle can also be maintained in a cruise control mode when the electric machine is no longer to output generator torque and when actuation of a service brake system of the motor vehicle is to be avoided. The method step can also be used when a maximum torque that can be generated by the electric machine as a generator is not sufficient to achieve or maintain a target deceleration or a target speed of the motor vehicle. In this way too, actuation of a service brake system can be avoided.

For clarification, it should be noted that the second purely electrical operating mode differs from an engine start operating mode or from an internal combustion engine shutdown mode. The second purely electrical operating mode is to be understood as a mode for electrically driving the motor vehicle, and is different from special operating states when changing between electrical and hybrid operation of the motor vehicle.

For example, the second purely electrical operating mode can be used when the motor vehicle is rolling with no load or with a very low load, especially when a speed of the motor vehicle reaches or falls below a limit value. As a result, the internal combustion engine can, if necessary, contribute to the drive of the motor vehicle again particularly quickly, since it does not need to be dragged up to its starting speed.

The motor vehicle is preferably operated in a stop-and-go mode in the second purely electrical operating mode, particularly preferably only when a temperature value of the internal combustion engine is less than a limit value. This warms up the internal combustion engine and prevents the internal combustion engine from cooling down. If the stop-and-go mode then changes back to normal driving mode, the internal combustion engine is up to operating temperature earlier. This has a positive effect on the emissions behavior of the internal combustion engine.

The motor vehicle is preferably operated in a purely electric sport mode in the second purely electric operating mode. Such a sport mode is also referred to as dynamic mode or performance mode. By selecting such a mode, the driver of the motor vehicle can request a particularly dynamic behavior of the drive. By operating in the second, purely electrical operating mode, the full capacity of the electrical machine is available, since no torque reserve has to be kept for starting the internal combustion engine. In addition, the internal combustion engine can be started very quickly from the second purely electrical operating mode, since the internal combustion engine does not need to be accelerated to its starting speed.

The motor vehicle is preferably operated in the second purely electrical operating mode when the motor vehicle is pulling a trailer. As a result, the full capacity of the electrical machine is available, since no torque reserve has to be kept for starting the internal combustion engine. If the target drive torque exceeds the maximum available torque of the electric machine, the internal combustion engine can be switched to a hybrid drive without delay.

The motor vehicle is preferably operated in crawling mode in the second purely electrical operating mode when a road gradient reaches or exceeds a limit value. As a result, the full capacity of the electrical machine is available, since no torque reserve has to be kept for starting the internal combustion engine. If the target drive torque exceeds the maximum available torque of the electric machine, the internal combustion engine can be switched to a hybrid drive without delay.

The motor vehicle is preferably operated in the second purely electrical operating mode when a change in the direction of travel of the motor vehicle is recognized or anticipated. As a result, the drive-side inertia is greater than in the first purely electrical operating mode, which makes it easier to brake the motor vehicle, which is required when changing direction of travel.

The motor vehicle is preferably operated in an off-road operating mode in the second purely electrical operating mode. Because in off-road operation, strong increases in road resistance can occur very suddenly. By operating in the second purely electrical operating mode, the efficiency of the electrical machine can be fully utilized in order to overcome such driving resistances. If the performance of the electrical machine is not sufficient, the combustion engine can be switched to a hybrid drive without delay.

The method is preferably carried out by an electronic control unit. The electronic control unit can be part of a motor vehicle.

• 1 bis 3 je einen Antriebsstrang eines Kraftfahrzeugs.

Embodiments of the invention are described in detail below. Show it:

• 1 until 3 one drive train each of a motor vehicle.

1 shows a schematic representation of a hybrid drive train for a motor vehicle. The hybrid powertrain has an internal combustion engine VM and an electric machine EM on. Between the internal combustion engine VM and the electric machine EM is a disconnect clutch K0 arranged. By means of the disconnect clutch K0 is a power flow between the internal combustion engine VM and the electric machine EM switchable. The hybrid drive train also includes a transmission G with a drive shaft GW1 and an output shaft GW2 . The output shaft GW2 is with a differential gear AG connected, via which the on the output shaft GW2 applied power to drive wheels DW of the motor vehicle is distributed. In the power flow between the electrical machine EM and the drive shaft GW1 is a torque converter TC arranged. The torque converter TC includes an impeller P. which with the electric machine EM connected is. A turbine wheel TR of the torque converter TC is with the drive shaft GW1 tied together. Impeller P. and turbine wheel TR work together hydrodynamically, so that power from the pump wheel P. hydrodynamically on the turbine wheel TR can be transferred. Impeller P. and turbine wheel TR are by closing a lock-up clutch WK mechanically connectable with each other.

The gear G is to show different gears between the drive shaft GW1 and the output shaft GW2 set up. Several shift elements are provided to form the gears. One of them is in 1 shown by way of example, and is in it as SCI designated. The switching elements, including the switching element SCI participate in 1 Planetary gear sets (not shown) together to the different gears between the drive shaft GW1 and output shaft GW2 to build. This is only to be regarded as an example. Instead of or in addition to the planetary gear sets, spur gear stages and / or one or more friction gears can be used, which are connected to the shifting elements, including the shifting element SCI work together to form a gait.

There is also an electronic control unit ECU intended. The control unit ECU stands with a converter INV in communication link, which of the electrical machine EM is assigned to their control. The control unit ECU also stands with the gearbox G in communication link. The gear G comprises an actuator for actuating the switching element SCI . The transmission also includes G also an actuator for actuating the lock-up clutch WK and an actuator for actuating the separating clutch K0 . This, too, is only to be regarded as an example. The disconnect clutch K0 could also be operated by an actuator which is independent of the gearbox G is. The same applies to the actuation of the lock-up clutch WK .

The lock-up clutch WK forms a torque-transmitting element between the electrical machine EM and the output shaft GW2 . If the lock-up clutch is operated in slip, a torque from the internal combustion engine can be generated VM and / or from the electrical machine EM to the drive wheels DW be transmitted without a fixed speed relationship between the output shaft GW2 and electric machine EM consists. The lock-up clutch WK can thus act as a starting element.

2 shows a schematic representation of a further hybrid drive train for a motor vehicle, which is essentially the same as in FIG 1 corresponds to the drive train shown. The torque converter is now omitted, so that the electric machine EM directly to the drive shaft GW1 connected is. Is the switching element SCI on the gear formation in the transmission G involved, so forms the switching element SCI a torque-transmitting element between the electrical machine EM and the output shaft GW2 . Will the switching element SCI operated in slip, a torque from the internal combustion engine VM and / or from the electrical machine EM to the drive wheels DW be transmitted without a fixed speed relationship between the output shaft GW2 and drive shaft GW1 consists. The switching element SCI can thus act as a starting element.

3 shows a schematic representation of a further hybrid drive train for a motor vehicle, which is essentially the same as in FIG 1 corresponds to the drive train shown. The torque converter is now omitted, so that the electric machine EM directly to the drive shaft GW1 connected is. The gear G is now listed as a dual clutch transmission, with the dual clutch through the clutches DC1 and DC2 is formed. Each of the clutches DC1 , DC2 is a clutch unit SK1 , SK2 assigned. Each of the clutch units SK1 , SK2 comprises at least two form-fitting couplings, which have an in 3 may have synchronizing unit, not shown. The clutch units are on the output side SK1 , SK2 with the output shaft GW2 tied together. Becomes one of the double clutches DC1 , DC2 operated in slip, a torque from the internal combustion engine VM and / or from the electrical machine EM to the drive wheels DW be transmitted without a fixed speed relationship between the output shaft GW2 and drive shaft GW1 consists. The clutches DC1 , DC2 can thus act as a starting element.

The hybrid powertrains according to 1 until 3 form so-called parallel hybrid drive trains. The internal combustion engine VM forms a first drive source of the drive train. The electric machine EM forms a second drive source of the drive train. Either of the two drive sources VM , EM can drive the drive wheels without operating the other drive source DW drive mechanically. The two sources of propulsion VM , EM can also put the drive wheels together DW drive so that the torques of the two drive sources VM , EM add. The motor vehicle is powered solely by the electric machine EM driven, there is a purely electrical operating mode.

The use of the method according to the invention is not limited to that according to 1 until 3 Drivetrains described are limited. For example, the method could also be used in a drive train without a shiftable transmission. Between at least one of the drive sources and the drive wheels DW a starting element can be arranged, for example a torque converter. Such a drive train can be used, for example, in a utility vehicle or in a rail vehicle.
According to the invention, a first and a second purely electrical operating mode are provided. In the first purely electric operating mode, the electric machine alone drives EM the drive wheels DW on, with the disconnect clutch K0 is open. In the first purely electric operating mode, the internal combustion engine can VM deactivated so that it comes to a standstill. By closing the disconnect clutch K0 can the internal combustion engine VM accelerated to its starting speed and then started.

In the second, all-electric operating mode, the electric machine alone drives EM the drive wheels DW on, with the disconnect clutch K0 closed is. This is the speed of the internal combustion engine VM depending on the speed of the electrical machine EM so that a crankshaft of the internal combustion engine VM is dragged along in the second purely electrical operating mode. This is where the internal combustion engine VM preferably operated unfired, so that in the combustion chambers of the internal combustion engine VM no fuel is injected. Preferably the in 1 inlet and outlet valves, not shown, of the internal combustion engine VM permanently open or permanently closed in the second purely electrical operating mode, so that no charge exchange losses occur.

Depending on the operating state of the motor vehicle, there are advantages to using the first purely electrical operating mode. If the motor vehicle is driving downhill, for example, the disconnect clutch should K0 preferably be open to as much energy as possible through a generator operation of the electrical machine EM to recuperate. The separating clutch should also be used to increase the range of the motor vehicle in purely electrical operation K0 to be open. Because for dragging along the combustion engine VM In the second, purely electrical operating mode, energy is required which is therefore not available to drive the motor vehicle.

Depending on the operating state of the motor vehicle, there are advantages to using the second purely electric operating mode, for example when the motor vehicle is in stop-and-go operation with a low internal combustion engine temperature, or in a purely electric sport driving mode, or when the motor vehicle is pulling a trailer, or in crawling mode on a steep road gradient, or in the event of a recognized or anticipated change of direction, or in an off-road operating mode of the motor vehicle.

List of reference symbols

VM

Internal combustion engine

G

transmission

GW1

drive shaft

GW2

Output shaft

K0

Disconnect clutch

EM

Electric machine

TC

Torque converter

P.

Impeller

TR

Turbine wheel

WK

Lock-up clutch

SCI

Switching element

DC1, DC2

coupling

SK1, SK2

Clutch unit

AG

Differential gear

DW

drive wheel

ECU

Control unit

INV

Converter

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed 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

• EP 2666689 A1 [0003]
• WO 2014/158826 A1 [0004]

Claims (16)

Method for operating a hybrid drive train for a motor vehicle, the drive train having an internal combustion engine (VM) and an electric machine (EM) as drive sources for the motor vehicle, - wherein in the power flow between the internal combustion engine (VM) and the electric machine (EM) a separating clutch (K0) is arranged, - the internal combustion engine (VM) and electrical machine (EM) acting alone or together mechanically on drive wheels (DW) of the motor vehicle, - wherein in a first purely electrical operating mode, only the electrical machine (EM) controls the motor vehicle drives while the separating clutch (K0) is open, characterized in that the separating clutch (K0) is closed in a second purely electrical operating mode in which the electric machine (EM) alone drives the motor vehicle. Procedure according to Claim 1 , characterized in that the internal combustion engine (VM) is operated unfired in the second purely electric operating mode. Procedure according to Claim 2 , characterized in that inlet and outlet valves of the internal combustion engine (VM) are either permanently open or permanently closed in the second purely electrical operating mode at least when the motor vehicle is driven by the electrical machine (EM). Procedure according to Claim 3 , characterized in that the inlet and outlet valves of the internal combustion engine (VM) are controlled during deceleration or braking of the motor vehicle in such a way that the drag losses of the internal combustion engine (VM) are increased if a. a torque that can be generated as a generator by the electrical machine (EM) is to be limited, or b. a maximum torque that can be generated by the electric machine (EM) as a generator is not sufficient to achieve or maintain a target deceleration or a target speed of the motor vehicle. Method according to one of the Claims 1 until 4th , characterized in that an engine start operating mode is provided in which the internal combustion engine (VM) is started from the first or second purely electric operating mode, the engine start operating mode differing from the first and second purely electric operating mode. Method according to one of the Claims 1 until 5 , characterized in that an internal combustion engine shutdown mode is provided in which the internal combustion engine (VM) is switched off starting from a hybrid drive mode, the internal combustion engine shutdown mode being different from the first and second purely electric operating mode. Method according to one of the Claims 1 until 6th , characterized in that in a roll state of the motor vehicle in which the electric machine (EM) is used as a drive source without load or with a very low load, starting from the first purely electrical operating mode is changed to the second purely electrical operating mode when a speed of the Motor vehicle reaches or falls below a limit value. Method according to one of the Claims 1 until 7th , characterized in that, in a stop-and-go mode, the motor vehicle is operated in the second purely electrical operating mode. Method according to one of the Claims 1 until 8th , characterized in that in a stop-and-go operation of the motor vehicle, the same is only operated in the second purely electrical operating mode when a temperature value of the internal combustion engine (VM) is less than a limit value. Method according to one of the Claims 1 until 9 , characterized in that in a purely electric sports driving mode, the motor vehicle is operated in the second purely electric operating mode. Method according to one of the Claims 1 until 10 , characterized in that the motor vehicle is operated in the second purely electrical operating mode when the motor vehicle is pulling a trailer. Method according to one of the Claims 1 until 11 , characterized in that the motor vehicle is operated in crawling mode in the second purely electrical operating mode when a road gradient reaches or exceeds a limit value. Method according to one of the Claims 1 until 12th , characterized in that the motor vehicle is operated in the second purely electrical operating mode when a change in the direction of travel of the motor vehicle is detected or anticipated. Method according to one of the Claims 1 until 13th , characterized in that the motor vehicle is operated in an off-road operating mode in the second purely electrical operating mode. Electronic control unit (ECU), characterized in that the electronic Control unit (ECU) for performing the method according to one of the Claims 1 until 14th is set up. Motor vehicle, characterized by an electronic control unit (ECU) according to Claim 15 .

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