DE102021206807A1 - Method of clutch engagement and motor vehicle - Google Patents

Abstract

The invention relates to a method for engaging a clutch which connects a drive train of a motor vehicle to an internal combustion engine while the motor vehicle is moving, with a deceleration torque generated thereby being calculated while the clutch is being engaged and a braking force acting on the drive train being reduced as a function thereof. The invention also relates to an associated motor vehicle.

Description

The invention relates to a method for engaging a clutch which connects a drive train of a motor vehicle to an internal combustion engine, and an associated motor vehicle.

In the course of greater fuel efficiency, combustion engines are increasingly being decoupled from the drive train by means of a clutch if they are not intended to generate propulsion. Such operating modes can be referred to as coasting, for example. Engaging a motor when a driving request changes typically costs time and energy. In addition, a clearly perceptible jerk can occur.

It is therefore an object of the invention to provide a method for engaging a clutch which is alternative or improved compared to known designs. It is also an object of the invention to provide an associated motor vehicle.

According to the invention, this is achieved by a method and a motor vehicle according to the respective main claims. Advantageous configurations can be found, for example, in the respective dependent claims. The content of the claims is made part of the content of the description by express reference.

• - Einkuppeln der Kupplung, dabei Berechnen eines dadurch erzeugten Verzögerungsmoments, und
• - Verringern einer am Antriebsstrang wirkenden Bremskraft in Abhängigkeit von dem Verzögerungsmoment.

The invention relates to a method for engaging a clutch which connects a drive train of a motor vehicle to an internal combustion engine while the motor vehicle is moving. The procedure has the following steps:

• - Engaging the clutch, thereby calculating a deceleration torque generated thereby, and
• - Reducing a braking force acting on the drive train as a function of the deceleration torque.

By means of such a method, a deceleration torque, which occurs when the clutch is engaged because of the contact with the internal combustion engine that is now present, can be taken into account and an acting braking force can be correspondingly reduced. Any jerking can be reduced or avoided in this way, since the additional braking effect applied by the motor is compensated for by an acting braking force being correspondingly reduced. This allows the clutch to be engaged without disruptive jerks.

A clutch can be understood in particular as an actuable element which in one state represents a rotational connection between the internal combustion engine and the drive train, whereas in another state it rotationally decouples the internal combustion engine and the drive train. Transitions are also possible between the two end positions, in which a partial power transmission can take place. A deceleration torque is to be understood in particular as a torque which acts on the drive train when the clutch is engaged due to the then existing connection between the drive train and the combustion engine, and which typically initially has a braking effect. A braking force is typically a force which is applied by a brake, for example a wheel brake, in order to decelerate the vehicle. This can be reduced according to the deceleration torque. This can take place in particular over a predetermined period of time, it also being possible for the deceleration torque to be calculated several times within this period of time.

The internal combustion engine can be started in particular by engaging the clutch. This allows the electrical energy otherwise required to operate a starter to be saved.

The engagement can be carried out in particular from a deactivated internal combustion engine. The internal combustion engine can be switched off during coasting, so that fuel is saved. A deactivated internal combustion engine can be understood in particular as an internal combustion engine to which no fuel is supplied in the deactivated state and/or whose crankshaft is not rotating.

The coupling can take place in particular according to a predetermined course. Such a course can be specified, for example, as a force-time curve.

The deceleration torque can be calculated in particular based on driving parameters and/or engine parameters. Driving parameters can be understood in particular as parameters relating to driving a motor vehicle, such as speed or acceleration. Engine parameters can be understood, for example, as performance data of the engine or current values from sensors in the internal combustion engine.

The braking force can be reduced, in particular, by means of a braking system that enables the braking force to be built up independently of the driver. For example, it can be a by Trade wire system. This allows a particularly individual control of the braking system.

In particular, the braking force can be reduced in such a way that the deceleration torque is compensated for. This allows particularly jerk-free engagement.

The engagement can be carried out in particular starting from a braking force that is already in effect. This typically takes place while the vehicle is being decelerated, which can be requested, for example, by a driver or a driving dynamics control system. If the internal combustion engine was started by engaging the clutch, it is subsequently available again for generating propulsion.

In particular, the engagement can take place starting from a completely disengaged state. Such a completely disengaged state can mean, for example, that there is no longer a power connection between the internal combustion engine and the drive train.

In particular, the drive train can act on one or more drive wheels. For example, one axle can be driven, or both axles can be driven. Also more axes can be used accordingly, which can be driven or not driven. When engaged, the internal combustion engine typically generates propulsion, which acts on the drive wheels and thus propels a vehicle.

In particular, no electric starter can be used to start the internal combustion engine during clutch engagement. This saves electrical energy for the starter. In particular, the starter can remain switched off. The electric motor can still be started by the rotary motion present in the drive train.

The method can be carried out in particular in response to a driver braking request. After such a braking request, engine power is typically required, which is then available through the engagement of the clutch.

According to a preferred embodiment, before the clutch is engaged, a target gear of a transmission to which the clutch is connected is set. Such a target gear can be specified, for example, or can be calculated using various parameters. A target gear can be, for example, one gear among several gears of a transmission, in which case the internal combustion engine can act on the drive wheels via the clutch and the transmission. By setting a target gear, it can be achieved in particular that the internal combustion engine can act on the drive train in an ideal gear immediately after the clutch is engaged. The target gear can be fixed, or it can be calculated each time the clutch is engaged.

The invention also relates to a motor vehicle. The motor vehicle has an internal combustion engine, a drive train and a clutch which connects the drive train to the internal combustion engine. The motor vehicle also has a braking system. It also has a control device configured to carry out a method described herein. With regard to the method, all of the versions and variants described herein can be used.

The method described herein can advantageously be implemented by means of such a motor vehicle. The advantages already described above can be achieved.

The motor vehicle can in particular also have an electric motor to support the internal combustion engine. This allows power to be generated jointly and/or alternately by the internal combustion engine and the electric motor. For example, this can be a mild hybrid system. However, this is not absolutely necessary for a motor vehicle that carries out a method according to the invention. In principle, the method can be used for any type of vehicle with the components mentioned.

For example, there can also be an additional voltage source in addition to an alternator which is driven by an internal combustion engine. This additional voltage source can be an accumulator, for example. As a result, a power supply can be ensured when the internal combustion engine is switched off.

In other words, for example, as soon as a driver steps on the brake pedal during coasting, a target gear can be selected in a dual clutch transmission and/or automatic transmission. The clutch can then be closed with a predetermined course in order to drive the engine. An engine control unit and a transmission control unit can calculate a torque on the clutch and send this to a brake control unit via CAN/FlexRay, for example. In a by-wire system, precisely this moment can be dynamically compensated, resulting in a constant braking moment at the vehicle level and thus a constant deceleration. The vehicle delays This results in particular from the sum of the hydraulic braking torque and the drag torque of the engine as a function of the transmitted clutch torque.

This results in particular in a saving in carbon dioxide emissions in a WLTP test cycle as well as in real operation by starting the clutch with each braking maneuver. No fuel or electrical energy is used in the process. A faster engine start enables faster triggering of recuperation, for example in hybrid architectures. In addition, a noticeable jerk for the driver is avoided. The wear of a pinion starter is also reduced.

• 1: ein Kraftfahrzeug.

The person skilled in the art will derive further features and advantages from the exemplary embodiment described below with reference to the attached drawing. It shows:

• 1 : a motor vehicle.

1 shows purely schematically a motor vehicle 10 according to an embodiment of the invention. The motor vehicle 10 has an internal combustion engine 20 which can ensure propulsion of the motor vehicle 10 . It acts via a clutch 30 on a drive train 40, which in turn is connected to two rear wheels 51, 52. Furthermore, the motor vehicle 10 also has two front wheels 53, 54, the function of which, however, will not be discussed further here.

Motor vehicle 10 has a brake system 60 with a first brake 61 and a second brake 62 . The first brake 61 acts on the left rear wheel 51, whereas the second brake 62 acts on the right rear wheel 52.

Furthermore, the motor vehicle 10 has a control device 70 . This is configured to carry out a method according to the invention, which is described below.

In normal operation, the clutch 30 is engaged so that the internal combustion engine 20 can drive the motor vehicle 10 via the two rear wheels 51, 52. These are therefore drive wheels. For this purpose, a transmission (not shown) can also be interposed. If no propulsion is required for a certain moment, for example because a slow deceleration is to take place or the motor vehicle 10 is driving down an incline, then the internal combustion engine 20 can be disengaged by means of the clutch 30 . It can also be switched off to save fuel. If motor vehicle 10 is to be braked, braking system 60 can be used for this purpose. If the internal combustion engine 20 is to be restarted during such a braking process, the clutch 30 can engage in accordance with a predetermined force profile, so that the internal combustion engine 20 can be restarted without the aid of an electric starter. The control device 70 can calculate a deceleration torque, which the internal combustion engine 20 exerts on the drive train 40 and thus also on the rear wheels 51, 52. The internal combustion engine 20 therefore has a braking effect, since it starts up again from a switched-off state. A corresponding deceleration torque, which is calculated by the control device 70, is used to correct the braking force applied by the braking system 60. The braking force generated by the two brakes 61, 62 is therefore reduced accordingly, so that no jerks can be felt when the clutch 30 is engaged. This can significantly increase driving comfort.

Mentioned steps of the method according to the invention can be carried out in the order given. However, they can also be executed in a different order, as far as this is technically reasonable. In one of its implementations, for example with a specific combination of steps, the method according to the invention can be carried out in such a way that no further steps are carried out. In principle, however, further steps can also be carried out, including those which are not mentioned.

It should be noted that in the claims and in the description features can be described in combination, for example to facilitate understanding, although they can also be used separately. The person skilled in the art recognizes that such features can also be combined independently of one another with other features or combinations of features.

Back-references in dependent claims can identify preferred combinations of the respective features, but do not exclude other combinations of features.

Reference List

10

motor vehicle

20

combustion engine

30

coupling

40

powertrain

51,52,53,54

Wheels

60

braking system

61

first brake

62

second brake

70

control device

Claims (15)

Method for engaging a clutch (30) which connects a drive train (40) of a motor vehicle (10) to an internal combustion engine (20) while the motor vehicle (10) is being driven, the method comprising the following steps: - Engaging the clutch (30), thereby calculating a deceleration torque generated thereby, and - Reducing a braking force acting on the drive train (40) as a function of the deceleration torque. procedure after claim 1 - wherein the internal combustion engine (20) is started by engaging. Method according to one of the preceding claims, - the engagement being carried out from a deactivated internal combustion engine (20). Method according to one of the preceding claims, - Wherein the coupling takes place according to a predetermined course. Method according to one of the preceding claims, - wherein the deceleration torque is calculated based on driving parameters and/or engine parameters. Method according to one of the preceding claims, - Wherein the braking force is reduced by means of a braking system which enables a driver-independent braking force build-up. Method according to one of the preceding claims, - whereby the braking force is reduced in such a way that the deceleration torque is compensated. Method according to one of the preceding claims, - the engagement being carried out starting from an already acting braking force. Method according to one of the preceding claims, - wherein the engagement occurs from a fully disengaged state. Method according to one of the preceding claims, - The drive train (40) acting on one or more drive wheels (51, 52). Method according to one of the preceding claims, - wherein no electric starter is used to start the internal combustion engine (20) during clutch engagement. Method according to one of the preceding claims, - Which is carried out in response to a driver braking request. Method according to one of the preceding claims, - A target gear of a transmission to which the clutch (30) is connected being set before the clutch is engaged. Motor vehicle (10), comprising - an internal combustion engine (20), - a drive train (40), - a clutch (30) which connects the drive train (40) to the internal combustion engine (20), - a braking system (60), and - a control device (70) which is configured to carry out a method according to any one of the preceding claims. Motor vehicle (10) after Claim 14 - Which further comprises an electric motor to support the internal combustion engine (20).

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