DE102011005095A1 - Control device for motor vehicle e.g. motor car, detects presence/absence of sailing operation, to open transmission clutch up to minimum degree depending on predefined current driving dynamic requirements in presence of sailing operation - Google Patents

Abstract

The device has a control unit (8,9) that controls drive unit (10) that determines target clutch torque on transmission clutch (1) set by actuator device. The control unit converts target clutch movement into electric current. A drive unit changes drive torque distributed to wheels (6,7) via transmission clutch. The control unit receives input signal and detects the presence/absence of sailing operation so that the transmission clutch is opened up to a minimum degree of locking respectively depending on predefined current driving dynamic requirements in the presence of sailing operation.

Description

The invention relates to a control device for a motor vehicle with four wheels and with a control unit, by means of which the drive torque of a drive unit as required via at least one transfer clutch to at least one wheel is variably distributed, according to the preamble of claim 1.

Such a control device is for example in the DE 100 54 023 A1 described. Accordingly, a torque distribution device is known for changing the torque distribution ratio between the wheels of the front axle and the wheels of the rear axle by corresponding control of a transfer clutch in the sense of a longitudinal lock, for example in the form of a friction clutch. By defining a torque distribution ratio, the driving behavior of a vehicle can be significantly influenced. The object of DE 100 54 023 A1 deals in particular with the driving dynamics when cornering. In this case, a temporarily four-wheel drive motor vehicle can be a basically front-wheel drive motor vehicle with a rear-wheel drive that can be engaged via a transmission clutch, a rear wheel drive motor which can be activated via a transfer clutch or a permanent four-wheel drive vehicle with a variable transfer clutch for changing the torque distribution between the front and rear axles.

Usually generalized in this regard are also referred to as the primary drive wheels permanently connected to the drive unit wheels and secondary drive wheels on the transfer coupling, if necessary, connectable to the drive unit wheels.

But are also known control devices of the type mentioned in which individual transmission wheels in the sense of a transverse lock - alternatively or in addition to a transfer clutch in the sense of a longitudinal lock - individual wheels of an axle as needed variable torque with a drive unit can be acted upon.

It is an object of the invention to improve a control system of the type mentioned in terms of reducing fuel consumption.

This object is solved by the features of patent claim 1. Advantageous developments are the subject matters of the dependent claims.

The invention is based on the following considerations:
Basically, a so-called sailing operation is known in connection with the drive unit of motor vehicles consisting of drive motor (s) and gearbox under defined conditions. The term sailing operation is understood to mean in particular a free rolling by interrupting the frictional connection between the drive motor and the transmission. Conditions for activating the sailing operation, for example, the release of the accelerator pedal when driving straight ahead. The sailing operation can be prevented for driving dynamics reasons, for example, when cornering or too steep downhill. Even with desired Rekuperationsvorgängen the sailing operation can be prevented. Conditions for switching on and off a sailing operation are already known. For this purpose, for example, on the not pre-published DE 10 2010 031 382 referred to the applicant.

In electronically controlled motor vehicles, in particular all-wheel drive vehicles, driving dynamics (and thus also driving safety-influencing) requirements such as longitudinal and transverse guidance stability are in the foreground, with the transfer clutch between the primary and secondary drive wheels or, in the case of non-all-wheel drive vehicles, usually at least partially closing the transfer clutch of transverse locks is.

The invention is based on the finding that, in turn, potential for saving fuel is lost, for example, as a result of friction losses (eg due to momentary stresses) and inertia losses in the drive train. Therefore, according to the invention, a minimum degree of locking for the transmission clutch (s) is determined in each case dependent on given current driving dynamics requirements, which can also be zero and in the presence of a sailing operation - preferably only after the opening of the clutch between the drive motor and transmission or after opening a clutch in the transmission - is specified.

Predetermined respectively current driving dynamics requirements are defined, for example, by threshold value monitoring with respect to the following parameters: lateral acceleration and / or yaw rate and / or vehicle speed and / or inclination angle (gradient, gradient) and / or road condition (smoothness, wetness, road surface with loose ground, dry roadway ). Through the connection with a navigation system can also be made predictive considerations.

Preferably, in the presence of relatively low driving dynamic requirements, not only the minimum stop degree of the transfer clutch (s) is set, but also energy-consuming components of other vehicle dynamics control systems - such as actuators active steering intervention systems and / or active roll stability systems and / or active vertical control systems (eg., Active spring / damper systems) and / or active stability / traction / brake control systems - temporarily disabled. Relatively low driving dynamics requirements are, for example, for longer straight-ahead driving (lateral acceleration and / or yaw rate at least almost zero) and / or moderate vehicle speed (for example, up to 100 km / h) and / or almost no slope (tilt angle at least almost zero) and / or on dry roads.

In an advantageous development of the invention, a transmission clutch can be completely opened in the given special conditions, but a more sensitive in the sense of a sensitive response and possibly resulting increased engagement of another vehicle dynamics control system (such as active stability / traction / brake control systems) made to ensure driving safety in extreme situations with optimum fuel consumption.

In the drawing, an embodiment of the invention is shown. It shows schematically a temporary four-wheel drive vehicle with an adjustable via a control unit according to the invention transfer clutch - here in the sense of a longitudinal lock - the example of a basically rear-wheel drive motor vehicle with a transfer clutch shiftable front wheel drive.

In the single figure is a temporary four-wheel drive vehicle in the form of a basically rear-wheel drive motor vehicle with, if necessary, via a transfer clutch 1 switchable front wheel drive shown. The transfer clutch 1 is via an electronic control unit 8th adjustable. The control unit 8th can an outsourced, z. B. directly to the transfer clutch 1 attached additional control unit 9 contain, for example, the predetermined target clutch _torque M _Ksoll in electric current for controlling the adjustment (not shown here) of the transfer clutch 1 implements.

In a vehicle according to the illustrated embodiment is open with transfer clutch 1 the total torque (drive torque) of the drive unit 10 on the wheels 6 and 7 the rear axle 3 transfer. Preferably, the drive unit consists 10 from a drive motor 11 (For example, an internal combustion engine and / or an electric motor), a transmission 12 , a clutch 13 and at least one drive control unit - here engine control unit 14 and gearbox control unit 15 , The drive controllers 14 and 15 communicate for example via the known motor vehicle data bus CAN or FlexRay with the control unit 8th and optionally other control devices, such as. B. the controller 17 active steering control or roll stabilization.

In the drawing are the rear wheels 6 and 7 the primary drive wheels, since they are permanently connected to the drive unit 9 are connected. With increasing clutch torque at the transfer clutch 1 drives the drive unit 10 also the wheels 4 and 5 the front axle 2 at. Thus, the front wheels 4 and 5 the secondary drive wheels.

The control unit 8th recorded to further input signals in particular an input signal for detecting the sailing operation, for example, a (not shown here) sailing operation status bit or the position of an accelerator pedal, z. As the operating angle FP of the so-called. Gas pedal or even transmitted from an engine control unit, effective powertrain gain. Furthermore, the control unit detects or determines 8th For example, the engine speed n _Mot , the engine torque (= engine torque and / or the torque of another / further drive unit) or the drive torque (= gearbox output propeller shaft torque), the steering angle LW, the yaw rate or yaw rate r and the wheel speeds n _VL , n _HL , n _VR , n _{HR of} all wheels 4 . 5 . 6 . 7 , From these wheel speeds n _VL , n _HL , n _VR , n _HR are in connection with others in the control unit 8th present information, the wheel speeds v _VL , v _HL ; v _VR , v _{HR of} all wheels 4 . 5 . 6 . 7 and the vehicle speed v determined.

For distribution of the drive torque of the drive unit 10 is a set target clutch torque M _Ksoll for between the drive unit 10 or the primary drive wheels 6 and 7 and the secondary drive wheels 4 and 5 arranged transmission clutch 1 specified. Preferably, the control unit outputs 8th the desired clutch _torque M _Ksoll to the additional control unit 9 out. The additional control unit 9 sets the target clutch _torque M _Ksoll in a current for controlling the actuator not shown here specifically.

In the control unit 8th is usually determined taking into account wheel slip and driving dynamics variables, such as oversteer and understeer the target clutch _torque M _Ksoll .

According to the invention by means of the regulator unit 16 , For example, in the form of a software module, determines whether a sailing operation is present. When sailing operation is present - preferably after opening the clutch 13 between gears 12 and drive motor 11 or after opening one Clutch in the gearbox 12 itself - also the transfer _clutch open at least up to a minimum _{degree of locking} M _Ksoll = M _Kmin . Will the transfer clutch 1 Fully opened, special conditions that meet high driving dynamics requirements or even critical situations may, if necessary, lead to an intensified or more sensitive compensating intervention of another vehicle dynamics control system, in particular an active brake control system. The control of the active brake control system may also be in the control unit 8th be integrated.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 10054023 A1 [0002, 0002]
• DE 102010031382 [0007]

Claims (3)

Control device for a motor vehicle with four wheels ( 4 . 5 . 6 . 7 ) and with a control unit ( 8th ; 8th . 9 ), by means of which the drive torque of a drive unit ( 10 ) as required via at least one transfer clutch ( 1 ) on at least one wheel ( 6 . 7 ) is variably distributable by the control unit ( 8th ; 9 ) determines a desired clutch _torque (M _Ksoll ), which by means of an actuator device at the at least one transfer clutch ( 1 ), characterized in that the control unit ( 8th ; 8th . 9 ) receives at least one input signal (FP, LW) for detecting a sailing operation and is designed such that in the presence of the sailing operation, the transfer clutch ( 1 ) is opened at least partially up to a minimum _{degree of locking} (M _Ksoll = M _Kmin ), which is determined as a function of predetermined respectively current driving dynamics requirements _{Control device} according to claim 1, characterized in that in the presence of relatively low driving dynamics requirements not only the minimum _{degree of locking} (M _Ksoll = M _Kmin ) of the transfer _clutch ( 1 ), but also energy-consuming components of other vehicle dynamics control systems are disabled. Control device according to one of the preceding claims, characterized in that at predetermined special conditions the at least one transfer clutch ( 1 ) is fully opened and at the same time, if necessary, an increased or more sensitive intervention of another vehicle dynamics control system is made.

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