Controlling an all-wheel drive coupling

Abstract

Method (200) for controlling an all-wheel drive coupling (130) on board a motor vehicle (100), wherein the method (200) comprises the following steps: Determining (215) a driving route (310) lying in front of the motor vehicle (100); determining (230) a section (315, 320) of the driving route (310) on which the all-wheel drive coupling (130) is to be closed; and closing (235) the all-wheel drive coupling (130) before the motor vehicle (100) reaches the section (315, 320), characterized in that the driving route (310) is determined within a predetermined driving horizon on the basis of ADASIS data.

Description

[0001] The invention relates to the control of an all-wheel drive clutch. In particular, the invention relates to the active actuation of an all-wheel drive clutch.

[0002] A motor vehicle comprises multiple axles with drive wheels. In an embodiment with switchable all-wheel drive, a drive motor permanently acts on one of the axles and can additionally act on another axle via an all-wheel clutch. The all-wheel clutch can be passively or actively actuated. With passive actuation, the all-wheel clutch closes fully or partially when a speed on the input side of the all-wheel clutch reaches a predetermined threshold or when a speed difference between the input side and the output side exceeds a predetermined threshold. Active actuation can be made dependent on any parameters and is usually carried out by means of a mechanical actuator, which can be embodied, for example, as an electric motor.

[0003] The all-wheel drive clutch is typically engaged to prevent one of the vehicle's wheels from slipping under difficult driving conditions. If slippage is detected, the all-wheel drive clutch should typically be engaged within approximately 100 to 200 ms to avoid signaling to the driver of the vehicle an impending loss of control. In a passenger car or light commercial vehicle, the actuating force required to open or close the all-wheel drive clutch is large enough to require an actuator with an output of approximately 300 W. An actuator with less power would require a more powerful reduction gear to apply the actuating force, meaning the required actuation time could not be achieved. However, an actuator of the described performance class is relatively large and heavy, and its electrical power consumption must be taken into account accordingly in the vehicle's on-board system.It is therefore an object of the present invention to provide an improved technology for controlling an all-wheel drive clutch on board a motor vehicle. The invention achieves this object by means of the subject matter of the independent claims. Subclaims specify preferred embodiments.

[0004] A method for controlling an all-wheel drive clutch on board a motor vehicle comprises the steps of determining a route ahead of the motor vehicle; determining a section of the route on which the all-wheel drive clutch should be engaged; and engaging the all-wheel drive clutch before the motor vehicle reaches the section. A corresponding method can be used to disengage the all-wheel drive clutch before the motor vehicle reaches a section on which the all-wheel drive clutch should be disengaged.

[0005] According to the method, it is possible to engage or disengage the all-wheel drive clutch even before a driving situation of the motor vehicle immediately requires it. By anticipating engagement, the driving safety of the motor vehicle can be increased. By anticipating engagement, less drive energy can be required for the motor vehicle automatically. In particular, engaging or disengaging the all-wheel drive clutch can take place relatively shortly before a driving situation that requires it is expected to occur. The motor vehicle can thus be driven more effectively with the all-wheel drive clutch engaged or disengaged depending on the route. The driver does not have to bear the burden of engaging or disengaging the all-wheel drive clutch.

[0006] The all-wheel drive clutch is typically configured to transmit drive torque from a drive motor to the wheels of an axle when the all-wheel drive clutch is engaged. Similarly, the wheels can be disconnected from the drive motor by disengaging the all-wheel drive clutch. Preferably, the motor vehicle comprises at least two axles, one of which is permanently driven by the drive motor, while the other is designed to be engageable by means of the all-wheel drive clutch. In a further embodiment, more than two axles can be provided on the motor vehicle, with at least one of the axles being permanently coupled to the drive motor and at least one being engageable by means of an all-wheel drive clutch. The all-wheel drive clutch can also engage multiple axles simultaneously, or multiple all-wheel drive clutches can be assigned to multiple axles or axle groups.

[0007] The all-wheel-drive clutch can be engaged, in particular, if the specific route indicates a risk of a vehicle wheel slipping. This can proactively prevent a vehicle wheel slipping from leading to unstable driving or giving the driver the impression of reduced control over the vehicle.

[0008] The all-wheel drive clutch can be engaged in particular when the section includes a curve. In another embodiment, the all-wheel drive clutch can be engaged when the section includes an uphill gradient. In both cases, a threshold value can be predetermined so that the all-wheel drive clutch is engaged when the radius of the curve falls below the threshold value or the gradient exceeds the threshold value. A downhill gradient is preferably included as a negative gradient. In both cases, a vehicle speed of the motor vehicle can also be evaluated so that the threshold value can be variable depending on the speed of the motor vehicle. This allows the all-wheel drive clutch to be engaged in an improved manner precisely when the driving stability of the motor vehicle requires improvement by engaging a drive axle.

[0009] The route ahead of the motor vehicle can be determined based on the position of the motor vehicle and stored map data in the area of ​​the position. For example, the position of the motor vehicle can be determined using a satellite navigation receiver, and the stored map data can be shared by a navigation system. It is preferred that the map data include topographical information, e.g., a gradient.

[0010] It is further preferred that the route within a predetermined driving horizon is determined based on ADASIS data. ADASIS (Advanced Driver Assistance Systems Interface Specifications) data is available in a cross-manufacturer standard for exchanging data for driver assistance systems. One or more ADASIS systems can be provided on board the motor vehicle, providing information about the route ahead of the motor vehicle. This information is typically limited to a driving horizon extending from the motor vehicle and is preferably larger than the area visible to a driver of the motor vehicle. The method can be easily implemented on board a conventional motor vehicle with ADASIS components.

[0011] It is further preferred that the all-wheel-drive clutch be opened or closed while the torque transmitted via it is below a predetermined threshold. Opening or closing the all-wheel-drive clutch can thus be carried out in a particularly gentle manner. Mechanical stress, aging, or wear on the all-wheel-drive clutch can thus be limited.

[0012] A control system for a controllable all-wheel drive on board a motor vehicle comprises an interface for sampling data relating to a route ahead of the motor vehicle; an actuator for opening or closing the all-wheel drive clutch; and a processing device for carrying out the method described above.

[0013] The all-wheel-drive clutch can be constructed in different ways. In one embodiment, the all-wheel-drive clutch is constructed as a friction-disk clutch. In another embodiment, the all-wheel-drive clutch comprises a dog clutch. The dog clutch provides positive engagement with potentially high load capacity, but does not allow partial engagement and therefore also no slippage via the all-wheel-drive clutch. Particularly when using the dog clutch, it is preferred that the all-wheel-drive clutch be opened or closed with as little load as possible. The load is at its lowest when the torque transmitted via the all-wheel-drive clutch is as close to zero as possible, or when the speed difference between an input side and an output side of the all-wheel-drive clutch is as close to zero as possible.The method described above can therefore shift the opening or closing of the all-wheel drive clutch so far before the motor vehicle enters the described section that driving conditions allow the all-wheel drive clutch to be opened or closed with little stress.

[0014] It is further preferred that the actuator comprises an electric geared motor. The gear can have a relatively high reduction factor, so that the required actuating force for opening or closing the all-wheel drive clutch can be applied by a small or lightweight electric motor. A reduced opening or closing speed of the all-wheel drive clutch can be accepted, since the need to open or close the all-wheel drive clutch is usually known several seconds in advance. An actuating time of the actuator can be in the range of one second or more. The actuating time can be taken into account when carrying out the method described above. The actuator can therefore be made smaller or lighter, which saves installation space or costs.The actuator's electrical power consumption can be reduced, allowing the vehicle's electrical system to be smaller. This can result in additional material and weight savings.

[0015] In a further embodiment, the all-wheel-drive clutch includes a differential lock. The differential lock is preferably activated when the all-wheel-drive clutch is closed and deactivated when the all-wheel-drive clutch is open. In a preferred, combined embodiment, the all-wheel-drive clutch controls both the transmission of torque between a drive motor and a drive axle and the locking of a differential between different sides of this axle.

[0016] The invention will now be described in more detail with reference to the accompanying figures, in which: Fig. 1 a motor vehicle with an all-wheel drive system; Fig. 2 a flowchart of a method for controlling the all-wheel drive system of Fig. 1; and Fig. 3 an illustration of the procedure of Fig. 2 represents.

[0017] Fig. 1 shows a motor vehicle 100 with an all-wheel drive system 105. The motor vehicle 100 comprises a drive engine 110, which is typically followed by a transmission 115 that acts on the all-wheel drive system 105. The all-wheel drive system 105 comprises at least one first axle 120, which is permanently driven, and at least one second axle 125, which can be selectively driven via an all-wheel drive clutch 130. A differential gear 135 can be provided on each axle 120, 125. Furthermore, at least one wheel 140 for transmitting drive forces is attached to each axle 120, 125.

[0018] In the illustrated embodiment, the first, permanently driven axle 120 is a front axle and the second, switchably driven axle 125 is a rear axle of the motor vehicle 100. However, other configurations can also be selected in other embodiments.

[0019] The all-wheel drive clutch 130 can be opened or closed by means of an actuator 150. The actuator 150 preferably comprises an electric motor with a reduction gear. A further differential gear 135 can be provided to decouple the first axle 120 and the second axle 125 from one another. This differential gear 135 can be lockable, and the actuator 150 can be configured to lock the differential gear 135 when the all-wheel drive clutch 130 is closed and to release the lock when the all-wheel drive clutch 130 is opened. Similarly, the differential gears 135 on the first axle 120 or the second axle 125 can be lockable and can be locked or released in the same way by the actuator 150. Both a differential lock and the all-wheel drive clutch 130 can comprise a dog clutch.

[0020] To control the all-wheel drive clutch 130, a control system 160 is provided, which comprises a processing device 165, a first interface 170 for connection to a data memory 175 and / or a second interface 180 for connection to another control unit on board the motor vehicle 100, and the actuator 150. A wireless interface 185 can also be provided. The control system 160 is configured to use the actuator 150 to control the all-wheel drive clutch 130 such that it is opened or closed in anticipation of a route ahead of the motor vehicle 100. The route is preferably determined based on map data in the data memory 175. The processing device 165 can receive a current position of the motor vehicle 100 from a positioning device via the second interface 180.The data storage 175 can then be queried for information in the area of ​​the determined position. It is particularly preferred that the processing device 165 be connected to an ADASIS system on board the motor vehicle 100 via only one of the interfaces 170, 180, which provides information regarding the route ahead of the motor vehicle 100. Additional information or an update of information in the data storage 175 can be received via the wireless interface 185.

[0021] Fig. 2 shows a flowchart of an exemplary method 200 for controlling the control system 160. The method 200 is configured, in particular, to run on the processing device 165. For this purpose, the processing device 165 may, in particular, comprise a programmable microcomputer, and the method 200 may be in the form of a computer program product.

[0022] In an optional step 205, a driving state of the motor vehicle 100 can be determined. This step can include receiving information via the second interface 180, and the information can include, in particular, a speed or acceleration of the motor vehicle 100 or an intended path of the motor vehicle 100, which can be adopted, for example, by a navigation system.

[0023] In a step 210, the position of motor vehicle 100 can be determined, and based on the position, a route ahead of motor vehicle 100 can be determined. This step can be replaced by receiving corresponding ADASIS data. In this case, the contents of step 215 can be performed by another component that provides ADASIS data.

[0024] The determined route ahead can then be analyzed. The route, which typically extends from motor vehicle 100 to a predetermined driving horizon, is preferably examined for curves in a step 220 or for inclines in a step 225. The goal of the examination is to divide the route, in a subsequent step 230, into first sections in which all-wheel drive clutch 130 should be engaged, and second sections in which all-wheel drive clutch 130 should be disengaged. The division in step 230 or the evaluation of a curve in step 220 or an incline in step 225 can be carried out in particular depending on the driving state of motor vehicle 100 determined in step 205.In particular, the splitting can be performed depending on the vehicle speed, so that, for example, a predetermined curve traveled at high speed can be considered a section with the all-wheel drive clutch engaged, and a section with the all-wheel drive clutch disengaged when the speed is low. The vehicle speed can be compared with a threshold value, which depends, for example, on a minimum curve radius, in order to distinguish between a high and a low vehicle speed.

[0025] In various embodiments, greater emphasis can be placed on the all-wheel drive clutch 130 either being closed in anticipation or opened in anticipation. In the first case (anticipatory closing), the all-wheel drive clutch 130 can be closed before the motor vehicle 100 enters the first section and only opened when the motor vehicle 100 has exited the first section. In the second case (anticipatory opening), the all-wheel drive clutch 130 can be opened before the motor vehicle 100 enters the second section and only closed after the motor vehicle 100 has already left the second section. A precise switching between the open and closed state of the all-wheel drive clutch 130 at the boundaries between a first and a second section can also be aimed for in order to integrate both cases as far as possible.

[0026] In a step 235, the all-wheel-drive clutch 130 is preemptively closed or opened according to the selected strategy, allowing all-wheel drive to be activated or deactivated. Method 200 can then be repeated to enable the most permanent preemptive actuation of the all-wheel-drive clutch 130 by means of the actuator 150.

[0027] Fig. 3 shows an illustration of the method 200 of Fig. 2. In the present example, which is to be understood as exemplary, the motor vehicle 100 travels on a terrain 305, the contour lines of which are in Fig.3. The motor vehicle 100 follows a route 310, which is composed of the above-mentioned first sections 315, in which the all-wheel drive clutch 130 is to be engaged, and second sections 320, in which the all-wheel drive clutch 130 is to be disengaged. The first sections 315 are shown with a solid line, and the second sections 320 with a dashed line.

[0028] Initially, the motor vehicle 100 essentially follows the contour lines of the terrain 305, traveling along a second section 320.1 with few curves and gradients. Then, the motor vehicle 100 follows a sharp left turn, which marks a first section 315.2. After a brief interruption by a second section 320.3, the motor vehicle 100 crosses several contour lines one after the other practically vertically on a first section 315.4, which corresponds to a gradient or a gradient.

[0029] Subsequently, the motor vehicle 100 travels between contour lines on a second section 320.5 before traversing another incline or decline on a first section 315.6. This is followed by a second section 320.7 without steep inclines or declines or tight curves, and finally a first section 315.8 with a steep incline and an entry-side curve.

[0030] It is preferred to operate the method 200 such that the all-wheel drive clutch 130 is proactively engaged before the motor vehicle 100 reaches a first section 315 and is only opened again once the motor vehicle 100 has left the first section 315. If two first sections 315 are separated from each other by a short second section 320, the all-wheel drive clutch 130 can also remain engaged on the second section 320. Such a situation can occur, for example, in the area of ​​sections 315.2, 320.3, and 315.4.

[0031] The invention is based on the finding that the opening and closing of the all-wheel drive clutch 130 can be performed depending on a prediction of the terrain 305 to be traveled. It is particularly preferred to obtain the corresponding terrain information from a component that provides it via the ADASIS protocol. The presented technology can be used in particular on board a passenger car, but also, for example, on construction machinery, agricultural machinery, a truck, or a bus. Reference symbol 100 motor vehicles 105 all-wheel drive system 110 drive motor 115 gearboxes 120 first axle (permanently driven) 125 second axle (switchable) 130 all-wheel drive clutch 135 differential gear 140 wheels 150 actuator 160 Tax system 165 processing facility 170 first interface 175 data storage 180 second interface 185 wireless interface 200 procedures 205 Determine driving condition of motor vehicle 210 Determine position of motor vehicle 215 Determine route 220 curve 225 gradient 230 Divide the route into sections 235 predictive Activate or deactivate all-wheel drive 305 terrain 310 driving distance 315 first section (all-wheel drive clutch closed) 320 second section (all-wheel drive clutch open)

Claims

[1] Method (200) for controlling an all-wheel clutch (130) on board a motor vehicle (100), the method (200) comprising the following steps: Determining (215) a route (310) ahead of the motor vehicle (100); determining (230) a section (315, 320) of the route (310) on which the all-wheel drive clutch (130) should be closed; and closing (235) the all-wheel drive clutch (130) before the motor vehicle (100) reaches the section (315, 320), characterized by that the route (310) within a predetermined driving horizon is determined on the basis of ADASIS data. [2] Method (200) for controlling an all-wheel clutch (130) on board a motor vehicle (100), the method (200) comprising the following steps: Determining (215) a route (310) ahead of the motor vehicle (100); determining (230) a section (315, 320) of the route (310) on which the all-wheel drive clutch (130) should be opened; and opening (235) the all-wheel drive clutch (130) before the motor vehicle (100) reaches the section (315, 320), characterized by that the route (310) within a predetermined driving horizon is determined on the basis of ADASIS data. [3] Method (200) according to claim 1 or 2, wherein the all-wheel clutch (130) is to be closed on the section (315, 320) when the determined route (310) indicates a risk of slipping of a wheel (140) of the motor vehicle (100). [4] Method (200) according to claim 3, wherein the all-wheel clutch (130) is to be closed on the section (315, 320) when the section (315, 320) comprises a curve. [5] Method (200) according to claim 3 or 4, wherein the all-wheel clutch (130) is to be closed on the section (315, 320) when the section (315, 320) comprises an incline. [6] Method (200) according to one of the preceding claims, wherein the route (310) is determined on the basis of a position of the motor vehicle (100) and stored map data in the area of ​​the position. [7] Method (200) according to one of the preceding claims, wherein the all-wheel drive clutch (130) is opened or closed while the torque transmitted therethrough is below a predetermined threshold value. [8] A control system (160) for a controllable all-wheel drive on board a motor vehicle (100), the control system (160) comprising: an interface (170, 180) for sampling data relating to a route (310) ahead of the motor vehicle (100); an actuator (150) for opening or closing the all-wheel clutch (130); and a processing device (165) for carrying out a method (200) according to any one of the preceding claims. [9] The control system (160) of claim 8, wherein the all-wheel drive clutch (130) comprises a dog clutch. [10] Control system (160) according to claim 8 or 9, wherein the actuator (150) comprises an electric gear motor.

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