METHOD AND DEVICE FOR PREDICTIVELY DEACTIVATING THE FREEWHEEL MODE OF A ROAD VEHICLE

Abstract

Method for predictive deactivation of a vehicle freewheel mode forcing the opening of the input clutch which connects its drive motor with its kinematic chain, characterized in that the exit from the freewheel mode as well as its prohibition are imposed on the vehicle in anticipation of events detected in advance by an on-board navigation system and for which the need to close the clutch is identified so as to anticipate the increase in the need for braking of the vehicle as they approach. Figure for the abstract: figure 1

Description

Title of the invention: METHOD AND DEVICE FOR PREDICTIVELY DEACTIVATING THE FREEWHEEL MODE OF A ROAD VEHICLE

[0001] The present invention relates to the control of a freewheel function called "free flight" or "sailing" in English, on a motor vehicle, consisting of momentarily interrupting the kinematic connection between the traction motor and the wheels of the vehicle during movement, for reasons of driving pleasure and / or energy saving.

[0002] More specifically, it relates to a method and a device for predictive deactivation of the freewheel mode of a vehicle by forcing the opening of the input clutch which connects its drive motor with its kinematic chain.

[0003] This invention finds its application on any road vehicle having a freewheel mode, and a navigation system.

[0004] To reduce the consumption of a vehicle powered by an internal combustion engine, some vehicles have a freewheeling driving mode ("sailing"), during which the engine is isolated or "disengaged" from the transmission and the powertrain. Under these conditions, the vehicle moves only under the effect of its inertia. In freewheeling, braking requires a greater pressure force on the brake pedal than in traction mode, to obtain the same deceleration. The sensations felt by the driver are therefore different in the two cases. In addition, it is preferable in certain cases for the engine to be engaged, so that the vehicle is responsive if the driver has to suddenly reaccelerate.

[0005] Deactivating the freewheel mode may be necessary to decelerate the vehicle, or contain its speed, for safety reasons. This need can be identified in real time, from the behavior or driving conditions of the vehicle (excessive speed, heavy braking, obstacle detection).

[0006] It can also be detected in advance, depending on the foreseeable speed of the vehicle. From the publication, WO2017 / 079569, a method for controlling the freewheel function is known, capable of predicting a change in speed of the vehicle, depending on the evolution of the terrain. The prohibition or abandonment of the freewheel mode, can be determined from the observation of the road scene by cameras, the evaluation of distances or reaction times, of the vehicle, the slope of the road, or even speed thresholds.

[0007] However, the predictive capacity of such a system and its effectiveness remain limited, in particular because it does not anticipate the behavior of the vehicle when braking.

[0008] The present invention aims to enhance the driving pleasure of a vehicle, by reducing the use of the brakes by the driver, in freewheel mode.

[0009] For this purpose, it proposes that the exit from freewheel mode, as well as its prohibition, be imposed on the vehicle in anticipation of events detected in advance by an on-board navigation system, for which the need to close the clutch is identified to anticipate the increase in the need for braking of the vehicle as they approach.

[0010] The device provided for this purpose comprises an on-board navigation system informing a prediction module of the type of event detected, its distance, its arrival speed, and the average slope of the road between the vehicle and the event.

[0011] These measures reduce the need for the driver to operate the vehicle's brakes. By judiciously deactivating the freewheel, the difference in the vehicle's braking behavior between a normal driving mode and a freewheel mode can be eliminated. Predictive deactivation is based on navigation data. Thanks to the invention, the vehicle exits the freewheel mode, or does not enter it, before the vehicle arrives at an "event", which requires a reduction in the vehicle's speed.

[0012] Other characteristics of the present invention will appear clearly on reading the following description of a non-limiting embodiment thereof, with reference to the attached drawings.

[0013] [Fig.l] illustrates the proposed device.

[0014] [Fig.2] shows its operating principle.

[0015] [Fig.3A] illustrates the corrections made to the estimation of the distance between the vehicle and the event justifying the deactivation of the freewheel.

[0016] [Fig.3B] also.

[0017] [Fig.4] summarizes the strategy implemented.

[0018] Freewheel mode, or more simply "freewheeling", consists of opening the drivetrain (disengaging the engine) of the vehicle, when there is a demand for zero torque (for example when lifting the foot), in order to reduce or maintain the speed of the vehicle. In freewheeling, the engine brake is absent, which is appropriate when the driver wishes to maintain his speed, but less so when the driver wishes, or must, reduce his speed.

[0019] Hence the interest in predicting the exit from freewheeling, or strictly prohibiting it, in certain circumstances, in particular in anticipation of certain events, such as obstacles or changes in driving conditions identified in advance by a navigation system. This provides a predictive deactivation function, the aim of which is to optimize the deceleration of the vehicle when approaching events identified in advance. This function can impose an exit from freewheeling mode if it is active, or its prohibition if the vehicle is not in freewheel mode. It is transparent to the driver, and simply ensures that the powertrain is closed (engine engaged) before the vehicle arrives at the identified event.

[0020] The proposed device, illustrated by [Fig. 1], is a device for predictive deactivation of a vehicle freewheel mode preventing the opening of the input clutch which connects its drive motor with its kinematic chain. It comprises an on-board navigation system and a deactivation prediction module. The on-board navigation system informs the deactivation prediction module of the type of event detected, its distance D_ currmt, its arrival speed V_ event, and the average slope of the road between the vehicle and the event.

[0021] Based on this information, the prediction module decides whether or not freewheeling should be left or prohibited. The prediction module sends a deactivation request to a coordination module, which takes this request into account and transmits it to the relevant actuators of the vehicle, in particular its brakes and the controlled clutch.

[0022] The information transmitted by the navigation system to the prediction module relates to the event identified upstream: - the type of event identified, - its distance, - its speed of arrival on the vehicle, and - its slope.

[0023] The events taken into account are, without limitation, the following: a curve, single or multiple, a roundabout, a toll, a stop, a loss of priority, an intersection, a work zone, a traffic jam, a slope, a speed limit, etc. An event is therefore an “object” in the broad sense, which the vehicle may encounter on a road or a traffic lane, and which requires it to adapt its speed or change direction.

[0024] The prediction module is also informed of the vehicle speed V_ vs, and of the activated or inactive state of the freewheel. Finally, the device comprises a coordination module, imposing an instruction to exit or prohibit the freewheel mode, on the vehicle clutch.

[0025] As soon as a new event is identified by the navigation system, its “type” and its “arrival speed” are sent to the prediction module. Each type of event has a maximum distance D, beyond which the freewheel function cannot be deactivated by this method. For each identified event, a reference distance of the event D_ event, less than D, is determined, which depends on the current speed V_ vs of the vehicle.

[0026] The navigation system also determines a target speed of arrival of the vehicle at the event, or target speed of the event V_ event, depending on the type of event and the slope of the road leading to it. The target speed, or "speed of arrival of the event", V_ event, detects the need for deceleration relative to the current speed of the vehicle V_ vs. In summary, the need to close the clutch to have engine braking, is determined according to the distance of the event from the vehicle, and its speed of arrival at the event.

[0027] The deactivation of the freewheel mode is imposed if the distance D_ current between the vehicle and the detected event is smaller than the reference distance D_ event for the type of detected event, and if the current speed of the vehicle V_ vs is greater than the target arrival V_ event, also a function of the type of event. Thus, for example, if the target arrival speed at a roundabout is 40 km / h, but the vehicle is at 30 km / h, the freewheel function is not deactivated, because it is not necessary to slow down the vehicle.

[0028] If the actual distance between the vehicle and the event D_ current is smaller than the typical distance of the event D_ event, and the current speed of the vehicle V_vs is greater than the target speed of the event V_ event, then the prediction module sends a deactivation request to the coordination module, which delivers a deactivation request applied by the clutch actuator.

[0029] [Fig.2] illustrates the proposed predictive deactivation method. As indicated above, the freewheel mode forces the opening of the input clutch (which connects its drive motor with its kinematic chain) during a zero torque request. The deactivation of the freewheel mode interrupts or prohibits the forcing of opening of the clutch. If the vehicle is at a distance from the event smaller than the maximum distance and its current speed is greater than the target speed (D_ current < D, and V_ vs > V_ the freewheel is deactivated, so that the vehicle is engaged, from the moment the conditions are met, until the arrival of the event. This predictive deactivation makes it possible to anticipate the increase in the vehicle's braking requirement when approaching certain events, and to maximize the use of the freewheel mode, in a transparent manner for the driver.

[0030] The reference distance of the event D_ event depends on the current speed V_ vs of the vehicle, and on the average slope of the road, between the vehicle and the detected event. Correction factors C1, depending on the speed, and C2 depending on the slope, are applicable to the maximum deactivation distance D, to determine the reference distance of the event D_ event. These coefficients are illustrated in Figures 3A and 3B. They apply to the maximum deactivation distance specific to the type of event detected in front of the vehicle to determine the typical distance, or distance applicable reference distance D_ event: D_ evmt = D * Cl * C2. Thanks to these corrections, the typical distance of the event D_ event is reduced when the vehicle speed decreases, or with a positive slope (uphill). Conversely, it increases with a higher speed and a negative slope (downhill).

[0031] The algorithm of [Fig.4], groups together the entire strategy: - the type of event determines its maximum distance, - the current speed of the vehicle V_ Vs, determines the first correction factor Cl, - the slope of the road, determines the second correction factor C2, - the maximum distance is multiplied successively by Cl and C2, to calculate the distance of the event D_ event, - the typical distance of the event D_ event is compared to its actual distance D- current, - the current speed of the vehicle V_ vs is compared to the target speed of the event V_ evenh - if V_ ,, > V_ event, and if D_ event > D- current, the freewheel is deactivated.

[0032] In conclusion, the implementation of the method requires the presence of an on-board navigation system to deliver the necessary information, a prediction module, and a coordination module. The deactivation of the predictive function can be applied at the request of the real driver, or of a virtual driver, for example in a cruise control, driving assistance or autonomous driving system. Finally, its application is not limited to passenger vehicles, but is also of interest on heavy goods vehicles or coaches, having a freewheel mode, and a navigation system. The navigation system is responsible for identifying the most probable and most restrictive event over a given distance, in front of the vehicle.Finally, the permanent use of vehicle speed information and the road gradient allows the freewheel deactivation instruction to be instantly corrected to adapt to the braking needs felt by the driver.

Claims

Claims

1. Method for predictive deactivation of a vehicle freewheel mode forcing the opening of the input clutch which connects its drive motor with its kinematic chain, in which the exit from the freewheel mode or its prohibition is imposed on the vehicle by a prediction module deciding whether or not the freewheel must be left or prohibited in anticipation of events detected in advance by an on-board navigation system, for which the need to close the clutch is identified so as to anticipate the increase in the need for braking of the vehicle as they approach, characterized in that the deactivation of the freewheel mode is imposed on the vehicle if the distance (D_ cumnl) between the vehicle and the detected event is smaller than a reference distance (D_ evenl) depending on the type of detected event,and if the current speed of the vehicle (V_ vs) is greater than a target arrival speed (V_ eveM) also depending on the type of event and in that an instruction to exit freewheel mode is imposed on the vehicle clutch by a coordination module.,

2. Method for deactivating the freewheel mode according to claim 1, characterized in that the need to be able to close the clutch is determined as a function of the distance of the event from the vehicle, and its speed of arrival at the event.

3. Method for deactivating the freewheel mode, according to claim 1 or 2, characterized in that the reference distance of the event (D_ eveM) depends on the current speed (V_ vs) of the vehicle.

4. Method for deactivating the freewheel mode according to claim 1, 2 or 3, characterized in that the reference distance of the event (D_ evenl) depends on the average slope of the road, between the vehicle and the detected event.

5. Method for deactivating the freewheel mode according to claims 3 and 4, characterized in that a maximum deactivation distance (D) is determined for the type of event detected, which is corrected according to the current speed of the vehicle (V_ vs).

6. Deactivation method according to claim 5, characterized in that the maximum deactivation distance (D) for the type of event detected is corrected as a function of the slope of the road.

7. Device for predictive deactivation of the freewheel mode of a road vehicle forcing the opening of the input clutch which connects its drive motor with its kinematic chain, characterized in that it comprises a prediction module deciding whether or not the freewheel must be left or prohibited in anticipation of events detected in advance by an on-board navigation system, which informs the prediction module of the type of event detected, its distance (D_ currenl), its arrival speed (V_ evenl), and the average slope of the road between the vehicle and the event and in that said deactivation device comprises a coordination module, imposing on the clutch of the vehicle, an instruction to exit the freewheel mode.

8. Device for predictive deactivation of the freewheel mode according to claim 7, characterized in that the prediction module is also informed of the speed of the vehicle, and of the activated or inactivated state of the freewheel function (V_ vs).

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