GB2519866A

GB2519866A - Method for operating a grille of a vehicle, in particular a commercial vehicle

Info

Publication number: GB2519866A
Application number: GB1418694.4A
Authority: GB
Inventors: Ethan Ott; Michael Norlin
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2014-10-21
Filing date: 2014-10-21
Publication date: 2015-05-06
Also published as: GB201418694D0

Abstract

A method for operating a radiator grille of a vehicle, the grille comprising a driving device and at least one covering element which is movable by the driving device, between a closed position in which at least a portion of an air passage aperture is covered by the covering element, and at least one open position in which the portion of the air passage aperture is uncovered, the method comprising at least one of: at least one determining procedure (22) in which an operational state of at least one braking device is determined, wherein the covering element is moved on the basis of the determined operational state; and at least one delaying procedure (20, 26) which, when at least one criterion for effecting a movement of the covering element is met, determines a time period during which the criterion is met and, when the determined time period exceeds a predetermined threshold value, admits a movement of the covering element, the criterion relating to at least one operating parameter of the vehicle.

Description

Method for Operating a Grille of a Vehicle, in particular a Commercial Vehicle The invention relates to a method for operating a grille of a vehicle, in particular a commercial vehicle.

Vehicles such as commercial vehicles comprising grilles are well-known from the general prior art. Such a grille is also referred to as a radiator grille" which is, for example, configured to be arranged in front of at least one heat exchanger of the vehicle. For example, the grille is configured to be arranged at least partially in an air passage aperture through which air can flow due to a forward movement of the vehicle. In other words, the grille can provide air flow so that air can flow against and around the heat exchanger arranged behind the grille with respect to the longitudinal direction of the vehicle.

For example, the heat exchanger serves to cool a fluid due to a heat transfer from the fluid via the heat exchanger to the air flowing around the heat exchanger. This means the fluid can flow through the heat exchanger thereby transferring heat via the heat exchanger to the air flowing around the heat exchanger.

The fluid can be configured as a liquid or a gas. For example, the fluid is a coolant and used to cool an engine of the vehicle. Alternatively or additionally, the coolant can be used to cool at least one electrical component of the vehicle. Moreover, the fluid can be a refrigerant used by an air conditioning system to cool air to be guided into an interior of the vehicle.

The grille comprises a driving device and at least one covering element which is, for example, a grille bar. The covering element is movable by the driving device between a closed position and at least one open position. In the closed position, at least a portion of said air passage aperture is covered by the covering element. In the open position, the portion of the air passage aperture is uncovered. Thus, in the closed position, air cannot flow through the portion of the air passage aperture. However, in the open position, air can flow through the portion.

A smooth and sealed front vehicle surface is generally desirable to achieve reduced aerodynamic drag. However, a trade-off exists with the reduction in air flow through the air passage aperture when the front grille surface is closed. It is desirable to provide a method to determine an advantageous position of the covering element whereby necessary cooling airflow is achieved for current operating conditions while the maximum aerodynamic and minimal parasitic energy consumption is achieved. Additional, the method should be an active grille control algorithm which accounts for safety and service related concerns.

US 7,784,576 B2 shows a method of controlling the flow of air through at least one vehicle opening, the at least one vehicle opening comprising at least one of a grille opening and a bumper opening. In said method, at least one vehicle operating parameter is sensed. At least one parameter representing signal is provided on a data bus, the signal representing the at least one vehicle operating parameter. It is determined from the at least one parameter representing signal whether an adjustment in the extent to which the at least one opening is open to the airflow to be made in response to the at least one signal. A control signal is provided on the data bus to cause the adjustment of the extent to which the at least one opening is open in the event the act of determining indicates that an adjustment is to be made.

Therein, the sensed at least one vehicle operating parameter comprises the vehicle speed and at least one additional vehicle operating parameter. Moreover, the at least one opening is controlled to be closed substantially continuously while the vehicle speed is above a threshold speed and at least one additional vehicle operating parameter and at least one environmental condition in which the vehicle is operated are not at respective conditions indicating that the opening should not be closed.

It is an object of the present invention to provide a method for operating a grille of a vehicle, by means of which method a particularly efficient operation of the vehicle can be realized.

This object is solved by a method having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are indicated in the other patent claims.

The invention relates to a method for operating a grille of a vehicle, the grille comprising a driving device and at least one covering element which is movable by the driving device between a closed position and at least one open position. In the closed position, at least a portion of an air passage aperture is covered by the covering element. In the open position, said portion of the air passage aperture is uncovered so that air can flow through the portion. In the closed position, air cannot flow through the portion since the airflow through the portion is blocked by the closed covering element.

The method according to the present invention comprises a determining procedure in which an operational state of at least one braking device is determined, wherein the covering element is moved on the basis of the determined operational state. Alternatively or additionally, the method according to the present invention comprises a delaying procedure which, when at least one criterion for effecting a movement of the covering element is met, determines a time period during which the criterion is met and, when the determined time period exceeds a predetermining threshold value, admits a movement of the covering element, the criterion relating to at least one operating parameter of the vehicle.

For example, the braking device is a retarder coupled with an output shaft of an engine of the vehicle, the engine being configured to drive the vehicle. For example, the engine is an internal combustion engine, wherein the output shaft is a crankshaft of the internal combustion engine. For example, said criterion is met when the retarder is activated thereby braking the engine and, thus, the vehicle. Since the method comprises the delaying procedure, the covering element is not moved immediately in response of the activation of the retarder, but the delaying procedure determines the time period during which the retarder is activated. When said time period exceeds the predetermined threshold value, the movement of the covering element is effected. Thereby, there is a predetermined time period between the activation of the retarder and the actual movement of the covering element so that rapid cycling of the covering element can be prevented. This means the delaying procedure provides a time delay between opening and closing of the covering element to prevent rapid cycling.

Alternatively or additionally, by considering the operational state of the braking device, the braking device can be supported in braking the vehicle by opening the covering element.

Thereby, drag is increased which helps brake the vehicle. For example, the braking device is an engine brake which can be configured as, for example, an exhaust brake and/or ajake brake which is also referred to as a "decompression brake".

Preferably, the operating parameter indicates the operational state of the braking device.

Moreover, the operating parameter can be a fan speed and/or a vehicle speed and/or a coolant temperature.

By considering the operational state of the at least one braking device and/or by delaying the movement of the covering element by means of the delaying procedure, a particularly efficient operation of the vehicle can be realized since necessary cooling air flow for current operating conditions as well as maximum aerodynamic and minimal parasitic energy consumption can be achieved.

For example, a request for opening the covering element can be generated whenever any of the following are true: -A fan speed request generated by a thermal management control strategy is above a defined threshold. A grille control interprets the fan speed request as an indication for the requested amount of airflow through the portion and, for example, a cooling package comprising at least one heat exchanger. If the request exceeds a defined threshold, the covering element is opened to assist in providing the requested flow.

-Engine retarder torque has been higher than in defined threshold for a defined amount of time. When the engine retarder is activated the goal is to provide additional braking drag on the vehicle. Under these conditions the covering element shall open to increase the level of aerodynamic drag to assist with the braking. Additional airflow under these conditions may also provide thermal dynamic benefits, e.g. lower charge air cooler temperatures which improve braking performance.

-Vehicle speed has been below a defined threshold for defined amount of time. At low vehicle speeds the effect of reduced aerodynamic drag is greatly decreased.

Therefore, the benefit of a closed grille or covering element is significantly reduced.

Opening the grille of the covering element at low speeds anticipates the common need for a total cooling package airflow equivalent to or greater than the grille open vehicle speed free airflow.

A request for closing the grille or the covering element is generated whenever any of the following are true: -There is no active open grille request. Requests for opening the grille shall take priority, except when a temperature of a coolant to be cooled by the cooling package is low as described below. Priority is given because the open grille or covering element state is more conservative than closed and is a desirable fail-safe condition.

-The engine coolant temperature is below a defined threshold and the vehicle speed is above a defined threshold. Optimal engine efficiency is achieved when the coolant temperature is in a certain range. If too cold, additional energy is lost to factors such as friction, poor combustion, and heat transfer. If too hot, potential mechanical damage can occur. Operating with the grille or the covering element closed when the coolant temperature is below a threshold reduces the airflow through the radiator and engine compartment and aids in speeding up the warm-up process so that the engine more quickly reaches the optimal coolant temperature. The grille shall be open when the vehicle speed is low (regardless of coolant temperature) so that the grille will never close when the vehicle is stationary and there is a chance for a portion to be caught in a grille mechanism.

A signal will be sent to the driving device which comprises, for example, the mechanical grille mechanism, triggering the grille or the covering element to close when the request for closing the covering element has been present for a defined amount of time and a driver operated switch is in an enable position. A signal will be sent to open the grille or covering element (or the close signal reversed) during initial vehicle key-on, whenever the driver operated switch is in a disable position or whenever there has been no grille close request for a defined amount of time.

Further advantages, features, and details of the invention derive from the following description of a preferred embodiment as well as from the drawings. The features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed in the respective indicated combination but also in any other combination are taken alone without leaving the scope of the invention.

The drawings show in: Fig. 1 a flow diagram of a method for operating a grille of a vehicle, the method comprising a determining procedure and a delaying procedure; Fig. 2 a further flow diagram illustrating the method; and Fig. 3 a flow diagram illustrating the method in which a fan is operated on the basis of an operational state of the grille.

In the figures the same elements or elements having the same functions are indicated with the same reference signs.

Fig. 1 shows a flow diagram illustrating a method for operating a grille of a vehicle, in particular a commercial vehicle such as a truck. For example, the grille is arranged in front of at least one heat exchanger of the vehicle with respect to the longitudinal direction of the vehicle. For example, the grille is arranged in front of a heat exchanger unit which is also referred to as a "cooling package", the heat exchanger unit comprising a plurality of heat exchangers. For example, the heat exchangers overlap each other and serve to cool fluids flowing through the heat exchangers. For example, one of said heat exchangers serves to cool at least one component of a power drain and/or at least electrical component of the vehicle. Said component of the power drain can be an engine, which is, for example, configured as an internal combustion engine. Therein, the fluid used to cool the engine is also referred to as a coolant" or an "engine coolant". The vehicle comprises a driver's cab and an engine compartment arranged in front of the driver's cab with respect the longitudinal direction of the vehicle. The engine compartment is covered by an engine hood at least partially, wherein the engine is arranged in the engine compartment, the engine serving to drive the truck.

Alternatively or additionally, at least one of said heat exchangers can be part of an air conditioning system configured to supply the interior of the driver's cab with cooled air.

The respective fluid flowing through the respective heat exchanger can be cooled by a heat transfer from the fluid via the respective heat exchanger to air flows and against and around the respective heat exchanger. Thus, the airflow can be affected by forward movement of the vehicle. In other words, air flowing around and against the respective heat exchanger when the vehicle moves forward.

For example, the grille is arranged in an air passage aperture of the engine hood. The air passage aperture is an air inlet through which air can flow so that the heat exchanger arranged behind the grille and the air passage aperture can be supplied with air flowing through the air passage aperture.

The grille comprises a plurality of covering elements in the form of grille bars which are, for example, inherently stable. The grille bars extend in the transverse direction of the vehicle and are arranged on top of each other in relation to the vertical direction of the vehicle. The grille further comprises lateral mounting elements on which the grille bars are mounted. For example, the grille bars are attached to the engine hood by the mounting elements. The grille is designed as an active grille in which the grille bars (covering elements) are movable between a closed position and at least one open position. In the closed position, a first portion of the air passage aperture is closed or covered by the grille bars. Thereby, air cannot flow through the first portion. In the open position, the first portion is uncovered so that air can flow through the first portion to the heat exchangers when the vehicle moves forward.

The grille further comprises a driving device having a mechanical grille mechanism, wherein the grille bars (covering elements) can be moved by means of the driving device.

For example, the driving device comprises at least one motor which can be configured as an electric motor, the motor being capable of moving the respective grille bars between the open position and the closed position.

For example, the grille bars are pivotable about respective pivot axes between the closed position and the open position, the respective pivot axes extending at least substantially the transverse direction of the vehicle. Each of the grille bars has, for example, shafts on either side near its leading edge that it rotates on, wherein the respective grille bar is pivotably mounted on the mounting elements via said lateral shafts. Thus, the respective grille bars can pivot about the pivot axes relative to the mounting elements. The respective shafts attached to the grille bars are pivotably supported on the respective mounting elements via, for example, nylon bushings.

The method illustrated in Fig. 1 serves to realize a particularly efficient operation of the vehicle since, by means of the method, optimal positions for the respective grille bars for current operating conditions can be determined. In other words, the method is a control algorithm used to control the grille bars on the basis of sensed conditions or parameters as will be described in the following. In Fig. 1, at block 10, the method or control algorithm starts. At block 12, for reference purposes, the covering elements are opened. At block 14, a determination is made as to whether a speed of the vehicle exceeds a predeterminable threshold value. If the answer at block 14 is no (N), block 16 is reached.

If the answer at block 14 is yes (Y), a yes branch from block 14 is followed to block 18.

At block 16 a determination is made as to whether a fan speed request exceeds a predetermined threshold value. This means the vehicle comprises at least one fan configured to convey air through the heat exchangers. The fan speed request corresponds to a request for air. If the answer at block 16 is yes, block 20 is reached. If the answer at block 16 is no, a no branch from block 16 is followed to block 22. At block 22, a determination is made as to whether an engine retarder is active. Such an engine retarder is a braking device of the vehicle, the engine retarder being connected to an output shaft of the engine. If the engine retarder is active or activated, the engine and, thus, the vehicle are braked or decelerated by means of the braking device. If the answer at block 22 is yes, a yes branch from block 22 is followed and block 20 is reached. If the answer at block 22 is no, a no branch from block 22 is followed to block 24. At block 24, a determination is made as to whether a speed of the vehicle is below a predetermined threshold value. If the answer at block 24 is yes, block 20 is reached. If the answer at block 24 is no, block 26 is reached.

At block 18, a determination is made as to whether a temperature of the coolant for cooling the engine is below a predetermined threshold value. If the answer at block 18 is no, a no branch from block 18 is followed and block 16 is reached. If the answer at block iBis yes, block 26 is reached.

At block 20, a grille open request timer is incremented and a grille close request timer is set to zero. After that, block 28 is reached wherein it is determined whether the grille open request timer exceeds a predetermined threshold value. If the answer at block 28 is no, block 14 is reached again. If the answer at block 28 is yes, block 32 is reached and the grille bars (covering elements) are opened, i.e. moved in the open position or the grille bars stay in the open position.

At block 26, a grille close request timer is incremented and the grille open request timer is set to zero. After that, block 30 is reached in which it is determined whether the grille close request timer exceeds a predetermined threshold value. If the answer at block 30 is no, block 14 is reached again. If the answer at block 30 is yes, block 34 is reached in which the covering elements are moved into the closed position or stay in the closed position.

As can be seen from Fig. 1, blocks 14, 16, 18, 22 and 24 indicate criterions on the basis of which the grille bars are moved when the respective criterions are met. Said criterions relate to respective operating parameters such as the fan speed request, the operational state of the engine retarder, the vehicle speed and the coolant temperature. Blocks 20 and 26 form a delaying procedure which, when the respective criterions for effecting a movement of the grille bars are met, determines a time period during which the criterions are met and, when a determined time period exceeds a predetermined threshold value, admits a movement of the grille bars. Thereby, rapid cycling, i.e. a high number of subsequent opening and closing movements of the grille bars can be prevented.

Moreover, by considering the operational states of the braking device in the form of the engine retarder, the engine retarder can be supported in braking the vehicle by, for example, opening the grille bars, so that drag increases thereby braking the vehicle.

The disclosed grille control algorithm relies on at least one signal representing the requested fan speed from the engine's thermal management algorithm and is able to delay or modify this signal before it is sent to a fan control mechanism shown in Fig. 2. In this way, a grille control algorithm for controlling the grille can determine whether or not activation of the fan is allowed. Fig. 3 shows a fan allow algorithm which starts at respective blocks 36 and 38.

After block 36, block 40 is reached in which it is determined whether the fan request speed exceeds a first predetermined threshold THD [A]. If the answer at block 40 is yes, a yes branch from block 40 is followed to block 42. If the answer at block 40 is no, block 44 is reached. At block 44 a determination is made as to whether the fan request speed exceeds a second predetermined threshold value THD [B]. If the answer at block 44 is yes, block 46 is reached. If the answer at block 44 is no, a no branch from block 44 is followed to block 48 in which a fan request timer is set to zero. After block 48, block 50 is reached in which it is determined that the activation of the fan is not allowed.

At block 46 a determination is made as to whether the fan request speed is trending down. If the answer at block 46 is yes, a yes branch of block 46 is followed to block 48. If the answer at block 46 is no, block 52 is reached in which the fan request timer is incremented. After block 52, block 54 is reached in which it is determined whether the fan request timer exceeds a predetermined threshold value. If the answer at block 54 is no, block 50 is reached. lithe answer at block 54 is yes, a yes branch from block 54 is followed to block 42. At block 42 a determination is made as to whether the grille bars are open. If the answer at block 42 is no, block 50 is reached. lithe answer at block 42 is yes, a yes branch from block 42 is followed to block 56 in which it is determined that the activation of the fan is allowed.

After block 38, block 58 is reached in which the grille bars are open, the activation of the fan is allowed and there is no request. When the grille bars are closed, block 60 is reached in which the grille bars are closed, the activation of the fan is not allowed and there is no request. From block 60, block 58 is reached when the grille bars are open and the fan request speed is below the second threshold value THD [B].

Generally, the fan speed request from the thermal management algorithm is a proxy for the required amount of airflow through the cooling package to balance the thermal loads.

When additional airflow is required, the requested fan speed will increase. Another way of increasing the airflow through the cooling package is to open the grille bars. Depending on physical configuration, this may provide twice the airflow through the cooling package compared to the close grille. When an active request for fan operation is received from the thermal management algorithm, the grille control system can first open the grille bars to provide additional airflow to the cooling system and not allow the fan request to go to the fan control mechanism. If this additional airflow is sufficient to meet the cooling needs, the requested fan speed from the thermal management algorithm should trend downward as the temperatures decrease. However, if the additional airflow is insufficient and the fan speed request continues to increase above the defined first threshold THD [A] or it persists at a moderate level which is greater than the second threshold value THD [B] for some amount of time, fan activation shall be allowed. Additionally, if the grille bars are already open due to operating conditions other than a fan request at the time when a fan request (fan speed request) becomes active, the fan request will immediately be allowed.

Compared to conventional systems, the disclosed solution offers a several benefits.

Because the proposed grille control algorithm reacts on a requested fan speed from the thermal management system, the number of input signals required is greatly reduced.

Additionally, using the requested fan speed reduces the number of parameters necessary for calibrating the grille control system and allows it to operate relative to the settings specified for the thermal management system. For example, it is not necessary to specify cooling temperature thresholds where the grille will open and close because the requested fan speed is already based on critical coolant temperature limits. Further, if the fan activation limits are modified within the thermal management system, the grille control will automatically be adjusted.

Delaying the fan activation allows for the maximum time with the closed grille aerodynamic benefit and minimizes the energy used by the fan. The logic within the fan-allow algorithm detects the ending of an active cooling event by noting when the fan request is low and decreasing. Under these conditions it is likely the passive airflow is sufficient for cooling the system and that the fan is not actually required. Under these conditions the fan will be disabled, saving the energy which otherwise would have been used and improving overall the economy of the vehicle. Additionally, the proposed solution introduces time delays between opening and closing of the grille bars to prevent rapid cycling which can cause thermal system instability and mechanical fatigue. It also provides conditions for opening the grille during engine braking to increase drag. This can improve a vehicle's ability to maintain a target speed on a steep downhill and may reduce the wear on service brakes.

List of references block 12 block 14 block 16 block 18 block block 22 block 24 block 26 block 28 block block 32 block 34 block 36 block 36 block block 42 block 44 block 46 block 48 block block 52 block 54 block 56 block 58 block block

Claims

Claims A method for operating a grille of a vehicle, the grille comprising a driving device and at least one covering element which is movable by the driving device, between a closed position in which at least a portion of an air passage aperture is covered by the covering element, and at least one open position in which the portion of the air passage aperture is uncovered, the method comprising at least one of: -at least one determining procedure (22) in which an operational state of at least one braking device is determined, wherein the covering element is moved on the basis of the determined operational state; and -at least one delaying procedure (20, 26) which, when at least one criterion for effecting a movement of the covering element is met, determines a time period during which the criterion is met and, when the determined time period exceeds a predetermined threshold value, admits a movement of the covering element, the criterion relating to at least one operating parameter of the vehicle.
2. The method according to claim 1, characterized in that the breaking device is a retarder coupled with an output shaft of an engine of the vehicle.
3. The method according to any one of claims 1 or 2, characterized in that the braking device is an engine break.
4. The method according to any one of the preceding claims, characterized in that the operating parameter indicates the operational state of the breaking device.
5. The method according to any one of the preceding claims, characterized in that the operating parameter is a tan speed and/or a vehicle speed and/or a coolant temperature.