DE102012204596A1 - Method and device for regulating the speed of a motor vehicle - Google Patents

Abstract

In a method for regulating the speed of a motor vehicle, a current fuel consumption FCact of the motor vehicle is determined and the speed of the motor vehicle is controlled by intervention in an engine control to maintain a predefinable fuel consumption target value FCsetpoint, wherein a minimum speed vmin can be predetermined, which is maintained at least. The invention also relates to a device for controlling the speed of a motor vehicle.

Description

The invention relates to a method and a device for regulating the speed of a motor vehicle.

To increase the comfort and relieve the driver, motor vehicles are nowadays often equipped with speed controls. In this case, a respective current speed of the motor vehicle is determined and intervened upon detection of a deviation from a predefinable setpoint speed in the engine control to minimize the deviation. Such speed controls are usually designed to keep the speed of the motor vehicle as constant as possible at the desired speed, regardless of external conditions, such as inclines, inclines, wind conditions or the nature of the road surface. However, this often results in increased fuel consumption.

In order to control an engine of a vehicle so that it consumes as little energy as possible in the DE 10 2010 018 335 A1 proposed a cruise control system whose control is designed so that it keeps the speed of the vehicle at an adjustable target speed, provided that the power output of the vehicle engine does not exceed an adjustable maximum target power, and if necessary, the speed of the vehicle so far reduced that the maximum Target power is not exceeded. As a result, however, a reduction in fuel consumption is achieved only to a limited extent.

For motor vehicles with hybrid drive is in the EP 2 010 423 B1 a speed control apparatus is described, wherein the controller is adapted to calculate a target acceleration of the vehicle within a range of permissible target accelerations, wherein the upper limit for the acceleration is set so that the required drive power can be provided by the electric drive. As a result, it can be achieved in a hybrid motor vehicle that the internal combustion engine does not need to leave its optimum operating point. This method is not applicable to motor vehicles without hybrid drive.

According to the EP 1 888 900 B1 For example, an actual value of the fuel consumption of a motor vehicle is detected, a value of the fuel consumption is given to a fuel consumption regulator as the target value, and the actual value of the fuel consumption is used to control the adjustment of the engine output. In one mode, the fuel consumption value is an upper limit, and a set speed is maintained if the predetermined fuel consumption value is not exceeded. However, it has been shown that such a regulation with a fuel consumption value as desired value in certain situations can lead to undesirable reactions of the motor vehicle, which complicate the operability of the motor vehicle.

It is therefore an object of the present invention to provide a method and an apparatus for controlling the speed of a motor vehicle, wherein the above-mentioned disadvantages are avoided. In particular, it is an object of the present invention to provide a method and a device of the type mentioned, wherein both a reduction in fuel consumption and pollutant emissions and an increase in the ease of use or traffic safety are possible.

This object is achieved by a method and by a device as specified in the independent claims.

The inventive method for controlling the speed of a motor vehicle relates in particular to motor vehicles with a drive motor which is designed as an internal combustion engine, for example as a gasoline or diesel engine.

In each case a current fuel consumption of the motor vehicle is determined. Methods for determining the fuel consumption as from the signal of a flow and / or a pressure sensor or from a map of the engine are known per se. By the term "fuel consumption" is meant here and below a distance-related fuel consumption, for example given in liters per 100 km, which can be determined for example from a time-related fuel consumption by taking into account the detectable via a speed sensor current speed of the motor vehicle.

By engaging in an engine control of the motor vehicle, the speed of the motor vehicle is regulated in accordance with the invention in such a way that a predefinable fuel consumption target value is maintained as far as possible. For this purpose, the deviation of the current fuel consumption from the fuel consumption target value can be determined and the speed of the motor vehicle can be adjusted to minimize the deviation. Since, as a rule, at least above a lower limit speed, the fuel consumption increases with increasing speed, in particular when the fuel consumption target value is exceeded, a reduction of the speed and an undershooting of the fuel consumption desired value causes an increase in the speed. For this purpose, an intervention in the engine control, the corresponds to a reduced or increased operating angle of the accelerator pedal.

According to the invention, a minimum speed of the motor vehicle can be predetermined, which is at least maintained. Thus, to maintain the minimum speed, if necessary, a higher actual fuel consumption than the fuel consumption target value is allowed.

Because a minimum speed can be predetermined, which is at least held independent of fuel consumption, a drop in the speed of the motor vehicle below the minimum speed can also be avoided in situations that increase consumption significantly, for example on a steep incline or in strong head wind. This makes both an improvement in the usability of the motor vehicle and an increase in traffic safety possible. In particular, this can avoid an unexpected behavior of the motor vehicle, which differs substantially from the behavior that would be chosen by a driver of the motor vehicle due to the situation. In this way, a low fuel consumption with high ride comfort can be achieved.

According to a preferred embodiment of the invention, a consumption-independent regulation of the speed of the motor vehicle to the predetermined minimum speed in the event that the current fuel consumption of the motor vehicle exceeds the fuel consumption setpoint even when the speed drops to the minimum speed. In particular, in cases where, for example, due to an increase in fuel consumption increases and the speed of the motor vehicle is therefore reduced to maintain the fuel consumption setpoint, then engages when the minimum speed is reached, a speed control on the minimum speed. Such a speed control, in which the deviation is detected by the minimum speed set in this case as a set speed and is minimized by intervention in the engine control, is known per se. In this way, a particularly comfortable behavior of the motor vehicle can be achieved and at the same time avoided that the minimum speed is exceeded. Depending on the design of the speed control, it may also be permissible that the minimum speed is undershot by one control deviation. As soon as the current fuel consumption falls below the fuel consumption setpoint in the regulation to the minimum speed, the consumption-independent control is terminated to the minimum speed, and the speed of the motor vehicle is increased to maintain the fuel consumption setpoint.

According to a preferred embodiment of the invention, not only a minimum speed, but also a maximum speed can be predetermined, which is kept at most independent of the current fuel consumption. As a result, a further improvement of the operability and traffic safety of the motor vehicle is made possible.

In particular, it is advantageously provided that when the current fuel consumption at the maximum speed falls below the fuel consumption target value, the speed is regulated to the maximum speed. Thus, if the current fuel consumption of the motor vehicle is particularly low, for example, on a downslope or with strong tailwind, the speed of the motor vehicle is regulated such that the maximum speed is not exceeded or, depending on the design of the control, at most by one control deviation. In this way, an unexpected increase in the speed of the motor vehicle in such situations can be avoided, whereby the operability and road safety of the motor vehicle are further improved.

According to a particularly preferred embodiment of the invention, the minimum speed can be predetermined as a function of the maximum speed. It can thus be provided, for example, that the maximum speed is predetermined, for example by manual input of the driver or by actuation of an operating element for taking over a current speed as the maximum speed, and the minimum speed as a function of the maximum speed, for example in a fixed ratio to the maximum speed determined is. In particular, the minimum speed may be about 80% of the maximum speed. It has been found that in this way a particularly simple and safe operation of the motor vehicle can be made possible, which can correspond in particular to a conventional cruise control system.

Furthermore, it is preferable that the fuel consumption target value is specified at a start time. The start time can be in particular the time of specification of the maximum speed. In particular, the fuel consumption target value can be determined from a current consumption at the start time and can for example be equal to the current consumption at the start time. As a result, the feasibility of the method according to the invention and thus the operability of the motor vehicle is further improved.

As current fuel consumption, for example, the instantaneous fuel consumption can be used, in particular from a Sensor signal or from a map can be determined based on the current operating parameters of the engine, including the instantaneous speed of the motor vehicle. However, the respective current fuel consumption is preferably determined from a current fuel consumption of the motor vehicle averaged over a minimum time or a minimum driving distance. As a result, not only measurement inaccuracies can be compensated, but it can also, if the motor vehicle is temporarily in a deceleration or acceleration phase at the start time, a fuel consumption target value suitable for the control can be determined.

An inventive device for regulating the speed of a motor vehicle comprises data acquisition means for acquiring data at least on the current fuel consumption and the current speed of the motor vehicle. Furthermore, the device according to the invention comprises input means for inputting a fuel consumption setpoint or establishing a start time, to which a desired value of the fuel consumption and possibly a minimum speed are taken or set. The device according to the invention further comprises processor means, which are set up to determine a manipulated variable for maintaining the fuel consumption setpoint and consumption-independent for maintaining the minimum speed, and actuator means for corresponding intervention in the engine control. The device according to the invention is designed in particular for carrying out the above-described method for regulating the speed of the motor vehicle.

The invention will be explained in more detail by way of example with reference to the drawing.

It shows:

1 an embodiment of a method according to the invention as a flowchart.

How out 1 can be seen, the inventive method for controlling the speed of a motor vehicle is activated at a start time, such as by operating an actuator by the driver. At this time, the maximum speed v _max and the fuel consumption target value FC _{soll are} set, for example, the instantaneous speed of the motor vehicle is taken as the maximum speed v _max and the current fuel consumption FC _{act of} the motor vehicle as a target fuel consumption FC _should . For this purpose, in particular the current speed v _{act of} the motor vehicle is detected continuously; Likewise, the current fuel consumption FC _{act of} the motor vehicle is continuously detected, for example by averaging a continuously detected instantaneous fuel consumption over a predefinable time span or driving distance. The data necessary for this purpose are usually already present in the context of other systems of the motor vehicle, for example in a motor vehicle information system or in a travel computer.

Furthermore, a minimum speed v _{min is} set, for example as 80% of the maximum speed v _max or the current speed at the start time. It may be provided that a different, higher or lower percentage of the maximum speed is specified as the minimum speed, or that the minimum speed otherwise depends on the maximum speed.

The current fuel consumption FC _act is now compared with the predetermined fuel consumption target value FC _soll . If the current fuel consumption FC _{act is} not greater than the nominal value FC _{soll of} the fuel consumption, then it is determined whether the current speed v _{act is} greater than or less than the maximum speed v _max or equal thereto. If the current speed v _{act is} less than the maximum speed v _max , which in this case is used as the setpoint of a speed control loop, the engine power is increased by increasing the manipulated variable α _t , which represents the operating angle of the accelerator pedal. For this purpose, α _{t is} increased by a predetermined increment. If, on the other hand, the current speed v _{act is} greater than the maximum speed v _max , then α _t is reduced by one increment. If the described speed control method has not been completed, as well as in the case that the current speed v _{act is} equal to the maximum speed v _max , a comparison of the current fuel consumption FC _act with the fuel consumption setpoint FC _soll takes place again.

If the current fuel consumption FC _{act is} greater than the fuel consumption target value FC _soll , then it is determined whether the current speed v _{act is} less than or greater than the minimum speed v _min . If the current speed v _{act is} below the minimum speed v _min , which in this case serves as the setpoint of a speed control loop, then α _{t is} increased by one increment so that the increased power output of the motor caused thereby increases the speed to reach the minimum speed v _min . On the other hand, if the actual speed v _{act is} greater than the minimum speed v _min , then α _t is lowered by one increment. This reduces the speed of the motor vehicle and the current fuel consumption FC _act decreases. If the described control method is not finished, as well as in the case that the current speed v _{act is} already the Minimum speed v corresponds to _min , a new comparison of the current fuel consumption FC _act with the target value FC _should fuel consumption.

The speed of the motor vehicle is thus regulated to maintain the fuel consumption target value FC _soll between the minimum speed v _min and the maximum speed v _max . When the maximum speed v _max is reached, the current speed v _{act is} regulated to the maximum speed v _max , wherein the current fuel consumption FC _{act may be} less than the setpoint value FC _{soll of} the fuel consumption; when the minimum speed v _min is reached, the current speed v _{act is} regulated to the minimum speed v _min , whereby an increase in the fuel consumption FC _act above the setpoint FC _{soll is} also accepted.

Depending on the situation, in particular depending on the increase or decrease in the slope, the counterwind or tailwind or the change of other fuel consumption influencing factors, despite an increase of α _t, the current speed v _{act may} remain constant or even continue to decrease, or vice versa a reduction of α _t, the current speed v _act remain unchanged or continue to increase. In this case, in the next comparison of the actual fuel consumption FC _act with the desired value FC _{soll of} the fuel consumption, a correspondingly increased or unchanged deviation of the actual speed v _act from the maximum speed v _max or the minimum speed v _{min will be} determined. Such an increase of the deviation may be permissible as a control deviation. However, the control loop can also be designed such that, depending on the size of the deviation, the manipulated variable α _{t is changed} by a different large increment. Furthermore, further known refinements of the speed or fuel consumption control, for example as a PID controller, are possible.

The exemplary described invention automatic Geschwindigkeitsbzw. Fuel consumption control may be activated in a manner similar to known speed controls by actuating a corresponding actuator, thereby automatically setting the fuel consumption target FC _soll , the maximum speed v _max and the minimum speed v _min . The described control method can be deactivated by actuating a corresponding actuating element by the driver; Preferably, it is provided that the control method according to the invention by pressing the brake pedal, possibly also by pressing the accelerator pedal is terminated.

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 102010018335 A1 [0003]
• EP 2010423 B1 [0004]
• EP 1888900 B1 [0005]

Claims (10)

Method for controlling the speed of a motor vehicle, wherein a current fuel consumption FC _{act of} the motor vehicle is determined and the speed of the motor vehicle _is controlled by intervention in an engine control to maintain a predefinable fuel consumption target value FC _soll , characterized in that a minimum speed v _{min can be} predetermined at least held. Method according to Claim 1, characterized in that, when the current fuel consumption FC _act exceeds the fuel consumption setpoint FC _soll when the minimum speed v _{min is reached} , the current speed v _{act is} regulated to the minimum speed v _min . A method according to claim 2, characterized in that a maximum speed v _{max can be} predetermined, which is held at most. Method according to claim 2 or 3, characterized in that, when the current fuel consumption FC _{act falls} below the fuel consumption setpoint FC _soll when the maximum speed v _{max is reached} , then the current speed v _{act is} regulated to the maximum speed v _max . Method according to Claim 2 or 3, characterized in that the minimum speed v _{min is} predetermined as a function of the maximum speed v _max . Method according to one of the preceding claims, characterized in that the minimum speed v _{min is} 80% of the maximum speed v _max . Method according to the preceding claim, characterized in that the fuel consumption target value FC _{is set} to a start time. A method according to claim 6 or 7, characterized in that the fuel consumption target value FC _{is determined} from the current fuel consumption FC _act at the start time. Method according to one of the preceding claims, characterized in that the current fuel consumption FC _{act is determined} from an averaged over a minimum time period and / or a minimum driving distance average fuel consumption. Device for controlling the speed of a motor vehicle, comprising data acquisition means for detecting at least one current fuel consumption FC _act and a current speed v _{act of} the motor vehicle, input means for inputting a fuel consumption target value FC _soll and / or establishing a start time for taking over the fuel consumption target value FC _soll and a minimum speed v _min , processor means arranged to determine a manipulated variable for maintaining the fuel consumption target value FC _{soll, but} at least the minimum speed v _{min are} set, and actuator means for engagement according to the determined manipulated variable in the engine control.

Images