AT515605A1 - Method for operating a motor vehicle - Google Patents

Abstract

The invention relates to a method for operating a motor vehicle having a manual transmission and an internal combustion engine as an engine, wherein the transmission is connected to a transmission control unit and the prime mover to an engine control unit. In order to keep the calibration effort for the gear selection as low as possible, it is provided that the accelerator pedal position (x) is evaluated on a single - preferably the engine control unit and the transmission control unit parent - instance, the accelerator pedal position is interpreted as an acceleration request that to fulfill the acceleration request necessary drive torque, preferably by a pilot control unit and / or an acceleration controller, is determined, wherein the necessary drive torque is converted into a target engine torque of the engine for each gear, and that - based on the acceleration request - a consumption optimal and / or low-emission combination of engine torque and gear is selected on the basis of at least one fuel characteristic map or pollutant map.

Description

The invention relates to a method for operating a motor vehicle having a manual transmission and an internal combustion engine as a drive machine, wherein the transmission with a transmission control unit and the prime mover is connected to an engine control unit.

In known gear selection strategies, the accelerator pedal position in the engine control unit is interpreted as an engine torque request. Different accelerator pedal maps define the engine setpoint depending on the accelerator pedal position and the engine speed. The accelerator pedal position is used in the transmission control unit for gear selection. Switching processes are triggered with the help of different shift maps. Each shift map consists of shift characteristics that define a speed for a shift up or down depending on the accelerator pedal position. The position of the accelerator pedal is thus interpreted twice and independently of each other both by the engine control unit, as well as by the transmission control unit.

A shift strategy with shift characteristics and a shift characteristic adaptation based on the actual travel resistance is known, for example, from US Pat. No. 6,067,495 A or DE 42 40 762 A1. US 4,972,737 A describes a similar shift / driving strategy, wherein it is shown that the accelerator pedal positions in the engine control unit and in the transmission control unit are interpreted separately.

Previous gear selection strategies have the disadvantage that a high number of calibration parameters is required. Typically, at least 12 values must be calibrated per switching characteristic. Each switching characteristic requires at least two switching characteristics. For each driving program (for example normal, uphill,

Downhill, Trailer, Winter, Sport, Manual, "Warmup", "Stop & Go") a separate shift map is required, which - depending on the driving situation (sportiness detection, driving resistance, ...) between the switching maps must be changed. Furthermore, the necessary to achieve a sovereign acceleration tuning the shift maps to the accelerator pedal map and the adjustment of the accelerator pedal maps is complex. The entire shift strategy calibration applies only to a defined accelerator pedal map. With several accelerator maps, correspondingly more calibration parameters are necessary. In addition, accelerator maps are often varied to achieve a different vehicle characteristics. As a result, the switching strategy calibration needs to be revised.

The aim of the tuning of shift characteristics and accelerator pedal maps is to achieve a linearly increasing acceleration of the vehicle with increasing accelerator pedal position, as shown in the figure by the rising line 1. In the diagram, the vehicle longitudinal acceleration a is plotted over the accelerator pedal position x. The points 2 in the figure show the actual vehicle acceleration a at a certain accelerator pedal position x. In the figure it can be seen that the acceleration a from a defined speed in the current gear, when increasing the accelerator pedal position, the expectations can not meet initially, for example, there is too low engine torque request from the accelerator pedal map or too late downshift. With a further increase in the accelerator pedal position x, the vehicle longitudinal acceleration a does not correspond to the driver's expectations even after the first downshift 3 (at higher engine speed due to the downshift 3: still too low a torque request from the accelerator pedal map or too late downshift). This behavior makes the vehicle seem sluggish in the current gear and also after the first downshift 3. The second downshift 4 is triggered too early in relation to the pedal travel and greatly increases the tractive force, causing the acceleration a of the vehicle to skyrocket (due to the downshift and the requested engine torque changed due to the engine speed change, the tractive force increases abruptly). Especially after the sluggish behavior up to this point, the vehicle behaves unexpectedly after the second downshift 4 for the driver.

Achieving the ideal behavior requires a lot of effort from experienced calibrators.

The object of the invention is to avoid these disadvantages and to reduce the calibration effort for the gear selection.

According to the invention, we achieved this by: • the accelerator pedal position being evaluated on a single instance, preferably the engine control unit and the transmission control unit, the accelerator pedal position being interpreted as an acceleration request, that a necessary drive torque, preferably by a pilot control unit, and / or to fulfill the desired acceleration or an acceleration controller is determined, wherein the necessary drive torque is converted into a target engine torque of the engine for each gear, and that - based on the acceleration request - a consumption optimal and / or low-emission combination of engine torque and gear on the basis of at least one fuel stock characteristic map or pollutant map is selected.

The operating points of the internal combustion engine to fulfill the desired acceleration can be defined by the speed of the prime mover and the engine target torque in each gear.

The accelerator pedal position is only more easily evaluated by the parent of the engine and transmission control unit and assigned to a specific acceleration request. On the basis of this acceleration request, a necessary drive torque of the internal combustion engine is determined by a pilot control unit and / or an acceleration controller. The necessary drive torque is converted for each gear into a motor setpoint torque of the internal combustion engine. Then, using at least one fuel consumption characteristic map and / or at least one pollutant characteristic map of the internal combustion engine, a fuel consumption optimal and / or pollutant-optimal engine nominal torque is selected in the associated gear.

Due to the fact that the accelerator pedal prescribes an acceleration request and a controller regulates it, an ideal acceleration behavior can be implemented with very little effort. Same accelerator pedal positions means the same acceleration, regardless of whether the vehicle is on a horizontal, rising or falling track.

With an accelerator pedal position, which corresponds to the acceleration request 0 m / s2, the current speed can be maintained at a horizontal, ascending or descending route.

In order to keep the number of gear changes as small as possible, it is advantageous if a defined acceleration reserve is taken into account in the selection of the gear, wherein the gear is selected so that no gear change is required within the range of the acceleration reserve.

Different vehicle characteristics can be very easily made possible by different accelerator pedal acceleration maps and possibly by different acceleration reserves.

Compared to known switching strategies, much fewer calibration parameters are needed. The calibration effort is thus much lower.

In the figure, the vehicle longitudinal acceleration a is shown on the accelerator pedal position. The line 1 represents the ideal course of the vehicle longitudinal acceleration a as a function of the accelerator pedal position x. The points 2 correspond to the course when using switching strategies known from the prior art.

With the method according to the invention, a course of the vehicle longitudinal acceleration a corresponding to the line 1 or at least approaching strongly can be achieved. In this case, the accelerator pedal position x is interpreted by a single instance as an acceleration request and the corresponding drive torque of the drive wheels is determined. This instance can be formed, for example, by the transmission control unit or by a higher-level instance of both the engine control unit and the transmission control unit. For each available gear, the drive torque is converted into a corresponding engine nominal torque of the internal combustion engine and then carried out an optimization in terms of consumption and / or emissions. That gear, together with the associated engine target torque to fulfill the desired acceleration with minimum fuel consumption and / or minimum emissions, is finally selected and the shift is carried out.

In order to avoid frequent gear changes with little change in the position of the accelerator pedal, a defined acceleration reserve is taken into account when selecting the gear. This acceleration reserve - which may be positive both in the direction of increasing acceleration and negative, ie in the direction of falling acceleration - makes it possible to slightly raise or lower the desired acceleration, without having to reverse or raise the gear.

For additional reassurance, additional functions such as curve detection can prevent up and / or downshifts for a limited time.

An interface to lock certain aisles is also present, which makes it possible, for example, to prevent shifting into gears in which overheated or damaged switching elements would have to be used.

Claims (3)

A method for operating a motor vehicle having a transmission and an internal combustion engine as an engine, wherein the transmission with a transmission control unit and the prime mover is connected to an engine control unit, characterized in that • the accelerator pedal position (x) on a single - preferably the engine control unit and the transmission control unit superordinated -Instanz is evaluated, the accelerator pedal position is interpreted as an acceleration request, • that to fulfill the acceleration request a necessary drive torque, preferably by a pilot unit and / or an acceleration controller, is determined, the necessary drive torque in a target engine torque of the prime mover for each Gear is converted, and • that - based on the acceleration request - a consumption-optimal and / or low-pollution combination of engine torque and gear due to a Motorver Nutzkennfeldes or pollutant map is selected. 2. The method according to claim 1, characterized in that in the selection of the gear a defined acceleration reserve is taken into account, wherein preferably the gear is selected so that within the range of the acceleration reserve no gear change is required. 3. The method according to claim 1 or 2, characterized in that the operating points of the internal combustion engine to fulfill the desired acceleration by the rotational speed of the engine and the engine nominal torque are defined in each gear.