US-12617295-B2 - Drive control system for a motor vehicle operable by electric motor and having a gear selector

US12617295B2US 12617295 B2US12617295 B2US 12617295B2US-12617295-B2

Abstract

A drive control system for a motor vehicle able to be operated by an electric motor and having a drive stage selector, an electronic accelerator pedal, a brake pedal, and an electronic control unit that is configured such that a creep function is deactivated when a first alternative automatic drive stage is selected, and that a creep function is activated when a second alternative automatic drive stage is selected. The control unit furthermore contains an appropriately programmed function module by way of which, when the creep function is activated and based on creep pilot control, the creep moment predefined thereby, in the form of a drive moment, is reduced based on a braking request from the driver, wherein a frictional braking moment is activated by the conventional wheel brake system only when the minimum possible creep moment is reached.

Inventors

Florian Schnappauf

Assignees

BAYERISCHE MOTOREN WERKE AKTIENGESELLSCHAFT

Dates

Publication Date: 20260505
Application Date: 20220210
Priority Date: 20210305

Claims (11)

1 . A drive control system for a motor vehicle operable by electric motor comprising: a gear selector; an electronic accelerator pedal; a brake pedal; and an electronic control unit, which is connected to the gear selector, the accelerator pedal, and the brake pedal, wherein the electronic control unit is configured to: deactivate a creep function in response to a first alternative automatic gear being selected; and activate a creep function in response to a second alternative automatic gear being selected, wherein a creep torque predefined by a creep pilot control and in the form of a drive torque is reducible depending on a braking intent of the driver starting from the creep pilot control, and wherein a frictional braking torque is applied only when a minimum possible creep torque applied by the electric motor has been reached, and wherein the minimum possible creep torque is the current maximum possible recuperation torque by the electric motor.
2 . The drive control system according to claim 1 , wherein when the creep function is activated, the creep torque predefined by a creep precontrol is reduced depending on the braking intent of the driver starting from the creep precontrol and only within a defined lower velocity-frictional braking torque range.
3 . The drive control system according to claim 1 , wherein the creep torque is reduced in proportion to the braking intent of the driver.
4 . The drive control system according to claim 1 , wherein the minimum possible creep torque is zero.
5 . The drive control system according to claim 1 , wherein the creep torque predefined by the creep pilot control is determined depending on a vehicle velocity.
6 . The drive control system according to claim 1 , wherein the gear selector has an automatically restoring toggle switch for selecting the first alternative automatic gear or the second alternative automatic gear, and wherein every time the toggle switch is actuated counter to the direction of travel starting from one of the two alternative automatic gears, the particular other alternative automotive gear is selectable.
7 . An electronic control unit for a drive control system of a motor vehicle operable by electric motor, wherein the electronic control unit is configured to: deactivate a creep function of the motor vehicle in response to a first alternative automatic gear being selected; and activate a creep function in response to a second alternative automatic gear being selected, wherein a creep torque predefined by a creep pilot control and in the form of a drive torque is reducible depending on a braking intent of a driver starting from the creep pilot control, and wherein a frictional braking torque is applied only when a minimum possible creep torque applied by the electric motor has been reached, and wherein the minimum possible creep torque is the current maximum possible recuperation torque by the electric motor.
8 . The electronic control unit according to claim 7 , wherein when the creep function is activated, the creep torque predefined by a creep precontrol is reduced depending on the braking intent of the driver starting from the creep precontrol and only within a defined lower velocity-frictional braking torque range.
9 . The electronic control unit according to claim 7 , wherein the creep torque is reduced in proportion to the braking intent of the driver.
10 . The electronic control unit according to claim 7 , wherein the minimum possible creep torque is zero.
11 . The electronic control unit according to claim 7 , wherein the creep torque predefined by the creep pilot control is determined depending on a vehicle velocity.

Description

FIELD The invention relates to a drive control system for a motor vehicle operable by electric motor and having a gear selector, having an electronic accelerator pedal, having a brake pedal and having an electronic control unit, which is connected to the gear selector, the accelerator pedal and the brake pedal. BACKGROUND AND SUMMARY The so-called “one-pedal feeling” with an electronic accelerator pedal in electric vehicles, which, more particularly, is a characteristic of the BMW i3, ensures that, once the accelerator pedal has been released, there is a strong, spontaneously controllable deceleration nearly to a standstill with high recuperation. Moreover, many different recuperation methods are already known for decelerating electrified motor vehicles (hybrid vehicles or purely electric vehicles). DE 10 2017222819 A1 deals with a solution to the problem that the so-called “one-pedal feeling” is not perceived to be advantageous in all situations. Moreover, the problem of brakes squeaking during creep is dealt with, for example, in EP 0 822 128 B1. The problem addressed by the invention is that of further improving the comfort in electrified motor vehicles, more particularly, having a purely electric drive. According to the invention, this problem is solved by the features as disclosed herein. Preferred enhanced embodiments of the invention are also described herein. The invention relates to a drive control system for a motor vehicle operable by electric motor and having a gear selector, having an electronic accelerator pedal, having a brake pedal and having an electronic control unit, which is connected, more particularly electrically, to the gear selector, the accelerator pedal and the brake pedal in order to detect the actuation thereof and/or the actual position thereof in the conventional way via appropriate sensors. The control unit is designed, for example, by means of an appropriately programmed software module, such that a creep function is deactivated when a first alternative automatic gear (more particularly an automatic gear “B” or “i” or “e”, which has a driving behavior that is characteristic for purely electric vehicles (“BEV”)) is selected, and that a creep function is activated when a second alternative automatic gear (more particularly a typical drive automatic gear labeled “D” in the case of automatic transmissions) is selected. In principle, creep is activated in gear “D.” In the related art, however, creep has previously been carried out regardless of the braking intent of the driver. According to the invention, the control unit therefore also includes an appropriately programmed function module, by means of which, when the creep function is activated, the creep torque predefined by a creep pilot control and in the form of a drive torque is reduced depending on a braking intent of the driver starting from the creep pilot control, wherein a frictional braking torque is applied by the conventional wheel brake system only when the minimum possible creep torque (for example, zero or the maximum possible recuperation torque) has been reached. The braking intent of the driver is detected, for example, in the usual way via the detected brake pressure at the brake pedal. Preferably, the predefined creep torque is reduced depending on the braking intent of the driver and only within a defined lower velocity-frictional braking torque range. This velocity-frictional braking torque range is defined, more particularly, by empirically ascertaining that wheel-brake squeaking has arisen. Preferably, the creep torque is reduced in proportion to the braking intent of the driver. The creep torque predefined within the scope of the creep pilot control is preferably determined at least also depending on the vehicle velocity. This is the case because squeaking arises primarily at comparatively low vehicle velocities with low negative acceleration. In one advantageous enhanced embodiment of the invention or also as an independent concept addressed by the invention, the gear selector has an automatically restoring toggle switch for selecting the first alternative automatic gear or the second alternative automatic gear, wherein every time the toggle switch is actuated counter to the direction of travel starting from one of the two alternative automatic gears, the other alternative automotive gear is selectable. The invention also relates to an electronic control unit and at least one software function module for the electronic control unit of the drive control system according to the invention. The invention is based on the following considerations: In principle, acoustic problems also arise during creep with electrified motor vehicles having electric machine drive technologies due to brake squeaking during the application of the drive torque against the friction brake of the motor vehicle service brake. In electrified drive concepts in which the internal combustion engine can be decoupled via clutches or which