Drive Control System For A Motor Vehicle Operable By Electric Motor And Having A Gear Selector

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.

Claims

1-9. (canceled)

10. 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 has been reached.

11. The drive control system according to claim 10, 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.

12. The drive control system according to claim 10, wherein the creep torque is reduced in proportion to the braking intent of the driver.

13. The drive control system according to claim 10, wherein the minimum possible creep torque is zero.

14. The drive control system according to claim 10, wherein the minimum possible creep torque is the current maximum possible recuperation torque.

15. The drive control system according to claim 10, wherein the creep torque predefined by the creep pilot control is determined depending on a vehicle velocity.

16. The drive control system according to claim 10, 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.

17. 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 has been reached.

18. The electronic control unit according to claim 17, 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.

19. The electronic control unit according to claim 17, wherein the creep torque is reduced in proportion to the braking intent of the driver.

20. The electronic control unit according to claim 17, wherein the minimum possible creep torque is zero.

21. The electronic control unit according to claim 17, wherein the minimum possible creep torque is the current maximum possible recuperation torque.

22. The electronic control unit according to claim 17, wherein the creep torque predefined by the creep pilot control is determined depending on a vehicle velocity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows an overview, in a schematic representation, of the essential components of the drive system according to the invention including selection of the two alternative automatic gears,

[0024] FIG. 2 shows an overview, in a schematic representation, of creep pilot control for the creep function according to the invention,

[0025] FIG. 3 shows a diagram-type explanation of a creep function according to the related art, and

[0026] FIG. 4 shows a diagram-type explanation of a creep function according to the invention.

DETAILED DESCRIPTION

[0027] FIG. 1 shows a drive control system for a motor vehicle operable by electric motor, that includes an electronic control unit 2, which is electrically connected to a gear selector 1, to a display operating unit 3, to an accelerator pedal 5, and to a brake pedal 6. The gear selector 1 can include an actuating element 7 in the form of an automatically restoring toggle switch for selecting various gears R, N, D or B, wherein every time the toggle switch is actuated counter to the direction of travel starting from one of the two alternative automatic gears D and B, the particular other alternative automotive gear is selectable.

[0028] The electronic control unit 2 is designed, more particularly due to an appropriately programmed software module 4, such that, in principle, a comparatively high (preferably maximum) recuperation level is set and creep is deactivated when a first alternative automatic gear (B) is selected and the accelerator pedal is released, and that at least one selectable fixed recuperation level or a (more particularly auto-adaptive) sailing operation is predefinable and creep is activated when a second alternative automatic gear (D) is selected and the accelerator pedal is released.

[0029] For implementing recuperation in the gear D, the recuperation level can preferably be configured by the driver, for example, via a display operating unit 3. The driver can choose, for example, between an adaptive recuperation or a preferred, fixedly settable recuperation level (in this case, for example, high/medium/low). With adaptive recuperation (via camera, radar, and navigation data), the vehicle automatically selects the correct recuperation as a function of the traffic situation.

[0030] The control unit 2 including the software module 4 is also designed according to the invention such that a creep function is activated when the second alternative automatic gear D is selected, in which the creep torque M_KR predefined by a creep pilot control M_KR_vor and in the form of a drive torque is reduced depending on a braking intent M_FW of the driver starting from the creep pilot control M_KR_vor, wherein a frictional braking torque M_RB is applied only when the minimum possible creep torque has been reached.

[0031] One possible method for determining the creep pilot control M_KR_vor is represented in FIG. 2. The creep torque M_KR predefined by the creep pilot control M_KR_vor is preferably determined depending on the vehicle velocity v. For this purpose, a raw creep torque M_KR depending on the vehicle velocity v is multiplied by a factor F between 0 and 1. The factor F is read out from a characteristic map, which specifies a value between 0 and 1 depending on the vehicle velocity v and the frictional brake torque M_RB.

[0032] FIG. 3 shows the effect of a creep function according to the related art. In principle, creep is activated in gear D. In the related art, however, the creep torque M_KR is implemented regardless of the braking intent M_FW of the driver. The braking intent M_FW is attended to solely by means of the frictional braking torque M_RB of the service brake. This results in an unsteady deceleration curve of the vehicle velocity v and, as a result, in brake squeaking for particularly low values of the vehicle velocity or deceleration. According to the invention, the friction brake is therefore intended to be used as little as possible.

[0033] FIG. 4 shows the creep function according to the invention in greater detail with reference to an exemplary embodiment:

[0034] When the creep function is activated, the creep torque M_KR predefined by the creep precontrol M_KR_vor is reduced depending on the braking intent M_FW of the driver starting from the creep precontrol M_KR_vor and preferably only within a defined lower velocity-frictional braking torque range KF. This lower velocity-frictional braking torque range KF is schematically plotted in FIG. 2 as a range KF, which is particularly relevant for the squeaking problem. The range KF defines that the vehicle velocity v is to be lower than a first threshold value S1 and the frictional braking torque M_RB is to be lower than a second threshold value S2.

[0035] FIG. 4 also shows that the creep torque M_KR is reduced in proportion to the braking intent M_FW of the driver until, preferably, the minimum possible creep torque has been reached, which is the currently maximum possible recuperation torque M_max_Reku in this case.