DE102009037182A1 - Method for controlling or regulating crawling moment of vehicle with electric drive, particularly hybrid- or electric vehicle, involves generating crawling moment from braking intensity by electric drive, with which vehicle is limited - Google Patents

Abstract

The method involves generating a crawling moment from the braking intensity by an electric drive, with which the vehicle is limited. The crawling moment is controlled or regulated according to the overall braking intensity that is applied from vehicle systems.

Description

The The present invention relates to a method of controlling the creep torque of a vehicle with electric drive according to the preamble of claim 1.

vehicles with automatic transmission are known to be between the engine and the automatic transmission input to a converter. When the gearbox in drive state and the vehicle by means of the service brake or the parking brake is braked so that it stands still, occurs in the converter slip which leads to a creeping moment and corresponding energy consumption leads. Becomes the brake released, so the vehicle rolls on until at a speed of about 5 km / h sets a torque equilibrium (maximum creep speed).

hybrid vehicles and electric vehicles with automatic transmission can be basically very similar to Drive vehicles with automatic transmission. Because with these vehicles Due to the concept, however, no converter is needed and therefore also is not provided, missing the maneuvering of conventional Vehicles with automatic transmission known creep torque. Without creeping moment is the maneuvering of hybrid or electric vehicles but relatively uncomfortable, since the driver in a short time often between the driving and Brake pedal must change. To simplify maneuvering, there are already different concepts to those of conventional automatic vehicles imitate known creep by means of the electric drive. Becomes A creeping torque generated even when the vehicle is stationary, so affects this unfavorable on the total consumption. Furthermore is a creeping moment when the vehicle is stationary with an additional, especially thermal stress on the affected components, in particular the electric motor and the power electronics connected.

task The invention is a method for controlling the Specify creep torque of a vehicle with electric drive at the creep torque is energetically sensible controlled or regulated becomes.

These The object is solved by the features of claim 1. advantageous Refinements and developments of the invention are the dependent claims remove.

The Basic principle of the invention is that by means of the electron drive of a hybrid or electric vehicle one of the "braking power" with which braked the vehicle becomes, dependent creeping moment is produced. The invention is thus based on the idea of a Creep as possible only to generate, when needed, unnecessary energy losses to avoid. Similar to at conventional Vehicles with automatic transmission and converter is thus in the operating state "driving" in shunting generates a creeping moment, so that the vehicle alone over the Brake pedal and the steering wheel can be controlled.

Of the Term "brake strength" can z. B. be interpreted as total braking pressure or total braking torque, which is generated by the brake system of the vehicle. The creeping moment So not necessarily dependent from the driver over the brake pedal controlled or regulated predetermined braking request, but generally in dependence the total wheel brake strength (Total brake pressure, total braking torque, o. Ä.), The z. As well as electronic systems such as B. of an electrically controlled parking brake system, a Start-up assistants, an "automatic hold assistance system "or the z. B. BMW vehicles known "ACC Stop and Go System" controlled can be.

According to the invention is provided that the creep torque is reduced when the vehicle stands and a "high" braking torque is available. Above a given "braking force", the creeping torque can a predetermined minimum value can be reduced. The minimum value can also be zero, d. H. the generation of a creep torque can when the vehicle is stationary and above a given braking intensity completely be disabled.

Further can be provided that the creep depending on generated by the speed of the vehicle. Basically, can be provided be that the creep torque is lower, the larger the creep Speed of the vehicle is. In standing or almost stationary Vehicle is the creep torque accordingly maximum, whereas it decreases with increasing speed as the vehicle rolls becomes.

Further can be provided that the creeping torque with decreasing braking force rises to a maximum value, wherein it may be provided that the Maximum value of the creeping torque already reached at a braking force that's bigger than Is zero. With unrestrained rolling or only slightly braked vehicle So the maximum creep torque is controlled.

Becomes the vehicle is braked while rolling, then the creep torque with increasing braking power or increasing braking torque according to a prescribed control strategy to values that are less than the maximum creep torque are.

It can be provided that with decreasing braking torque, the increase The creep torque from the minimum value to the maximum value is the steeper or the maximum value is greater, the smaller the speed. Conversely, it can be provided that with decreasing braking torque the increase of the creep torque of Minimum value to the maximum value the flatter or the maximum value all the more smaller, the bigger the Speed of the vehicle is.

If the vehicle is at a standstill and a high braking torque is applied, then the creep torque is reduced. With decreasing Braking torque, the creep torque is rebuilt. The driver can thus over the brake pedal "modulate" the crawl speed. An unnecessary creeping moment with corresponding energy consumption is thus avoided.

at the interpretation of dependence between the creep torque and the braking torque is to be noted that at very small braking torques the creep torque is not yet is hardly reduced, since in this braking torque range the actual Creep takes place, the z. B. when maneuvering the vehicle Advantage is.

Furthermore It is important that the drive torque does not decrease faster afterwards as the braking torque increases, otherwise the vehicle when starting on a slope after loosening the brake first roll back would, before it starts to crawl. The with decreasing brake strength Incremented increase of the Kreichmoments should so in amount be at least as big like the decrease in braking power, so that when starting on a slope a backward rolling of the vehicle Solve the Brake is prevented. Preferably, with decreasing braking torque the increase in the creep torque in terms of amount greater than the decrease in the braking torque.

To a development of the invention is provided that the Kriechmomentenverlauf time is filtered to jump, d. H. noticeable changes for the driver to avoid the creeping torque. The filtering must be fast be enough to solve quickly the brake on a slope to prevent the vehicle from rolling backwards. at A too slow filtering would risk the braking torque already degraded relatively far before a correspondingly large drive torque is applied. The temporal filter characteristic of the Kriechmomentenverlaufs as the creep torque increases, the temporal filter characteristic may change the Kriechmomentenverlaufs with decreasing creep torque differ.

The dependence the creep torque of the vehicle speed forms on the one hand those of conventional Automatic vehicles known dependence the creep torque from the vehicle speed and provides on the other hand, sure that when driving an inappropriate driving torque reduction is avoided.

To a development of the invention is the drive torque reduction withdrawn as soon as possible the accelerator pedal is pressed becomes. Thus, the driver always has the opportunity, the full creep or a higher one Retrieve drive torque. Also conceivable is a flexible adaptation the accelerator pedal characteristic, the "zero%" position of the accelerator pedal, d. H. if the accelerator pedal is inactive is, mathematically always on the current reduced creep is placed.

To a development of the invention is for the control or regulation the creep torque used "brake force", either measured and / or calculated, a plausibility check subjected. If the "input signals" for the creep torque reduction, especially the braking torque, due to a system failure not to disposal can be provided or that are implausible, it can be provided that the Kriechmomentreduzierung is deactivated. The vehicle then always crawls with the maximum Creep. Alternatively, it may be provided that in the case of a fault or no apparent creep torque is activated in the event of a brake force that does not appear plausible is adjusted to an unnecessary Component load as well as unnecessary To avoid energy consumption. Only with an actuation of the Accelerators is then available again drive torque.

Claims (16)

Method for controlling or regulating the creep torque of a vehicle with electric drive, in particular a hybrid or electric vehicle, characterized in that by means of the electric drive, a creep torque dependent on the braking force with which the vehicle is braked is generated. Method according to claim 1, characterized in that that the creep depending on the Controlled by vehicle systems applied total braking power becomes. Method according to claim 1 or 2, characterized that the creep depending on generated by the speed of the vehicle. Method according to one of claims 1 to 3, characterized in that the creep torque above a predetermined braking force on a predetermined minimum value, in particular to zero, is reduced. Method according to one of claims 1 to 4, characterized the creep torque increases to a maximum value as the braking power decreases. Method according to one of claims 1 to 5, characterized that the maximum value of the creeping torque already reached at a braking force that's bigger than Is zero. Method according to one of the preceding claims, characterized characterized in that with decreasing braking torque, the increase of Creep torque from the minimum value to the maximum value is the steeper or the maximum value is greater, the smaller the speed of the vehicle is. Method according to one of the preceding claims, characterized characterized in that with decreasing braking torque, the increase of Creep torque in terms of amount always at least as big as that Decrease in braking torque is such that when starting on a slope a backward roll of the vehicle when releasing the brake is prevented. Method according to claim 8, characterized in that that with increasing braking torque, the increase in the creeping torque always greater than the decrease of the braking torque is. Method according to one of claims 1 to 9, characterized that for used the control or regulation of the braking torque as an input variable braking strength a plausibility check is subjected. Method according to claim 10, characterized in that that the reduction of the creep torque deactivated with increasing braking force will or that at all no creep torque is generated when the as input to the controller or Regulation of the creep torque used brake force seems implausible. Method according to one of claims 1 to 3, characterized that reduces the creeping torque with increasing braking power, in particular to zero, is reduced. Method according to one of the preceding claims, characterized characterized in that the creep torque increase and decrease time is filtered to noticeable erratic drive torque changes to avoid. Method according to claim 13, characterized in that that the temporal filtering for the increase and decrease of the creeping torque designed differently becomes. Method according to one of the preceding claims, characterized characterized in that the drive torque reduction is withdrawn is when the accelerator pedal is pressed becomes. Method according to one of the preceding claims, characterized characterized in that the drive torque reduction takes into account in the accelerator pedal characteristic becomes.