DE102023100402A1 - Method for providing torque in a power-limited system - Google Patents

Abstract

A method is provided for providing torques in power-limited systems, wherein in the case of a gear change in which the system is transferred from one operating state to a second operating state, in a first step the wheel torque applied during the gear change is calculated on a speed-based basis according to the formula (1) R_d = K_d * i_d, where i_d is the speed-based gear ratio and K_d is the torque curve along a power hyperbola during the speed transfer.

Description

The invention relates to a method for providing torques in a power-limited system, such as in an at least partially electrically powered vehicle, wherein negative drive potentials are optimized during a gear change in interaction with the brake.

For example, in hybrid vehicles with an electric motor in the drive before the transmission, the electric motor is used to decelerate (brake) the vehicle, which is known as drag recuperation and brake recuperation. If their performance is no longer sufficient, friction brakes are also used. It can happen that the braking system has to switch between the friction brake and brake recuperation (drive) in order to continue to meet the driver's braking request when the vehicle is braked. This happens, for example, when changing gears, since the wheel torque is the result of multiplying the potential before the transmission by the changing gear ratio. When changing gears, the torque transmission (transmission) and speed transmission (transfer) through the transmission take place at different times.

This systematically leads to a change in torque during speed adjustment, which is the most sensitive part of a gearshift and can therefore lead to jerking, releasing or deceleration during the gearshift process. The interaction between the drive and the braking system can also take place via several control units and buses and can therefore be associated with signal run times, which can lead to inaccuracies in the overall behavior. Furthermore, depending on the brake condition, the use of the brakes can have the following disadvantages, which can be particularly noticeable when the torque changes: less accurate positioning of the brake compared to the drive, scraping, squeaking.

In order to improve the disadvantages mentioned, it is an object of this invention to provide a corresponding method which solves these problems. This object is solved according to the invention by the features of the independent patent claims. Advantageous embodiments are the subject of the dependent claims.

A method is proposed for providing torques in power-limited systems, wherein in the case of a gear change in which the system is transferred from one operating state to a second operating state, in a first step the wheel torque applied during the gear change is calculated on a speed-based basis according to the formula (1) R_d = K_d * i_d, where i_d is the speed-based gear ratio and K_d is the torque curve along a power hyperbola during the speed transfer.

Furthermore, it is provided that in a second step a new torque of the transmission input during the gear change is calculated based on the wheel torque calculated in the first step according to the formula (2): K_m = R_d / i_m, where i_m is the torque-based ratio.

Furthermore, it is intended that the gear change is a braked downshift. Furthermore, it is intended that the gear change is a braked upshift. Furthermore, it is intended that the gear change is a shift in which the drag recuperation has already reached the performance limit of the system.

Furthermore, a computer program product with program code for carrying out the method is proposed when it is executed on at least one control unit of the vehicle.

Furthermore, a control device or devices is proposed in which the method is implemented as a computer program.

Furthermore, a power-limited system is proposed which has at least one control unit, wherein the power-limited system is an electric machine or a motor or a pump which is controlled by the control unit.

Furthermore, a vehicle is proposed comprising the power-limited system.

Further features and advantages of the invention emerge from the following description of embodiments of the invention, based on the figures of the drawing, which show details according to the invention, and from the claims. The individual features can be implemented individually or in groups in any combination in a variant of the invention.

• 1 zeigt eine schematische Darstellung des Zusammenhangs der Signalverläufe bei einem Gangwechsel, mit Überblendung zur Bremse gemäß dem Stand der Technik und einer Ausführung der vorliegenden Erfindung.
• 2 zeigt eine schematische Darstellung des Zusammenhangs zwischen Moment und Drehzahl bei einem leistungsbegrenzten System.
• 3 zeigt eine schematische Darstellung wichtiger Komponenten zur Durchführung des Verfahrens gemäß einer Ausführung der vorliegenden Erfindung.

Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings.

• 1 shows a schematic representation of the relationship between the signal curves during a gear change, with cross-fading to the brake according to the prior art and an embodiment of the present invention.
• 2 shows a schematic representation of the relationship between torque and speed in a power-limited system.
• 3 shows a schematic representation of important components for carrying out the method according to an embodiment of the present invention.

In the following figure descriptions, identical elements or functions are provided with identical reference symbols.

The basic concept of the invention is to optimize drive potentials during a gear change for a power-limited system 102 (which can be any type of motor or pump) that moves along a power hyperbola (negative torque M and speed curve N over speed n). A power-limited system 102 is understood to mean drive components that are located in front of the transmission input.

In particular, the invention is directed to a power-limited system 102 that is used in the vehicle to optimize drive potentials in interaction with the brake, as described below. During a gear change G, the system is switched from an operating state (C in 1 ) if necessary via further states D, A into a second operating state (B in 1 ) was transferred.

In principle, positive and negative potentials can be used, whereby the invention has advantages for both the transmission and the brake. For example, gear shifting (shifting quality, jerking) is improved by shifting the torque change outside the speed transfer. In addition, the coordination between drive and brake can be calmed independently of this by preventing the short-term torque change during a shift. Thus, the invention is an advantage for gear shifting even in a system in which the brake does not balance.

The invention is described below using an embodiment and 1 to 3 described, which shows a gear change with cross-fading to the brake in a vehicle. Cross-fading means the transfer of torque from the drive to the friction brake or vice versa, so that the total at the wheels is maintained. This process is also known as balancing.

Whether the system is torque-based or power-based limited can be determined by a defined corner speed E, as in 2 shown, limited or taken into account online via an interface, e.g. to the E-system. The operating point A, B is above the base speed E, as in 2 shown, and is thus power-limited. If the operating point is below the base speed E, the system is torque-limited. The invention relates to a power-limited system 102. A power-limited system 102 is to be understood as meaning that the deceleration power (eg generator power in an electric machine) is limited. In addition, an ascertainable influence can also act, which can thus be calculated out if the accuracy requires it.

In a power-limited system 102, the torque at the transmission input K changes with the speed (speed curve N) along the power hyperbola ( 2 from A to B with direction *). P=M _A × n _A = M _B × n _B (power P = torque M x speed n). In the short period of time during which a gear change takes place, the power is almost constant and is therefore assumed to be constant as a good approximation. The power does not change as a result of a gear change, so P=M _A × n _A = M _B × n _B still applies.

The drive potential (e.g. torque of the transmission input K), which includes, for example, an electric motor of a hybrid drive, is multiplied by the transmission ratio (e.g. i_m) to form a wheel potential as a torque (wheel torque R): K x i_m = R. The braking function can control brake recuperation up to the wheel torque R and will also use the friction brake to fulfill the driver's braking request. The braking function is implemented as software and can be located on any control unit.

The minimum (negative) drive potential arises from the transmission input torque K_d, which has a simplified constant torque up to the speed transfer A and follows the power hyperbola up to B ( 1 and 2 ). Normally, the wheel torque potential R_m is formed based on the torque by multiplying it by the torque ratio (R_m = K_d x i_m), whereby during the short time of the gear shift (usually less than 1s) a smaller negative potential (when shifting down or larger when shifting up) would be calculated and thus the braking function must balance in and out over this period, with the disadvantages mentioned above, since the minimum drive potential should be used for efficiency reasons. If the speed ratio i_d is used instead, a wheel torque R_d (wheel torque potential) results without the local increase (R_d = K_d x i_d) (first step), whereby the braking function can maintain the division between drive and friction brake during the gear shift, so no balancing is required. The friction brake component ΔBr no longer has to be reduced to ΔBr' in order to subsequently fade back to ΔBr. Instead The friction brake component ΔBr can be maintained, meaning that the above-mentioned disadvantages no longer occur systematically with each gear change. By preventing the short-term torque change during a gear change, the coordination between drive and brake is calmed down, regardless of the gear change quality. The energy that is not absorbed during the gear change (difference between R_d and R_m) can (if necessary) be used further by the transmission control to provide a homogeneous acceleration behavior across the gear change.

Independent of the braking system and the presence of a balancing braking function, starting from the wheel torque R_d, an advantage for the gear shift quality (e.g. jerking, releasing or deceleration) can be achieved by shifting the torque change outside the speed transfer. Using the torque ratio i_m, the new torque of the transmission input (transmission input torque) K_m is calculated (K_m = R_d / i_m) and used, whereby the torque change no longer occurs during speed transfer ( 1 and 2 A , B and *) as the most sensitive part of the circuit, but during the momentary crossfade ( 1 and 2C , D), which is significantly more resilient in terms of shifting quality. This reduces or even eliminates jerking, releasing or delaying of the shifting.

This procedure can also be used for towing recuperation, i.e. in the case where towing recuperation has already reached the performance limit of the system and thus braking recuperation is no longer possible.

The proposed method is based on 1 described, which shows a brake downshift, i.e. a gear change to a lower gear during a braking process.

Curves K and R represent negative torques. Curve R (wheel torque) represents the drive deceleration potential (e.g. an electric motor used in a hybrid vehicle is operated as a generator). This is the potential that is used by brake recuperation and is balanced with the brake to represent a driver braking or deceleration request. Curve Br represents the braking or deceleration request. To simplify the representation of the inventive concept, the braking request Br is chosen to be constant in this example. In addition, the difference ΔBr between the braking request Br and the drive wheel torque potential R is shown, with the dashed line representing the state of the art (R_m) and the solid line the result of the proposed method (R_d). It can be seen that the friction braking torque of the brake can be kept constant according to the proposed method (all ΔBr are the same). According to the previous approach (state of the art), the friction brake torque would have to be briefly reduced during a gear change due to the change in the wheel torque R_m by using the torque ratio i_m (ΔBr' is smaller than ΔBr) in order to comply with the driver's braking or deceleration request via the brake balancing.

The three curves above represent the speed curve N, the speed ratio i_d and the torque ratio i_m.

All curves have the same time course t. In the case of a brake downshift, there is a change in the torque ratio i_m to the target gear ( 1C , D) before the speed transfer / ratio i_d ( 1 A , B, *), which describes the change from operating point A to operating point B ( 1 and 2 A , B, *).

The smallest possible drive wheel torque potential that can be controlled by drag and/or brake recuperation through a braking function is currently defined by K_d (dashed line in 1 and 2 ), by means of torque ratio i_m, to the wheel torque R_m (dashed line in 1 ). The controlled torque of the transmission input K is also calculated back from the wheel torque R_m as K_d using the torque ratio i_m, whereby K_d is still the smallest possible (negative) drive torque and, due to the power limitation, its amount is distributed over the speed n along the power hyperbola ( 2 A , B,*) changes.

Previously, the torque change at the transmission input during the speed transfer (A, B) was K_d. According to the invention, the torque change at the transmission input during the torque blending (C, D) is K_m (solid line in 1 and 2 ). Since the speed transfer is the most sensitive point of the gearshift, the invention avoids the transfer of the torque of the gearshift input K in this area. This reduces or even prevents jerking, releasing or deceleration caused by the gearshift.

In a power-limited system 102 (i.e. at operating points above the base speed E at the power limit of the system), the wheel torque R during the gear change G is calculated according to the invention using the speed ratio i_d (first step) - instead of with the torque ratio i_m as before.

wobei
i_d die drehzahlbasierte Übersetzung ist, und
K_d der Momentenverlauf entlang der Leistungshyperbel (2 A, B).The wheel torque R_d is calculated according to the formula (1): $\text{R\_d}=\text{K\_d}\times \text{i\_d},$

where
i_d is the speed-based ratio, and
K_d is the torque curve along the power hyperbola ( 2 A , B).

This eliminates the change in the wheel torque potential (decrease of the curve R_m in 1 ) during the gear change G (gear shift) and the wheel torque R_d remains unchanged (solid line in 1 ), so that the brake can be controlled harmoniously without the above-mentioned disadvantages such as inaccuracy of the overall behavior due to signal propagation times, and/or perceptibility of the brake positioning accuracy depending on the brake state during cross-fading.

In addition (second step), the torque of the transmission input K_m via the gear change G ( 1C , D, A, B) according to the formula (2): K_m = R_d / i_m, where i_m is the torque-based ratio.

This calculation shows that the torque of the transmission input K is already at the beginning of the gear change G at C ( 1 ) is changed to the value of the torque of the transmission input K_B required for the new gear (ramp CD from K_m 1 ), as in 1 shown by the solid line K_m, and not - as before - only in the speed transfer, i.e. after the speed ratio i_d from A to B, as in 1 shown with the dashed line K_d. For illustration, the transition from operating point A (current operating point) to operating point B (operating point after gear change) is shown in 1 and 2 also marked with an (*).

The proposed method, which uses the limited power of the system to change the calculation from the conventional torque ratio i_m to the speed ratio i_d during brake downshifts, achieves better functionality between the vehicle's control units that control the following functions: gear changes, drive torques, brake recuperation, braking. This improves driving behavior in a targeted manner.

Even if the invention has been described based on the preferred embodiment of the brake downshift, it can also be applied analogously for brake upshifts (braked shifting to a higher gear), as well as for shifts (with or without braking) in which the drag recuperation has already reached the performance limit of the system and thus brake recuperation is no longer possible.

The method is preferably implemented as software or computer program on one or more corresponding control units 101 in a vehicle 100 with hybrid drive, which is in signal and active connection with the required components to be controlled, such as drive before transmission input (power-limited system 102), e.g. electric motor, and drive component(s) after transmission output or brake 103, as in 3 indicated schematically.

List of reference symbols

in the

Moment translation

i_d

Speed ratio

M

Torque

N

Speed curve

n

number of revolutions

P

Performance

E

Corner speed

K

Gearbox input torque

K_B

Torque of the transmission input after gear change at operating point B

K_d

Torque curve along power hyperbola (StdT)

K_m

Torque curve based on torque ratio

R

Wheel torque, drive wheel torque potential

R_d

Torque curve along power hyperbola calculated with speed ratio

R_m

Torque curve along power hyperbola calculated with torque ratio (StdT)

Br

Brake request

ΔBr

Difference between braking demand and drive wheel torque potential R_d

ΔBr'

Difference between braking requirement and drive wheel torque potential R_m

G

Gear change

AWAY

Operating points speed transfer to power hyperbola

C, D

Operating points start and end torque ratio

E

Corner speed

100

vehicle

101

Control unit

102

power-limited system before transmission input

103

Brake or drive component after transmission output

Claims (9)

Method for providing torques in power-limited systems (102), wherein in the case of a gear change (G) in which the system is transferred from one operating state (C) to a second operating state (B), - in a first step, the wheel torque (R_d) present during the gear change (G; C-D-A-B) is calculated based on the speed according to the formula (1): R_d = K_d * i_d, where i_d is the speed-based gear ratio, and K_d is the torque curve along a power hyperbola during the speed transfer (i_d; A, B). Procedure according to Claim 1 , wherein - in a second step, a new torque of the transmission input (K_m) during the gear change (G; C, D) is calculated based on the wheel torque (R_d) calculated in the first step according to the formula (2): K_m = R_d / i_m, where i_m is the torque-based gear ratio. Procedure according to Claim 1 or 2 , where the gear change (G) is a braked downshift. Procedure according to Claim 1 or 2 , where the gear change (G) is a braked upshift. Procedure according to Claim 1 or 2 , whereby the gear change (G) is a shift in which the drag recuperation has already reached the performance limit of the system. Computer program product with program code for carrying out the method according to one of the preceding claims when it is executed on at least one control unit (101) of the vehicle (100). Control device (101) or control devices (101) in which the method according to one of the Claims 1 until 5 implemented as a computer program. Power-limited system (102) comprising at least one control device (101) according to Claim 7 wherein the power-limited system (102) is an electric machine or a motor or a pump which is controlled by the control unit (101). Vehicle (100) comprising the power-limited system (102) according to Claim 8 .

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