Method for controlling a brake system for adjusting a total brake torque distribution between a first and a second axle of a motor vehicle and a brake system to carry out the procedure

1. A method for controlling a braking system for setting a total braking torque distribution between a first axle and a second axle of a motor vehicle, wherein the braking system comprises a friction braking device and a recuperative braking device, wherein the braking system further comprises a total braking torque that is composed of a friction braking torque portion of the friction braking device and a recuperative braking torque portion of the recuperative braking device, and wherein when a braking request is distributed according to a preset braking torque ratio W1/W2 to the respective first and second axles, the friction braking torque portion is distributed according to a preset friction braking torque ratio B1/B2 to the respective first and second axles, wherein B1 is a percentage of the friction braking torque portion associated with the first axle, B2 is a percentage of the friction braking torque portion associated with the second axle, W1 is a percentage of the total braking torque associated with the first axle, and W2 is a percentage of the total braking torque associated with the second axle, the method comprising:

determining a minimal recuperation torque for one of the first or second axles in response to B1 not being equal to W1; and

setting the minimal recuperation torque on the one of the first or second axles, wherein the minimal recuperation torque remains on the one of the first or second axles for all driving situations as the recuperative braking torque portion, and wherein the setting the minimal recuperation torque on the one of the first or second axles comprises:

in response to W1<B1, setting the minimal recuperation torque on the second axle, wherein the minimal recuperation torque is:

M

B

,

Rek

,

Min

,

=

M

B

,

Ges

*

(

1

-

W

⁢

⁢

1

B

⁢

⁢

1

)

,

wherein M B,Ges is the total braking torque,

wherein a remaining residual friction torque is calculated as:

M

B

,

Reib

,

rest

=

M

B

,

Ges

*

W

⁢

⁢

1

B

⁢

⁢

1

,

wherein a residual friction torque portion for the second axle is:

M B,Reib,A2 =M B,Reib,rest *B 2, and

wherein a residual friction torque portion for the first axle is:

M B,Reib,A1 =M B,Reib,rest *B 1.

2. The method according to claim 1 , further comprising:

setting the total braking torque distribution with allowance for the minimal recuperation torque to be set on the second axle.

3. The method according to claim 2 , wherein the setting the minimal recuperation torque on the one of the first or second axles comprises:

in response to W1>B1, setting the minimal recuperation torque on the first axle,

wherein the minimal recuperation torque is:

M

B

,

Rek

,

Min

,

=

M

B

,

Ges

*

(

1

-

W

⁢

⁢

2

B

⁢

⁢

2

)

,

wherein the remaining residual friction torque is:

M

B

,

Reib

,

rest

=

M

B

,

Ges

*

W

⁢

⁢

2

B

⁢

⁢

2

,

wherein a residual friction torque portion for the first axle is:

M B,Reib,A1 =M B,Reib,rest *B 1, and

wherein a residual friction torque for the second axle is:

M B,Reib,A2 =M B,Reib,rest *B 2.

4. A braking system of a motor vehicle, the braking system comprising:

a friction braking device;

a recuperative braking device; and

an adjustment and control device configured to set a total braking torque distribution between a first axle and a second axle of the motor vehicle according to a braking torque ratio W1/W2, wherein W1 is a percentage of a total braking torque associated with the first axle, and W2 is a percentage of the total braking torque associated with the second axle,

wherein the total braking torque is composed of a friction braking torque portion of the friction braking device and a recuperative braking torque portion of the recuperative braking device,

wherein the friction braking torque portion is distributed according to a preset friction braking torque ratio B1/B2 to the first and second axles, wherein B1 is a percentage of the friction braking torque associated with the first axle, and B2 is a percentage of the friction braking torque associated with the second axle, and

wherein the adjustment and control device is configured to:

calculate a minimal recuperation torque to be set on one of the first axle or the second axle in response to B1 not being equal to W1; and

set the minimal recuperation torque on the one of the first or second axles, wherein for all driving situations the minimal recuperation torque remains set as a recuperative braking torque portion on the one of the first axle or the second axle,

wherein in response to W1<B1, the adjustment and control device is configured to set the minimal recuperation torque on the second axle,

wherein the minimal recuperation torque is:

M

B

,

Rek

,

Min

,

=

M

B

,

Ges

*

(

1

-

W

⁢

⁢

1

B

⁢

⁢

1

)

,

wherein M B,Ges is the total braking torque,

wherein a remaining residual friction torque is calculated as:

M

B

,

Reib

,

rest

=

M

B

,

Ges

*

W

⁢

⁢

1

B

⁢

⁢

1

,

wherein a residual friction torque portion for the second axle is:

M B,Reib,A2 =M B,Reib,rest *B 2, and

wherein a residual friction torque portion for the first axle is:

M B,Reib,A1 =M B,Reib,rest *B 1, and

wherein in response to W1>B1, the adjustment and control device is configured to set the minimal recuperation torque on the first axle,

wherein the minimal recuperation torque is:

M

B

,

Rek

,

Min

,

=

M

B

,

Ges

*

(

1

-

W

⁢

⁢

2

B

⁢

⁢

2

)

,

wherein the remaining residual friction torque is calculated as:

M

B

,

Reib

,

rest

=

M

B

,

Ges

*

W

⁢

⁢

2

B

⁢

⁢

2

,

wherein a residual friction torque portion for the first axle is:

M B,Reib,A1 =M B,Reib,rest *B 1, and

wherein a residual friction torque for the second axle is:

M B,Reib,A2 =M B,Reib,rest *B 2.

5. The braking system according to claim 4 , wherein the adjustment and control device is further configured to:

set the total braking torque distribution with allowance for the minimal recuperation torque to be set on the one of the first or second axles.

6. A method for controlling a braking system for setting a total braking torque distribution between a first axle and a second axle of a motor vehicle, wherein the braking system comprises a friction braking device and a recuperative braking device, wherein the braking system further comprises a total braking torque that is composed of a friction braking torque portion of the friction braking device and a recuperative braking torque portion of the recuperative braking device, and wherein when a braking request is distributed according to a preset braking torque ratio W1/W2 to the respective first and second axles, the friction braking torque portion is distributed according to a preset friction braking torque ratio B1/B2 to the respective first and second axles, wherein B1 is a percentage of the friction braking torque portion associated with the first axle, B2 is a percentage of the friction braking torque portion associated with the second axle, W1 is a percentage of the total braking torque associated with the first axle, and W2 is a percentage of the total braking torque associated with the second axle, the method comprising:

determining a minimal recuperation torque for one of the first or second axles in response to B1 not being equal to W1; and

setting the minimal recuperation torque on the one of the first or second axles, wherein the minimal recuperation torque remains on the one of the first or second axles for all driving situations as the recuperative braking torque portion, and wherein the setting the minimal recuperation torque on the one of the first or second axles comprises:

in response to W1>B1, setting the minimal recuperation torque on the first axle, wherein the minimal recuperation torque is:

M

B

,

Rek

,

Min

,

=

M

B

,

Ges

*

(

1

-

W

⁢

⁢

2

B

⁢

⁢

2

)

,

wherein a remaining residual friction torque is calculated as:

M

B

,

Re

⁢

⁢

ib

,

rest

=

M

B

,

Ges

*

⁢

W

⁢

2

B

⁢

2

,

wherein a residual friction torque portion for the first axle is:

M B,Reib,A1 =M B,Reib,rest *B 1, and

wherein a residual friction torque for the second axle is:

M B,Reib,A2 =M B,Reib,rest *B 2.