Method for operating a braking system of a motor vehicle

Abstract

A method for operating a braking system (10) of a motor vehicle with at least one operating mode with pre-filling to at least partially overcome a clearance of one or more wheel brakes (11, 12, 13, 14) before an expected actuation of a brake pedal (16), wherein actuation of the brake pedal (16) is expected at certain gradients of actuation of controls of the motor vehicle or at certain positions and gradients of actuation of the controls of the motor vehicle, wherein the method comprises an operating mode in which the gradient is determined depending on limit values ​​of the actuation of the controls, characterized in that the operating mode is activated when an index (I) formed from limit values ​​of the actuation of the controls reaches a predetermined value (Sw). n ) exceeds.

Description

[0001] The present invention relates to a method for operating a braking system of a motor vehicle with at least one operating mode including pre-filling to at least partially overcome any air gap in one or more wheel brakes before the anticipated actuation of a brake pedal, wherein actuation of the brake pedal is expected at certain positions and / or gradients of actuation by the operating device, in particular an accelerator pedal, of the motor vehicle. The present invention further relates to a device, in particular a control unit such as a computer program, for executing the program.

[0002] German patent DE 10 2004 030 464 A1 discloses a method for electronic brake control in which the air gap is overcome by pre-filling the servo-hydraulic brake systems when the accelerator pedal is released with a gradient exceeding a minimum gradient. This method assumes that a driver, for example in an emergency situation, will suddenly release the accelerator pedal and that the pre-filling will be activated in this situation.

[0003] German patent application DE 10 2004 039 269 B3 discloses a method for operating a braking system of a motor vehicle with at least one operating mode with pre-filling to at least partially overcome a clearance of one or more wheel brakes before an expected actuation of a brake pedal, wherein actuation of the brake pedal is expected at certain positions and / or gradients of the actuation of operating devices, in particular an accelerator pedal, of the motor vehicle, characterized in that the method includes an operating mode in which the gradient is determined depending on the dynamics and / or limit values ​​of the actuation of the operating devices.

[0004] Document DE 197 45 128 A1 discloses a method for operating a braking system, wherein the operating mode is determined depending on the dynamics and / or limit values ​​of a deceleration requirement.

[0005] The known method allows the brake system to overcome the air gap by pre-filling the brake system only if the driver abruptly releases the accelerator pedal. This is generally only guaranteed in an emergency situation. In a so-called sporty or dynamic driving style, where there is frequent switching between acceleration by pressing the accelerator pedal and deceleration by pressing the brake pedal, and where the accelerator pedal is not usually released abruptly, the air gap in the service brake is therefore not overcome. This is perceived by the driver as a delayed response of the service brake. Disclosure of the invention

[0006] One object of the present invention is to provide a method, a device and a computer program that offers an overcoming of the free play of the wheel brake even outside of dangerous situations.

[0007] This problem is solved by a method for operating a motor vehicle's braking system with at least one operating mode featuring pre-filling to at least partially overcome the air gap of one or more wheel brakes before anticipated brake pedal actuation, wherein brake pedal actuation is expected at certain positions and / or gradients of the actuation of controls, in particular an accelerator pedal, of the motor vehicle, and wherein the method includes an operating mode in which the gradient is determined depending on the dynamics and / or limit values ​​of the actuation of the controls. The gradient of the actuation of the controls, in particular the accelerator pedal, can become arbitrarily small; in principle, it can even be zero.This means that the pre-filling of the brakes, and thus the overcoming of the wheel brake clearance and the application of the brake pads, is activated even with a slow release of the accelerator pedal. According to the invention, an operating state is defined, detected during operation, and activated as needed, in which even a slow release of the accelerator pedal causes the brakes to pre-fill. This operating state is referred to here as "sporty driving style" or "dynamic driving style." In addition, there can be any number of other operating states, in particular a "normal driving style" operating state, in which a minimum rate of accelerator pedal release is necessary to overcome the wheel brake clearance; thus, brake pre-filling, as in the prior art, only occurs in an emergency situation.The dependence of the gradient on the dynamics and / or limit values ​​of the control device actuation means that the type of actuation, such as actuation speed, maximum travel, or maximum pressure, is observed and evaluated over a specific period. Therefore, the brake pre-filling is no longer solely dependent, as in the prior art, on a single release of the accelerator pedal with a minimum gradient, but rather on the actuations of several control devices observed over a predetermined period, particularly the actuation of the accelerator and brake pedals. Furthermore, other vehicle operating parameters, such as speed, dynamics of torque demand (both braking and engine torque), maximum accelerations in both the longitudinal and lateral directions, and the like, can also be taken into account.According to the invention, the operating mode is activated when an index, calculated from the dynamics and / or limit values ​​of the control device's actuation, exceeds a predetermined value. The index is preferably evaluated in a loop, meaning it is continuously evaluated at specific time intervals or upon the occurrence of certain other triggering events, such as after a certain distance has been covered. Preferably, the index is increased by a specific value during the loop-based evaluation of the vehicle's operating parameters whenever the maximum braking demand exceeds an upper threshold.

[0008] Preferably, the operating mode is designed so that pre-filling is activated as soon as the accelerator pedal position is changed to a lower torque demand, i.e., when the accelerator pedal is released. It is further preferably designed so that the operating mode is determined based on the dynamics and / or limit values ​​of a driver-requested torque demand, i.e., the accelerator pedal position, and / or a deceleration demand, i.e., the brake pedal position.

[0009] When requesting driver torque, both the maximum value of the requested torque and the gradient of its change—in other words, the rate at which the accelerator pedal position changes—can be taken into account. Similarly, when requesting deceleration, both the maximum pedal travel or force and the gradient of the brake pedal actuation can be considered.

[0010] In a further preferred embodiment, the index remains unchanged during the loop-based evaluation of the vehicle's operating parameters if the maximum braking demand is below the upper threshold and above a lower threshold. It is further preferably provided that the index is reduced by a specific value during the loop-based evaluation of the vehicle's operating parameters if the maximum braking demand is below the lower threshold.

[0011] The problem mentioned at the outset is also solved by a computer program with program code for carrying out all steps according to a method according to the invention, when the program is executed on a computer. The problem mentioned at the outset is likewise solved by a device, in particular a control unit, with means for operating a braking system of a motor vehicle, in particular a servo-assisted or servo-actuated system, with at least one operating mode including pre-filling to at least partially overcome any free play in one or more wheel brakes before an anticipated actuation of a brake pedal, wherein actuation of the brake pedal is expected at certain positions and / or gradients of the actuation of operating devices, in particular an accelerator pedal, of the motor vehicle, and wherein the device includes an operating mode in which the gradient is determined depending on the dynamics and / or limit values ​​of the actuation of the operating devices. Brief description of the drawings

[0012] An embodiment of the present invention will now be explained in more detail with reference to the accompanying drawings. The drawings show: Fig. 1 a sketch of a servo-assisted hydraulic braking system; Fig. 2 a flowchart of an exemplary embodiment of a method according to the invention. embodiment(s) of the invention

[0013] One in Fig. The servo-assisted hydraulic brake system (wheel brake system) 10 for passenger cars shown in Figure 1 has a brake circuit I assigned to the wheel brakes 11, 12 of the front axle (VA) of the vehicle and a brake circuit II assigned to the wheel brakes 13, 14 of the rear axle (HA). A servo pressure source 15 is connected to both brake circuits I and II, which provides the energy required to generate braking force. The brake system 10 thus has an externally operated service brake. The brake system 10 also includes a manually operated auxiliary brake. This has a master brake cylinder 17 with a hydraulic fluid reservoir 18, which can be actuated by a brake pedal 16. The master brake cylinder 17 is a single-circuit system, i.e., it is connected to brake circuit I via a line 19 and a first valve 20 located in this line. In the position of valve 20 shown, the auxiliary brake therefore only acts on the wheel brakes 11 and 12 of the front axle VA.When the service brake is effective, valve 20 blocks the connection between the master brake cylinder and the wheel brakes 11 and 12. The first valve 20 assigned to the master brake cylinder 17 is therefore subsequently referred to as the shut-off valve.

[0014] The servo pressure source 15 draws hydraulic fluid from the reservoir 18 of the master brake cylinder 17 and pressurizes it to high pressure for the service brake function. Hydraulic fluid withdrawn from the wheel brakes 11 to 14 during service brake operation is returned to the reservoir 18. To isolate brake circuit I from the hydraulic fluid reservoir 18 when the auxiliary brake is applied, a shut-off valve 24 is arranged in a line 23 leading to the hydraulic fluid reservoir. Furthermore, each wheel brake 11 to 14 is assigned two valves 25 and 26 for brake pressure modulation when the service brake is applied.

[0015] The brake system 10 is equipped with an electronic control unit 29, to which, in addition to the valves 20, 24, 25 and 26, a travel sensor 30 detecting the travel of the brake pedal 16 and six pressure sensors 31 to 36 are connected. These sensors detect the pressure generated by the master brake cylinder 17, the pressure supplied by the servo pressure source 15, and the pressures applied to the wheel brakes 11 to 14. While the auxiliary brake operates hydraulically in the conventional manner without the involvement of the control unit 29, the service brake operates electro-hydraulically, i.e.,When the driver of the passenger car presses the brake pedal 16, the electrical position signal detected by the position sensor 30 and, if applicable, other electrical signals are evaluated by the electronic control unit 29 to control the valves 20, 24, 25 and 26 in order to generate brake pressure in the wheel brakes 11 to 14 according to the brake request, which is monitored by the control unit on the basis of the electrical signals from the pressure sensors 31, 33 to 36.

[0016] For the following embodiment of the method according to the invention, an electromechanical braking system is used, such as the piezohydraulic wheel brake device from DE 198 18 156 A1, the electrohydraulic braking system from DE 195 46 647 A1, the electromechanical braking device from DE 103 21 159 A1 and DE 199 43 601 A1.

[0017] Based on the Fig. Section 2 below describes an embodiment of the method according to the invention. The function of the electronic brake prefill (EBP) overcomes the wheel brake clearance by applying the brake pads as soon as the accelerator pedal is released. By overcoming the clearance, the response time of the wheel brake system (service brake) is shortened when the brake pedal is subsequently actuated. This results in a shorter pressure build-up time, thereby reducing the stopping distance. The clearance is overcome by the hydraulic unit, whereby a low wheel pressure is set to apply the brake pads. According to the invention, the activation of the prefill occurs independently of the accelerator pedal gradient, and thus independently of a possible emergency situation. For this purpose, a "sporty" operating mode is defined.In sport mode, pre-filling is no longer activated based on the accelerator pedal position, but rather as soon as the torque demand decreases due to the accelerator pedal position. This means activation occurs when the driver releases the accelerator pedal, regardless of the rate at which the pedal is released. To enable this, the "sport" mode must be recognized based on the driver's driving style. The driver's driving style is determined by the dynamics of the service brake application (one of several driver controls) and / or by measuring the threshold values ​​of this application. Therefore, the driver's brake pedal inputs are recorded and analyzed over a defined period. This involves recording the driver's braking intention, for example, by measuring brake pressure, braking force, and / or pedal travel.If the requested braking force exceeds a certain threshold, the system recognizes sporty driving behavior and switches to "sporty" operating mode. This process is illustrated below using the flowchart. Fig. Figure 2 shows the procedure. It begins in step 101. In step 102, it is checked whether form P vor a first threshold Sw1 is exceeded, P vor > Threshold Sw1. If this is the case, indicated by branch "J", the process branches to step 103; if this is not the case, indicated by branch "N", the process branches to step 104. In step 103, it is checked whether the form P vor larger than a saved pre-printed form P vor,merk Step 104 checks whether the saved form P vor,merk is greater than zero. Is the saved form P vor,merkIf the value in step 104 is greater than zero, the program branches to step 105, indicated by the branch "J". In step 105, it is checked whether the stored form P vor,merk greater than an upper threshold Sw o If this is the case, indicated by the branch "J", the process proceeds to step 106. In step 106, a Deltaindex value is calculated from the difference between the stored pre-printed value and the upper threshold Sw. o formed, Delta index = P vor,merk - Sw o Then, in step 107, index I is increased by the value of the delta index. This increases index I to a maximum value. max limited. If the check in step 105 shows that the saved form P vor,merk smaller than the upper threshold Sw o If this is indicated by the branch "N", then a branch is made in step 108. In step 108, it is checked whether the stored pre-printed form P vor,merk less than a lower threshold Swu If this is the case, indicated by the branch "J", then a branch is made in step 109. In step 109, the overall index is reduced by a constant value, with the overall index being limited to zero at the bottom. If the stored form P is not present during the check in step 108... vor,merk greater than the lower threshold Sw u If the branch is marked with "N", then a branch is made in step 110. In step 110, the stored pre-printed form P is used. vor,merk reset to zero.

[0018] If it was determined in step 103 that the form P vor larger than the saved pre-printed form P vor,merk If this is indicated by the branch "J", then a branch is made in step 111. In step 111, the stored form P is assigned. vor,merk the value of form P vor assigned, whereby the value of the stored form P vor,merk to an upper limit P vor,merk,maxThe process is limited. Then, it branches to step 112. Similarly, it branches from step 110 to step 112, and from steps 103 and 104, if the checks there branch to option "N", it also branches to step 112. In step 112, it is checked whether the overall index I n greater than a threshold Sw n for the overall index. If this is the case, indicated by the branch "J", the "sporty" operating mode is activated in step 113. If the check in step 112 shows that the overall index is not greater than the threshold for the overall index Sw n If the option is marked "N", the "sporty" operating mode is deactivated in step 114. The procedure ends in step 115. From step 115, a loop, possibly with a time delay, branches back to step 101.

Claims

[1] Method for operating a braking system (10) of a motor vehicle with at least one operating mode with a pre-filling for at least partially overcoming a clearance of one or more wheel brakes (11, 12, 13, 14) before an expected actuation of a brake pedal (16), wherein actuation of the brake pedal (16) is expected at certain gradients of actuation of controls of the motor vehicle or at certain positions and gradients of actuation of the controls of the motor vehicle, wherein the method includes an operating mode in which the gradient is determined depending on limit values ​​of the actuation of the controls, characterized by , that the operating mode is activated when an index (I), formed from limit values ​​of the actuation of the operating devices, reaches a predetermined value (Sw n ) exceeds. [2] Method according to claim 1, characterized by, that in this operating mode, pre-filling is activated as soon as the position of the accelerator pedal is changed to a lower torque requirement. [3] Method according to claim 1 or 2, characterized by , that the operating mode is determined depending on the limit values ​​of a driver request torque demand. [4] Method according to any one of claims 1 to 3, characterized by , that the operating mode is determined depending on the limits of a delay request. [5] Method according to any one of the preceding claims, characterized by , that the index (I) is increased by a certain value (delta index) in a loop-shaped evaluation of the operating parameters of the motor vehicle if the maximum braking request is above an upper threshold. [6] Method according to any one of the preceding claims, characterized by, that the index remains unchanged in a loop-shaped evaluation of the vehicle's operating parameters if the maximum braking request is below the upper threshold and above a lower threshold. [7] Method according to any one of the preceding claims, characterized by , that the index is reduced by a certain value in a loop-shaped evaluation of the vehicle's operating parameters if the maximum braking request is below the lower threshold. [8] Computer program with program code for carrying out all the steps according to any one of claims 1 to 7 when the program is executed in a computer. [9] Device with means for operating a braking system of a motor vehicle with at least one operating mode with a pre-filling for at least partially overcoming a clearance of one or more wheel brakes before an expected actuation of a brake pedal, wherein actuation of the brake pedal is expected at certain gradients of actuation of operating devices of the motor vehicle or at certain positions and gradients of actuation of the operating devices of the motor vehicle, wherein the device includes an operating mode in which the gradient is determined depending on limit values ​​of the actuation of the operating devices, characterized by , that the operating mode is activated when an index (I), formed from limit values ​​of the actuation of the operating devices, reaches a predetermined value (Sw n ) exceeds.

Images