Control device and method for determining the pV characteristic of at least one wheel brake cylinder of a brake system of a vehicle - Patents.com

Abstract

The present invention relates to a method for determining the pV characteristic of at least one wheel brake cylinder (10a) of a braking system of a vehicle, comprising: the method comprising the steps of increasing the pressure in at least one wheel brake cylinder (10a) of the brake system during a measurement time interval, detecting at least once during the measurement time interval a volume quantity representative of a current volume in the at least one wheel brake cylinder (10a) and simultaneously detecting a pressure quantity representative of a current pressure in the at least one wheel brake cylinder (10a), and determining the pV characteristic of the at least one wheel brake cylinder (10a) taking into account the at least one volume quantity and the at least one pressure quantity, wherein, during at least one pressure increase interval prior to the measurement time interval, the pressure acting on at least one closed wheel intake valve and / or the at least one closed gate valve is increased to a limit pressure greater than or equal to 25 bar with an average pressure increase gradient greater than or equal to 50 bar / s.

Description

[Technical field]

[0001] The present invention relates to a method for determining the pV characteristic of at least one wheel brake cylinder of a braking system of a vehicle, and also to a control device for a braking system of a vehicle and a braking system for a vehicle. [Background technology]

[0002] 1a to 1e show coordinate systems illustrating the conventional procedures for determining the pV characteristic of at least one wheel brake cylinder of a vehicle-specific brake system. The conventional procedures described below are known to the applicant as the domestic prior art.

[0003] In the coordinate systems of Figures 1a to 1e, the horizontal axis is the time axis t. The vertical axis of the coordinate system of Figure 1a represents the pressure p in the first wheel brake cylinder of the vehicle-specific brake system (which, however, has three further wheel brake cylinders). The vertical axis of the coordinate system of Figure 1b represents the current intensity I of the control signal provided to the first wheel intake valve (arranged upstream of the first wheel brake cylinder). input1 1c indicates the current intensity I of the control signal output to the other three wheel intake valves of the other three wheel brake cylinders. input2-4 Correspondingly, the vertical axis of the coordinate system of FIG. 1d represents the current intensity I of the control signal provided to the first wheel exhaust valve (located downstream of the first wheel brake cylinder). output1 1e indicates the current intensity I of the control signal output to the other three wheel exhaust valves of the other three wheel brake cylinders. output2-4 The wheel intake valve is a valve that is open when no current is applied, whereas the wheel exhaust valve is a valve that is closed when no current is applied.

[0004] As can be seen in the coordinate system of FIG. 1a, in the conventional treatment described here, the pressure p in the first wheel brake cylinder increases over a measurement time interval ΔtM The brake pressure build-up in the first wheel brake cylinder is caused by the transfer of brake fluid into the first wheel brake cylinder via the first wheel intake valve, which is controlled to be open, while the other three wheel intake valves and all four wheel exhaust valves are controlled to be open for a measurement time interval Δt M The valve is closed during the measurement interval Δt M A volume quantity representative of a current volume in the first wheel brake cylinder is detected at least once during the period and, at the same time, a pressure quantity representative of a current pressure p in the first wheel brake cylinder is detected. A pV characteristic of the first wheel brake cylinder can then be determined on the basis of the at least one volume quantity and the at least one pressure quantity. Summary of the Invention

[0005] The present invention provides a method for determining a pV characteristic of at least one wheel brake cylinder of a braking system of a vehicle with the features of claim 1, a control device for a braking system of a vehicle with the features of claim 7, and a braking system for a vehicle with the features of claim 10.

[0006] The invention provides improved possibilities for an accurate and error-free determination of the pV characteristic of at least one wheel brake cylinder of a vehicle's brake system, such as, for example, the elasticity of at least one wheel brake cylinder and / or the stiffness of at least one wheel brake cylinder. In particular, the wheel-per / wheel brake cylinder-per pV characteristic of the individual wheel brake cylinder (including its pressure transmission mechanism / brake pipe) can be accurately and reliably determined by the invention (for all wheel brake cylinders of the respective brake system). The possibilities offered by the invention allow the pV characteristic to be determined / measured automatically or the values ​​stored as pV characteristic to be automatically adapted to the actual pV characteristic of at least one wheel brake cylinder. If desired, the determined or adapted pV characteristic of at least one wheel brake cylinder can then be stored directly in a controller or in a storage unit. Whereas according to the above-mentioned conventional procedure, such a step could only be performed reliably in the factory during the development and application process of the respective brake system, since the individual wheel brake pipes of the brake system have to be screwed together and / or special expensive equipment is required, the invention allows a reliable determination of the pV characteristic of at least one wheel brake cylinder even outside the factory. When using the possibilities for determining the pV characteristic of at least one wheel brake cylinder provided by the present invention, it is not necessary to open the wheel piping, so that the conventional need for degassing is also eliminated in order to remove as much as possible the air that has entered the brake system during the implementation of the conventional treatment modes by means of some degassing method. Furthermore, this eliminates the conventional risk that residual air components still remain in the brake system despite the implementation of the degassing method. It should also be noted that the use of the possibilities for determining the pV characteristic of at least one wheel brake cylinder provided by the present invention does not require expensive equipment.

[0007] The possibility for determining the pV characteristic of at least one wheel brake cylinder provided by the invention therefore does not result in any loss of time in the use of free time in the factory. The implementation of the above-mentioned conventional procedures can require up to six hours for each measurement, during which the vehicle cannot be used for other tests, with the associated loss of time being often significant. In contrast, the possibility according to the invention often requires less than five minutes to determine the pV characteristic of at least one wheel brake cylinder. The invention also provides the possibility for controlling the quality and tolerance position of at least the wheel brake cylinders of a brake system installed on a vehicle by routine implementation.

[0008] A further particular advantage of the invention is that the pV characteristic of at least one wheel brake cylinder can be redetermined / recalibrated multiple times during operation of the respective brake system without the need for a visit to the workshop for this purpose. This also entails considerable cost savings, since the knowledge of the pV characteristic of at least one wheel brake cylinder can be verified or corrected multiple times to maintain a high level of performance of the respective brake system. The invention thus allows a "true" pV relationship to be determined anew multiple times, thereby countering the effects of ageing effects in the brake system (in particular without the need for a new degassing of at least one wheel brake cylinder of the respective brake system).

[0009] In an advantageous embodiment of the method, during a first pressure build-up interval, the partial volume pressure in the partial volume of the brake system defined by at least one closed gate valve is raised to a limit pressure of at least greater than or equal to 25 bar by the driver braking force acting on the brake pedal of the brake system and / or by activation of an electric brake booster, and at the start of a second pressure build-up interval, the at least one gate valve is opened, thereby transferring brake fluid from the partial volume (48) through the at least one gate valve (28a) into the at least one wheel suction valve (30a) with an average pressure build-up gradient of greater than or equal to 50 bar / s. As will become clear from the following description, the procedure described in this paragraph allows the desired pressure to be sequentially provided in at least one gate valve and at least one wheel intake valve during the pressure build-up interval, whereby the at least one wheel intake valve, the at least one check valve arranged in parallel to the at least one wheel intake valve, and the at least one gate valve are reliably sealed so as not to affect the build-up of pressure in the at least one wheel brake cylinder during the measurement interval, which allows a more accurate and more reliable determination of the pV characteristic of the at least one wheel brake cylinder.

[0010] Preferably, after the at least one pressure build-up interval and before the measurement time interval, the pressure in the at least one wheel brake cylinder is lowered during a pressure drop interval by draining the brake fluid from the at least one wheel brake cylinder via at least one wheel exhaust valve of the brake system which is arranged downstream of the at least one wheel brake cylinder, the draining of the brake fluid via the at least one wheel exhaust valve not affecting the reliable sealing of the at least one wheel intake valve, the at least one check valve and / or the at least one gate valve which occurs during the pressure build-up interval.

[0011] In particular, it is possible to increase the pressure in at least one wheel brake cylinder with an average pressure increase gradient during a measurement time interval that is less than or equal to 35 bar / s. Such a "slow" pressure increase allows an accurate determination of at least one volume quantity and at the same time at least one pressure quantity, so that the pV characteristic can be determined very accurately.

[0012] In a further advantageous embodiment of the method, the pressure acting on at least one closed wheel suction valve and / or at least one closed gate valve is increased during at least one pressure increase interval with an average pressure increase gradient of more than or equal to 50 bar / s to a limit pressure of more than or equal to 25 bar, the limit pressure being sufficient to seal at least one check valve arranged in parallel to the at least one wheel suction valve and / or sufficient to seal at least one gate valve. Thus, the at least one wheel suction valve, the at least one check valve and / or the at least one gate valve are already in their respective closed positions before the measurement time interval, so that during the transfer of brake fluid into at least one wheel brake cylinder carried out in the measurement time interval, no brake fluid volume is "lost" due to insufficient sealing of the at least one wheel suction valve, the at least one check valve and / or the at least one gate valve. This allows a more accurate knowledge of the brake fluid volume displaced into the at least one wheel brake cylinder and therefore also a more accurate and more reliable determination of the pV characteristic.

[0013] In an advantageous further configuration of the method, the pressure in the at least one wheel brake cylinder can be increased during an air clearance close interval to an air clearance closing pressure greater than or equal to 40 bar before the at least one pressure increase interval, and the pressure in the at least one wheel brake cylinder can then be reduced to a starting pressure less than or equal to 5 bar before the at least one pressure increase interval. By the steps described in the paragraphs cited herein, it can be ensured that the air clearance of the at least one wheel brake cylinder is already closed before the measuring time interval, whereby the precision and accuracy of the determined pV characteristic can be further improved.

[0014] The aforementioned advantages can also be ensured by means of a corresponding control device for a brake system of a vehicle, which control device can be further configured according to the above-mentioned method embodiments. For example, the electronic device can be further configured and / or programmed to cause during a first pressure build-up interval or to recognize by means of at least one supplied sensor signal that a partial volume pressure in a partial volume of the brake system defined by at least one closed gate valve has risen to a limit pressure of at least 25 bar at the end of at least a first pressure build-up interval by a driver braking force acting on a brake pedal of the brake system and / or by activation of an electric brake pressure booster, and to open at least one gate valve at the beginning of a second pressure build-up interval so that brake fluid is transferred from the partial volume via the at least one gate valve to the at least one closed wheel intake valve with an average pressure build-up gradient of at least 50 bar / s. In particular, the electronic mechanism may further be configured and / or programmed to activate, during a first pressure build-up interval, as an electric brake intensifier, an electric plunger device integrated in the brake system, an electromechanical brake booster arranged upstream of a brake master cylinder of the brake system, or a pump motor of at least one pump of the brake system, such that the partial volume pressure is increased by the activated electric brake intensifier at least at the end of the first pressure build-up interval to a limit pressure that is at least greater than or equal to 25 bar.

[0015] Furthermore, the above-mentioned advantages are also ensured in the case of a corresponding vehicle brake system with a control device of this type and at least one wheel brake cylinder and at least one wheel intake valve arranged upstream of the at least one wheel brake cylinder and / or at least one gate valve arranged upstream of the at least one wheel brake cylinder, which may also be further configured according to the above-mentioned embodiment of the method. [Brief description of the drawings]

[0016] Further features and advantages of the present invention will now be described with reference to the drawings. [Figure 1a] 1 shows a coordinate system illustrating a conventional procedure for determining the pV characteristic of at least one wheel brake cylinder of a vehicle-specific brake system. [Figure 1b] 1 shows a coordinate system illustrating a conventional procedure for determining the pV characteristic of at least one wheel brake cylinder of a vehicle-specific brake system. [Figure 1c] 1 shows a coordinate system illustrating a conventional procedure for determining the pV characteristic of at least one wheel brake cylinder of a vehicle-specific brake system. [Figure 1d] 1 shows a coordinate system illustrating a conventional procedure for determining the pV characteristic of at least one wheel brake cylinder of a vehicle-specific brake system. [Figure 1e] 1 shows a coordinate system illustrating a conventional procedure for determining the pV characteristic of at least one wheel brake cylinder of a vehicle-specific brake system. [Figure 2a] FIG. 2 is a schematic diagram of a brake system to illustrate an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2b] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2c]1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2d] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2e] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2f] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2g] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2h] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2i] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2j] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Figure 2k] 1 shows a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system. [Diagram 3] FIG. 2 is a schematic diagram of one embodiment of a control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 2a to 2k show a schematic diagram of a brake system and a coordinate system for illustrating an embodiment of a method for determining the pV characteristic of at least one wheel brake cylinder of a brake system.

[0018] Fig. 2a shows an example of a vehicle brake system, in which the method for determining the pV characteristic of at least one wheel brake cylinder 10a described below can be used. It is pointed out, however, that the feasibility of the method described below is not limited to the type of brake system outlined in Fig. 2a, nor to a specific vehicle type of a vehicle / automobile equipped with the respective brake system. That is to say, the total number of just four wheel brake cylinders 10a-10d of the brake system, as shown for example in Fig. 2a, should be interpreted as merely exemplary. The first wheel brake cylinder 10a and the second wheel brake cylinder 10b are coupled to a first brake circuit of the brake system, whereas the third wheel brake cylinder 10c and the fourth wheel brake cylinder 10d are coupled to a second brake circuit of the brake system.

[0019] In the method described below, the wheel-by-wheel / wheel brake cylinder-by-wheel pV characteristic of the first wheel brake cylinder 10a is determined. However, the method described below can be correspondingly implemented for the other three wheel brake cylinders 10b to 10d. If desired, the procedure described below may also be used to determine the pV characteristics of one or more of the wheel brake cylinders 10a to 10d. This of course also applies to vehicles / automobiles with fewer or more than four wheel brake cylinders 10a to 10d, such as for example three-axle vehicles.

[0020] The embodiment of the method depicted in FIG. 2a to FIG. 2k begins, for example, with closing the air clearance of at least the first wheel brake cylinder 10a, so that the so-called air clearance closing interval Δt clearanceDuring the air clearance close interval Δt, the pressure in at least the first wheel brake cylinder 10a is increased to an air clearance close pressure greater than or equal to 40 bar. clearance During the air clearance close interval Δt, all brake linings of all wheel brake cylinders 10a to 10d may be fully applied by the pressure rise created in the wheel brake cylinders 10a to 10d, thereby ensuring that the air clearance of the wheel brake cylinders 10a to 10d does not affect the method steps described below. clearance The pressure rise occurring in at least the first wheel brake cylinder 10a during may in particular be greater than or equal to 80 bar, for example greater than or equal to 120 bar, in particular greater than or equal to 180 bar, although the stated values ​​should only be interpreted as examples.

[0021] The braking system shown in Figure 2a has an air clearance close interval Δt clearance The motorized brake booster has, for example, an electric plunger arrangement 12 for generating a brake boost in at least the first wheel brake cylinder 10a during the air clearance close interval Δt. The motorized plunger arrangement 12 can in particular be a piston-cylinder arrangement integrated in the brake system, in particular an IPB arrangement (Integrated Power Brake). However, instead of or as a complement to the motorized plunger arrangement 12, other types of motorized brake booster can also be used, such as, for example, an electromechanical brake booster supported upstream of a brake master cylinder 14 of the brake system or a pump motor of at least one pump of the brake system, which is connected to the air clearance close interval Δt. clearanceIt should be noted that the driver braking force acting on the brake pedal 16 of the brake system and detectable in particular by means of the rod distance sensor 18 and / or by means of the distance difference sensor 20 may also be used or used in combination to generate a brake boost in at least the first wheel brake cylinder 10a during the braking. Even if the brake system does not have an electric brake booster, the driver braking force acting on the brake pedal 16 of the brake system and detectable in particular by means of the rod distance sensor 18 and / or by means of the distance difference sensor 20 may also be used or used in combination to generate a boost in at least the first wheel brake cylinder 10a. From the driver braking force, it is then possible to reliably assess the boost in pressure caused by the driver braking force at least in the brake master cylinder 14 and / or the volume displaced by the driver braking force by means of characteristic curves which are usually stored in a computer. The use of a sensor for measuring the volume displaced by the driver braking force is therefore often not necessary. In some cases, the driver or operator or mechanic of the respective vehicle may be required to apply a correspondingly large driver braking force to the brake pedal 16 of the vehicle by means of optical signals, acoustic signals and / or image displays.

[0022] The coordinate systems of Figures 2b to 2k each have a time axis t as the horizontal axis. The coordinate system of Figure 2b has a pressure p 12 2c, while the vertical axis of the coordinate system of FIG. 2c denotes the displacement distance x of the piston of the motorized plunger device 12 from its starting position. The displacement distance x can be determined, for example, using a rotor position sensor 22 of the motor 24 of the motorized plunger device 12. In an optional embodiment, the motor 24 of the motorized plunger device 12 may additionally further comprise a motor current sensor 26.

[0023] In the example of Fig. 2a, the motorized plunger device 12 is connected to a first brake circuit of the brake system via a first gate valve 28a and to a second brake circuit of the brake system via a second gate valve 28b. The coordinate system of Fig. 2d and Fig. 2e is represented by a vertical axis representing the current intensity I28a and the current intensity I of the control signal output to the second gate valve 28b. 28b As can be seen in Fig. 2a, gate valves 28a and 28b are each valves that are closed in the absence of current.

[0024] Furthermore, in the brake system of Fig. 2a, a wheel intake valve 30a to 30d is arranged upstream of each wheel brake cylinder 10a to 10d, and a wheel exhaust valve 32a to 32d is arranged downstream of each wheel brake cylinder 10a to 10d. The wheel intake valves 30a to 30d are open without current, whereas the wheel exhaust valves 32a to 32d are closed without current. Using the vertical axis of the coordinate system of Fig. 2f, the current intensity I of the control signal output to the first wheel intake valve 30a arranged upstream of the first wheel brake cylinder 10a is expressed as 30a The current strength I of the control signal provided to the other wheel intake valves 30b to 30d is shown. 30b-30d is reproduced using the vertical axis of the coordinate system of FIG. 2g. The first wheel exhaust valve 32a, which is arranged downstream of the first wheel brake cylinder 10a, is reproduced using the vertical axis of the coordinate system of FIG. 2h. 32a are activated by the control signals shown in the figure. The current strength I 32b-32d is shown using the vertical axis of the coordinate system of FIG. 2i.

[0025] The first brake circuit of the braking system of Fig. 2a is further coupled to the brake master cylinder 10 via a first decoupling valve 34a, while the second brake circuit is coupled to the brake master cylinder 10 via a second decoupling valve 34b. As can be seen in Fig. 2a, the decoupling valves 34a and 34b are each valves that are open without current. The vertical axis of the coordinate system of Fig. 2j represents the current intensity I 34a 2k, the vertical axis of the coordinate system of FIG. 2k represents the current intensity I of the control signal output to the second decoupling valve 34b. 34bBy closing both decoupling valves 34a and 34b, all wheel brake cylinders 10a to 10d are decoupled from the brake master cylinder 10, in which case the driver, acting on the brake pedal 16, can intervene in the simulator 38 via the simulator coupling valve 36 to slow down if necessary. In an optional embodiment, the brake master cylinder 14 can further be coupled to a brake fluid reservoir 42 via a reservoir decoupling valve 40. A pressure sensor 44 can likewise be coupled to the brake master cylinder 14.

[0026] Based on the above-described configuration of the brake system of FIG. 2 with the valves 28a, 28b, 30a to 30d, 32a to 32d, 34a, and 34b, the air clearance close interval Δt clearance In order to close the air clearances of all wheel brake cylinders 10a to 10d by means of the motorized plunger device 12 during the air clearance closing interval Δt, the brake fluid is transferred into the wheel brake cylinders 10a to 10d via the open gate valves 28a and 28b and the open wheel intake valves 30a to 30d, while the wheel exhaust valves 32a to 32d and the decoupling valves 34a and 34b are kept or controlled in a closed state. This is reproduced using the coordinate system of Fig. 2d to 2k. The closing of the air clearances of the wheel brake cylinders 10a to 10d provides an advantageously reproducible prerequisite for carrying out the method steps described below, but is, however, only an optional method step in the embodiment of the method described here. Air clearance closing interval Δt clearance Thereafter, the pressure in the first wheel brake cylinder 10a is reduced to a starting pressure less than or equal to 5 bar, preferably equal to atmospheric pressure.

[0027] In the method described herein, the pressure acting on at least the first closed wheel intake valve 30a and / or the first closed gate valve 28a is increased for at least one pressure increase interval Δt increase1 and Δt increase2It is particularly advantageous to increase the pressure to a limit pressure of greater than or equal to 25 bar with an average pressure increase gradient of greater than or equal to 50 bar / s during the at least one pressure increase interval Δt increase1 and Δt increase2 The average pressure build-up gradient of the pressure rise in the first wheel brake cylinder 10a during each pressure rise interval Δt can be greater than or equal to 60 bar / s, for example greater than or equal to 70 bar / s, in particular greater than or equal to 80 bar / s. In particular, the average pressure build-up gradient can be greater than or equal to 60 bar / s, for example greater than or equal to 70 bar / s, in particular greater than or equal to 80 bar / s. increase1 and Δt increase2 The pressure rise occurring at each valve 28a or 30a during each pressure rise interval Δt increase1 and Δt increase2 It may be the quotient obtained by dividing the period by the number of years.

[0028] A pressure applied to at least the closed first wheel intake valve 30a and / or the closed first gate valve 28a, with an average pressure increase gradient of greater than or equal to 50 bar / s up to a limit pressure of greater than or equal to 25 bar, is applied to at least the first wheel intake valve 30a, the first check valve 46a arranged in parallel with the first wheel intake valve 30a, and the first gate valve 28a, during at least one pressure increase interval Δt increase1 and Δt increase2 A pressure bias is generated between the first wheel inlet valve 30a, the first check valve 46a and the first gate valve 28a, so that the valve discs are pressed against their respective valve seats, thereby creating a (substantially) fluid-tight seal of at least the first wheel inlet valve 30a, the first check valve 46a and the first gate valve 28a, the advantages of which will be described further below.

[0029] In particular, a pressure with an average pressure increase gradient of greater than or equal to 50 bar / s up to a limit pressure of greater than or equal to 25 bar is maintained for all closed gate valves 28a and 28b and for all closed wheel intake valves 30a to 30d for at least one pressure increase interval Δt increase1 and Δt increase2 In this case, this generates both a pressure bias of the gate valves 28a and 28b and of the wheel suction valves 30a to 30d and their respective check valves 46a to 46d arranged in parallel with the respective wheel suction valves 30a to 30d, so that the valve bodies of the respective valves 28a and 28b, 30a to 30d, 46a to 46d are pressed against their respective valve seats and thus the valves 28a and 28b, 30a to 30d, 46a to 46d are sealed. In particular, the valve bodies of the check valves 46a to 46d are pressed against their respective valve seats so that the check valves 46a to 46d are optimally closed. This sealing of the valves 28a and 28b, 30a to 30d, 46a to 46d, especially caused by a relatively large pressure build-up gradient, prevents leakage that may occur in valves that are not reliably sealed due to manufacturing tolerances, especially those in the check valves 46a to 46d, during the subsequent pressure build-up in the first wheel brake cylinder 10a (described further below), which may result in volume "lost". Thus, at least one pressure build-up interval Δt increase1 and Δt increase2 A number of method steps carried out in between result in an advantageous preconditioning of the valves 28a and 28b, 30a to 30d, 46a to 46d for an accurate and error-free determination of the pV characteristic.

[0030] Advantageously, in the method described here, a first pressure increase interval Δt increse1During the second pressure build-up interval Δt, the partial volume pressure in the partial volume 48 of the brake system is increased to a limit pressure greater than or equal to 25 bar. By partial volume 48 is to be understood the volume of the brake system that is bounded by at least the first gate valve 28a, which is closed (and, in an optional embodiment, also by the second gate valve 28b, which is closed), so that by opening at least the first gate valve 28a, a transfer of brake fluid from the partial volume 48 to the first wheel intake valve 30a, which is closed, can occur. Thus, the above-mentioned relatively large average pressure build-up gradient, greater than or equal to 50 bar / s, is sufficient to increase the brake fluid pressure in the second pressure build-up interval Δt increse2 2. The above-described method can be implemented by opening at least the first gate valve 28a and possibly also the second gate valve 28b at the beginning of the braking operation. In particular, a "rapid pressure boost" with a relatively large average pressure rise gradient can be generated in all wheel intake valves 30a-30d. The method described here allows the generation of a "rapid pressure boost" with a relatively large average pressure rise gradient even if the motorized plunger device 12, the other type of motorized brake intensifier used, and / or the driver's braking force actually acting on the brake pedal 16 are not suitable for generating such a large gradient. Thus, a relatively cost-effective motorized plunger device 12 with a relatively low-power motor 24 or another type of cost-effective motorized brake intensifier can also be advantageously used to implement the method described here. Even the driver's braking force acting on the brake pedal 16 can be utilized to generate a relatively large average pressure increase gradient by the advantageous manner described herein, for which the driver of the respective vehicle is required to actuate the brake pedal 16, possibly by means of optical signals, by means of acoustic signals and by means of visual displays.

[0031] As can be seen based on the coordinate system of Figs. 2d to 2k, the valves 28a, 28b, 30a to 30d, 32a to 32d, 34a, and 34b are controlled to rotate for at least one pressure rise interval Δtincrease1 and Δt increase2 Then, in the method described here, the second pressure rise interval Δt increase2 At the start of the flow, the gate valves 28a and 28b are first opened "abruptly," which causes a "rapid" pressure increase at the wheel intake valves 30a-30d and their check valves 46a-46d, thereby ensuring the sealing of the valves 28a, 28b, 30a-30d, 32a-32d. The first wheel intake valve 30a is then also opened.

[0032] At least one pressure rise interval Δt increase1 and Δt increase2 followed by the measurement time interval Δt measure Before the pressure drop in the first wheel brake cylinder 10a, the pressure drop interval Δt decrease This is done by draining the brake fluid from the first wheel brake cylinder 10a through the first wheel drain valve 32a. In addition, the first decoupling valve 34a may be opened for a short period of time. This reduces the pressure drop interval Δt decrease The sealing of the valves 28a, 28b, 30a to 30d, 32a to 32d that remain closed during the pressure drop interval Δt decrease 3. The first wheel brake cylinder 10a is not affected by the reduction in pressure in the first wheel brake cylinder 10a that occurs during the first wheel brake cylinder 10a depressurization. Furthermore, the reduction in pressure in the first wheel brake cylinder 10a that occurs by draining the brake fluid from the first wheel brake cylinder 10a through the first wheel drain valve 32a does not require a reset of the motorized plunger device 12, so that at this point it is guaranteed that the leak hole of the motorized plunger device 12 is / remains closed.

[0033] After carrying out the steps described herein, a measurement time interval Δt measure The optimal starting conditions are obtained for the determination of the pV characteristic of the first wheel brake cylinder 10a, which is carried out during the air clearance close interval Δt clearanceand at least one pressure rise interval Δt increase1 and Δt increase2 The sealing of at least the first wheel intake valve 30a, the first check valve 46a, and the first gate valve 28a during the measurement time interval Δt measure It has been achieved that the determination of the pV characteristic of the first wheel brake cylinder 10a carried out during the period cannot be disturbed.

[0034] In particular, at least the first wheel inlet valve 30a, the first check valve 46a and the first gate valve 28a are "tightly" sealed so that leakage is not an issue even under low applied pressure.

[0035] To determine the pV characteristic of the first wheel brake cylinder 10a, the pressure in the first wheel brake cylinder 10a is measured over a measurement time interval Δt measure During the measurement time interval Δt, the motorized plunger device 12 is used to move the brake fluid through the first gate valve 28a and the first wheel intake valve 30a into the first wheel brake cylinder 10a. measure At least once during the measurement time interval Δt, a volume quantity x representative of the current volume in the first wheel brake cylinder 10a and at the same time a pressure quantity p representative of the current pressure in the first wheel brake cylinder 10a are detected. Preferably, the pressure in the first wheel brake cylinder 10a is measured during the measurement time interval Δt measure During this time, the pressure is increased with an average pressure increase gradient of less than or equal to 35 bar / s, so that the pV course of the pressure in the first wheel brake cylinder 10a can be easily followed with a number of measurement steps for simultaneously determining the pressure quantity p and the volume quantity x.

[0036] As pressure quantity p, for example, the pressure in the first wheel brake cylinder 10a can be measured by means of a pressure sensor 50. As volume quantity x, the displacement distance x from the starting position of the piston of the motorized plunger device 12 can be determined, for example, by means of a rotor position sensor 22 of the motor 24. The current volume in the first wheel brake cylinder 10a can be calculated on the basis of the displacement distance x and the radius r of the piston of the motorized plunger device 12. Therefore, no volumetric flow measurement is necessary. In addition, in particular the at least one pressure rise interval Δt increase1 and Δt increase2 The sealing of at least the first wheel suction valve 30a, the first check valve 46a and the first gate valve 28a occurring during ensures that the displacement distance x corresponds (substantially) to the current volume in the first wheel brake cylinder 10a.

[0037] The pV characteristic of the first wheel brake cylinder 10a is then determined taking into account at least one volume quantity x and at least one pressure quantity p. As pV characteristic, individual values ​​or pV characteristic curves may be alternatively determined. It should be pointed out once again that the determined pV characteristic may be a wheel-per-wheel / wheel brake cylinder-per-pV characteristic. As pV characteristic, for example, the elasticity E of the first wheel brake cylinder 10a may be determined according to equation (Gl.1) or the stiffness Σ of the first wheel brake cylinder 10a according to equation (Gl.2).

[0038] (Gl.1) E=(π*x*r 2 / p)-K

[0039] (Gl.2) Σ=(p / π*x*r 2 ΔV)-K'

[0040] K and K' respectively represent correction values ​​defined by the internal elasticity and stiffness of the brake system.

[0041] FIG. 3 is a schematic diagram of one embodiment of a control device.

[0042] The applicability of the control device 52 described below is not limited to a particular type of brake system, nor to a particular vehicle type / automobile type of vehicle / automobile equipped with the respective brake system.

[0043] The control device 52 has an electronic mechanism 54, the first slave unit 56 of which is configured and / or programmed for switching at least one wheel intake valve of the brake system arranged upstream of at least one wheel brake cylinder of the brake system and / or for switching at least one gate valve of the respective brake system arranged upstream of at least one wheel brake cylinder. The first slave unit 56 can in particular be configured and / or programmed as a pressure regulator actuator and a valve actuator of the respective brake system. The first slave unit 56 is configured and / or programmed, inter alia, for first increasing the pressure acting on at least one closed wheel intake valve and / or at least one closed gate valve during at least one pressure increase interval, at least to a limit pressure of greater than or equal to 25 bar, with an average pressure increase gradient of greater than or equal to 50 bar / s, prior to at least one measurement carried out for determining the pV characteristic of the at least one wheel brake cylinder. Possibilities for advantageously transferring brake fluid into at least one wheel brake cylinder have already been enumerated above. Only after this step does the first slave unit 56 increase the pressure in the at least one wheel brake cylinder by transferring brake fluid into the at least one wheel brake cylinder via at least one wheel intake valve and / or at least one gate valve during a measurement time interval.

[0044] Furthermore, the second slave unit 58 of the electronics 54 is configured and / or programmed to determine a pV characteristic of at least one wheel brake cylinder taking into account at least one volume quantity determined during a measurement time interval and representative of the current volume in at least one wheel brake cylinder and at least one pressure quantity determined simultaneously and representative of the current pressure in at least one wheel brake cylinder. Examples for the volume quantity, pressure quantity and pV characteristic have already been given above. For example, the processing of the recorded pressure and volume signals is carried out using a suitable data evaluation program, such as for example Matlab or Python. If necessary, a third slave unit 60 of the electronics 54 may further be configured / programmed for a plausibility check of the determined pV characteristic and for data processing. For example, the curve of the pV characteristic can be calculated using the third slave unit 60 by using a fitting curve. The finally obtained pV characteristic and / or further required intermediate values ​​and parameters can be selectively stored in the volatile memory 62 or in the non-volatile memory 64.

[0045] The determination of the PV characteristic of at least one wheel brake cylinder may be selectively initiated by a manual trigger 66 or a wireless trigger 68. A corresponding initiation signal 70 is then output to all slave units 56, 58, 60 of the control device 52.

[0046] The determination of the pV characteristic can be performed without irritating the driver, especially when the vehicle is stationary. The determined pV characteristic of the at least one wheel brake cylinder can then be output to at least one brake system control 72. Optionally, the determined pV characteristic can be displayed in the vehicle or sent wirelessly to the factory.

[0047] The above process can also be performed several more years after the brake system is put into service to recalibrate the pV characteristics, which will positively impact the brake performance and durability limits of the brake system.

[0048] If desired, at the end of the above-described process, a common pressure boost can also be generated in all four wheel brake cylinders 10a-10d, so that brake fluid is transferred into the four wheel brake cylinders 10a-10d at least via the open wheel inlet valves 30a-30d when the wheel outlet valves 32a-32d are closed. The sum of the pV characteristics of the four wheel brake cylinders 10a-10d is then compared with one specific pV characteristic of all four wheel brake cylinders 10a-10d, so that any deviations can be identified as a leak in one of the individual wheel measurements. [Explanation of symbols]

[0049] 10a-10d Wheel brake cylinder 12 Brake booster, electric plunger device 14 Brake master cylinder 16 Brake pedal 28a-28b Gate valve 30a-30d Wheel suction valve 32a-32d Wheel exhaust valve 46a-46d Check valve 48 Partial Volume 52 Control device 54 Electronic Mechanism p Pressure amount x Volume Δt increase1 First pressure rise interval Δt increase2 Second pressure rise interval Δt measure Measurement Time Interval Δt decrease Pressure Drop Interval Δt clearance Air Clearance Close Interval

Claims

1. A method for determining the p-V characteristic of at least one wheel brake cylinder (10a) of a braking system of a vehicle, comprising: - increasing a pressure (p) in the at least one wheel brake cylinder (10a) of the brake system during a measurement time interval (Δtmeasure) by transferring brake fluid into the at least one wheel brake cylinder (10a) via at least one wheel intake valve (30a) of the brake system arranged upstream of the at least one wheel brake cylinder (10a) and / or via at least one gate valve (28a) of the brake system arranged upstream of the at least one wheel brake cylinder (10a), while at least once during the measurement time interval (Δtmeasure) determining a volume quantity (x) representative of a current volume in the at least one wheel brake cylinder (10a) and simultaneously determining a pressure quantity (p) representative of the current pressure (p) in the at least one wheel brake cylinder (10a); determining said p-V characteristic of said at least one wheel brake cylinder (10a) taking into account said at least one volume quantity (x) and said at least one pressure quantity (p); In the method comprising the steps of: - during at least one pressure increase interval (Δt increas 1, Δt increas 2) prior to said measurement time interval (Δt measure ), increasing the pressure acting on at least one closed wheel suction valve (30a) and / or on at least one closed gate valve (28a) to a limit pressure of greater than or equal to 25 bar with an average pressure increase gradient of greater than or equal to 50 bar / s; The method according to claim 1, further comprising:

2. 2. The method according to claim 1, further comprising increasing a partial volume pressure in the brake system partial volume defined by the at least one closed gate valve during a first pressure increase interval to a limit pressure of at least greater than or equal to 25 bar by actuation of an electric brake intensifier, and opening the at least one gate valve at the beginning of a second pressure increase interval, thereby transferring brake fluid from the partial volume through the at least one gate valve with an average pressure increase gradient of greater than or equal to 50 bar / s into the at least one wheel suction valve.

3. 3. The method according to claim 1, further comprising the step of: after the at least one pressure increase interval (Δt increas 1, Δt increas 2) and before the measurement time interval (Δt measure), the pressure (p) in the at least one wheel brake cylinder (10a) is decreased during a pressure decrease interval (Δt decrease) by draining brake fluid from the at least one wheel brake cylinder (10a) via at least one wheel drain valve (32a) of the brake system which is arranged downstream of the at least one wheel brake cylinder (10a).

4. 4. The method according to claim 1, wherein the pressure (p) in the at least one wheel brake cylinder (10a) is increased with an average pressure increase gradient less than or equal to 35 bar / s during the measurement time interval (Δtmeasure).

5. 5. The method according to claim 1, further comprising increasing the pressure acting on at least one closed wheel suction valve (30a) and / or on at least one closed gate valve (28a) during at least one pressure increase interval (Δtincrease1, Δtincrease2) to a limit pressure of greater than or equal to 25 bar with an average pressure increase gradient of greater than or equal to 50 bar / s, the limit pressure being sufficient to seal at least one check valve (46a) arranged in parallel to the at least one wheel suction valve (30a) and / or being sufficient to seal the at least one gate valve (28a).

6. 6. The method according to claim 1, further comprising increasing the pressure (p) in the at least one wheel brake cylinder (10a) to an air clearance closing pressure greater than or equal to 40 bar during an air clearance closing interval (Δtclearance) prior to the at least one pressure increase interval (Δtincrease1, Δtincrease2) and subsequently decreasing the pressure (p) in the at least one wheel brake cylinder (10a) to a starting pressure less than or equal to 5 bar prior to the at least one pressure increase interval (Δtincrease1, Δtincrease2).

7. A control device (52) for a braking system of a vehicle, comprising: An electronic mechanism (54) configured and / or programmed to: at least for switching a wheel intake valve (30a) of said braking system arranged upstream of at least one wheel brake cylinder (10a) of said braking system and / or at least one gate valve (28a) of said braking system arranged upstream of said at least one wheel brake cylinder (10a), - to increase the pressure (p) in said at least one wheel brake cylinder (10a) during a measurement time interval (Δtmeasure) by transferring brake fluid into said at least one wheel brake cylinder (10a) via said at least one wheel intake valve (30a) and / or said at least one gate valve (28a); to determine the p-V characteristic of the at least one wheel brake cylinder (10a) taking into account at least one volume quantity (x) representative of a current volume in the at least one wheel brake cylinder (10a) determined during the measurement time interval (Δtmeasure) and at least one pressure quantity (p) representative of a current pressure (p) in the at least one wheel brake cylinder (10a) determined simultaneously, A control device (52) for a braking system of a vehicle, comprising the electronic mechanism (54) configured and / or programmed, 1. A control device (52) for a brake system of a vehicle, the control device (52) being further configured and / or programmed for increasing the pressure acting on at least one closed wheel suction valve (30 a) and / or at least one closed gate valve (28 a) to a limit pressure of greater than or equal to 25 bar with an average pressure increase gradient of greater than or equal to 50 bar / s during at least one pressure increase interval (Δt measure, Δt increase 2) prior to the measurement time interval (Δt measure).

8. The electronic mechanism (54) is further configured and / or programmed to cause, during a first pressure build-up interval (Δt increas1 ), that a partial volume pressure in the brake system partial volume (48) defined by the at least one closed gate valve (28 a) is raised to a limit pressure of at least greater than or equal to 25 bar by the operation of the electric brake intensifier (12) at least at the end of the first pressure build-up interval (Δt increas1 ); or the electronic mechanism (54) is configured and / or programmed to recognize, using at least one supplied sensor signal, and to open the at least one gate valve (28a) at the beginning of a second pressure build-up interval (Δt increas2) so as to move brake fluid from the partial volume (48) through the at least one gate valve (28a) into the at least one closed wheel suction valve (30a) with the average pressure build-up gradient greater than or equal to 50 bar / s.

9. 9. The control device (52) according to claim 8, wherein the electronic mechanism (54) is configured and / or programmed for activating an electric plunger device (12) integrated in the brake system as the electric brake intensifier (12) or a pump motor of at least one pump of the brake system during the first pressure build-up interval (Δt increas1) such that the partial volume pressure is raised by the activated electric brake intensifier (12) at least at the end of the first pressure build-up interval (Δt increas1) to the limit pressure which is at least greater than or equal to 25 bar.

10. A control device (52) according to any one of claims 7 to 9; said at least one wheel brake cylinder (10a); at least one wheel suction valve (30a) arranged upstream of the at least one wheel brake cylinder (10a) and / or at least one gate valve (30a) arranged upstream of the at least one wheel brake cylinder (10a).

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