Method for determining a probable master cylinder internal pressure and device for determining a probable master cylinder internal pressure

Abstract

Procedure for determining a probable master cylinder internal pressure with the steps: Estimating and / or measuring an adjustment path s of a brake input element (12, 14, 22, 24) arranged on a master brake cylinder (10) of a brake system from its initial position (S1); Estimating and / or measuring a first hydraulic fluid volume flow q MC1 a hydraulic fluid of the brake system from or into a first pressure chamber (10a) of the master brake cylinder (10) and a second hydraulic fluid volume flow q MC2 the hydraulic fluid from or into a second pressure chamber (10b) of the master brake cylinder (10) (S2); and Determine the probable master cylinder internal pressure p MC (t) at least taking into account the estimated and / or measured adjustment path s, the estimated and / or measured first hydraulic fluid volume flow q MC1and the estimated and / or measured second hydraulic fluid volume flow q MC2 (S3).

Description

[0001] The present invention relates to a method for determining a probable internal pressure of a brake master cylinder. The present invention also relates to a device for determining a probable internal pressure of a brake master cylinder. Furthermore, the present invention relates to an electromechanical brake booster, an ESP control system, and a braking system for a vehicle. State of the art

[0002] DE 102011 080 431 A1 describes a braking system for a vehicle. The braking system comprises at least one pre-pressure sensor, which is intended to determine the pressure present in the master brake cylinder.

[0003] DE 10 2010 008 033 A1 relates to a brake system with a brake booster, the piston-cylinder system of which is driven mechanically or hydraulically by an electric motor, in particular by means of transmission means, wherein at least one working chamber of the piston-cylinder system is connected to at least two wheel brakes via hydraulic lines, wherein a 2 / 2-way switching valve is assigned to each wheel brake and the hydraulic connecting lines between the wheel brakes and the piston-cylinder system can be closed separately or jointly by means of the 2 / 2-way switching valves.are, so that a pressure can be regulated in the wheel brakes one after the other in the sense of a multiplex process and / or simultaneously, wherein the electric motor and the switching valves are controlled by a control device, wherein the control device calculates the respective pressure in the wheel brakes by means of a pressure model and transmits the calculated pressure values ​​to at least one ABS / ESP controller and a pressure control device, wherein the pressure control device controls at least the 2 / 2-way switching valves and the electric motor, and in that a prioritization device selects a wheel at least on the basis of the data transmitted by the ABS / ESP controller and transmits this to the pressure control device. The pressure model uses the master cylinder pressure as an input signal, which only corresponds to the wheel pressure in the wheel brake in the steady state (static). The model is designed four times for a vehicle with four wheel brakes.Alternatively, the pressure model can calculate the master cylinder pressure using a stored pressure-volume characteristic curve for the master cylinder. This means that the wheel pressure can also be dynamically adjusted using the corresponding master cylinder position or piston travel. The task of the pressure model is to obtain a dynamic or high-frequency estimate of the wheel cylinder pressure. The piston travel or piston position of the master cylinder is used as the input signal for the pressure model. The volume in the master cylinder is calculated from the volume at the wheel and the piston travel using a summation point. Wheel volume is understood to be the volume of the wheel brake including the supply lines and the working chamber of the master cylinder. The master cylinder pressure is calculated using the volume-pressure characteristic curve of the master cylinder.

[0004] Fig. 1a and Fig. 1b show coordinate systems for explaining deviations between conventionally measured pre-pressure values, sensor values ​​processed according to the state of the art, and pressure values ​​present in a master brake cylinder. The abscissas of the coordinate systems of the Fig. 1a and Fig. 1b are the time axis t (in seconds), while the ordinates of the coordinate systems of the Fig. 1a and Fig. 1b represents a pressure (in bar).

[0005] A graph g in Fig. 1a shows conventionally measured pre-pressure values, while a graph g0 in Fig. 1a indicates the (real) pressure values / real pre-pressure values ​​present in the master brake cylinder. It can be seen that signal noise generally occurs in graph g. This signal noise can be eliminated by sensor signal processing, whereby a graph g' with sensor values ​​processed according to the state of the art can be derived from graph g. However, suitable sensor signal processing requires at least a signal processing time Δt. During the signal processing time Δt, however, the pressure / real pre-pressure present in the master brake cylinder can change by a pressure difference Δp.

[0006] Fig. 1b shows an attempt to extrapolate according to equation (Gl 0) p0=p'+α⋅Δt based on a processed sensor value p' of the graph g' and a slope a of processed sensor values ​​of the graph g' a probable pre-pressure p 0 to appreciate. Disclosure of the invention

[0007] The invention provides a method for determining a probable master cylinder internal pressure comprising the steps: Estimating and / or measuring an adjustment travel s of a brake input element arranged on a master brake cylinder of a brake system from its initial position. Estimating and / or measuring a first hydraulic fluid volume flow of a hydraulic fluid of the brake system from or into a first pressure chamber of the master brake cylinder and a second hydraulic fluid volume flow of the hydraulic fluid from or into a second pressure chamber of the master brake cylinder; and Determining the probable master brake cylinder internal pressure at least taking into account the estimated and / or measured adjustment travel, the estimated and / or measured first hydraulic fluid volume flow and the estimated and / or measured second hydraulic fluid volume flow.

[0008] According to a further aspect of the invention, a device for determining a probable master cylinder internal pressure is claimed, comprising: an electronic device which is designed to determine and provide the probable master brake cylinder internal pressure taking into account at least one provided estimated and / or measured first variable relating to an adjustment path of a brake input element arranged on a master brake cylinder of a brake system from its initial position, a provided estimated and / or measured second variable relating to a first hydraulic fluid volume flow of a hydraulic fluid of the brake system from or into a first pressure chamber of the master brake cylinder, and a provided estimated and / or measured third variable relating to a second hydraulic fluid volume flow of the hydraulic fluid from or into a second pressure chamber of the master brake cylinder

[0009] A further aspect of the invention relates to an electromechanical brake booster and an ESP control with a device as described above or according to the claim relating to the device, as well as a braking system for a motor vehicle with a device as described above or according to the claim relating to the device, with an electromechanical brake booster as described above or according to the claim relating to the electromechanical brake booster and / or with an ESP control as described above or according to the claim relating to the ESP control.

[0010] The probable internal pressure of the master cylinder can generally also be understood as the probable pre-pressure. The exclusive use of the term "probable internal pressure of the master cylinder" in the following is for the sake of clarity.

[0011] The device for determining a probable internal pressure of the master brake cylinder can be understood, for example, as a sensor device, an evaluation device, and / or an estimation device. The device for determining a probable internal pressure of the master brake cylinder can also be a control device for at least one brake system component. As explained in more detail below, the device for determining a probable internal pressure of the master brake cylinder can be designed, in particular, as at least part of the control electronics of an electromechanical brake booster and / or as at least part of an ESP control system. Advantages of the invention

[0012] The present invention enables faster and / or more reliable determination of the probable master cylinder internal pressure. Inaccuracies due to signal noise need not be feared when determining the probable master cylinder internal pressure according to the invention. This also eliminates the conventional need for sensor signal processing when determining the probable master cylinder internal pressure according to the present invention. The device for determining the probable master cylinder internal pressure therefore does not require complex evaluation electronics suitable for carrying out the sensor signal processing. The device according to the invention is therefore comparatively simple to design. Accordingly, the corresponding method for determining a probable master cylinder internal pressure can also be implemented using cost-effective components that require little installation space.

[0013] Furthermore, when using the present invention, the conventional problems of delayed determination due to the signal processing time required for sensor signal processing are eliminated. Extrapolation / delay time compensation as in the prior art, which often does not contribute to signal improvement, can thus be dispensed with. While conventional extrapolation cannot react to frequent fluctuations in the admission pressure, for example due to return flow, the subject matter of the present invention also allows a reliable determination / determination of the probable internal pressure of the master brake cylinder in this case. In particular, the present invention offers a model-based determination of the probable internal pressure of the master brake cylinder, ora model-based estimation of a pressure gradient in the master brake cylinder, which provides reliable results with improved accuracy even for a pressure curve in the master brake cylinder with a time-varying gradient.

[0014] In particular, the present invention can be implemented so quickly that there is hardly any risk of the pre-determined probable internal pressure of the master brake cylinder lagging behind the actual pre-pressure. For example, the disadvantage of measured pre-pressure values, which are always greater than the actual pre-pressure during a braking maneuver in which the driver releases the brake pedal, is thus also avoided.

[0015] The probable internal pressure of the master brake cylinder determined by means of the present invention can then be used to control at least one brake system component. For example, an ESP controller of a brake system operated by means of the present invention can use the determined probable internal pressure of the master brake cylinder to control at least one hydraulic component of the brake system, such as, in particular, to control the wheel inlet valves. This is particularly advantageous when a target value of the at least one hydraulic component of the brake system can be optimized with regard to the probable internal pressure of the master brake cylinder. The determined probable internal pressure of the master brake cylinder can be used by the ESP controller, in particular, for runtime compensation / delay time compensation.Likewise, a control system for an electromechanical brake booster of the braking system can advantageously utilize the probable internal pressure of the master brake cylinder for targeted pre-control of the electromechanical brake booster. Since the probable internal pressure of the master brake cylinder can be determined quickly and reliably using the present invention, at least the functioning of the ESP control system and / or the electromechanical brake booster of the braking system itself can be adapted to significant pressure fluctuations in the master brake cylinder.

[0016] In particular, the functionality of the ESP control and / or the electromechanical brake booster of the braking system can be optimized so that pressure fluctuations in the master brake cylinder can be dampened or prevented. This protects braking system components from increased mechanical stress (triggered by strong pressure fluctuations in the master brake cylinder). The service life and functionality of the braking system components can thus be improved.

[0017] In an advantageous embodiment of the method, the probable master brake cylinder internal pressure p MC (t) is determined taking into account at least one measured master cylinder pressure value and / or at least one measured pre-pressure. The present invention is thus also suitable for the improved processing of measured values.

[0018] Advantageously, the probable master cylinder internal pressure p MC (t) is determined by additionally considering a compression modulus K of the hydraulic fluid, an initial volume V0 of the master cylinder when the brake input element is in its initial position, an inner diameter d of the master cylinder, and / or a cross-sectional area A of the master cylinder. Using such a model based on the geometry of the master cylinder, the probable internal pressure of the master cylinder can be determined / specified with increased accuracy.

[0019] In a further advantageous embodiment, to determine the probable master brake cylinder internal pressure p MC (t) a pressure change rate dp MC / dt continuously set with: dpMCdt=KV0−π⋅d24⋅s⋅(qMC1+qMC2+π⋅d24⋅dsdt), where ds / dt is an estimated or measured rate of change of the displacement s of the brake input element and / or an estimated or measured displacement speed of the brake input element. The pressure change rate can then be further evaluated to determine the probable internal pressure of the master cylinder. Furthermore, the pressure change rate can also be taken into account when controlling brake system components.

[0020] Alternatively, to determine the probable master cylinder internal pressure p MC (t) the pressure change rate dp MC / dt can be set continuously with: dpMCdt=KV0−A⋅s(qMC1+qMC2+A⋅dsdt), where ds / dt is the estimated or measured rate of change of the displacement s of the brake input element and / or the estimated or measured displacement speed of the brake input element. This approach also ensures the advantages mentioned above.

[0021] Preferably, the probable master cylinder internal pressure p MC (t) defined as an integral over the pressure change rate dp MC / dt with: pMC(t)=pMC(t0)+∫t0tdpMCdt⋅dt, where p MC (to) is an initial value or a value determined for time t0. The probable internal pressure of the master brake cylinder can thus be determined relatively accurately.

[0022] Likewise, the probable master cylinder internal pressure p MC (t) can be determined by the pressure change rate dp MC / dt with: pMC(t)=pMC∗(t')+dpMCdt⋅(t−t'), where p MC *(t') a master cylinder pressure value measured at time t', a pre-pressure measured at time t' or a probable master cylinder internal pressure p determined for time t' MC(t'). Signal propagation time compensation can also be performed this way. To further increase accuracy, parameter adjustment of the relevant parameters at runtime using a control loop or another learning algorithm would also be possible.

[0023] Preferably, the adjustment travel s is measured and / or estimated using at least one subunit of an electromechanical brake booster. This multifunctionality of the electromechanical brake booster, which is usually equipped with a suitable sensor, eliminates the need to equip the braking system with additional sensors.

[0024] In a further preferred embodiment, the first hydraulic fluid volume flow q MC1 and / or the second hydraulic fluid volume flow q MC2Measured and / or estimated by at least one subunit of an ESP control electronics. The ESP control electronics also typically already have data / sensors for estimating / measuring hydraulic fluid volume flows. Equipping the braking system with additional suitable sensors is therefore not necessary in this case.

[0025] The advantages listed above can also be realized by means of a corresponding device for determining a probable internal pressure of the master brake cylinder. The device can be further developed according to the embodiments of the method.

[0026] An electromechanical brake booster with such a device also realizes these advantages. Equipping the electromechanical brake booster with this device, or integrating the device into the control electronics of the electromechanical brake booster, offers the additional advantage that there is no time delay between determining the probable internal pressure of the master brake cylinder and its consideration by the control electronics, since signal transmission is not necessary.

[0027] The benefits are also guaranteed if an ESP control system is equipped with a corresponding device. Even if the device is integrated into the ESP control system, signal transmission is eliminated before the ESP control system takes the probable internal pressure of the master brake cylinder into account.

[0028] Furthermore, the advantages are also realized by a braking system for a motor vehicle with the device, the electromechanical brake booster and / or the ESP control. Short description of the drawings

[0029] The invention is explained below using embodiments in conjunction with the figures. They show: Fig. 1a and Fig. 1b Coordinate systems for explaining deviations between conventionally measured pre-pressure values, sensor values ​​processed according to the state of the art and pressure values ​​present in a master brake cylinder; Fig. 2a and Fig. 2b is a flowchart and a schematic representation of a master brake cylinder of a brake system for explaining a first embodiment of the method for determining a probable master brake cylinder internal pressure; Fig. 3a to 3c are schematic representations of a first, second and third embodiment of the device for determining a probable master cylinder internal pressure; Fig. 4a and Fig. 4b is a schematic representation of a first embodiment of the braking system and a coordinate system for explaining its operation; and Fig. 5a and Fig. 5b a schematic representation of a second embodiment of the braking system and a coordinate system for explaining its operation. Embodiments of the invention

[0030] Fig. 2a and Fig. 2b show a flow chart and a schematic representation of a master brake cylinder of a brake system for explaining a first embodiment of the method for determining a probable master brake cylinder internal pressure.

[0031] In a method step S1, an adjustment travel s of a brake input element (not shown) arranged on the master brake cylinder 10 is measured or estimated from its initial position. The brake input element can be understood, in particular, as a brake pedal, an input rod, or an output rod. The adjustment travel s can, for example, be an actuation travel of the brake pedal or a rod travel. Preferably, the adjustment travel s is an adjustment travel s of an input rod. However, it should be noted that at least one other variable representing an adjustment of a brake input element can also be measured or estimated, other than the adjustment travel s.

[0032] To measure the adjustment travel s, for example, a rod travel sensor and / or a differential travel sensor can be used. Likewise, the adjustment travel s can be estimated taking into account an actuation travel of the brake pedal, a driver braking force and / or a driver braking pressure. Preferably, the adjustment travel s is measured and / or estimated using at least one subunit of an electromechanical brake booster. For example, a sensor integrated into the electromechanical brake booster can be used to measure the adjustment travel s of the input rod of the electromechanical brake booster. Likewise, a controller of the electromechanical brake booster can be used to estimate the adjustment travel s. This multifunctionality of the at least one subunit of an electromechanical brake booster makes it possible to eliminate the need for additional electronics for measuring and / or estimating the adjustment travel s.Furthermore, in this case, a time-consuming signal / data transmission for the subsequent transmission of the measured and / or estimated adjustment travel s, or a probable master brake cylinder internal pressure taking into account the adjustment travel s, to the control of the electromechanical brake booster is not necessary.

[0033] In a process step S2, a first hydraulic fluid volume flow q MC1 of a hydraulic fluid of the brake system from or into a first pressure chamber 10a of the master brake cylinder 10 is measured and / or estimated. Likewise, in method step S2, a second hydraulic fluid volume flow q MC2of the hydraulic fluid from or into a second pressure chamber 10b of the master brake cylinder 10 is measured and / or estimated. The first pressure chamber 10a can, for example, be defined by a rod piston 12 of the master brake cylinder 10, while the second pressure chamber 10 is defined by a floating piston 14 of the master brake cylinder 10.

[0034] To carry out the method step S2, the first hydraulic fluid volume flow q MC1 and / or the second hydraulic fluid volume flow q MC2 measured and / or estimated by at least one subunit of an ESP control electronics. ESP control electronics usually contains continuously updated data on the hydraulic fluid volume flows q MC1 and q MC2 already present. The multifunctionality of the ESP control electronics also allows for additional electronics to measure and / or estimate the hydraulic fluid flow rates q MC1 and q MC2can be saved. As explained in more detail below, in this case, time-consuming signal / data transmission to the ESP control electronics can also be eliminated.

[0035] Process steps S1 and S2 can be performed in any order or simultaneously. The numbering therefore does not specify a chronological order for the execution of process steps S1 and S2.

[0036] In a subsequent process step S3, the probable master brake cylinder internal pressure p MC (t) at least taking into account the estimated and / or measured adjustment path s, the estimated and / or measured first hydraulic fluid volume flow q MC1 and the estimated and / or measured second hydraulic fluid volume flow q MC2 Such a determination of the probable master cylinder internal pressure p MC(t) can be performed more quickly than the above-mentioned measurement of pre-pressure values ​​and the subsequent sensor signal processing that is usually required. Thus, the probable master cylinder internal pressure p determined by method step S3 is MC (t) is usually more accurate than a value obtained from the measured pre-pressure values ​​and the subsequent sensor signal processing. This allows the actual internal pressure in the master cylinder 10 to be determined / estimated more accurately. Furthermore, the faster determination of the probable internal pressure p in the master cylinder, realized by method step S3, MC (t) can also react more quickly to changes in the current master cylinder internal pressure.

[0037] In an advantageous embodiment of the method, the probable master brake cylinder internal pressure p MC(t) may be determined taking into account a compression modulus K of the hydraulic fluid, an initial volume V0 of the master brake cylinder 10 when the brake input element is in its initial position, an inner diameter d of the master brake cylinder 10 and / or a cross-sectional area A of the master brake cylinder 10. For example, to determine the probable master brake cylinder internal pressure p MC (t) a pressure change rate dp MC / dt are continuously determined according to equation (Gl 1): dpMCdt=KV0−π⋅d24⋅s⋅(qMC1+qMC2+π⋅d24⋅dsdt), where ds / dt is an estimated or measured rate of change of the displacement s of the brake input element and / or an estimated or measured displacement speed of the brake input element.

[0038] However, if the master brake cylinder 10 does not have a cylindrical internal volume, the pressure change rate dp MC / dt also the cross-sectional area A of the master brake cylinder 10 perpendicular to an adjustment direction of its at least one piston 12 and 14 can be used with equation (Gl 2): dpMCdt=KV0−A⋅s⋅(qMC1+qMC2+A⋅dsdt), where ds / dt is the estimated or measured rate of change of the displacement s of the brake input element and / or the estimated or measured displacement speed of the brake input element.

[0039] In both cases, the probable master cylinder internal pressure p MC (t) can be defined as an integral over the pressure change rate dp MC / dt according to equation (Eq 3): pMC(t)=pMC(t0)+∫t0tdpMCdt⋅dt, where p MC (to) is an initial value or a value determined for time t0.

[0040] Likewise, the probable master cylinder internal pressure p MC(t) can be determined by the pressure change rate dp determined by equation (GI 1) or (GI 2) MC / dt according to equation (Eq 4): pMC(t)=pMC∗(t')+dpMCdt⋅(t−t'), where p MC * (t') a master cylinder pressure value measured at time t', a pre-pressure measured at time t' or a probable master cylinder internal pressure p determined for time t' MC (t'). In other cases, the probable master cylinder internal pressure p MC (t) can be determined taking into account at least one measured master cylinder pressure value and / or at least one measured pre-pressure. Thus, there are a variety of options for calibrating the probable master cylinder internal pressure p MC (t) with measured sensor values.

[0041] In an optional process step S4, the probable master brake cylinder internal pressure p MC(t) is taken into account when at least one brake system component is activated. For example, the probable master cylinder internal pressure p MC (t) are used when controlling at least one hydraulic component, in particular the wheel inlet valves. Preferably, at least one target value of the at least one hydraulic component is determined taking into account the probable master brake cylinder internal pressure p MC (t). Especially for runtime compensation / delay time compensation, the probable master cylinder internal pressure p MC (t). Likewise, the probable master cylinder internal pressure p MC (t) can also be used for targeted pre-control of an electromechanical brake booster, as explained in more detail below.

[0042] Fig. 3a to 3c show schematic representations of a first, second and third embodiment of the device for determining a probable master brake cylinder internal pressure.

[0043] The Fig. 3a to 3c, each schematically illustrated device 16 comprises an electronic device (not sketched) which is designed to determine a probable master brake cylinder internal pressure p MC (t) (in a master brake cylinder of a brake system cooperating with the device 16). Optionally, the pressure change rate dp already mentioned above can also be MC / dt can be determined and provided by means of the electronic device of the device 16. Determining at least the probable master brake cylinder internal pressure p MC(t) is taking into account at least one provided estimated and / or measured first variable s1 relating to an adjustment path s of a brake input element arranged on the master brake cylinder from its initial position, a provided estimated and / or measured second variable s2 relating to a first hydraulic fluid volume flow q MC1 a hydraulic fluid of the brake system from or into a first pressure chamber of the master brake cylinder and a provided estimated and / or measured third variable s3 with respect to a second hydraulic fluid volume flow q MC2 of hydraulic fluid from or into a second pressure chamber of the master brake cylinder. For example, the quantities and equations given above can be used for this purpose.

[0044] In the embodiment of the Fig. 3a, the device 16 is a subunit of an ESP controller 18, or rather, is integrated into the ESP controller 18. The second variable s2 and the third variable s3 can be measured and / or estimated by the ESP controller 18 itself. An electromechanical brake booster 20 can be used to measure and / or estimate the first variable s1, which then outputs the first variable s1 to the ESP controller 18. Determining the probable master brake cylinder internal pressure p MC (t) by a device 16 as a sub-unit of the ESP control 18 is associated with the advantage that in this case no complex data transmission is required to provide an output signal s4 with the probable master brake cylinder internal pressure p MC (t) to the ESP controller 18 is necessary. Furthermore, in this case, an additional time delay due to such data transmission is eliminated.

[0045] For example, a transmission time of 100 ms may be necessary for data transmission from an external unit to the ESP control 18. With a pressure gradient of the pre-pressure of 1000 bar / s, the pre-pressure changes by 100 bar during the data transmission from an external unit to the ESP control 18. In contrast, the determination / provision of the probable master brake cylinder internal pressure p MC (t) by the device 16 integrated in the ESP control system takes only 20 ms. With the exemplary pressure gradient of the pre-pressure of 1000 bar / s, the pre-pressure can thus be determined from the pre-determined probable master cylinder internal pressure p MC (t) only deviate by 20 bar.

[0046] The probable master cylinder internal pressure p provided by the output signal s4 MC(t) thus corresponds quite precisely to the currently prevailing master cylinder internal pressure while being considered by the ESP control 18, for example, to control at least one wheel inlet valve. The function of the ESP control 18 is thus advantageously adapted to the currently prevailing master cylinder internal pressure. Optionally, the output signal s4 can be provided with at least the probable master cylinder internal pressure p MC (t) can also be output by the ESP control 18 to the electromechanical brake booster 20. The electromechanical brake booster 20 can thus also reliably adapt its operation to the currently existing master brake cylinder internal pressure, as described below.

[0047] In the embodiment of the Fig. 3b, the device 16 is a subunit of the electromechanical brake booster 20, or is integrated into a control of the electromechanical brake booster 20. The electromechanical brake booster 20 is preferably used to measure and / or estimate the first variable s1. The second variable s2 and the third variable s3 can be measured and / or estimated by the ESP control 18 and subsequently output to the electromechanical brake booster 20. Due to the determination of the probable master brake cylinder internal pressure p MC (t) by means of the device 16 as a sub-unit of the electromechanical brake booster 20, the electromechanical brake booster 20 can determine the probable master brake cylinder internal pressure p MC(t) immediately after the determination. A complex data transmission to provide the output signal s4 with the probable master cylinder internal pressure p MC (t) to the electromechanical brake booster 20 is also omitted in this case. Therefore, no time delay due to such a data transmission needs to be taken into account when using / taking into account the probable master brake cylinder internal pressure p MC (t) by the electromechanical brake booster 20. Therefore, signal propagation time compensation is not necessary. In this case, too, the output signal s4 can be compared with at least the probable master cylinder internal pressure p MC (t) are output from the electromechanical brake booster 20 to the ESP control 18.

[0048] In the embodiment of the Fig. 3c, a device 16 is integrated into the ESP controller 18 and into the electromechanical brake booster 20. The two devices 16 can be designed for communication / data exchange with each other.

[0049] However, it should be noted that the previously described integration of the device 16 into the ESP control 18 and / or the electromechanical brake booster 20 is to be interpreted merely as an example. The device 16 can also be arranged as a separate component in a braking system.

[0050] Fig. 4a and Fig. 4b shows a schematic representation of a first embodiment of the braking system and a coordinate system for explaining its operation.

[0051] The Fig. The braking system schematically illustrated in Figure 4a is equipped with a master brake cylinder 10, an ESP controller (not shown), and the device 16. A brake pedal 22 is connected to the master brake cylinder 10 via at least one input rod 24. A sensor (not shown), such as an actuation travel sensor and / or a rod travel sensor, can optionally be attached to the brake pedal 22. A vacuum brake booster 26 is also arranged between the brake pedal 22 and the master brake cylinder 10. A brake fluid reservoir 28 for providing a hydraulic fluid is also connected to the master brake cylinder 10. The brake fluid reservoir 28 can be connected to the master brake cylinder 10 via at least one sniffer bore.

[0052] The master brake cylinder 14 comprises two (not visible) pressure chambers, each of which is fluidically / hydraulically connected to a brake circuit 32a and 32b via a supply line 30a and 30b. Each of the brake circuits 32a and 32b has two wheel brake cylinders 34a and 34b (preferably hydraulically actuated disc brakes). Brake circuits 32a and 32b can be used either for an X-circuit distribution or for a II-circuit distribution.

[0053] Each wheel brake cylinder 34a and 34b is assigned a wheel inlet valve 36a and 36b (with a check valve arranged in a bypass line). Likewise, each wheel brake cylinder 34a and 34b is assigned a wheel outlet valve 38a and 38b. Furthermore, each of the brake circuits 32a and 32b has a changeover valve 40a and 40b (with a check valve arranged in a bypass line), a high-pressure switching valve 42a and 42b, and a return pump 44a and 44b. The two return pumps 44a and 44b can be arranged on a common shaft 46 of a motor 48. One storage chamber 50a and 50b each, preferably a low-pressure storage chamber 50a and 50b, is connected on the output side to the two wheel outlet valves 38a and 38b of a brake circuit 32a and 32b. A pressure relief valve 52a and 52b is preferably arranged between each storage chamber 50a and 50b and the return pump 44a and 44b of the same brake circuit 32a and 32b.Optionally, the brake system also has at least one pressure sensor, such as a pre-pressure sensor 54.

[0054] During ABS control, hydraulic fluid (or brake fluid) can be drained from at least one wheel brake cylinder 34a and 34b into the accumulator chambers 50a and 50b via the wheel outlet valves 38a and 38b. The hydraulic fluid can then be pumped from the accumulator chambers 50a and 50b back into the master brake cylinder 10 via the return pumps 44a and 44b. In this way, brake fluid consumption during ABS control can be compensated. This allows ABS control to continue indefinitely.

[0055] The coordinate system of the Fig. 4b shows the pressure modulations that usually occur during the return flow in the master cylinder 10, with an abscissa of the coordinate system of the Fig. 4b the time axis t (in seconds) and an ordinate of the coordinate system of the Fig. 4b represents a pressure p (in bar). The graph p r shows the pressure curve (brake pressure curve) caused by the ABS / ESP system in a wheel brake cylinder 34a and 34b. Using the graph p MC * shows a pressure curve in the master brake cylinder 10 that usually occurs during the return flow. It can be seen that pressure fluctuations Δp in the master brake cylinder 10 usually occur during the return flow. MC * may occur.

[0056] However, by means of the device 16, the internal pressure likely present in the master brake cylinder 10 can be determined quickly and reliably, even during the return flow. In particular, the advantage can be utilized that the variables s2 and s3, or data on the first hydraulic fluid volume flow q MC1 and the second hydraulic fluid volume flow qMC2 , are usually already present in the ESP control system during the return flow. Therefore, at least the ESP control system cooperating with / equipped with the device 16 can react comparatively quickly and reliably to the triggered pressure fluctuations Δp MCin the master brake cylinder 10. Especially when controlling components of the braking system whose target values ​​depend on the probable internal pressure of the master brake cylinder, the ESP control system cooperating with / equipped with the device 16 can take the output signal s4 into account. For example, the output signal s4 can be used for runtime compensation and / or delay time compensation. Preferably, the output signal s4 is taken into account by the ESP control system, especially when controlling the wheel inlet valves 36a and 36b. Taking the output signal s4 into account, the ESP control system can adapt its mode of operation, in particular, such that the pressure fluctuations Δp occurring in the master brake cylinder 10 during the return flow MC be minimized.

[0057] Fig. 5a and Fig. 5b shows a schematic representation of a second embodiment of the braking system and a coordinate system for explaining its operation.

[0058] The Fig. 5a, the braking system schematically illustrated has, in contrast to the previous embodiment, an electromechanical brake booster 20. The design of the electromechanical brake booster 20 is not limited to a specific brake booster type. Regarding the other components of the braking system of Fig. 5a, reference is made to the preceding paragraphs.

[0059] In the coordinate system of the Fig. 5b shows the pressure modulations that conventionally occur in such a braking system during the return flow in the master brake cylinder 10, wherein an abscissa of the coordinate system of the Fig. 5b is the time axis t (in seconds) and an ordinate of the coordinate system of the Fig. 4b shows a pressure p (in bar). Again, a graph p r the pressure curve caused by the ABS / ESP system in a wheel brake cylinder 34a and 34b (brake pressure curve) and a graph p MC * a pressure curve that usually occurs during the return flow in the master brake cylinder 10.

[0060] Although the graph p r of the coordinate system of the Fig. 5b with the corresponding graph of the Fig. 4b is identical, during the return flow in a master brake cylinder 10 of a brake system equipped with an electromechanical brake booster 20, significantly larger pressure fluctuations Δp MC* This is due to the decoupling of the brake pedal 22 / the driver's foot from the master brake cylinder by means of the electromechanical brake booster 20. Therefore, a return flow of hydraulic fluid is not absorbed or compensated by a force applied by the driver (i.e., the driver's foot). A braking system equipped with an electromechanical brake booster 20 therefore generally exhibits a lower overall elasticity. If the pressure fluctuations Δp MC * in the master brake cylinder 10 during the return of hydraulic fluid (by the pumps 44a and 44b) is not counteracted, these can conventionally occur more intensely in a braking system equipped with an electromechanical brake booster 20.

[0061] In the braking system of the Fig.5b, however, the ESP control (not shown) and / or the electromechanical brake booster 20 can interact with the device 16. In particular, the ESP control and / or the electromechanical brake booster 20 can be equipped with the device 16. In addition to the advantageous consideration of the output signal s4 by the ESP control, as already described above, the functioning of the electromechanical brake booster 20 can also be adapted to the probable internal pressure of the master brake cylinder determined by the device.In particular, due to the comparatively rapid determination / determinability of the probable internal pressure of the master brake cylinder, the electromechanical brake booster 20 can be specifically controlled / pre-controlled such that, at a (predicted) pressure maximum, the booster force exerted by the electromechanical brake booster 20 on the pistons of the master brake cylinder 10 is reduced. In particular, when a comparatively large amount of hydraulic fluid flows into the master brake cylinder 10, the booster force can thus be reduced. Accordingly, by specifically pre-controlling the electromechanical brake booster 20, its booster force can be increased at a (predicted) pressure minimum. In this case, the electromechanical brake booster 20 can react to a comparatively low flow of hydraulic fluid into the master brake cylinder 10 with an increased booster force.

[0062] In summary, the pressure modulations in the master brake cylinder 10 can be dampened / suppressed, particularly through the interaction of the ESP control and the electromechanical brake booster 20. In this way, many components of the brake system can be protected from increased mechanical stress due to pressure modulations in the master brake cylinder 10. The use of the advantageous device 16 in the brake system can therefore increase the functionality and service life of many components of the brake system.

Claims

[1] Procedure for determining a probable master cylinder internal pressure with the steps: Estimating and / or measuring an adjustment path s of a brake input element (12, 14, 22, 24) arranged on a master brake cylinder (10) of a brake system from its initial position (S1); Estimating and / or measuring a first hydraulic fluid volume flow q MC1 a hydraulic fluid of the brake system from or into a first pressure chamber (10a) of the master brake cylinder (10) and a second hydraulic fluid volume flow q MC2 the hydraulic fluid from or into a second pressure chamber (10b) of the master brake cylinder (10) (S2); and Determine the probable master cylinder internal pressure p MC (t) at least taking into account the estimated and / or measured adjustment path s, the estimated and / or measured first hydraulic fluid volume flow q MC1and the estimated and / or measured second hydraulic fluid volume flow q MC2 (S3). [2] Method according to claim 1, wherein the probable master cylinder internal pressure p MC (t) is determined taking into account at least one measured master cylinder pressure value and / or at least one measured pre-pressure. [3] Method according to claim 1 or 2, wherein the probable master cylinder internal pressure p MC (t) is determined taking additional account of a compression modulus K of the hydraulic fluid, an initial volume V0 of the master brake cylinder (10) when the brake input element (12, 14, 22, 24) is in its initial position, an inner diameter d of the master brake cylinder (10) and / or a cross-sectional area A of the master brake cylinder (10). [4] Method according to claim 3, wherein for determining the probable master cylinder internal pressure p MC(t) a pressure change rate dp MC / dt is set continuously with: dpMCdt=KV0−π⋅d24⋅s⋅(qMC1+qMC2+π⋅d24⋅dsdt), where ds / dt is an estimated or measured rate of change of the displacement s of the brake input element (12, 14, 22, 24) and / or an estimated or measured displacement speed of the brake input element (12, 14, 22, 24). [5] Method according to claim 3, wherein for determining the probable master cylinder internal pressure p MC (t) the pressure change rate dp MC / dt is set continuously with: dpMCdt=KV0−A⋅s⋅(qMC1+qMC2+A⋅dsdt), where ds / dt is the estimated or measured rate of change of the displacement s of the brake input element (12, 14, 22, 24) and / or the estimated or measured displacement speed of the brake input element (12, 14, 22, 24). [6] Method according to claim 4 or 5, wherein the probable master cylinder internal pressure p MC(t) is determined as an integral over the pressure change rate dp MC / dt with: pMC(t)=pMC(t0)+∫t0tdpMCdt⋅dt, where p MC (to) is an initial value or a value determined for time t0. [7] Method according to claim 4 or 5, wherein the probable master cylinder internal pressure p MC (t) is determined by the pressure change rate dp MC / dt with: pMC(t)=pMC∗(t')+dpMCdt⋅(t−t'), where p MC *(t') a master cylinder pressure value measured at time t', a pre-pressure measured at time t' or a probable master cylinder internal pressure p determined for time t' MC (t') is. [8] Method according to one of the preceding claims, wherein the adjustment path s is measured and / or estimated by means of at least one subunit of an electromechanical brake booster (20). [9] Method according to one of the preceding claims, wherein the first hydraulic fluid volume flow q MC1 and / or the second hydraulic fluid volume flow q MC2 is measured and / or estimated by means of at least one subunit of an ESP control electronics (18). [10] Device (16) for determining a probable master cylinder internal pressure, comprising: an electronic device which is designed to take into account at least one provided estimated and / or measured first variable (S1) relating to an adjustment path (s) of a brake input element (12, 14, 22, 24) arranged on a master brake cylinder (10) of a brake system from its initial position, a provided estimated and / or measured second variable (s2) relating to a first hydraulic fluid volume flow (q MC1) of a hydraulic fluid of the brake system from or into a first pressure chamber (10a) of the master brake cylinder (10) and a provided estimated and / or measured third variable (s3) relating to a second hydraulic fluid volume flow (q MC2 ) of the hydraulic fluid from or into a second pressure chamber (10b) of the master brake cylinder (10) the probable master brake cylinder internal pressure ( PMC (t)) to be determined and provided. [11] Electromechanical brake booster (20) with a device (16) according to claim 10. [12] ESP control (18) with a device (16) according to claim 10. [13] Braking system for a motor vehicle with a device (16) according to claim 10, an electromechanical brake booster (20) according to claim 11 and / or an ESP control (18) according to claim 12.

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