Method for calculating pressure of booster cylinder

Abstract

The invention relates to a method for determining a corrected potential booster cylinder pressure (pF) of a booster brake system (1). The method comprises the following steps: ascertaining (A) at least one engine value (MM) of the booster cylinder engine (20), ascertaining (B) a potential booster cylinder pressure (pF) from the engine value (MM) by means of a correlation model (pF (MM)) between the engine value (MM) and the potential booster cylinder pressure (pF), and ascertaining (C) a booster cylinder pressure (PESP) by means of an ESP pressure sensor (36) in the ESP brake system (8). Furthermore, the method comprises the following steps: comparing (D) the potential booster cylinder pressure (pF) with the booster cylinder pressure (PESP) of the ESP pressure sensor (36) taking into account a time delay (tv) between the potential booster cylinder pressure (pF) and the measured booster cylinder pressure (PESP) of the ESP pressure sensor (36), and correcting (E) the correlation model (pF (MM)) as a function of the ascertained deviation ([Delta] p).

Description

Technical Field

[0001] The invention relates to a method for determining a booster cylinder pressure of a booster brake system. Background Art

[0002] Today's power-assisted brake systems are characterized by being mechanically and / or hydraulically coupled to the driver. This is accomplished via a brake pedal connected to an input rod. In the overall system, the driver's braking desire is detected via the input rod and a pedal feel in the form of a force-displacement characteristic curve is achieved. Subsequently, the pressure increase is achieved via a power-assisted piston, which is hydraulically decoupled from the driver's foot. To regulate this pressure increase, the brake pressure generated by the power-assisted piston is measured by a pressure sensor. In the return plane, the driver's foot is coupled to the wheel brake cylinders by means of a brake cylinder actuated by muscle force, whereby the driver can apply brake pressure with the help of his foot. As a result, in the event of a fault, the vehicle remains brakeable.

[0003] DE 10 2018 222 488 A1 discloses an electrohydraulic assisted vehicle brake system for an autonomously driven land vehicle. This electrohydraulic assisted vehicle brake system is provided with two redundant assisted brake pressure generators, so that during autonomous driving and in the event of a failure of a assisted brake pressure generator, the other assisted brake pressure generator can brake the motor vehicle without driver intervention.

[0004] DE 10 2019 201 536 A1 also discloses an electrohydraulic booster vehicle brake system. In this electrohydraulic booster vehicle brake system, the booster brake pressure generator is designed as a piston-cylinder unit, wherein the piston-cylinder unit is connected to a pressureless brake fluid reservoir via a pressure-limiting valve and a controllable valve. The pressure of the booster brake pressure generator is measured by a pressure sensor arranged on the piston-cylinder unit. The pressure-limiting valve prevents pressure peaks in the vehicle brake system when the booster brake pressure generator is used to close the inlet valve of the hydraulic wheel brake of the vehicle brake system during the pressure buildup. Summary of the invention

[0005] The object of the present invention is to provide a method for determining a booster cylinder pressure, by means of which the booster cylinder pressure can be determined more economically. In addition, a device for carrying out such a method should be provided.

[0006] This object is achieved by a method for determining a boost cylinder pressure having the features of claim 1. In addition, a device for carrying out the method is provided. The correspondingly cited dependent claims reflect advantageous developments of the invention.

[0007] The present invention provides a method for determining a booster cylinder pressure of a booster cylinder brake system. The method comprises the following steps: determining at least one engine value of a booster cylinder engine, determining the potential booster cylinder pressure from the engine value by means of a correlation model between the engine value and the potential booster cylinder pressure, and determining the booster cylinder pressure by means of an ESP pressure sensor in an ESP brake system. The method further comprises the following steps: comparing the potential booster cylinder pressure with the booster cylinder pressure of the ESP pressure sensor while taking into account the time delay between the potential booster cylinder pressure and the measured booster cylinder pressure of the ESP pressure sensor, and correcting the correlation model according to the determined deviation.

[0008] The booster cylinder pressure is understood here as the pressure generated by the booster cylinder for generating the braking force. In the aforementioned prior art, this pressure is usually determined by a pressure sensor arranged directly downstream of the booster cylinder. The potential booster cylinder pressure is a pressure that has not yet been measured but has been calculated. It is assumed for the potential pressure that it corresponds to the measured pressure. However, due to uncertainties in the calculation, there may be minimal differences. An engine value in the sense of the invention is understood here as any measured value that is related to the operating state of the engine and is variable over time. Advantageously, the engine values ​​are calculated with the aid of already known values, so that no additional measuring sensors have to be used.

[0009] Here, the correlation model is a model which can be constructed as a mathematical function, for example, by means of which the booster cylinder pressure can be determined for each engine value. The correlation model includes all factors that influence the booster cylinder pressure. Since it is difficult to include environmental conditions such as temperature or wear of the booster brake system, a high accuracy of the determined booster cylinder pressure can be achieved by constantly correcting the correlation model. The time delay is the time value of the booster cylinder pressure determined by the ESP pressure sensor and the actual pressure or the potential booster cylinder pressure determined by the correlation model.

[0010] The method can accurately obtain the booster cylinder pressure without using a pressure sensor, thereby saving the cost of the pressure sensor and economically obtaining the booster cylinder pressure.

[0011] In a preferred embodiment of the invention, the runtime of the measured booster cylinder pressure of the ESP pressure sensor is measured, and the time delay between the potential booster cylinder pressure and the measured booster cylinder pressure of the ESP pressure sensor is adapted using the runtime. By determining the runtime, the time delay can be determined, so that the pressure difference and thus the correlation model can be calculated more accurately. As a result, the potential booster cylinder pressure can be determined more accurately, thereby improving the control of the booster cylinder. Advantageously, the runtime measurement is performed regularly in order to continuously achieve a high degree of accuracy.

[0012] In a further preferred embodiment of the invention, the run time of the test signal is determined in order to measure the time delay. Such a test signal can include the transmission time. By comparing the reception time and the transmission time, the run time can be determined in a simple manner. As a result, the run time can be measured in a simple manner independently of the braking maneuver, thereby increasing the accuracy of the determined potential booster cylinder pressure.

[0013] Preferably, the torque is used as the engine value for determining the potential booster cylinder pressure. The torque can be measured. It is also possible to calculate this value in the control unit. The torque can thus be determined in a simple manner.

[0014] In an advantageous refinement, the motor current is used as the motor value for determining the potential booster cylinder pressure. Since the motor current is known through regulation via the control unit, this value does not need to be determined. As a result, the motor value can be determined in a simple manner.

[0015] The object of the invention is additionally achieved by a device for carrying out the method. The device comprises a booster cylinder, by means of which a booster cylinder pressure can be generated by means of a booster cylinder engine, an ESP pressure sensor, and a control unit, by means of which the delayed pressure of the booster cylinder pressure can be measured, and in which the potential booster cylinder pressure can be determined by means of a correlation model between the engine value and the potential booster cylinder pressure. By determining the booster cylinder pressure in this way, a booster cylinder pressure measurement without a pressure sensor can be provided. Thus, the advantages mentioned for the method are achieved with this device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the present invention are shown in the drawings and explained in more detail in the following description.

[0017] Figure 1 An embodiment of a power-assisted brake system is shown, in which the booster cylinder pressure is to be ascertained according to the method according to the invention.

[0018] Figure 2 An exemplary embodiment of a method for determining a booster cylinder pressure of a booster brake system is shown, and

[0019] Figure 3 An embodiment of a method for determining a time delay is shown. DETAILED DESCRIPTION

[0020] Figure 1An embodiment of a power-assisted braking system 1 is shown, at which the booster cylinder pressure is to be determined according to the method according to the invention. Here, the power-assisted braking system 1 includes two units 4, 8. The first unit 4 shows a basically known power-assisted system. Therefore, a detailed description is omitted, and only the components relevant to the present invention are discussed. The first unit 4 includes a power-assisted braking pressure generator 12 with a power-assisted cylinder 16, by which the booster cylinder pressure can be generated by the movement of the booster piston 24 via a power-assisted cylinder motor 20. The power-assisted cylinder motor 20 is connected to a control unit 28, by which the motor 20 is controlled. Here, the booster cylinder pressure exists at a location X. In the prior art, in order to determine the booster cylinder pressure, a booster cylinder pressure sensor is usually arranged at this location X. However, in the power-assisted braking system 1, the booster cylinder pressure is determined without using a booster cylinder pressure sensor.

[0021] In the present exemplary embodiment, the second unit 8 is an ESP brake system, by means of which a brake pressure can be applied to the wheel brakes 32. To measure the brake pressure in the ESP brake system 8, an ESP pressure sensor 36 is arranged, which is also connected to the control unit 28 for transmitting the pressure to the control unit. The rest of the ESP brake system 8 is designed in a known manner, so that a detailed description thereof is omitted.

[0022] Figure 2 shows the method for obtaining Figure 1 1. In a first step A, the engine value of the booster cylinder motor 20 is determined. In this embodiment, the torque M is determined. M Since this value is determined in a standardized manner, no additional sensor is required for this purpose. Alternatively, the motor current of the booster cylinder motor 20 can also be determined. Based on the torque M M In the second step B, the potential booster cylinder pressure p is determined F For this purpose, the potential booster cylinder pressure p F With torque M M The correlation between F (M M ). Correlation p F (M M ) can include values ​​such as the transmission characteristics of the booster cylinder motor 20, the elasticity of the brake system and the piston area.

[0023] The potential booster cylinder pressure p is thus determined FFor booster cylinder regulation R, a separate pressure sensor can be omitted. In a third step C, the pressure of the ESP pressure sensor 36 is determined. This pressure is transmitted to the control unit 28. In the control unit 28, in a fourth step D, the determined booster cylinder pressure p F The booster cylinder pressure p of the ESP pressure sensor 36 ESP For comparison. Since the booster cylinder pressure p of the ESP sensor 36 ESP Delayed transmission and signal processing to the control unit 28, the booster cylinder pressure p of the ESP sensor 36 ESP With respect to the desired potential booster cylinder pressure p F With time delay t V When comparing these two values, the booster cylinder pressure p ESP Considering the time delay t V .

[0024] In a fifth step E, in the deviation Δp between the two values ​​determined in the comparison, the correlation p F (M M ) is adapted according to the deviation Δp and stored again to calculate the potential booster cylinder pressure p F Therefore, the potential booster cylinder pressure p can be increased. F accuracy.

[0025] Figure 3 shows the method for determining the time delay t V . For this purpose, in a first determination step M, a test signal is applied between the control unit and the ESP pressure sensor. In a second determination step N, the run time of the test signal is measured. Starting from the run time, a time delay t V This value can then be used according to Figure 2 is updated in the method. By delaying t V The corrected value of the correlation p can be used to improve the accuracy of comparing the two values, thereby obtaining a more accurate correlation p f (M M ).

Claims

1. A method for obtaining a booster cylinder pressure (p F ), the method comprising the following steps: - obtaining (A) at least one engine value (M) of the booster cylinder engine (20); M ), - With the help of engine value (M M ) and potential booster cylinder pressure (p F ) correlation model (p F (M M )), from the engine value (M M ) to obtain (B) the potential booster cylinder pressure (p F ), - Using the ESP pressure sensor (36) in the ESP brake system (8), the booster cylinder pressure (P ESP ), - Taking into account the potential booster cylinder pressure (p F ) and the booster cylinder pressure (P ESP ) time delay (t v ), the potential boost cylinder pressure (p F ) and the booster cylinder pressure (P ESP ) for comparison (D), and - Correct (E) the correlation model (p) according to the deviation (Δp) determined F (M M )).

2. The method according to claim 1, characterized in that Measuring the booster cylinder pressure (P ESP ) and adapt the potential booster cylinder pressure (P F ) and the booster cylinder pressure (P ESP ) time delay (t v ).

3. The method according to claim 2, characterized in that In order to measure the time delay (t v ), find the running time of the test signal.

4. The method according to any one of the preceding claims, characterized in that In order to obtain the potential booster cylinder pressure (P F ), using the torque as the engine value (M M ).

5. The method according to any one of claims 1 to 3, characterized in that In order to obtain the potential booster cylinder pressure (P F ), using the motor current as the motor value.

6. An apparatus for performing the method according to any one of the preceding claims, comprising: - a booster cylinder (16), by means of which a booster cylinder pressure can be generated by means of a booster cylinder engine (20), - an ESP pressure sensor (36), by means of which the booster cylinder pressure (P ESP ) of the delayed pressure, and a control unit (28) in which the engine value (M M ) and potential booster cylinder pressure (P F ) correlation model (p F (M M )) Calculate the potential booster cylinder pressure (P F ).

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