JP2019518660A - Method for operating a hydraulic brake system, hydraulic brake system - Google Patents

Abstract

【Task】
The present invention is a method for operating a hydraulic brake system (1) of a motor vehicle, said brake system (1) comprising a brake pedal (2) and a master connected to the brake pedal (2). It has a brake cylinder (3) and at least one brake circuit (4) with at least one wheel brake (9), in which case the braking force amplification is adjusted automatically in dependence on the brake pedal operation On how to do it.
[Solution means]
In this case, brake force amplification is generated by at least the controllable pressure generator (12) in the brake circuit (4), on the one hand depending on the brake pedal actuation, on the other hand the master brake cylinder (3) It can be generated as a function of the hydraulic pressure inside or in the wheel brake (9).
[Selected figure] Figure 1

Description

  The present invention is a method for operating a hydraulic brake system of a motor vehicle, the brake system comprising at least one brake pedal, a master brake cylinder connected to the brake pedal, and at least one wheel brake. The invention relates to a method for automating and adjusting the braking force amplification as a function of the brake pedal operation.

  The invention further relates to a corresponding hydraulic brake system having at least one brake booster, by means of which the braking force amplification can be adjusted.

  Brake systems and methods of the type mentioned at the outset are known from the prior art. Automobiles are usually equipped with a hydraulic brake system, which can also generate braking forces on individual wheels when the driver of the vehicle operates the brake pedal. In this case, a brake booster is normally arranged on the master brake cylinder, and this brake booster is generally configured as a vacuum brake booster and is added by the driver to the brake pedal. The amplified force is amplified and brought into the hydraulic brake system or hydraulic circuit so that, for example, the legally required service brake action is obtained. Thus, the brake booster provides the necessary assist force while at the same time producing a brake pedal feel with a pronounced reaction force characteristic curve that is usual for the driver. This characteristic curve has a deceleration based on the mechanical structure of the vacuum brake booster in a general manner before a perceptually high reaction force acts against the driver. The point in time at which the reaction force rises accordingly is also referred to as the jump-in point or the jump-in effect.

  The known vacuum brake booster uses its functional principle for power assist to always keep the pedal effort and the braking force or the degree of deceleration of the vehicle for the driver despite the varying volume accommodation of the respective wheel brakes. Further guarantee that the correlation and reproducibility between

  A method according to the invention having the features of claim 1 is a brake boost mechanically separated by a controllable brake booster, ie from the brake pedal, without the driver having an unexpected sensation in the brake pedal. It has the advantage that a braking force amplification can be generated by the device. In particular, since the correlation between the pedal effort and the vehicle deceleration is guaranteed by the method of the present invention, the driver always feels comfortable when steering the vehicle. According to the invention, this means that the braking force amplification is produced by at least the controllable pressure generator in the braking circuit, on the one hand depending on the brake pedal actuation, and on the other hand in the master brake cylinder or in the wheel brakes. It is obtained by being generated depending on the fluid pressure of By controlling the pressure generator on the one hand on the basis of the brake pedal actuation and on the other hand on the pressure in the master brake cylinder or in the wheel brake, on the one hand, the desired braking force is generated. It is ensured that the volume is moved into the respective wheel brakes, while the pressure in the master brake cylinder is maintained or adjusted in such a way that the driver has a familiar driving feel to the driver. .

  According to a preferred development of the invention, the brake pedal actuation is detected by means of a pedal stroke sensor. That is, the brake pedal operation is detected by the stroke sensor. In this case, the pedal stroke is measured and the pressure generator is controlled as a function of the measured pedal stroke, whereby in particular the desired or target pressure for the master brake cylinder and thus the driver reaction force are calculated. Ru.

  For this purpose, the desired pressure or reaction force is preferably determined by means of the characteristic map and / or characteristic curve as a function of the detected brake pedal actuation.

  Furthermore, depending on the brake pedal operation, a target pressure for the wheel brake is preferably determined. Thereby, the target pressure of the wheel brake is calculated by the brake pedal operation or the detected pedal stroke. This is done in particular in addition to or in addition to the calculation or determination of the target pressure of the master brake cylinder. Since the calculated target pressure is used as a target value in the control of the pressure generator, in particular only one target value, preferably the target pressure of the master brake cylinder, selectively the target pressure of the wheel brakes In use, if the others do not reach or exceed the uncontrolled target values, the target values are appropriately matched, so that mutually correlated changes of the two target values are obtained.

  Preferably, the pressure generator is controlled in dependence on the brake pedal operation based on the assumed volume accommodation of the wheel brakes. By knowing the volume accommodation of the brake circuit, in particular of the wheel brakes, the pressure generator is such that an unnecessary volume is moved into the brake circuit or into the respective wheel brakes due to the pressure buildup in the master brake cylinder. , Controlled. Preferably, pressure control is superimposed on this in consideration of the pressure in the master brake cylinder, and in this pressure control, the pressure in the brake circuit as well as the pressure in the master brake cylinder is the desired brake at the desired wheel pressure. The control of the pressure generator as well as the control of the valve or valves of the braking circuit are also suitably adapted to maintain or adjust, so as to obtain a pedal / force characteristic curve. In this case, the target pressure characteristic curve or reaction force characteristic curve of the master brake cylinder over the pedal stroke reproduces the pedal depression force change of the vacuum brake booster in order to provide the driver with a familiar pedal feeling. Should be configured as

  For this purpose, the pressure generator is controlled in dependence on the target pressure or target pressure characteristic curve which supplies the corresponding pedal feel for the master brake cylinder or wheel brake.

  The desired pressure characteristic curve is moved by an offset value, preferably in dependence of the idle stroke, in particular the air gap and / or the precharging of the brake circuit. As a result, in particular, the pressure in the master brake cylinder is kept pressureless or at 0 bar until the point of jump-in, and only then the reaction force increases. This achieves the desired conventional pedal effort change for the driver. The increase of the pedal effort until the jump-in force is obtained is preferably fulfilled, in particular, by means of a spring arrangement arranged on the brake pedal. The offset value is in particular determined as the difference between the stroke of the predetermined hydraulic pressure obtained at the end of the jump-in and the stroke stored in the target characteristic curve. In this case, the fluid pressure to be obtained does not necessarily have to be the pressure at the end of the jump-in, but may alternatively be any fluid pressure below this value.

  Furthermore, preferably, in addition to the offset value, the stiffness factor of the brake circuit is calculated and used for the target pressure characteristic curve. In particular, for this purpose, the target pressure characteristic curve is displaced by the offset value, so that the target pressure and the actual pressure overlap each other at the jump-in point. The stiffness factor is then calculated, in particular by means of a division operation, and is transformed back by offsetting. From this stiffness factor, the scaling factor used for the target pressure characteristic curve is obtained, which results in the most recent target pressure characteristic curve. This causes the pedal effort and wheel pressure / vehicle motion to be associated with the vacuum brake booster as in a conventional vehicle, and the altered volume containment and braking system stiffness is the pedal stroke change at the desired deceleration. Guaranteed to produce only.

  A brake system according to the invention having the features of claim 9 wherein the brake booster comprises a controllable pressure generator controlled by a specially configured control unit, said control unit generating pressure The apparatus is characterized in that it is arranged to control the apparatus in accordance with the method according to the invention. In this case, the above-described advantages can be obtained. Preferably, the brake pedal is associated with a spring arrangement which ensures an increase in braking force or reaction force until a jump-in force is reached.

  Preferably, the master brake cylinder and / or the wheel brake each have at least one hydraulic pressure sensor in order to detect the hydraulic pressure present in the master brake cylinder or in the wheel brake.

  Furthermore, preferably, a pedal stroke sensor is associated with the brake pedal, so that brake pedal operation is calculated by monitoring the brake pedal movement and, in particular, the stroke advanced by the brake pedal.

  Furthermore, preferably, the brake circuit comprises at least one operable switching valve between the master brake cylinder and the wheel brake. Since the switching valve is open in particular in a currentless manner, the brake pressure at the wheel brake is always increased by pedaling. When the switching valve is energized, the connection between the brake circuit and the master brake cylinder is closed so that no pressure leaks out of the brake circuit. In this case, the switching valve is connected to the pressure generator, in particular on the discharge side, so that when the pressure generator is controlled, the pressure generated in the brake circuit is held in the braking circuit by the switching valve. Or enhanced.

FIG. 1 is a simplified view of a brake system of a motor vehicle. It is a diagram for demonstrating brake force amplification. FIG. 5 is a diagram illustrating a preferred method for operating the brake system.

  Other advantages and preferred features and combinations of features are described in particular in the description and the claims. Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a simplified view of a hydraulic brake system 1 for a motor vehicle not shown in detail here. The brake system 1 is operated by the driver of the vehicle using the brake pedal 2 when the driver wants to start the brake operation or the deceleration of the vehicle. The brake pedal 2 is connected to the master brake cylinder 3. In this case, the brake pedal 2 may be connected to the master brake cylinder 3 directly or indirectly via a link mechanism in order to move the piston in the master brake cylinder to generate hydraulic pressure.

  The master brake cylinder 3 is fluidly connected to the brake circuit 4. Basically, the brake system 1 may have more than one brake circuit 4. Here, the brake circuit 4 has a high pressure switching valve 5 and a switching valve 6 which are connected in parallel to each other. The high-pressure switching valve 5 is configured in the same manner as the switching valve 6 in a non-current closing type. Following the high-pressure switching valve 5, a discharge valve 7, which is also configured to be currentless closed, is provided. Following the switching valve 6, a suction valve 8 configured to be open without current is provided. The discharge valve 7 and the suction valve 8 are both fluidly connected to the wheel brake 9 of the brake system, which is arranged on one of the wheels of the vehicle. The wheel brake 9 is constructed in a conventional manner and form, and for this purpose it comprises, in particular, at least one brake piston movably mounted in a brake caliper, said brake piston being relative to the wheel It is operable by the hydraulic pressure from the brake circuit 4 in order to be tightened against the non-rotatably connected brake disc. In this case, in particular, the brake disc is tightened between the brake linings of the wheel brakes 9 which are arranged opposite one another, whereby a friction is generated between the brake lining and the brake disc, which friction is hydraulic. The braking torque is generated on the wheel depending on the braking force. Further, a pressure sensor 10 is disposed corresponding to the wheel brake 9, and the pressure sensor 10 monitors the fluid pressure in the wheel brake. Similarly, a pressure sensor 11 is disposed in correspondence with the master brake cylinder 3. The pressure sensor 11 calculates or detects the pressure of the master brake cylinder. Furthermore, the suction side of the pressure generator 12 is fluidly connected between the high pressure switching valve 5 and the discharge valve 7, and in this case, the pressure generator 12 has a discharge side braked between the switching valve 6 and the suction valve 8. It is connected to the circuit 4. The pressure generator 12 is configured as a motor-driven pump in the exemplary embodiment of the invention, which pump, as controlled accordingly by the control unit 13 of the brake system 1, always switches the switching valve and the suction. The fluid pressure between the valve 8 and the wheel brake 9 can be increased.

  In the operated / energized state, the high-pressure switching valve 5 opens in the direction of the pressure generator 12, in which case the outlet valve 7 is operated or controlled in the high-pressure switching valve 7 or pressure generator. Open in the direction of 12. The switching valve 6 opens in the direction of the master brake cylinder 3 and the direction of the suction valve 8 in the operated state. Likewise, the suction valve 8 opens in both directions, ie in the direction of the switching valve 6 as well as in the direction of the wheel brake 9.

  The method described below implemented by the control unit 13 confirms the correlation between the pedal effort and the vehicle deceleration for performing electrical and vacuum free brake force amplification in the closed brake system 1 described herein. It must be. In this case, the main components of the ESP system may be utilized. In particular, the valves 4, 6, 7, 8 as well as the pressure generator 12 are components of many existing ESP systems, so that the additional construction costs for carrying out the method are significantly cheaper.

  According to the illustrated embodiment, the generally provided vacuum brake booster connected between the brake pedal 2 and the master brake cylinder 3 is omitted. Instead, a braking force amplification or braking force support is automated and realized by the pressure generator 12. The braking force amplification is thus caused by the pressure difference via the switching valve 6 so that the driver always obtains a retrofitable correlation between the pedal effort or reaction force and the braking force or vehicle deceleration. In order to counteract the driver at the brake pedal, the reaction force must be controlled via the pedal stroke of the brake pedal 2.

  Since the usable brake fluid volume of the brake system 1 is preset via the pedal stroke of the brake pedal 2, a reduction in wheel pressure or brake pressure, for example by increasing the volume accommodation of the wheel brake 9, and As a result, a reduction in vehicle deceleration occurs. Nevertheless, the pressure in the master brake cylinder and thus the reaction force acting against the brake pedal 2 or the driver are controlled in accordance with the target characteristic curve of the master brake cylinder 3. Therefore, no correlation or repeatability between the reaction force and the vehicle deceleration can be obtained, for example, when the volume fluctuation exceeds 30%. Thus, without other measures, the brake system 1 controls the target pressure of the master brake cylinder which generates the corresponding reaction force and the control target of the wheel pressure of the wheel brake 9 which generates the corresponding deceleration of the vehicle. , Can not get at the same time.

  The correlation between reaction force and vehicle deceleration is ascertained by the method described below. That is, using only one of the existing target values, preferably the target pressure of the master brake cylinder, or optionally the target pressure of the wheel brake 9, no other or uncontrolled target value is obtained. When or exceeds, the target values are properly matched, which results in mutually correlated changes of the two target values.

  The brake pedal 2 is further provided with a pedal stroke sensor 14 for monitoring the movement of the brake pedal 2. Depending on the detected pedal stroke of the brake pedal 2, the control unit 13 firstly uses the characteristic curves dependent on the respective vehicle to obtain the desired pressure for obtaining the desired reaction force at the brake pedal 2. Calculate By knowing the volume accommodation of the brake system 1, the pressure generator 12 is controlled via pilot control in order to move unnecessary volumes into the brake circuit 4 due to the pressure buildup in the master brake cylinder 3. . On top of this, pressure control is superimposed in a suitable manner, using the pressure sensor 11, so that the control of the pressure generator 12 as well as the control of the diverter valve 6 are properly adapted.

  In order to simulate the change in pedaling force or the reaction force of the vacuum brake booster, in particular, the driver can obtain a target pressure characteristic curve which represents the target pressure or the target pressure of the master brake cylinder over the movement stroke of the brake pedal 2. In spite of the automatic brake force support without the vacuum brake booster, it is configured to obtain a familiar driving feel for the driver. The so-called "JumpIn-Effekt" "jump-in effect" is obtained by the target pressure characteristic curve of the master brake cylinder 3 being kept at 0 bar without pressure until the jump-in time.

Therefore, FIG. 2, the pedal pressing force F _P acting against the driver as a reaction _force, the pressure p ₃ of the master brake cylinder 3 and the pressure p ₉ of the wheel brakes _9, are respectively over the pedal stroke s The three diagrams shown are shown in simplified form. In this case, it can be seen that, in the initial position, the departure from a pedaling force F ₂ of 0, pressures p ₃ and p ₉ respectively of 0 bar, is obtained. In the first movement section of the brake pedal 2 to the position s _1, it is associated arranged in the brake pedal 2, only the reaction force F ₂ is increased by the spring device 15 simply shown schematically in Figure 1. When overcoming the stroke s _1, increases from this point, as can be seen by the pressure p ₉ in the wheel brake 9, jump-in effect to take effect. As mentioned above, at this point in time, the pressure p3 in the master brake cylinder ₃ is initially maintained at 0 bar. The pedal effort F ₂ and the pressure p ₃ in the master brake cylinder 3 rise for the first time at a delayed stroke point s ₂ after the jump-in effect is overcome.

  FIG. 3 shows how the target pressure characteristic curve of the master brake cylinder 3 shown in FIG. 2 is defined, and thus how the braking force characteristic of the brake pedal 2 is familiar to the driver. The actual value or the actual characteristic curve is indicated by a solid line, and the target value or the target characteristic curve is indicated by a broken line.

First, at which pedal stroke s the jump-in effect (s ₁ ) starts is calculated (A). The stroke movement amount Δs is calculated from the value from the target pressure characteristic curve corresponding to this. In order to correctly adjust the jump-in effect within the pressure of the master brake cylinder 3, the target pressure for the master brake cylinder is 0 bar up to this calculated stroke. Therefore, the target pressure characteristic curve of the pressure p ₃ in the master cylinder 3, optionally in order to correct the preliminary filling of the air gap or brake system 1 increased exists, it is moved by the offset value Delta] s.

The hydraulic brake system 1 can further change the rigidity of the brake circuit 4. This can be corrected via the stiffness factor f. This is because the target pressure characteristic curve of the wheel brake 9 is moved by the calculated offset value As, whereby the target pressure and the actual pressure are at this point or at a stroke point at which the jump-in effect is started, as shown in FIG. Calculated by overlapping each other as shown in (B). The stiffness factor f is calculated by division processing, and is converted back by offset movement. Then, this is used as a scaling factor for the target pressure characteristic curve of the master brake cylinder 3, whereby the latest target pressure characteristic curve K3 for the master brake cylinder ₃ is calculated online (C). Hereby, the reaction force and the wheel pressure or the vehicle deceleration at the brake pedal 2 are associated with one another as in a normal vehicle equipped with a vacuum brake booster, and the changed stiffness of the volume storage and brake system 1 is desired It is guaranteed that only the pedal stroke change occurs at the time of deceleration.

  In a preferred manner, the method is used during driving of a motor vehicle. Average long-term values can be stored, and in some cases, long-term values can be used as default values, for example, if online adaptation is not available. Situations in which evaluation is not possible are, for example, emergency braking or braking with high operating dynamics, which result in erroneous calculations due to time delays and dynamic pressures. Even at extremely low temperatures, for example T <−30 ° C., on the basis of the properties of the hydraulic medium used, the amplified dynamic pressure effect and the reduced pumping capacity of the pressure generator 12 have to be taken into account, Preferably stored long-term values are used.

  Here the method is such that the pressure of the master brake cylinder 3 is controlled to be adapted to the wheel pressure or the pressure deviation of the wheel brake 9, whereas according to another embodiment this is Conversely, the control of the pressure in the wheel brake 9 or of the wheel pressure is adapted to the pressure deviation of the master brake cylinder 3.

1 brake system 2 brake pedal 3 master brake cylinder 4 brake circuit 6 switching valve 8 stiffness factor 9 wheel brake 10, 11 hydraulic pressure sensor, pressure sensor 12 pressure generator 13 control unit 14 pedal stroke sensor Δs stroke travel distance, offset value

Claims (12)

A method for operating a hydraulic brake system (1) of a motor vehicle, said brake system (1) comprising a brake pedal (2) and a master brake cylinder (3) connected to the brake pedal (2). And at least one brake circuit (4) having at least one wheel brake (9), in a method for automatically adjusting the braking force amplification in dependence on the brake pedal operation,
Brake force amplification is produced by at least the controllable pressure generator (12) in the brake circuit (4), on the one hand depending on the brake pedal actuation, and on the other hand in the master brake cylinder (3) or the wheel Method for operating a hydraulic brake system, characterized in that it is generated in dependence on the hydraulic pressure in the brake (9).   Method according to claim 1, characterized in that the brake pedal actuation is detected by means of a pedal stroke sensor (14).   Method according to claim 1 or 2, characterized in that the target pressure of the master brake cylinder (3) is determined as a function of the detected brake pedal actuation.   Method according to one of the claims 1 to 3, characterized in that a target pressure for the wheel brake (9) is determined in dependence of the brake pedal operation.   5. A pressure control device as claimed in any one of the preceding claims, characterized in that the pressure generator (12) is controlled in dependence of the pedal operation on the basis of the assumed volume accommodation of the wheel brake (9). Method according to paragraph.   6. A pressure control system as claimed in any one of the preceding claims, characterized in that the pressure generator (12) is controlled in dependence on the target pressure characteristic curve for the master brake cylinder (3) or the wheel brake (9). Or the method described in paragraph 1.   A method according to claim 1, characterized in that the target pressure characteristic curve is displaced by an offset value (Δs) depending on the idle stroke, in particular the air gap and / or the prefilling of the brake circuit (4). The method according to any one of the above.   A stiffness factor (8) of the brake circuit (4) is calculated as a function of the offset value (Δs) and is used for the desired pressure characteristic curve. Method according to clause 1. A hydraulic brake system (1) for a motor vehicle, comprising a brake pedal (2), a master brake cylinder (3) connected to the brake pedal (2), and at least one wheel brake (9) And at least one brake circuit (4), the brake circuit (4) being of the type in which at least one brake booster is correspondingly arranged,
The brake booster comprises a controllable pressure generator controlled by a specially configured control unit (13), said control unit (13) claiming said pressure generator (12) Item 9. A hydraulic brake system, which is configured to be controlled according to the method according to any one of Items 1 to 8.   10. A braking system according to claim 9, characterized in that the master brake cylinder (3) and / or the wheel brake (9) each have at least one hydraulic pressure sensor (10, 11).   A brake system according to claim 9 or 10, characterized in that a pedal stroke sensor (14) is associated with the brake pedal (2).   The brake circuit (4) is characterized in that it comprises at least one operable switching valve (6) between the master brake cylinder (3) and the wheel brake (9). The brake system according to any one of 9 to 11.

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