WO2010069656A1 - Method for controlling a brake booster of a hydraulic auxiliary power-operated vehicle brake system - Google Patents

Abstract

The invention relates to a method for controlling or adjusting an electromechanical brake booster (1) of a hydraulic vehicle brake system. According to the invention, an auxiliary power of the brake booster (1) is controlled not exclusively depending on an actuation path or a muscular power, but also or instead depending on one or more other variables such as the actuation or release of the brake, a relative movement between a brake pedal and the brake booster and/or an actuation speed and/or depending on a driving state such as speed, cornering and/or forward travel or reversing. The invention particularly provides a hysteresis of the pedal characteristic, i.e. a muscular power different for a brake actuation than for releasing the brake.

Description

 description

title

Method for controlling a brake booster of a hydraulic auxiliary vehicle brake system

State of the art

The invention relates to a method for controlling a brake booster of a hydraulic power-assisted vehicle brake system having the features of the term of claim 1. The terms control, etc. are also used in the sense of control, rules, etc. here.

In motor vehicles today hydraulic vehicle brake systems with a muscle-operated master cylinder and a vacuum brake booster are common. The muscle power is applied by foot by means of a (foot -) / brake pedal or by hand by means of a (hand) brake lever. The brake booster exerts an auxiliary force in addition to the muscle power on the master cylinder, with actually a piston, namely a so-called rod or primary piston is acted upon and moved by the force and not the

Master brake cylinder itself. The force exerted by a driver muscle power and the auxiliary power of the brake booster add up to an actuating force with which the master cylinder or its piston is acted upon. For the sake of simplicity, an actuation or loading of the master cylinder will be discussed below. Because part of the on the

Applied master brake cylinder actuating force applied as muscle power by the driver and the remaining part is the auxiliary power generated by the brake booster, such vehicle braking systems are referred to as auxiliary vehicle brake systems. The auxiliary power of a vacuum brake power booster or the power gain, ie the ratio of operating force to muscle power, in a vacuum brake booster from a Ser- controlled voventil, which ventilates the so-called working chamber of the brake booster. The servo valve is controlled by a relative movement between a piston rod which is pivotally connected to the brake pedal, and a working piston of the brake booster, so in the end by a pedal travel and / or a pedal force. The pedal travel is the path traveled by the brake pedal or the piston rod and will be referred to hereinafter as the actuation path. The pedal force is the force exerted on the brake pedal or the piston rod muscle power. The control of the auxiliary power of the brake booster or the power amplification thus takes place in dependence on the actuation path and / or the force exerted by the driver muscle power.

There are also known electromechanical brake booster. These can also be understood as electromechanical actuators which electromechanically generate the power to operate the master cylinder in addition to the muscle force exerted by the driver. Exemplary is on the

Publication DE 100 57 557 A1 referenced, which discloses an electromechanical brake booster with a linear motor or an electromagnet. Also possible is the generation of the auxiliary power with an electric motor via a transmission. The control of the auxiliary power of the known electromechanical brake booster see in response to a pedal travel, which is referred to here as the actuation path, and / or in response to a pedal force, which is referred to here as muscle power. For measuring the pedal or actuating travel and / or the muscle power, the known electromechanical brake booster on a Weg- and a force sensor. To differentiate here is between the actuation path, namely the pedal travel or the way of the piston rod, on the one hand and the actuating force on the other hand, which is the sum of the force exerted by the driver for braking effort muscle power and the auxiliary power generated by the brake booster, the common to the master cylinder or whose piston act. The actuation path, ie the path of the brake pedal or the articulated connection with it

Piston rod does not have to be equal to the piston stroke, so the displacement of the piston of the master cylinder, because the piston rod can move relative to the piston. Disclosure of the invention

The inventive method with the features of claim 1 provides a control of the auxiliary power of the brake booster or its Verdikkungsfaktors in response to a size that is neither the actuation path, for example, the brake pedal or the piston rod nor the muscle power. The invention allows a hysteresis-free brake operation or the choice of a hysteresis, wherein the hysteresis can be variable. Hysteresis means that the assisting power of the brake booster differs at a certain brake pedal position, depending on whether the brake is actuated or released.

The hysteresis of the vehicle brake system can be controlled by software and thereby changed with little effort and adapted for example to different vehicles. Also, the hysteresis can be easily in

Depending on the type of brake operation, for example, be controlled by the speed of the brake application and / or driving conditions of a vehicle.

Sizes of which the control of the auxiliary power of the brake booster can be dependent are, for example, an actuation direction, ie actuation or release of the vehicle brake system, the time since a reversal of the actuation direction, a relative movement between a brake pedal or a piston rod and a movement generated by the brake booster and / or, as already mentioned, an operating speed (claim 3).

The assist power of the brake booster may also be controlled to compensate for vehicle brake hysteresis (e.g., by friction of mechanical components)

Instead of or in addition to the above-mentioned variables which act on the vehicle brake system during the braking operation, the control of the brake booster can also be controlled as a function of a driving state of a vehicle which is equipped with the vehicle brake system (claim 5). Such driving conditions may be a vehicle speed, cornering and / or forward and reverse. The auxiliary power of the brake Amplifier and thus its amplification factor and / or the hysteresis can be dependent on the method according to the invention of fast and slow driving, driving at walking speed (shunting / parking) and cornering speed, which can be determined, for example, by a rotary accelerometer which can be used for driving dynamics regulations (FDR, ESP;

Anti-skid control) is used.

Instead of or in addition to the above-mentioned quantities of a brake operation or a driving state of a vehicle, the control of the brake booster can also be performed depending on settings of a driver, e.g. Adjustment of transmission and / or chassis characteristics (e.g., comfort or sport emphasis) or depending on adaptation algorithms of the brake system or other vehicle systems that evaluate the driver's driving style (e.g., accelerator pedal gradient).

Preferably, but not necessarily, the auxiliary power of the brake booster is also controlled in dependence on the actuation path and / or the force exerted by a driver for the braking force of the muscle force, as is known per se. This is the subject of claim 6.

The controllability of the brake booster according to the invention is not possible with a conventional vacuum brake booster which has a servo valve controlled by the pedal rod. It is instead of the servo valve or preferably in addition a controllable valve, such as a solenoid valve and because of better controllability in particular a proportional valve necessary. Claim 7 provides an electromechanical brake booster, which has the required controllability by design.

Short description of the drawing

The invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it:

1 shows an axial section of an electromechanical Bremskraftver- amplifier for carrying out the method according to the invention; FIG. 2 shows a flow chart of an embodiment of the method according to the invention; and

Figure 3 is a pedal characteristic according to the inventive method.

The drawing is to be understood as a schematic and simplified representation for understanding and explaining the invention.

Embodiment of the invention

The brake booster 1 shown in FIG. 1 is an electromechanical brake booster 1 with an electromechanical actuator 2 to be explained, and a piston rod 3, which is connected in an articulated manner to a brake pedal 5. Furthermore, the brake booster 1, a push rod 7 with a piston-shaped base 6, with the in a conventional manner an unillustrated primary or rod piston of a hydraulic master cylinder, also not shown a hydraulic vehicle brake system with an actuating force can be acted upon.

The actuator 2 has an amplifier body 9, which is cylindrical in the illustrated embodiment and has an axial through hole 10 in which the piston rod 3 is received axially displaceable. The through hole 10 of the amplifier body 9 opens into a cylindrical countersink 1 1, which has a larger diameter than the through hole 10 and in which the foot 6 of the push rod 7 is received axially displaceable. The amplifier body 9 is axially displaceable as the piston rod 3 and the push rod 7, which is symbolically represented in the drawing by a rolling bearing on the underside of the booster body 9.

Between the foot 6 of the push rod 7 and a bottom 12 of the countersink 1 1, an elastic reaction disc 8 is arranged. The reaction disc 8 is acted upon in its center by the piston rod 3 with a force exerted by a driver on the brake pedal muscle force and annularly around the piston rod 3 from the base 12 of the countersink 1 1 of the booster body 9 with an electromechanically generated by the actuator 2 auxiliary power. The reaction disk 8 sums up the muscle power and the auxiliary power to a actuating force and transmits it to the foot 6 of the push rod 7, which in turn acts as already said the primary or rod piston of the master cylinder, not shown. Due to its elasticity, the reaction disc 8 compensates for relative displacements between the piston rod 3 and the enhancer body 9 to a limited extent. When the reaction disk 8 is acted upon by the booster body 9, the reaction disk 8 bulges in its center as indicated in FIG. 1 by dashed lines into the through hole 10 of the booster body 9 until it rests against the end face of the piston rod 3 facing it. In this case, the reaction disc 8 includes a here as Lehrweg d designated gap between itself and the piston rod 3, so that the muscle power is transmitted from the piston rod 3 on the foot 6 of the push rod 7. The countersink 1 1 of the amplifier body 9 comprises the reaction disk 8 as a socket and thereby prevents a radial expansion of the reaction disk 8 or at least limits the radial expansion of the reaction disk 8.

For the drive, the actuator 2 has an electric motor 14 with which the amplifier body 9 can be driven in the axial direction via a gear 15. The gear 15 meshes with a rack 16 of the booster body 9. The gear 15 and the electric motor 14 may be interposed an unillustrated reduction gear. Instead of an electromotive drive, the electromechanical actuator 2 may, for example, also have an electromagnetic drive or a linear motor (not shown).

The electromechanical brake booster 1 has a displacement sensor 17, with which a displacement and thus also a speed and an acceleration of the booster body 9, and a position sensor 18, with a relative movement, ie a displacement of the piston rod 3 with respect to the booster body 9, are measurable on , Furthermore, there may be a displacement sensor 19 for measuring the displacement of the piston rod 3, ie for

Measurement of the pedal travel of the brake pedal 5, and a force sensor 20 for measuring the force exerted on the brake pedal 5 muscle power. The displacement of the piston rod 3 and the pedal travel of the brake pedal 5 are also referred to as actuating travel here. An electronic control unit 21 receives the signals from the sensors 17, 18, 19, 20 and controls the electric motor 14 and thus the displacement of the booster body 9 and the actuator 2 of the Bremskraftver- Strength 1 generated and transmitted via the reaction disc 8 on the foot 6 of the push rod 7 auxiliary power. Instead of the displacement sensor 19 for the pedal travel, a rotation angle sensor may also be provided on the electric motor 14 (not shown). Certain engine types, such as electronically commutated electric motors, provide a rotation angle signal, so no special sensor is required.

As usual, the brake pedal 5 is stepped on to a brake application. With the position sensor 18, a displacement of the piston rod 3 relative to the booster body 9 is measured and the electric motor 14 energized so that the booster body 9 moves in the same direction as the piston rod 3, ie in the direction of a brake actuator in the direction of the push rod 7. For example, the displacement between the piston rod 3 and the booster body 9 is controlled to zero during a brake application, i. the booster body 9 moves synchronously with the piston rod 3 with. Due to the gap d between the piston rod 3 and the reaction disc 8, the brake pedal 5 moves with the piston rod 3 initially almost free of force, the force exerted on the push rod 7 actuating force is exclusively the auxiliary power of the actuator 2 and the brake booster. 1 Due to the load, the reaction disk 8, as already described, elastically deforms in its center into the through hole 10 of the amplifier body 9 until it rests against the end face of the piston rod 3 facing it. From the system of the reaction disc 8 on the piston rod 3 or vice versa, the piston rod 3 on the reaction disc 8, the reaction disc 8 transmits the muscle power of the piston rod 3 additional lent to the auxiliary power of the booster body 9 of the actuator 2 on the push rod.

The muscular force is felt on the brake pedal 5 and must be applied to the brake pedal 5. Size for the control or regulation in the case described, the displacement of the piston rod 3 relative to the booster body 9. However, it is additionally or instead also a control of the actuator 2 and thus of the brake booster 1 in dependence on other variables such as the brake pedal fifth exerted muscle power or the pedal travel (actuation path) possible.

According to one embodiment of the method according to the invention, in a first step, the direction of movement of the piston rod 3 and the brake pedal 5 is detected. It is therefore determined whether the brake is actuated or released becomes. In the flowchart of Figure 2, the direction of movement is queried by the query Vp _ed ≥O, where V _{Ped is} the pedal speed. If the pedal speed Vp _ed > 0, ie the brake is actuated, the displacement of the piston rod 3 with respect to the verifier body 9 is queried in a next method step. If the displacement x> 0, ie the piston rod 3 is further displaced than the booster body 9, the auxiliary force F _{BoOst of} the actuator 2 and thus of the brake booster 1 is increased in order to reduce the displacement of the piston rod 3 with respect to the booster body 9. Subsequently, the query begins, ie the method according to the invention again, the method is constantly re-performed. The index "Boost" of the assistant stands for

If, in the second method step, the displacement of the piston rod 3 is not greater than that of the amplifier body 9, the auxiliary force _{F.sub.soost is} not increased.When the first inquiry is made, the pedal speed V.sub.p _{ed is} negative, ie In a second query, it is checked whether the displacement x of the piston rod 3 with respect to the amplifier body 9 is smaller than a hysteresis value c, the hysteresis value c being selectable and changeable in embodiments of the method according to the invention hysteresis means that the displacement of the piston rod 3 with respect to the booster body 9 is different when the brake is actuated than when the brake is released 9 is assumed to be zero when the brake is actuated When the brake is released, the piston rod 3 shifts with respect to the booster body 9, it leads by the hysteresis value c. The hysteresis value c is negative because the piston rod 3 leads in the sense of a release of the brake with respect to the amplifier 9, ie counter to the actuation direction which, in any case, here is provided with a positive sign. Thus, if the displacement x of the piston rod 3 with respect to the booster body 9 is greater than the hysteresis value c in the second method step when the brake is released, the auxiliary force F _{BoOst of} the actuator 2 and thus of the brake booster 1 is reduced so that the wake of the booster body 9 is opposite the piston rod 3 when releasing the brake is not greater than the hysteresis c. In the other case, the auxiliary power F _Bθost remains unchanged.

The hysteresis value c can also be selected positive, resulting in a flow of the piston rod 3 relative to the booster body 9, so a shift the piston rod 3 in the direction of actuation on the reaction disc 8 and the foot 6 of the push rod 7 relative to the booster body 9 upon actuation of the brake results.

Apart from the direction of movement of the piston rod 3 and the brake pedal 5, the hysteresis c may be dependent on other parameters of the brake operation such as the operating speed and the muscle force exerted on the brake pedal 5 and / or the displacement of the piston rod 3, ie the pedal travel 5. The hysteresis value c can be dependent on one, several or all of the mentioned variables and possibly other variables. In addition, the hysteresis value c may be dependent on variables which are not directly related to the brake operation, in particular of driving conditions of a vehicle equipped with the vehicle brake system. Such variables are, for example, the driving speed, cornering and / or forward or reverse drive. With the method _{according to} the invention, the auxiliary power F _{Bθost of} the brake booster 1 and thus the force amplification and a pedal characteristic in dependence on different sizes, which are related to the brake operation and / or the driving conditions, control or regulate. The size of the shift, so the size of the hysteresis, can change with the pedal travel. Also, a change in the hysteresis value c at a

Brake operation and when releasing the brake possible, for example, a positive hysteresis c in the brake application and a negative hysteresis c when releasing the brake.

Figure 3 shows a pedal characteristic in controlling the brake booster 1 according to the inventive method. The pedal characteristic is the dependence between the force exerted on the brake pedal 5 muscle force, which is also commonly referred to as pedal force, and the pedal travel and the displacement of the piston rod 3. The muscle force is plotted on the ordinate in Figure 3 and designated Fp _ed , the Pedalweg is abraded on the abscissa and denoted by s. It can be seen that the pedal characteristic in the operation of the brake has a different course than when releasing the brake, upon actuation of the brake is exerted on the brake pedal 5 muscle force F _Ped at a certain pedal position greater than when releasing the brake. If the brake is only partially released and pressed again, the pedal characteristic returns from its course when releasing the brake on the course when pressing the brake. As explained the course of the pedal characteristic and the hysteresis can change depending on different sizes, with a change can also take place during braking.

Claims

claims 1 . Method for controlling a brake booster (1) of a hydraulic auxiliary vehicle brake system, which has a muscle-operated master cylinder and a controllable brake booster (1) which exerts an auxiliary force to the master cylinder in addition to muscle power during a brake application, characterized in that the auxiliary power of Brake booster (1) is controlled in response to a size that is neither a Betätigungsweg nor the muscle power. 2. The method according to claim 1, characterized in that the brake booster (1) is controlled so that a pedal characteristic has a hysteresis. 3. The method according to claim 1, characterized in that the size for the control of the brake booster (1) is an actuating direction, the time since a reversal of the actuating direction, a relative movement between the muscle power and the brake booster (1) and / or an operating speed. 4. The method according to claim 1, characterized in that the brake booster (1) is controlled so that hysteresis of the Fahrzeugbrems- be aläge compensated 5. The method according to claim 1, characterized in that the size for the control of the brake booster (1) is a driving condition of a vehicle which is equipped with the vehicle brake system. 6. The method according to claim 1, characterized in that the auxiliary power of the brake booster (1) is controlled as a function of the size and in dependence on the actuation travel and / or the muscular force. 7. The method according to claim 1, characterized in that the vehicle brake system comprises an electromechanical brake booster (1).