EP2571736A1

EP2571736A1 - Brake force booster and method for operating the same

Info

Publication number: EP2571736A1
Application number: EP11711836A
Authority: EP
Inventors: Dirk Mahnkopf
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-05-20
Filing date: 2011-03-25
Publication date: 2013-03-27
Also published as: JP2013526452A; CN102883928A; CN102883928B; JP5653512B2; US20130140877A1; US9604618B2; DE102010038918A1; WO2011144378A1

Abstract

The invention relates to a regulable brake force booster and to a method and a control unit for operating the same. By means of the method for operating the brake force booster and the design of the brake force booster, feedback to the driver in the form of an offset of the brake pedal or in the form of a changed actuating force in the event of a change in the assistance force can be eliminated or reduced. In particular, the change in the assistance force is an adaptation of the braking action of a hydraulic brake system to the braking action of a regenerative brake system.

Description

description

Brake booster and method for its operation

State of the art

The method according to the invention can be used in a brake system which comprises two partial brake systems. One of them is a partial hydraulic brake system, which also includes the brake booster 2, and the other partial brake system is a regenerative partial brake system. The braking effect of both partial braking systems lead to a total braking effect of the brake system. If the proportion of the braking effect of the regenerative braking system changes as a function of the overall braking effect, then the hydraulic braking effect must be adapted to this change, this change being best compensated for.

An adaptation of the hydraulic braking action of the hydraulic partial braking system should in the best case unnoticed by the driver, in particular without a reaction for the driver due to a variable pedal feel, offset the brake pedal or change a force applied for the operation. For this reason, a complete decoupling of the actuating unit, so for example, the brake pedal, provided by the hydraulic brake system in such total braking systems often; the driver only operates a pedal simulator. A force transfer from the driver to the wheel brakes is often not provided in such systems or is interrupted by, for example, a valve is closed, which connects the master cylinder with a hydraulic brake. However, this can affect the safety of the brake system, especially in case of failure of braking power generating means. In document DE 10 2009 007 494 AI a brake system is described, in which - as mentioned - the driver is disconnected from the brake circuit in the case of a regenerative braking.

Disclosure of the invention

The method according to the invention makes it possible to adapt the braking effect by adequately operating a controllable brake booster, so that the driver feels no or only little reaction, whereby the driver is not decoupled from the brake system. In the brake system according to the invention, the driver always remains connected to the at least one brake circuit connected to the master brake cylinder. Connected means in this sense that the possibility of a force transfer remains, regardless of whether the driver brakes conventional and / or regenerative braking.

The present invention relates to a controllable brake booster and a method for operating the same.

In the method according to the invention for operating the controllable brake booster, it is provided that the brake booster is part of a hydraulic brake system. The brake booster applies an assisting force to an output element of the brake booster. The support force to be applied is determined as a function of at least one information relating to at least one elastic element which is located between an input element of the brake booster and the output element and in dependence on at least one information relating to a pressure-volume relationship of the hydraulic brake system, in particular a pV- Curve. In addition, the assisting force to be applied is also determined depending on a driver applied input force applied to the input member. The applied support force is applied by the brake booster in the process of the invention. The relationship between the force applied by the driver input force, for example via a brake pedal, and the force applied by the amplifier support force is also referred to as a characteristic of the brake booster. In a controllable brake booster, this relationship can be varied. Characterized in that the support force can be adjusted or adjusted independently of the input power, this characteristic can be changed in a controllable brake booster.

In certain brake situations or operating situations of a brake system, it may be necessary to reduce the force applied by the brake booster support force or increase. This can be done by means of the controllable brake booster.

It is provided that the relationship between the input force and the applied assisting force is determined by the brake booster taking advantage of at least one piece of information relating to at least one elastic element. The deformation of the elastic element depends both on the input force and on the support force.

The elastic member transmits the input and assisting force to the output rod. The input rod of the brake booster is coupled to a brake pedal, the output rod of the brake booster can act directly or indirectly on an input piston of a master cylinder. By such an elastic element, for example, a spring or an elastic member can be understood, as it is used in brake boosters as a reaction disk.

If information relating to the elastic element is taken into account in determining the support force of the brake booster to be applied, then a reaction on the part of the brake system can be reduced, in particular the change in the force acting against the driver for a given pedal position. In this way, the driver feels less reaction from the brake system and so does not realize the change in the characteristics of the brake booster or only to a small extent. Likewise, it is provided that the applied assistance force of the brake booster is determined by utilizing at least one piece of information regarding a pressure-volume relationship of the hydraulic brake system. Such a pressure-volume relationship is, for example, a pV characteristic.

By information regarding the elastic element on the part of the brake booster and by taking into account information regarding the pressure-volume relationship of the connected hydraulic elements, the characteristic of the brake booster can be changed or varied in an advantageous manner. Thus, essential components of the brake system, the brake booster and the hydraulic elements, which are present in the brake system, are taken into account for setting the characteristic.

Furthermore, it is provided in the method according to the invention that the assistance force is adjusted such that an infinitesimal small change in the assisting force leads to a vanishing displacement of the input element of the brake booster, in particular to a zero shift. It can be assumed that the operation is kept constant by the driver. A constant actuation by the driver is to be understood, for example, as a constant input force and / or a constant input path.

Changing the assist force for a given operator brake application, ie changing the brake booster characteristic, can be perceived by the driver, especially if the characteristic is changed during braking. For example, changing the characteristic will cause the driver's applied force to reach the present pedal position to change. This is usually perceived as a change in the opposing force. If, on the other hand, the driver memorizes a constant input force, changing the characteristic results in a shift of the input rod and thus the pedal position. An offset of the input element at a constant input force or an amended, applied by the driver input force at a constant position of the pedal or the Input force can be summarized under the term "feedback" for the driver.

In the method according to the invention, the assisting force is set such that such a retroactive effect on the driver e.g. is minimized at a present change of the assisting force and constant input force, e.g. a driver experiences a vanishingly small displacement of the input element, in particular no displacement of the input element. An adaptation of the characteristic of the brake booster to a present braking situation can thus take place with reduced retroactivity to the driver, especially without any reaction.

A present braking situation may, for example, be a change of a regenerative braking torque which participates in braking in addition to a hydraulic braking torque. In a further embodiment of the method according to the invention it is provided that the support force is adjusted such that at a finite change in the supporting force, an additional force to the input force, which must be applied to hold the input member at the same position is minimal, in particular equal to zero.

If the assisting force changes in a present braking situation or an operating condition of the entire braking system, ie not by an infinitesimal proportion as before, but by a finite proportion, an additional force is required to keep the input element in the same position. By adjusting the assist force, it is ensured that the change of the force to be applied by the driver, which is necessary to the

Input element at the finite change in the support force at the same position to keep as low as possible. Thus, an irritating to the driver feedback of the change in the supporting force can be advantageously avoided.

In a further embodiment of the method according to the invention it is provided that the additional force to be applied is applied by an actuator. In this way, the driver does not have to vary the input force, but the actuator. The actuator may additionally be provided as an actuator in a brake booster. In a further embodiment of the method according to the invention can be provided that the applied additional force is applied by a reaction force, especially a Haftreibkraft. Also in this way it is ensured that the minimum change in the input force, which is necessary to keep the input member at a fixed position when the assistance force of the brake booster is changed, is not applied by the driver. In this way, the driver experiences advantageously no negative reaction from the braking system.

In a further embodiment of the method according to the invention it is provided that the minimum change in the input force is applied by a frictional force, wherein the frictional force is regulated. The controlled frictional force is in particular a Gleitreibkraft which is mechanically and / or electrically regulated, in particular by a brake.

In a further embodiment of the method according to the invention it is provided that the brake is a friction brake, which acts directly or indirectly on the input member. For example, it may be provided that the brake presses the input element against a further surface for generating the frictional force. In this way, in an advantageous manner, the frictional force can be adjusted by skillful selection of the surface according to the invention, to which the input element is pressed, for example with respect to the magnitude of the frictional force.

In a further embodiment of the method according to the invention, it is provided that the brake booster is part of a hydraulic partial brake system of an overall brake system. By changing the assisting force of the brake booster, a hydraulic braking torque is set in the method according to the invention. By means of the hydraulic braking torque, a braking torque difference between a total braking torque and a regenerative braking torque is reduced. In particular, it is provided to compensate for this braking torque difference. The regenerative braking torque is generated, for example, by a generator which charges a power source. produced. Such regenerative braking systems are used, for example, in electric or hybrid vehicles.

The regenerative braking torque is produced by a further partial braking system of the overall brake system. If the hydraulic braking torque as described is adapted to the present regenerative braking torque by changing the assisting force, then the overall braking effect can advantageously be kept constant given the driver's actuation. In this way, the overall braking effect of the vehicle is independent of the present operating situation, in particular of the regenerative braking system, whose braking effect is greatly different from the present one

Vehicle speed and, for example, the level of the energy storage, which is loaded by means of the regenerative braking system depends. By operating the brake booster according to the inventive relationship between the input force and the supporting force can in this way the braking effect of

Vehicle are kept constant taking into account the braking effect of the regenerative system, which is variable, with a negative reaction to the driver by operating the brake booster according to the context of the invention is prevented.

In a further embodiment of the method according to the invention it is provided that the applied support force is stored as a function of the input force as a characteristic in the vehicle. The stored characteristic here depends on the at least one information regarding the at least one elastic element and on the at least one information relating to a pressure element.

Volume relationship of the hydraulic brake system. The characteristic does not necessarily depend on the input power. Since the input force, which is based on the support force to be set, can also be determined from a signal of a displacement sensor which measures the input path of an actuating element, it can also be provided that the characteristic curve links the assisting force with the input path, instead of the input force.

In a further embodiment of the method according to the invention, it is provided that the characteristic is recalibrated, in particular during maintenance intervals in a workshop or as part of a check before or at the start of the Vehicle. If the relationship exists as a characteristic curve in the vehicle, then this can be recalibrated and it is always in an advantageous manner the current context, which takes into account the state of the brake system, for example, age-related deviations of the state of the brake system.

It can also be provided to calculate the support force to be set as a function of the input force during braking. Also in the calculation, the support force to be set depends on the at least one information regarding the at least one elastic element (9) and on the at least one information regarding a pressure-volume relationship of the hydraulic brake system.

A provision of a characteristic curve in the vehicle, in particular in a control unit of the vehicle, is then not necessary. If the assistance force is always calculated during a braking operation, ie during operation of the vehicle, then the set assisting force is always based on the values currently present in the vehicle. A recalibration can thus be omitted in an advantageous manner. Either the at least one information regarding the pressure-volume relationship or the at least one information relating to the elastic element or both must be determined from measured variables, are known and stored in the vehicle in electronic form. Both information can be stored in the control unit.

It can be provided to determine the input force by means of a force sensor or to calculate it by means of at least one signal of a displacement sensor of the input element.

Furthermore, the invention comprises a controllable brake booster which applies its support force to an output element of the brake booster, wherein the applied support force of at least one information regarding at least one elastic element, which is located between an input element of the brake booster and the output element, at least one information a pressure-volume relationship of the hydraulic braking system, in particular a pV characteristic, as well as by an applied by the driver input force which is applied to the input member depends. The relationship between the input force and the supporting force can be determined on the basis of the two aforementioned information in such a way that a reaction to the driver is minimized when the assisting force changes. The brake booster brings the support force on. Thus, an operation of the brake booster is advantageously possible, in which the brake booster provides a support force available that can be changed without the driver experiences a reaction. An irritating reaction for the driver, for example by offset of the brake pedal with a constant input force, can thus be avoided. The possibility of assisting the present needs of the

Brake system, in particular to adjust the braking situation, remains intact.

In a further embodiment of the brake booster is provided that the brake booster, the support force and an additional force, which force must be applied to a finite change in the support force on the input element to minimize the reaction to minimize / completely suppress, and counteracts an offset of the input element, in particular, keeps the input member at the same position. It is particularly advantageous that not only the support force set by the brake booster, but also the additional power can be applied. In a further embodiment of the brake booster is provided that the brake booster has an additional actuator. By means of this additional actuator, the additional power can be applied and changed. The fact that an additional actuator is provided in the brake booster, the support force can be changed so that the reaction to the driver is minimized with a variation of the support force or completely suppressed. Thus, the characteristic of the brake booster can be adjusted unnoticed by the driver. The fact that the actuator is part of the brake booster, the hydraulic brake system can be designed to save space, since no additional component must be integrated in the vehicle.

In a further embodiment of the brake booster is provided that the brake booster mechanical and / or electromechanical Has brake. The brake is mechanically and / or electromechanically actuated. The brake acts on the input element of the brake booster. By pressing the brake, electromechanical or mechanical, a change of additional power is possible. By a mechanically actuated brake, the additional force can be varied depending on the actuation position of the input element and / or position of the amplifier body. The mechanically actuated brake can take place, for example, in the form of a mechanical coupling, in particular an elastic mechanical coupling between the amplifier body and the brake pedal or the input element. An electromechanically actuated brake comprises a further actuator. The change of the input force takes place by friction. It is both static friction, and sliding friction conceivable. An electromechanically operable brake has the advantage that the amount by which the input force is changed, can be finely controlled and adjusted.

In addition to the method for operating the brake booster and the brake booster itself part of the invention is a control unit for performing the method and for operating the brake booster itself. By means of the control unit, the brake booster can be controlled. Taxes can also be understood in the sense of a regulation in this context. By means of the control unit, the support force to be set can firstly be determined on the basis of characteristic curves or also calculated directly, with and without the use of characteristic curves. Furthermore, the setting of the support force and optionally the additional force of the brake booster is controlled by the control unit. In particular, it can be provided that the control unit controls the further actuator of the brake booster for actuating the brake. In addition, the additional actuator, which applies an additional force to the input element, can be actuated by means of the control device.

Figure 1 shows schematically the controllable brake booster according to the invention. Figure 2 shows a replacement model of the brake booster, which represents the interaction of the brake booster and driver during braking or resulting forces.

In Figure 3 a and b is shown on the basis of the replacement model, which effects can have a regenerative braking operation on the brake booster and the driver.

FIG. 4 shows a profile of a characteristic of the brake booster and, by way of example, an optimized characteristic according to the method according to the invention.

Figure 5 and Figure 6 show the replacement model, as an additional force can be applied to the actuator of the brake system. On the one hand, FIG. 5 shows an additional force via static friction, on the other hand FIG. 6 shows an additional force applied via friction of a brake.

FIG. 7 shows a further possibility of applying an additional force to the actuating element.

The invention relates to a brake booster 1 as shown schematically in Figure 1.

The brake booster 1 is to be understood in the following as a controllable and / or controllable brake booster 1 and is hereinafter referred to only as a brake booster 1. In particular, controllable includes that the assisting force 2 of the brake booster for actuating a master brake cylinder (not shown) can be varied. Thus, depending on the driver, the brake booster 1 can apply an assisting force F _sup 2, for example as a function of an input force 3, which generally corresponds to the actuating force F _in FIG. 3 of the driver. The input force 3 may optionally include a further, additional force in addition to the driver's operating force, which will be explained later in the description of the method.

The input force 3 acts on the input element 4. Likewise, the brake booster, the supporting force F _sup 2 in response to a Actuation / an operating position of the input element 4 apply.

Likewise, the brake booster 1 can provide a support force 2 also independent of an operation of a brake pedal by the driver, in particular independent of an operating force of the driver and / or an actuating travel of the brake pedal.

Input force 3 and 2 supportive force act together on an output element 5. The output element can then for example act on an input piston of a master cylinder with an output force 6 and thus initiate a braking of the vehicle. The

Support force 2 of the brake booster is applied by an actuator 7, for example a motor. Optionally, this can be done via a transmission, such as a rotation-translation gear. The support force then acts, if necessary via the transmission, on an amplifier body 8. Input force 3 and 2 supporting force are on the

Output element 5 transmitted via a coupling element 9, which combines the forces to the output force 6. In this case, the coupling element can be designed differently. It is essential to the invention that the deformation of the coupling element can depend on both the input and the assisting force, e.g. in the form of a force scale indicating a deviation of the ratio of the assisting force 2 to the input force 3 from a predetermined ratio by a deformation. Such a force balance is, for example, a reaction disk, as it is often found in brake boosters and is assumed below without limiting the generality. The reaction disk 9 may be directly connected to the output element 5, or indirectly via other components. Input element 4 and amplifier body 8 need not be in direct connection to the reaction disk. The brake booster can have an idle path between the input element and the reaction disk 9, which first has to be overcome before the input element 4 comes into contact with the reaction disk 9.

FIG. 2 shows, with reference to a replacement model, the variables necessary for operating the brake booster. Identical elements are provided in Figure 2 with the same reference numerals as in Figure 1. The actuator of the Brake booster 1 (not shown in FIG. 2) can apply an assisting force 2 to the booster body 8, resulting in a displacement s _sup 201 of the booster body. If the driver applies an input force F _in FIG. 3 to the input element 4, then this shifts by a distance s _in 202. Via the coupling element 9, the input force 3 and the assisting force 2 are combined to form an output force F _ou t 6. The output element 5 is displaced by a distance s _ou t 203. The replacement model of the brake booster further includes variables that represent the reaction disk 9. Thus, the reaction disc 9 has an elasticity 204. In addition, three contact points 205, 206 and 207 can be seen in FIG. A quotient x indicates the ratio of the distance x between the points 205 and 207 and the distance between points 206 and 207 (marked here with the length one). The lever lengths, ie the length of the distance of the points 205,207, as well as the points 206,207 correspond to areas on the reaction disk 9. The solid line shows the reaction disk

9 in rest position. If an assisting force 2 and / or an input force 3 is present, this can lead to a deformation of the reaction disk 9, shown as a dashed line 208 in FIG. 2. This deformation of the reaction disk 9 leads to a differential path ds 210 between the new position of the point 206 with applied input and / or support force and the point

207th

As described above, the method according to the invention is used, inter alia, when the proportion of the braking effect of a regenerative partial braking system changes in the overall braking effect.

For the sake of simplicity, it is now assumed that the driver brakes with a constant input force, only with the involvement of the hydraulic partial braking system. In this case, the brake booster can apply an assisting force 2. This initial situation is shown in Figure 3a. Again, the reference numerals of Figures 1 and 2 are maintained if the designated elements in Figure 3 correspond to the elements in Figure 1 and 2 respectively. If the driver brakes with a constant input force, then point 206 is at a position as shown in FIG. 3a. By applying the input and supporting force is a deformation of the reaction disc 9 before. Furthermore, it is now assumed that an additional braking effect is added by the regenerative partial braking system. Since the overall braking effect is to be kept constant, the supporting power is reduced. In the hydraulic partial braking system, this leads to a reduction in the pressure in the wheel brakes and thus to a reduction in the hydraulic braking effect. Additional effects of a master cylinder and a possibly existing hydraulic unit (ESP or ABS, for example) are left out here for simplicity.

Since the pressure in the partial hydraulic brake system has been reduced by reducing the assisting force 2, brake fluid flows back into the master cylinder. This leads to an offset of the output element 5 against the original operating direction. This is shown in FIG. 3b. The dashed line shows the starting situation from FIG. 3a and a parallel offset thereof by the path ds _ou t 301. Furthermore, a further deformation of the reaction disk 9 occurs which results in a deflection at the point of contact of the input rod delta _s 302. This is a position change relative to the position change of the output element. The elasticity of the reaction disk 9 can either have a linear dependence between the force and the deformation path or, more generally, a characteristic curve which describes this relationship. For the linear case, delta _s becomes:

delta _s = 1 / c (F _in -x F _sup ). In the case of a characteristic P (F _in -x F _sup ), delta _s results:

delta _s = P (F _in -x F _sup ).

The offset d input element ds _in caused by changing the assist force 2 follows

s _in = s _out + delta _s .

In order to investigate the offset due to the change in the assist force, the variation of the magnitude s _in can be considered assuming a constant input force. This results in ds. \

\ Fin = const. = ^ 7 ^ ^L AF ₊ ^^ AF

l » ^SU P 3 / ^SU P

^ΟΓ out ° ^r sup ° ^r sup

= ^ EL AF 1 ^DDELTA * F

dF out, ^sup dF sup

Here, sometimes the partial derivatives according to the output force F _ou t and / or the support force F _{sup are} formed and used. The term ^s out iFut ⁼ Fn ⁺ Fu _P ) represents the volume absorption of the brake system, depending on the driver and support forces. This relationship is usually nonlinear.

In order to ensure that the driver notices as little as possible of the change in the assisting force and thus of the offset s _in , the magnitude ds _in must be as small as possible with a constant input force F _in , ideally equal to zero.

It can also be provided that the force change should be minimal in order to keep the size ds _in fixed.

With the condition ds _in = 0, it follows from the above equation: ds _out . ddelta _s . "_

- 2HL FH ^S -AF = 0

dF out, ^sup dF sup

It follows, however, that: If you enter all dependencies into this equation again, you get:

dF sup ^~ dF out _t

The term on the left side depends on the characteristic curve of the reaction disk 9. The term on the right side of the equation again describes the

Volume absorption of the brake system. Both the characteristic curve of the reaction disk and the volume absorption of the brake system are variables which are generally known or otherwise can be determined directly or indirectly. Are these sizes, especially before, in the form of Characteristics, it can be from the specified context (1) for each driver input force F _in an associated support force F _sup specify, in each of the value pairs F _in and F _sup thus found the condition is satisfied that ds _in = 0 applies.

In this way, an optimized amplifier characteristic can be determined, by means of which each input force F can be assigned _in an assist force F _sup. This method works on the assumption that the characteristic curve of the reaction disk 9 and the volume absorption of the brake system are not too far apart, so that the above condition can be solved in a meaningful framework. The amplifier characteristic curve thus determined can now be used in different ways to control the brake booster. On the one hand, the amplifier characteristic can be specified in advance with the specified

Relationship (equation 1) can be calculated. This amplifier characteristic is then used unchanged during braking, possibly including a braking contribution of a regenerative partial braking system. In a further embodiment, the amplifier characteristic is recalibrated. These

Recalibration can be done for a given occasion, or periodically, for example every time the vehicle is restarted or during maintenance. In this way, it is possible to take into account wear in the brake system, for example on brake linings or aging effects in the brake system when determining the amplifier characteristic curve. Thus, there is always an amplifier characteristic which is adapted to the current vehicle condition. Likewise, it is conceivable to directly or indirectly include ambient conditions such as an outside temperature during the determination of the characteristic curve during the recalibration.

On the other hand, it is conceivable that the assisting force F _sup 2 during braking by means of a regulation according to equation 1 at any time during a braking in which there is no contribution of a braking effect of a regenerative braking system, adjust. For this purpose, via a sensor provided in the brake booster and / or via control / control variables the brake booster, the assistance force and the driver force are calculated. For example, parameters such as signals of a displacement sensor of the input rod 4, a position sensor of the booster body 8, an engine position sensor of the engine 7 and a pre-pressure sensor of the hydraulic brake system can be used for this calculation. Likewise, the input force F _in can be measured directly by means of a force sensor. It is also possible to determine the deformation of the reaction disk 9. Said sensor is not shown in the figures.

dP (F _in -xF _see below)

Thus, during operation of the brake, the quantities - dF and --- - can be calculated during braking.

dF _0Ut

Taking advantage of these calculated quantities, Equation (1) can now be used to control the brake booster, that is to say to set the assistance force. In the above options, the brake booster based on a

Characteristic, ie calculated in advance, or to operate in a scheme with direct calculation of the support force to be set, then it is still the support force according to the relationship in equation (1) set.

This can in turn be based on signals from a displacement sensor of

Input rod 4, a position sensor of the amplifier body 8, a motor position sensor of the motor 7 and / or a Differenzwegsensors done. Said sensor is not shown in the figures. Irrespective of whether the brake booster is operated on the basis of a characteristic curve, that is to say pre-calculated, or in a control with direct calculation of the assisting force to be set, the input force F _in from which the determination of the assisting force F _sup to be set can either be measured directly, or be calculated from other sizes, for example, signals from a displacement sensor of the input rod. 4

The characteristic curve F _in _{-F sup} therefore does not necessarily have to be in this form either; likewise, a characteristic s _in _{-F sup can be} provided or the calculation of the assisting force can be carried out starting from an input path s _in . The assisting force is now adjusted so as not to set, as originally, a zero-path of difference between the amplifier body 8 and the input rod 4, but such that Equation 1 is satisfied. This can in turn be adjusted on the basis of a differential path, for example by means of the difference path sensor just mentioned by adjusting the difference path corresponding to the newly calculated characteristic F _in _{-F sup} .

FIG. 4 shows two different amplifier characteristics. On the vertical axis 404, the output force F _ou t 6 is applied, ie the sum of

Actuating force F _in _FIG . 3 and assisting force F _sup 2. On the horizontal axis 405, the input force F _in FIG. 3 is plotted. The course of the characteristic 401 is the course of a conventional brake booster. The output force increases only after a certain input force, in Figure 4 at a point 406th This is followed by a range of the characteristic in that the output force F _ou t 6 increases at constant operating force F _in 3, followed by a portion 408, which a linear relationship between Output Force F _ou t 6 and actuating force F _in Fig. 3 shows. In a region 409 of the characteristic curve, the brake booster is already in an operating mode, which is also referred to as run out. Here, the brake booster the predetermined

Reinforcement no longer or at least not completely muster.

For example, compared to the curve of the characteristic curve 401 of a conventional brake booster, the optimized amplifier characteristic based on equation 1 can have a profile, as shown by the curve 402 in FIG. The characteristics such as maxima, minima, slopes and / or turning points in the curve are not to be understood as limiting, but are merely illustrative. The curve shown should represent that the optimized amplifier characteristic differs from the usual characteristic according to which the brake booster is otherwise operated. The course of the curve may have different characteristics for different vehicles, different brake booster, each with different structural design and components used. However, it is characteristic that the curve deviates only from the conventional curve as soon as the input force F _in FIG. 3 has exceeded point 406. Once point 406 is exceeded with respect to the input force, the method is used. The arrow 403 in FIG. 4 indicates what happens when a further braking effect is connected at a constant actuating force F _in FIG. The assist force F _sup 2 is reduced to keep the overall braking effect constant.

If one operates the brake booster with an optimized characteristic amplifier according to Equation 1, so, leads to the fact that, for infinitesimally small changes in assist force F _sup the change in the input path s _in equal to zero.

With changes in the support force F _sup finite size, however, the operation of the brake booster with the optimized amplifier characteristic again leads to an offset of the input element 4, ie to a change of s _in 202. The optimized amplifier characteristic is thereby, as indicated by the arrow 403 left. This means that a complete compensation of the offset of the input element 4 is also not possible by using an optimized amplifier characteristic.

So that the driver feels no offset of the input element, he could change the input power 3 by a certain amount. Thus, it would be possible, despite changed support force 2 of the brake booster _to maintain the operating position of the input member s _in . However, he would notice this change in input power 3.

The use of an amplifier characteristic according to equation (1) with the addition of a regenerative braking effect reduces the additional force to be applied by the driver to keep the input element 4 in a reduction of the assist force F _sup at a fixed actuation position s _in . In particular, the additional force to be applied by the driver is minimized.

In a further embodiment of the invention, reduced by the method described above the necessary change in the input power is 3, which is necessary to hold the input member 4 at a fixed operation position s _in, applied by an additional force. It is especially provided that by this additional force the operating position s _in at a constant operating force F _in 3 of the driver can be kept constant and will. It must be considered below that the input force 3 is no longer necessarily applied by the driver alone, but may include an additional force in addition to the proportion originating from the driver.

Analogous to the derivations described above, the elasticity ε of the hydraulic brake system can be written as a function of the output force F _out as follows

ds ","

P (F = F. + F

If the variation of the actuation position 202 of the input element 4 is also formed analogously to the above-described method, then in the case of a linear elastic reaction disk:

Here Ä _sup and AF are _in changes of the support 2 and the

Input force 3, c corresponds to the value of the elasticity 204 of the reaction disk 9 with respect to input force / input path. From this equation, it can be seen how a change in the assisting force 2 and the input force 3 affect the operating position 202.

In addition, it is assumed that the elasticity of the reaction disk 9 has already been adapted so that it already compensates for a certain part of the offset of the input element 4, which occurs or would occur if the support force is reduced at a constant input force. This corresponds to the situation as described above in equation 1 of the first embodiment of the method according to the invention. This can be expressed as follows. EAF sup - - ^ AF sup £ £ sup

X

ε- «ε

c

On the basis of this equation and together with equation 2, the following can be seen: the proportion of the path which is based on the backflow of the brake fluid from the brake system (eAe _sup ) is determined by the

Deformation of the reaction disc due to the reduction of

X

Support force (- AF _: ^' ) significantly reduced. Since, however, as above c

described is not completely the case, there remains a small residual path As _jn , which still has to be compensated, or which still needs to be reduced.

This can now be masked by a change in the input force, ie via the term "ε + - F _: "".

In contrast to the first embodiment of the method according to the invention, F _in does not only include the actuating force applied by the driver, hereinafter referred to as F _F , but additionally a force, which is referred to below as F _r .

In the first described embodiment of the method _{according to} the invention, the change of the input force AF _jn a \ s zero was assumed because the

Driver has applied a constant operating force F _F as the only contribution to the input force F _in FIG. A constant driver force will continue to be assumed below.

The additional force F _r , however, may change. Since a constant operating force AF = _F 0, the change of the input force 3 in equation (2) can be written as follows:

AF in = AF F _F + AF r = AF r By substituting into Equation (2), it can be seen that by applying an additional force AF _r compensates for an additional path of As

can be.

In order to compensate for the remaining way, which could not yet be compensated by way of the reaction disk 9, this additional force AF _r must be applied.

The additional force z_v _r can now be applied in different ways.

In a first embodiment, the additional force 501 F _{r may be} a passive applied force. By this example, a static friction can be understood. This situation is shown in FIG. If the support force F _{sup changes,} an offset of the input element 4 is to be expected. Keep this in an additional surface 502 the result is a change in the additional KraftÄ _r, in this case, the friction force because the

Static friction is a reaction force. The friction between the surface 502 and the input element 4 is represented in FIG. 5 by the reference symbol μ. However, this method only works if the driver does not change the pressure during the braking process with a regenerative and hydraulic brake system or does not specify a change request.

Alternatively or additionally, the friction force 501 can also be controlled or regulated. For example, a brake may be provided on the input element 4, which is provided with an actuator. This actuator can be designed very small. For example, the frictional force may be controlled and / or controlled using the actuation travel of a piston of the master cylinder (not shown) and the deviation of the assist force from the associated value without regenerative braking (ie, deviation from the static equilibrium value) as control and / or control quantities. For example, an automatic mechanical regulation 600 of the additional force on the input element is possible. This is shown in Figure 6 on the equivalent model of the brake booster. An elastic member 601 is structurally connected to the booster body 8. In addition, the elastic element 601 can come into contact with a lever arm which is rotatably and / or tiltably mounted on a holder. The holder is structurally connected to the input rod 4. When the booster body 8 moves in relation to the input rod 4, the position of the elastic member 601 with respect to the lever arm 602 also changes. The lever arm is designed to apply a force 603 to the input rod 4. About this force, the input element 4 is pressed against a surface 604 and thus leads to a static and / or sliding friction, symbolized in Figure 6 by the reference numeral μ. By the direction in which the booster body 8 moves with respect to the input member 4 - in the construction and / or degradation of the support force F _sup - the amount of the force 603 can be varied. In this way, the additional force, so the friction force can be adjusted. The adjustment of the friction force described here is based on a frictional force, which depends on a differential path of the amplifier body 8 and the input element 4. By the design, positioning, dimensioning and mounting of the lever arm 602, the surface 604 and / or the elastic member 601, the manner in which the frictional force varies with the differential path can be specified.

It should be noted that the described mechanical control of the additional force can be used both in construction, as well as in the reduction of the support force, so when switching a regenerative braking system as well as when switching off a regenerative braking system.

Alternatively, the reduction of an existing friction force is possible. This possibility arises, for example, when a brake described above has already been actuated. With a fixed input element, the static friction force can be used as it represents a reaction force. However, if the driver still models the pressure, this is not possible. Instead of providing the additional force on the static friction force, as described above in the passive variant, now a reverse sliding friction force reduced. This works because the Gleitreib force always counteracts the movement. This reduction of Gleitreibkraft can be done by means of a control or regulation of a brake as already described or purely mechanical as shown in Figure 6. For this purpose, the effect of the brake, which affects the Gleitreibkraft on the input element 4, must be reduced.

Alternatively or additionally, the additional force F _{r can} also be applied by means of a further actuator 701, which transmits the additional force to the input element 4. This is shown schematically in FIG. One possible embodiment of such an actuator is an electric motor which, if appropriate, acts on the input element 4 with the additional force via a gear stage.

The use of a frictional force as additional force can lead to a hysteresis in the brake operation, ie to a different behavior of the brake booster in power compared to a force reduction on the input rod 4 by the driver with respect to the resulting output force F _ou t- Da this behavior However, also occurs in conventional brake boosters, it is known to the driver and can even be felt to be beneficial.

The described process components, ie the use of an optimized amplifier characteristic curve and the application or regulation / control of the additional force during regenerative braking for path compensation need not be considered in isolation from one another. It is also conceivable and possible, and even advantageous to operate the two embodiments in succession or in parallel. Operate the brake booster in non-regenerative braking based on the optimized amplifier characteristic, so reduces the displacement of the input member when a generator torque, and reduces the additional force applied, which is required to hold the input member at an operating position. In order to completely hide the switching on of the regenerative braking system, the additional force in at least one of the following can optionally then be subsequently connected described species are applied. It is also conceivable to operate the amplifier in non-regenerative braking, ie in purely hydraulic braking according to a conventional characteristic, for example characteristic curve 401 in FIG. 4, and then to switch the characteristic curve when the regenerative braking system is switched on, to the optimized characteristic curve. However, the transition could be noticed by the driver.

In general, it should be noted that although the methods and applications described here have only been described when connecting a regenerative partial braking system, they are in no way limited thereto. Similarly, a shutdown of a regenerative partial braking system is possible, or a

Change in the respective shares of the hydraulic and the regenerative partial braking system on the overall braking effect.

Claims

claims

1) A method for operating an adjustable brake booster (1) of a hydraulic brake system wherein the brake booster (1) a support force on an output member (5) of the brake booster, wherein the applied support force (2) in response to at least one information relating to at least one elastic element (9), which is located between an input element (4) of the brake booster and the output element (5), at least one information regarding a pressure-volume relationship of the hydraulic brake system is determined, in particular a pV characteristic curve,

and a driver applied input force (3) applied to the input member

is determined and the support force (2) is set.

2) A method according to claim 1, characterized in that the supporting force (2) is adjusted at an applied by the driver input force (3) such that a retroactive effect on the driver with a change of the supporting force (2) is reduced.

3) A method according to claim 1, characterized in that the supporting force is adjusted such that an infinitesimal small change in the assisting force (2) leads to a vanishing displacement of the input element (4) of the brake booster (1), in particular to a zero shift.

4) A method according to claim 1, characterized in that the supporting force is adjusted such that at a finite change of the supporting force (2) an additional force (603, 501, μ, 701) to the input force (3), which must be applied to the Input element (4) to hold in the same position is minimal, in particular equal to zero.

5) Method according to claim 4, characterized in that the additional force to be applied by an actuator (701) is applied.

6) Method according to claim 4, characterized in that the additional force to be applied by a friction force (501) is applied.

7) Method according to claim 5 and / or 6, characterized in that the additional force to be applied by a controlled friction force (601), in particular by a brake is applied, in particular by a mechanically and / or electrically controlled friction force (601).

8) Method according to claim 7, characterized in that the brake is a friction brake which acts directly or indirectly on the input element (4).

9) Method according to at least one of the preceding claims, wherein the brake booster (1) is part of a hydraulic partial braking system of an overall braking system, characterized in that by the change of the supporting force (2) a hydraulic braking torque is set, wherein by means of the hydraulic braking torque a braking torque difference between a total braking torque and a regenerative braking torque is reduced, in particular this braking torque difference is compensated.

10) Method according to claim 1, characterized in that the support force to be applied as a function of the input force or the input path of the input element (4) is deposited by means of a characteristic in the vehicle, the characteristic as a function of at least one information relating to the at least one elastic Element (9) and in dependence of at least one information relating to a pressure-volume relationship of the hydraulic brake system is determined. 11) A method according to claim 10, characterized in that the characteristic curve is recalibrated, in particular at maintenance intervals or as part of a check before or at the start of the vehicle.

12) A method according to claim 1, characterized in that the applied support force (2) during braking, depending on the input force, the at least one information relating to the at least one elastic element (9) and in dependence on at least one information relating to a pressure - Volume relationship of the hydraulic brake system is calculated.

13) A method according to claim 10 or 12, characterized in that the input force is determined by means of a force sensor or calculated on the basis of at least one signal of a displacement sensor of the input element (4).

14) controllable brake booster characterized in that the brake booster (1) a support force (2) on an output element (5) of the brake booster (1) applies, wherein the applied supporting force (2) of

at least one piece of information regarding at least one elastic element (9), which is located between an input element (4) of the brake booster and the output element (5), of at least one information relating to a pressure-volume relationship of the hydraulic brake system, in particular a pV- Curve,

and an applied by the driver input force (3), which is applied to the input member

depends.

15) A brake booster according to claim 14, characterized in that the brake booster the supporting force (2) and an additional force (603, 501, μ, 701), which at a finite change of the supporting force (2) on the input member (4) must be applied , and applies an offset of the input element (4) counteracts, in particular the input member (4) holds in the same position.

16) brake booster according to claim 15, characterized in that the brake booster comprises an additional actuator (701, 600) of the additional force (603, μ, 701) applies.

17) brake booster according to claim 14 or 15, characterized in that the brake booster mechanically and / or electromechanically actuated brake which acts on the input element (4) of the brake booster (1), wherein by pressing the brake, the additional force (603, 501 , μ) is applied.

18) control unit for carrying out the method for operating a brake booster according to at least one of the preceding claims, wherein the applied support force (2) is calculated by the control unit or determined by a characteristic, and wherein the brake booster by the control unit for adjusting the supporting force and optionally the Additional power is controlled.