DE102017221055A1 - Brake system for motor vehicles with Fußeinklemmschutz - Google Patents

Abstract

A braking system (2) for motor vehicles, comprising hydraulically actuated wheel brakes (50, 52, 54, 56), which are pressurized via brake lines with pressure; a brake pedal (6) and a pedal push rod (300) coupled to the brake pedal and exerting an actuating force on a master cylinder (10) when pressure is applied to the brake pedal (6) in a master cylinder related axial direction of actuation; a master brake cylinder (10) via the brake lines (180, 182) can be acted upon with pressure, with a master brake cylinder piston (14) which is actuated via the pedal push rod (300); a third-party actuating device, by means of which the master brake cylinder can be operated electronically controlled independently of and in superimposition to a pedal operation performed by the driver, the brake pedal (6) being moved during a foreign operation, a displacement of the pedal pressure rod (300) against the master brake cylinder piston (14) is limited in the direction of actuation by a stop means so that compressive forces are transmitted from the pedal push rod (300) without restriction to the master brake cylinder piston (14), while a displacement of the pedal push rod (300) relative to the master brake cylinder piston (14) is allowed against the direction of actuation by a mechanical lots , wherein elastic means are provided, which cause a tensile force due to elasticity between master brake cylinder piston (14) and pedal push rod (300) and thus also in the pedal push rod (300) when using the lots.

Description

• • hydraulisch betätigbare Radbremsen, die über Bremsleitungen mit Druck beaufschlagbar sind;
• • ein Bremspedal sowie eine mit dem Bremspedal gekoppelte Pedaldruckstange, die beim Ausüben von Druck auf das Bremspedal in einer hauptbremszylinderbezogen axialen Betätigungsrichtung eine Betätigungskraft auf einen Hauptbremszylinder ausübt;
• • einen Hauptbremszylinder, über den Bremskreisleitungsabschnitte mit Druck beaufschlagbar sind, mit einem Hauptbremszylinderkolben, der über die Pedaldruckstange betätigbar ist;
• • einer Fremdbetätigungseinrichtung, über die der Hauptbremszylinder unabhängig von und in Überlagerung zu einer von Fahrer durchgeführten Pedalbetätigung elektronisch gesteuert betätigt werden kann

wobei bei einer Fremdbetätigung das Bremspedal mitbewegt wird.The invention relates to a braking system for motor vehicles, comprising

• • hydraulically actuated wheel brakes, which can be pressurized via brake lines;
• • a brake pedal and a brake pedal coupled to the pedal pressure rod, which exerts an actuating force on a master cylinder when exerting pressure on the brake pedal in a master cylinder related axial actuation direction;
• A master cylinder, via which brake circuit line sections can be pressurized, with a master brake cylinder piston, which can be actuated via the pedal pressure rod;
• • a third-party control device that allows the master cylinder to be electronically controlled independently of and in superposition of a pedal operation performed by the driver

wherein during a foreign operation, the brake pedal is moved.

In hydraulic brake systems with a third-party actuator, which is designed as a so-called active brake booster with entrained pedal, the brake booster is electronically controlled to perform an automated braking, wherein the brake pedal is moved. A brake booster is referred to as an "active" brake booster, if it can be caused in addition to the brake pedal by means of electronic signals for the controlled construction of a boosting or external actuating force.

The brake pedal of a vehicle is arranged in front of a driver in a direction of travel in front of a driver by means of an end wall (called a "bulkhead" in automotive engineering) and is displaceable by the driver from a rest position into an actuated position. The rest position is further away from the end wall than the actuation position. In the conventional design of the brake pedal as a pivotable about a hinge lever with a treadle case may occur that in the space that is traversed by the lever and pedal between the rest position and the actuation position, objects are penetrated, which prevent pivoting of the pedal lever or damaged by pivoting the pedal lever. In particular, in this way injuries to the driver's feet are possible by being clamped under the brake pedal.

Due to the mechanical coupling of the brake pedal lever with the active brake booster, the brake pedal is during an automatic, executed by the active brake booster brake engagement in a position corresponding to the current brake operation, so that sets the driver a familiar brake feel with the deceleration corresponding brake pedal lever pivot angle, if he would like to additionally operate the brake pedal lever in such a situation.

The DE 103 29 720 A1 describes a pedal assembly for a motor vehicle in which the space under the brake pedal is filled with a foam which is intended to prevent foreign bodies from entering this space.

The DE 10 2006 020 304 A1 suggests that a detection device monitors the space under the pedal and that in the case of the presence of a foreign body on an automated operation is dispensed with. The DE 10 2014 211 008 A1 describes a method according to which a pinching force is to be determined in an electronic control unit of the brake booster from the sensor data present in its regular operation in order to dispense with detected Einklemmkraft on an automated actuation of the brake booster.

A disadvantage of the mentioned solutions is that either additional installations in the footwell are necessary, which may hinder an automated actuation of the brake booster, or additional sensors must be installed, which limits the function of the brake system in an undesirable manner when detected Einklemmgefahr and also be monitored consuming must, because even with a failure of this sensor, the function of the automated brake operation must be turned off, because the brake system in this case can no longer provide protection against the pinching of the foot.

The invention is therefore based on the object to improve an actuating device to the effect that is prevented by simple structural means that a foot located under the brake pedal is seriously injured. A second aspect of the invention is to enable an automated control of the brake booster in the case of a pedal blockade.

This object is achieved in that a displacement of the pedal pressure rod against the master brake cylinder piston is limited in the direction of actuation by a stop means so that compressive forces are transmitted from the pedal pressure rod without restriction to the master cylinder piston, while a displacement of the pedal pressure rod relative to the master cylinder piston against Actuation direction is permitted by a mechanical lots, wherein elastic means are provided, which cause a tensile force due to elasticity between the master cylinder piston and pedal pressure rod and thus in the pedal pressure rod when using the lots.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that in brake systems with hydraulic brake booster, the brake pedal is moved during automated braking, so that it can come to a pinching of a foot in the footwell under the pedal. In order to avoid injuries in such a case, methods have been developed which aim to detect jamming and then cancel the so-called third-party operation of the brake booster. Because of the associated loss of functionality, such a concept is not acceptable in terms of safe automated driving. In addition, this requires special costly sensor technology and a significant additional expenditure on installation. It would therefore be desirable to realize by passive and simple constructive means an anti-trap, which also allows the function of a third-party operation of the brake booster when the brake pedal hits an obstacle on its intended actuation path.

As has now been recognized, such an anti-trap can be realized by the pedal push rod is connected via a spring to the brake booster piston. If an object is clamped under the brake pedal, then the clamping force is limited by the spring force. A foot under the brake pedal can be easily pulled out by counter-pressure against the spring again.

Advantageously, the pedal pressure rod at its end facing the master brake cylinder on a Pedaldruckstangenkopf, which is designed for transmitting compressive and tensile forces.

The pedal push rod head is preferably guided in an axial blind bore of the master brake cylinder piston.

Serving for the transmission of compressive forces between Pedaldruckstangenkopf and master brake cylinder piston stop means are preferably structurally designed such that they allow pivoting of the pedal pressure rod in the sense of a limited angular rotation of the axes of pedal pressure rod and master cylinder piston against each other.

The stop means are preferably formed by a body of elastomeric material which is deformable but substantially incompressible.

For the transmission of tensile forces between Pedaldruckstangenkopf and master brake cylinder piston elastic means are advantageously present, which oppose a disengagement of pedal push rod and master cylinder elasticity-induced tensile forces, which are structurally dimensioned so that they lead to only safe trapping forces on objects between the brake pedal and dashboard.

An exemplary dimensioning is a weight of 10 kg, which placed on the foot exerts a weight of about 100 Newton. Such a load is uncomfortable but harmless to the driver.

The elastic means for transmitting tensile forces are formed in a preferred embodiment as a compression spring.

The compression spring is advantageously supported on the master brake cylinder piston in the region of its pedal-side end. It also relies on preferred on Pedaldruckstangenkopf.

In a preferred embodiment, the compression spring is designed as a helical spring, preferably made of metal, which is wound in particular from spring steel wire.

Preferably, the coil spring is penetrated by the pedal pressure rod, i. the pedal push rod is at least partially surrounded by the helical spring.

Advantageously, the coil spring is arranged in a bore of the master brake cylinder piston.

Advantageously, means are provided to generate frictional forces during a relative movement between the pressure rod head and the master cylinder, whereby possible relative movements are damped.

The master cylinder is preferably designed as a tandem master cylinder with an operable with the brake pedal primary piston and a, in particular floating, secondary piston.

The advantages of the invention are, in particular, that the anti-pinch protection described is structurally simple to implement and requires no additional sensors. At the same time he allows the Carrying out automated braking even with blocked pedal movement.

An embodiment of the invention will be explained in more detail with reference to a drawing. In it, the only figure shows a braking system 2 with one by means of a brake pedal 6 actuated master cylinder 10 who has a primary piston 14 which has a primary chamber 16 limited, in which a return spring 18 is arranged. A floating secondary piston 22 limits a secondary chamber 24 in which a return spring 28 is arranged. Each with a compensation line 32 . 36 are primary chamber 16 or secondary chamber 24 with a pressure medium reservoir 40 connected in the unactuated position of the piston. In the respective compensation line 32 . 36 is in each case a normally open container separation valve 42 . 44 arranged, the electrical activation of the respective master cylinder chamber 16 . 24 hydraulically from the pressure fluid reservoir 40 separates. The one from the primary piston 14 The distance traveled is by a preferably redundantly designed displacement sensor 20 measured.

The brake system 2 has four hydraulic wheel brakes 50 . 52 . 54 . 56 on, as well as four Raddrehwinkelensoren 60 . 62 . 64 . 66 , Every wheel brake 50 - 56 are each a normally open isolation valve 70 . 72 . 74 . 76 and in each case a normally closed exhaust valve 80 . 82 . 84 . 86 assigned. When electrically activated, the isolation valves stop 70 . 72 . 74 . 76 a pressure build-up in the respective wheel brake 50 - 56 by hydraulically disconnecting the respective hydraulic pressure connection of the wheel brake. The exhaust valves 80 . 82 . 84 . 86 allow electrical pressure to release pressure from the wheel brakes 50 - 56 towards the container. These are the output sides of the exhaust valves 80 . 82 . 84 . 86 hydraulically with the pressure fluid reservoir 40 connected.

In each of the isolation valves 70 . 72 . 74 . 76 is each a check valve 100 . 102 . 104 . 106 integrated, the function of the electromagnetically controllable valve stage is connected in parallel and allows outflow of pressure medium from the wheel brakes to the respective master-cylinder-side valve connections, regardless of the electrical control state of the valve. The brake system 2 has a control unit 96 on.

The brake system 2 has a pressure supply device 120 on with one of a plunger 126 limited pressure chamber 132 , where the piston 126 from an electric motor 136 and a rotational-translation gear 142 for active pressure build-up in the pressure chamber 132 in a pressure build-up direction (in the illustration to the left).

The brake circuit I associated brake circuit pressure line 180 connects the main cylinder chamber 16 with the master cylinder-side connections of the isolation valves 70 and 72 and the wheel side connection of the Zuschaltventils 236 , The brake circuit II associated brake circuit pressure line 182 connects the main cylinder chamber 24 with the master cylinder-side connections of the isolation valves 74 and 76 and the wheel side connection of the Zuschaltventils 238 , At least one of the brake circuit pressure lines 180 . 182 is a preferably redundant executed pressure sensor 190 connected, with which the master cylinder pressure is detected.

A suction line 146 connects the pressure fluid reservoir 40 with a check valve 152 , This suction valve prevents drainage of pressure medium from the pressure chamber 132 to the container 40 and allows a sucking of pressure medium from the container into the pressure chamber 132 , In the pressure room 132 pressurized brake fluid can via a valve 214 in a system pressure line 160 . 170 . 200 be fed. With electrically activated valve 214 can the pressure chamber when returning the piston 120 also absorb pressure medium from the system pressure line.

Other components connected to the system pressure line are a master cylinder drive chamber 210 , a system pressure relief valve 234 , Which is designed as an analog controllable pressure control valve, can be controlled via the pressure medium discharged from the system pressure line into the container, the hydraulic output of a pump 222 , which is adapted to suck pressure medium from the container and to feed into the system pressure line, and a first Zuschaltventil 236 , about which the brake circuit I associated brake circuit pressure line 180 with the system pressure line 160 and a second Zuschaltventil 238 , about which the brake circuit II associated brake circuit pressure line 182 also with the system pressure line 160 can be connected. In the proposed normal braking function so all wheel brakes are subjected to a common system pressure, while the hydraulic separation is reserved in two separate brake circuits of an emergency mode reserved.

The system pressure is by means of a preferably redundant pressure sensor 191 detected.

A trained as an annular space drive chamber 210 is permanent with the system pressure line 160 connected so that the master cylinder piston or primary piston 14 via an annular active surface with the surface A _verst is driven in the direction of actuation with a force proportional to the system pressure.

The brake system 2 also has one of a motor 220 as needed driven pump 222 their discharge volume into the system pressure line 160 feeds. With the pressure delivery device 120 and the engine-pump unit 220 . 222 a system pressure build-up is ensured in a redundant way. It is also possible to use the two different system pressure sources according to their specific advantages. For example, the pressure delivery device works 120 particularly precise and quiet, while piston pumps for brake systems are usually specialized in delivering very high pressures.

The wheel brakes 50 . 52 are assigned to a first brake circuit I can be assigned to a common vehicle axle (axle brake circuit division) or also assigned to a front wheel and a rear wheel (diagonal brake circuit split). The wheel brakes 54 . 56 are assigned to a second brake circuit II.

In normal operation, there are activated connection valves 236 . 238 the brake circuit pressure lines 180 . 182 with the system pressure line 160 connected together. The pressures in both brake circuit pressure lines are then equal to the system pressure. Hydraulic is the master cylinder primary piston 14 over the drive chamber 210 a driving force A _verst • system pressure and via the master cylinder chamber 16 a restorative force A ₁ • exposed to system pressure. Because A ₁ greater than A _verst remains as the resulting restoring hydraulic force ( A ₁ - A _verst ) • System pressure which the driver has to overcome by pressing the pedal. This corresponds to a hydraulic power gain by the factor A ₁ / ( A ₁ - A _verst ).

It is known that a brake system via the brake pedal is more pleasant to operate when the effect of the brake booster at the first start, that is raised for small pedal travel. This is in the present brake system by a sleeve 250 realized in the drive chamber 210 acts as Antriebsflächenvergrößerungskörper or Wirkflächenvergrößerungskörper. This effect unfolds limited to an initial path of the pedal, because the sleeve 272 with increasing Pedalweg on a against the housing of the master cylinder 14 supported spring touches down, which over the sleeve 250 additionally applied driving force reduced.

If one chooses the hydraulically effective surface of the sleeve 250 so that the effective combined effective area A _verst equal A ₁ is, there is infinite gain. This means that by applying pressure to the brake pedal, a hydraulic pressure can be set without this pressure exerting a resetting effect. The pedal can be positioned with the foot against only the restoring forces of the springs. In this operating situation, the pedal travel is detected and converted by means of electronic control based on a predetermined characteristic curve in a target system pressure, which is then converted by means of the pressure plate in an actual system pressure.

A particularly pleasant pedaling behavior is obtained when the hydraulically effective surface of the sleeve 250 is chosen so that the effective combined effective area A _verst is slightly smaller than A ₁ . This results in a noticeable, the dosing of the brake actuation facilitating, hydraulic reaction to the pedal force even with small pedal paths. The hydraulic restoring force is not fully compensated in such a structural design.

The brake system 2 is thus adapted to pedal and / or piston paths which are less than a predetermined threshold, the hydraulic effective area A _verst to a value close to but below the hydraulic effective area A1 of the primary piston 14 to enlarge. After a fixed brake pedal travel, this increase in area is no longer effective. This is the sleeve 250 provided that the primary piston 14 at least partially encloses.

The sleeve 250 or the Wirkflächenvergrößerungskörper encloses this partially the edge of the primary piston 14 in the drive chamber 210 , so that when introducing pressure medium into the drive chamber 210 primary piston 14 and sleeve 250 to move to the same extent in the direction of actuation. This will be the hydraulic effective surface A _verst of the hydraulic brake booster to a value in the vicinity, but below the hydraulic effective area A ₁ elevated. The application of both opposing surfaces ( A ₁ on the front side of the primary piston 14 and A _verst on the side of the amplifier chamber or drive chamber 210 ) with almost equal, oppositely directed forces causes them to cancel each other out. In this way, in the case of pedal and / or piston paths which are less than a predefined threshold value, a brake system pressure p can be brought to a preferably brake pedal travel-dependent value, without this being the only force effect on the brake pedal provided for larger pedal travel 6 entails.

After a predetermined brake pedal travel, the sleeve is supported 250 additionally on one in an annular chamber 266 arranged elastic element 270 from, which is presently designed as a compression spring. Above this pedal or Kolbenweg value, the hydraulically kraftbeaufschlagte sleeve is supported 250 not completely on the primary piston 14 but also in an increasing with the piston stroke dimensions on the spring. If, with increasing compression travel, the residual spring travel still available approaches zero because the pressure spring is compressed to its block length or another spring deflection by other measures such as, for example, the formation of a stop between the return force compensation body 250 and a housing 272 of the master cylinder 10 is no longer possible, the sleeve is supported 250 completely off the case, allowing for the contact force between sleeve 250 and primary pistons 14 no share of force remains. The sleeve 250 stops and only the primary piston 14 keeps moving. From this and for even greater pedal travel, the hydraulic brake booster works as a power amplifier. The restoring force compensation body 250 is preferably made of a metal such as aluminum or steel.

When using the third-party actuator to perform an automated braking, the brake pedal 6 entrained or moved. The brake system 2 is designed to prevent yourself from getting under the brake pedal at this time 6 foot is injured. In addition, even during a blockage of the brake pedal 6 still be an automated braking possible.

This is a pedal push rod 300 , which with the brake pedal 6 for actuating the primary piston 14 is coupled, with an elastic means, for example a helical compression spring 306 to the primary piston 14 or brake booster piston connected. This is a cavity 310 provided, in which at least partially the pedal pressure rod 300 is arranged at her the primary piston 14 facing end a Pedaldruckstangenkopf 312 has, which acts as an actuating element and which may be formed, for example, as a ball or cylinder.

Between pedal push rod head 312 and a brake pedal 6 zugwandten end of the cavity 310 is the spring 306 clamped, ie it relies on the one hand on the Pedaldruckstangenkopf 312 and on the other hand to an annular Auflagefäche at this end of the cavity 310 from. The pedal pressure rod head 312 is from the spring 306 in the cavity up to a stop on the primary piston 14 pushed. For flat distribution of the stop contact forces is a plastically deformable stop body 314 For example, provided a cylindrical disc made of an elastomeric material. Upon actuation of the brake pedal 6 through the foot transfers the pedal push rod head 312 the pedal lever translated operating force on the stop body 314 on the primary piston 14 ,

The pedal pressure rod head 312 is preferred in an axial blind bore of the master brake cylinder piston 14 guided. Opposite to the operating direction of the brake pedal 6 is realized a mechanical lots, wherein elastic means (compression spring 306 ) are provided, which in use of the lots elasticity-induced tensile force between the master cylinder piston 14 and pedal push rod 300 and thus also in the pedal push rod 300 effect. The mechanical lots is in particular given by the fact that mechanical play between the Pedaldruckstangenkopf 312 and the primary piston 14 given is.

In a foreign braking, the tensile force transmission property of the pedal connection according to the invention comes into play. The compression spring for transmitting tensile forces tows the pedal.

If in an automated braking with the help of the brake booster 276 a foot under the brake pedal 6 jammed, the clamping force is due to the spring force of the spring 206 limited. This means that the driver feels the pressure of the spring on the foot 206 , The driver can also resist the pressure of the spring 206 the brake pedal 6 push up and free his foot. Will the brake pedal 6 blocked, can still use the primary piston 14 be hydraulically actuated by adding pressure medium into the booster chamber 210 is pressed.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10329720 A1 [0005]
• DE 102006020304 A1 [0006]
• DE 102014211008 A1 [0006]

Claims (12)

Brake system (2) for motor vehicles, comprising • hydraulically actuated wheel brakes (50, 52, 54, 56), which can be pressurized via brake lines; A brake pedal (6) and a pedal push rod (300) coupled to the brake pedal exerting an actuating force on a master cylinder (10) when pressure is applied to the brake pedal (6) in a master cylinder related axial direction of actuation; • a master brake cylinder (10) via the brake circuit pressure lines (180, 182) can be pressurized with a master brake cylinder piston (14) which is actuated via the pedal push rod (300); A third-party operating device, via which the master cylinder can be operated electronically controlled independently of and in superposition to a pedal operation performed by the driver, wherein in a foreign operation, the brake pedal (6) is moved, characterized in that a displacement of the pedal push rod (300) against the Master cylinder piston (14) in the actuating direction by a stop means (314) is limited, so that pressure forces from the pedal push rod (300) without restriction to the master brake cylinder piston (14) are transmitted, while a displacement of the pedal push rod (300) relative to the master brake cylinder piston (14) opposite Actuating direction is permitted by a mechanical lots, wherein elastic means (304) are provided which cause a tensile force due to elasticity between the master brake cylinder piston (14) and pedal push rod (300) and thus in the pedal push rod (300) when using the lots. Brake system (2) after Claim 1 , wherein the pedal pressure rod (300) at its the master cylinder (10) facing the end of a Pedaldruckstangenkopf (312), which is designed to transmit compressive and tensile forces. Brake system (2) after Claim 2 wherein the pedal push rod head (312) is guided in an axial blind bore of the master brake cylinder piston (14). Brake system (2) after Claim 3 , wherein for transmitting compressive forces between Pedaldruckstangenkopf (312) and master brake cylinder piston (14) serving stop means are constructively designed such that they pivot the pedal push rod (300) in the sense of a limited angular rotation of the axes of pedal push rod (300) and master cylinder piston (14) against each other allow. Brake system (2) after Claim 4 wherein the stop means are formed by a body of elastomeric material which is deformable but substantially incompressible. Braking system (2) according to one of Claims 2 to 5 wherein the elastic means for transmitting tensile forces between the pedal push rod head (312) and the master brake cylinder pistons (14) are designed to oppose tensile forces of the pedal push rod (300) and master cylinder (10) against only harmless pinching forces of objects between them Guide the brake pedal and the bulkhead. Brake system (2) after Claim 6 , wherein the elastic means for transmitting tensile forces are formed as a compression spring. Brake system (2) after Claim 7 , wherein the compression spring is supported on the master brake cylinder piston in the region of its pedal-side end. Brake system (2) after Claim 7 , wherein the compression spring on the pedal push rod head (312) is supported. Brake system (2) after Claim 9 , wherein the compression spring is designed as a helical spring, preferably made of metal, which is wound in particular from spring steel wire. Brake system (2) after Claim 10 , wherein the coil spring is penetrated by the pedal push rod (300). Braking system (2) according to one of Claims 2 to 11 in which means are provided in order to generate frictional forces during a relative movement between pedal push-rod head (312) and master brake cylinder (10), whereby possible relative movements can be damped.

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