DE102014216341A1 - Hydraulic brake booster and method for its operation - Google Patents

Abstract

Hydraulic brake booster for actuating a working piston (12) of a master brake cylinder (9) of a hydraulic brake system for motor vehicles, comprising a housing (5) in which a booster piston (2) is displaceably guided, the booster piston (2) being connected to the housing (5). a booster chamber (13) bounded, an electrically controllable pressure medium source (11) which is connected to the booster chamber (13), wherein by building up a pressure in the booster chamber (13) by means of the pressure medium source (11) of the booster piston (2) in one Brake operation direction is displaceable, one with a brake pedal (4) coupled actuating piston (1), an actuating element (18) for actuating the working piston (12), and a body (3) made of elastic material, which between the actuating piston (1) and the booster piston (2) on the one hand and the actuating element (18) on the other hand is arranged, wherein the booster chamber (13) b ei unactuated actuating piston (1) with a return port (25) to a pressure medium reservoir (16) is hydraulically connected, wherein upon actuation of the actuating piston in the brake actuation direction of the actuating piston (1) to the booster piston (2) can be applied to the booster chamber (13) to separate from the return port, and method for its operation.

Description

The invention relates to a hydraulic brake booster for actuating a master cylinder of a hydraulic brake system for motor vehicles according to the preamble of claim 1 and a method for its operation.

From the publication DE 37 26 525 A1 a hydraulic booster for actuating a master cylinder in a hydraulic brake system for motor vehicles is known, which comprises a pressure medium supply means for building a pressure in an booster chamber, an actuating piston coupled to the actuating piston, a booster piston, a power transmission element for actuating the working piston of the master cylinder and between actuating piston and Amplifier piston on the one hand and the power transmission element on the other hand arranged rubber reaction disc comprises, wherein the booster piston in an inner space receives the actuating piston, the rubber reaction disc and an end of the force transmission element. Furthermore, the booster comprises a control device for controlling the hydraulic pressure in the booster chamber comprising a control spool movable by the actuating piston by means of a double lever mechanism and two seat valves, which are actuated by the spool and open a pressure medium discharge line to a non-pressurized reservoir and a pressure medium supply line from the pressure medium supply means or shut down. Due to the number of components, in particular the double lever mechanism, the spool and the two seat valves, the power amplifier is complex to manufacture and requires a relatively large amount of space.

In the DE 100 17 341 A1 a hydraulic brake booster is described with a housing in which in coaxial arrangement a booster piston, a piston integrated in the booster piston and arranged in a receiving bore of the combi piston integrated brake pressure control piston, which is connected to an actuating piston. An intensifier chamber is defined by the transmission piston and the combination piston. A reaction disc is disposed between a push rod for actuating the master cylinder and the combination piston, wherein between the reaction disc and the brake pressure control piston, a pressure piece is arranged. The brake pressure control piston and the combination piston comprise various control openings or holes, in order to connect the booster chamber for actuating the combination piston either to a non-pressurized reservoir connection or to a storage connection. Also, this brake booster, especially due to the different pistons, built consuming.

It is therefore an object of the present invention to provide a hydraulic brake booster with a pressure medium source and a method for its operation, which is simple in construction and thus inexpensive to produce and requires as little space as possible.

This object is achieved by a hydraulic brake booster according to claim 1 and a method according to claim 14.

The invention is based on the idea that in a hydraulic brake booster with a booster piston, a brake pedal coupled to an actuating piston, an actuator for actuating the master cylinder and a body of elastic material, which is arranged between the actuating piston and the booster piston on the one hand and the actuator on the other in that, when the actuating piston is operated, the booster piston is hydraulically connected to a return port to a pressure medium reservoir, wherein upon actuation of the actuating piston in the brake actuation direction the actuating piston can be applied to the booster piston to separate the booster chamber from the return port. In other words, the hydraulic connection between the booster chamber and the return port is separable upon application of the actuating piston to the booster piston upon movement of the actuating piston toward the booster piston.

The invention has the advantage that the brake booster has a simple and compact structure, and therefore can be produced inexpensively. The brake booster is robust and reliable.

The brake pedal actuated actuating piston acts practically as a brake pedal-operated closing body of a control valve for setting an actuating force proportional pressure in the booster chamber. Additional components, such as In the prior art, a double lever mechanism, a spool valve, poppet valves or a plurality of coaxially arranged pistons are not necessary for controlling the pressure in the booster chamber.

The brake booster according to the invention for motor vehicles requires no negative pressure.

Preferably, in the booster piston, a bore is arranged, via which the booster chamber with unconfirmed actuating piston with the Return connection is connected. Particularly preferred is a limited by the housing and the booster piston annular chamber is provided so that the booster chamber is connected to the return port with unconfirmed actuating piston via the bore in the booster piston and the annular chamber.

Advantageously, the annular chamber is connected to the return port regardless of the operating state of the booster piston, so that when lifting the actuating piston of the booster piston, regardless of the position of the booster piston relative to the housing, pressure medium from the booster chamber can drain into the pressure fluid reservoir.

According to a preferred embodiment of the brake booster according to the invention, the actuating piston is stepped, wherein the step is a sealing edge which is pushed on a movement of the actuating piston in the direction of the booster piston on a ramp-shaped formation of the booster piston, so that the connection between the booster chamber and the return port is disconnected.

Preferably, a sealing element is arranged on the sealing edge of the actuating piston. The sealing element is sealingly pushed upon the movement of the actuating piston in the direction of the booster piston on the ramp-shaped formation of the booster piston, so that the connection between the booster chamber and the return port is disconnected. The sealing element is particularly preferably made elastic, in order to achieve a good sealing effect.

Between the actuating piston and over the body of elastic material, a transmission disc is preferably arranged in order to be able to easily adjust the geometric amplification ratio and the response of the brake booster.

The body of elastic material is preferably a known rubber reaction disc.

The body of elastic material is preferably disposed in a bore of the booster piston to reduce the overall length of the booster. Particularly preferably, the translation disc is arranged in a bore of the booster piston.

Between the actuating piston and booster piston an elastic element is preferably arranged, so that the actuating piston is pushed against the pressure of the prestressed elastic element on the ramp-shaped formation of the booster piston.

According to a preferred embodiment, a portion of the larger diameter actuating piston is slidably and sealingly guided in the housing and a portion of the smaller diameter actuating piston is slidably guided in a bore of the booster piston in sealed fashion. Thus, the booster chamber is sealed even with unactuated actuating piston.

The actuating piston preferably has a constant diameter in the region between the sealing element and the housing-side seal. As a result, act by the construction of a pressure in the booster chamber no forces against the brake actuation direction on the actuating piston.

The booster chamber is preferably connected to the pressure source independently of an actuation state of the actuation piston, wherein a check valve which opens in the direction of the booster chamber is arranged in the connection.

The pressure source is preferably formed by a driven by an electric motor hydraulic pump. Particularly preferably, the suction side is connected to the pressure fluid reservoir, to which the return port is connected.

On the actuating piston or on the booster piston, a driving means is preferably arranged, by means of which during a displacement of the booster piston in the brake actuation direction of the actuating piston is carried.

According to a preferred embodiment, a switching means or detecting means is provided, which detects a movement of the actuating piston. As a result, the pressure source can be activated as needed, only upon actuation of the brake pedal by the driver. Thus, the energy consumption of the brake booster is kept low.

In order to achieve an external control of the brake booster, the return port is preferably via a return line in which an electrically operable, advantageously normally open, valve is arranged, connected to the pressure fluid reservoir.

The invention also relates to a method for operating a hydraulic brake booster according to the invention. In this case, a movement of the actuating piston is detected and the pressure source activated, so that pressure medium in the Booster chamber is promoted as soon as a movement is detected.

Further preferred embodiments of the invention will become apparent from the subclaims and the following description with reference to figures.

Show it

1 A first embodiment of a hydraulic brake booster according to the invention,

2 the brake booster according to 1 in an actuated state, and

3 A second embodiment of a hydraulic brake booster according to the invention.

In 1 is a first embodiment of a hydraulic brake booster according to the invention for actuating a master cylinder 9 of a hydraulic brake system for motor vehicles. 1 shows the brake booster 35 in an unactuated position (brake release position).

To the master cylinder 9 , which is designed, for example, as a tandem master cylinder of conventional design, not shown hydraulic wheel brakes are connected. Master Cylinder 9 is shown only schematically, with only the first working piston (the primary piston) 12 of the master cylinder 9 is shown. Master Cylinder 9 is a pressure medium reservoir 10 assigned, from which pressure medium in the pressure chambers of the master cylinder 9 can run after.

Preferably, the brake booster is used in brake systems with conventional hydraulic wheel brakes.

To realize a parking brake function, the wheel brakes can be embodied on at least one vehicle axle as a combination saddle with an electric parking brake function, in particular with integrated electromechanical actuators.

The housing 5 of the brake booster 35 and the master cylinder 9 are arranged coaxially.

Brake booster 35 is by means of a brake pedal 4 actuated. For this purpose, an actuating piston 1 of the brake booster 35 via a only schematically indicated pedal piston rod (push rod) 22 with the brake pedal 4 coupled.

In the case 5 becomes a booster piston 2 slidably guided, with the housing 5 an amplifier chamber 13 limited. The actuating piston 1 is stepped (level 19 ). A brake pedal side portion of the actuating piston 1 with a larger diameter is displaced and by means of a sealing element 24 sealed in the housing 5 guided. In amplifier piston 2 a bore is made, wherein a master cylinder side portion of the actuating piston 1 with a smaller diameter by means of a sealing element 23 sealed in the bore of the intensifier piston 2 is guided displaceably.

With unactuated (ie unshifted) actuating piston 1 is through the housing 5 , the amplifier piston 2 and the actuating piston 1 a hydraulic room 30 limited. During a movement of the actuating piston 1 towards the intensifier piston 2 becomes the stage 19 on a ramp-shaped formation 34 of the booster piston 2 pushed, causing the room 30 into the amplifier chamber 13 and the room area 33 is shared. The stage 19 of the actuating piston 1 thus represents a sealing edge. For improved seal is at the stage 19 of the actuating piston 1 Therefore, an advantageously elastic, sealing element 6 arranged.

The amplifier chamber 13 is (regardless of the operating state of the actuating piston 1 ) via a pressure connection 26 with an electrically controllable pressure medium source 11 connected, by means of which pressure medium in the booster chamber 13 can be promoted.

Pressure medium source 11 is by way of example by means of an electric motor 32 directly driven hydraulic pump 31 educated. For this purpose, a small, simple electric motor is sufficient. The suction side of the pump 31 is with a pressure medium reservoir 16 connected. In the pressure fluid reservoir 16 the pressure medium source 11 it may be an additional pressure fluid reservoir or the pressure medium reservoir associated with the master cylinder 10 (or a chamber of the same) act. For a cost-effective design of the pressure medium source 11 a DC brush motor is provided. For improved comfort, a speed-controllable brushless DC motor can advantageously be used.

Preferably, the brake booster is designed with an electrically driven hydraulic pump. The structural design of the pump-amplifier unit allows extremely quiet function. Preferably, the pressure medium source comprises 11 only by the electric motor 32 powered hydraulic pump 31 , a high-pressure accumulator or the like for storing hydraulic energy is not available.

Particularly advantageous is the use of pumps with low pulsations, such as gear, Innenzahnrad-, or vane pumps.

In the hydraulic connection line between the pressure medium source 11 and the pressure port 26 is one in the direction of the amplifier chamber 13 opening check valve 17 arranged. In order to minimize throttling during suction, advantageously only the check valve, and no further valve is arranged in the connecting line.

The room area 33 is independent of the operating state of the booster piston 2 with a return connection 25 connected, which via a return line 15 with the pressure medium reservoir 16 connected is. This is a radial bore 27 in intensifier piston 2 arranged which the room area 33 with an annular chamber 28 connects to the housing 5 and the intensifier piston 2 is limited. annular chamber 28 is made by two sealing elements 36 sealed. With a displacement of the booster piston 2 the annular chamber moves 28 over the area of the return connection 25 so that the annular chamber 28 always with the return line 15 connected is.

The amplifier chamber 13 is thus at unoperated actuating piston 1 over the hole 27 and the annular chamber 28 hydraulically with the return connection 25 connected. During a movement of the actuating piston 1 towards the intensifier piston 2 (Brake operation direction) sets the sealing edge 19 of the actuating piston 1 after overcoming a predetermined distance to the ramp-shaped formation 34 of the booster piston 2 on, allowing the hydraulic connection between the booster chamber 13 and the return port 25 is disconnected. With the help of the pressure medium source 11 can then be a pressure in the booster chamber 13 be constructed, through which the booster piston 2 in the direction of the master cylinder (brake operation direction) is shifted.

The ramp-shaped formation 34 the booster piston 2 and the sealing edge 19 of the actuating piston 1 forms, so to speak, a seat valve, wherein the ramp-shaped formation 34 to the valve seat and the actuating piston 1 with sealing edge 19 corresponds to the closing body.

For controlling the pressure medium source 11 is a switching device (eg brake light switch) or detection means (eg position sensor) 14 provided, which is a movement of the actuating piston 1 detected.

Inside the intensifier piston 2 is a known reaction disk 3 made of elastic material, eg rubber, attached. It is located in a bore of the booster piston 2 , which has a larger diameter than the bore for the guidance of the actuating piston 1 has. The rubber reaction disc 3 is held by the inner wall of the booster piston 2 , by the brake pedal end of an actuator 18 in the form of a push rod and through the heel 29 in the intensifier piston 2 , Between the master cylinder side end of the actuating piston 1 and the rubber reaction disc 3 is a translation disc 20 arranged. The rubber reaction disc is thus between the actuating piston 1 and the intensifier piston 2 on the one hand and the actuating element 18 arranged on the other hand.

With the diameter and thickness of the translating disc 20 the geometric gain ratio of the booster is adjusted and the vote of the control path actuating piston to booster piston on the elastic reaction disc 3 performed. So all other parts can be used standardized and unchanged for different vehicles and brake designs. In addition, about the design of the end face of the translation disc 20 the response of the amplifier tunable.

By one of the actuating piston 1 and / or the intensifier piston 2 on the rubber reaction disc 3 applied force passes through the actuator 18 to an actuation of the primary piston 12 of the master cylinder 9 , so that in the pressure chambers of the master cylinder 9 Pressure is built up.

To reset the booster piston 2 in its unoperated basic position is an elastic element 8th provided in the form of a return spring, which is biased between the booster piston 2 and the housing 5 or the master cylinder 9 is arranged.

In the bore of the intensifier piston 2 is in the room area 33 an elastic element 7 arranged in the form of a return spring, which is biased between the booster piston 2 and the actuating piston 1 is arranged and the provision of the actuating piston 1 in its unoperated home position, when the brake pedal operation is terminated.

According to the example is on the actuating piston 1 a means of transport 21 arranged, by means of which during a displacement of the booster piston 2 in the brake actuation direction of the actuating piston 1 is carried.

The amplifier piston 2 is therefore substantially tubular, wherein the interior at least a portion of the actuating piston 1 with a smaller diameter, the body 3 made of elastic material and the booster piston end of the actuating element 18 receives.

Based on 2 that the brake booster 35 according to 1 shows in an actuated state, the operation of a brake booster according to the invention will be explained in more detail. For a better overview because of the master cylinder 9 as well as the coupling to the brake pedal 4 in 2 not shown.

When the brake pedal is pressed 4 by the driver becomes a force F _driver on the actuating piston 1 exercised, which thereby in the direction of the booster piston 2 (in brake actuation direction, left in 2 ) is moved. By suitable means, such as a switch or a displacement sensor 14 that the movement of the actuating piston 1 Captured, it is achieved that the pump 31 only when the brake pedal is pressed 4 starts. In a particularly preferred embodiment of the brake booster according to the invention, the detection of the driver's braking request is effected by a redundant and independently secured measurement of the brake pedal or actuating piston travel. When a brake pedal movement is detected, the pump becomes 31 switched on. The pump 31 then promotes pressure fluid volume in the booster chamber 13 , As long as the actuating piston 1 not yet on the amplifier piston 2 seated and the hydraulic connection between the booster chamber 13 and return port 25 separates, finds no pressure build-up in the booster chamber 13 Instead, since the pressure medium is conveyed so to speak in a circle (from the pressure medium reservoir 16 into the amplifier chamber 13 , from the amplifier chamber 13 the pressure medium flows over the space area 33 , the hole 27 , the ring chamber 28 , the return line 15 back into the pressure fluid reservoir 16 ).

Closes the actuating piston 1 over the sealing edge 19 the connection to the return connection 25 off, so will a pressure in the booster chamber 13 built, the amplifier piston 2 in brake actuation direction (to the left in 2 ) (according to an amplification force F _Verst ).

The pressure in the booster chamber 13 is set so to speak by the driver by means of a brake pedal operated control valve foot force proportional. The streamlined design of the brake pedal-operated control valve ensures particularly quiet operation of the amplifier. The stepless actuating force-proportional pressure setting and the usual brake pedal feel are achieved with the already known by vacuum brake booster reaction mechanism of a rubber reaction disc.

About the rubber reaction disc 3 be the driver F _driver and the boosting force F _Verst on the actuator 18 transmitted and there is an actuating force F _Bet for actuating the master cylinder 9 generated. Marriage through the actuator 18 and the working piston 12 of the master cylinder 9 a master cylinder pressure is built up, the rubber reaction disc 3 through the actuating piston 1 (or the translation disc 20 ) and the intensifier piston 2 compressed by a certain amount.

The control _balance between driver F _driver and boost force F _Verst on the known rubber reaction disc 3 Ensures the intended amplifier characteristic without force or pressure sensors.

A reaction force on the brake pedal-connected actuating piston 1 acts exclusively by the response spring 7 and the force-dependent deformation of the rubber reaction disc 3 generated. The actuating piston 1 owns in the area between the sealing edge 19 and the housing-side seal 24 (ie in the area of the amplifier chamber 13 ) of the same diameter, allowing pressure build-up in the booster chamber 13 no force against the brake actuation direction on the actuating piston 1 generated.

Actuation of the driver's brake pedal 4 not further, so he holds the actuating piston 1 in one position, it causes the intensifier piston 2 the hydraulic connection at the sealing edge 19 opens and pressure fluid volume in the pressure fluid reservoir 16 can flow out, so that the pressure in the booster chamber 13 reduced. This relative movement between actuating piston 1 and intensifier pistons 2 becomes forceful at the rubber reaction disc 3 corrected.

This in 3 illustrated second embodiment of a hydraulic brake booster according to the invention largely corresponds to the first embodiment. In addition, in the return line 15 an electrically operable, advantageously normally open, valve 40 arranged. This allows a third-party control of the brake booster, ie by the addition of only one valve 40 is a third-party control of the brake control possible. By closing the valve 40 Can the hydraulic connection between the booster chamber 13 and the pressure fluid reservoir 16 even with unactuated actuating piston 1 be separated, allowing a pressure build-up in the booster chamber 13 and with it Moving the booster piston 2 in the brake actuation direction is possible.

Valve 40 is advantageously designed as a proportional valve to adjust an accurate pressure can.

The supplement to the external control further requires the acquisition of additional physical variables, their evaluation and the demand-controlled control of the pressure medium source 11 , For this purpose, a person skilled in the known and not particularly illustrated electronic control unit (ECU) is required. The necessary sensors and the connections are also known to the person skilled in the art and are therefore only partially here (eg position detection sensor 14 ' for redundant and independently secured measurement of the brake pedal or actuating piston travel).

In summary, it can be said that the invention provides an energy-efficient hydraulic brake booster with very simple means. The low energy requirement is due to the fact that energy is consumed only when needed and only to the extent currently required.

The invention offers the advantage of a vacuum-free "on-demand" brake booster.

An advantage of the brake booster according to the invention is the particularly simple removal. Furthermore, the brake booster according to the invention has a high availability.

The brake booster according to the invention has in particular a simple control valve principle. According to the first embodiment, no electrically switchable valves are required.

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 3726525 A1 [0002]
• DE 10017341 A1 [0003]

Claims (14)

Hydraulic brake booster ( 35 ) for actuating a working piston ( 12 ) of a master cylinder ( 9 ) of a hydraulic brake system for motor vehicles, comprising a housing ( 5 ), in which a booster piston ( 2 ) is slidably guided, wherein the booster piston ( 2 ) with the housing ( 5 ) an amplifier chamber ( 13 ), an electrically controllable pressure medium source ( 11 ) connected to the booster chamber ( 13 ), wherein a build-up of a pressure in the booster chamber ( 13 ) by means of the pressure medium source ( 11 ) of the booster piston ( 2 ) is displaceable in a brake actuation direction, one with a brake pedal ( 4 ) coupled actuating piston ( 1 ), an actuator ( 18 ) for actuating the working piston ( 12 ), and a body ( 3 ) made of elastic material, in particular a rubber reaction disc, which between the actuating piston ( 1 ) and the intensifier piston ( 2 ) on the one hand and the actuating element ( 18 ) is arranged on the other hand, characterized in that the booster chamber ( 13 ) with unactuated actuating piston ( 1 ) with a return connection ( 25 ) to a pressure medium reservoir ( 16 ) is hydraulically connected, wherein upon actuation of the actuating piston in the brake actuation direction of the actuating piston ( 1 ) on the booster piston ( 2 ) can be applied to the amplifier chamber ( 13 ) to be separated from the return port. Brake booster according to claim 1, characterized in that the booster chamber ( 13 ) with unactuated actuating piston ( 1 ) via a bore ( 27 ) in the booster piston ( 2 ), and in particular one of the housing ( 5 ) and the intensifier piston ( 2 ) limited annular chamber ( 28 ), with the return port ( 25 ) connected is. Brake booster according to claim 1 or 2, characterized in that the actuating piston ( 1 ) is stepped, the level ( 19 ) represents a sealing edge, which during a movement of the actuating piston ( 1 ) in the direction of the intensifier piston ( 2 ) on a ramp-shaped formation ( 34 ) of the booster piston ( 2 ), so that the connection between the amplifier chamber ( 13 ) and the return port ( 25 ) is separated. Brake booster according to claim 3, characterized in that at the sealing edge of the actuating piston a, in particular elastic, sealing element ( 6 ) is arranged. Brake booster according to claim 3 or 4, characterized in that between the actuating piston ( 1 ) and over the body ( 3 ) of elastic material, a translation disc ( 20 ) is arranged. Brake booster according to one of claims 3 to 5, characterized in that the actuating piston ( 1 ) against the pressure of a prestressed elastic element, in particular a spring ( 7 ), on the ramp-shaped formation of the booster piston ( 2 ) is pushed. Brake booster according to one of claims 3 to 6, characterized in that a portion of the actuating piston with a larger diameter displaceable and sealed ( 24 ) in the housing ( 5 ) and / or that a portion of the actuating piston is sealed with a smaller diameter ( 23 ) in a bore of the intensifier piston ( 2 ) is guided displaceably. Brake booster according to claim 7, characterized in that the actuating piston ( 1 ) in the area between the sealing element ( 6 ) and the housing-side seal ( 24 ) has a constant diameter. Brake booster according to one of claims 1 to 8, characterized in that the booster chamber ( 13 ) regardless of an operating state of the actuating piston ( 1 ) with the pressure medium source ( 11 ), wherein in the connection, in particular exclusively, a non-return valve opening in the direction of the booster chamber (US Pat. 17 ) is arranged. Brake booster according to one of claims 1 to 9, characterized in that the pressure medium source ( 11 ) by means of an electric motor ( 32 ) driven hydraulic pump ( 31 ) is formed, the suction side in particular with the pressure fluid reservoir ( 16 ) connected is. Brake booster according to one of claims 1 to 10, characterized in that on the actuating piston ( 1 ) or on the booster piston ( 2 ) an entrainment means ( 21 ) is arranged, by means of which during a displacement of the booster piston ( 2 ) in the brake actuating direction of the actuating piston ( 1 ) is carried. Brake booster according to one of claims 1 to 11, characterized in that a switching means or a detection means ( 14 . 14 ' ) is provided, which movement of the actuating piston ( 1 ) detected. Brake booster according to one of claims 1 to 12, characterized in that the return port ( 25 ) via a return line ( 15 ), in which an electrically operable, in particular normally open valve ( 40 ) is arranged, with the pressure fluid reservoir ( 16 ) connected is. Method for operating a hydraulic brake booster according to one of claims 1 to 13, characterized in that a movement of the actuating piston ( 1 ) and that the pressure medium source ( 11 ) is activated, so that pressure medium in the booster chamber ( 13 ) is promoted as soon as a movement is detected.

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